JP4029284B2 - AC-AC power converter controller - Google Patents

Description

【００２０】
また、電力変換器から出力される対称三相正弦波電流を瞬時空間ベクトルにて表すと、数式２となる。なお、数式２において、Ｉ_ｍｏｕｔは出力電流の振幅、φは位相角である。
【００２１】
【数２】

【００２２】
従って、数式１，数式２から、瞬時有効電力は数式３となる。この結果、電力変換器の出力側の瞬時有効電力は一定であることがわかる。
【００２３】
【数３】

【００２４】
一方、入力電圧にｎ次高調波が重畳されている場合、入力電圧ベクトルは数式４となる。なお、数式４において、Ｖ_ｍｉｎは入力電圧の振幅、Ｖ_ｎｉｎは入力電圧のｎ次高調波成分の振幅、ζ＝ωｔ、βは位相角である。
【００２５】
【数４】

【００２６】
このとき、入力電流として対称三相交流電流を流した場合、入力電流ベクトルは数式５で表されると共に、数式４，数式５から、瞬時有効電力は数式６となる。数式５において、ρは位相角を示し、数式６において、Ｒｅは実数部を示す。
【００２７】
【数５】

【００２８】
【数６】

【００２９】
前述した数式３は出力側の瞬時有効電力であり、数式６は入力側の瞬時有効電力である。エネルギー保存の法則から、エネルギーバッファのない電力変換器では、入力側と出力側の瞬時有効電力を一致させる必要がある。
しかし、数式６は右辺第２項にζを含んでいることから脈動分を持っており、入力電圧に高調波成分を含んでいる場合には入力電流と出力電圧とを対称三相正弦波とすることは物理的に不可能である。
【００３０】
数式３と数式６を一致させるためには、入力電流または出力電圧のいずれかもしくはその両方を歪ませることにより、数式６の第２項を打ち消す必要がある。電力変換器に電動機等が接続されている場合、出力電圧をひずませて高調波が含まれると、電動機にトルクリプルを生じ、騒音が発生するので好ましくない。
そこで、入力側の瞬時有効電力が一定になるように、入力電流指令に高調波成分を重畳して数式７により制御することとした。
【００３１】
【数７】

【００３２】
ここで、入力側の瞬時有効電力を求めると、数式８となる。
【００３３】
【数８】

【００３４】
数式８右辺第４項は、入力電圧及び入力電流の高調波成分によって生じる瞬時有効電力であり、ζに対し、定数項Ｃ及び高調波次数ｎに応じた変動項ｆ（ｎζ）によって表すことができるので、数式８は数式９となる。
【００３５】
【数９】

【００３６】
数式９において、右辺第１項と第４項は定数項であり、一定である。瞬時有効電力の脈動は、ζを含む右辺第２項、第３項及び第５項により発生する。従って、瞬時有効電力を一定とするためには、数式１０を満たす高調波成分ΣＩ_ｎｉｎｅ^{ｊｋｎ（ζ＋ρ）}を入力電流指令に重畳すればよい。
【００３７】
【数１０】

【００３８】
なお、スイッチングを伴う電力変換器では有効電力は入力側から出力側に伝達されるが、無効電力は電力変換器の還流モードにより発生する。これは従来の直流−交流電力変換器（インバータ）を考えれば、明らかである。インバータの入力は直流であるから、瞬時電力はすべて瞬時有効電力である。
しかし、インバータの出力側では負荷に応じて無効電力が発生し、瞬時有効電力の他に、負荷に応じた瞬時無効電力が発生している。従って、入力側の電流波形を変化させ、入出力の瞬時有効電力を一致させることで、大容量のエネルギーバッファがない場合でも出力側に一定の瞬時有効電力を取り出すことができる。
【００３９】
図１において、電圧検出手段２００は数式４に基づいて入力電圧ｖ_ｉｎを検出し、瞬時有効電力一定化手段３００は、Ｖ_ｍｉｎ，Ｖ_ｎｉｎ，ζ，β，ｎ（高調波次数）を用いて数式１０を満たす入力電流の高調波成分ΣＩ_ｎｉｎｅ^{ｊｋｎ（ζ＋ρ）}を算出する。そして、入力電流指令発生手段４００は、数式５で示される入力電流基本波指令に前記高調波成分ΣＩ_ｎｉｎｅ^{ｊｋｎ（ζ＋ρ）}を重畳し、数式７により交流−交流電力変換器１００に与える入力電流指令ｉ_ｉｎを生成して出力する。
これにより、入力側の瞬時有効電力が一定に制御され、電力変換器１００の出力電圧波形を歪みのない正弦波にすることができる。
【００４０】
次に、図２は本発明の第２実施形態を示すブロック図である。
この実施形態では、交流−交流電力変換器として、入力電流を制御する電流形ＰＷＭ整流器２０と電圧形ＰＷＭインバータ４０とがフィルタなしに直接接続されており、整流器制御手段５０は、入力電流指令に応じた入力電流を流すように整流器２０を制御し、インバータ制御手段６０は、出力電圧指令に従った電圧を出力するべくインバータ４０を制御するように構成されている。２１〜２６は交流スイッチ、４１〜４６は半導体スイッチング素子である。
【００４１】
また、三相交流電源１０には電圧検出手段２００が接続され、その出力は基本波検出手段３１０及び高調波検出手段３２０に加えられていると共に、これらの検出手段３１０，３２０の出力は、入力電流基本波指令と一緒に高調波電流指令演算手段３３０に加えられている。そして、高調波電流指令演算手段３３０から出力される高調波電流指令は入力電流基本波指令と加算手段４１０により加算され、その加算結果が入力電流指令として整流器制御手段５０に入力されている。
【００４２】
本実施形態では、以下の理由により、入力電圧に含まれる５次高調波と７次高調波について補償を行うものとする。
（１）数式１０は比較的複雑であり、すべての次数の高調波について補償するためには演算量が多くなるため高速の制御装置が必要である。
（２）負荷が電動機の場合、入力電圧の高次高調波は漏れインダクタンスにより平滑され、電流に現れる影響は小さくなる。
（３）加えて、高周波のトルクリプルは電動機の慣性モーメントに吸収されるため、回転ムラとしては現れず、問題にならない。
（４）電源電圧高調波に最も多く含まれるのは、一般に５次、７次である。また、高次高調波は入力フィルタを設けることで減衰させることができる。
【００４３】
そこで、数式１０に基づき、入力電圧に５次高調波と７次高調波が含まれる場合について瞬時有効電力ｐ_ｉｎを求めると、数式１１となる。なお、数式１１において、Ｖ_５ｉｎ，Ｖ_７ｉｎは５次高調波、７次高調波の電圧振幅、Ｉ_５ｉｎ，Ｉ_７ｉｎは５次高調波、７次高調波の電流振幅である。
【００４４】
【数１１】

