CN105576652B - A kind of voltage control method and system of D.C. high voltage transmission sending end - Google Patents

Abstract

The invention discloses a voltage control method and system for a high-voltage direct current transmission sending end, which judges whether the sending end is in an island operation state, and performs active and reactive power cooperative control based on adaptive voltage-reactive power sensitivity and voltage-active power sensitivity in the island mode, In the network mode, the reactive power voltage control is carried out according to the normal voltage regulation coefficient, and the reactive power setting value of each AVC (automatic voltage control) unit is calculated according to the reactive power distribution method, and finally the excitation regulator of each AVC unit is based on the above reactive power Power setpoint for local closed-loop control. According to the different operating conditions of the high-voltage direct current transmission sending end system, the present invention avoids large fluctuations of the high-voltage bus voltage of the power plant in an island mode due to the mismatch of the AVC voltage regulation coefficient and active power regulation. The invention can be widely used in the field of automatic voltage control of electric power system.

Description

A voltage control method and system for a high-voltage direct current transmission terminal

technical field

The invention relates to the field of automatic voltage control of electric power systems, in particular to a voltage control method and system for a sending end of high-voltage direct current transmission.

Background technique

Yunnan and Guizhou in the west of China Southern Power Grid are large-scale sending-end systems, which transmit hydropower from the west to the load center in the east through large-capacity UHV/UHV DC lines. The large-capacity DC transmission system adopts the isolated island operation mode at the sending end, which can reduce the impact of power flow transfer on the AC system after a DC trip, and has unique advantages in improving the stability of the long-distance power transmission system and increasing the power transmission capacity.

AVC (Automatic Voltage Control of Power Plant) refers to the technology of automatically controlling the busbar voltage of the power plant or the reactive power of the whole power plant according to predetermined conditions and requirements. Under the condition of ensuring the safe operation of the unit, it provides the system with fully usable reactive power and reduces the power loss of the power plant. The AVC substation system of the power plant receives the control targets of the whole plant (high-voltage bus voltage of the power plant, total reactive power of the whole plant, etc.) issued by the AVC master station system, and reasonably allocates them to each By adjusting the reactive power output of the generator, the target control value of the whole plant is reached, and the automatic control of voltage and reactive power of multiple units in the whole plant is realized. The whole control process is shown in Figure 1.

In island operation conditions, the short circuit of the system is relatively small, that is, the same amount of reactive power variation will cause greater voltage fluctuations than in networked conditions, so the voltage regulation coefficient of the AVC system is reduced, so that the reactive power adjustment corresponding to the same voltage deviation The amplitude is reduced to achieve the purpose of reducing the gain and preventing the voltage from oscillating greatly. A lower voltage regulation coefficient can meet the needs of steady-state voltage regulation, but in the process of island steady-state power ups and downs, with the decrease and increase of the transmission power of the island system, the voltage of the island power plant and converter station will also increase significantly or lower. From the sensitivity analysis, it can be seen that the voltage of the island system is highly sensitive to the change of active power, so the power plant power fluctuation will cause large-scale voltage fluctuations.

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is: a method of adaptively setting voltage-reactive power sensitivity and voltage-active power sensitivity through online network analysis, and considering the influence of active power adjustment on voltage, thereby avoiding power plant and converter station bus voltage A voltage control method at the sending end of high-voltage direct current transmission with large fluctuations.

In order to solve the above-mentioned technical problems, another object of the present invention is: a method of adaptively setting voltage-reactive power sensitivity and voltage-active power sensitivity through online network analysis, considering the influence of active power adjustment on voltage, thereby avoiding the The voltage control system at the sending end of HVDC transmission where the bus voltage fluctuates greatly.

The traditional AVC (automatic voltage control) reactive power adjustment cannot synchronously compensate the voltage deviation caused by active power. It is necessary to introduce active power adjustment information into the AVC reactive power adjustment and improve it into a voltage controller that can compensate for active power adjustment.

