JPH0624895Y2 - Grid interconnection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a power system having a voltage type inverter circuit such as an active filter, a reactive power compensator, a solar cell generator, a fuel cell generator, etc. The present invention relates to a grid interconnection device that is used in a state in which it is interconnected with. In particular, the present invention relates to control of active power and reactive power in a voltage-type inverter circuit that transmits and receives active power and reactive power, harmonic voltage / current, etc. by linking with a commercial power system.

[Conventional technology]

FIG. 2 is a circuit diagram showing a configuration of a conventional system interconnection device. The system interconnection device of FIG. 2 connects the AC side terminal of the voltage type inverter circuit 3 to the power system 1 via an interconnection induction device, for example, an interconnection reactor (including an interconnection transformer) 2. Then, for example, a DC capacitor (battery in the case of a power generator) 4 is connected to the DC side terminal of the voltage type inverter circuit 3.
Are connected. In this case, the voltage of the power system 1 is s, the impedance of the interconnection reactor 2 is jXs, and the voltage of the AC side terminal of the voltage type inverter circuit 3 is ₁
The current flowing from the voltage type inverter circuit 3 into the power system 1 through the interconnection reactor 2 is ₁ .

Then, this grid interconnection device transfers active power P and reactive power Q between the power grid 1 and the voltage-type inverter circuit 3 via the grid reactor 2.

In this case, the active power P and the reactive power Q sent from the voltage type inverter circuit 3 to the power system 1 are derived as follows.

It is assumed that the voltage _{1 at} the AC side terminal of the voltage type inverter circuit 3 is represented by, for example, ₁ = ks (cosφ + jsinφ) (1). However, k is the amplitude (≈1), and φ is the phase difference (10 degrees or less) between the voltage s and the voltage ₁ .

In this case, the current ₁ flowing from the voltage type inverter circuit 3 to the power system 1 is represented by the following equation.

Now, assuming that the phase difference φ is small and sin φ≈φ and cos φ≈1, Becomes Therefore, the active power P and the reactive power Q sent from the voltage type inverter circuit 3 to the power system 1 are
Each Becomes

In order to control the active power P and the reactive power Q, since the phase difference φ is small and the change in cosφ is small, the active power P can be controlled by changing the phase difference φ, and the reactive power Q changes the amplitude k. It can be controlled by changing it.

FIG. 3 shows the voltage of the control circuit of the voltage type inverter circuit 3 for adjusting the active power P and the reactive power Q sent from the voltage type inverter circuit 3 to the power system 1 by changing the phase difference φ and the amplitude k. Type inverter circuit 3
2 shows a reference signal generation circuit 12 for generating a reference signal that determines ₁ to be output to the AC side terminal from the.

As shown in FIG. 3, the reference signal generating circuit 12 outputs a system voltage detection signal Vs ′ obtained as a secondary output of an instrument transformer, for example, to a phase synchronization circuit (PLL circuit) 5
To the phase θ of the system voltage detection signal Vs'.
_s is detected.

On the other hand, in the active power control system 6, for example, in the active filter, the reactive power compensator, etc., the DC capacitor 4 is used.
The voltage between both ends of is detected and the phase φ'according to the detected voltage is output. Then, the adder 7 adds the phase θ _s output from the phase synchronization circuit 5 and the phase difference φ output from the active power control system 6.

The ROM 8 stores the waveform data of the sine wave for each fixed phase, and sequentially reads the waveform data of the sine wave (amplitude is 1 pu) according to the clock signal, and the phase of the waveform data of the sine wave to be read is added. It depends on the output of the container 7. Since the digital-analog converter 9 converts the waveform data output from the ROM 8 into an analog signal,
The digital / analog converter 9 outputs a sine wave signal having the same frequency as the system voltage detection signal Vs 'and an amplitude of 1 pu and a phase difference φ with respect to the system voltage detection signal Vs'.

