JP2003189474A - System linked power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system linked power converter which has a power conversion unit having a circuit comprising three self-exciting single phase inverters which are delta-connected while the DC circuits of the respective inverters are independent from each other and hence does not need a common resistor R<SB>cc</SB>. <P>SOLUTION: This system linked power converter 1 includes a power converting circuit 5 which supplies a reactive power to a three-phase AC power system having an inductive load, a switching pulse supply unit 2 which generates and supplies switching pulse signals, an apparatus loss detection unit 3 which detects DC output voltages of smoothing capacitors constituting self-exciting single phase inverters in the power converting circuit 5 and calculates the apparatus losses of the respective self-exciting single phase inverters according to the detected output voltages, and a power factor angle control unit 4 which controls the power factor angles of the output voltages of the respective self- exciting single phase inverters in the power converting circuit 5 according to the calculation results. The respective outputs of the power converting circuit 5 are connected to the respective phases of the three-phase AC power system via reactors L1-L3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection power conversion device suitable for compensating reactive power in an AC power system and ensuring power stability of the entire system.

[0002]

2. Description of the Related Art Conventionally, a conventional power conversion circuit 5 having a configuration as shown in FIG. 5 has been used as a system interconnection power conversion device for compensating reactive power of an AC power system using a self-excited single-phase inverter.
Those containing 0 were used. As shown in FIG. 5, the conventional power conversion circuit 50 in the conventional grid-connected power conversion device uses the smoothing capacitor C as a DC voltage source and converts its DC input into AC output by single-phase inverters U1 to U3.
, A transformer Tr, a harmonic filter FL, and a resonance suppression resistor Rcc.

In the single-phase inverters U1 to U3, a DC circuit including a smoothing capacitor C in each inverter is commonly used, and the other portions are connected in parallel, and their outputs are further passed through a transformer Tr. 3
It is configured to be connected to each phase of the phase alternating current power system Vs. Further, as shown in FIG. 5, the smoothing capacitor C has an inductance L with another smoothing capacitor C.
_{Since cc} causes resonance, resonance suppression resistor R _cc suppresses occurrence of resonance.

Further, the three-phase AC power system Vs has an inductive load such as an induction motor, and the conventional system interconnection power conversion device is the conventional power conversion circuit 50 constituting the conversion device. By controlling the output voltage, power is supplied from the grid to compensate for the overall device loss of the self-excited single-phase inverters U1 to U3, the DC voltage of the smoothing capacitor C is controlled to a desired voltage, and each self-excited single-phase inverter is controlled. U1-U
The system is stabilized by making the reactive power output from 3 constant.

Specifically, in the conventional grid-connected power conversion device, a switching pulse signal from a switching pulse supply device (not shown) is input to each of the self-excited single-phase inverters U1 to U3 in the conventional power conversion circuit 50. The switching pulse switches ON / OFF of the switching element forming the inverter to convert the DC input into the AC output. These switching elements do not require a forced commutation circuit, power transistors, GTO (Gate Turn Off) thyristors, I
A self-extinguishing element such as a GBT (Insulated Gate Bipolar Transistor) is used.

That is, each self-excited single-phase inverter U1 to U
As shown in FIG. 5, 3 includes first to fourth switching element sections 51 to 54 in which switching elements and diodes are connected in parallel in opposite directions, and pulse is applied to the switching elements in these switching element sections. A signal is supplied, and one of the combination of the first switching element section 51 and the fourth switching element section 54 and the combination of the second switching element section 52 and the third switching element section 53 is in the ON state. At this time, the DC input is converted to the AC output by switching each switching element so that the other is in the OFF state. This makes 3
By supplying reactive power to the phase alternating current power system Vs, and controlling the power factor angle of the output power of the self-excited single-phase inverters U1 to U3 by a power factor angle control device or the like not shown,
Each equipment loss is supplied from the grid and the inverters U1 to U3
The DC voltage of each smoothing capacitor C is controlled to be the same voltage.

[0007]

[SUMMARY OF THE INVENTION However, the conventional power conversion circuit 50, as described above, in order to suppress the occurrence of resonance due to the inductance L _cc between the smoothing capacitor C in the self-excited single-phase inverters U1~U3 Since the resonance suppression resistor R _cc is required, there is a problem that the efficiency of the entire system is reduced due to the loss due to this R _cc .

Therefore, the present invention has been made by paying attention to the unsolved problem of the conventional technique as described above, in which the circuit of the power converter is provided with three self-excited single-phase inverters, respectively. It is an object of the present invention to provide a system interconnection power conversion device that does not require the resonance suppression resistor R _cc by making the DC circuit of delta connection configuration independent of each other.

