JP2004266972A - Alternating current-alternating current power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain sine waves without distortion in input current waveform or output voltage waveform, make it possible to detect output currents without causing a trouble in a power supply system or such loads as a motor and without detection delay, and accomplish high-performance control of the motor and the like. <P>SOLUTION: An alternating current-alternating current power converter has a PWM (pulse width modulation) rectifier which converts the polyphase alternating-current power of a power supply into direct-current power, and a PWM inverter which converts direct-current power outputted from the PWM rectifier through a direct-current link portion into polyphase alternating-current power. The direct-current link portion is not provided with a smoothing filter. The alternating current-alternating current power converter is provided with an on-off ratio extracting means 35 and a symmetrical deformed triangular wave generating means 41. The on-off ratio extracting means extracts the ratio of the on period to the off period of the phase switched by the PWM rectifier. Based on the ratio of the on period to the off period, the symmetrical deformed triangular wave generating means varies the peak position of the carrier of the rectifier 10, and generates a triangular wave symmetrical with respect to the peak position of the carrier of the rectifier 10 as the carrier of the PWM inverter 20. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１９】
表１に基づいてインバータ側キャリアを生成すると、図２に示すように、インバータ側キャリアは整流器側キャリアのピーク（山，谷）の位置を中心として対称な変形三角波になる。この結果、インバータ２０側のＰＷＭパルスは、整流器側キャリアのピーク位置を中心として対称になる。
従って、整流器側キャリアのピークのタイミングで電力変換装置の出力電流（負荷電流）をサンプリングすれば、電流検出部にリプルを除去するフィルタを設ける等の手段を講じなくても、負荷電流として平均値を時間遅れなく検出することができ、出力電流の制御を高精度に行うことができる。
【００２０】
図１の実施形態において、オンオフ比抽出手段３５は整流器１０のスイッチングしている相（図２の例ではＲ相）のオンオフ比（図２におけるＴ_１，Ｔ_２の比）を検出し、このオンオフ比は対称変形三角波発生手段４１に入力される。また、キャリア発生手段３２から出力される整流器側キャリアも対称変形三角波発生手段４１に入力される。
対称変形三角波発生手段４１では、上記オンオフ比と整流器側キャリアのピークのタイミングとを用い、前記表１の論理に従って増減する図２のインバータ側キャリア（対称変形三角波）を作成し、出力する。
比較手段４２では、このインバータ側キャリアと各相の出力電圧指令ｖ_ｕ ^＊，ｖ_ｖ ^＊，ｖ_ｗ ^＊とを比較し、Ｕ相、Ｖ相、Ｗ相のインバータ側ＰＷＭパルスを出力する。
【００２１】
図３は、図１における対称変形三角波発生手段４１の具体例をその周辺の構成要素と共に示したブロック図であり、図４は対称変形三角波発生手段４１の動作説明図である。
ここでは、対称変形三角波発生手段４１をディジタルハードウェアにより構成した例を示しているが、アナログ回路により構成することも可能であり、対称変形三角波をソフトウェアにより作成しても良い。
