JP6370702B2 - Power converter - Google Patents
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本発明は、単位変換器を多段接続したＭＭＣ（Ｍｏｄｕｌａｒ Ｍｕｌｔｉｌｅｖｅｌ Ｃｏｎｖｅｒｔｅｒ）回路に好適な電力変換装置に関する。 The present invention relates to a power converter suitable for an MMC (Modular Multilevel Converter) circuit in which unit converters are connected in multiple stages.
半導体技術の発展と共に、電力変換器（インバータ）に用いるスイッチング素子も進歩してきた。その成果の１つとして、変換器の多レベル化がある。 With the development of semiconductor technology, switching elements used for power converters (inverters) have also advanced. One of the achievements is multi-level conversion.
従来、電力変換器が高圧系統に連系する際には、２，３電圧レベルの変換器出力をトランスで昇圧するのが一般的であったが、その場合、出力電圧に含まれる高調波成分を低減するために、三相交流出力にリアクトルやコンデンサで構成される高調波フィルタを挿入する必要があった。出力電圧のレベル数が少ないと、含まれる高調波成分も大きい。そのため、電力系統に流れ出す高調波成分が他の機器に悪影響を及ぼさないレベルまで低減させるためには、前記高調波フィルタを大きくする必要があり、結果としてコストの増大と重量の増加を招いていた。 Conventionally, when a power converter is connected to a high-voltage system, it has been common to boost the converter output of a few voltage levels with a transformer, but in that case, harmonic components included in the output voltage In order to reduce this, it is necessary to insert a harmonic filter composed of a reactor and a capacitor into the three-phase AC output. When the number of levels of the output voltage is small, the included harmonic components are large. Therefore, in order to reduce the harmonic component flowing out to the power system to a level that does not adversely affect other devices, it is necessary to enlarge the harmonic filter, resulting in an increase in cost and weight. .
これらを解決するべく、細かい電圧を出力する単位変換器を複数台直列接続することにより、多レベルの階段状の電圧波形を出力できる電力変換器（ＭＭＣ：Ｍｏｄｕｌａｒ Ｍｕｌｔｉｌｅｖｅｌ Ｃｏｎｖｅｒｔｅｒ）の開発が進められている。このＭＭＣ回路の場合、多レベル化により出力電圧の波形を正弦波に近付けることができるため、重量、体積及びコストの面で不利な前記高調波フィルタを小型化し、あるいは不要にできるメリットがある。 In order to solve these problems, development of a power converter (MMC: Modular Multilevel Converter) that can output a multi-level stepped voltage waveform by connecting a plurality of unit converters that output fine voltages in series has been promoted. Yes. In the case of this MMC circuit, since the waveform of the output voltage can be brought close to a sine wave by increasing the number of levels, there is an advantage that the harmonic filter which is disadvantageous in terms of weight, volume and cost can be reduced in size or made unnecessary.
このＭＭＣ回路は、単位変換器がそれぞれ備える直流電圧源が独立しており、それら全ての電圧を一定に保つ必要がある。直列段数が増え、単位変換器の数が増えるほど、蓄電池や絶縁ＤＣ／ＤＣ変換器といった手段で単位変換器の直流電圧源を用意することが非現実的となる。そのような場合はコンデンサを直流電圧源として、制御によって電圧を一定に保つことが一般的である。Ｓｔａｔｉｃ Ｓｙｎｃｈｒｏｎｏｕｓ Ｃｏｍｐｅｎｓａｔｏｒ（ＳＴＡＴＣＯＭ）やＨｉｇｈ Ｖｏｌｔａｇｅ Ｄｉｒｅｃｔ Ｃｕｒｒｅｎｔ（ＨＶＤＣ）変換器等の系統連系機器に前記ＭＭＣ回路を適用する場合、系統から電力を得て、単位変換器のコンデンサ電圧を制御することになる。 In this MMC circuit, the DC voltage sources provided in the unit converters are independent, and it is necessary to keep all these voltages constant. As the number of series stages increases and the number of unit converters increases, it becomes impractical to prepare a DC voltage source for the unit converters by means such as a storage battery or an insulated DC / DC converter. In such a case, it is common to use a capacitor as a DC voltage source and keep the voltage constant by control. When the MMC circuit is applied to a grid-connected device such as a Static Synchronous Compensator (STATCOM) or a High Voltage Direct Current (HVDC) converter, power is obtained from the grid and the capacitor voltage of the unit converter is controlled. .
