JP2006238645A - Serial multiple matrix converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a serial multiple matrix converter by which a value of a capacitor of an input filter is suppressed to be smaller, even when capacity of the matrix converter becomes large. <P>SOLUTION: The matrix converter includes an input-side polyphase transformer 2 connected to polyphase AC power supply 1, and a polyphase input single-phase output matrix converter 10 of an (a) phase connected to the secondary side of the transformer 2. The converter 10 is constituted of a quantity of (b) of a cell 5 connected in series, in which the cell is constituted of the input filter 3 and a converter unit 4. Each cell 5 generates an output voltage through PWM by a carrier triangular wave, having a phase difference of 360°/n(n=a×b) with respect to each other, and the series multiple matrix converter outputs an (a) phase AC voltage by the converter 10. The resonance frequency of the input filter 3 is set higher than the carrier frequency, which is a source for generating PWM waveforms, by which harmonic components are removed in a current of a carrier frequency component, flowing out to the primary side of the transformer 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a serial multiple matrix converter that generates AC power of an arbitrary frequency from an AC power source and drives an AC load such as an AC motor.

  Conventionally, a PWM (Pulse Width Modulation) inverter method has been employed to drive an AC load such as an AC motor at a variable speed using an AC power source such as a commercial power source. In this PWM inverter system, a commercial power supply is once converted into direct current by a rectifier circuit unit, and then, multiphase AC power having an arbitrary frequency is generated using an inverter.

  However, the PWM inverter system temporarily converts the commercial power supply into direct current, so it is necessary to provide a smoothing capacitor (electrolytic capacitor) with a large capacity in order to reduce the ripple component after rectification, which is a bottleneck in miniaturization. . In addition, since the two conversions of AC → DC → AC are performed using the semiconductor switching elements, there is a limit to increasing the efficiency. Further, there is a problem that regenerative energy from the load side cannot be used due to irreversibility between the commercial power source side and the AC load side such as an AC motor.

In recent years, a cycloconverter that directly generates an AC output of an arbitrary frequency from a commercial AC power source having a constant frequency has been adopted (see, for example, Patent Documents 1 to 3).
As the circuit configuration of the cycloconverter, a “matrix converter” type in which each phase of the input (commercial power supply side) and each phase of the output (AC load side) are directly connected by a high-speed switch is often used.

  FIG. 6 shows a configuration of a serial multiple matrix converter that has been conventionally employed. This serial multiple matrix converter includes an input-side multiphase transformer 2 connected to a multiphase (three-phase in this example) AC power source 1 and an a phase (a ≧ a) connected to the secondary side of the input multiphase transformer 2. 3), the multiphase input single phase output matrix converter 10 includes a cell 5 including an input filter 3 and a matrix converter unit 4 each including a reactor 3a and a capacitor 3b. b (b ≧ 2) are connected in series. Each cell 5 generates an output voltage by PWM using a carrier triangular wave having a phase difference of 360 ° / n (n = a × b), and drives a load 6 such as a motor.

  In the serial multiplex matrix converter having such a configuration, the AC voltage on the input side is switched at high speed at a predetermined carrier frequency, and therefore harmonics resulting from the switching flow out to the input side. Therefore, conventionally, as shown in FIG. 6, by setting the resonance frequency of the input filter 3 of the matrix converter unit 4 lower than the carrier frequency, the carrier frequency is set in the attenuation region of the input filter 3 as shown in FIG. The harmonics having the carrier frequency due to the switching of the matrix converter unit 4 flowing out to the input side are reduced.

  Further, the input filter 3 of the matrix converter unit 4 shown in FIG. 6 includes a reactor 3a and a capacitor 3b, and removes higher harmonic components such as carrier frequency components. As shown in FIG. 8, some harmonic components that could not be obtained are provided by a damping filter 20 including a reactor 21, a capacitor 22, and a resistor 23. 8 is connected to the input side of each cell 5, that is, to the secondary side of the input-side multiphase transformer 2.

International Publication No. WO 97/09773 JP 2001-258258 A JP 2004-229492 A

  As described above, in the input filter 3 of the conventional matrix converter unit 4 shown in FIG. 6, because the resonance frequency must be lower than the carrier frequency, the capacitance value of the filter capacitor 3b determined thereby is particularly When the capacity of the matrix converter is increased, the matrix converter becomes larger. As a result, there is a problem that space saving is hindered by an increase in the size of the cell 5. In addition, when a thyristor converter is connected to the same system as the input power supply, thereby causing waveform distortion in the input voltage, the resonance frequency of the input filter 3 is low, which causes a resonance phenomenon due to waveform distortion. There was also a point.

