JPH1118304A - Interconnected inverter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an excellent interconnected inverter capable of stably interconnecting both an engine generator having a large voltage fluctuation range and a commercial system. An interconnection inverter (A) includes an inverter (7), a voltage synchronization signal generation circuit (13), a feedback circuit (16), a feedforward circuit (23), and inverter driving means (19, 20), an engine generator start completion detection circuit (24) and a commercial power supply. The system includes a system restoration detection circuit 25 and selectively supplies power to the AC load 4 by selectively linking with either the commercial system 2 or the engine generator 3. Feed forward circuit 2
When the signal _SEG of the engine generator start completion detecting circuit 24 is “1”, the time constant switching unit 22 of No. 3 changes the time constant T ′ of the primary delay filter 21 to the time constant T for the engine generator.
_{2 and} when the signal S _{CS of} the commercial power restoration detection circuit 25 is “1”, the time constant T of the first-order lag filter 21
The 'switching to constant T ₁ time of the commercial system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interconnection inverter for interconnecting a DC power supply such as a fuel cell or a solar cell with a commercial system or an engine generator.

[0002]

2. Description of the Related Art In recent years, it has been recommended to develop a system for supplying power from a plurality of types of power sources including a commercial system in order to secure a stable power supply even in the event of a commercial system power failure. Above all, a system that connects a DC power supply such as a fuel cell or a solar cell to a commercial system or an engine generator is promising, and in such a system,
Convert DC power output from DC power supply to AC power,
It is necessary that the AC power follow the voltage of the commercial system or the engine generator and be connected stably.

FIG. 4 is a block diagram showing a conventional interconnection inverter used in a system for interconnecting a DC power supply and a commercial system or an engine generator as described above.
As shown in FIG. 4, the interconnection inverter B is configured to interconnect the DC power supply 1 and the commercial system 2 or the engine generator 3 to supply power to the AC load 4. Here, 5 is a connection switch for a commercial system, and 6 is a connection switch for an engine generator. Hereinafter, details of the interconnection inverter B will be described.

First, the interconnection inverter B has an inverter 7 for converting DC power output from the DC power supply 1 into AC power and an interconnection reactor 8, and an inverter output current detector for detecting the output current of the inverter 7. 9, a system voltage detector 10 for detecting an output voltage of one of the commercial system 2 and the engine generator 3 as a system voltage.
The interconnection inverter B also includes a voltage synchronous oscillator 11 and a multiplier 12, a voltage synchronous signal generating circuit 13 for obtaining a current command value corresponding to the system voltage, a subtractor 14, and a current controller (AC
R) 15 and a feedback circuit 16 for generating a current command signal for converging the difference between the current command value and the inverter output current. The interconnection inverter B is
A feedforward circuit 18 that passes a system voltage through a first-order lag filter 17 to generate a voltage filter signal, an adder 19 that adds a current command signal and a voltage filter signal, and a switch drive signal corresponding to the addition result of the adder It has a PWM circuit 20 to generate.

The operation of the conventional interconnection inverter B having the above configuration is as follows. The voltage synchronization signal generation circuit 13 uses the voltage synchronization oscillator 11 to output the system voltage V _L according to the system voltage V _L detected by the system voltage detector 10.
A reference sine wave SIN having a sine waveform having an amplitude of 1 and having the same frequency and phase as the _L fundamental wave component is generated. Subsequently, the preset amplitude command value K _P and the reference sine wave SIN by multiplying by the multiplier 12 to obtain a current command value I _r of the fundamental wave component of the inverter output.

[0006] Feedback circuit 16 includes a voltage synchronizing signal generating circuit current command value obtained by the 13 I _r and the inverter output current detected by the detector 9 the inverter output current I _INV
Is subtracted by the subtractor 14, and the power command signal IACR is generated by controlling the _ACR 15 so that the result of the subtraction converges. Also, feed forward circuit 1
8 passes the system voltage _VL through a first-order lag filter 17 having a preset time constant T to generate a voltage filter signal _VLF .

