JP3773794B2 - Power converter - Google Patents

Description

ただし、Ｃ：コンデンサの容量。
【００４１】
回生状態に入ってｔ秒が継続しているときの直流電圧Ｖｄｃと電力Ｐとコンデンサの充電エネルギＵとの関係は、数２式で得られる。
【００４２】
【数２】

この数２式から、直流電圧の演算値Ｖｄｃを数３式によって求める。
【００４３】
【数３】

すなわち、図３において回生時直流電圧演算器１９の内部ブロックが示すように、回生が始まった時点の直流電圧から積分の初期値Ｕｏを積分器に設定し、回生中の電力Ｐを積分して平方根を求めることにより回生中の直流電圧Ｖｄｃを演算するのである。
【００４４】
この第２の実施の形態によれば、第１の実施の形態と同様の効果を得られると共に、電動機４から回生電力がある場合にも直流電圧Ｖｄｃを正しく求めることができる。
【００４５】
（第３の実施の形態）
本発明の第３の実施の形態について、図４及び図５を用いて説明する。図４に示した本実施の形態の電力変換装置の構成要素において、図１に示した第１の実施の形態と同一の構成要素については同一番号をつけて示してある。本実施の形態において、図１の第１の実施の形態と異なる点は、電流検出器７Ａと入力電流検出器２０により変圧器２の１次電流実効値Ｉａｃ（以降、「入力電流」と称す）を検出し、制御回路６Ｂが入力電流Ｉａｃを読み込んで直流電圧Ｖｄｃの演算処理に使用する点である。
【００４６】
図５を用いて、第３の実施の形態における制御回路６Ｂの制御動作について説明する。図５に示した制御回路６Ｂの構成要素において、図１２に示した従来例の制御回路６と同一の構成要素については同一番号をつけて示してある。図１２の従来例と異なる点は、入力電圧Ｖａｃと入力電流Ｉａｃを用い直流電圧Ｖｄｃを演算するようにした点である。
【００４７】
直流電圧Ｖｄｃの演算では、直流電圧Ｖｄｃが入力交流電圧Ｖａｃと略比例関係にあるが、変圧器２の電流が増大すると変圧器２のインピーダンスドロップ分だけ直流電圧Ｖｄｃが低下する特性を模擬する。
【００４８】
第３の実施の形態においても、演算により直流電圧Ｖｄｃを求めるようにしたので、直流電圧検出回路又は直流電圧を制御回路へ取り込む伝送回路が不要な電力変換装置を構成することができる。
【００４９】
（第４の実施の形態）
本発明の第４の実施の形態について図６を用いて説明する。第４の実施の形態の電力変換装置は、基本的な回路構成を図１１の従来例と共通するが、制御回路６を図６に示す制御回路６′の構成とした点で異なる。
【００５０】
図６に示した本実施の形態の制御回路６′の構成要素において、図１２の制御回路と同一の構成要素については同一番号を用いて説明する。図１２の従来例の制御回路と異なる点は、磁束指令Φ*と速度ωｒの積から電圧指令Ｖ*を演算し、出力電圧基準Ｖｕ，Ｖｖ，Ｖｗから変調率演算器２１によりＰＷＭ制御回路８の変調率αを求め、その比Ｖ*／αから直流電圧Ｖｄｃを演算する点である。
【００５１】
この演算の具体的な方法を次に説明する。図６に示すベクトル制御回路６′は高精度に磁束及びトルク制御できることが知られている。電動機４の入力電圧Ｖは数４式と等しくなる。
【００５２】
【数４】