【００２２】
図３において、４１１は排他的論理和（ＥＸ−ＯＲ）回路であり、整流器側キャリアのアップ／ダウン信号と整流器側のＰＷＭパルスとに基づき、前述した表１の論理に従ってインバータ側キャリアのアップ／ダウン指令を出力する。ここで、整流器側キャリアのアップ信号は論理“１”、ダウン信号は論理“０”、整流器側ＰＷＭパルスのＨｉｇｈは論理“１”、Ｌｏｗは論理“０”、インバータ側キャリアのアップ指令は論理“１”、ダウン指令は論理“０”に、それぞれ対応する。
【００２３】
排他的論理和回路４１１から出力されるインバータ側キャリアのアップ／ダウン指令は、アップダウンカウンタ４１２に加えられている。このアップダウンカウンタ４１２は、整流器側キャリアのピーク（山，谷）のタイミングで発生するカウンタロード信号により、上記アップ／ダウン指令に従ってインバータ側キャリアのピーク値をアップカウントまたはダウンカウントし、そのカウント値をインバータ側キャリア（対称変形三角波）として出力する。
【００２４】
アップダウンカウンタ４１２４１２のクロックは一定であり、アップカウントまたはダウンカウントする期間は、整流器側ＰＷＭパルスのデューティ比に依存する。従って、図４に示すように、整流器側ＰＷＭパルスのＨｉｇｈ，Ｌｏｗに応じて、インバータ側キャリアのピーク値は異なってくる。
【００２５】
そこで、あらかじめソフトウェアにより、元のインバータ出力電圧指令からインバータ側キャリアのピーク値に合わせて補正した電圧指令ｖａ_ｎと電圧指令ｖｂ_ｎとを演算し、それぞれ、電圧指令レジスタ４２２，４２３に書き込んでおく。そして、インバータ側キャリアのピーク値が整流器側ＰＷＭパルスのＨｉｇｈ，Ｌｏｗに応じて変化するのに対応させて、比較器４２１により比較する電圧指令をセレクタ４２４により切り替えることとする。ここで、セレクタ４２４は、図３に示したように、整流器側ＰＷＭパルスに基づいて、インバータ側キャリアのピーク値が変化することを認識可能である。
従って、セレクタ４２４から出力される電圧指令は、図４に示す如く、整流器側ＰＷＭパルスがＬｏｗ→Ｈｉｇｈ→Ｌｏｗ→……と変化するにつれて電圧指令レジスタ４２２または４２３の出力を選択し、ｖａ_ｎ−１→ｖａ_ｎ→ｖｂ_ｎ→ｖｂ_ｎ＋１→ｖａ_ｎ＋１→……と変化していく。
【００２６】
このようにしてセレクタ４２４により選択された出力電圧指令とインバータ側キャリアとを比較器４２１にて比較することにより、インバータ２０側のＰＷＭパルスを得るものである。
なお、インバータ側キャリアのピーク値はソフトウェアにより演算し、求めたピーク値をカウンタロード信号により整流器側キャリアの山，谷のタイミングでアップダウンカウンタ４１２へロードする。
【００２７】
次に、図５は本発明の第２実施形態を示す構成図であり、この実施形態では主回路の電力変換器としてマトリクスコンバータ５０を用いている。このマトリクスコンバータ５０は、入力端子Ｒ，Ｓ，Ｔと出力端子Ｕ，Ｖ，Ｗとの間に双方向スイッチ５１〜５９を接続して構成されており、各スイッチ５１〜５９は、例えばＩＧＢＴ等の２個の半導体スイッチング素子を逆方向に直列接続すると共に、各スイッチング素子に環流ダイオードをそれぞれ逆並列に接続して構成される。
また、制御装置の構成は図１と実質的に同様であり、図１におけるゲートパルス発生手段３４，４３に代えてＰＷＭパルス合成手段６０が設けられ、その出力パルスが双方向スイッチ５１〜５９に与えられている。
【００２８】
マトリクスコンバータ５０の制御に当たっては、図１におけるＰＷＭ整流器１０、ＰＷＭインバータ２０と同様な構成のＰＷＭ整流器、ＰＷＭインバータをマトリクスコンバータ５０内に仮想し、これらの仮想整流器及び仮想インバータに対するＰＷＭパルス（スイッチング関数）を合成手段６０により合成してマトリクスコンバータ５０を制御する方法が知られている（例えば、「マトリクスコンバータにおける入出力無効電力の非干渉制御法」，伊藤里絵・高橋勲，電気学会半導体電力変換研究会ＳＰＣ−０１−１２１，ＩＥＡ−０１−６４を参照）。
【００２９】
すなわち、マトリクスコンバータ５０の電力変換動作は、以下の数式１によって表される。なお、数式１において、ｖ_ｕ，ｖ_ｖ，ｖ_ｗは出力相電圧、ｖ_ｒ，ｖ_ｓ，ｖ_ｔは入力相電圧、Ｓ_５１〜Ｓ_５９は双方向スイッチ５１〜５９のスイッチング関数である。
【００３０】
【数１】

【００３１】
また、上記スイッチング関数Ｓ_５１〜Ｓ_５９は、仮想整流器側のスイッチング関数及び仮想インバータ側のスイッチング関数を用いて、数式２のように表すことができる。
【００３２】
【数２】

【００３３】
従って、本実施形態では、図５における比較手段３３からのＰＷＭパルスに基づく仮想整流器側のスイッチング関数と、対称変形三角波を用いた比較手段４２からのＰＷＭパルスに基づく仮想インバータ側のスイッチング関数とを用いてＰＷＭパルス合成手段６０が数式２によりスイッチング関数を演算し、このスイッチング関数に従って双方向スイッチ５１〜５９をオンオフ制御すればよい。
この場合、仮想整流器側の動作は、電源短絡を許容しないため電流形のＰＷＭ整流器と等価な動作となる。
【００３４】