[0007] The adder 19 is connected to the power command signal _IACR from the feedback circuit 16 and the feedforward circuit 18.
By adding the voltage filter signal V _LF from, obtaining a voltage command value V _r. Subsequently, PWM circuit 20, the switch drive signal PW having a pulse width which the voltage command value V _r and polarity are equal, and proportional to the amplitude of the absolute value of the voltage command value V _r
Generate M.

[0008] Then, the inverter 7, the input DC voltage V _DC output from the DC power supply 1 to operate the main switch according to the switch driving signal PWM from the PWM circuit 20, the waveform of the similar to the voltage command value V _r And generates an inverter output voltage V _INV having

With the above operation, the inverter output current I
It is possible to make _INV a sine wave synchronized with the fundamental wave of the system voltage _VL. By appropriately setting the amplitude command value K _P to be multiplied by the reference sine wave SIN, the output amount of the DC power supply 1 can be reduced. An appropriate constant AC power can be supplied from the inverter 7. Also, even when the system voltage _VL fluctuates instantaneously, by appropriately setting the time constant T of the first-order lag filter 17 of the feedforward circuit 18,
It is possible to make the inverter output voltage V _INV follow the system voltage V _L , thereby preventing the inverter 7 from outputting an overcurrent.

[0010]

By the way, in the conventional interconnection inverter as described above, the time constant of the primary delay filter 17 of the feedforward circuit 18 is
Since the suitable time constant differs between the case where the system is connected to the commercial system and the case where the system is connected to the engine generator, it is particularly difficult to connect both the engine generator and the commercial system with a large voltage fluctuation range. There's a problem.

Hereinafter, this problem will be described in more detail with reference to FIGS. Here, FIG. 5 is a graph showing the relationship between the time constant T of the feedforward circuit 18 and the harmonic component of the inverter output current I _{IN V.}
Is a graph showing the relationship between the time constant T of the feedforward circuit 18 and the allowable fluctuation range of the system voltage _VL .

First, as shown in FIG. 5, when the time constant T of the feedforward circuit 18 is reduced, the controllability of the inverter output current I _INV is reduced, and the inverter output current I _INV is reduced.
The harmonic component of _INV increases. In particular, when connecting to a commercial system, the inverter 7
The time constant T
Care must be taken not to make the value too small.

On the other hand, as shown in FIG. 6, when the time constant T of the feedforward circuit 18 is increased, the system voltage V _L
Of the inverter output voltage V _{INV with} respect to the instantaneous fluctuation of the power supply voltage V _INV decreases, and the allowable fluctuation width of the system voltage _VL decreases. Generally, the voltage fluctuation width of the engine generator is larger than that of the commercial system, and therefore, it is desirable to make the time constant T smaller when connecting to the engine generator than when connecting to the commercial system. That is, it is desirable to set the time constant T to be large when connecting to a commercial system, and to set the time constant T to be small when connecting to an engine generator.

In view of the above-described restrictions on the time constant, in order to enable interconnection with at least the commercial system, the minimum time constant T such that the harmonic current output from the inverter 7 satisfies the system interconnection guidelines. Must be set.
However, when the time constant T is set in this manner, it becomes impossible to connect to the engine generator that fluctuates beyond the allowable fluctuation range of the system voltage determined by the time constant T. That is, it is difficult to interconnect both the engine generator having a large voltage fluctuation range and the commercial system.

The present invention has been proposed to solve the problems of the prior art as described above.
An object of the present invention is to provide an excellent interconnection inverter capable of stably interconnecting both an engine generator having a large voltage fluctuation range and a commercial system.

[0016]

The above objects can be attained by employing the novel means according to the present invention. That is, the interconnected inverter of the present invention first includes an inverter, a voltage synchronization signal generation circuit, a feedback circuit, a feedforward circuit, and inverter driving means, and is selectively interconnected with either the commercial system or the engine generator. Interconnected inverter that supplies power to the AC load. The inverter converts DC power output from the DC power supply into AC power. Further, the voltage synchronization signal generation circuit generates a current command value synchronized with a fundamental component of the output voltage of one of the commercial system and the engine generator. Then, the feedback circuit generates a current command signal for converging a deviation between the current command value and the inverter output current, and the feedforward circuit generates a voltage filter signal by passing the output voltage through a first-order lag filter. I do. Further, the inverter driving means drives the inverter using the current command signal and the voltage filter signal.