一方、変調率αと電力変換装置の出力電圧（＝電動機４の入力電圧）Ｖと直流電圧Ｖｄｃとの関係は、数５式となる。
【００５３】
【数５】

ここで、Ｋ：比例定数。
【００５４】
これら数４式及び数５式より、直流電圧Ｖｄｃは数６式によって求めることができる。
【００５５】
【数６】

この第４の実施の形態では、第１〜第３の実施の形態で必要であった変圧器２の１次側の電圧や電流の検出が不要であり、制御変数だけで直流電圧Ｖｄｃの検出が可能である利点がある。また、力行時と共に回生時にも直流電圧の検出ができる利点もある。
【００５６】
なお、本実施の形態では速度ωｒを直流電圧演算に用いたが、これに代えて出力周波数ω１を用いることができる。
【００５７】
（第５の実施の形態）
本発明の第５の実施の形態について、図１及び図７を用いて説明する。本実施の形態の回路構成は第１の実施の形態と同様に、図１に示したものであるが、制御回路６Ａが図７に示す構成である点が異なる。図７に示した制御回路６Ａの構成要素において、図２の制御回路と同一の構成要素については同一番号を用いて説明する。
【００５８】
本実施の形態の制御回路６Ａにおいて、図２に示した第１の実施の形態の制御回路と異なる点は、演算で検出した直流電圧Ｖｄｃと直流電圧基準Ｖｄｃ*の差分を負側リミッタ２２に入力し、差分出力が正の場合だけ電圧制御器２３により速度指令ωｒ*に対して増加方向に補正入力するようにした点である。
【００５９】
直流電圧指令Ｖｄｃ*を当該電力変換装置の単相インバータ３に対する過電圧保護レベルよりも小さく設定することで、直流電圧上昇時に過電圧保護が動作する前に、交流電動機４の速度を加速して直流電圧Ｖｄｃの上昇を抑制することができ、過電圧保護によって装置が誤停止するのを防止できる。
【００６０】
なお、図示していないが、電力変換装置の外部からの速度基準を変化率制限して電力変換装置の速度基準とする場合があるが、外部からの速度基準が低減して電動機４が回生状態とり、直流電圧Ｖｄｃが直流電圧基準Ｖｄｃ*を超過した場合に電力変換装置の速度基準の変化を０とする方法も、電力変換装置の速度基準が外部速度基準に対して相対的に増加方向に補正されることを意味するので、本発明に含まれる。
【００６１】
また、上記の第５の実施の形態では、第１の実施の形態で演算した直流電圧Ｖｄｃを用いているが、直流電圧Ｖｄｃには、すでに説明した第２〜第４の実施の形態のいずれで演算した直流電圧Ｖｄｃを用いてもよい。
【００６２】
（第６の実施の形態）
本発明の第６の実施の形態について図８及び図９を用いて説明する。図８に示した第６の実施の形態の電力変換装置の構成要素において、図１に示した第１の実施の形態のものと同一の構成要素については同一番号をつけて示してある。本実施の形態において、図１に示した第１の実施の形態の電力変換装置と異なる点は、各単相インバータ３の故障信号をＰＷＭ制御回路８Ａに入力していない点と、直流電圧Ｖｄｃが過電圧保護レベル以上になった場合に制御回路６Ｃが停止信号ＧＢをＰＷＭ制御回路８Ａへ出力して装置を停止させる点である。
【００６３】
図９を用いて、この制御回路６Ｃの制御動作について説明する。図９に示した制御回路６Ｃの構成要素において、図２の制御回路６Ａと同一の構成要素については同一番号を用いて説明する。
【００６４】
本実施の形態の制御回路６Ｃにおいて、図２の制御回路と異なる点は、演算で求めた直流電圧Ｖｄｃと直流電圧保護設定Ｖｄｃ**とを比較器２４で比較し、直流電圧Ｖｄｃが保護設定Ｖｄｃ**を超えた場合に停止信号ＧＢをＰＷＭ制御回路８Ａへ出力するようにした点である。
【００６５】
このように構成することにより、各単相インバータ３で個々に直流電圧の過電圧保護検出を行う必要が不要となる。ただし、各単相インバータ３で直流過電圧保護と本実施の形態の直流過電圧保護とを併用する場合も本発明に含まれる。
【００６６】
また、制御回路６ＣからＧＢ信号をＰＷＭ制御回路８Ａへ出力してインバータを停止させることは、第１〜第５の実施の形態、あるいは第７の実施の形態で求める直流電圧Ｖｄｃを直流過電流保護設定Ｖｄｃ**と比較して行うようにすることもできる。
【００６７】
（第７の実施の形態）
本発明の第７の実施の形態について、図１及び図１０を用いて説明する。本実施の形態の電力変換装置は、図１に示した第１の実施の形態と共通する回路構成を備えている。ただし、制御回路６Ａが図１０に示した構成である点が第１の実施の形態とは異なる。図１０に示す制御回路６Ａにおいて、図２の制御回路と同一の構成要素については同一番号を用いて示してある。
【００６８】
本実施の形態の制御回路６Ａにおいて、図２の制御回路と異なる点は、変調率演算器２１を用いて変調率αを求め、演算で求めた直流電圧Ｖｄｃと変調率αとの積から当該電力変換装置の出力電圧Ｖｍｏｔを求めるようにした点である。
【００６９】
このように構成することにより、出力電圧検出回路が不要となる。なお、本実施の形態の制御回路６Ａで求めた出力電圧は、電圧の表示、出力電圧制御、出力電圧の過電圧保護等に利用できる。しかしながら、求めた出力電圧の用途について特に限定されることはなく、本実施の形態は、直流電圧を演算し、それをもとに出力電圧を求めることを特徴とする。
【００７０】
なお、第７の実施の形態では第１の実施の形態で演算した直流電圧Ｖｄｃを用いたが、これに代えて、第２〜第４の実施の形態で演算した直流電圧を用いることができる。
【００７１】
また、図示はしないが、Ｕ，Ｖ，Ｗ相の出力電圧基準Ｖｕ，Ｖｖ，Ｖｗと演算で求めた直流電圧Ｖｄｃとの積から各相の出力電圧を演算で求める方法や、ｄ軸、ｑ軸の出力電圧基準Ｖｄ，Ｖｑと演算で求めた直流電圧Ｖｄｃとの積からｄ軸、ｑ軸電圧を求める方法も本発明に含まれる。
【００７２】
以上で第１〜第７の実施の形態について説明した。それぞれの実施の形態において各単相インバータ３内で直流過電圧を検出する方法を例に説明したが、各単相インバータ３内で直流過電圧を検出しなくても本発明に含まれる。
【００７３】
さらに、これらの実施の形態では速度検出器５を用いた速度制御について説明したが、速度検出器を用いずに、速度推定によって速度制御を実施するような場合や、速度制御を行わず、出力周波数を調節するような場合も本発明に含まれる。
【００７４】
【発明の効果】
以上のように、本発明によれば電力変換装置の直流電圧を演算により求めるようにしたので、直流電圧を直接に検出する必要がなく、直流電圧検出回路を簡略化できる。
【００７５】
また、電力回生等で直流電圧が上昇するような状態で、装置が過電圧保護により停止動作する前に直流電圧の上昇を抑制するようにすれば、電力変換装置の運転が継続できるようになる。
【００７６】
さらに、直流電圧を演算で求めると共に電力変換装置の出力電圧も検出器を用いることなく演算で求めるようにすれば、交流電圧の検出回路も簡略化できる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の電力変換装置の構成を示す回路図。
【図２】上記の第１の実施の形態における制御回路の制御ブロック図。
【図３】本発明の第２の実施の形態における制御回路の制御ブロック図。
【図４】本発明の第３の実施の形態の電力変換装置の構成を示す回路図。
【図５】上記の第３の実施の形態における制御回路の制御ブロック図。
【図６】本発明の第４の実施の形態における制御回路の制御ブロック図。
【図７】本発明の第５の実施の形態における制御回路の制御ブロック図。
【図８】本発明の第６の実施の形態の電力変換装置の構成を示す回路図。
【図９】上記の第６の実施の形態における制御回路の制御ブロック図。
【図１０】本発明の第７の実施の形態における制御回路の制御ブロック図。
【図１１】従来例の電力変換装置の構成を示す回路図。
【図１２】従来例における制御回路の制御ブロック図。
【図１３】従来例における単相インバータの構成を示す回路図。
【符号の説明】
１…３相電源
２…変圧器
３…単相インバータ
４…電動機
５…速度検出器
６，６′，６Ａ，６Ｂ，６Ｃ…制御回路
７，７Ａ…電流検出器
８，８Ａ…ＰＷＭ制御回路
９…速度制御器
１０…電流制御器
１１…３相−２相変換器
１２…２相−３相変換器
１３…整流回路
１４…平滑コンデンサ
１５…単相インバータ回路
１６…故障検出器
１７…入力電圧検出器
１８…極性判定器
１９…回生時直流電圧演算器
２０…入力電流検出器
２１…変調率演算器
２２…負側リミッタ
２３…電圧制御器
２４…比較器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power conversion device that performs power conversion of an AC power source and outputs desired multiphase AC power.
[0002]
[Prior art]
Conventionally, as a power conversion device that converts an AC power source into desired three-phase power and outputs the same, the configuration shown in FIG. 11 is intended to increase the capacity and voltage of the power conversion device, and to improve the output waveform. Things are known.
[0003]
This conventional power converter supplies three-phase AC power to a single-phase inverter 3 from a three-phase power source 1 via a transformer 2 having a plurality of windings on the secondary side. The output of the single-phase inverter 3 is connected in series, and one of them is connected as a neutral point, and the other is connected to a three-phase induction motor (M) 4 so that three-phase AC power is supplied to the induction motor 4. Supply. The rotation speed of the induction motor 4 is detected by the speed detector 5 and input to the control circuit 6. The current output from the power converter is detected by the current detector 7 and input to the control circuit 6.
[0004]
In the control circuit 6, output voltage references Vu, Vv, Vw are determined so that the speed of the electric motor 4 becomes a predetermined speed, and is output to the PWM control circuit 8. The PWM control circuit 8 controls the gate signal of each single-phase inverter 3 so as to generate an output voltage corresponding to the output voltage reference Vu, Vv, Vw. If any single-phase inverter 3 fails, a failure signal from the single-phase inverter 3 is input to the PWM control circuit 8 to stop the operation of the power converter.
[0005]
FIG. 12 is a detailed diagram of the control circuit 6 of FIG. This control circuit 6 is a widely known circuit (for example, published by Denki Shoin, “New Life Electronics”, section 6.2.4), and the current of the induction motor 4 is decomposed into a torque current and an excitation current, and independently. Control.
[0006]