コンデンサ電圧の制御は、変換器が備える全てのコンデンサ電圧平均値を定格値に一致させる全体電圧制御、各相の備えるコンデンサ電圧平均値を全相平均値に一致させる相間バランス制御、各相の備える個々のコンデンサ電圧を当該相の平均値に一致させる段間バランス制御、などの制御法により実現される。（非特許文献１） Capacitor voltage control includes overall voltage control that matches all capacitor voltage average values of the converter with the rated value, phase-to-phase balance control that matches the capacitor voltage average value of each phase with the average value of all phases, and provision of each phase This is realized by a control method such as interstage balance control in which individual capacitor voltages are matched with the average value of the phase. (Non-Patent Document 1)
単位変換器のコンデンサ電圧は充放電によって上下するため、単位変換器に電流が流れなければ制御できない。前記ＳＴＡＴＣＯＭにおける無効電力補償運転中、及び前記ＨＶＤＣ変換器における電力輸送中は、電流が流れるために全てのコンデンサ電圧は制御される。 Since the capacitor voltage of the unit converter goes up and down by charging and discharging, it cannot be controlled unless a current flows through the unit converter. During the reactive power compensation operation in the STATCOM and during the power transfer in the HVDC converter, all capacitor voltages are controlled because current flows.
しかしながら、ＳＴＡＴＣＯＭで無効電力出力を停止する場合や、ＨＶＤＣ変換器で輸送電力を停止する場合は、基本的に単位変換器に電流が流れないので、当該期間は、コンデンサ電圧の段間バランス制御が有効に作用しなくなるという不具合を生じる。 However, when reactive power output is stopped by STATCOM, or when transport power is stopped by an HVDC converter, basically no current flows through the unit converter. This causes a problem that it does not work effectively.
例えばデルタ結線のＳＴＡＴＣＯＭが無効電力補償運転を停止して、無効電力の出力指令または無効電流指令が零である時も、各種制御は動作するため、全体電圧制御による有効電流と、相間バランス制御による零相電流は流れる。 For example, when STATCOM of delta connection stops the reactive power compensation operation and the reactive power output command or reactive current command is zero, various controls operate, so the active current based on the overall voltage control and the interphase balance control Zero-phase current flows.
しかし全体電圧制御と相間バランスの偏差は常に微小であるため、これらの制御による電流も微小であり、流れたとしても段間バランス制御への寄与は小さい。また、単位変換器に流れる電流は、必ず系統または他相にも流れるため、段間のバランスのみに影響する電流のモードは存在しない。 However, since the deviation between the overall voltage control and the interphase balance is always very small, the current by these controls is also very small, and even if it flows, the contribution to the interstage balance control is small. In addition, since the current flowing through the unit converter always flows through the system or other phases, there is no current mode that affects only the balance between stages.
図７は、無効電力出力指令ｑ*がタイミングｔ０時点で停止した後の、各コンデンサ電圧の変化を示している。図７（Ａ）がｒ，ｓ，ｔ各相のコンデンサ電圧平均値ｖcr，ｖcs，ｖct、図７（Ｂ）がｒ相の単位変換器が備えるコンデンサの電圧ｖcr1，ｖcr2，ｖcr3、図７（Ｃ）が無効電力出力指令ｑ*を示す。 FIG. 7 shows changes in the capacitor voltages after the reactive power output command q * is stopped at the timing t0. 7A shows capacitor voltage average values vcr, vcs, vct for the r, s, and t phases, and FIG. 7B shows capacitor voltages vcr1, vcr2, vcr3 of the r-phase unit converter. C) shows the reactive power output command q * .