この実施形態では、マトリクスコンバータ５０内の仮想整流器のスイッチングしている相のオンオフ比に基づき、対称変形三角波発生手段４１が、仮想整流器キャリアに対してピーク位置を変化させ、かつ、仮想整流器側キャリアのピーク位置に対して対称である対称変形三角波を発生させ、比較手段４２が、この変形三角波と各相の出力電圧指令とを比較することにより、仮想直流リンク部電流がゼロである期間を各相電流に対して均等に配置するようなインバータ側のＰＷＭパルスを発生させる。
仮想整流器側のＰＷＭパルスの発生動作は第１実施形態と同様であるため、説明を省略する。
【００３５】
なお、本発明は、各実施形態で説明した三相以外の多相交流の相互変換にも適用可能である。
【００３６】
【発明の効果】
以上のように本発明によれば、大形のエネルギーバッファを有しない交流−交流電力変換装置において、入力電流波形及び出力電圧波形に歪みのない正弦波を得ることにより、電源系統や電動機等の負荷に障害を与えず、小形かつ長寿命の電力変換装置を提供することができる。
特に、整流器キャリアのピークのタイミングで負荷電流を検出すれば、検出遅れなしに負荷流の平均値を検出可能であり、高精度な電流制御が可能になる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示す構成図である。
【図２】第１実施形態の動作説明図である。
【図３】図１における対称変形三角波発生手段の具体例を示すブロック図である。
【図４】図３の動作説明図である。
【図５】本発明の第２実施形態を示す構成図である。
【図６】先願のＰＷＭパルス発生方法の説明図である。
【符号の説明】
１０：ＰＷＭ整流器
１１〜１６：半導体交流スイッチ
２０：ＰＷＭインバータ
２１〜２６：半導体スイッチング素子
３１：台形波指令発生手段
３２：キャリア発生手段
３３，４２：比較手段
３４，４３：ゲートパルス発生手段
３５：オンオフ比抽出手段
４１：対称変形三角波発生手段
４１１：排他的論理和回路
４１２：アップダウンカウンタ
４２１：比較器
４２２，４２３：電圧指令レジスタ
４２４：セレクタ
５０：マトリクスコンバータ
５１〜５９：双方向スイッチ
６０：ＰＷＭパルス合成手段
Ｒ，Ｓ，Ｔ：交流入力端子
Ｕ，Ｖ，Ｗ：交流出力端子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor power converter that outputs a polyphase AC voltage from a polyphase AC voltage using a semiconductor switching element without having a large-sized energy buffer such as a capacitor or a reactor. And an AC-AC power conversion device configured to reduce distortion of an output voltage waveform.
[0002]
[Prior art]
The present applicant has already filed an application for this type of AC-AC power converter as Japanese Patent Application No. 2003-2903.
The AC-AC power converter according to the prior application converts a multi-phase AC power of a power supply into a DC power and a PWM rectifier, and converts DC power output from the PWM rectifier through a DC link unit into a polyphase AC power. In an AC-AC power converter having a PWM inverter and having no smoothing filter in the DC link section, an on / off ratio extracting means for extracting a ratio of an on / off period of a switching phase of the PWM rectifier; A deformed carrier generating means for generating a deformed carrier in which the position of the carrier of the PWM inverter with respect to the carrier of the PWM rectifier is changed such that the input current waveform of each phase of the PWM rectifier becomes substantially a sine wave based on the on / off period ratio; , Is provided.
