CN104979846B - A kind of multi-electrical level inverter low voltage traversing control method, equipment and system - Google Patents
A kind of multi-electrical level inverter low voltage traversing control method, equipment and system Download PDFInfo
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Abstract
The present invention provides a kind of multi-electrical level inverter low voltage traversing control method, equipment and system, in inverter applied to photovoltaic electric station grid connection operation, for the DC supply input that the solar energy pole plate of photovoltaic plant exports to inverter, DC inverter is that alternating current is fed back to power grid after alternating current by inverter；Including：The three-phase voltage of power grid is monitored, judges whether network voltage occurs asymmetry and fall；Asymmetry is fallen including two-phase short-circuit fault and single-phase grounding fault；If network voltage occurs asymmetry and falls, power frequency common-mode voltage is injected into the given three-phase grid voltage for input to PWM modulator, PWM controller is according to given three-phase grid voltage output pwm signal to control the on off state of switching tube in inverter.The power frequency fluctuation of busbar midpoint electric current is reduced or reduces by controlling the work of inverter.After the power frequency fluctuation of busbar midpoint electric current is reduced, the voltage stress that each switching tube is born can reduce, and switching tube will not be caused to damage.
Description
Technical field
The present invention relates to power electronics field, more particularly to a kind of multi-electrical level inverter low voltage crossing controlling party
Method, equipment and system.
Background technology
With petering out for the energy, solar energy is increasingly utilized now and is generated electricity.But solar energy pole plate is defeated
Go out for direct current, it is necessary to feed back to power grid or load after inverter inversion is alternating current.Therefore, inverter is in the sun
Key effect can be played in photovoltaic generating system.
In recent years, as an important indicator for ensureing operation of power networks, the low-voltage of inverter in photovoltaic generating system
Pass through（LVRT, Low Voltage Ride Through）Ability is increasingly taken seriously.
LVRT refers to when power system accident or disturbance cause the Voltage Drop of photovoltaic electric station grid connection point, in certain voltage
Fall in scope and time interval, photovoltaic plant can ensure that off-grid is not run continuously, avoid the extension of electric network fault, at the same time
Photovoltaic combining inverter is required to send certain active power and reactive power, to support power system restoration, so that " passing through "
This low-voltage time (region).
LVRT points are symmetrically to fall（Three phase short circuit fault）Fall with asymmetry（Two-phase short-circuit fault, single-line to ground fault
Failure）.
LVRT technologies in the prior art are described below.
Referring to Fig. 1, which is the grid-connected inverters control block diagram for having the function of in the prior art LVRT.
In grid-connected inverters control, power grid three-phase voltage is gathered first（ea、eb、ec）And three-phase current（ia、ib、ic）；
The component i under dq reference axis is obtained by coordinate transformdAnd iq；Electric network voltage phase angle γ is obtained by phase-angle detection.
Wherein LVRT includes 200 two parts of LVRT detection modules 100 and LVRT control modules.LVRT detection modules 100 are real
Now to the real-time detection of grid voltage amplitude and phase, testing result is returned to LVRT control modules 200, LVRT control modules
200 realize the control of watt current and reactive current during LVRT.
Although the control block diagram shown in Fig. 1 can control inverter to complete low voltage crossing, in low voltage crossing mistake
Cheng Zhong, there are larger fluctuation for busbar midpoint electric current.
Therefore, those skilled in the art need to provide a kind of control method of multi-electrical level inverter low voltage crossing and set
It is standby, low voltage crossing can be smoothly completed, and reduce the ripple of busbar midpoint electric current when network voltage generation asymmetry is fallen
It is dynamic.
The content of the invention
The embodiment of the present invention provides a kind of multi-electrical level inverter low voltage traversing control method, equipment and system, Neng Gou
Network voltage occurs to favorably accomplish low voltage crossing when asymmetry is fallen, and reduces the fluctuation of busbar midpoint electric current.
First aspect, there is provided a kind of multi-electrical level inverter low voltage traversing control method, is transported applied to photovoltaic electric station grid connection
In capable inverter, the DC supply input exported of the solar energy pole plate of photovoltaic plant is inverse by direct current to inverter, inverter
It is changed into that alternating current is fed back to power grid after alternating current；Comprise the following steps：
The three-phase voltage of power grid is monitored, judges whether network voltage occurs asymmetry and fall；The asymmetry fall including
Two-phase short-circuit fault and single-phase grounding fault；
Fall if asymmetry occurs for network voltage, noted into the given three-phase grid voltage for inputing to PWM modulator
Enter power frequency common-mode voltage, the PWM controller is according to the given three-phase grid voltage output pwm signal to control in inverter
The on off state of switching tube.
It is described to inputing to the given three-phase of PWM controller simultaneously in the first possible implementation of first aspect
Inject before power frequency common-mode voltage, further include in net voltage：
Detect the three-phase reactive current and three-phase in the amplitude and phase of power grid three-phase voltage, and asymmetric falling process
Watt current；
Institute is determined according to the amplitude of the power grid three-phase voltage and phase and three-phase reactive current and three-phase watt current
State the amplitude and phase of power frequency common-mode voltage.
With reference to first aspect and in any of the above-described kind of possible implementation, in second of possible implementation, institute
State and injected into the given three-phase grid voltage for input to PWM modulator before power frequency common-mode voltage, further included：
Detect positive pole line voltage and negative busbar voltage；
Positive and negative busbar voltage difference is obtained by the positive pole line voltage and negative busbar voltage；
By the positive and negative busbar voltage difference compared with reference voltage, the power frequency common-mode voltage is determined by comparative result
Amplitude and phase.