The technical solution adopted in the present invention is: a voltage control method of a high-voltage direct current transmission terminal, including the following steps:

A. At the sending end of the long-distance HVDC transmission, the island detection module is used to detect whether the sending end is in an island operation state;

B. If the sending end is in the island operation state, set the voltage regulation coefficient of the power plant according to the island system voltage-reactive power sensitivity, and calculate the reactive power compensation coefficient for active power adjustment according to the island system adaptive voltage-active power sensitivity, and then perform active and reactive power adjustment. Coordinated control of functions, execute step D;

C. If the sending end is in the networked state, use the normal voltage regulation coefficient in the networked state to control the reactive power voltage, and perform step D;

D. Calculate the reactive power setting value of each AVC unit according to the reactive power distribution method;

E. The excitation regulators of each AVC unit perform local closed-loop control according to the above reactive power setting value.

Further, the calculation formula for active and reactive power coordinated control based on adaptive voltage-reactive power sensitivity and voltage-active power sensitivity in the step B is:

in,

Q _AVC is the reactive AVC distribution value of the whole plant;

Q _ACT is the current actual reactive power;

ΔV is the deviation between the actual bus voltage and the given voltage value;

K _{V_islanded} is the voltage regulation coefficient of the power plant under the island mode;

ΔP K _p is the reactive power compensation amount of active power adjustment of the island generator set, ΔP is the active power adjustment amount of the island generator set, and K _P is the reactive power compensation coefficient for active power adjustment;

It is the sum of reactive power generated by units not participating in AVC.

Further, the K _{V_islanded} and K _P values are determined according to the voltage-active power sensitivity matrix and the voltage-reactive power sensitivity matrix of the power flow equation.

Further, in the step C, the calculation formula for reactive power voltage control according to the normal voltage regulation coefficient under the networking state is:

in,

Q _AVC is the reactive AVC distribution value of the whole plant;

Q _ACT is the current actual reactive power;

ΔV is the deviation between the actual bus voltage and the given voltage value;

K _{V_networked} is the normal voltage regulation coefficient;

It is the sum of reactive power generated by units not participating in AVC.

Further, the reactive power allocation method in the step D is to allocate the reactive power value of each AVC unit according to the principle of equal power factors, the principle of proportional reactive power capacity, the principle of similar adjustment margin or the principle of dynamic optimization.

Further, the reactive power allocation method in the step D is to allocate the reactive power value of each AVC unit according to the principle of similar adjustment margin, and the calculation formula for the allocation is:

in,

n is the number of crews participating in AVC;

Q _iMax -Q _i is the reactive power adjustment margin of the i-th unit participating in AVC;

is the sum of the current reactive power adjustment margins of participating AVC units;

Q _iAVC is the reactive power output of AVC assigned to the i-th unit participating in the AVC unit.

Another technical solution adopted by the present invention is: a voltage control system at the sending end of high-voltage direct current transmission, including:

The island detection module is used to detect whether the sending end of the long-distance HVDC power transmission is in an island operation state;

The island operation control module is used to set the voltage regulation coefficient of the power plant online according to the island system voltage-reactive power sensitivity when the sending end is in the island operation state, and calculate the reactive power compensation coefficient for active power adjustment according to the island system adaptive voltage-active power sensitivity , to carry out active and reactive power coordinated control;

The networking control module is used to control the reactive power voltage using the normal voltage regulation coefficient in the networking state when the sending end is in the networking state;

The reactive power distribution module is used to calculate the reactive power setting value of each AVC unit according to the reactive power distribution method;

The AVC unit in the system uses the excitation regulator of the AVC unit to perform local closed-loop control according to the above-mentioned reactive power setting value.

The beneficial effects of the present invention are: the method of the present invention is based on the different operating conditions of the high-voltage direct current transmission sending end system, and in the islanding condition, according to the calculation of the sensitivity of the island voltage to reactive power, a smaller voltage regulation coefficient is used to avoid the voltage cycle of the island system Sexual oscillation; according to the sensitivity of the island voltage to active power, cooperate with the active power adjustment information to prevent the high-voltage bus voltage of the power plant from falling sharply with the increase or decrease of the output power of the system.