無効電力の停止状態が続くと、図７（Ｂ）に示すｖcr1〜ｖcr3のように、部品の個体差等によって生じるコンデンサ電圧の段間アンバランスが大きく広がり、コンデンサ電圧の定格値から著しく乖離したコンデンサが生じて、変換器全体としての出力電圧に歪みが発生する虞がある。出力電圧の歪みは電流歪みにつながり、系統を介して周辺機器へ悪影響を与える。 When the reactive power stops, the capacitor voltage unbalance due to individual differences of parts greatly increases as shown in FIG. 7B, and the output voltage deviates significantly from the rated value of the capacitor voltage. A capacitor may be generated, and distortion may occur in the output voltage of the entire converter. Output voltage distortion leads to current distortion, and adversely affects peripheral devices through the system.
停止中の直流コンデンサ電圧の制御については、特許文献１や特許文献２のように外部電源から充電する方法がある。
図８は、前記特許文献に記載された技術を用い、電源５１から変圧器５２を介して得た電力を、充電回路５３によりインバータ５４の直流コンデンサ５５に充電する場合の手法を示す。同図でインバータ５４は、系統ｖsに対して連系インピーダンス５６、変圧器５７を介して接続されている。
As for control of the DC capacitor voltage during the stop, there is a method of charging from an external power source as in Patent Document 1 and Patent Document 2.
FIG. 8 shows a technique in which the electric power obtained from the power supply 51 via the transformer 52 is charged to the DC capacitor 55 of the inverter 54 by the charging circuit 53 using the technique described in the patent document. In the figure, the inverter 54 is connected to the system vs via a connection impedance 56 and a transformer 57.
このような手法は、電源５１や変圧器５２、充電回路５３といった追加回路が別途必要となるため、前述のとおり直列段数が多いＭＭＣ回路のような用途においては非現実的である。 Such a method requires additional circuits such as the power supply 51, the transformer 52, and the charging circuit 53, and thus is unrealistic in applications such as an MMC circuit having a large number of series stages as described above.
本発明は上記のような実情に鑑みてなされたもので、追加の回路を必要とせず、負荷運転の停止中もコンデンサ電圧を定格値に保ち、変換器の電流歪みを抑制することを目的とする。 The present invention has been made in view of the above circumstances, and does not require an additional circuit, and aims to keep a capacitor voltage at a rated value even during a stop of load operation and to suppress current distortion of a converter. To do.
実施形態に係る電力変換装置は、各相毎に半導体スイッチング素子及びコンデンサを含む単位電力変換器を複数直列接続し、両端を電圧源に接続した、複数相分のレグと、前記単位電力変換器を制御して所定の電圧を出力させる制御部とを備える電力変換装置において、前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで負荷電力に影響を与えない電流ルートに電流を流すことを特徴とする。
実施形態に係る他の電力変換装置は、各相毎に半導体スイッチング素子及びコンデンサを含む単位電力変換器を複数直列接続し、両端を電圧源に接続した、複数相分のデルタ結線を構成するレグと、前記単位電力変換器を制御して所定の電圧を出力させる制御部とを備える電力変換装置において、前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで零相電流ルートに電流を流すことを特徴とする。
実施形態に係るさらに他の電力変換装置は、各相毎に半導体スイッチング素子及びコンデンサを含む単位電力変換器を複数直列接続し、両端を直流電圧源に接続し、中間点から交流出力端子を引き出した、複数相分のレグと、前記単位電力変換器を制御して所定の電圧を出力させる制御部とを備える電力変換装置において、前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで交流側に流れない循環電流ルートに電流を流すことを特徴とする。
A power conversion device according to an embodiment includes a plurality of unit power converters each including a semiconductor switching element and a capacitor for each phase, connected in series, and connected to a voltage source at both ends, and the unit power converter And a control unit that controls the output of a predetermined voltage, and the control unit includes a capacitor included in the unit power converter according to the balance in the phase while stopping the current output to the load. The current is caused to flow in a current route that includes the leg and does not affect the load power so that the voltage of the current is the same in the same phase.
