JP2019004657A - Single-phase three-wire inverter and voltage compensation device - Google Patents

Abstract

To provide a single-phase three-wire inverter which reduces distortion of an output voltage by controlling a voltage between output lines by providing a phase difference between carriers of phases of the inverter on which PWM control is performed, and a voltage compensation device.SOLUTION: A single-phase three-wire inverter comprises: an inverter part 200 in which a DC power source 201 is connected between DC input terminals of an inverter bridge 202; and a PWM control part 3 which makes an output voltage command of an N phase into zero, varies output voltage commands of an U phase and a V phase and controls output voltages between output lines between U and N phases and between V and N phases to predetermined values in order to generate drive signals for switching elements of the phases by comparing the phase voltage commands with a carrier. In the single-phase three-wire inverter, the PWM control part 3 provides a phase difference between a carrier with respect to the N phase and a carrier with respect to the U phase and the V phase by a delay circuit 6 in such a manner that a voltage waveform between output lines becomes a dipolar modulation waveform during a period in which the output voltage commands of the U phase and the V phase are small.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a single-phase three-wire inverter controlled by PWM (pulse width modulation) and a voltage compensator that compensates for fluctuations in system voltage by the single-phase three-wire inverter.

FIG. 3 shows a conventional technique of a single-phase three-wire inverter that is PWM-controlled, and is described in, for example, Patent Document 1.
In FIG. 3, the inverter part 200 is comprised by the DC power supply 201 and the inverter bridge 202 connected between the both poles. The inverter bridge 202 includes semiconductor switching elements Q _{1 to} Q ₆ such as IGBTs (insulated gate bipolar transistors) connected in a three-phase full bridge. The connection points of the switching elements of the upper and lower arms of each phase are respectively U-phase output terminals, An N-phase (neutral phase) output terminal and a V-phase output terminal are connected to the single-phase three-wire power system 204.

The PWM controller 205 that drives the switching elements Q _{1 to} Q ₆ receives PWM controllers 205U and 205N to which U-phase, N-phase, and V-phase voltage commands and a carrier (triangular wave) from the carrier signal generator 205C are input, respectively. , 205V.
The U-phase PWM controller 205U compares the U-phase voltage command with the carrier to generate driving signals for the switching elements Q ₁ and Q ₂ , and the N-phase PWM controller 205N receives the N-phase voltage command (= 0). ) And the carrier to generate drive signals for the switching elements Q ₃ and Q ₄ , and the V-phase PWM controller 205V compares the V-phase voltage command with the carrier to compare the switching elements Q ₅ and Q ₆ . A drive signal is generated.

  FIG. 4 is a waveform diagram showing the operation of this prior art. 4A shows the voltage command and carrier of each phase in the PWM control unit 205, FIG. 4B shows the output phase voltage of the inverter unit 200, and FIG. 4C shows the output line voltage of the inverter unit 200. Voltage (UN output voltage, VN output voltage) is shown.

  In FIG. 4A, the U-phase voltage command and the V-phase voltage command are sine wave signals having a phase difference of 180 ° from each other, and the N-phase voltage command is zero. Each phase output voltage shown in FIG. 4B is a voltage with respect to a virtual neutral point of the DC circuit (a potential point that is 1/2 of the voltage of the DC power supply 201). As can be seen from FIG. 4C, the output line voltage of the inverter unit 200 has a unipolar modulation waveform.

  According to this prior art, by controlling the N-phase output voltage to zero, the line voltage between the UN and VN can be easily controlled, and the amplitudes of the U-phase voltage command and the V-phase voltage command can be controlled. Further, the line voltage between UN and VN can be controlled independently by giving the phase difference individually.

Next, FIG. 5 is a configuration diagram of a voltage compensator linked to a single-phase three-wire power system.
In FIG. 5, terminals u and v on the secondary side (low voltage system) of the pole transformer 301 are connected to an AC input terminal of a single-phase converter 303 including semiconductor switching elements Q _{11 to} Q ₁₄ via an interconnection reactor 302. connected to u ₁ and v ₁ .