In the reactive power control system 10, for example, in the reactive power compensator, the reactive power supplied from the power system 1 to the load (not shown) is detected, and the value of the amplitude k corresponding to the detected reactive power of the load is output. To do. Then, in the multiplier 11, the sine wave signal having an amplitude of 1 pu output from the digital-analog converter 9 is multiplied by the value k, and the multiplier 11
Output becomes the reference signal V _R1 .

Then, this reference signal V _R1 is converted into a square wave signal in a pulse width modulation circuit (not shown), and each switching element of the voltage type inverter circuit 3 is on / off controlled according to the obtained square wave signal. The active power P and the reactive power Q are sent from the voltage type inverter circuit 3 to the power system 1.

As a result, in this system interconnection device, for example, the active power P is controlled so that the voltage of the DC capacitor 4 is constant, and the reactive power Q is controlled so as to cancel the reactive power consumed by the load. Will be.

[Problems to be solved by the device]

However, in this system interconnection device, among the control circuits that control the voltage-type inverter circuit 3, the reference-signal generation circuit that generates the reference signal V _R1 that determines the voltage ₁ to be output from the voltage-type inverter circuit 3 to the AC side terminal. 12 is composed of a hybrid circuit of an analog circuit and a digital circuit, and there is a problem that the structure is complicated and expensive.

Further, since the reference signal generating circuit 12 is configured to process the system voltage detection signal Vs ′ obtained as the secondary output of the instrument transformer, for example, in series to generate the reference signal V _R1 , somewhere 1 If the location becomes abnormal, the reference signal V _R1 becomes an abnormal value. For example, when the reference signal V _R1 becomes 0, the voltage _{1 at} the AC side terminal of the voltage type inverter circuit 3 becomes 0. The state where the voltage ₁ of the voltage type inverter circuit 3 is 0 is equivalent to a short circuit of the power system 1, and
Therefore, an excessive short-circuit current flows through the interconnection reactor 2 and the voltage-type inverter circuit 3. That is,
The failure of the circuit that creates the reference signal V _R1 led to a major accident in the power system 1, and the reliability as a system interconnection device was low.

Therefore, an object of the present invention is to simplify the configuration of a reference signal generation circuit that generates a reference signal that determines the voltage of the AC side terminal of the voltage type inverter circuit, reduce cost, and improve reliability. It is to provide a system interconnection device capable of performing the above.

[Means for Solving the Problems]

The grid interconnection device of the present invention connects a voltage type inverter circuit to an electric power system through an interconnection induction device and sends at least one of active power and reactive power from the voltage type inverter circuit to the power system. ing. Then, for this purpose, a reference signal is created by the reference signal creating circuit, and the voltage of the AC side terminal of the voltage type inverter circuit is determined by this reference signal.

In this case, the reference signal creation circuit is a signal obtained by phase-shifting the reactive voltage control signal obtained by multiplying the system voltage detection signal by the output signal of the reactive power control system and the system voltage detection signal by π / 2. Is added to at least one of the active power control signals obtained by multiplying the output signal of the active power control system by using the circuit as a reference signal.

[Action]

According to the configuration of the present invention, the reference signal generating circuit generates the reactive power control signal obtained by multiplying the system voltage detection signal by the output signal of the reactive power control system and the system voltage detection signal by π / 2. Since the reference signal is obtained by adding at least one of the active power control signals obtained by multiplying the phase-shifted signal by the output signal of the active power control system, the reference signal can be created only by analog processing.

Further, even if at least one of the reactive power control signal and the active power control signal becomes zero due to some abnormality, at least the system voltage detection signal is output as the reference signal, and the voltage at the AC side terminal of the voltage type inverter circuit is at least the power. It can be kept at the same voltage as the grid voltage of the grid.

〔Example〕

An embodiment of this invention will be described with reference to FIG. In this system interconnection device, the connection relationship among the power system 1, the interconnection reactor 2, the voltage type inverter circuit 3, and the DC capacitor 4 is the same as that of the conventional example shown in FIG. The conventional example is
The reference signal generation circuit of the control circuit for controlling the voltage type inverter circuit 3 is different. The process after creating the reference signal is the same as the conventional example.