In this control circuit 6, the torque command T * is adjusted by using the speed controller 9 so that the deviation between the speed command ωr * and the speed ωr becomes zero. On the other hand, the excitation command Φ * is usually kept constant. In the figure, the set value of the excitation command Φ * is indicated as Φset. These values are converted into orthogonal two-phase d-axis and q-axis current commands Id * and Iq * by the calculation shown in the block diagram of FIG. 12, and the deviation from each current feedback signal Id and Iq is zero. The d-axis and q-axis voltage commands Vd and Vq are adjusted using the current controller 10.
[0007]
Further, the slip frequency ωs is obtained from the torque command T * and the excitation command Φ *, and the speed signal ωr fed back from the speed detector 5 is added to the slip frequency ωs, thereby determining the frequency ω1 output from the power converter. Using the output phase θ1 obtained by integrating the output frequency ω1, the three-phase to two-phase converter 11 obtains the d-axis and q-axis currents Id and Iq from the three-phase current detection values Iu, Iv and Iw. At the same time, output voltage references Vu, Vv, and Vw are obtained by the two-phase to three-phase converter 12 from the d-axis and q-axis voltage commands.
[0008]
FIG. 13 is a detailed view of the single-phase inverter 3 of FIG. The power from the secondary winding of the transformer 2 is converted into DC power by the diode rectifier circuit 13 and the DC smoothing capacitor 14, and further converted into power having an arbitrary frequency and voltage by the single-phase inverter circuit 15. The failure detector 16 detects an abnormality in the single-phase inverter 3 and outputs a failure signal to the PWM control circuit 8 in FIG.
[0009]
As an example of the abnormality of the single-phase inverter 3, an increase in the DC voltage Vdc can be considered. Usually, when the DC voltage Vdc rises above a predetermined value, it is generally performed to detect a failure and stop the power converter so that components in the single-phase inverter 3 are not damaged due to overvoltage.
[0010]
[Problems to be solved by the invention]
However, in the power converter configured as described above, when the output frequency of the power converter is lower than the rotational speed of the AC motor 4, the mechanical energy of the AC motor is regenerated in the power converter, and the DC The voltage is charged by regenerative energy, the DC voltage rises, an overvoltage failure is detected, and there is a problem that the device is stopped although it is not a failure.
[0011]
In order to solve this problem, an increase in the DC voltage Vdc may be detected before an overvoltage failure is detected, and control may be performed so as to increase the output frequency so that regenerative operation does not occur. When this control is performed, it is necessary to capture the DC voltage value Vdc of each single-phase inverter 3 into the control circuit 6.
[0012]
However, as shown in FIG. 11, the power converter having a multiple connection inverter configuration using a plurality of single-phase inverters 3 has a problem that the DC voltage detection circuit becomes very complicated and expensive because there are a plurality of DC circuits. In addition, even in the case of a single inverter regardless of multiple connection inverters, it is common to perform voltage detection by insulating the control circuit and the DC circuit, but in recent years, power converters have become high voltage and the DC circuit And the control circuit are insulated from each other, the voltage detection circuit becomes complicated, and there is a problem that reliability is lowered and detection accuracy is lowered.
[0013]
In view of the above-described conventional problems, the present invention obtains a DC voltage by using the input or output voltage, current, and control amount for controlling the power converter of the power converter, thereby providing a complicated circuit configuration. It aims at providing the power converter device which can obtain | require DC voltage with the high precision at least.
[0014]
Another object of the present invention is to provide a power conversion device that does not stop by erroneously detecting an overvoltage failure by using the obtained DC voltage.
[0015]
[Means for Solving the Problems]
  According to the first aspect of the present invention, there is provided a transformer comprising a multiphase primary winding and a multiphase secondary winding, and a rectifier that is connected to the secondary winding of the transformer and converts a multiphase AC voltage into a DC voltage. A DC circuit that is connected to the circuit and the rectifier circuit, and converts the DC voltage into an AC voltage corresponding to a voltage reference signal.Single phase inverterAnd saidSingle phase inverterOutput in series or parallelMultipleIn a power converter connected to generate multi-phase AC power and supply the multi-phase AC power to the multi-phase AC motor, input voltage detecting means for detecting a voltage on the primary side of the transformer, and the AC motor Motor input power calculation means for calculating the power flowing into the inverter, and DC voltage calculation means for calculating the DC voltage from the voltage on the primary side of the transformer and the power flowing into the AC motor. is there.
[0016]
In the power conversion device according to the first aspect of the invention, the voltage on the primary side of the transformer is detected, the power flowing into the AC motor is calculated, and the voltage on the primary side of these transformers and the AC motor are flown into the AC motor. Calculate the DC voltage of the power converter from the power.