【００４５】
数式１１の右辺第３項以降が、ζによる変動項である。入力力率を１とし（β＝ρ）、数式１１の右辺第３項以降をゼロとするためには、数式１２が成立すればよい。
【００４６】
【数１２】

【００４７】
数式１２により、入力電流基本波指令に重畳する５次高調波、７次高調波の電流振幅は数式１３となる。
【００４８】
【数１３】

【００４９】
図２では、入力電圧を電圧検出手段２００により検出し、基本波検出手段３１０により、基本波の電圧振幅Ｖ_ｍを抽出し、高調波検出手段３２０により５次、７次高調波の電圧振幅Ｖ_５ｉｎ，Ｖ_７ｉｎを検出する。高調波電流指令演算手段３３０では数式１３の演算により５次、７次高調波電流の振幅Ｉ_５ｉｎ，Ｉ_７ｉｎを求め、これらを加算手段４１０により入力電流の基本波指令（振幅指令）に加算して整流器制御手段５０に与える入力電流指令を得る。
【００５０】
図３は、この実施形態によるシミュレーション結果を示す入力電圧波形及び出力電圧波形であり、図７の場合と同様に、入力電圧には５次高調波が５％、７次高調波が２．５％含まれている場合である。入力電流に５次、７次高調波電流を重畳することにより、入力側の瞬時有効電力を一定にし、入力電流波形及び出力電圧波形を歪みのない正弦波にすることができる。
【００５１】
次に、図４は本発明の第３実施形態を示す構成図であり、この実施形態では、主変換器としてマトリクスコンバータ９０を用いている。
このマトリクスコンバータ９０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９１〜９９を接続して構成されており、各スイッチ９１〜９９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。
【００５２】
上記マトリクスコンバータ９０の制御に当たっては、図２におけるＰＷＭ整流器２０、ＰＷＭインバータ４０と同様な構成のＰＷＭ整流器、ＰＷＭインバータを仮想し、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）を整流器制御手段５０及びインバータ制御手段６０により作成すると共に、これらのパルスをＰＷＭパルス合成手段７０により合成してマトリクスコンバータ９０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）。
【００５３】
ここで、マトリクスコンバータ９０の電力変換動作は、以下の数式１４によって表される。なお、数式１４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_９１〜Ｓ_９９は双方向スイッチ９１〜９９のスイッチング関数である。
【００５４】
【数１４】

【００５５】
また、上記スイッチング関数Ｓ_９１〜Ｓ_９９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１５のように表すことができる。
【００５６】
【数１５】