FIG. 1 is a block diagram showing the configuration of the reference signal generating circuit 27 in one embodiment of the present invention. This first
As shown in FIG. 1, the reference signal generation circuit 27 in the figure includes a reactive power control system 21 and a voltage type inverter that generate a coefficient k ₁ corresponding to the reactive power Q to be sent from the voltage type inverter circuit 3 to the power system 1. Circuit 3 to power grid 1
An active power control system 22 for generating a coefficient k ₂ corresponding to the active power P to be sent to, and a multiplier 24 for multiplying the system voltage detection signal Vs ′ obtained as a secondary output of an instrument transformer by k ₁ for example. The phase of the system voltage detection signal Vs ′ is π /
Π / 2 phase shift circuit 23 that shifts two phases, and π / 2 phase shift circuit 23
25 which multiplies the output of 1 by a coefficient k ₂ , a system voltage detection signal Vs ′, and a reactive power detection signal V _Q and an active power detection signal V _P output from the multipliers 24 and 25, respectively, and a reference signal. And a multiplier 26 for V _R2 .

In this case, in the reactive power control system 21, for example, in the reactive power compensator, the reactive power supplied from the power system 1 to the load (not shown) is detected, and the coefficient k ₁ corresponding to the detected reactive power of the load is detected. The value of is output. In the case of an active filter that only performs harmonic compensation, the reactive power Q is generally not sent from the voltage type inverter circuit 3 to the power system 1, so the reactive power sent from the voltage type inverter circuit 3 to the power system 1 is not. In order to make Q zero, the active power control system 22 detects the reactive power Q of the voltage type inverter circuit 3 itself and outputs the value of the coefficient k ₁ according to it.

Further, in the active power control system 22, for example, in an active filter, a reactive power compensating device, etc., the voltage across the DC capacitor 4 is detected and a coefficient k ₂ corresponding to this detected voltage is detected.
Is output. In the case of the power generator, the voltage of the battery is detected and the value of the coefficient k ₂ corresponding to the voltage value is output.

Then, the reference signal V _R2 is similar to the conventional example,
The pulse width modulation circuit (not shown) converts into a square wave signal, and each switching element of the voltage-type inverter circuit 3 is ON / OFF controlled according to the obtained square wave signal, and the active power P and the reactive power Q are controlled. It is sent from the voltage type inverter circuit 3 to the power system 1.

As a result, in this system interconnection device, for example, in the case of a reactive power compensator, the active power P is controlled so that the voltage of the DC capacitor 4 is constant, and the reactive power consumed by the load is canceled. The reactive power Q will be controlled.

The coefficients k ₁ and k ₂ are determined based on the following formula.

Since Equation (1) is φ≈0, it can be approximated as ₁ = ks (1 + jφ) (6). Now, the amplitude k can be expressed as k = 1 + k '... (7). However, k'≈0.

Substituting the equation (7) into the equation (6), we have: ₁ = (1 + k '). S (1 + j.phi.) = S + k's + jk.phi.s (8)

In the reference signal generating circuit 27 shown in FIG. 1, the first term of the equation (8) is the system voltage detection signal Vs' directly added by the adder 2
6, the second term of the equation (8) corresponds to the path for reactive power control in which the system voltage detection signal Vs ′ is input to the adder 26 through the multiplier 24, and The third term of the equation (8) is that the system voltage detection signal Vs' is π / 2 phase shift circuit 23.
And a path for active power control input to the adder 26 through the multiplier 25. Then, the coefficient k ′ in the equation (8) corresponds to the coefficient k ₁ , and kφ in the equation (8) corresponds to the coefficient k ₂ .

It should be noted that when the power system 1 and the voltage-type inverter circuit 3 are connected via the interconnection reactor 2, the difference voltage ₁ -s is applied across the interconnection reactor 2 as described above. However, the current ₁ flowing through the interconnection reactor 2 is delayed by π / 2 with respect to the difference voltage ₁ -s.