Furthermore, as shown in FIG. 8, if a damping filter 20 for removing a harmonic component of a certain order that could not be removed by the input filter 3 is connected to each cell, a harmonic of a certain order is generated. Due to the components, the size of the cell 5 becomes larger and the size of the cell 5 depends on the harmonic order. Moreover, since the damping filter 20 for n cells is required, cost performance is deteriorated, which is disadvantageous in terms of economy.
In order to solve this problem, there is a method in which the damping filter 30 including the reactor 31, the capacitor 32, and the resistor 33 is configured on the primary side of the input-side polyphase transformer 2 as shown in FIG. The point is that the voltage on the primary side of the input-side multiphase transformer 2 of the serial multiplex matrix converter is high, and therefore it is necessary to make the damping filter 30 compatible with high voltage. From the viewpoint of high voltage compatibility, it is necessary to handle and handle high voltage electric appliances, which is disadvantageous in terms of structure and cost performance.

  The present invention has been made in view of such problems. Even when the capacity of the serial multiple matrix converter is increased, the value of the capacitor is kept small, and a thyristor converter is connected to the same system as the input power supply. In such a case, an object of the present invention is to provide a serial multiple matrix converter capable of minimizing the resonance phenomenon caused thereby.

  A first configuration of the present invention includes an input-side multi-phase transformer connected to a multi-phase AC power source, and an a-phase (a ≧ 3) multi-phase input unit connected to a secondary side of the input-side multi-phase transformer. The multi-phase input single-phase output matrix converter is configured by connecting in series b cells (b ≧ 2) including an input filter including a reactor and a capacitor and a converter unit. Each cell generates an output voltage by PWM using a carrier triangular wave having a phase difference of 360 ° / n (n = a × b), and outputs a phase AC voltage by the multiphase input single layer output matrix converter. In the serial multiple matrix converter, the resonance frequency of the input filter composed of the reactor and the capacitor is set to be higher than the carrier frequency that generates the PWM waveform. It is set high, and thereby, harmonic components contained in the current of the carrier frequency component flowing out to the primary side of the input side multiphase transformer are removed.

  A second configuration of the present invention includes an input-side multi-phase transformer connected to a multi-phase AC power source, and an a-phase (a ≧ 3) multi-phase input unit connected to the secondary side of the input-side multi-phase transformer. The multi-phase input single-phase output matrix converter is configured by connecting in series b cells (b ≧ 2) including an input filter including a reactor and a capacitor and a converter unit. Each cell generates an output voltage by PWM using a carrier triangular wave having a phase difference of 360 ° / n (n = a × b), and outputs a phase AC voltage by the multiphase input single layer output matrix converter. In the serial multiple matrix converter, a current of a specific order harmonic component that flows out to the primary side of the input-side multiphase transformer is caused by a winding added in the input-side multiphase transformer. It is characterized in that it is removed by a damping filter composed of an inductance and a capacitor and a resistor connected in series to the inductance.

  According to the first configuration of the present invention, the resonance frequency of the input filter is set higher than the carrier frequency from which the PWM waveform is generated. Capacitors can be kept small, and the resonance frequency of the input filter can be set to a high value away from the distorted harmonic frequency by the thyristor converter, which usually exists at 1 kHz or less, so the thyristor converter is connected to the same power supply. Even in the case where it is, it is possible to suppress the resonance phenomenon caused thereby.

  According to the second configuration of the present invention, a current of a specific order harmonic component that flows out to the primary side of the input-side multiphase transformer, an inductance due to the winding added in the input-side multiphase transformer, and the inductance in series By using a damping filter consisting of a connected capacitor and resistor, it is possible to eliminate the current of a specific order harmonic component, and the damping filter can be placed in the input-side polyphase transformer. And can be constructed as a low pressure, which is advantageous in terms of structure and cost performance.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[Embodiment 1]
1 is a graph showing frequency characteristics of an input filter according to Embodiment 1 of the present invention, FIG. 2 is a connection diagram of a multiphase input single phase output matrix converter according to Embodiment 1, and FIG. 3 is a polyphase of FIG. FIG. 4 is a vector diagram of harmonic components according to the first embodiment, and FIG. The entire circuit configuration is the same as that in FIG.

  In the first embodiment, as shown in FIG. 1, the resonance frequency of the input filter 3 is set higher than the carrier frequency from which the PWM waveform is generated. Specifically, in the gain characteristic of the input filter 3, the carrier frequency is lower than the resonance frequency and the gain is approximately 1. As a result, the harmonic component having the carrier frequency is directly output to the power supply side. However, in the high-voltage matrix converter using the multiplex drive method, output multiphase (three-phase) voltage is generated by n cells (units). Since the phase of the carrier triangular wave for output is shifted by 360 ° el / n, the harmonic component having the carrier frequency is canceled and does not go out of the apparatus.

  This will be specifically described with reference to FIGS. In a high-voltage matrix converter that employs a multiplex drive system, as shown in FIG. 2, b units (three units) are star-connected for each a phase (three phases), and output is performed in nine cells 5 in this example. The phase of the carrier triangular wave that generates the voltage is shifted by 40 ° el (360 ° el / 9 units) and output. Table 1 shows each phase of nine cells 5 and the phase of the carrier triangular wave that generates the output voltage of each stage.