[0003]
In summary, in the power converter described above, by shifting the peak position of the carrier (triangular wave) of the PWM inverter in accordance with the on / off ratio of the switching phase of the PWM rectifier, the inclination of the carrier is different from that of the PWM rectifier. Then, the carrier is compared with a voltage command to obtain a PWM pulse on the inverter side.
Here, when there is no smoothing filter as an energy buffer in the DC link unit, the input current of the inverter (current of the DC link unit) becomes zero when the output voltage of the inverter is zero. For this reason, on the PWM rectifier side, the input current waveform of each phase is partially removed in order to reduce the current of the DC link unit to zero, and as a result, an imbalance occurs in the input current waveform of each phase.
Therefore, the timing of zero voltage generation is important in the control on the inverter side, and in order to prevent imbalance in the input current waveform, the period in which the current in the DC link section becomes zero due to the generation of zero voltage is controlled by the PWM rectifier side. It is necessary to make the ratio almost the same for each phase conduction period (PWM pulse) (the period during which the current in the DC link unit becomes zero is evenly arranged for the PWM pulse on the PWM rectifier side).
[0004]
Here, FIG. 6 shows the principle of generation of carriers on the inverter side in the above-mentioned prior application.
Under the control of the PWM rectifier, the input current is distributed to the R phase and the S phase, and the combined current flows to the T phase. At this time, (the shaded portion in FIG. 6) period each phase the input current is removed by the zero period T ₀ of the DC link current i _dc by zero voltage vector of the inverter, S-phase also current i _r of R-phase for even the current i _s, it is desirable to be substantially the same ratio for the duration of each flow.
At the same time, it is necessary to make the average value of the DC link section current i _dc during one cycle of the carrier equal between the R-phase conduction period and the S-phase conduction period.
[0005]
Therefore, as shown in FIG. 6, the peak position of the carrier on the inverter side is determined by the ratio of the on-off period of the switching phase (R phase) of the PWM rectifier (ratio of the on-period of the R phase and the S phase), that is, FIG. A deformed triangular wave is obtained by moving the wave according to the ratio of T ₁ , T ₂ , and the zero voltage period T is set so that the average value of the DC link section current i _dc coincides in the ON period T ₁ and the OFF period T ₂ of the R phase. Controls the occurrence timing of ₀ .
At this time, the ratio of the periods T ₁ and T ₂ becomes equal to the ratio of the periods t ₁ and t ₂ in the zero current period T ₀ , and the ratio to the original R-phase conduction period T ₂ (caused by the zero current period T ₀ ). ) and the ratio of deletion period t ₂ of the R-phase input current waveform, and the ratio of deletion period t ₁ of the original with respect to S-phase conduction period T ₁ (due to zero current period T ₀₎ S-phase input current waveform is equal .
That is, there is a peak position that divides the zero period T ₀ of the DC link section current i _{dc according} to the ratio of the conduction period of the R phase and the S phase (the ratio of T ₂ , T ₁ , that is, the ratio of t ₂ , t ₁ ). By generating the modified triangular wave and using it as a carrier on the inverter side, the average current of each phase within one cycle of the carrier can be matched and equalized.
[0006]
As a specific method for creating variations triangular wave extracts off ratio of R-phase is the switching phase of the PWM rectifier, the positive slope of the carrier is proportional to T _1, is proportional to the negative of the slope of the carrier to T ₂ .
Similarly, in other S-phase and T-phase operation modes, by generating a modified triangular wave whose slope is controlled in proportion to the on / off period of the switching phase of the PWM rectifier, the period during which each phase current is deleted is reduced by the PWM rectifier side. The ratio can be set to be substantially the same as the conduction period of each phase, and the input current waveform can be made substantially sinusoidal by correcting the imbalance of the input current waveform of each phase.