Second aspect, there is provided a kind of multi-electrical level inverter low voltage crossing control device, is transported applied to photovoltaic electric station grid connection
In capable inverter, the DC supply input exported of the solar energy pole plate of photovoltaic plant is inverse by direct current to inverter, inverter
It is changed into that alternating current is fed back to power grid after alternating current；Including：Judging unit and injection unit；
The judging unit, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall；Institute
Asymmetry is stated to fall including two-phase short-circuit fault and single-phase grounding fault；
The injection unit, for when judging unit judges that network voltage occurs asymmetry and falls, to inputing to PWM tune
Power frequency common-mode voltage is injected in the given three-phase grid voltage of device processed, the PWM controller is according to the given three-phase grid electricity
Output pwm signal is pressed to control the on off state of switching tube in inverter.
In the first possible implementation of second aspect, further include：First detection unit and the first determination unit；
The first detection unit, for detecting the amplitude and phase of power grid three-phase voltage, and asymmetric falling process
In three-phase reactive current and three-phase watt current；
First determination unit, for the amplitude according to the power grid three-phase voltage and phase and three-phase reactive current
The amplitude and phase of the power frequency common-mode voltage are determined with three-phase watt current.
With reference in second aspect and any of the above-described kind of possible implementation, in second of possible implementation, go back
Including：Second detection unit, positive and negative busbar voltage difference obtaining unit and the second determination unit；
The second detection unit, for detecting positive pole line voltage and negative busbar voltage；
The positive and negative busbar voltage difference obtaining unit, for obtaining positive and negative mother by the positive pole line voltage and negative busbar voltage
Line voltage is poor；
Second determination unit, for the positive and negative busbar voltage difference compared with reference voltage, to be tied by comparing
Fruit determines the amplitude and phase of the power frequency common-mode voltage.
The third aspect, there is provided a kind of multi-electrical level inverter low voltage ride through control system, including：Inverter, PWM modulator
And controller；
The inverter, the DC inverter for solar energy pole plate to be exported feed back to power grid for alternating current；
The PWM modulator, for output pwm signal under the control of the controller to the switching tube in inverter, control
The on off state of switching tube；
The controller, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall, described
Asymmetry is fallen including two-phase short-circuit fault and single-phase grounding fault；Fall if it is determined that asymmetry occurs for network voltage,
Power frequency common-mode voltage is then injected into the given three-phase grid voltage for input to PWM modulator.
In the first possible implementation of the third aspect, the controller, is additionally operable to detection power grid three-phase voltage
Amplitude and phase, and three-phase reactive current and three-phase watt current in asymmetric falling process；According to the power grid three
The amplitude and phase and three-phase reactive current and three-phase watt current of phase voltage determine the power frequency common-mode voltage amplitude and
Phase.
With reference in the third aspect and any of the above-described kind of possible implementation, in second of possible implementation, institute
Controller is stated, is additionally operable to detection positive pole line voltage and negative busbar voltage；Obtained just by the positive pole line voltage and negative busbar voltage
Negative busbar voltage difference；By the positive and negative busbar voltage difference compared with reference voltage, determine that the power frequency is total to by comparative result
The amplitude and phase of mode voltage.
With reference in the third aspect and any of the above-described kind of possible implementation, in the third possible implementation, institute
It is three-phase multi-electrical level inverter to state inverter；
The inverter is at least two parallel runnings.
Multi-electrical level inverter low voltage traversing control method, equipment and the system that above technical scheme provides, are judging electricity
When net voltage generation asymmetry falls failure, power frequency common-mode voltage is injected into given three-phase grid voltage.Because power grid is electric
When pressure life asymmetry falls failure, busbar midpoint electric current can produce power frequency fluctuation, in order to reduce the power frequency of busbar midpoint electric current
Fluctuation, therefore, just injects power frequency common-mode voltage, the pwm signal of such PWM modulator output is exactly to note before PWM modulator
Enter the later signal of power frequency common-mode voltage, since pwm signal is used for controlling the on off state of switching tube in inverter, pass through
Control inverter works to reduce or reduce the power frequency fluctuation of busbar midpoint electric current.When the power frequency fluctuation quilt of busbar midpoint electric current
After reduction, the voltage stress that each switching tube is born in inverter can reduce, and will not so cause switching tube to damage.
Brief description of the drawings
In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing
There is attached drawing needed in technology description to be briefly described, it should be apparent that, drawings in the following description are only this
Some embodiments of invention, for those of ordinary skill in the art, without creative efforts, can be with
Other attached drawings are obtained according to these attached drawings.
Fig. 1 is the grid-connected inverters control block diagram for having the function of in the prior art LVRT；
Fig. 2 is one flow chart of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention；
Fig. 3 is inverter busbar mid-point voltage wave pattern of the network voltage by taking B phase ground short circuit failures as an example；
Fig. 4 is control block diagram when asymmetric fall occurs for network voltage provided by the invention；
Fig. 5 is two flow chart of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention；
Fig. 6 is three flow chart of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention；
Fig. 7 be it is provided by the invention injection power frequency common-mode voltage after B relative ground circuits when oscillogram；
Fig. 8 is one schematic diagram of multi-electrical level inverter low voltage crossing control device embodiment provided by the invention；
Fig. 9 is two schematic diagram of multi-electrical level inverter low voltage crossing control device embodiment provided by the invention；
Figure 10 is three schematic diagram of multi-electrical level inverter low voltage crossing control device embodiment provided by the invention；
Figure 11 is one schematic diagram of multi-electrical level inverter low voltage ride through control system embodiment provided by the invention.