The DC output terminal of the single-phase converter 303 is connected to the DC input terminal of the single-phase three-wire inverter 305 composed of the semiconductor switching elements Q _{15 to} Q ₂₀ via the DC capacitor 304.
The AC output terminals u ₂ and N of the inverter 305 are connected to the secondary side of the low-voltage system series transformer 308 through the interconnection reactor 306, and the AC output terminals v ₂ and N are connected through the interconnection reactor 307. And connected to the secondary side of the low-voltage system series transformer 309.

In this prior art, the output voltage of the inverter 305 is superimposed on the system voltage via the series transformers 308 and 309, so that the line voltage of the system becomes 101 ± 6 [V], 202 ± 20 [V], for example. I have control.
Similarly to the single-phase three-wire inverter described in Patent Document 1, the n-phase output voltage command is set to zero, and the u-phase and v-phase output voltage commands are converted into sine wave signals having a phase difference of 180 ° from each other. By controlling the inverter 305, the un-line voltage and the vn line voltage can be individually controlled.

Japanese Patent Laid-Open No. 7-163153 (paragraphs [0007] to [0009], FIG. 1, FIG. 3, etc.)

The inverter unit 200 shown in FIG. 3 is directly connected to the single-phase three-wire power system 204. For this reason, a value near the rated voltage of the system is set in the output voltage command of the inverter unit 200.
On the other hand, the output voltage command of the inverter 305 constituting the voltage compensator of FIG. 5 has a wide range of values from zero to the rated voltage because the inverter 305 is connected to the system via the series transformers 308 and 309. Set to For this reason, when the system voltage greatly deviates from the target voltage range, the range in which the output voltage command of the inverter 305 changes also increases.

  As a PWM control method of the inverter 305 in this type of voltage compensator, when the unipolar modulation method is applied as in Patent Document 1, when the output voltage command is small, the output line voltage waveform is distorted. Since the output line voltage of the inverter 305 is superimposed on the system via the series transformers 308 and 309, the system voltage waveform is also distorted due to distortion of the output line voltage of the inverter 305, and as a result, peripheral devices connected to the system There is a problem of causing malfunctions and damages.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a single-phase three-wire inverter and a voltage compensator that can reduce distortion of the output line voltage waveform of an inverter that is PWM controlled.

In order to solve the above-mentioned problem, a single-phase three-wire inverter according to claim 1 comprises an inverter bridge in which upper and lower arms for one phase each having a semiconductor switching element are connected in parallel to form an inverter bridge. An inverter unit formed by connecting a DC power source between the input terminals;
A PWM control unit that compares the voltage command of each phase of the inverter bridge with the carrier to generate a drive signal for the semiconductor switching element of each phase, and sets the output voltage command of the first phase of the inverter bridge to zero The output voltage commands for the second phase and the third phase are variable, and the output line voltages between the first phase and the second phase and between the first phase and the third phase are respectively predetermined. PWM control unit that can be controlled to a value;
In a single-phase three-wire inverter equipped with
The PWM control unit
The carrier for the first phase and the carrier for the second phase and the third phase so that the output line voltage waveform becomes a dipolar modulation waveform during a period when the output voltage command for the second phase and the third phase is small. Means is provided for providing a phase difference therebetween.

  A single-phase three-wire inverter according to a second aspect is the single-phase three-wire inverter according to the first aspect, wherein carriers of the second phase and the third phase have the same phase.

  The single-phase three-wire inverter according to claim 3 is the single-phase three-wire inverter according to claim 1, wherein a phase difference is provided between the carrier for the second phase and the carrier for the third phase. Features.

The single-phase three-wire inverter according to claim 4 is the single-phase three-wire inverter according to claim 1,
An output voltage detecting means for detecting an output voltage of the single-phase three-wire inverter;
The means for giving a phase difference between the carrier for the first phase and the carrier for the second phase and the third phase adjusts the phase difference according to the detection value of the output voltage detection means. Features.

  According to a fifth aspect of the present invention, there is provided a voltage compensator that connects an AC output terminal of each phase of the single-phase three-wire inverter according to any one of the first to fourth aspects to a single-phase three-wire power system. The voltage fluctuation of the single-phase three-wire power system is compensated by the operation of the phase three-wire inverter.