Another beneficial effect of the present invention is: the system of the present invention adapts to different operating conditions of the high-voltage direct current transmission sending end system, and adopts a normal voltage regulation coefficient for reactive voltage control in the networking condition; in the island condition, according to the island voltage - Reactive power sensitivity and voltage-active power sensitivity, AVC and active power adjustment information are combined to carry out active and reactive power coordinated control, so as to avoid the large drop and increase of the high voltage bus voltage of the power plant with the increase or decrease of the system output power.

Description of drawings

Fig. 1 is the overall transfer function block diagram of prior art voltage control;

Fig. 2 is a flow chart of the steps of the inventive method;

Fig. 3 is the structural representation of the system of the present invention;

FIG. 4 is a schematic structural diagram of an island system in an embodiment of the present invention;

Fig. 5 is a block diagram of the overall transfer function of the voltage control of the present invention.

Detailed ways

The specific embodiment of the present invention will be further described below in conjunction with accompanying drawing:

Referring to FIG. 2 , a voltage control method for a high-voltage direct current transmission transmission terminal includes the following steps:

A. At the sending end of the long-distance HVDC transmission, the island detection module is used to detect whether the sending end is in an island operation state;

B. If the sending end is in the island operation state, set the voltage regulation coefficient of the power plant according to the island system adaptive voltage-reactive power sensitivity, and calculate the reactive power compensation coefficient with active power adjustment according to the island system adaptive voltage-active power sensitivity to perform active power Reactive power coordinated control, execute step D;

C. If the sending end is in the networked state, use the normal voltage regulation coefficient in the networked state to control the reactive power voltage, and perform step D;

D. Calculate the reactive power setting value of each AVC unit according to the reactive power distribution method;

E. The excitation regulators of each AVC unit perform local closed-loop control according to the above reactive power setting value.

Further as a preferred embodiment, in the definite value mode of the island working condition, the AVC of the power plant calculates the reactive power output of the whole plant according to the given bus voltage value, and the goal is to maintain the bus voltage of the power plant at a given level; in the step B The calculation formula for active and reactive power cooperative control based on adaptive voltage-reactive power sensitivity and voltage-active power sensitivity is:

in,

Q _AVC is the reactive AVC distribution value of the whole plant;

Q _ACT is the current actual reactive power;

ΔV is the deviation between the actual bus voltage and the given voltage value;

K _{V_islanded} is the voltage regulation coefficient of the power plant under the island mode;

ΔP K _p is the reactive power compensation amount of active power adjustment of the island generator set, ΔP is the active power adjustment amount of the island generator set, and K _P is the reactive power compensation coefficient for active power adjustment;

It is the sum of reactive power generated by units not participating in AVC.

As a further preferred embodiment, the K _{V_islanded} and K _P values are determined according to the voltage-reactive power sensitivity matrix and the voltage-active power sensitivity matrix of the power flow equation.

For the reactive power compensation coefficient K _P that cooperates with active power adjustment, it is necessary to obtain the system operating state through state estimation, and perform online calculation to obtain adaptive parameter values. because To calculate K _P , the voltage-active power sensitivity matrix and the voltage-reactive power sensitivity matrix must be obtained first. The specific process is as follows.

List the extended power flow equations,

Find the partial derivatives of active and reactive power with respect to node voltage and phase angle, and the sensitivity matrix can be obtained,

In order to represent the following characteristics of PV nodes and balance nodes,

Perform the following operations on S: set the column vector indicating the sensitivity about the reference phase angle to zero; set the column vector indicating the sensitivity about the PV node and the balance node voltage to zero; The row vector of the reactive sensitivity of the balance node is set to zero; the diagonal elements intersecting the row vector and the column vector are set to 1. In the power vector, the elements corresponding to the reactive power of the PV node and the active power and reactive power of the balance node are set to zero.

Through the above operations, and then inverse S, we get

Among them, voltage-active power sensitivity and voltage-reactive power sensitivity information can be obtained from S _VP and S _VQ respectively.

