JP-7856212-B2 - Control device for a multilevel power conversion system and multilevel power conversion system

Inventors

• 神田 大介
• 深澤 一誠
• 岡安 正憲

Assignees

• 株式会社TMEIC

Dates

Publication Date

20260511

Application Date

20231101

Claims (7)

1. A control device for a multilevel power conversion system having a multilevel power converter having a plurality of semiconductor switching elements and a plurality of neutral point elements, wherein a carrier level shift modulation scheme is used, A process for generating a modulated wave based on the voltage command value of each phase, A process for generating a carrier wave, which is a triangular wave signal having a predetermined carrier period, A process for generating an injected carrier that changes within a predetermined amplitude range and has the same carrier period and opposite phase as the carrier wave, A process for generating a modulated wave in which the modulated wave and the injected carrier are superimposed by carrier injection control, A process to generate gate signals that control the operation of the multiple semiconductor switching elements and the multiple neutral point elements in the multilevel power converter, based on the result of comparing the modulated wave on which the carrier injection control has been performed with the multiple carrier waves, A control device characterized by performing the following.
2. In the control device according to claim 1, A control device characterized in that the predetermined amplitude range in the injected carrier is smaller than the amplitude of the carrier wave.
3. In the control device according to claim 2, A control device characterized in that the predetermined amplitude range in the injected carrier is in the range of 20% to 30% of the amplitude of the carrier wave.
4. In the control device according to claim 1, A control device characterized in that the predetermined amplitude range in the injected carrier is dynamically varied according to the DC voltage conditions and modulation rate.
5. In the control device according to claim 4, A control device characterized in that the predetermined amplitude range in the injection carrier is made smaller when the DC voltage is low and larger when the DC voltage is high.
6. In the control device according to claim 1, The control device is characterized in that the injected carrier changes within a predetermined amplitude range and is a triangular wave signal having the same carrier period and opposite phase as the carrier wave.
7. A multilevel power conversion system using a carrier level shift modulation scheme, Multiple DC capacitors connected in series between a positive terminal connected to a DC power supply or DC load and a negative terminal, via a DC neutral point, A plurality of semiconductor switching elements connected between the positive terminal and the negative terminal and an AC terminal connected to an AC power supply or an AC load, A plurality of neutral point elements connected between the DC neutral point and the AC terminal, A multilevel power converter having, A process for generating a modulated wave based on the voltage command value of each phase, A process for generating a carrier wave, which is a triangular wave signal having a predetermined carrier period, A process for generating an injected carrier, which is a signal that changes within a predetermined amplitude range, is in opposite phase to the carrier wave, and has the same carrier period as the carrier wave, A process for generating a modulated wave in which the modulated wave and the injected carrier are superimposed by carrier injection control, A process to generate gate signals that control the operation of the multiple semiconductor switching elements and the multiple neutral point elements in the multilevel power converter, based on the result of comparing the modulated wave on which the carrier injection control has been performed with the multiple carrier waves, A control device that performs the following: A multilevel power conversion system characterized by comprising the following features.

Description

The present invention relates to a control device for a multilevel power conversion system and a multilevel power conversion system. Conventionally, a multilevel power converter is known that comprises, for example, a plurality of DC capacitors connected in series on the DC side, and a plurality of semiconductor switching elements connected to the series connection points of the plurality of DC capacitors (see, for example, Patent Document 1). In this specification and the drawings, the DC connection points of the plurality of DC capacitors are also referred to as "DC neutral points," and the plurality of semiconductor switching elements connected to the DC connection points (DC neutral points) of the plurality of DC capacitors are also referred to as "neutral point elements." Japanese Patent Publication No. 2003-319662 This figure shows an example of the configuration of a multilevel power conversion system according to one embodiment.Figure 1 is a circuit diagram showing an example of the circuit configuration of a multilevel power converter in the multilevel power conversion system shown in Figure 1.Figure 1 shows an example of the configuration of a control device in a multilevel power conversion system.Figure 3 shows an example of the control configuration in the voltage command generation unit of the control unit shown in Figure 3.This figure shows an example of the control configuration in the gate signal generation unit of the control unit shown in Figure 3.This figure shows an example of the control configuration in the gate signal generation unit according to a comparative example.Figure 6 shows an example of carrier level shift modulation in the gate signal generation unit of the comparative example shown.This figure shows an example of a switching pattern in carrier-level shift modulation.Figure 8 shows an example of each gate signal of each semiconductor element in carrier level shift modulation of the switching pattern shown in Figure 8.This is a schematic diagram of the harmonic spectra of the output voltages of each phase of a power converter using carrier-level shift modulation.Figure 7 shows a magnified view of the area around the 0 crossover and an example of the gate signals of each semiconductor element at that time.Figure 7 is a schematic diagram showing an example of the relationship between the modulated wave, carrier wave, and each phase output voltage near the peak of the modulated wave.Figure 12 shows an example of the Fourier series expansion of the square wave of each phase output voltage.This figure shows an example of the relationship between the sign of a modulated wave and the slope of a modulated wave.Figure 14 is a schematic diagram showing an example of the relationship between the modulated wave, carrier wave, and each phase output voltage in Pattern 1.Figure 14 is a schematic diagram showing an example of the relationship between the modulated wave, carrier wave, and each phase output voltage in Pattern 2.Figure 14 is a schematic diagram showing an example of the relationship between the modulated wave, carrier wave, and each phase output voltage in Pattern 3.Figure 14 is a schematic diagram showing an example of the relationship between the modulated wave, carrier wave, and each phase output voltage in pattern 4.Figure 5 shows an example of the relationship between the carrier wave and the modulated wave when carrier injection control is performed in the gate signal generation unit according to one embodiment shown in Figure 5.Figure 19 shows an enlarged view of the area around the 0 crossover and an example of the gate signals of each semiconductor element at that time.This is a schematic diagram illustrating an example of the relationship between the modulated wave, carrier wave, and each phase output voltage during a period when the slope of the modulated wave is negative.This is a schematic diagram illustrating an example of the relationship between the modulated wave, carrier wave, and each phase output voltage during a period when the slope of the modulated wave is positive.This figure shows an example of the harmonic spectrum of the DC voltage-normalized inter-line output voltage, both when carrier injection control is not performed and when carrier injection control is performed.This figure shows an example of a carrier wave and a modulated wave under the condition that the DC voltage is small compared to the AC output voltage.This figure shows a magnified view of the area near the peak of the modulated wave in Figure 24, along with an example of the gate signal at that time.This figure shows an example of a carrier wave and a modulated wave with carrier injection control under the condition that the DC voltage is small relative to the AC output voltage.This figure shows a magnified view of the area near the peak of the modulated wave in Figure 26, along with an example of the gate signal at that time.Figure 2 shows an example of the charging and discharging of