[0007]
As a result, in the modified triangular wave, the slope of the carrier is different depending on whether the carrier is positive or negative. However, the PWM pulse in one cycle of the carrier has an on / off ratio according to the voltage commands v _u ^* , v _v ^* , v _w ^* on the inverter side, and the carrier 1 Since the average voltage in the cycle matches the voltage commands v _u ^* , v _v ^* , v _w ^* , a desired output voltage can be obtained on the inverter side.
[0008]
The prior application, Japanese Patent Application No. 2003-2903, has not been published yet at the time of filing this application, but the following non-patent document 1 is a document to which the exception of the loss of novelty of the prior application has been applied. .
[0009]
[Non-patent document 1]
Junichi Ito et al., "Improvement method of input / output waveform of matrix converter by virtual AC / DC / AC conversion method", Institute of Electrical Engineers of Japan (Semiconductor Power Conversion / Industrial Electricity Application Joint Research Group), SPC-02 -77-96, IEA-02-18-37, November 14, 2002, p. 75-80
[0010]
[Problems to be solved by the invention]
In the power converter described in the prior application, a PWM pulse is generated using a modified triangular wave having different positive and negative slopes on the inverter side. Therefore, as shown in FIG. Neither the carrier peak nor the carrier peak on the rectifier side is distributed symmetrically.
As a result, for example, in a system that generates an output voltage command so that the output current (load current) of the power conversion device matches the command value and compares the output voltage command with the carrier to generate a PWM pulse of the inverter, Even if the output current is sampled at the peak of the carrier on the side or the peak of the carrier on the rectifier side, the average value of the current cannot be detected, and the detected current value becomes a value including ripple. Therefore, when a filter is inserted on the output side of the current detector to remove the ripple, there is a problem that the control performance of the output current is deteriorated due to a detection delay time generated by the filter.
[0011]
Therefore, the present invention provides a large-sized AC-AC power conversion device having no filter as an energy buffer, by obtaining a sine wave having no distortion in an input current waveform and an output voltage waveform, so that a load such as a power supply system or a motor can be provided. It is an object of the present invention to provide an AC-AC power conversion device capable of detecting an output current without causing a failure and without delay in detection, thereby realizing high-performance control of a load such as an electric motor.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an invention according to claim 1 includes a PWM rectifier that converts polyphase AC power of a power supply into DC power, and a DC power output from the PWM rectifier through a DC link unit. An AC-AC power converter having a PWM inverter for converting to AC power, and not having a smoothing filter in the DC link unit.
On / off ratio extracting means for extracting a ratio of an on / off period of a switching phase of the PWM rectifier; and changing a peak position with respect to a carrier of the PWM rectifier based on the on / off period ratio; And a symmetrically deformed triangular wave generating means for generating a triangular wave symmetrical with respect to the peak position of the carrier as a carrier of the PWM inverter.
[0013]
The invention described in claim 2 is a virtual PWM rectifier that converts polyphase AC power of a power supply into DC power, and converts a DC power output from the PWM rectifier through a virtual DC link unit into a polyphase AC power. In an AC-AC power conversion device including a matrix converter having a virtual PWM inverter for converting power,
On / off ratio extracting means for extracting a ratio of an on / off period of a switching phase of the PWM rectifier; and changing a peak position with respect to a carrier of the PWM rectifier based on the on / off period ratio; And a symmetrically deformed triangular wave generating means for generating a triangular wave symmetrical with respect to the peak position of the carrier as a carrier of the PWM inverter.
[0014]
According to a third aspect of the present invention, in the AC-AC power converter according to the first or second aspect,
The PWM rectifier (including a virtual PWM rectifier in a matrix converter) is provided with a means for sampling a load current at a timing of a carrier peak.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In the main circuit shown in FIG. 1, reference numeral 10 denotes a current-type three-phase PWM rectifier (hereinafter, simply referred to as a rectifier) including semiconductor AC switches 11 to 16, and reference numeral 20 denotes an IGBT (insulated gate bipolar transistor) having a freewheeling diode. A three-phase voltage-type PWM inverter (hereinafter, also simply referred to as an inverter) including semiconductor switching elements 21 to 26, R, S, and T are AC input terminals, and U, V, and W are AC output terminals.