[0017]
According to a second aspect of the present invention, there is provided the power converter according to the first aspect, wherein the direct-current voltage calculation means is configured such that when the power flowing into the alternating-current motor is equal to or greater than a predetermined value, the voltage on the primary side of the transformer The DC voltage is calculated from the power flowing into the AC motor, and when the power flowing into the AC motor is less than a predetermined value, the power flowing into the AC motor is integrated.
[0018]
In the power conversion device according to the second aspect of the invention, when the power flowing into the AC motor is greater than or equal to a predetermined value, the DC voltage is calculated from the voltage on the primary side of the transformer and the power flowing into the AC motor. When the power flowing into the electric motor is less than or equal to a predetermined value, the direct current is obtained by integrating the power flowing into the AC motor.
[0019]
  According to a third aspect of the present invention, a transformer comprising a multi-phase primary winding and a multi-phase secondary winding and a secondary winding of the transformer are respectively connected to convert the multi-phase AC voltage into a DC voltage. A rectifier circuit and the rectifier circuit are respectively connected to convert the DC voltage into an AC voltage corresponding to a voltage reference signal.Single phase inverterAnd saidSingle phase inverterOutput in series or parallelMultipleAn input voltage detecting means for detecting a voltage on the primary side of the transformer in a power converter for connecting and generating multiphase AC power and supplying the multiphase AC power to a multiphase AC motor, and the transformer Input current detecting means for detecting the primary side current of the transformer, and DC voltage calculating means for calculating the DC voltage from the voltage on the primary side of the transformer and the current on the primary side of the transformer. It is made up of.
[0020]
In the power conversion device of the invention of claim 3, the voltage on the primary side of the transformer is detected, the current on the primary side of the transformer is detected, and the voltage and current on the primary side of these transformers are detected. Calculate the DC voltage of the power converter.
[0021]
  According to a fourth aspect of the present invention, there is provided a transformer comprising a multi-phase primary winding and a multi-phase secondary winding, and a rectifier connected to the secondary winding of the transformer for converting a multi-phase AC voltage into a DC voltage. A DC circuit that is connected to the circuit and the rectifier circuit, and converts the DC voltage into an AC voltage corresponding to a voltage reference signal.Single phase inverterAnd saidSingle phase inverterOutput in series or parallelMultipleIn a power converter that connects and generates multi-phase AC power and supplies the multi-phase AC power to the multi-phase AC motor, a voltage reference signal to the power converter is determined based on the torque reference and excitation reference of the AC motor. Determining means; frequency detecting means for detecting a frequency output from the power converter; or speed detecting means for detecting a speed of the AC motor; a frequency output from the power converter or the speed of the AC motor and the excitation AC voltage output calculation means for calculating the AC voltage output from the power converter from the reference, and the DC voltage from the voltage reference signal for the power converter and the calculated value of the AC voltage output from the power converter. And DC voltage calculating means.
[0022]
In the power converter of the invention of claim 4, a voltage reference signal to the power converter is determined based on the torque reference and excitation reference of the AC motor, and the frequency output from the power converter or the speed of the AC motor is detected. The AC voltage output from the power converter is calculated from the frequency output from the power converter or the speed of the AC motor and the excitation reference. And the direct-current voltage of the said power converter is calculated | required and calculated | required from the above-mentioned voltage reference signal with respect to the said power converter, and the calculated value of the said alternating voltage output from the said power converter.
[0023]
According to a fifth aspect of the present invention, in the power conversion device according to any one of the first to fourth aspects, a direct current that corrects the direct current voltage in a direction in which a frequency output from the power conversion device increases when the direct current voltage becomes a predetermined value or more. A voltage reduction means or a frequency reduction suppression means for suppressing the frequency reduction is provided.
[0024]
In the power converter of the invention of claim 5, when the DC voltage of the power converter determined by calculation in the inventions of claims 1 to 4 exceeds a predetermined value, the frequency output by the power converter increases. The DC voltage is corrected in the direction, or the decrease in the frequency output from the power converter is suppressed.
[0025]
According to a sixth aspect of the present invention, there is provided the power conversion device according to any one of the first to fourth aspects, further comprising an output stop means for stopping the output of the power conversion device when the DC voltage becomes a predetermined value or more.