[0009]

In order to achieve the above object, a grid interconnection power converter according to a first aspect of the present invention includes a smoothing capacitor as a DC voltage source, and the DC voltage is converted into an AC voltage. Reactive power is provided by including three self-excited single-phase inverters that perform conversion and a reactor that suppresses changes in the output current of the self-excited single-phase inverter, and by performing input and output of electric power with a three-phase AC power system. In the system interconnection power conversion device for compensating the above, the three self-excited single-phase inverters are delta-connected with their respective DC circuit parts independent of each other, and the three self-excited single-phase inverters after the connection are connected. Each output side of the phase inverter is adapted to be connected to each phase of the three-phase AC power system via the reactor, and to eliminate device loss of each of the plurality of single-phase inverters. Outputting device loss detection means and the power factor of the output power of the three self-excited single-phase inverters so that the voltage of the smoothing capacitors in the three self-excited single-phase inverters becomes a desired voltage based on the detection result. And a power factor angle control means for controlling the angles independently of each other.

That is, three self-excited single-phase inverters are delta-connected while the DC circuit parts such as the smoothing capacitors forming the self-excited single-phase inverter are independent from each other, and the output thereof is the output of the self-excited single-phase inverter. It is configured to be connected to a three-phase AC power system via a reactor that suppresses a change in current. Therefore, the DC circuit part is independent, and resonance does not occur between smoothing capacitors in different self-excited single-phase inverters, so there is no need for a resonance suppression resistor that suppresses resonance, which reduces the efficiency of the device itself. Can be prevented.

Further, since each self-excited single-phase inverter is delta-connected, the device loss detection means detects each device loss of the self-excited single-phase inverter, and the power factor angle control means detects the result based on the detection result. By independently controlling the power factor angle of each output power of the self-excited single-phase inverter, it is possible to draw power from the three-phase AC power system that compensates for the device loss of each self-excited single-phase inverter. Therefore, by controlling the output voltage of the self-excited single-phase inverters connected in series so as to be a constant voltage, the self-device can be stably operated.

According to a second aspect of the present invention, there is provided a system interconnection power converter including three self-excited single-phase inverters which include a smoothing capacitor as a DC voltage source and convert the DC voltage into an AC voltage. A transformer for suppressing a change in output current of a self-excited single-phase inverter, and a grid interconnection power conversion device that compensates reactive power by inputting and outputting power to and from a three-phase AC power system. Then, the three self-excited single-phase inverters are delta connected while their respective DC circuit parts are mutually independent, and the three
Each output side of the two self-excited single-phase inverters is connected to each phase of the three-phase AC power system via the transformer, and detects the device loss of each of the plurality of single-phase inverters. And a power factor angle of the output power of the three self-excited single-phase inverters so that the voltage of the smoothing capacitors in the three self-excited single-phase inverters becomes a desired voltage based on the detection result. And a power factor angle control means for controlling each of them independently.

That is, the reactor in the grid interconnection power converter according to the first aspect is changed to a transformer, and it is possible to insulate itself from the three-phase AC power system by the transformer. According to a third aspect of the present invention, in the grid-connected power conversion device according to the first or second aspect, the power loss detecting means detects a DC voltage of the smoothing capacitor, and the detection result is set in advance. The difference between the calculated reference DC voltage and the calculated reference DC voltage is calculated, and the calculation result is output as the device loss.

That is, the device loss detecting means detects the DC voltage of the smoothing capacitor as the device loss, and calculates and outputs the difference between the detected voltage and the preset reference DC voltage.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are diagrams showing an embodiment of a grid interconnection power conversion device according to the present invention. First, the configuration of the grid interconnection power converter according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a grid interconnection power conversion device according to the present invention.
[Fig. 3] is a diagram showing a power conversion circuit in a system interconnection power conversion device. The same parts as those in the conventional example of FIG. 5 are designated by the same reference numerals.

As shown in FIG. 1, the system interconnection power conversion device 1 proceeds to a three-phase AC power system having an inductive load,
Power conversion circuit 5 for supplying reactive power including delay
And a switching pulse signal generation and power conversion circuit 5
The DC voltage of the smoothing capacitor that constitutes the self-excited single-phase inverter in the power conversion circuit 5 and the switching pulse supply unit 2 that supplies the switching pulse signal to the device is detected, and the device loss of each self-excited single-phase inverter is detected based on the voltage. And a power factor angle control unit 4 for controlling the power factor angle of the output power of each self-excited single-phase inverter in the power conversion circuit 5 based on the calculation result. And each output of the power conversion circuit 5 is
For each phase of the three-phase AC power system, a reactor L1 to be described later is provided.
It is connected via L3.

