JPH1189096A - Operation control method of distributed power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a parallel synchronous operations of respective distributed power supply devices, when the respective distributed power supply devices are paralleled off from a power system into self-contained operations, while synchronism is not obtained by exchanging information on output powers, output currents, etc., between the distributed power supply devices. SOLUTION: When a plurality of distributed power supply devices (solar generators 1) which are paralleled off from a power system 5 are put into self-contained operations, an inverter 3 of one of the respective distributed power supply devices is used as a reference inverter. The reference inverter is operated by a voltage control operation to form an AC voltage source. After the reference inverter generates a voltage, the inverters 3 of the remaining distributed power supply devices are operated by current control operation synchronously with the output voltage of the reference inverter. Through the current control operation, AC-current sources synchronous with the AC voltage source are respectively formed, and the parallel synchronous operations of the respective distributed power supply devices are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method for operating a plurality of distributed power supplies disconnected from an electric power system.

[0002]

2. Description of the Related Art Conventionally, as a distributed power source, there is a photovoltaic power generation device that converts DC power of a solar cell provided on a roof or the like into AC power by an inverter and supplies the AC power to a load of premises equipment.

[0003] When the system power supply is normal (always), the solar power generation system is operated in an interconnected manner with the electric power system. And supplies power mainly to so-called important loads such as loads for disaster prevention and loads at shelters.

[0004] When a plurality of distributed power sources such as photovoltaic power generators are used to construct a distributed power supply system and operate in parallel, in the case of the self-sustaining operation, for example, the output voltage between the photovoltaic power generators is reduced. In order to prevent unbalance and increase the load capacity, and to supply sufficient power to disaster prevention loads and shelter loads, adjust the phase and magnitude (amplitude) of the output voltage of the inverter of each power generator. There is a need.

[0005] During the interconnection operation, the inverters of the respective photovoltaic power generators are controlled by current control in synchronization with the voltage of the system power supply (system voltage). Phase of the inverter output voltage,
The sizes match, and each solar power generation device is operated in parallel and synchronously. However, during the self-sustaining operation, there is no common synchronization information between the respective photovoltaic power generators.

[0006] In order to match the phase and magnitude of the output voltage of the inverter of each photovoltaic power generator during self-sustained operation, the following operation control methods have been conventionally proposed.

(A) Master-slave control In this method, one of the inverters of each photovoltaic power generation device is used as a master inverter, and the inverters of the remaining photovoltaic power generation devices are used as slave inverters. Phase synchronization signal,
Information related to the output such as amplitude signal is transmitted, and this information is used as common information of the synchronous operation. The inverters of the respective photovoltaic power generators are operated in parallel and synchronously, and the control method for adjusting the phase and magnitude of their output voltages is performed. is there.

(B) Load sharing control This is a control method adopted for parallel operation of uninterruptible power supply (UPS), and is a method for controlling the following (a), (b) or (c). is there.

(A) When the number of the solar power generation devices is n, the active power and the reactive power consumed by the load are equally distributed to the inverters of the respective solar power generation devices by 1 / n.

(B) The inverters of the respective photovoltaic power generators are operated such that the active power and the reactive power flowing between the respective photovoltaic power generators become zero.

(C) The output current of the inverter of each photovoltaic power generator is detected, and the inverter of each photovoltaic power generator is operated so that the imbalance of the output current between the inverters becomes zero.

[0012]

SUMMARY OF THE INVENTION The conventional master
Regardless of the operation control method of either the slave control or the load sharing control, when each of the photovoltaic power generation devices is disconnected from the power system and operates independently, the output power and the output current between the devices are controlled. It is necessary to exchange information related to the output such as the above, and to control the operation of the inverter of the own device in accordance with the exchange, and the same applies to a distributed power supply other than the solar power generation device.

Therefore, in the case of the conventional operation control method of this type of distributed power supply equipment, it is necessary to lay communication lines for exchanging information related to output such as output power and output current between the distributed power supplies. And there are problems such as high equipment costs.

Further, when the manufacturers of the inverters of the respective distributed power supplies are different, it is difficult to actually perform an appropriate parallel synchronous operation due to a difference in the control sequence between the distributed power supplies.