Embodiment
Below in conjunction with the attached drawing in the embodiment of the present invention, the technical solution in the embodiment of the present invention is carried out clear, complete
Site preparation describes, it is clear that described embodiment is only part of the embodiment of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, those of ordinary skill in the art are obtained every other without making creative work
Embodiment, belongs to the scope of protection of the invention.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, below in conjunction with the accompanying drawings to the present invention
Embodiment be described in detail.
It should be noted that the embodiment of the present invention provides a kind of multi-electrical level inverter low voltage traversing control method, equipment
And system, when asymmetry, which occurs, for network voltage falls, subtracted by injecting power frequency common-mode voltage into given three-phase voltage
The fluctuation of small busbar midpoint electric current, and then protect the switching tube in inverter.
Embodiment of the method one：
Referring to Fig. 2, which is one flow of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention
Figure.
Multi-electrical level inverter low voltage traversing control method provided in this embodiment, applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Including：
S201：The three-phase voltage of power grid is monitored, judges whether network voltage occurs asymmetry and fall；The asymmetry is fallen
Including two-phase short-circuit fault and single-phase grounding fault；
It should be noted that method provided in an embodiment of the present invention solar photovoltaic generation system suitable for sending not
When symmetrically falling failure.
Asymmetry, which falls failure, to be included：Two-phase short-circuit fault, single-phase grounding fault.For example, B phases ground short circuit event
Barrier, or, short trouble between A phases and B phases.
It is understood that this method is not suitable for symmetrically falling failure, i.e., short circuit occurs for A phases, B phases and C phase three-phases
Failure.
For example, for three-level inverter, bus capacitor midpoint electric current is by three-phase grid electric current and three-phase PWM switch function
Determine.When asymmetry, which occurs, for network voltage falls failure, bus capacitor midpoint electric current causes Down Highway there are larger fluctuation
The fluctuation of voltage, specifically may refer to Fig. 3, which is in inverter busbar of the network voltage by taking B phase ground short circuit failures as an example
Point voltage wave cardon.
From figure 3, it can be seen that when ground short circuit failure occurs for B phases, it will in busbar midpoint electric current（It is corresponding in Fig. 3
Inverter midpoint electric current）Upper generation power frequency fluctuation（The power frequency of China is 50Hz）；So as to cause inverter busbar mid-point voltage
Power frequency fluctuation.And by emulation and verification experimental verification, when asymmetry, which occurs, for network voltage falls, there are work for busbar mid-point voltage
Frequency fluctuates, and the voltage stress that when the fluctuation of busbar mid-point voltage is larger the switching tube in inverter can be caused to bear is excessive or implements
Protection causes LVRT to fail, and can increase system cost if the capacity of increase bus capacitor in turn.
The present invention is taken when network voltage generation asymmetry is fallen, and power frequency common-mode voltage is injected, to reduce busbar midpoint
The fluctuation of electric current.Since the fluctuation of busbar midpoint electric current can produce the fluctuation of busbar mid-point voltage, reduce busbar midpoint electricity
The fluctuation of stream and then the fluctuation that busbar mid-point voltage can be reduced.
S202：Fall if asymmetry occurs for network voltage, to the given three-phase grid voltage for inputing to PWM modulator
Middle injection power frequency common-mode voltage, the PWM controller is according to the given three-phase grid voltage output pwm signal to control inversion
The on off state of switching tube in device.
It is understood that the purpose of injection power frequency common-mode voltage is to offset the fluctuation of busbar midpoint electric current.
Fig. 4 specifically is may refer to, which is control block diagram when asymmetric fall occurs for network voltage provided by the invention.
When judging that generation asymmetry is fallen, it is necessary to before PWM modulator, injected into given three-phase grid voltage
Power frequency common-mode voltage.As shown in figure 4, given three-phase grid voltage is ua *、ub *And uc *；It should be noted that the power frequency of injection
Common-mode voltage is a vector, including power frequency common-mode voltage amplitude and phase.The amplitude and phase of the power frequency common-mode voltage of injection
It is to be determined by the drop depth of network voltage.
In solar photovoltaic generation system shown in Fig. 4, including two inverters, the two inverter parallels.
It is understood that in solar photovoltaic generation system, it can only include an inverter, can also include more
The inverter of a parallel running.
Control of the method provided in this embodiment for each inverter is identical, and identical work is injected in each inverter
Frequency common-mode voltage.
To sum up, multi-electrical level inverter low voltage traversing control method provided in this embodiment, is judging network voltage
When asymmetry falls failure, power frequency common-mode voltage is injected into given three-phase grid voltage.Because it is not right that network voltage occurs
When title falls failure, busbar midpoint electric current can produce power frequency fluctuation, in order to reduce the power frequency fluctuation of busbar midpoint electric current, therefore,
Power frequency common-mode voltage is just injected before PWM modulator, the pwm signal of such PWM modulator output is exactly to inject power frequency common mode
The later signal of voltage, since pwm signal is used for controlling the on off state of switching tube in inverter, by controlling inverter
Work reduce or reduce the power frequency fluctuation of busbar midpoint electric current.After the power frequency fluctuation of busbar midpoint electric current is reduced,
The voltage stress that each switching tube is born in inverter can reduce, and will not so cause switching tube to damage.
The present invention provides the control mode of two kinds of power frequency common-mode voltages, one kind is opened loop control, and another kind is closed loop control
System, is discussed in detail with reference to specific embodiment.
Embodiment of the method two：
Referring to Fig. 5, which is two flow of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention
Figure.
The method that multi-electrical level inverter low voltage crossing is realized with opened loop control is introduced in the present embodiment.
S501 is identical with S201, and details are not described herein.