The power conversion circuit 5 includes self-excited single-phase inverters U1 to U3, reactors L1 to L3, and a harmonic filter FL. The self-excited single-phase inverters U1 to U3 are delta-connected as shown in FIG. 2, and their outputs are connected to a three-phase AC power system Vs via reactors L1 to L3 and a harmonic filter FL. Has become.

Here, the reactors L1 to L3 suppress changes in output currents of the delta-connected self-excited single-phase inverters U1 to U3. Further, the harmonic filter FL is a self-excited single-phase inverter U1 to Delta-connected.
It suppresses harmonics contained in each output of U3.
The switching pulse supply unit 2 generates a switching pulse signal having an appropriate pulse width and frequency, and performs switching generated for each switching element of the first to fourth switching element units in each self-excited single-phase inverter U1 to U3. A pulse signal is supplied, and one of a combination of the first switching element section 51 and the fourth switching element section 54 and a combination of the second switching element section 52 and the third switching element section 53 is provided. When in the on state, the other is supplied with a switching pulse signal so that the other is in the off state, and the direct current voltage is converted into an alternating current voltage.

The device loss detector 3 detects the DC voltage of the smoothing capacitor C of each self-excited single-phase inverter U1 to U3 in the power conversion circuit 5, and detects the detected DC voltage and a preset reference DC voltage Vr. And the difference between
The calculation result is output to the power factor angle control unit 4 as a device loss. In the present embodiment, the device loss detector 3 detects the DC voltage of the smoothing capacitor C in each of the self-excited single-phase inverters U1 to U3 at a predetermined cycle and calculates the device loss.

Based on the device loss calculated by the device loss detection unit 3, the power factor angle control unit 4 outputs the self-excited single-phase inverters U1 to U3 of the inverters U1 to U3 when the device loss is equal to or more than a certain value. By controlling the power factor angle of each output power, the power for the device loss is controlled by the three-phase AC power system Vs.
Perform processing to pull in. Further, a more specific operation of the grid interconnection power conversion device 1 will be described with reference to FIG. Figure 4
FIG. 4 is a vector diagram showing a loss current of each device loss in each self-excited single-phase inverter and a zero-phase current that is a loss compensation current flowing from a three-phase AC power system.

First, in the system interconnection power converter 1, when the power factor angle controller 4 acquires the device loss detected by the device loss detector 3, the loss is compared with a preset loss value. Then, a determination process for determining whether or not the value is equal to or larger than a certain value is performed. When it is determined that the power consumption is equal to or more than a certain value, the power for compensating for the loss is supplied to the three-phase AC power supply unit V.
In order to obtain from s, the power factor angle of the output power of the target self-excited single-phase inverter is controlled according to the magnitude of the device loss.

At this time, each self-excited single-phase inverter U1
The device loss generated in U3 is as shown in FIG.
Since the magnitudes are different from each other, the power factor angle control unit 3 supplies each loss from the three-phase AC power system Vs, so that the self-excited single-phase inverters U1 to U3 are provided according to the magnitude of the loss.
Will control the power factor angle of each output power.

Therefore, the self-excited single-phase inverters U1 to U3
The power factor angle of the output power of 1 is controlled to different angles, respectively, and different powers are drawn from the respective phases of the three-phase AC power system Vs to the system interconnection power conversion device 1 side. As a result, the three-phase AC power system Vs
The value obtained by adding the current values of the respective phases does not become zero, and the same system Vs is in an unbalanced state. In order to allow the zero-phase current to flow, each of the self-excited single-phase inverters U1 to U3 has a delta connection configuration.

As described above, each self-excited single-phase inverter is delta-connected while the DC circuit parts such as the smoothing capacitors constituting the self-excited single-phase inverters U1 to U3 are independent, and the output thereof is the same as that of the self-excited single-phase inverter. Since it is connected to the three-phase AC power system via a reactor that suppresses changes in output current, resonance does not occur between the smoothing capacitors,
A resonance suppression resistor that suppresses resonance is not required.

Further, since the self-excited single-phase inverter is delta-connected, the zero-phase current can flow even if the device loss of the same inverter is different, and as a result, the three-phase AC power system Vs.
It is possible to supply the device loss compensation power from. In FIG. 3, as a second embodiment of the power conversion circuit, a reactor L1 for connecting the output of the self-excited single-phase inverter in the power conversion circuit 5 to a three-phase AC power supply.
A transformer Tr is shown instead of ~ L3.