According to the present invention, when each of the distributed power sources is disconnected from the power system and is operated independently, information related to the output is exchanged between the distributed power sources and the parallel synchronous operation is not performed. The task is to be able to do so.

[0016]

In order to solve the above-mentioned problems, in the operation control method of the distributed power supply equipment according to the present invention, a plurality of distributed power supplies disconnected from the power system are operated independently. One of the inverters in each of the distributed power supplies is used as a reference inverter, and the reference inverter is operated under voltage control to form an AC voltage source. After the output voltage of the reference inverter is generated, the remaining distributed power supplies are used. Current control operation is performed on each of the inverters in synchronization with the output voltage of the reference inverter. The current control operation forms an AC current source synchronized with the AC voltage source, and the distributed power supplies are operated in parallel and synchronously.

Therefore, when each of the distributed power sources is disconnected from the power system and is operated independently, first, the reference inverter is voltage-controlled to form an AC voltage source.

Further, the inverters of the remaining distributed power supplies are each operated under current control with a delay from the reference inverter, thereby forming an AC current source.

At this time, the voltage of the load power supply is determined by the reference inverter voltage, and the output currents of the remaining distributed power supply inverters have the same phase as the reference inverter output voltage.

Therefore, the output of the inverter of the remaining distributed power supply is synchronized with the output of the reference inverter, and each distributed power supply does not exchange information related to the output, etc. Is done.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the entire configuration of the distributed power supply equipment, and the distributed power supplies # 1, # 2,
Each of the photovoltaic power generation devices 1 of..., #N includes a parallel power supply device provided with a DC power storage medium 4 such as a solar cell 2, an inverter 3 and a storage battery.

Each solar cell 2 such as a PV panel is distributed and installed on a roof of a house or a factory or on a side wall of a highway,
Each photovoltaic power generator 1 may be separated by several hundred meters depending on the case.

Next, as shown in FIG. 2, the inverter 3 includes a switching circuit section 3a composed of a power switching semiconductor and the like, and a control circuit section 3 composed of a microcomputer and the like.
b and an instrument current transformer 3c and a transformer 3d, and the current transformer 3c has an AC output current Im (m = 1,
, N) and supplies a current measurement output im to the control circuit unit 3b. The transformer 3d measures each AC output voltage Vm equal to the load voltage Vout, and outputs a voltage measurement output vm (= vout). ) Is supplied to the control circuit unit 3b.

The control circuit 3b outputs the measurement outputs im, v
The switching circuit 3b is driven in accordance with the operation mode based on m and various contact signals not shown.

When the system power supply 6 of the power system 5 supplies power to the load 7 shown in FIG. 1 such as an in-house load, the system is operated normally during the day when the solar cell 2 generates power. 1
Are connected to the power system 5 under the control of the interconnection operation mode and are operated in parallel, and
The DC power of the solar cell 2 is supplied in parallel to a load 7 which is converted into AC power by the inverter 3.

At this time, the inverters 3 of the respective photovoltaic power generators 1 are all subjected to current control operation so that the respective output currents Im have the same phase as the voltage of the system power supply 6, and are operated in synchronization with the system power supply 6. .

Next, when the system power supply 6 is cut off due to a disaster or the like, each of the photovoltaic power generators 1 is disconnected from the power system 5 in order to prevent an electric shock due to so-called isolated operation.

A broken line in FIG. 1 indicates that the power system 5 is in a power outage state, and a cross in the figure indicates a disconnection point.

Then, when the self-sustaining operation mode is commanded to the inverters 3 of the respective photovoltaic power generators 1 by manual operation or automatic operation such as sequence control, the inverters 3 of the respective photovoltaic power generators 1 are operated as described below. Operate.

At this time, the switch 8 of each photovoltaic power generator 1 is turned on so that DC power can be supplied to the inverter 3 from the solar cell 2 and the DC power storage medium 4 so that power can be supplied to the load 7 even at night. Power is supplied in parallel.

When the inverter 3 of the # 1 photovoltaic power generator 1 is set as the reference inverter, first, only the inverter 3 of the # 1 photovoltaic power generator 1 (hereinafter referred to as # 1 inverter) is used. Start voltage control operation.