S502：Detect the three-phase reactive current in the amplitude and phase of power grid three-phase voltage, and asymmetric falling process
With three-phase watt current；
During operation of power networks, the three-phase voltage and three-phase current information of power grid can be gathered, therefore, passes through three-phase
Voltage falls it may determine that asymmetry whether occurs.In addition, it can determine to need what is injected by the information of voltage and current
The amplitude and phase of power frequency common-mode voltage.
S503：It is true according to the amplitude of the power grid three-phase voltage and phase and three-phase reactive current and three-phase watt current
The amplitude and phase of the fixed power frequency common-mode voltage.
S504：Power frequency common-mode voltage, the PWM are then injected into the given three-phase grid voltage for input to PWM modulator
Controller is according to the given three-phase grid voltage output pwm signal to control the on off state of switching tube in inverter.
It should be noted that method provided in this embodiment, the position of injection power frequency common-mode voltage is PWM modulation in Fig. 4
Before device, power frequency common-mode voltage is injected into given three-phase voltage.
Method provided in this embodiment, it is not necessary to by the voltage of detection or current feedback to input terminal and set-point or in advance
Definite value is compared, but the power frequency common-mode voltage of injection is directly determined according to the voltage and current of detection, belongs to open loop control
System, this control is fairly simple, and it is convenient to realize.By injecting power frequency common-mode voltage, the power frequency of busbar midpoint electric current can be reduced
Fluctuation, so as to reduce the voltage stress that each switching tube is born in inverter, protection switch pipe is without prejudice.
Embodiment of the method three：
Referring to Fig. 6, which is three flow of multi-electrical level inverter low voltage traversing control method embodiment provided by the invention
Figure.
The method for realizing multi-electrical level inverter low voltage crossing in the present embodiment with closed-loop control.
S601 is identical with S201, and details are not described herein.
S602：Detect positive pole line voltage and negative busbar voltage；
S603：Positive and negative busbar voltage difference is obtained by the positive pole line voltage and negative busbar voltage；
Since the difference of positive pole line voltage and negative busbar voltage can represent the fluctuation situation of busbar midpoint electric current, use
Positive and negative busbar voltage difference is used as feedback quantity, which is judged to the ripple of busbar midpoint electric current compared with reference voltage
It is dynamic.
It is understood that the reference voltage is voltage set in advance, calculate for convenience, in the embodiment of the present invention
Reference voltage can be set as zero.
S604：By the positive and negative busbar voltage difference compared with reference voltage, determine that the power frequency is total to by comparative result
The amplitude and phase of mode voltage.
S605：Power frequency common-mode voltage, the PWM are then injected into the given three-phase grid voltage for input to PWM modulator
Controller is according to the given three-phase grid voltage output pwm signal to control the on off state of switching tube in inverter.
It should be noted that the position that power frequency common-mode voltage is injected in the present embodiment is also in Fig. 4 before PWM modulator,
Power frequency common-mode voltage is injected into given three-phase voltage.
In the present embodiment, using closed-loop control, positive and negative mother is obtained by the positive pole line voltage and negative busbar voltage of collection
Line voltage is poor, and positive and negative busbar voltage difference is fed back to input terminal compared with reference voltage, injection is determined by comparative result
Power frequency common-mode voltage amplitude and phase.The closed-loop control that the present embodiment uses, can pass through the positive and negative busbar voltage of feedback
Reference voltage poor and set in advance is compared, and control can so be better achieved.
In order to which the beneficial effect for the method that above example of the present invention provides is better described, below in conjunction with the accompanying drawings for
It is bright.
Referring to Fig. 7, the figure be it is provided by the invention injection power frequency common-mode voltage after B relative ground circuits when oscillogram.
Fig. 7 is compared with Fig. 3 and can be seen that by opened loop control provided in an embodiment of the present invention or closed-loop control, to
Injected in given three-phase voltage after power frequency common-mode voltage, effectively reduce busbar mid-point voltage and electric current when asymmetry is fallen
Fluctuation.
From figure 3, it can be seen that inverter midpoint electric current（Busbar midpoint electric current）Perunit value be about 1, and in Fig. 7
In, inverter midpoint electric current（Busbar midpoint electric current）Perunit value be about 0.5.
Apparatus embodiments one：
The multi-electrical level inverter low voltage traversing control method provided based on above example, present invention also offers one kind
Multi-electrical level inverter low voltage crossing control device, is discussed in detail below in conjunction with the accompanying drawings.
Referring to Fig. 8, which is that multi-electrical level inverter low voltage crossing control device embodiment one provided by the invention is illustrated
Figure.
Multi-electrical level inverter low voltage crossing control device provided in this embodiment, applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Including：Judging unit 800 and injection unit 900；
The judging unit 800, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall
Fall；The asymmetry is fallen including two-phase short-circuit fault and single-phase grounding fault；
It should be noted that control device provided in an embodiment of the present invention solar photovoltaic generation system suitable for sending out
When sending the asymmetry to fall failure.
Asymmetry, which falls failure, to be included：Two-phase short-circuit fault, single-phase grounding fault.For example, B phases ground short circuit event
Barrier, or, short trouble between A phases and B phases.
It is understood that this method is not suitable for symmetrically falling failure, i.e., short circuit occurs for A phases, B phases and C phase three-phases
Failure.
For example, for three-level inverter, bus capacitor midpoint electric current is by three-phase grid electric current and three-phase PWM switch function
Determine.When asymmetry, which occurs, for network voltage falls failure, bus capacitor midpoint electric current causes Down Highway there are larger fluctuation
The fluctuation of voltage, specifically may refer to Fig. 3, which is in inverter busbar of the network voltage by taking B phase ground short circuit failures as an example
Point voltage wave cardon.