In addition to the above configuration, the interconnection inverter according to the first aspect of the present invention detects an engine generator activation completion detection circuit for detecting the completion of activation of the engine generator, and detects a power recovery of the commercial system. A commercial power recovery detection circuit is provided, and the feedforward circuit is configured as follows. That is, the feedforward circuit is configured to switch the time constant of the first-order lag filter in accordance with the output signal of the engine generator start completion detection circuit and the output signal of the commercial power restoration detection circuit.

According to the first aspect of the present invention having the above configuration, the time constant of the first-order lag filter of the feedforward circuit is set to a time constant suitable for the commercial system when interconnected with the commercial system. In the case of setting and linking with an engine generator, the time constant can be switched to a time constant suitable for the engine generator. Therefore, even when interconnecting with an engine generator having a large voltage fluctuation range, the allowable fluctuation range of the system voltage can be increased by using a time constant suitable for such an engine generator. And stable connection with both commercial and commercial systems.

According to a second aspect of the present invention, in the first aspect of the present invention, the feedforward circuit is further configured as follows. In other words, the feedforward circuit sets the time constant when the harmonic component of the current output from the inverter reaches the value specified in the system interconnection guideline as the time constant for the commercial system, and the allowable fluctuation range of the system voltage indicates the engine power generation. The time constant in the case of the voltage fluctuation width of the machine is set as the time constant for the engine generator, and the time constant of the first-order lag filter is switched.

In the invention having the above-described configuration, the time constants for the commercial system and the engine generator are appropriately set as the time constants of the first-order lag filter of the feedforward circuit. Therefore, it is possible to stably connect both the commercial system and the engine generator. In particular, when connecting to an engine generator having a large voltage fluctuation range, the time constant can be switched to match the voltage fluctuation range of the engine generator, so that it is possible to stably connect to the engine generator. .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[1. Configuration] FIG. 1 is a block diagram showing one embodiment of an interconnection inverter to which the present invention is applied. This figure 1
As shown in FIG. 4, the basic configuration of the present embodiment is the same as that of the conventional technique shown in FIG. 4, and therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted.

That is, as shown in FIG. 1, the interconnection inverter A includes an inverter 7, an interconnection reactor 8, an inverter output current detector 9, and an inverter 7, similarly to the prior art shown in FIG.
A voltage synchronous oscillator 1 having a system voltage detector 10
It has a voltage synchronization signal generation circuit 13 including 1 and a multiplier 12, a feedback circuit 16 including a subtractor 14 and a current controller (ACR) 15, an adder 19, and a PWM circuit 20. Here, the adder 19 and the PWM circuit 20 correspond to the inverter driving means of the present invention.

In the present embodiment, the time constant T 'is replaced with the time constant T' for the commercial system according to the present invention, instead of the feedforward circuit 18 including the first-order lag filter 17 in which the conventional time constant T is fixedly set. A feedforward circuit 23 including a first-order lag filter 21 and a time constant switching unit 22 that can be switched between the time constant T _{1 of FIG. 1} and the time constant T ₂ for the engine generator is provided. Further, an engine generator activation completion detection circuit 24 for detecting the completion of activation of the engine generator 3 and a commercial system restoration detection circuit 25 for detecting restoration of the commercial system 2 are provided.

FIG. 2 shows a feedforward circuit 2
3, the time constant T ₁ for the commercial system and the time constant T ₂ for the engine generator, and the inverter output current I ′ _INV
Is a graph showing the relationship between the allowable variation width of the harmonic component and the system voltage _V'L of. As shown in FIG. 2, in the present embodiment, the time constant when the harmonic component of the inverter output current I ′ _INV output from the inverter 7 reaches the specified value of the system interconnection guideline is set to the value for the commercial system. when the constant T _1, is constant T ₂ time constant for the engine generator when when allowable fluctuation range of the system voltage _V'L is the voltage fluctuation width of the engine generator 3.