Further as a preferred embodiment, the voltage-active power sensitivity of the networking working condition can be ignored, regardless of the cooperation with the active power regulation, and the voltage-reactive power sensitivity does not change much with the power adjustment. The calculation formula for reactive power voltage control is as follows:

in,

Q _AVC is the reactive AVC distribution value of the whole plant;

Q _ACT is the current actual reactive power;

ΔV is the deviation between the actual bus voltage and the given voltage value;

K _{V_networked} is the normal voltage regulation coefficient;

It is the sum of reactive power generated by units not participating in AVC.

As a further preferred embodiment, the reactive power allocation method in the step D is to allocate the reactive power value of each AVC unit according to the principle of equal power factors, proportionality of reactive power capacity, similar adjustment margin or dynamic optimization.

Further as a preferred embodiment, taking the similar adjustment margin principle as an example, the reactive power distribution method in the step D is to distribute the reactive power values of each AVC unit according to the similar adjustment margin principle, and the calculation formula for distribution is:

in,

n is the number of crews participating in AVC;

Q _iMax -Q _i is the reactive power adjustment margin of the i-th unit participating in AVC;

is the sum of the current reactive power adjustment margins of participating AVC units;

Q _iAVC is the reactive power output of AVC assigned to the i-th unit participating in the AVC unit.

Taking the isolated island system in Fig. 4 as an example, the specific embodiment of the method of the present invention applied to the isolated island system is illustrated. The double-circuit line is connected to the Chuxiong converter station. In addition, the Heping station is connected in parallel between Xiaowan Power Plant and Chuxiong station via a single-circuit line, and the Heping station is connected to the synchronous power grid. The Chusui DC island discrimination system is composed of the island discrimination devices of Chuxiong Station, Xiaowan Power Plant and Heping Station.

In the network mode, according to the calculation results of voltage-reactive power sensitivity, the AVC voltage regulation coefficient of Xiaowan Power Plant is K _{V_networked} = 6MVar/kV, that is, the voltage deviation is 1kV, and the reactive power should be adjusted by 6MVar. The sensitivity of active power to voltage can be adjusted in large power grids. Almost ignored. The AVC of the power plant under the network working condition calculates the reactive power according to the following formula:

In the island mode, according to the calculation result of the sensitivity of the voltage to reactive power, the actual voltage regulation coefficient K _{V_islanded} = 2MVar/kV, if the constant voltage regulation coefficient is still adjusted in the network condition, there will be fluctuations caused by overshooting, and it must be adjusted according to the network status Adaptive adjustment.

In the island mode, the sensitivity of voltage to active power increases significantly, and the continuous rise or fall of power plant active power has a significant impact on the voltage amplitude of the high-voltage busbar of the power plant. The influence of this makes the bus voltage more stable.

According to the result of sensitivity calculation, at the power level of 2500MW of the island system, the active power is increased by 1MW, and the reactive power must be increased by 0.25MVar to maintain a constant voltage. The online calculation K _P =0.25, the calculation formula adopts:

The block diagram of the overall transfer function of AVC control in the island mode is shown in Figure 5.

Referring to Figure 3, a voltage control system at the sending end of HVDC power transmission includes:

The island detection module is used to detect whether the sending end of the long-distance HVDC power transmission is in an island operation state;

The island operation control module is used to set the voltage regulation coefficient of the power plant according to the island system adaptive voltage-reactive power sensitivity when the sending end is in the island operation state, and calculate the reactive power for active power adjustment according to the island system adaptive voltage-active power sensitivity Compensation coefficient for active and reactive power coordinated control;

The networking control module is used to control the reactive power voltage using the normal voltage regulation coefficient in the networking state when the sending end is in the networking state;

The reactive power distribution module is used to calculate the reactive power setting value of each AVC unit according to the reactive power distribution method;

The AVC unit in the system uses the excitation regulator of the AVC unit to perform local closed-loop control according to the above-mentioned reactive power setting value.

The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the described embodiments, and those skilled in the art can also make various equivalent transformations or replacements without violating the spirit of the present invention. These equivalent modifications or replacements are all within the scope defined by the claims of the present application.