【００５７】
図４におけるＰＷＭパルス合成手段７０は、整流器制御手段５０からのスイッチング関数とインバータ制御手段６０からのスイッチング関数とを用いて数式１４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マトリクスコンバータ９０内の双方向スイッチ９１〜９９をオンオフ制御する。
なお、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。
【００５８】
本実施形態では、マトリクスコンバータ９０の入力電圧に高調波が含まれる場合でも、仮想整流器に対する入力電流指令を得るために基本波電流指令に数式１３の高調波電流指令を重畳することにより、入力側の瞬時有効電力が一定となるように制御を行い、入力電流波形及び出力電圧波形の歪みを低減することができる。ここで、図４における各手段２００，３１０，３２０，３３０，４１０の動作は第２実施形態と同様であるため、詳述を省略する。
【００５９】
次いで、図５は本発明の第４実施形態を示すブロック図である。この実施形態では、瞬時有効電力を一定にする演算を簡単に行うため、入力電流基本波指令に重畳する高調波成分を調節器により得るようにした。
【００６０】
すなわち、図５において、交流−交流電力変換器１００の出力側には電流検出手段３４０が接続されており、この検出手段３４０により出力電流を検出し、出力電圧指令と出力電流とから出力側の瞬時有効電力を瞬時有効電力演算手段３５０により演算する。
脈動分検出手段３６０は、演算した瞬時有効電力の脈動分を検出する。瞬時有効電力の脈動を、入力電流の基本波の振幅指令に高調波成分を重畳することにより抑制できることは、各実施形態で説明したとおりである。
従って、脈動分検出手段３６０の出力とゼロが図示の符号で入力される加算器３７０と調節器３８０とを設けることにより、調節器３８０の出力が瞬時有効電力を一定にするような高調波成分となる。この高調波成分を入力電流基本波指令に加算することにより、電力変換器１００の出力側の瞬時有効電力を一定にして出力電圧波形を正弦波に制御することができる。
ここで、調節器３８０には、例えば比例調節器、比例積分調節器等を用いることができる。
【００６１】
なお、瞬時有効電力は、出力電圧指令から演算する以外に、図示されていない出力電圧検出手段を設けて出力電流及び出力電圧の各検出値から求めても良いし、電力変換器１００の入力側に電流検出手段を設け、入力電圧と入力電流とから求めても良い。
更に、この実施形態は図２の回路にも適用可能であり、直流リンク部に直流電圧検出手段及び直流電流検出手段を設け、直流リンク部の瞬時電力を求めてもよい。
また、この実施形態は、図４に示した回路にも適用可能であり、その場合には、マトリクスコンバータ９０の瞬時有効電力を検出し、その脈動成分をゼロにするように調節動作する調節器の出力を入力電流基本波指令に重畳して整流器制御手段５０に加えれば良い。この場合の瞬時有効電力も、出力電流及び出力電圧の各検出値、入力電流及び入力電圧の各検出値等から求めることができる。
【００６２】
また、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。
【００６３】
【発明の効果】
以上のように本発明によれば、直流リンク部に大容量のエネルギーバッファを持たずに整流器及びインバータから構成される電力変換器や、マトリクスコンバータ等の交流−交流直接変換形電力変換器において、入力電圧に高調波が含まれる場合でも、出力電圧波形として歪みのない正弦波を得ることができる。
この結果、小形、長寿命であり、電動機等の負荷の運転に障害を与えない交流−交流電力変換器を提供することができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示すブロック図である。
【図２】本発明の第２実施形態を示すブロック図である。
【図３】第２実施形態によるシミュレーション結果を示す入力電圧波形及び出力電圧波形である。
【図４】本発明の第３実施形態を示すブロック図である。
【図５】本発明の第４実施形態を示すブロック図である。
【図６】従来技術を示すブロック図である。
【図７】従来技術における入力電圧波形及び出力電圧波形である。
【符号の説明】
１０：三相交流電源
２０：電流形ＰＷＭ整流器
２１〜２６：交流スイッチ
４０：電圧形ＰＷＭインバータ
４１〜４６：半導体スイッチング素子
５０：整流器制御手段
６０：インバータ制御手段
７０：ＰＷＭパルス合成手段
１００：交流−交流電力変換器
１１０：マトリクスコンバータ
１１１〜１１９：双方向スイッチ
２００：電圧検出手段
３００：瞬時有効電力一定化手段
３１０：基本波検出手段
３２０：高調波検出手段
３３０：高調波電流指令演算手段
３４０：電流検出手段
３５０：瞬時有効電力演算手段
３６０：脈動分検出手段
３７０，４１０：加算手段
４００：入力電流指令発生手段
Ｒ，Ｓ，Ｔ：交流入力端子
Ｕ，Ｖ，Ｗ：交流出力端子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an AC-AC power converter that outputs a multi-phase AC voltage from a multi-phase AC voltage using a semiconductor switching element, particularly in an AC-AC power converter that does not have a large-capacity energy buffer. The present invention relates to a control device for performing harmonic compensation for reducing distortion of an output voltage waveform when the input voltage includes harmonics.
[0002]
[Prior art]
FIG. 6 shows a configuration of a conventional AC-AC power converter using an AC-DC-AC conversion system (converter-inverter system). Here, the most common three phases are illustrated as examples of polyphase on the input side and output side, and the phases on the input side (power supply side) are R, S, T phases, and the output side (load side). Each phase shall be called U, V, W phase.
[0003]
In FIG. 6, 20 is a three-phase current source PWM rectifier composed of AC switches 21 to 26, 40 is a three-phase voltage source PWM inverter composed of semiconductor switching elements 41 to 46 such as IGBTs having freewheeling diodes, and 30 is a rectifier 20. Connected to the DC link section between the inverter 40 and the inverter 31, and a filter comprising a reactor 31 and a capacitor 32, 50 is a rectifier control means for controlling on / off of the AC switches 21 to 26 in the rectifier 20, and 60 is an inverter 40 It is an inverter control means which controls ON / OFF of the switching elements 41-46 in the inside.
[0004]
In the above prior art, a DC voltage of a desired magnitude is obtained while controlling the input current by the rectifier 20 in accordance with the input current command, and this DC voltage is input to the inverter 40 to obtain the desired magnitude and the output voltage command. It is converted into a three-phase AC voltage having a frequency and output.
Here, the reactor 31 and the capacitor 32 constituting the filter 30 function as a large-capacity energy buffer, and the rectifier 20 and the inverter 40 can be independently controlled by the energy buffer.
[0005]
The rectifier 20 is controlled by comparing the input current command and the carrier waveform by the rectifier control means 50, obtaining a PWM command based on the magnitude relationship, and generating control pulses for the AC switches 21 to 26.
Similarly, the inverter control means 60 compares the output voltage command and the carrier waveform on the inverter 40 side, obtains a PWM command based on the magnitude relationship, and generates control pulses for the switching elements 41 to 46.
[0006]
In the above prior art, even if a harmonic component is included in the input voltage, the harmonic component is smoothed by the filter 30, so that the influence does not appear on the output side.
That is, in the circuit of FIG. 6, even when a harmonic component is superimposed on the input voltage, the output voltage can be controlled to a desired magnitude and frequency, and a good waveform can be obtained.
[0007]
Various converter-inverter AC-AC power converters as shown in FIG. 6 have been conventionally provided. For example, there is one described in Patent Document 1 below.
[0008]
[Patent Literature]
JP-A-11-299290 (FIG. 1, [0018], [0019], etc.)
[0009]
[Problems to be solved by the invention]
As the smoothing capacitor described in the capacitor 32 and Patent Document 1, an electrolytic capacitor is usually used. However, since the electrolytic capacitor has a large outer shape and a short life, it is possible to reduce the size and the life of the device. It is a hindrance. Furthermore, the reactor 31 that constitutes the filter 30 together with the capacitor 32 is also large, which hinders downsizing.
That is, if the filter 30 inserted in the DC link portion is removed, the apparatus can be reduced in size and extended in life, so that it is required to realize a power converter that does not have the filter 30.
[0010]
Here, FIG. 7 shows that the harmonic component (5th harmonic is 5%, 7th harmonic is 2.5%) in the input voltage when the filter 30 of the DC link unit is removed from the configuration of FIG. When included, an input voltage waveform and an output voltage waveform are displayed in a unit method.
When harmonic components are included in the input voltage as shown in FIG. 7, when the input current is controlled to a sine wave, the active power pulsates and a ripple appears in the voltage of the DC link unit. When there is a large-capacity energy buffer as in the conventional filter 30, the active power pulsation on the input side can be absorbed by the energy buffer. However, in a power converter that does not have a large-capacity energy buffer, As a result, the output voltage waveform is distorted as shown in FIG. When the electric motor is connected as a load of the AC-AC power converter, the distortion of the output voltage not only causes torque vibration and noise of the electric motor, but also increases copper loss due to harmonic current and decreases efficiency. It will be.
[0011]
Therefore, the present invention provides a harmonic component in the input voltage in the case of power converters that do not have a large-capacity energy buffer in the DC link unit, or when AC-AC direct conversion is performed without using an energy buffer such as a matrix converter. By providing a sine wave without distortion in the output voltage waveform even when included, provide a control device for an AC-AC power converter that is small and has a long life and does not interfere with the operation of a load such as an electric motor. It is what.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an invention according to claim 1 is an AC-AC power converter that converts a polyphase AC voltage to a polyphase AC voltage without having an energy buffer in the DC link unit.