Another power conversion device according to the embodiment is a leg that forms a delta connection for a plurality of phases in which a plurality of unit power converters including semiconductor switching elements and capacitors are connected in series for each phase, and both ends are connected to a voltage source. And a control unit that controls the unit power converter and outputs a predetermined voltage, the control unit, while stopping the current output to the load, according to the balance in the phase A current is caused to flow through the zero-phase current route including the leg so that the voltage of the capacitor included in the unit power converter is the same in the same phase.
Still another power conversion device according to the embodiment connects a plurality of unit power converters including a semiconductor switching element and a capacitor for each phase in series, connects both ends to a DC voltage source, and draws an AC output terminal from an intermediate point. In addition, in the power conversion device including a leg for a plurality of phases and a control unit that controls the unit power converter to output a predetermined voltage, the control unit is configured to perform a phase while stopping the current output to the load. A current is caused to flow through a circulating current route that includes the leg and does not flow to the AC side so that the voltage of the capacitor included in the unit power converter becomes the same in the same phase according to the balance.
本発明によれば、追加の回路を必要とせず、負荷運転の停止中もコンデンサ電圧を定格値に保ち、変換器の電流歪みを抑制することが可能となる。 According to the present invention, an additional circuit is not required, and the capacitor voltage can be kept at the rated value even when the load operation is stopped, thereby suppressing the current distortion of the converter.
以下、本発明の実施形態について、詳細に説明する。
（第１の実施形態）
図１は、第１の実施形態に係る、デルタ結線の無効電力補償装置に適用した電力変換器の全体構成を示す図である。なお、後述する第２の実施形態以下においても、図１に示す電力変換器の構成要素と同一、または相当する構成要素には、図１で使用した符号と同一の符号を付して説明する。
Hereinafter, embodiments of the present invention will be described in detail.
(First embodiment)
FIG. 1 is a diagram illustrating an overall configuration of a power converter applied to a reactive power compensator for delta connection according to the first embodiment. In the second and subsequent embodiments to be described later, the same or corresponding components as those of the power converter shown in FIG. 1 are denoted by the same reference numerals as those used in FIG. .
この電力変換器では、４つのスイッチング素子３１と、直流電圧源としてのコンデンサ３２とにより構成された単相フルブリッジ構成の単位変換器３を、ｒ，ｓ，ｔの各相毎にｎ段直列接続してレグ２を構成し、さらに当該レグ２とリアクトル４とを直列接続し、それら３相分をデルタ結線して電力変換部１を構成する。そして、この電力変換部１内の各単位変換器３を制御する制御部５を備える。 In this power converter, unit converters 3 having a single-phase full-bridge configuration including four switching elements 31 and a capacitor 32 as a DC voltage source are connected in series in n stages for each of r, s, and t phases. The leg 2 is connected, and the leg 2 and the reactor 4 are connected in series, and the power conversion unit 1 is configured by delta connection of the three phases. And the control part 5 which controls each unit converter 3 in this electric power conversion part 1 is provided.
本実施形態では、前述した如くデルタ結線の無効電力補償装置に適用した場合の例であるため、電力変換部１を構成する各相の変換器は、変圧器６を介して、３相交流電源７を含む電力系統ｖsに連系させている。 Since the present embodiment is an example of application to the reactive power compensator of delta connection as described above, the converter of each phase constituting the power converter 1 is a three-phase AC power source via the transformer 6. 7 is connected to the electric power system vs. 7.
前記リアクトル４は、変換器でスイッチングに伴って瞬時的に生じる線間短絡の際の電流増加を抑制する。 The reactor 4 suppresses an increase in current at the time of a short circuit between lines that occurs instantaneously with switching in the converter.