At this time, the control circuit section 3b of the inverter 3 of # 1 operates the voltage control function of FIG. 3 according to the voltage-type inverter control program.

[0033] Then, the output current detecting means 9 on the basis of the current measurement output i _1, # 1 of the output current I1, for example, 50-90% of the rated inverter 3 low until rises to the set value Iα of rms A voltage increase command (L) is formed and output.

The digital or analog reference frequency forming means (not shown) may be configured to repeat the reading of one cycle of waveform data or the free-running oscillation of the oscillator, so that when the system power supply 6 is 60 Hz, 2π · 60, 50 Hz is used. In this case, a signal having a reference angular frequency ω ₀ of 2π · 50 (= 2π · f, where f is a frequency) is always formed.

Then, the output voltage V of the inverter 3 of # 1
Since 1 in the voltage of the reference angular frequency omega ₀ of up to rated voltage Vc determine the load voltage Vout, the operation reference signal generating means 10, based on the reference angular frequency omega ₀ of the signal amplitude | v | sinusoidal waveform Voltage control reference signal | v | sin (ω
₀ · t) is formed, the amplitude | increases from 0 at the soft start characteristic during voltage increase command a is input | v.

Further, the subtracter 11 calculates an error between the voltage control reference signal of the generating means 9 and the voltage measurement output v ₁ which is the detection output of the current load voltage Vout, and converts the error signal into a feedback control signal. It is supplied to the processing means 12.

The signal processing means 12 performs signal processing of general feedback control such as P (proportional) -I (integral) control on the error signal to form a voltage-controlled inverter drive signal. A signal is supplied from the control circuit unit 3b to the switching circuit unit 3a to switch the circuit unit 3a.

By this switching drive, the inverter 3 of # 1 is operated under voltage control by self-synchronous control based on its own voltage control reference signal to form an AC voltage source having an angular frequency ω _0. In the soft start characteristic, the voltage increases from 0 with the upper limit of the rated voltage Vc.

On the other hand, the output voltage V1 of the inverter 3 of # 1
The load voltage Vout becomes, for example, 3
/ 4, the remaining inverters 3 (hereinafter referred to as # 2 to #n inverters) 3 of the respective photovoltaic power generators 1 start current control operation.

That is, when the self-sustaining operation mode is commanded, the control circuit sections 3b of the inverters # 2 to #n operate the current control functions of FIG. 4 according to the respective current type inverter control programs.

Then, the output voltage detecting means 13 outputs a load voltage Vout of, for example, 3/3 of the rated voltage Vc based on the voltage measurement outputs v ₂ ,.
4, a low-level current increase command is generated and output.

Further, the frequency detecting means for digital or analog, which is not shown, the voltage measurement output v _2, ..., the digital waveform analysis vn, the voltage measurement output v _2, ..., a PLL synchronization oscillation or the like based on vn, # The angular frequency ω ₀ of the load voltage Vout based on the output of the first inverter 3 is digitally or analogously detected.

Then, the operation reference signal creating means 14 similar to the creating means 10 makes the output currents I2 to In of the inverters # 2 to #n have the same phase as the output voltage V1 of the inverter 3 of # 1. Based on the frequency ω ₀ , a sinusoidal current control signal | i of amplitude | i | synchronized with the voltage control reference signal
In addition to forming | sin (ω ₀ · t), the amplitude | i | is gradually increased from 0 by the soft start characteristic so that the output currents I2 to In are increased with the set value Iα as an upper limit, for example.

Further, the subtracter 15 calculates an error between the current control reference signal and the current measurement outputs i ₂ ,..., In, and outputs a signal of this error.

An analog switch 16 for operating on / off operation is connected in series to the output terminal of the subtracter 15, and this switch 16 changes, for example, the load voltage Vout to a predetermined value by a binary change of the judgment output of the start-up judgment circuit 17. Turns on when the voltage rises to Vα.

When the analog switch 16 is turned on,
The error signal of the subtractor 15 is supplied to a signal processing means 18 for feedback control similar to that of the signal processing means 12, and this processing means 18 performs signal processing for feedback control on the error signal and drives the inverter for current control. Form a signal.