[2. Operation / Effect] Regarding the operation of the interconnection inverter A of the present embodiment having the above configuration,
Next, description will be made with reference to FIGS. Here, FIG.
5 is a flowchart illustrating an operation procedure of the time constant switching unit 22 of the feedforward circuit 23.

First, the interconnection inverter A normally closes the interconnection switch 5 for the commercial system and opens the interconnection switch 6 for the engine generator to perform the interconnection operation with the commercial system 2. In this state, when the commercial system 2 is out of power, the commercial system interconnection switch 5 is opened and the engine generator 3
Is completed, the connection switch 6 for the engine generator is closed, and the connection to the engine generator 3 is established. Thereafter, when the commercial system 2 is restored, the interconnection switch 6 for the engine generator is opened, the interconnection switch 5 for the commercial system is closed, and the commercial system 2 is interconnected.

[0027] Therefore, usually, constant T'time of the first-order lag filter 21 is set to be constant T ₁ time of the commercial system. This constant T ₁ time of the commercial system, as shown in FIG. 2, the time constant of the time the harmonic component of the current output from the inverter 5 is the specified value of the grid interconnection guidelines.

The engine generator start completion detecting circuit 24 according to the present invention sets the engine generator start completion signal _SEG to 1 when the start of the engine generator 3 is completed after the commercial power system 2 is cut off, and sets the engine power generation to 1. When the machine connection switch 6 is closed, the engine generator start completion signal _{SEG is set} to 0. On the other hand, the commercial power restoration detection circuit 25 according to the present invention includes:
When the commercial system 2 has Fukuden after power failure, and 1 commercial system power recovery signal S _CS, and 0 the commercial system power recovery signal S _CS at the time the interconnection switch 5 for commercial system closed.

The voltage synchronizing signal generating circuit 13 uses the voltage synchronizing oscillator 11 according to the system voltage V ' _L detected by the system voltage detector 10 to make the fundamental wave component of the system voltage V' _L equal in frequency and phase. A reference sine wave SIN ′ having a sine waveform with an amplitude of 1 is generated. Subsequently, the multiplier 12 multiplies the reference sine wave SIN by a preset amplitude command value K ′ _P to obtain a current command value I ′ of a fundamental component of the inverter output.
get _r .

The feedback circuit 16 includes a current command value I ′ _r obtained by the voltage synchronization signal generation circuit 13 and an inverter output current I ′ detected by the inverter output current detector 9.
_{The INV} is compared and subtracted by the subtractor 14, and then the power command signal I'ACR is generated by controlling the _ACR 15 so that the result of the subtraction converges.

In the feedforward circuit 23 according to the present invention, the time constant switching unit 22 switches the time constant T 'of the first-order lag filter 21 in the procedure shown in FIG. That is, as shown in FIG.
Monitors whether the value of the engine generator start completion signal S _EG is S _EG = 1 (step 31), receives the engine generator start completion signal S _EG having a value of “1”, and receives S _EG. =
Once it is determined that the 1 switches the constant T'time of the first-order lag filter 21 to the constant T ₂ when the engine generator (step 32). Next, the time constant switching unit 22 monitors whether or not the value of the commercial system restoration signal S _CS is S _CS = 1 (step 33), and the commercial system restoration signal S having a value of “1”. receive _CS when it is determined that S _CS = 1, 1
Switching the time constant T of the next lag filter 21 'constant T ₁ time for the grid (step 34). The feedforward circuit 23 supplies the system voltage V ′ to the first-order lag filter 21 having the time constant T ₁ or T ₂ switched in this manner.
Through _L , a voltage filter signal V ′ _LF is generated.

The adder 19 receives the power command signal _IACR from the feedback circuit 16 and the feedforward circuit 18
By adding the voltage filter signal _V'LF from, obtaining a voltage command value _V'r. Subsequently, PWM circuit 20, the voltage command value _V'r and polarity are equal, and generating a switch drive signal PWM' having a pulse width proportional to the amplitude of the absolute value of the voltage command value _V'r.

The inverter 7 receives the DC voltage V ′ _DC output from the DC power supply 1 as an input, and
The main switch is operated in accordance with the switch drive signal PWM ′ from the inverter, and an inverter output voltage V ′ _INV having a waveform similar to the voltage command value V ′ _r is generated.