Voltage detecting means for detecting the input voltage of the power converter, and an instantaneous for calculating the harmonic component of the input current such that the instantaneous active power on the input side becomes constant according to the input voltage detected by the voltage detecting means An active power stabilizing means; an input current command generating means for generating an input current command to be applied to the power converter by superimposing a harmonic component calculated by the stabilizing means on an input current fundamental wave command;
It is equipped with.
[0013]
The invention according to claim 2 is an AC-AC power converter control comprising: a rectifier that converts a polyphase AC voltage into a DC voltage; and an inverter that converts a DC voltage output from the rectifier into a polyphase AC voltage. A control device comprising: a rectifier control means for controlling a rectifier given an input current command of the rectifier; and an inverter control means for controlling the inverter.
Voltage detection means for detecting the input voltage of the rectifier, fundamental wave detection means and harmonic detection means for detecting fundamental wave components and harmonic components of the input voltage detected by the voltage detection means, and detection of these fundamental waves The harmonics such that the instantaneous active power on the input side becomes constant using the amplitude of the fundamental component and the harmonic component of the input voltage detected by the means and the harmonic detection means, and the input current fundamental wave command. The harmonic current command calculation means for calculating the harmonic component of the input current of the same order as the component and outputting it as a harmonic current command, and superimposing the harmonic current command on the input current fundamental wave command to the power converter Means for generating an input current command to be applied;
It is equipped with.
[0014]
The invention described in claim 3 is the one in which the characteristic configuration of the invention of claim 2 is applied to a matrix converter, and includes a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage using a virtual rectifier and a virtual inverter. A control device for an AC-AC power converter, wherein a rectifier control means for outputting a control pulse of the virtual rectifier in response to an input current command of the virtual rectifier, and an inverter control means for outputting a control pulse of the virtual inverter And a pulse synthesizing unit that synthesizes a control pulse of the virtual rectifier and a control pulse of the virtual inverter and gives the matrix converter, a control device comprising:
Voltage detection means for detecting the input voltage of the virtual rectifier, fundamental wave detection means and harmonic detection means for detecting fundamental wave components and harmonic components of the input voltage detected by the voltage detection means, and these fundamental waves The harmonics such that the instantaneous active power on the input side becomes constant using the amplitude of the fundamental component and the harmonic component of the input voltage detected by the detection means and the harmonic detection means, and the input current fundamental wave command. A harmonic current command calculating means for calculating a harmonic component of the input current of the same order as the wave component and outputting it as a harmonic current command, and the rectifier control means for superimposing the harmonic current command on the input current fundamental wave command Means for generating an input current command to be applied to
It is equipped with.
[0015]
According to a fourth aspect of the present invention, there is provided an AC-AC power converter control comprising: a rectifier that converts a multiphase AC voltage into a DC voltage; and an inverter that converts a DC voltage output from the rectifier into a multiphase AC voltage. A control device comprising: a rectifier control means for controlling a rectifier given an input current command of the rectifier; and an inverter control means for controlling the inverter.
Means for determining the instantaneous active power of the power converter, means for detecting the pulsation of the instantaneous active power obtained by the means, adjustment means for adjusting the pulsation obtained by the means to zero, and Means for generating an input current command to be applied to the rectifier by superimposing an output on an input current fundamental wave command;
It is equipped with.
[0016]
The invention described in claim 5 is obtained by applying the characteristic configuration of the invention of claim 4 to a matrix converter, and includes a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage using a virtual rectifier and a virtual inverter. A control device for an AC-AC power converter, wherein a rectifier control means for outputting a control pulse of the virtual rectifier in response to an input current command of the virtual rectifier, and an inverter control means for outputting a control pulse of the virtual inverter And a pulse synthesizing unit that synthesizes a control pulse of the virtual rectifier and a control pulse of the virtual inverter and gives the matrix converter, a control device comprising:
Means for obtaining the instantaneous active power of the matrix converter, means for detecting the pulsation of the instantaneous active power obtained by this means, adjustment means for adjusting the pulsation obtained by this means to zero, and the output of this adjustment means Generating an input current command that is superimposed on the input current fundamental wave command and applied to the virtual rectifier;
It is equipped with.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of the present invention. In this embodiment, the AC-AC power converter 100 that does not have a large-capacity energy buffer, the voltage detection means 200 that detects the input voltage from the three-phase AC power supply 10, and the instantaneous effective power on the input side are constant. In this way, the instantaneous active power stabilizing means 300 that performs the control and the harmonic component of the input current obtained by the instantaneous active power stabilizing means 300 are superimposed on the input current fundamental wave command, and the input current command of the power converter 100 And an input current command generating means 400 for generating.
The AC-AC power converter 100 includes a current source PWM rectifier 20 and a voltage source PWM inverter 40 as shown in FIG. 6, for example, and a DC link unit includes a filter including a reactor and a capacitor. There is no energy buffer.
[0018]
Hereinafter, in this embodiment, the principle that the output voltage waveform is improved by controlling the input current so that the instantaneous active power on the input side becomes constant will be described.
This type of AC-AC power converter outputs an AC voltage having a desired magnitude and frequency from an AC input voltage. When the symmetric three-phase AC voltage v _out output from the power converter is represented by an instantaneous space vector, Equation 1 is obtained. In Equation 1, V _mout is the amplitude of the output voltage, θ = ωt, and α is the phase angle.
[0019]
[Expression 1]