[0026]
In the power converter of the invention of claim 6, the output of the power converter is stopped when the DC voltage of the power converter obtained by calculation in the invention of claims 1 to 4 exceeds a predetermined value.
[0027]
A seventh aspect of the present invention is the power conversion device according to any one of the first to fourth aspects, further comprising output voltage calculation means for calculating an AC voltage output from the power conversion device from the calculated value of the DC voltage and a voltage reference signal. It is.
[0028]
In the power converter of the invention of claim 7, the AC voltage output from the power converter is calculated from the DC voltage of the power converter determined by the calculation in the inventions of claims 1 to 4 and the voltage reference signal.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0030]
(First embodiment)
A first embodiment of the present invention will be described with reference to FIG. In the constituent elements of the power conversion device according to the first embodiment shown in FIG. 1, the same constituent elements as those in the conventional example shown in FIG. 11 is different from the conventional example of FIG. 11 in that the effective value Vac (hereinafter referred to as “input voltage”) of the primary voltage of the transformer 2 is detected by the input voltage detector 17 and read by the control circuit 6A. This is a point used for the calculation processing of the voltage Vdc.
[0031]
FIG. 2 shows a control block diagram of the control circuit 6A. In the constituent elements of the control circuit 6A shown in FIG. 2, the same constituent elements as those of the control circuit 6 of the conventional example shown in FIG. The difference from the conventional example of FIG. 12 is that the output P of the AC motor 4 is obtained from the torque command T * and the speed ωr, and the DC voltage Vdc is calculated using this and the input voltage Vac.
[0032]
In the calculation of the DC voltage Vdc, the AC voltage Vac and the DC voltage Vdc are approximately proportional to each other. However, when the load of the transformer 2 is increased, the DC voltage Vdc is reduced by the impedance drop of the transformer 2. ing.
[0033]
According to the power conversion device of the first embodiment, since the DC voltage Vdc is obtained by calculation, it is possible to configure a power conversion device that does not require a DC voltage detection circuit or a transmission circuit that takes the DC voltage into the control circuit. .
[0034]
In the first embodiment, the electric power flowing into the electric motor 4 is obtained from the product of the torque command T * and the speed ωr as being approximately equivalent to the electric motor output P, but the voltage and current output by the electric power converter are detected. The configuration may be obtained from the above, or the configuration may be obtained from the voltage reference signal commanded to the power converter and the detected current value.
[0035]
Furthermore, although 1st Embodiment made it the simple structure using the characteristic that DC voltage Vdc fell only the part of the impedance drop of the transformer 2 when the load of the transformer 2 increased, the electric power which flows into the motor 4, and the said The current flowing through the transformer 2 may be calculated from the conversion efficiency of the power conversion device, the input voltage, and the like, and the DC voltage Vdc may be obtained by calculating the impedance drop strictly from the current and the impedance of the transformer 2.
[0036]
(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. The overall configuration of the power conversion device according to the second embodiment is as shown in FIG. 1 as in the first embodiment. The detailed configuration of the control circuit 6A is shown in FIG. 3, which is different from that of the first embodiment shown in FIG. In FIG. 3, the same components as those of the control circuit of the first embodiment shown in FIG. 2 will be described using the same reference numerals.
[0037]
In the control circuit 6A according to the present embodiment, the difference from the first embodiment shown in FIG. 2 is that the polarity of the motor output P is determined by the polarity determiner 18, and the first case when the polarity is positive. The DC voltage Vdc is calculated and output by the same method as in the above embodiment, and when it is negative, switching is performed so that the DC voltage Vdc calculated by the regenerative DC voltage calculator 19 is output.
[0038]
The DC voltage calculator 19 at the time of regeneration operates as follows. The single-phase inverter 3 in the power conversion device of FIG. 1 has a configuration common to the single-phase inverter 3 shown in FIG. 13 as a conventional example, and includes a rectifier circuit 13 made of a diode. Therefore, when the power converter is in a regenerative state, all the diodes are turned off and the input of the rectifier circuit 13 and the DC circuit are disconnected. That is, all the electric power from the motor 4 is charged in the DC smoothing capacitor 14. The DC voltage calculator 19 at the time of regeneration calculates the DC voltage Vdc by simulating that the smoothing capacitor 14 is charged with the regenerative power from the motor 4 at the time of regeneration and the DC voltage rises. A specific method of calculation is as follows.
[0039]
The charging energy Uo of the smoothing capacitor 14 before entering the regenerative state is obtained by the equation 1 using the DC voltage Vdc at that time.
[0040]
[Expression 1]