The difference from the system interconnection power conversion device 1 is only the transformer Tr part, and the other circuit operations are the same, so description thereof will be omitted. The role of the transformer Tr is 3
This is to insulate the phase AC power system Vs from the second power conversion circuit 6. As described above, in the second power conversion circuit 6, since the transformer Tr is connected to the connection of each self-excited single-phase inverter to the three-phase AC power system Vs, the circuit 6 and the three-phase AC power system Vs are insulated from each other. It is possible.

Here, the device loss detector 3 shown in FIG.
Corresponds to the device loss detection means described in claims 1 to 3, and the power factor angle control section 4 corresponds to the power factor angle control means described in claims 1 and 2. In the above-described embodiment, the power factor angle control unit 4 controls the power factor angle of the output power of each self-excited single-phase inverter to supply power from the three-phase AC power system Vs and correct the device loss. To do.

[0028]

As described above, according to the system interconnection power conversion device of the present invention, since each self-excited single-phase inverter is delta-connected, the device loss detection means causes the self-excited single-phase inverter to operate. The device loss of each self-excited single-phase inverter is detected by detecting each device loss and independently controlling the power factor angle of each output power of the self-excited single-phase inverter based on the detection result by the power factor angle control means. It is possible to draw power for compensating for the power from the three-phase AC power system. Therefore, the DC circuit part can be made independent, and resonance does not occur between the smoothing capacitors in different self-excited single-phase inverters, so a resonance suppression resistor that suppresses resonance is not required. It is possible to prevent the decrease.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a grid interconnection power conversion device according to the present invention.

FIG. 2 is a diagram showing a power conversion circuit in a system interconnection power conversion device.

FIG. 3 is a diagram showing a second embodiment of a system interconnection power conversion device.

FIG. 4 is a vector diagram showing a loss current of each device loss in each self-excited single-phase inverter and a zero-phase current which is a loss compensation current flowing from a three-phase AC power system.

FIG. 5 is a diagram showing a conventional power conversion circuit 50 in a conventional grid-connected power conversion device.

[Explanation of symbols]

1 grid interconnection power converter 2 Switching pulse supply unit 3 Device loss detector 4 Power factor angle control unit 5 Power conversion circuit 6 Second power conversion circuit 50 Conventional Power Converter Circuit 51-54 1st-4th switching element parts L1 to L3 reactor FL harmonic filter Tr transformer Vs 3-phase AC power system

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naoya Eguchi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 5G066 FA01 FB13 FC01 FC11                 5H007 CA01 CB05 CC05 CC09 EA02                 5H420 BB16 CC05 DD03 EA10 EA20                       EA45 EA47 EB09 EB39

Claims (3)

[Claims] 1. A self-excited single-phase inverter that includes a smoothing capacitor as a DC voltage source and converts the DC voltage into an AC voltage, and a reactor that suppresses a change in output current of the self-excited single-phase inverter. A system interconnection power conversion device comprising: three-phase AC single-phase inverters for compensating for reactive power by inputting and outputting electric power to and from a three-phase AC power system. While connecting the parts independently from each other by delta connection,
The respective output sides of the three self-excited single-phase inverters after connection are configured to be connected to the respective phases of the three-phase AC power system via the reactor, and the output terminals of the plurality of single-phase inverters are connected. Device loss detecting means for detecting each device loss, and the above-mentioned 3 based on the detection result.
Power factor angle control means for independently controlling the power factor angles of the output powers of the three self-excited single-phase inverters so that the voltage of the smoothing capacitors in the two self-excited single-phase inverters becomes a desired voltage. A grid interconnection power conversion device comprising: 2. A self-excited single-phase inverter that includes a smoothing capacitor as a DC voltage source and converts the DC voltage into an AC voltage, and a transformer that suppresses a change in output current of the self-excited single-phase inverter. A system interconnection power conversion device comprising: three-phase AC single-phase inverters for compensating for reactive power by inputting and outputting electric power to and from a three-phase AC power system. While connecting the parts independently from each other by delta connection,
The output side of each of the three self-excited single-phase inverters after connection is adapted to be connected to each phase of the three-phase AC power system via the transformer, and each of the plurality of single-phase inverters is connected. Device loss detecting means for detecting the device loss of No. 3, and the above-mentioned 3 based on the detection result.
Power factor angle control means for independently controlling the power factor angles of the output powers of the three self-excited single-phase inverters so that the voltage of the smoothing capacitors in the two self-excited single-phase inverters becomes a desired voltage. A grid interconnection power conversion device comprising: 3. The power loss detecting means detects a DC voltage of the smoothing capacitor, calculates a difference between the detection result and a preset reference DC voltage, and outputs the calculation result as the device loss. The grid-connected power conversion device according to claim 1 or 2, characterized in that.