With the above operation, as in the prior art, a constant AC power corresponding to the output amount of the DC power supply 1 is supplied to the inverter 7.
Can be supplied from In particular, in the present embodiment, when connecting to the engine generator 3,
And because it is switched to the constant T ₂ time suitable for small engine generator 3 than when interconnection, it is possible to increase the allowable fluctuation range of the system voltage _V'L than the conventional interconnection inverter B. Therefore, even in the case of connecting to an engine generator having a large voltage fluctuation range, it is possible to stably connect to both the engine generator and the commercial system.

[0035]

As described above, according to the present invention, an engine generator start completion detecting circuit and a commercial system restoration detecting circuit are provided, and a first-order lag filter of a feedforward circuit is provided in accordance with an output signal of these circuits. , It is possible to provide an excellent interconnected inverter capable of stably interconnecting both the engine generator having a large voltage fluctuation range and the commercial system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an interconnection inverter to which the present invention is applied.

FIG. 2 is a time constant T ₁ for a commercial system and a time constant T of an engine generator used in the feedforward circuit 23 of FIG. 1;
₆ is a graph showing a relationship between the harmonic component of the inverter output current I ′ _INV and an allowable fluctuation width of the system voltage V ′ _L.

FIG. 3 is a flowchart illustrating an operation procedure of a time constant switching unit 22 of FIG. 1;

FIG. 4 is a block diagram showing a conventional interconnection inverter.

FIG. 5 is a graph showing a relationship between a time constant T of a feedforward circuit and a harmonic component of an inverter output current I _INV .

FIG. 6 is a graph showing a relationship between a time constant T of a feedforward circuit and an allowable variation width of a system voltage _VL .

[Explanation of symbols]

 A, B: interconnection inverter 1 ... DC power supply 2 ... commercial power system 3 ... engine generator 4 ... AC load 5, 6 ... interconnection switch 7 ... inverter 8 ... interconnection reactor 9 ... inverter output current detector 10 ... system voltage Detector 11 Voltage Synchronous Oscillator 12 Multiplier 13 Voltage Synchronous Signal Generating Circuit 14 Subtractor 15 Current Controller (ACR) 16 Feedback Circuit 17, 21 Primary Delay Filter 18, 23 Feedforward Circuit 19 ... Adder 20 ... PWM circuit 22 ... Time constant switching unit 24 ... Engine generator start completion detection circuit 25 ... Commercial power recovery detection circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshio Naito 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu Factory, Toshiba Corporation (72) Kuniyoshi Tazume 3-9-1-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Within Telegraph and Telephone Co., Ltd. (72) Inventor Chuichi Aoki 3-192-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Within Telegraph and Telephone Co., Ltd. Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. An inverter for converting DC power output from a DC power supply to AC power, and a voltage synchronization for generating a current command value synchronized with a fundamental component of an output voltage of one of a commercial system and an engine generator. A signal generation circuit; a feedback circuit for generating a current command signal for converging a deviation between the current command value and the output current from the inverter; and a voltage filter signal by passing the output voltage through a first-order lag filter. A feed forward circuit, and an inverter driving means for driving the inverter using the current command signal and the voltage filter signal, wherein the AC load is selectively connected to either the commercial system or the engine generator. In the interconnection inverter for supplying power to the engine generator, the engine generator start completion detection detecting the start completion of the engine generator is performed. An output circuit, and a commercial power recovery detection circuit for detecting power recovery of the commercial power system, wherein the feedforward circuit includes an output signal of the engine generator start completion detection circuit and an output signal of the commercial power recovery detection circuit. Wherein the time constant of the first-order lag filter is switched in accordance with the following. 2. The system according to claim 1, wherein the feedforward circuit sets a time constant when a harmonic component of a current output from the inverter reaches a value specified by a system interconnection guideline as a time constant for a commercial system, 2. The time constant of the first-order lag filter according to claim 1, wherein a time constant when the width is a voltage fluctuation width of the engine generator is set as a time constant for the engine generator. Interconnected inverter.