The inverter drive signal is supplied to the control circuit 3b.
Is supplied to the switching circuit unit 3a from the
a is switched.

By this switching drive, # 2 to #n
Of each of the inverters 3 is operated in a current control in synchronization with the output voltage of the inverter 3 of # 1 to form an AC current source having an angular frequency ω ₀ .

The # 3 inverter 3 outputs the output voltage V
When the output current I1 exceeds a predetermined value Iα in accordance with the rise of 1, the output of the output current detection means 8 is inverted to a high level (H) voltage drop command, and the operation reference signal creation means 10 responds to this command by the voltage control command. Reducing the amplitude | v | of the reference signal;
The output voltage V1 is reduced and maintained at the rated voltage Vc.

When the load voltage Vout reaches the rated voltage Vc, the inverters # 2 to #n invert the output of the output voltage detecting means 13 to a high-level current decrease command, and generate an operation reference signal by this command. Means 14 reduces the amplitude | i | of the current control reference signal to reduce the output currents I2 to In.

Therefore, the output voltage V1 of the # 1 inverter 3 is feedback-controlled to the rated voltage Vc by the voltage control operation, and the output currents I2 to In of the remaining # 2 to #n inverters are controlled by the current control operation. Output voltage V1
The feedback control is performed so that the phase is equal to or less than the set value Iα.

By these feedback controls, each photovoltaic power generator 1 is operated in parallel and synchronously to feed the load 7 without exchanging information related to output such as output power and output current between the apparatuses.

At this time, the output power of the photovoltaic power generator 1 of # 1 is represented by P1 + jQ1 (P1 is active power, Q1
Is the reactive power), the output power of the remaining # 2 to #n solar power generation devices 1 is the output voltage I2
2 to Vn (= Vout) and become in-phase, so that the active power becomes P2,..., Pn in FIG.

The load current I _L (= I ₁ + I ₂ +... +
In), the power consumption of the load 7 flowing through is represented by P _L + jQ in FIG.
_L (P _L is the effective power, Q _L is the reactive power) When active power P _L is the effective power P _1, P ₂ of each photovoltaic power generator 1,
..., it is financed by Pn, the reactive power Q _L is covered by the reactive power Q1 of solar power generation apparatus 1 of # 1.

Next, an example of a specific change in the output of each photovoltaic power generator 1 after the start of operation when the load 7 has a power factor of 1 will be described with reference to FIG. In the figure,
, ... it is _{t 0 ~t 1, t 1 ~t} 2 when the time series of the start operation (start) and a t _0, ..., showing each operation period of the time series of t ₁₀ ~t ₁₁ (section).

First, during the operation period immediately after the start,
Only the inverter 3 performs voltage control operation, and its output voltage V1 (= Vout) gradually increases to increase its output current I
It also increases by one.

[0057] Then, the output voltage V1 to t ₁ is set value Vα
, The current control operation of the inverters # 2 to #n is started. During the operation period, the output voltage V1 of the inverter 3 of # 1 further increases and the output of the inverters 3 of # 2 to #n is increased. The currents I2 to In gradually increase from 0.

Next, at t ₂ , the output voltage V 1 becomes the rated voltage V
During the operation period in which the output current I2 -In changes, the inverter 3 of # 1 is operated to maintain the rated voltage Vα, and the inverters 3 of # 2 to #n do not change in the load voltage Vout. Not to be kept.

Next, when the capacity of the load 7 increases during the operation period, the load voltage Vout decreases instantaneously, but this voltage decrease causes the output current I2 of the inverter 3 of # 2 to #n to decrease.
In immediately increases, and the output currents I2 to In reach the set value Iα.
To prevent the load voltage Vout from decreasing.

When the capacity of the load 7 further increases, the output currents I2 to In that have reached the set value Iα do not increase any more. However, based on the decrease in the load voltage Vout, the # 3 inverter 3 reduces the load voltage Vout. increasing the output current I1 to rise, the operating period is compensated shortage of the load current I _L output current I ₁ is increased.

Further, during the operation period, the capacity of the load 7 is kept constant, and each inverter 3 is kept in the output state immediately before.