Claims (5)

1. A voltage control method of a high-voltage direct-current transmission terminal is characterized by comprising the following steps: the method comprises the following steps:

A. detecting whether a sending end of the long-distance high-voltage direct-current transmission is in an island operation state or not through an island detection module;

B. if the sending end is in an island operation state, setting a power plant voltage regulating coefficient according to the self-adaptive voltage-reactive sensitivity of the island system, calculating a reactive compensation coefficient matched with active regulation according to the self-adaptive voltage-active sensitivity of the island system, further performing active and reactive cooperative control, and executing the step D;

C. if the sending end is in the networking state, the reactive voltage is controlled by using the normal voltage regulating coefficient in the networking state, and the step D is executed;

D. calculating a reactive power set value of each AVC unit according to a reactive power distribution method;

E. each AVC unit excitation regulator carries out local closed-loop control according to the reactive power set value;

the reactive compensation coefficient K matched with active power regulation_PThe value is determined according to a voltage-reactive sensitivity matrix and a voltage-active sensitivity matrix of the power flow equation; the specific calculation process is as follows:

the expanded power flow equation is listed,

<mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>=</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>V</mi> <mi>j</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>G</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>cos&amp;delta;</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>B</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>sin&amp;delta;</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>Q</mi> <mi>i</mi> </msub> <mo>=</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>V</mi> <mi>j</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>G</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>sin&amp;delta;</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>B</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>cos&amp;delta;</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced>

partial derivatives of active power and reactive power to the node voltage and the phase angle are calculated to obtain a sensitivity matrix:

<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>P</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>Q</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mo>-</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>H</mi> </mtd> <mtd> <mi>N</mi> </mtd> </mtr> <mtr> <mtd> <mi>K</mi> </mtd> <mtd> <mi>L</mi> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mi>S</mi> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> </mrow>

the following operations are performed on S: zero-setting a column vector representing sensitivity with respect to a reference phase angle; zero-setting a column vector representing sensitivity with respect to the PV node and balance node voltages; setting a row vector representing the active sensitivity of the balance node to zero; zero setting of a row vector representing reactive sensitivity of the PV node and the balance node; setting the diagonal line element intersected by the row vector and the column vector as 1; in the power vector, elements corresponding to PV node reactive power, balance node active power and reactive power are set to zero;

then, the S is inverted to obtain

<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>S</mi> <mrow> <mi>&amp;delta;</mi> <mi>P</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>S</mi> <mrow> <mi>&amp;delta;</mi> <mi>Q</mi> </mrow> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>S</mi> <mrow> <mi>V</mi> <mi>P</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>S</mi> <mrow> <mi>V</mi> <mi>Q</mi> </mrow> </msub> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>P</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>Q</mi> </mtd> </mtr> </mtable> </mfenced> </mrow>

Wherein, from S_VPAnd S_VQCan respectively obtain voltage-active powerSensitivity and voltage-reactive sensitivity, and then calculating a reactive compensation coefficient matched with active power regulation:

<mrow> <msub> <mi>K</mi> <mi>p</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mo>&amp;part;</mo> <mi>Q</mi> </mrow> <mrow> <mo>&amp;part;</mo> <mi>V</mi> </mrow> </mfrac> <mfrac> <mrow> <mo>&amp;part;</mo> <mi>V</mi> </mrow> <mrow> <mo>&amp;part;</mo> <mi>P</mi> </mrow> </mfrac> </mrow>

and B, performing active and reactive cooperative control based on the adaptive sensitivity in the step B by using a calculation formula as follows:

<mrow> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>C</mi> <mi>T</mi> </mrow> </msub> <mo>+</mo> <mi>&amp;Delta;</mi> <mi>V</mi> <mo>&amp;CenterDot;</mo> <msub> <mi>K</mi> <mrow> <mi>V</mi> <mo>_</mo> <mi>i</mi> <mi>s</mi> <mi>l</mi> <mi>a</mi> <mi>n</mi> <mi>d</mi> <mi>e</mi> <mi>d</mi> </mrow> </msub> <mo>+</mo> <mi>&amp;Delta;</mi> <mi>P</mi> <mo>&amp;CenterDot;</mo> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>-</mo> <msub> <mi>Q</mi> <mover> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> <mo>&amp;OverBar;</mo> </mover> </msub> </mrow>

wherein,

Q_AVCdistributing a value for the reactive AVC of the whole plant;

Q_ACTreactive power is generated for the current real time;

Δ V is the deviation of the actual bus voltage from the given voltage value;

K_{V_islanded}voltage regulation coefficient of power plant in island mode, K_{V_islanded}＝2MVar/kV；

ΔP·K_pReactive compensation quantity for active regulation of island generator set, delta P is active regulation quantity of island generator set, K_PThe reactive compensation coefficient is matched with active power regulation;

the sum of reactive power generated by the AVC unit is not participated.