From figure 3, it can be seen that when ground short circuit failure occurs for B phases, it will in busbar midpoint electric current（It is corresponding in Fig. 3
Inverter midpoint electric current）Upper generation power frequency fluctuation（The power frequency of China is 50Hz）；So as to cause inverter busbar mid-point voltage
Power frequency fluctuation.And by emulation and verification experimental verification, when asymmetry, which occurs, for network voltage falls, there are work for busbar mid-point voltage
Frequency fluctuates, and the voltage stress that when the fluctuation of busbar mid-point voltage is larger the switching tube in inverter can be caused to bear is excessive or implements
Protection causes LVRT to fail, and can increase system cost if the capacity of increase bus capacitor in turn.
The present invention is taken when network voltage generation asymmetry is fallen, and power frequency common-mode voltage is injected, to reduce busbar midpoint
The fluctuation of electric current.Since the fluctuation of busbar midpoint electric current can produce the fluctuation of busbar mid-point voltage, reduce busbar midpoint electricity
The fluctuation of stream and then the fluctuation that busbar mid-point voltage can be reduced.
The injection unit 900, for when judging unit judges that network voltage occurs asymmetry and falls, to inputing to
In the given three-phase grid voltage of PWM modulator inject power frequency common-mode voltage, the PWM controller according to the given three-phase simultaneously
Net voltage output pwm signal is to control the on off state of switching tube in inverter.
It should be noted that injection power frequency common-mode voltage is to offset the fluctuation of busbar midpoint electric current.
It is understood that in solar photovoltaic generation system, it can only include an inverter, can also include more
The inverter of a parallel running.
Control of the equipment provided in this embodiment for each inverter is identical, and identical work is injected in each inverter
Frequency common-mode voltage.
To sum up, multi-electrical level inverter low voltage crossing control device provided in this embodiment, is judging network voltage
When asymmetry falls failure, power frequency common-mode voltage is injected into given three-phase grid voltage.Because it is not right that network voltage occurs
When title falls failure, busbar midpoint electric current can produce power frequency fluctuation, in order to reduce the power frequency fluctuation of busbar midpoint electric current, therefore,
Power frequency common-mode voltage is just injected before PWM modulator, the pwm signal of such PWM modulator output is exactly to inject power frequency common mode
The later signal of voltage, since pwm signal is used for controlling the on off state of switching tube in inverter, by controlling inverter
Work reduce or reduce the power frequency fluctuation of busbar midpoint electric current.After the power frequency fluctuation of busbar midpoint electric current is reduced,
The voltage stress that each switching tube is born in inverter can reduce, and will not so cause switching tube to damage.
Apparatus embodiments two：
An embodiment of the present invention provides two kinds of different control devices, a kind of is the control device of open loop control mode, separately
A kind of be the control device of close-loop control mode, introduces separately below, introduces the control device of open loop control mode first.
Referring to Fig. 9, which is that multi-electrical level inverter low voltage crossing control device embodiment two provided by the invention is illustrated
Figure.
Multi-electrical level inverter low voltage crossing control device provided in this embodiment, except including in apparatus embodiments one
Beyond judging unit 800 and injection unit 900, further include：First detection unit 1000a and the first determination unit 1000b；
The first detection unit 1000a, for detecting the amplitude and phase of power grid three-phase voltage, and asymmetry is fallen
During three-phase reactive current and three-phase watt current；
During operation of power networks, the three-phase voltage and three-phase current information of power grid can be gathered, therefore, passes through three-phase
Voltage falls it may determine that asymmetry whether occurs.In addition, it can determine to need what is injected by the information of voltage and current
The amplitude and phase of power frequency common-mode voltage.
The first determination unit 1000b, for the amplitude according to the power grid three-phase voltage and phase and three-phase without
Work(electric current and three-phase watt current determine the amplitude and phase of the power frequency common-mode voltage.
It should be noted that control device provided in this embodiment, the position of injection power frequency common-mode voltage is PWM in Fig. 4
Before modulator, power frequency common-mode voltage is injected into given three-phase voltage.
Control device provided in this embodiment, it is not necessary to by the voltage of detection or current feedback to input terminal and set-point or
Person's predetermined value is compared, but the power frequency common-mode voltage of injection is directly determined according to the voltage and current of detection, is belonged to out
Ring controls, and this control is fairly simple, and it is convenient to realize.By injecting power frequency common-mode voltage, busbar midpoint electric current can be reduced
Power frequency fluctuation, so as to reduce the voltage stress that each switching tube is born in inverter, protection switch pipe is without prejudice.
Apparatus embodiments three：
Referring to Figure 10, which is that multi-electrical level inverter low voltage crossing control device embodiment three provided by the invention is illustrated
Figure.
The control device with close-loop control mode is described below.
Multi-electrical level inverter low voltage crossing control device provided in this embodiment, except including in apparatus embodiments one
Beyond judging unit 800 and injection unit 900, further include：Second detection unit 1000c, positive and negative busbar voltage difference obtaining unit
1000d and the second determination unit 1000e；
The second detection unit 1000c, for detecting positive pole line voltage and negative busbar voltage；
The positive and negative busbar voltage difference obtaining unit 1000d, for by the positive pole line voltage and the acquisition of negative busbar voltage
Positive and negative busbar voltage difference；
Since the difference of positive pole line voltage and negative busbar voltage can represent the fluctuation situation of busbar midpoint electric current, use
Positive and negative busbar voltage difference is used as feedback quantity, which is judged to the ripple of busbar midpoint electric current compared with reference voltage
It is dynamic.