Next, at the operation period, the load current I _L capacity of the load 7 is reduced is decreased, the output current I1 of # 1 of the inverter 3 in conjunction with this reduction is reduced.

Further, during the operation period in which the capacity of the load 7 is kept constant, each inverter 3 is operated stably without a change in output, as in the operation period.

Next, after the operation period when the capacity of the load 7 gradually decreases and changes, the output current I
₁ further decreases and changes.

Then, after the output current I1 drops to 0,
When the capacity of the load 7 further decreases, the output currents I2 to In of the inverters 3 of # 2 to #n decrease.

When no load occurs, the output current I1
To In become zero, and at this time, the load voltage Vout is maintained at the rated voltage Vc based on the output voltage V1.

Then, during the self-sustaining operation, only the inverter 3 of the photovoltaic power generator 1 of # 1 is operated by voltage control first,
# 2 to #n photovoltaic power generators 1 in synchronization with the output voltage
Are operated in current control, each of the photovoltaic power generators 1 does not exchange information related to output such as output power and output current, and furthermore, does not provide a dedicated sensor or the like for the same, so that Operated synchronously.

In this case, since the inverters 3 of the respective photovoltaic power generators 1 are individually operated, for example, the manufacturers of the respective photovoltaic power generators 1 are different, and the control sequences of the respective inverters 3 are different. Irrespective of this difference, the inverters 3 of the photovoltaic power generators # 2 to #n
Is synchronized with the output voltage of the inverter of the # 1 photovoltaic power generator 1, and each photovoltaic power generator 1 is operated in parallel and synchronously.

The present invention can be similarly applied to a case where a plurality of distributed power sources which are disconnected from the power system and operated independently are other than the photovoltaic power generator. In this case, it is needless to say that a configuration in which various types of distributed power sources are mixed may be employed.

Next, the set voltage Vα for starting the operation of the inverters # 2 to #n and the set value Iα for defining the upper limit of the output currents I1 to In are appropriately set according to the capacity of the load 7. Of course, you can. The reference inverter may be any of inverters # 1 to #n.

[0071]

The present invention has the following effects. Each distributed power source (each photovoltaic power generation device 1) has a power system 5
When the self-sustaining operation is performed after being disconnected from the inverter, the reference inverter (for example, the inverter of the # 1 photovoltaic power generator 1) 3 is voltage-controlled to form an AC voltage source, and the remaining dispersion is delayed from the reference inverter. Power supply inverter (eg # 2
To #n of the photovoltaic power generators 1 are respectively subjected to current control operation to form an AC current source.

At this time, the voltage of the load power supply is determined by the voltage of the reference inverter, and the output currents of the remaining distributed power supply inverters have the same phase as the output voltage of the reference inverter. The distributed power sources can be operated in parallel and synchronously without the need to exchange information related to the output between the distributed power sources in synchronization with the output of the distributed power sources, and communication lines can be laid between the distributed power sources. In addition, it is possible to realize a parallel synchronous operation at the time of self-sustaining operation of a plurality of distributed power sources with an inexpensive configuration.

[Brief description of the drawings]

FIG. 1 is a single-wire system diagram of one embodiment of the present invention.

FIG. 2 is a circuit block diagram illustrating a configuration of each inverter of FIG.

FIG. 3 is a functional block diagram of a part of FIG. 2 during a voltage control operation.

FIG. 4 is a functional block diagram of a part of FIG. 2 at the time of current control operation.

FIG. 5 is a waveform chart showing an example of a change in voltage and current of each unit in FIG.

[Explanation of symbols]

 1 Photovoltaic power generation device as a distributed power source 3 Inverter 5 Power system

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02M 7/48 H01L 31/04 K

Claims (1)

[Claims] When a plurality of distributed power supplies disconnected from a power system are operated independently, one of the distributed power supplies is used as a reference inverter, and the reference inverter is operated under voltage control. An AC voltage source is formed, and after the output voltage of the reference inverter is generated, the remaining distributed power supply inverters are respectively subjected to current control operation in synchronization with the output voltage of the reference inverter. An operation control method for a distributed power supply facility, wherein an AC current source synchronized with an AC voltage source is formed and each distributed power supply is operated in parallel and synchronously.