2. The voltage control method of the high-voltage direct-current transmission terminal according to claim 1, characterized by comprising the following steps: in the step C, a calculation formula for performing reactive voltage control by using the normal voltage regulation coefficient in the networking state is as follows:

<mrow> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>C</mi> <mi>T</mi> </mrow> </msub> <mo>+</mo> <mi>&amp;Delta;</mi> <mi>V</mi> <mo>&amp;CenterDot;</mo> <msub> <mi>K</mi> <mrow> <mi>V</mi> <mo>_</mo> <mi>n</mi> <mi>e</mi> <mi>t</mi> <mi>w</mi> <mi>o</mi> <mi>r</mi> <mi>k</mi> <mi>e</mi> <mi>d</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>Q</mi> <mover> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> <mo>&amp;OverBar;</mo> </mover> </msub> </mrow>

wherein,

Q_AVCdistributing a value for the reactive AVC of the whole plant;

Q_ACTreactive power is generated for the current real time;

Δ V is the deviation of the actual bus voltage from the given voltage value;

K_{V_networked}the normal voltage regulation coefficient;

the sum of reactive power generated by the AVC unit is not participated.

3. The voltage control method of the high-voltage direct-current transmission terminal according to claim 1, characterized by comprising the following steps: and D, distributing the reactive power set value of each AVC set according to an equal power factor principle, a reactive capacity proportional principle, a similar adjustment margin principle or a dynamic optimization principle.

4. The voltage control method of the HVDC transmission terminal of claim 3, wherein: the reactive power distribution method in the step D is to distribute reactive power set values of all AVC sets according to a similarity adjustment margin principle, and the distributed calculation formula is as follows:

<mrow> <msub> <mi>Q</mi> <mrow> <mi>i</mi> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> </msub> <mo>&amp;times;</mo> <mfrac> <mrow> <msub> <mi>Q</mi> <mrow> <mi>i</mi> <mi>M</mi> <mi>a</mi> <mi>x</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>Q</mi> <mi>i</mi> </msub> </mrow> <mrow> <msubsup> <mi>&amp;Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </msubsup> <mrow> <mo>(</mo> <msub> <mi>Q</mi> <mrow> <mi>i</mi> <mi>M</mi> <mi>a</mi> <mi>x</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>Q</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>,</mo> <mi>i</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mo>...</mo> <mo>,</mo> <mi>n</mi> </mrow>

wherein,

n is the number of sets participating in AVC;

Q_iMax-Q_iadjusting the margin for the reactive power of the ith unit participating in AVC;

the sum of the current reactive power adjustment margins of the AVC units is obtained;

Q_iAVCand distributing reactive power output of the ith station participating in the AVC set for AVC.

5. A voltage control system of high voltage direct current transmission send end which characterized in that: comprises that

The island detection module is used for detecting whether a sending end of the long-distance high-voltage direct-current transmission is in an island operation state;

the island operation control module is used for setting a power plant voltage regulating coefficient according to the self-adaptive voltage-reactive sensitivity of the island system when the sending end is in an island operation state, calculating a reactive compensation coefficient of power plant active regulation according to the self-adaptive voltage-reactive sensitivity of the island system, and further performing active and reactive cooperative control; reactive compensation coefficient K matched with active power regulation_PThe value is determined according to a voltage-reactive sensitivity matrix and a voltage-active sensitivity matrix of the power flow equation; the specific calculation process is：