C: Capacitor capacity.
[0041]
The relationship among the DC voltage Vdc, the power P, and the charging energy U of the capacitor when t seconds have continued since entering the regenerative state can be obtained from Equation 2.
[0042]
[Expression 2]

From this equation (2), the calculated value Vdc of the DC voltage is obtained by equation (3).
[0043]
[Equation 3]

That is, as shown in the internal block of the DC voltage calculator 19 at the time of regeneration in FIG. 3, the integration initial value Uo is set in the integrator from the DC voltage at the time when regeneration starts, and the power P during regeneration is integrated. The DC voltage Vdc during regeneration is calculated by obtaining the square root.
[0044]
According to the second embodiment, the same effect as that of the first embodiment can be obtained, and the DC voltage Vdc can be correctly obtained even when there is regenerative power from the motor 4.
[0045]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS. In the constituent elements of the power conversion apparatus of the present embodiment shown in FIG. 4, the same constituent elements as those of the first embodiment shown in FIG. This embodiment differs from the first embodiment of FIG. 1 in that the primary current effective value Iac (hereinafter referred to as “input current”) of the transformer 2 by the current detector 7A and the input current detector 20 is different. ) And the control circuit 6B reads the input current Iac and uses it for the calculation of the DC voltage Vdc.
[0046]
The control operation of the control circuit 6B in the third embodiment will be described with reference to FIG. In the constituent elements of the control circuit 6B shown in FIG. 5, the same constituent elements as those of the control circuit 6 of the conventional example shown in FIG. The difference from the conventional example of FIG. 12 is that the DC voltage Vdc is calculated using the input voltage Vac and the input current Iac.
[0047]
In the calculation of the DC voltage Vdc, the DC voltage Vdc is substantially proportional to the input AC voltage Vac. However, when the current of the transformer 2 increases, the DC voltage Vdc decreases by the impedance drop of the transformer 2.
[0048]
Also in the third embodiment, since the DC voltage Vdc is obtained by calculation, it is possible to configure a power converter that does not require a DC voltage detection circuit or a transmission circuit for taking DC voltage into the control circuit.
[0049]
(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIG. The power converter of the fourth embodiment has a basic circuit configuration in common with the conventional example of FIG. 11, but differs in that the control circuit 6 is configured as a control circuit 6 ′ shown in FIG.
[0050]
In the constituent elements of the control circuit 6 ′ of the present embodiment shown in FIG. 6, the same constituent elements as those of the control circuit of FIG. The difference from the control circuit of the conventional example of FIG. 12 is that the voltage command V * is calculated from the product of the magnetic flux command Φ * and the speed ωr, and the PWM control circuit 8 is operated from the output voltage reference Vu, Vv, Vw by the modulation factor calculator 21. Is obtained by calculating the DC voltage Vdc from the ratio V * / α.
[0051]
A specific method of this calculation will be described next. It is known that the vector control circuit 6 'shown in FIG. 6 can control magnetic flux and torque with high accuracy. The input voltage V of the electric motor 4 is equal to Equation 4.
[0052]
[Expression 4]

On the other hand, the relationship among the modulation factor α, the output voltage of the power conversion device (= input voltage of the electric motor 4) V, and the DC voltage Vdc is expressed by Equation 5.
[0053]
[Equation 5]

Here, K: proportional constant.
[0054]
From these equations 4 and 5, the DC voltage Vdc can be obtained from equation 6.
[0055]
[Formula 6]