  A voltage compensation device according to claim 6 is the voltage compensation device according to claim 5, further comprising system voltage detection means for detecting a voltage value of the single-phase three-wire power system, and detection of the system voltage detection means. The phase difference is adjusted according to a value.

According to the present invention, the output is controlled by controlling the inverter so that the output line voltage waveform of the single-phase three-wire inverter becomes a dipolar modulation waveform in a period in which the output voltage command of the other two phases excluding the neutral phase is small. Control accuracy when controlling the voltage over a wide range can be improved and distortion of the voltage waveform can be reduced.
For this reason, when a single-phase three-wire inverter is applied to, for example, a voltage compensator to compensate for voltage fluctuations in the power system, it is possible to prevent malfunctions and damage of peripheral devices connected to the system.

1 is a configuration diagram of a single-phase three-wire inverter according to an embodiment of the present invention. It is a wave form diagram which shows the operation | movement of FIG. It is a block diagram of the prior art described in patent document 1. FIG. It is a wave form diagram which shows the operation | movement of FIG. It is a block diagram of the voltage compensation apparatus linked | linked with a single phase three-wire type electric power system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a single-phase three-wire inverter according to this embodiment. In FIG. 1, the configuration of the inverter unit 200 is the same as that in FIG. 3, and thus the same parts as those in FIG.

The PWM control unit 3 that drives the semiconductor switching elements Q _{1 to} Q ₆ of the inverter bridge 202 is configured as follows.
That is, the PWM control unit 3 includes a voltage command generation unit 4 that generates U-phase, N-phase, and V-phase voltage commands, as in FIG. 3, and each phase voltage command (N-phase voltage command is 0) is a drive signal. The signals are input to U-phase, N-phase, and V-phase PWM controllers 7U, 7N, and 7V constituting the generation unit 7, respectively.

The carrier (triangular wave) output from the carrier signal generator 5 is directly input to the U-phase and V-phase PWM controllers 7U and 7V, and the N-phase PWM controller 7N is connected to the delay circuit 6 by the delay circuit 6. Input is delayed by a predetermined phase.
PWM controller 7U, 7N, 7V is a driving signal generated respectively by comparing the voltage command and the carrier input, these driving signals, the phases of the inverter bridge 202 of the switching element _Q 1 to Q ₆ It is designed to be turned on and off.
Each phase output terminal U, N, V of inverter bridge 202 is connected to a single-phase three-wire power system or connected to an AC load.

FIG. 2 is a waveform diagram showing the operation of this embodiment.
FIG. 2A shows voltage commands and carriers for each phase in the PWM control unit 3. Similar to FIG. 4A, the U-phase voltage command and the V-phase voltage command are sine wave signals having a phase difference of 180 °, and the N-phase voltage command is zero. The U-phase and V-phase carriers are the same, whereas the N-phase carrier has a phase difference of, for example, 45 degrees with respect to the U-phase and V-phase carriers due to the action of the delay circuit 6. It is.

  FIG. 2B shows an output phase voltage of the inverter unit 200, which is a voltage with respect to a potential point that is ½ of the voltage of the DC power supply 201. In this embodiment, due to the phase difference between the U-phase and V-phase carriers and the N-phase carrier, there is a phase difference between the N-phase output voltage and the U-phase and V-phase output voltages.

FIG. 2C shows the output line voltage (UN output voltage, VN output voltage) of the inverter unit 200.
Due to the phase difference between the N-phase output voltage and the U-phase and V-phase output voltages shown in FIG. 2B, in FIG. A unipolar modulation period and a dipolar modulation period occur. In correspondence with the U-phase voltage command and the V-phase voltage command, the average value of the output voltage between UN and the output voltage between VN is both small (near zero voltage) during the dipolar modulation period. .

  In other words, since the average value of the output line voltage can be controlled to be small in the dipolar modulation method, the U-phase and V-phase carriers and the N-phase carrier are controlled so that dipolar modulation is performed during a period when the output voltage command is small. If the phase difference is appropriately set, the accuracy of controlling the output line voltage of the inverter unit 200 to a minute value can be increased.