The expanded power flow equation is listed,

<mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>=</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>V</mi> <mi>j</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>G</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>cos&amp;delta;</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>B</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>sin&amp;delta;</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>Q</mi> <mi>i</mi> </msub> <mo>=</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>V</mi> <mi>j</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>G</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>sin&amp;delta;</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>B</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msub> <mi>cos&amp;delta;</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced>

partial derivatives of active power and reactive power to the node voltage and the phase angle are calculated to obtain a sensitivity matrix:

<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>P</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>Q</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mo>-</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>H</mi> </mtd> <mtd> <mi>N</mi> </mtd> </mtr> <mtr> <mtd> <mi>K</mi> </mtd> <mtd> <mi>L</mi> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mi>S</mi> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> </mrow>

the following operations are performed on S: zero-setting a column vector representing sensitivity with respect to a reference phase angle; zero-setting a column vector representing sensitivity with respect to the PV node and balance node voltages; setting a row vector representing the active sensitivity of the balance node to zero; zero setting of a row vector representing reactive sensitivity of the PV node and the balance node; setting the diagonal line element intersected by the row vector and the column vector as 1; in the power vector, elements corresponding to PV node reactive power, balance node active power and reactive power are set to zero;

then, the S is inverted to obtain

<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <msup> <mi>V</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mi>&amp;Delta;</mi> <mi>V</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>S</mi> <mrow> <mi>&amp;delta;</mi> <mi>P</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>S</mi> <mrow> <mi>&amp;delta;</mi> <mi>Q</mi> </mrow> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>S</mi> <mrow> <mi>V</mi> <mi>P</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>S</mi> <mrow> <mi>V</mi> <mi>Q</mi> </mrow> </msub> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>P</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>Q</mi> </mtd> </mtr> </mtable> </mfenced> </mrow>

Wherein, from S_VPAnd S_VQThe voltage-active sensitivity and the voltage-reactive sensitivity can be respectively obtained, and then the reactive compensation coefficient matched with active regulation is calculated:

<mrow> <msub> <mi>K</mi> <mi>p</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mo>&amp;part;</mo> <mi>Q</mi> </mrow> <mrow> <mo>&amp;part;</mo> <mi>V</mi> </mrow> </mfrac> <mfrac> <mrow> <mo>&amp;part;</mo> <mi>V</mi> </mrow> <mrow> <mo>&amp;part;</mo> <mi>P</mi> </mrow> </mfrac> </mrow>

the calculation formula for performing active and reactive cooperative control based on the adaptive sensitivity is as follows:

<mrow> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>Q</mi> <mrow> <mi>A</mi> <mi>C</mi> <mi>T</mi> </mrow> </msub> <mo>+</mo> <mi>&amp;Delta;</mi> <mi>V</mi> <mo>&amp;CenterDot;</mo> <msub> <mi>K</mi> <mrow> <mi>V</mi> <mo>_</mo> <mi>i</mi> <mi>s</mi> <mi>l</mi> <mi>a</mi> <mi>n</mi> <mi>d</mi> <mi>e</mi> <mi>d</mi> </mrow> </msub> <mo>+</mo> <mi>&amp;Delta;</mi> <mi>P</mi> <mo>&amp;CenterDot;</mo> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>-</mo> <msub> <mi>Q</mi> <mover> <mrow> <mi>A</mi> <mi>V</mi> <mi>C</mi> </mrow> <mo>&amp;OverBar;</mo> </mover> </msub> </mrow>

wherein,

Q_AVCdistributing a value for the reactive AVC of the whole plant;

Q_ACTreactive power is generated for the current real time;

Δ V is the deviation of the actual bus voltage from the given voltage value;

K_{V_islanded}voltage regulation coefficient of power plant in island mode, K_{V_islanded}＝2MVar/kV；

ΔP·K_pReactive compensation quantity for active regulation of island generator set, delta P is active regulation quantity of island generator set, K_PThe reactive compensation coefficient is matched with active power regulation;

the sum of the reactive power generated by the AVC unit is not participated;

the networking control module is used for performing reactive voltage control by using a normal voltage regulation coefficient in a networking state when the sending end is in the networking state;

the reactive power distribution module is used for calculating a reactive power set value of each AVC unit according to a reactive power distribution method;

and the AVC set in the system performs local closed-loop control by using an AVC set excitation regulator according to the reactive power set value.