It is understood that the reference voltage is voltage set in advance, calculate for convenience, in the embodiment of the present invention
Reference voltage can be set as zero.
The second determination unit 1000e, for by the positive and negative busbar voltage difference compared with reference voltage, by than
Relatively result determines the amplitude and phase of the power frequency common-mode voltage.
It should be noted that the position that power frequency common-mode voltage is injected in the present embodiment is also in Fig. 4 before PWM modulator,
Power frequency common-mode voltage is injected into given three-phase voltage.
In the present embodiment, using closed-loop control, positive and negative mother is obtained by the positive pole line voltage and negative busbar voltage of collection
Line voltage is poor, and positive and negative busbar voltage difference is fed back to input terminal compared with reference voltage, injection is determined by comparative result
Power frequency common-mode voltage amplitude and phase.The closed-loop control that the present embodiment uses, can pass through the positive and negative busbar voltage of feedback
Reference voltage poor and set in advance is compared, and control can so be better achieved.
A kind of multi-electrical level inverter low voltage traversing control method and equipment provided based on above example, the present invention is also
A kind of multi-electrical level inverter low voltage ride through control system is provided, is described in detail with reference to embodiment.
System embodiment one：
Referring to Figure 11, which is that multi-electrical level inverter low voltage ride through control system embodiment one provided by the invention is illustrated
Figure.
Multi-electrical level inverter low voltage ride through control system provided in this embodiment, including：Inverter 1100, PWM modulation
Device 1200 and controller 1300；
The inverter 1100, the DC inverter for solar energy pole plate to be exported feed back to power grid for alternating current；
The PWM modulator 1200, for output pwm signal under the control of the controller to the switching tube in inverter,
The on off state of controlling switch pipe；
The controller 1300, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall,
The asymmetry is fallen including two-phase short-circuit fault and single-phase grounding fault；Fall if it is determined that asymmetry occurs for network voltage
Fall, then power frequency common-mode voltage is injected into the given three-phase grid voltage for input to PWM modulator.
It should be noted that method provided in an embodiment of the present invention solar photovoltaic generation system suitable for sending not
When symmetrically falling failure.
Asymmetry, which falls failure, to be included：Two-phase short-circuit fault, single-phase grounding fault.For example, B phases ground short circuit event
Barrier, or, short trouble between A phases and B phases.
It is understood that this method is not suitable for symmetrically falling failure, i.e., short circuit occurs for A phases, B phases and C phase three-phases
Failure.
For example, for three-level inverter, bus capacitor midpoint electric current is by three-phase grid electric current and three-phase PWM switch function
Determine.When asymmetry, which occurs, for network voltage falls failure, bus capacitor midpoint electric current causes Down Highway there are larger fluctuation
The fluctuation of voltage.
When judging that generation asymmetry is fallen, it is necessary to before PWM modulator, injected into given three-phase grid voltage
Power frequency common-mode voltage.As shown in figure 4, given three-phase grid voltage is ua *、ub *And uc *；It should be noted that the power frequency of injection
Common-mode voltage is a vector, including power frequency common-mode voltage amplitude and phase.The amplitude and phase of the power frequency common-mode voltage of injection
It is to be determined by the drop depth of network voltage.
In solar photovoltaic generation system shown in Fig. 4, including two inverters, the two inverter parallels.
It is understood that in solar photovoltaic generation system, it can only include an inverter, can also include more
The inverter of a parallel running.
Control of the control system provided in this embodiment for each inverter is identical, is injected in each inverter identical
Power frequency common-mode voltage.It is understood that same PWM modulator 1200 and same control can be shared during multiple inverters
Device 1300 processed.
To sum up, multi-electrical level inverter low voltage ride through control system provided in this embodiment, controller 1300 are judging electricity
When net voltage generation asymmetry falls failure, power frequency common-mode voltage is injected into given three-phase grid voltage.Because power grid is electric
When pressure life asymmetry falls failure, busbar midpoint electric current can produce power frequency fluctuation, in order to reduce the power frequency of busbar midpoint electric current
Fluctuation, therefore, just injection power frequency common-mode voltage, the PWM that such PWM modulator 1200 exports believe before PWM modulator 1200
Number it is exactly to inject the later signal of power frequency common-mode voltage, since pwm signal is used for controlling the switch of switching tube in inverter 1300
State, therefore reduce or reduce the power frequency fluctuation of busbar midpoint electric current by controlling the work of inverter 1300.When in busbar
After the power frequency fluctuation of point electric current is reduced, the voltage stress that each switching tube is born in inverter 1300 can reduce, so not
Switching tube can be caused to damage.
The present invention provides the control mode of two kinds of power frequency common-mode voltages, one kind is opened loop control, and another kind is closed loop control
System, is discussed in detail with reference to specific embodiment.
System embodiment two：
Controller is introduced in the present embodiment in a manner of opened loop control to realize the operation principle of control.
Controller in the present embodiment, is additionally operable to the amplitude and phase of detection power grid three-phase voltage, and asymmetry was fallen
Three-phase reactive current and three-phase watt current in journey；It is idle according to the amplitude of the power grid three-phase voltage and phase and three-phase
Electric current and three-phase watt current determine the amplitude and phase of the power frequency common-mode voltage.
During operation of power networks, the three-phase voltage and three-phase current information of power grid can be gathered, therefore, passes through three-phase
Voltage falls it may determine that asymmetry whether occurs.In addition, it can determine to need what is injected by the information of voltage and current
The amplitude and phase of power frequency common-mode voltage.