[0016]
On the other hand, in the control device for controlling the PWM rectifier 10 and the PWM inverter 20, 31 is a trapezoidal wave command generating means for generating a trapezoidal wave command based on the input current command on the rectifier 10 side, and 32 is a carrier (triangular wave) on the rectifier 10 side. , A comparison means for generating a PWM pulse by comparing the trapezoidal wave command with the carrier, and a gate for driving the AC switches 11 to 16 based on the PWM pulse from the comparison means 33. A gate pulse generating means for generating a pulse, 35 is an on / off ratio extracting means for extracting an on / off ratio of a switching phase of the rectifier 10 from the PWM pulse, and 41 is based on the on / off ratio and a carrier on the rectifier 10 side. , The peak of the carrier on the inverter 20 side is shifted, and the peak position of the carrier on the rectifier 10 side is shifted. A symmetrically deformed triangular wave generating means for generating a symmetrically deformed triangular wave as a carrier symmetric with respect to, a comparing means for comparing the symmetrically deformed triangular wave with an output voltage command on the inverter 20 side to generate a PWM pulse, and 43 a comparing means Gate pulse generating means for generating a gate pulse for driving the switching elements 21 to 26 based on the PWM pulse from 42.
In FIG. 1, i _dc and e _dc represent the current and voltage of the DC link unit.
[0017]
FIG. 2 shows the generation of the rectifier-side PWM pulse (only the R-phase pulse is shown) and the inverter-side PWM pulse of each phase when the symmetrically deformed triangular wave output from the generating means 41 is used as the carrier on the inverter 20 side. Is shown.
In this embodiment, the up / down pattern of the inverter-side carrier is switched according to the up / down (increase / decrease in size) of the rectifier-side carrier and the on / off ratio of the switching phase. Specifically, the ratio of the up / down period of the carrier on the inverter side is determined based on the duty ratio of the PWM pulse of the switching phase on the rectifier side. That is, up / down of the carrier on the inverter side is determined by the logic shown in Table 1.
[0018]
[Table 1]

[0019]
When the inverter-side carrier is generated based on Table 1, as shown in FIG. 2, the inverter-side carrier becomes a deformed triangular wave that is symmetric about the rectifier-side carrier's peak (peak, valley) position. As a result, the PWM pulse on the inverter 20 side is symmetric about the peak position of the rectifier-side carrier.
Therefore, if the output current (load current) of the power converter is sampled at the peak timing of the rectifier-side carrier, the average value of the load current can be obtained without taking any means such as providing a filter for removing ripples in the current detection unit. Can be detected without time delay, and the output current can be controlled with high accuracy.
[0020]
In the embodiment of FIG. 1, the on / off ratio extracting means 35 detects the on / off ratio (the ratio of T ₁ , T ₂ in FIG. 2) of the switching phase of the rectifier 10 (the R phase in the example of FIG. 2). The on / off ratio is input to the symmetrically deformed triangular wave generating means 41. The rectifier-side carrier output from the carrier generation means 32 is also input to the symmetrically deformed triangular wave generation means 41.
The symmetrically deformed triangular wave generating means 41 creates and outputs the inverter-side carrier (symmetrically deformed triangular wave) shown in FIG. 2 which increases or decreases according to the logic of Table 1 using the on / off ratio and the peak timing of the rectifier-side carrier.
The comparing means 42 compares the inverter-side carrier with the output voltage commands v _u ^* , v _v ^* , v _w ^{* of} each phase, and outputs U-phase, V-phase, and W-phase inverter-side PWM pulses.
[0021]
FIG. 3 is a block diagram showing a specific example of the symmetrically deformed triangular wave generating means 41 in FIG. 1 together with its peripheral components, and FIG.
Here, an example in which the symmetrically deformed triangular wave generating means 41 is configured by digital hardware is shown, but it is also possible to configure by an analog circuit, and the symmetrically deformed triangular wave may be created by software.
[0022]
In FIG. 3, reference numeral 411 denotes an exclusive OR (EX-OR) circuit, based on the up / down signal of the rectifier-side carrier and the PWM pulse of the rectifier-side, according to the logic of Table 1 described above. Outputs a down command. Here, the up signal of the rectifier side carrier is logic “1”, the down signal is logic “0”, the High of the rectifier side PWM pulse is logic “1”, the Low is logic “0”, and the up command of the inverter side carrier is logic “1”. “1” and the down command correspond to logic “0”, respectively.