[0020]
Further, when the symmetrical three-phase sine wave current output from the power converter is represented by an instantaneous space vector, Equation 2 is obtained. In Equation 2, I _mout is the amplitude of the output current, and φ is the phase angle.
[0021]
[Expression 2]

[0022]
Therefore, from the formulas 1 and 2, the instantaneous active power is given by the formula 3. As a result, it can be seen that the instantaneous effective power on the output side of the power converter is constant.
[0023]
[Equation 3]

[0024]
On the other hand, when the nth-order harmonic is superimposed on the input voltage, the input voltage vector is expressed by Equation 4. In Equation 4, V _min is the amplitude of the input voltage, V _nin is the amplitude of the nth-order harmonic component of the input voltage, and ζ = ωt, β is the phase angle.
[0025]
[Expression 4]

[0026]
At this time, when a symmetric three-phase alternating current is passed as the input current, the input current vector is expressed by Formula 5, and the instantaneous active power is expressed by Formula 6 from Formula 4 and Formula 5. In Equation 5, ρ represents a phase angle, and in Equation 6, Re represents a real part.
[0027]
[Equation 5]

[0028]
[Formula 6]

[0029]
Formula 3 described above is the instantaneous active power on the output side, and Formula 6 is the instantaneous active power on the input side. From the law of conservation of energy, it is necessary for the power converter without an energy buffer to match the instantaneous active power on the input side and output side.
However, since Equation 6 includes ζ in the second term on the right side, it has pulsation, and when the input voltage includes a harmonic component, the input current and the output voltage are converted into a symmetric three-phase sine wave. It is physically impossible to do.
[0030]
In order to make Formula 3 and Formula 6 coincide, it is necessary to cancel the second term of Formula 6 by distorting either or both of the input current and the output voltage. When an electric motor or the like is connected to the power converter, if the output voltage is distorted and harmonics are included, torque ripple is generated in the electric motor and noise is generated, which is not preferable.
Therefore, control is performed using Equation 7 by superimposing a harmonic component on the input current command so that the instantaneous active power on the input side is constant.
[0031]
[Expression 7]

[0032]
Here, when the instantaneous active power on the input side is obtained, Equation 8 is obtained.
[0033]
[Equation 8]

[0034]
The fourth term on the right side of Equation 8 is the instantaneous active power generated by the harmonic components of the input voltage and input current, and can be expressed by a constant term C and a fluctuation term f (nζ) corresponding to the harmonic order n with respect to ζ. Since this is possible, Equation 8 becomes Equation 9.
[0035]
[Equation 9]