In the fourth embodiment, it is not necessary to detect the voltage or current on the primary side of the transformer 2 which is necessary in the first to third embodiments, and the detection of the DC voltage Vdc is performed only by the control variable. There is an advantage that is possible. In addition, there is an advantage that the DC voltage can be detected during power regeneration as well as during regeneration.
[0056]
In this embodiment, the speed ωr is used for DC voltage calculation, but the output frequency ω1 can be used instead.
[0057]
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to FIGS. The circuit configuration of the present embodiment is the same as that of the first embodiment shown in FIG. 1, except that the control circuit 6A has the configuration shown in FIG. In the components of the control circuit 6A shown in FIG. 7, the same components as those in the control circuit of FIG.
[0058]
The control circuit 6A of the present embodiment differs from the control circuit of the first embodiment shown in FIG. 2 in that the difference between the DC voltage Vdc detected by the calculation and the DC voltage reference Vdc * is applied to the negative limiter 22. Only when the difference output is positive, the voltage controller 23 makes a correction input in the increasing direction with respect to the speed command ωr *.
[0059]
By setting the DC voltage command Vdc * to be smaller than the overvoltage protection level for the single-phase inverter 3 of the power converter, the speed of the AC motor 4 is accelerated before the overvoltage protection is activated when the DC voltage rises. An increase in Vdc can be suppressed, and the apparatus can be prevented from being erroneously stopped by overvoltage protection.
[0060]
Although not shown, the speed reference from the outside of the power converter may be limited by the rate of change to be the speed reference of the power converter, but the speed reference from the outside is reduced and the electric motor 4 is in a regenerative state. However, when the DC voltage Vdc exceeds the DC voltage reference Vdc *, the method of setting the change of the speed reference of the power converter to 0 is also a method in which the speed reference of the power converter is relatively increased with respect to the external speed reference. Since it means that it is corrected, it is included in the present invention.
[0061]
In the fifth embodiment, the DC voltage Vdc calculated in the first embodiment is used. The DC voltage Vdc can be any of the second to fourth embodiments already described. The DC voltage Vdc calculated in (1) may be used.
[0062]
(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIGS. In the constituent elements of the power conversion device of the sixth embodiment shown in FIG. 8, the same constituent elements as those of the first embodiment shown in FIG. This embodiment differs from the power converter of the first embodiment shown in FIG. 1 in that a failure signal of each single-phase inverter 3 is not input to the PWM control circuit 8A, and the DC voltage Vdc. Is that the control circuit 6C outputs a stop signal GB to the PWM control circuit 8A to stop the apparatus when the voltage exceeds the overvoltage protection level.
[0063]
The control operation of the control circuit 6C will be described with reference to FIG. Among the components of the control circuit 6C shown in FIG. 9, the same components as those of the control circuit 6A of FIG.
[0064]
The control circuit 6C of the present embodiment is different from the control circuit of FIG. 2 in that the DC voltage Vdc obtained by calculation and the DC voltage protection setting Vdc ** are compared by the comparator 24, and the DC voltage Vdc is set as the protection setting. This is the point that the stop signal GB is output to the PWM control circuit 8A when Vdc ** is exceeded.
[0065]
With this configuration, it is not necessary to perform overvoltage protection detection of the DC voltage individually in each single-phase inverter 3. However, the case where the DC overvoltage protection and the DC overvoltage protection of the present embodiment are used together in each single-phase inverter 3 is also included in the present invention.
[0066]
Further, outputting the GB signal from the control circuit 6C to the PWM control circuit 8A to stop the inverter means that the DC voltage Vdc obtained in the first to fifth embodiments or the seventh embodiment is converted to the DC overcurrent. It can also be performed in comparison with the protection setting Vdc **.
[0067]
(Seventh embodiment)
A seventh embodiment of the present invention will be described with reference to FIGS. The power conversion device of the present embodiment has a circuit configuration common to that of the first embodiment shown in FIG. However, it differs from the first embodiment in that the control circuit 6A has the configuration shown in FIG. In the control circuit 6A shown in FIG. 10, the same components as those of the control circuit of FIG.
[0068]
The control circuit 6A of the present embodiment is different from the control circuit of FIG. 2 in that the modulation factor calculator 21 is used to obtain the modulation factor α, and the product of the DC voltage Vdc obtained by the calculation and the modulation factor α The output voltage Vmot of the power converter is obtained.
[0069]
With this configuration, the output voltage detection circuit becomes unnecessary. The output voltage obtained by the control circuit 6A of the present embodiment can be used for voltage display, output voltage control, output voltage overvoltage protection, and the like. However, the use of the obtained output voltage is not particularly limited, and the present embodiment is characterized in that a DC voltage is calculated and the output voltage is obtained based on the calculated DC voltage.
[0070]
In the seventh embodiment, the DC voltage Vdc calculated in the first embodiment is used. Instead, the DC voltage calculated in the second to fourth embodiments can be used. .
[0071]
Although not shown, a method for calculating the output voltage of each phase from the product of the U, V, W phase output voltage references Vu, Vv, Vw and the DC voltage Vdc obtained by the calculation, d-axis, q A method of obtaining the d-axis and q-axis voltages from the product of the shaft output voltage references Vd and Vq and the DC voltage Vdc obtained by calculation is also included in the present invention.
[0072]
  The first to seventh embodiments have been described above. In each of the embodiments, the method for detecting the DC overvoltage in each single-phase inverter 3 has been described as an example. However, the present invention is included even if the DC overvoltage is not detected in each single-phase inverter 3..
[0073]
Further, in these embodiments, the speed control using the speed detector 5 has been described. However, when speed control is performed by speed estimation without using the speed detector, speed control is not performed, and output is performed. The case where the frequency is adjusted is also included in the present invention.
[0074]
【The invention's effect】
As described above, according to the present invention, since the DC voltage of the power converter is obtained by calculation, it is not necessary to directly detect the DC voltage, and the DC voltage detection circuit can be simplified.
[0075]
In addition, in a state where the DC voltage increases due to power regeneration or the like, if the increase of the DC voltage is suppressed before the device is stopped by overvoltage protection, the operation of the power conversion device can be continued.
[0076]
Furthermore, if the DC voltage is obtained by calculation and the output voltage of the power converter is obtained by calculation without using a detector, the AC voltage detection circuit can be simplified.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a power conversion device according to a first embodiment of the present invention.
FIG. 2 is a control block diagram of a control circuit in the first embodiment.
FIG. 3 is a control block diagram of a control circuit according to a second embodiment of the present invention.
FIG. 4 is a circuit diagram showing a configuration of a power conversion device according to a third embodiment of the present invention.
FIG. 5 is a control block diagram of a control circuit in the third embodiment.
FIG. 6 is a control block diagram of a control circuit according to a fourth embodiment of the present invention.
FIG. 7 is a control block diagram of a control circuit according to a fifth embodiment of the present invention.
FIG. 8 is a circuit diagram showing a configuration of a power conversion device according to a sixth embodiment of the present invention.
FIG. 9 is a control block diagram of a control circuit in the sixth embodiment.
FIG. 10 is a control block diagram of a control circuit according to a seventh embodiment of the present invention.
FIG. 11 is a circuit diagram showing a configuration of a conventional power conversion device.
FIG. 12 is a control block diagram of a control circuit in a conventional example.
FIG. 13 is a circuit diagram showing a configuration of a single-phase inverter in a conventional example.
[Explanation of symbols]
1 ... Three-phase power supply
2 ... Transformer
3 ... Single-phase inverter
4 ... Electric motor
5. Speed detector
6, 6 ', 6A, 6B, 6C ... control circuit
7, 7A ... Current detector
8,8A ... PWM control circuit
9 ... Speed controller
10 ... Current controller
11 ... 3-phase-2 phase converter
12 ... Two-phase to three-phase converter
13 ... Rectifier circuit
14: Smoothing capacitor
15 ... Single-phase inverter circuit
16 ... Failure detector
17 ... Input voltage detector
18 ... Polarity detector
19 ... DC voltage calculator for regeneration
20 ... Input current detector
21 ... Modulation rate calculator
22 ... Negative limiter
23 ... Voltage controller
24 ... Comparator