[0023]
The up / down command of the inverter-side carrier output from the exclusive OR circuit 411 is added to the up / down counter 412. The up / down counter 412 counts up or down the peak value of the inverter side carrier in accordance with the up / down command in response to a counter load signal generated at the peak (peak, valley) of the rectifier side carrier, and counts the count value. As an inverter-side carrier (symmetrically deformed triangular wave).
[0024]
The clock of the up / down counter 412412 is constant, and the period for counting up or counting down depends on the duty ratio of the rectifier-side PWM pulse. Accordingly, as shown in FIG. 4, the peak value of the carrier on the inverter side differs depending on the High and Low of the PWM pulse on the rectifier side.
[0025]
Therefore, should the previously software calculates the voltage command va _n and the voltage command vb _n corrected in accordance with the peak value of the inverter side carrier from the original inverter output voltage command, respectively, is written to the voltage command register 422, 423 . Then, the selector 424 switches the voltage command to be compared by the comparator 421 in response to the peak value of the inverter-side carrier changing in accordance with the rectifier-side PWM pulse High and Low. Here, the selector 424 can recognize that the peak value of the inverter-side carrier changes based on the rectifier-side PWM pulse as shown in FIG.
Therefore, the voltage command output from the selector 424, as shown in FIG. 4, selects the output voltage command register 422 or 423 as rectifier side PWM pulse changes Low → High → Low → ......, va n- _{1 → va n → vb n →} vb n + 1 → va n + 1 → ...... and will change.
[0026]
By comparing the output voltage command selected by the selector 424 with the inverter-side carrier in the comparator 421 in this way, a PWM pulse on the inverter 20 side is obtained.
The peak value of the carrier on the inverter side is calculated by software, and the obtained peak value is loaded into the up / down counter 412 at the peak and valley of the carrier on the rectifier side by a counter load signal.
[0027]
Next, FIG. 5 is a configuration diagram showing a second embodiment of the present invention. In this embodiment, a matrix converter 50 is used as a power converter of a main circuit. The matrix converter 50 is configured by connecting bidirectional switches 51 to 59 between input terminals R, S, T and output terminals U, V, W. Each of the switches 51 to 59 is, for example, an IGBT or the like. The two semiconductor switching elements are connected in series in the reverse direction, and a circulating diode is connected to each switching element in antiparallel.
The configuration of the control device is substantially the same as that of FIG. 1. PWM pulse synthesizing means 60 is provided in place of gate pulse generating means 34 and 43 in FIG. Has been given.
[0028]
In controlling the matrix converter 50, a PWM rectifier and a PWM inverter having the same configuration as the PWM rectifier 10 and the PWM inverter 20 in FIG. 1 are imagined in the matrix converter 50, and a PWM pulse (switching function) for the virtual rectifier and the virtual inverter is used. ) Are synthesized by the synthesizing means 60 to control the matrix converter 50 (for example, “Non-interference control method of input / output reactive power in a matrix converter”, Rie Itoh / Isao Takahashi, IEEJ Semiconductor Power Converter) See Study Group SPC-01-121, IEA-01-64).
[0029]
That is, the power conversion operation of the matrix converter 50 is represented by the following Equation 1. Incidentally, in Equation _{1, v u, v v,} v w are output phase _{voltage, v r, v s, v} t is the input phase _voltages, S 51 _{to S 59} is the switching function of the bidirectional switch 51 to 59.
[0030]
(Equation 1)

[0031]
Further, the switching functions S _{51 to} S ₅₉ can be expressed as Expression 2 using the switching function on the virtual rectifier side and the switching function on the virtual inverter side.
[0032]
(Equation 2)

[0033]
Therefore, in the present embodiment, the switching function on the virtual rectifier side based on the PWM pulse from the comparing unit 33 in FIG. 5 and the switching function on the virtual inverter side based on the PWM pulse from the comparing unit 42 using the symmetrically deformed triangular wave are used. Then, the PWM pulse synthesizing means 60 calculates the switching function according to Equation 2, and controls the bidirectional switches 51 to 59 on and off according to the switching function.