  FIG. 3 (a) shows the waveform of each phase of the carrier frequency, and (b), (c), and (d) show the output voltage and each cell voltage of the U phase, V phase, and W phase, respectively. As shown in FIG. 3, the harmonic component having the carrier frequency of each cell 5 is canceled on the primary side of the input-side polyphase transformer 2. That is, in the present embodiment, since the triangular wave of the carrier frequency is shifted by 40 ° el, the phase of each triangular wave is as shown in the vector diagram of FIG. For example, when considering the phase of the triangular wave that generates the U phase, U1 to U3 are shifted by 120 ° el, so the synthesis is zero. That is, since the synthesis of the carrier triangular wave that generates the output voltage for each phase (U phase, V phase, W phase) becomes zero, the harmonic component related to the carrier frequency component can be canceled as a result. In this way, harmonic components having a carrier frequency due to switching of the matrix converter unit 4 flowing out to the input side, which is the original purpose of the input filter 3, can be reduced.

  Since the resonance frequency of the input filter 3 can be set high from such a control method, the capacity of the input filter capacitor can be kept small even when the capacity of the matrix converter is increased.

[Embodiment 2]
FIG. 5 is a circuit diagram showing a configuration of the second embodiment of the present invention. In the second embodiment, a winding 7 a is added in the input-side multiphase transformer 2, and a capacitor 7 b and a resistor 7 c are connected in series to the winding 7 a to form a damping filter 7. Other configurations are the same as those in FIG. 6, and thus the same reference numerals are given and description thereof is omitted.

  In the second embodiment, the inductance in the damping filter 7 is configured using the winding 7a added in the input-side multiphase transformer 2, and at this time, the damping filter 7 portion is connected to the input-side polyphase. The turns ratio is set to be lower than the transformer primary voltage (high voltage). By adopting such a configuration, the structure of the cell 5 is not influenced by the generated harmonic component of a certain order, and the number of damping filters can be reduced as compared with the conventional example shown in FIG. 9 can be configured at a lower pressure than the conventional example shown in FIG. 9, which is advantageous in terms of structure and cost performance.

  The present invention is a serial multiple matrix converter that suppresses a resonance phenomenon, and can be used for a converter that drives an AC load such as an AC motor.

It is a graph which shows the frequency characteristic of the input filter by Embodiment 1 of this invention. 1 is a connection diagram of a multiphase input single phase output matrix converter according to Embodiment 1 of the present invention. FIG. 3 is a graph showing a current command and a voltage waveform of each cell in the multiphase input single phase output matrix converter of FIG. 2. It is a vector diagram of the harmonic component by Embodiment 1 of this invention. It is a circuit diagram which shows the structure of Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the serial multiple matrix converter to which Embodiment 1 of this invention is applied. It is a graph which shows the frequency characteristic of the input filter in the past. It is a circuit diagram which shows the structure of the conventional serial multiple matrix converter. It is a circuit diagram which shows the other structure of the conventional serial multiple matrix converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polyphase AC power source 2 Input side polyphase transformer 3 Input filter 3a Reactor 3b Capacitor 4 Matrix converter unit 5 Cell 6 Load 7 Damping filter 7a Winding 7b Capacitor 7c Resistor 10 Multiphase input single phase output matrix converter

Claims (2)

An input-side multi-phase transformer connected to a multi-phase AC power source, and an a-phase (a ≧ 3) multi-phase input single-phase output matrix converter connected to the secondary side of the input-side multi-phase transformer, A multi-phase input single-phase output matrix converter is configured by connecting b cells (b ≧ 2), each of which is composed of an input filter including a reactor and a capacitor, and a converter unit, and each of the cells is 360 ° / In a serial multiple matrix converter that generates an output voltage by PWM using a carrier triangular wave having a phase difference of n (n = a × b), and outputs an a-phase AC voltage by the multi-phase input single-layer output matrix converter,
The resonance frequency of the input filter consisting of the reactor and the capacitor is set to be higher than the carrier frequency from which the PWM waveform is generated, and thus included in the current of the carrier frequency component that flows out to the primary side of the input-side multiphase transformer. The serial multiple matrix converter is characterized in that it eliminates harmonic components. An input-side multi-phase transformer connected to a multi-phase AC power source, and an a-phase (a ≧ 3) multi-phase input single-phase output matrix converter connected to the secondary side of the input-side multi-phase transformer, A multi-phase input single-phase output matrix converter is configured by connecting b cells (b ≧ 2), each of which is composed of an input filter including a reactor and a capacitor, and a converter unit, and each of the cells is 360 ° / In a serial multiple matrix converter that generates an output voltage by PWM using a carrier triangular wave having a phase difference of n (n = a × b), and outputs an a-phase AC voltage by the multi-phase input single-layer output matrix converter,
A current of a specific order harmonic component that flows out to the primary side of the input-side multiphase transformer, an inductance by a winding added in the input-side multiphase transformer, and a capacitor and a resistor connected in series to the inductance A serial multiple matrix converter characterized by being removed by a configured damping filter.

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