[0036]
In Equation 9, the first and fourth terms on the right side are constant terms and are constant. The pulsation of the instantaneous effective power is generated by the second term, the third term, and the fifth term on the right side including ζ. Therefore, in order to make the instantaneous active power constant, the harmonic component ΣI _nin e ^{jkn (ζ + ρ)} satisfying Equation 10 may be superimposed on the input current command.
[0037]
[Expression 10]

[0038]
In a power converter with switching, active power is transmitted from the input side to the output side, but reactive power is generated by the return mode of the power converter. This is apparent when considering a conventional DC-AC power converter (inverter). Since the input of the inverter is DC, all instantaneous power is instantaneous active power.
However, reactive power is generated according to the load on the output side of the inverter, and instantaneous reactive power according to the load is generated in addition to the instantaneous active power. Therefore, by changing the current waveform on the input side to match the instantaneous active power of input and output, a constant instantaneous active power can be taken out on the output side even when there is no large-capacity energy buffer.
[0039]
In Figure 1, the voltage detecting means 200 detects an input voltage _{v in,} based on Equation 4, the instantaneous active power constant means _{300, V min, V nin, ζ} , β, with n (harmonic order) The harmonic component ΣI _nin e ^{jkn (ζ + ρ)} of the input current that satisfies Equation 10 is calculated. Then, the input current command generation means 400 superimposes the harmonic component ΣI _nin e ^{jkn (ζ + ρ)} on the input current fundamental wave command shown in Equation 5, and the input current given to the AC-AC power converter 100 by Equation 7 A command i _in is generated and output.
Thereby, the instantaneous active power on the input side is controlled to be constant, and the output voltage waveform of the power converter 100 can be made a sine wave without distortion.
[0040]
Next, FIG. 2 is a block diagram showing a second embodiment of the present invention.
In this embodiment, as an AC-AC power converter, a current source PWM rectifier 20 for controlling an input current and a voltage source PWM inverter 40 are directly connected without a filter, and the rectifier control means 50 is provided with an input current command. The rectifier 20 is controlled so as to cause a corresponding input current to flow, and the inverter control means 60 is configured to control the inverter 40 so as to output a voltage according to the output voltage command. 21 to 26 are AC switches, and 41 to 46 are semiconductor switching elements.
[0041]
The three-phase AC power supply 10 is connected to a voltage detection means 200, and its output is applied to the fundamental wave detection means 310 and the harmonic detection means 320, and the outputs of these detection means 310 and 320 are input. It is added to the harmonic current command calculation means 330 together with the current fundamental wave command. The harmonic current command output from the harmonic current command calculation unit 330 is added by the input current fundamental wave command and the adding unit 410, and the addition result is input to the rectifier control unit 50 as an input current command.
[0042]
In the present embodiment, it is assumed that the fifth harmonic and the seventh harmonic included in the input voltage are compensated for the following reason.
(1) Equation 10 is relatively complex, and a high-speed control device is required because the amount of calculation increases in order to compensate for harmonics of all orders.
(2) When the load is an electric motor, the higher harmonics of the input voltage are smoothed by the leakage inductance, and the effect of appearing on the current is reduced.
(3) In addition, since the high-frequency torque ripple is absorbed by the moment of inertia of the electric motor, it does not appear as rotation unevenness and does not cause a problem.
(4) In general, the fifth and seventh orders are the most contained in the power supply voltage harmonics. Further, high-order harmonics can be attenuated by providing an input filter.
[0043]
Therefore, based on Equation 10, when determining the instantaneous active power p _in the case including the fifth harmonic and seventh harmonic of the input voltage, the equation 11. In Equation 11, V _5in and V _7in are the voltage amplitudes of the fifth harmonic and the seventh harmonic, and I _5in and I _7in are the current amplitudes of the fifth harmonic and the seventh harmonic.
[0044]
## EQU11 ##

[0045]
The third and subsequent terms on the right side of Equation 11 are variation terms due to ζ. In order to set the input power factor to 1 (β = ρ) and set the third and subsequent terms on the right side of Formula 11 to zero, Formula 12 may be satisfied.
[0046]
[Expression 12]

[0047]
According to Equation 12, the current amplitudes of the fifth harmonic and the seventh harmonic superimposed on the input current fundamental wave command become Equation 13.
[0048]
[Formula 13]