In this case, the operation on the virtual rectifier side is equivalent to the operation of the current-type PWM rectifier because the power supply short circuit is not allowed.
[0034]
In this embodiment, the symmetrically deformed triangular wave generator 41 changes the peak position with respect to the virtual rectifier carrier based on the on / off ratio of the switching phase of the virtual rectifier in the matrix converter 50, and sets the virtual rectifier carrier A symmetrical deformed triangular wave that is symmetrical with respect to the peak position is generated, and the comparing unit 42 compares the deformed triangular wave with the output voltage command of each phase to determine a period in which the virtual DC link section current is zero. A PWM pulse is generated on the inverter side so as to be evenly arranged with respect to the phase current.
The operation of generating the PWM pulse on the virtual rectifier side is the same as that of the first embodiment, and thus the description is omitted.
[0035]
The present invention is also applicable to the mutual conversion of polyphase alternating currents other than the three-phase described in each embodiment.
[0036]
【The invention's effect】
As described above, according to the present invention, in an AC-AC power converter that does not have a large energy buffer, by obtaining a sine wave having no distortion in the input current waveform and the output voltage waveform, the power supply system and the motor can be used. A small-sized and long-life power converter that does not impair the load can be provided.
In particular, if the load current is detected at the peak timing of the rectifier carrier, the average value of the load flow can be detected without detection delay, and high-precision current control becomes possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is an operation explanatory diagram of the first embodiment.
FIG. 3 is a block diagram showing a specific example of a symmetrically deformed triangular wave generator in FIG.
FIG. 4 is an operation explanatory diagram of FIG. 3;
FIG. 5 is a configuration diagram showing a second embodiment of the present invention.
FIG. 6 is an explanatory diagram of a PWM pulse generation method of the prior application.
[Explanation of symbols]
10: PWM rectifiers 11 to 16: semiconductor AC switches 20: PWM inverters 21 to 26: semiconductor switching elements 31: trapezoidal wave command generating means 32: carrier generating means 33, 42: comparing means 34, 43: gate pulse generating means 35: On / off ratio extracting means 41: symmetrically deformed triangular wave generating means 411: exclusive OR circuit 412: up / down counter 421: comparators 422, 423: voltage command register 424: selector 50: matrix converters 51 to 59: bidirectional switch 60: PWM pulse synthesis means R, S, T: AC input terminals U, V, W: AC output terminals

Claims (3)

A PWM rectifier that converts polyphase AC power of a power supply into DC power, and a PWM inverter that converts DC power output from the PWM rectifier through a DC link unit to polyphase AC power, and In an AC-AC power converter that does not have a smoothing filter in the link unit,
On / off ratio extracting means for extracting a ratio of an on / off period of a switching phase of the PWM rectifier;
A symmetry that changes a peak position with respect to the carrier of the PWM rectifier based on the ratio of the on / off period and generates a triangular wave that is symmetric with respect to the peak position of the carrier of the PWM rectifier as a carrier of the PWM inverter. Deformed triangular wave generating means,
An AC-AC power converter, comprising: A virtual PWM rectifier for converting polyphase AC power of a power supply to DC power, and a virtual PWM inverter for converting DC power output from the PWM rectifier via a virtual DC link unit to polyphase AC power An AC-AC power conversion device comprising a matrix converter having
On / off ratio extracting means for extracting a ratio of an on / off period of a switching phase of the PWM rectifier;
A symmetry that changes a peak position with respect to the carrier of the PWM rectifier based on the ratio of the on / off period and generates a triangular wave that is symmetric with respect to the peak position of the carrier of the PWM rectifier as a carrier of the PWM inverter. Deformed triangular wave generating means,
An AC-AC power converter, comprising: The AC-AC power converter according to claim 1 or 2,
An AC-AC power converter, comprising: means for sampling a load current at a peak timing of a carrier of the PWM rectifier.

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