  Thus, for example, when the inverter unit 200 is connected to a single-phase three-wire power system as a voltage compensation device, the output voltage command for the U phase and the V phase of the inverter unit 200 covers a wide range from zero to the rated value of the system voltage. Even in such a case, the output line voltage can be controlled with high accuracy.

  In the embodiment of FIG. 1, the delay circuit 6 is used to provide a phase difference between the U-phase and V-phase carriers and the N-phase carrier. An N-phase carrier having a phase difference with respect to the U-phase and V-phase carriers may be generated by a carrier signal generator provided separately from the generator 5. Further, using a single carrier signal by the carrier signal generator 5 and two delay circuits having different delay times (phase differences), a phase difference is sequentially provided between U-phase, V-phase, and N-phase carriers. May be allowed.

  In short, a result is obtained by providing a phase difference between the U-phase and V-phase carriers and the N-phase carrier, or by sequentially providing a phase difference between the U-phase, V-phase, and N-phase carriers. As described above, the inverter unit 200 may be PWM-controlled so that the waveform of the output line voltage (UN output voltage, VN output voltage) becomes a dipolar modulation waveform.

Here, for example, in Japanese Patent Application Laid-Open No. 7-274517, in a plurality of PWM converters mounted on electric vehicles of the same organization and supplied with AC power from a pantograph through a common transformer, carriers for each converter are used. A control device that sequentially provides a phase difference is disclosed.
However, this known technique reduces the harmonic component by offsetting the peaks and valleys of the current waveform flowing through each converter by shifting the switching timing of each converter. The idea is different from the technique for controlling a part of the output line voltage waveform of the three-wire inverter to be a dipolar modulation waveform.

  The single-phase three-wire inverter according to the present invention can be used as a voltage compensator connected to a single-phase three-wire power system or a power supply device for a distributed power generation system.

3: PWM control unit 4: Voltage command generation unit 5: Carrier signal generator 6: Delay circuit 7: Drive signal generation unit 7U, 7N, 7V: PWM controller 200: Inverter unit 201: DC power supply 202: Inverter bridge Q ₁ To Q ₆ : Semiconductor switching element U: U-phase output terminal N: N-phase output terminal V: V-phase output terminal

Claims (6)

An inverter part formed by connecting an upper and lower arm for one phase having a semiconductor switching element for three phases in parallel to form an inverter bridge, and connecting a DC power source between DC input terminals of the inverter bridge;
A PWM control unit that compares the voltage command of each phase of the inverter bridge with the carrier to generate a drive signal for the semiconductor switching element of each phase, and sets the output voltage command of the first phase of the inverter bridge to zero The output voltage commands for the second phase and the third phase are variable, and the output line voltages between the first phase and the second phase and between the first phase and the third phase are respectively predetermined. PWM control unit that can be controlled to a value;
In a single-phase three-wire inverter equipped with
The PWM control unit
The carrier for the first phase and the carrier for the second phase and the third phase so that the output line voltage waveform becomes a dipolar modulation waveform during a period when the output voltage command for the second phase and the third phase is small. A single-phase three-wire inverter characterized by having means for providing a phase difference therebetween. In the single-phase three-wire inverter according to claim 1,
A single-phase three-wire inverter characterized in that the phases of carriers for the second phase and the third phase are equal. In the single-phase three-wire inverter according to claim 1,
A single-phase three-wire inverter having a phase difference between a carrier for the second phase and a carrier for the third phase. In the single-phase three-wire inverter according to claim 1,
An output voltage detecting means for detecting an output voltage of the single-phase three-wire inverter;
The means for giving a phase difference between the carrier for the first phase and the carrier for the second phase and the third phase adjusts the phase difference according to the detection value of the output voltage detection means. Characteristic single-phase three-wire inverter.   The AC output terminal of each phase of the single-phase three-wire inverter according to any one of claims 1 to 4 is connected to a single-phase three-wire power system, and the single-phase three-wire inverter is operated to operate the single-phase three-wire inverter. A voltage compensation device that compensates for voltage fluctuations in a three-wire power system. In the voltage compensation device according to claim 5,
System voltage detecting means for detecting a voltage value of the single-phase three-wire power system,
The voltage compensator, wherein the phase difference is adjusted according to a detection value of the system voltage detection means.

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