[0049]
In FIG. 2, the input voltage is detected by the voltage detection means 200, the fundamental wave detection means 310 extracts the fundamental voltage amplitude V _m , and the harmonic detection means 320 extracts the fifth and seventh harmonic voltage amplitudes V _{m. 5in} and _V7in are detected. In the harmonic current command calculation means 330, the amplitudes I _5in and I _7in of the fifth and seventh harmonic currents are obtained by the calculation of Equation 13, and these are added to the fundamental wave command (amplitude command) of the input current by the addition means 410. Thus, an input current command to be given to the rectifier control means 50 is obtained.
[0050]
FIG. 3 shows an input voltage waveform and an output voltage waveform showing simulation results according to this embodiment. As in the case of FIG. 7, the input voltage has a 5th harmonic of 5% and a seventh harmonic of 2.5%. % Is included. By superimposing the fifth and seventh harmonic currents on the input current, the instantaneous active power on the input side can be made constant, and the input current waveform and the output voltage waveform can be made sine waves without distortion.
[0051]
Next, FIG. 4 is a block diagram showing a third embodiment of the present invention. In this embodiment, a matrix converter 90 is used as a main converter.
This matrix converter 90 is configured by connecting bidirectional switches 91-99 between input terminals R, S, T and output terminals U, V, W. Each of the switches 91-99 is, for example, an IGBT or the like. The two semiconductor switching elements are connected in series in the reverse direction, and a freewheeling diode is connected in antiparallel to each switching element.
[0052]
In controlling the matrix converter 90, a PWM rectifier and a PWM inverter having the same configuration as the PWM rectifier 20 and the PWM inverter 40 in FIG. 2 are virtually assumed, and PWM pulses (switching functions) for these virtual rectifier and virtual inverter are controlled by the rectifier. There is known a method of controlling the matrix converter 90 by generating the pulses by the means 50 and the inverter control means 60 and combining the pulses by the PWM pulse synthesizing means 70 (for example, “non-reactive input / output power in the matrix converter”). Interference control method ", see Rie Ito and Isao Takahashi, SPC-01-121, IEA-01-64, IEEJ Semiconductor Power Conversion Study Group).
[0053]
Here, the power conversion operation of the matrix converter 90 is expressed by Equation 14 below. In Expression 14, v _u , v _v , and v _w are output phase voltages, v _r , v _s , and v _t are input phase voltages, and S _{91 to} S ₉₉ are switching functions of the bidirectional switches _{91 to 99} .
[0054]
[Expression 14]

[0055]
Further, the switching functions S _{91 to} S ₉₉ can be expressed as Expression 15 using a switching function on the virtual rectifier side and a switching function on the virtual inverter side.
[0056]
[Expression 15]

[0057]
The PWM pulse synthesizing means 70 in FIG. 4 calculates the switching function by the equation 14 using the switching function from the rectifier control means 50 and the switching function from the inverter control means 60, and both in the matrix converter 90 according to this switching function. The direction switches 91 to 99 are on / off controlled.
The operation on the virtual rectifier side is equivalent to that of a current-type PWM rectifier because a power supply short circuit is not allowed.
[0058]
In the present embodiment, even when harmonics are included in the input voltage of the matrix converter 90, the harmonic current command of Formula 13 is superimposed on the fundamental current command in order to obtain the input current command for the virtual rectifier. Is controlled so that the instantaneous active power becomes constant, and distortion of the input current waveform and the output voltage waveform can be reduced. Here, since the operation of each means 200, 310, 320, 330, 410 in FIG. 4 is the same as that of the second embodiment, detailed description thereof is omitted.
[0059]
FIG. 5 is a block diagram showing a fourth embodiment of the present invention. In this embodiment, in order to easily perform the calculation for making the instantaneous effective power constant, the harmonic component superimposed on the input current fundamental wave command is obtained by the regulator.
[0060]
That is, in FIG. 5, current detection means 340 is connected to the output side of the AC-AC power converter 100, and the output current is detected by this detection means 340, and the output side is detected from the output voltage command and output current. Instantaneous active power is calculated by the instantaneous active power calculating means 350.
The pulsation component detecting means 360 detects the pulsation component of the calculated instantaneous active power. As described in each embodiment, the pulsation of the instantaneous active power can be suppressed by superimposing the harmonic component on the amplitude command of the fundamental wave of the input current.
Therefore, by providing an adder 370 and a regulator 380 to which the output of the pulsation detecting means 360 and zero are input with the illustrated symbol, a harmonic component such that the output of the regulator 380 makes the instantaneous effective power constant. It becomes. By adding this harmonic component to the input current fundamental wave command, the instantaneous active power on the output side of the power converter 100 can be kept constant and the output voltage waveform can be controlled to a sine wave.
Here, as the controller 380, for example, a proportional controller, a proportional-integral controller, or the like can be used.
[0061]
In addition to calculating from the output voltage command, the instantaneous active power may be obtained from each detected value of output current and output voltage by providing output voltage detection means (not shown), or on the input side of the power converter 100 Current detection means may be provided in the input voltage and the input current may be obtained from the input current.
Furthermore, this embodiment can also be applied to the circuit of FIG. 2, and a DC voltage detecting means and a DC current detecting means may be provided in the DC link section to obtain the instantaneous power of the DC link section.
This embodiment can also be applied to the circuit shown in FIG. 4. In this case, the regulator that detects the instantaneous effective power of the matrix converter 90 and adjusts the pulsation component to zero. Is superimposed on the input current fundamental wave command and added to the rectifier control means 50. The instantaneous active power in this case can also be obtained from the detected values of the output current and output voltage, the detected values of the input current and input voltage, and the like.
[0062]
The present invention can also be applied to the mutual conversion of multiphase alternating currents other than the three phases described in each embodiment.
[0063]
【The invention's effect】
As described above, according to the present invention, in a power converter composed of a rectifier and an inverter without having a large-capacity energy buffer in the DC link unit, or in an AC-AC direct conversion type power converter such as a matrix converter, Even when harmonics are included in the input voltage, a sine wave without distortion can be obtained as an output voltage waveform.
As a result, it is possible to provide an AC-AC power converter that is small and has a long life and does not impede the operation of a load such as an electric motor.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of the present invention.
FIG. 2 is a block diagram showing a second embodiment of the present invention.
FIG. 3 is an input voltage waveform and an output voltage waveform showing simulation results according to the second embodiment.
FIG. 4 is a block diagram showing a third embodiment of the present invention.
FIG. 5 is a block diagram showing a fourth embodiment of the present invention.
FIG. 6 is a block diagram showing a conventional technique.
FIG. 7 shows an input voltage waveform and an output voltage waveform in the prior art.
[Explanation of symbols]
10: Three-phase AC power supply 20: Current source PWM rectifiers 21 to 26: AC switch 40: Voltage source PWM inverters 41 to 46: Semiconductor switching element 50: Rectifier control means 60: Inverter control means 70: PWM pulse synthesizing means 100: AC AC power converter 110: matrix converters 111 to 119: bidirectional switch 200: voltage detection means 300: instantaneous active power stabilization means 310: fundamental wave detection means 320: harmonic detection means 330: harmonic current command calculation means 340 : Current detection means 350: Instantaneous active power calculation means 360: Pulsation component detection means 370, 410: Addition means 400: Input current command generation means R, S, T: AC input terminals U, V, W: AC output terminals