Claims (7)

A transformer composed of a polyphase primary winding and a polyphase secondary winding, a rectifier circuit connected to the secondary winding of the transformer and converting a polyphase AC voltage to a DC voltage; and the rectifier circuit are connected, and the single-phase inverter that converts the AC voltage corresponding to the DC voltage to a voltage reference signal, and multiple access to generate a multi-phase AC power output of the single-phase inverters in series or in parallel, the multiphase In a power conversion device that supplies AC power to a multiphase AC motor,
Input voltage detecting means for detecting the voltage on the primary side of the transformer;
Motor input power calculating means for calculating power flowing into the AC motor;
A power converter comprising a DC voltage calculation means for calculating the DC voltage from the voltage on the primary side of the transformer and the power flowing into the AC motor.   The DC voltage calculating means calculates the DC voltage from the voltage on the primary side of the transformer and the power flowing into the AC motor when the power flowing into the AC motor is greater than or equal to a predetermined value, The power conversion device according to claim 1, wherein when the power flowing into the AC motor is equal to or less than a predetermined value, the power flowing into the AC motor is integrated. A transformer comprising a polyphase primary winding and a polyphase secondary winding; a rectifier circuit connected to the secondary winding of the transformer and converting a polyphase AC voltage to a DC voltage; and the rectifier circuit the respectively connected, and the single-phase inverter that converts the DC voltage into an AC voltage corresponding to the voltage reference signal, and multiple access to generate a multi-phase AC power output of the single-phase inverters in series or in parallel, the multi In a power conversion device that supplies phase AC power to a multiphase AC motor,
Input voltage detecting means for detecting the voltage on the primary side of the transformer;
Input current detecting means for detecting a current on the primary side of the transformer;
A power converter comprising: a DC voltage calculation means for calculating the DC voltage from a voltage on the primary side of the transformer and a current on the primary side of the transformer. A transformer composed of a polyphase primary winding and a polyphase secondary winding, a rectifier circuit connected to the secondary winding of the transformer and converting a polyphase AC voltage to a DC voltage; and the rectifier circuit are connected, and the single-phase inverter that converts the AC voltage corresponding to the DC voltage to a voltage reference signal, and multiple access to generate a multi-phase AC power output of the single-phase inverters in series or in parallel, the multiphase In a power conversion device that supplies AC power to a multiphase AC motor,
Means for determining a voltage reference signal to the power converter according to a torque reference and an excitation reference of the AC motor;
A frequency detection means for detecting the frequency output by the power converter or a speed detection means for detecting the speed of the AC motor;
AC voltage output calculation means for calculating the AC voltage output from the power converter from the frequency output from the power converter or the speed of the AC motor and the excitation reference;
A power conversion device comprising: a voltage reference signal for the power conversion device; and a DC voltage calculation means for calculating the DC voltage from the calculation value of the AC voltage output from the power conversion device.   DC voltage correction means for correcting the DC voltage in a direction in which the frequency output from the power converter increases when the DC voltage becomes a predetermined value or more, or frequency reduction suppression means for suppressing the decrease in the frequency. The power conversion device according to claim 1, wherein the power conversion device is a power conversion device.   The power converter according to any one of claims 1 to 4, further comprising an output stop unit that stops the output of the power converter when the DC voltage becomes a predetermined value or more.   The power converter according to any one of claims 1 to 4, further comprising an output voltage calculator that calculates an AC voltage output from the power converter from the calculated value of the DC voltage and a voltage reference signal. .

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