Control system provided in this embodiment, it is not necessary to by the voltage of detection or current feedback to input terminal and set-point or
Person's predetermined value is compared, but the power frequency common-mode voltage of injection is directly determined according to the voltage and current of detection, is belonged to out
Ring controls, and this control is fairly simple, and it is convenient to realize.By injecting power frequency common-mode voltage, busbar midpoint electric current can be reduced
Power frequency fluctuation, so as to reduce the voltage stress that each switching tube is born in inverter, protection switch pipe is without prejudice.
System embodiment three：
Controller is introduced in the present embodiment in a manner of closed-loop control to realize the operation principle of control.
Controller in the present embodiment, is additionally operable to detection positive pole line voltage and negative busbar voltage；By the positive pole line voltage and
Negative busbar voltage obtains positive and negative busbar voltage difference；By the positive and negative busbar voltage difference compared with reference voltage, by comparing knot
Fruit determines the amplitude and phase of the power frequency common-mode voltage.
Since the difference of positive pole line voltage and negative busbar voltage can represent the fluctuation situation of busbar midpoint electric current, use
Positive and negative busbar voltage difference is used as feedback quantity, which is judged to the ripple of busbar midpoint electric current compared with reference voltage
It is dynamic.
It is understood that the reference voltage is voltage set in advance, calculate for convenience, in the embodiment of the present invention
Reference voltage can be set as zero.
In the present embodiment, using closed-loop control, positive and negative mother is obtained by the positive pole line voltage and negative busbar voltage of collection
Line voltage is poor, and positive and negative busbar voltage difference is fed back to input terminal compared with reference voltage, injection is determined by comparative result
Power frequency common-mode voltage amplitude and phase.The closed-loop control that the present embodiment uses, can pass through the positive and negative busbar voltage of feedback
Reference voltage poor and set in advance is compared, and control can so be better achieved.
It should be noted that the inverter in the control system that above example provides can be three-phase multi-level inverse conversion
Device；For example, three-level inverter, five-electrical level inverter etc..In addition, the inverter can also be an inverter, also may be used
Think the inverter of multiple parallel runnings, be, for example, two inverter parallels.
The topology of inverter can be T-shaped or I types.
It should be noted that the control system that above example of the present invention provides, due to reducing busbar midpoint electric current
Fluctuation, therefore the capacitance of bus capacitor is also reduced at the same time.Since in the case of identical busbar midpoint current fluctuation, bus capacitor
Capacitance it is bigger, the fluctuation of busbar mid-point voltage is smaller.The above described is only a preferred embodiment of the present invention, it is not pair
The present invention makees limitation in any form.Although the present invention is disclosed above with preferred embodiment, but it is not limited to this
Invention.Any those skilled in the art, without departing from the scope of the technical proposal of the invention, take off using above-mentioned
The methods and technical content shown makes technical solution of the present invention many possible changes and modifications, or is revised as equivalent variations
Equivalent embodiment.Therefore, every content without departing from technical solution of the present invention, the technical spirit according to the present invention are implemented to more than
Any simple modifications, equivalents, and modifications done of example, in the range of still falling within technical solution of the present invention protection.
Claims (8)
1. a kind of multi-electrical level inverter low voltage traversing control method, it is characterised in that applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Comprise the following steps：
The three-phase voltage of power grid is monitored, judges whether network voltage occurs asymmetry and fall；The asymmetry is fallen including two-phase
Short trouble and single-phase grounding fault；
Fall if asymmetry occurs for network voltage, inject work into the given three-phase grid voltage for inputing to PWM modulator
Frequency common-mode voltage to reduce the fluctuation of bus capacitor midpoint electric current, the power frequency common-mode voltage include power frequency common-mode voltage amplitude and
Phase；The PWM modulator is according to the given three-phase grid voltage output pwm signal to control opening for switching tube in inverter
Off status；
It is described to be injected into the given three-phase grid voltage for input to PWM modulator before power frequency common-mode voltage, further include：
Three-phase reactive current and three-phase in the amplitude and phase of detection power grid three-phase voltage, and asymmetric falling process is active
Electric current；
The work is determined according to the amplitude of the power grid three-phase voltage and phase and three-phase reactive current and three-phase watt current
The amplitude and phase of frequency common-mode voltage.
2. a kind of multi-electrical level inverter low voltage traversing control method, it is characterised in that applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Comprise the following steps：
The three-phase voltage of power grid is monitored, judges whether network voltage occurs asymmetry and fall；The asymmetry is fallen including two-phase
Short trouble and single-phase grounding fault；
Fall if asymmetry occurs for network voltage, inject work into the given three-phase grid voltage for inputing to PWM modulator
Frequency common-mode voltage to reduce the fluctuation of bus capacitor midpoint electric current, the power frequency common-mode voltage include power frequency common-mode voltage amplitude and
Phase；The PWM modulator is according to the given three-phase grid voltage output pwm signal to control opening for switching tube in inverter
Off status；It is described to be injected into the given three-phase grid voltage for input to PWM modulator before power frequency common-mode voltage, further include：
Detect positive pole line voltage and negative busbar voltage；
Positive and negative busbar voltage difference is obtained by the positive pole line voltage and negative busbar voltage；
By the positive and negative busbar voltage difference compared with reference voltage, the width of the power frequency common-mode voltage is determined by comparative result
Value and phase.