In the grid interconnection device of this embodiment, the reference signal generation circuit 27 multiplies the grid voltage detection signal Vs ′ by the multiplier 24 by the coefficient k ₁ output from the reactive power control system 21, and the grid voltage detection signal Vs ′. Is multiplied by a signal obtained by phase shifting by π / 2 in a π / 2 phase shift circuit 23, and is multiplied by a coefficient k ₂ output from the active power control system 22 in a multiplier 25, and multiplied by a system voltage detection signal Vs ′ in an adder 26. The reactive power control signal output from the adder 24 and the active power control signal output from the multiplier 25 are added, and the output signal of the adder 26 is used as a reference signal. A reference signal can be created only by analog processing without using a circuit, and the reference signal creation circuit 27 can be configured by using a small number of operational amplifiers, which simplifies the circuit configuration. It is possible to achieve low cost.

Further, at least one of the reactive power control signal output from the multiplier 24 and the active power control signal output from the multiplier 25 is zero due to some abnormality such as an abnormality of the reactive power control system 21 or the active power control system 22. Even if
The system voltage detection signal Vs ′ is used as the reference signal V _R2.
Is output at least, and the voltage ₁ at the AC side terminal of the voltage-type inverter circuit 3 can be held at least at the same voltage as the system voltage s of the power system 2, which may lead to a major accident in the power system 1 such as a short circuit. Absent. In addition, the path for directly inputting the system voltage detection signal Vs' to the adder 26 is formed only by a line, and there is almost no abnormality in this path, and the reliability as a system interconnection device can be improved. it can.

It should be noted that in the above-described embodiment, both the active power P and the reactive power Q sent from the voltage type inverter circuit 3 to the power system 1 are controlled, and the reference signal generation circuit 2 is used.
7 also adds both the reactive power control signal and the active power control signal to the system voltage detection signal Vs', but if reactive power control is not required, the reactive power control system 2
1 and multiplier 24 are not needed. Further, if control of active power is unnecessary, the π / 2 phase shift circuit 23, active power control system 22 and multiplier 25 are not required.

[Effect of device]

According to the grid interconnection device of the present invention, a reference voltage creation circuit that creates a reference voltage that determines the voltage of the AC side terminal of the voltage-type inverter circuit that is connected to the power grid,
The grid voltage detection signal is multiplied by the reactive power control system output signal and the reactive power control signal and the grid voltage detection signal is shifted by π / 2 to the active power control system output signal. Since at least one of the active power control signals is added as the reference signal, the reference signal can be created only by analog processing, the circuit configuration can be simplified, and the cost can be reduced. it can.

Further, even if at least one of the reactive power control signal and the active power control signal becomes zero due to some abnormality, at least the system voltage detection signal is output as the reference signal, and the voltage at the AC side terminal of the voltage type inverter circuit is at least the power. It can be maintained at the same voltage as the system voltage, and will not lead to a major accident in the power system such as a short circuit. Therefore, the reliability of the system interconnection device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a reference signal generating circuit in a system interconnection device according to an embodiment of the present invention, and FIG.
The figure is a block diagram showing the overall configuration of a conventional system interconnection device.
FIG. 3 is a block diagram showing the configuration of a conventional example of the reference signal generating circuit in the system interconnection device. DESCRIPTION OF SYMBOLS 1 ... Electric power system, 2 ... Interconnection reactor, 3 ... Voltage type inverter circuit, 21 ... Reactive power control system, 22 ... Active power control system, 23 ... π / 2 phase shift circuit, 24, 25 ... Multiplier, 26
... Adder, 27 ... Reference signal generation circuit

Claims (1)

[Scope of utility model registration request] 1. A voltage type inverter circuit connected to a power system via an interconnection induction device, and a reference signal generating circuit for generating a reference signal for determining a voltage of an AC side terminal of the voltage type inverter circuit. The reference signal generating circuit is configured to phase shift the reactive power control signal obtained by multiplying the system voltage detection signal by the output signal of the reactive power control system and the system voltage detection signal with respect to the system voltage detection signal by π / 2. A grid interconnection device configured by a circuit that adds at least one of active power control signals obtained by multiplying a signal by an output signal of an active power control system to obtain a reference signal.