Claims (5)

In an AC-AC power converter that converts a polyphase AC voltage to a polyphase AC voltage without having an energy buffer in the DC link unit,
Voltage detection means for detecting the input voltage of the power converter;
Instantaneous active power stabilization means for calculating a harmonic component of the input current such that the instantaneous active power on the input side becomes constant according to the input voltage detected by the voltage detection means;
Input current command generating means for generating an input current command to be applied to the power converter by superimposing a harmonic component calculated by the stabilizing means on an input current fundamental wave command;
A control apparatus for an AC-AC power converter, comprising: A control device for an AC-AC power converter, comprising: a rectifier that converts a polyphase AC voltage into a DC voltage; and an inverter that converts a DC voltage output from the rectifier into a polyphase AC voltage, the controller of the rectifier In a control device comprising rectifier control means for controlling a rectifier given an input current command, and inverter control means for controlling the inverter,
Voltage detecting means for detecting an input voltage of the rectifier;
Fundamental wave detection means and harmonic detection means for detecting the fundamental wave component and harmonic components of the input voltage detected by the voltage detection means;
Using the fundamental wave component amplitude and the harmonic component amplitude of the input voltage detected by these fundamental wave detection means and harmonic detection means, and the input current fundamental wave command, the instantaneous effective power on the input side becomes constant. Calculating the harmonic component of the input current of the same order as the harmonic component, and outputting a harmonic current command as a harmonic current command;
Means for generating an input current command to be applied to the power converter by superimposing the harmonic current command on an input current fundamental wave command;
A control apparatus for an AC-AC power converter, comprising: A control device for an AC-AC power converter including a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage using a virtual rectifier and a virtual inverter, and an input current command of the virtual rectifier is given to the virtual rectifier Rectifier control means for outputting a control pulse, inverter control means for outputting a control pulse of the virtual inverter, pulse synthesis means for synthesizing the control pulse of the virtual rectifier and the control pulse of the virtual inverter and giving the matrix converter to the matrix converter In a control device comprising:
Voltage detection means for detecting an input voltage of the virtual rectifier;
Fundamental wave detection means and harmonic detection means for detecting the fundamental wave component and harmonic components of the input voltage detected by the voltage detection means;
Using the fundamental wave component amplitude and the harmonic component amplitude of the input voltage detected by these fundamental wave detection means and harmonic detection means, and the input current fundamental wave command, the instantaneous effective power on the input side becomes constant. Calculating the harmonic component of the input current of the same order as the harmonic component, and outputting a harmonic current command as a harmonic current command;
Means for superimposing the harmonic current command on an input current fundamental wave command to generate an input current command to be given to the rectifier control means;
A control apparatus for an AC-AC power converter, comprising: A control device for an AC-AC power converter, comprising: a rectifier that converts a polyphase AC voltage into a DC voltage; and an inverter that converts a DC voltage output from the rectifier into a polyphase AC voltage, the controller of the rectifier In a control device comprising rectifier control means for controlling a rectifier given an input current command, and inverter control means for controlling the inverter,
Means for determining the instantaneous active power of the power converter;
Means for detecting the pulsation of instantaneous active power obtained by this means;
Adjusting means for adjusting the pulsation obtained by this means to zero;
Means for generating an input current command to be applied to the rectifier by superimposing an output of the adjusting means on an input current fundamental wave command;
A control apparatus for an AC-AC power converter, comprising: A control device for an AC-AC power converter including a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage using a virtual rectifier and a virtual inverter, and an input current command of the virtual rectifier is given to the virtual rectifier Rectifier control means for outputting a control pulse, inverter control means for outputting a control pulse of the virtual inverter, pulse synthesis means for synthesizing the control pulse of the virtual rectifier and the control pulse of the virtual inverter and giving the matrix converter to the matrix converter In a control device comprising:
Means for determining the instantaneous active power of the matrix converter;
Means for detecting the pulsation of instantaneous active power obtained by this means;
Adjusting means for adjusting the pulsation obtained by this means to zero;
Means for generating an input current command to be applied to the virtual rectifier by superimposing an output of the adjusting means on an input current fundamental wave command;
A control apparatus for an AC-AC power converter, comprising:

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