3. a kind of multi-electrical level inverter low voltage crossing control device, it is characterised in that applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Including：Judging unit and injection unit；
The judging unit, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall；It is described not
Symmetrically fall including two-phase short-circuit fault and single-phase grounding fault；
The injection unit, for when judging unit judges that network voltage occurs asymmetry and falls, to inputing to PWM modulator
Given three-phase grid voltage in inject power frequency common-mode voltage to reduce the fluctuation of bus capacitor midpoint electric current, the power frequency common mode
Voltage includes power frequency common-mode voltage amplitude and phase；The PWM modulator is believed according to the given three-phase grid voltage output PWM
Number to control the on off state of switching tube in inverter；
Further include：First detection unit and the first determination unit；
The first detection unit, for detecting in the amplitude and phase of power grid three-phase voltage, and asymmetric falling process
Three-phase reactive current and three-phase watt current；
First determination unit, for the amplitude according to the power grid three-phase voltage and phase and three-phase reactive current and three
Phase watt current determines the amplitude and phase of the power frequency common-mode voltage.
4. a kind of multi-electrical level inverter low voltage crossing control device, it is characterised in that applied to photovoltaic electric station grid connection operation
In inverter, DC inverter is by the DC supply input exported of the solar energy pole plate of photovoltaic plant to inverter, inverter
Alternating current is fed back into power grid after alternating current；Including：Judging unit and injection unit；
The judging unit, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall；It is described not
Symmetrically fall including two-phase short-circuit fault and single-phase grounding fault；
The injection unit, for when judging unit judges that network voltage occurs asymmetry and falls, to inputing to PWM modulator
Given three-phase grid voltage in inject power frequency common-mode voltage to reduce the fluctuation of bus capacitor midpoint electric current, the power frequency common mode
Voltage includes power frequency common-mode voltage amplitude and phase；The PWM modulator is believed according to the given three-phase grid voltage output PWM
Number to control the on off state of switching tube in inverter, further include：Second detection unit, positive and negative busbar voltage difference obtaining unit and
Second determination unit；
The second detection unit, for detecting positive pole line voltage and negative busbar voltage；
The positive and negative busbar voltage difference obtaining unit, for obtaining positive and negative busbar electricity by the positive pole line voltage and negative busbar voltage
Pressure difference；
Second determination unit, for by the positive and negative busbar voltage difference compared with reference voltage, it is true by comparative result
The amplitude and phase of the fixed power frequency common-mode voltage.
A kind of 5. multi-electrical level inverter low voltage ride through control system, it is characterised in that including：Inverter, PWM modulator and control
Device processed；
The inverter, the DC inverter for solar energy pole plate to be exported feed back to power grid for alternating current；
The PWM modulator, for output pwm signal under the control of the controller to the switching tube in inverter, controlling switch
The on off state of pipe；
The controller, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall, described not right
Title falls including two-phase short-circuit fault and single-phase grounding fault；If it is determined that network voltage occur asymmetry fall, then to
Input to and power frequency common-mode voltage is injected in the given three-phase grid voltage of PWM modulator to reduce the ripple of bus capacitor midpoint electric current
Dynamic, the power frequency common-mode voltage includes power frequency common-mode voltage amplitude and phase；
The controller, the three-phase being additionally operable in the amplitude and phase of detection power grid three-phase voltage, and asymmetric falling process
Reactive current and three-phase watt current；According to the amplitude of the power grid three-phase voltage and phase and three-phase reactive current and three-phase
Watt current determines the amplitude and phase of the power frequency common-mode voltage.
6. multi-electrical level inverter low voltage ride through control system according to claim 5, it is characterised in that the inverter
For three-phase multi-electrical level inverter；
The inverter is at least two parallel runnings.
A kind of 7. multi-electrical level inverter low voltage ride through control system, it is characterised in that including：Inverter, PWM modulator and control
Device processed；
The inverter, the DC inverter for solar energy pole plate to be exported feed back to power grid for alternating current；
The PWM modulator, for output pwm signal under the control of the controller to the switching tube in inverter, controlling switch
The on off state of pipe；
The controller, for monitoring the three-phase voltage of power grid, judges whether network voltage occurs asymmetry and fall, described not right
Title falls including two-phase short-circuit fault and single-phase grounding fault；If it is determined that network voltage occur asymmetry fall, then to
Input to and power frequency common-mode voltage is injected in the given three-phase grid voltage of PWM modulator to reduce the ripple of bus capacitor midpoint electric current
Dynamic, the power frequency common-mode voltage includes power frequency common-mode voltage amplitude and phase；The controller, is additionally operable to detection positive pole line voltage
With negative busbar voltage；Positive and negative busbar voltage difference is obtained by the positive pole line voltage and negative busbar voltage；By positive and negative busbar electricity
Pressure difference is determined the amplitude and phase of the power frequency common-mode voltage by comparative result compared with reference voltage.
8. multi-electrical level inverter low voltage ride through control system according to claim 7, it is characterised in that the inverter
For three-phase multi-electrical level inverter；
The inverter is at least two parallel runnings.
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| CN107465207B (en) * | 2017-08-11 | 2019-08-13 | 阳光电源股份有限公司 | Flying capacitor five-electrical level inverter and its low voltage traversing control method and device |
| CN110426601A (en) * | 2019-08-22 | 2019-11-08 | 金华电力设计院有限公司 | A kind of Fault Locating Method of earth-free photovoltaic system |
| CN111181430B (en) * | 2020-01-10 | 2021-04-27 | 山东大学 | Neutral point balance control method and system for three-level inverter under low-voltage ride-through condition |
| CN113644631B (en) * | 2021-09-17 | 2022-04-26 | 锦浪科技股份有限公司 | Processing method for half bus short circuit |
| CN114530883A (en) * | 2022-01-18 | 2022-05-24 | 国网冀北电力有限公司 | Power control method, device and system of light storage integrated grid-connected inverter |
| CN117134417B (en) * | 2023-10-26 | 2024-02-06 | 锦浪科技股份有限公司 | Photovoltaic inverter voltage cross-over current regulation method, device and storage medium |
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