前記制御部５は、系統電圧ｖsr，ｖss，ｖst、変換器電流ｉrs，ｉst，ｉtr、コンデンサ電圧ｖcr1〜ｖcrn，ｖcs1〜ｖcsn，ｖct1〜ｖctnに基づいて、各相の電圧指令値ｖr*，ｖs*，ｖr*を演算し、それらに基づいて実際に各スイッチング素子３１を駆動するゲート信号を出力する。また制御部５は、単位変換器３が備えるコンデンサ３２の電圧を定格値ｖc*に維持するため、各種電圧制御、具体的には全体の電圧制御、相間のバランス制御、及び段間のバランス制御等を行なう。 The control unit 5 determines the voltage command values vr * and vs for each phase based on the system voltages vsr, vss, vst, the converter currents irs, ist, itr, and the capacitor voltages vcr1 to vcrn, vcs1 to vcsn, vct1 to vctn. * And vr * are calculated, and a gate signal for actually driving each switching element 31 is output based on these. Further, the control unit 5 performs various voltage controls, specifically, overall voltage control, balance control between phases, and balance control between stages in order to maintain the voltage of the capacitor 32 provided in the unit converter 3 at the rated value vc *. Etc.
これらの電圧制御のうち、全体の電圧制御は、制御部５が系統ｖsと電力変換部１の間の有効電流を制御し、電力変換部１が備える全てのコンデンサ電圧の平均値を定格値ｖc*に一致させる。 Among these voltage controls, the overall voltage control is such that the control unit 5 controls the effective current between the system vs and the power conversion unit 1, and the average value of all capacitor voltages provided in the power conversion unit 1 is the rated value vc. Match with *.
図２は、制御部５が実行する相間のバランス制御の内容を示す。同図に示すように制御部５は、各相のコンデンサ電圧平均値をバランスさせる。各相のレグ２が備えるｎ個のコンデンサ３２の平均電圧が相間で異なる場合、制御部５は同図２に示すように電力変換部１のデルタ結線部を循環する零相電流ｉ0を流すことで、相間の電力がアンバランスとなるようにして、各相のコンデンサ電圧平均値を制御する。 FIG. 2 shows the content of balance control between phases executed by the control unit 5. As shown in the figure, the control unit 5 balances the capacitor voltage average value of each phase. When the average voltage of the n capacitors 32 included in the legs 2 of each phase differs between the phases, the control unit 5 causes the zero-phase current i0 to circulate through the delta connection portion of the power conversion unit 1 as shown in FIG. Thus, the capacitor voltage average value of each phase is controlled so that the power between the phases is unbalanced.
例えば零相電流ｉ0が交流で、その位相がｒ相のレグ２の出力電圧ｖrと一致している場合、当該ｒ相は有効電力が流出してコンデンサ電圧の平均値が減少する。その一方で、三相平衡電圧であれば、ｓ相とｔ相には有効電力が流入してコンデンサ電圧の平均値が増加する。このように、相間のバランス制御では、零相電流ｉ0の大きさと位相によってコンデンサ電圧の相間のバランスを制御する。 For example, when the zero-phase current i0 is alternating current and the phase thereof matches the output voltage vr of the r-phase leg 2, the active power flows out of the r-phase, and the average value of the capacitor voltage decreases. On the other hand, in the case of a three-phase balanced voltage, active power flows into the s phase and the t phase, and the average value of the capacitor voltage increases. Thus, in the balance control between the phases, the balance between the phases of the capacitor voltage is controlled by the magnitude and the phase of the zero-phase current i0.
段間のバランス制御は、各相の個々のコンデンサ電圧をバランスさせる。ある相のレグ２が備えるｎ個のコンデンサ３２の電圧が同レグ２内でアンバランスである場合、各単位変換器３の出力電圧を個別に制御する。 Balance control between stages balances the individual capacitor voltage of each phase. When the voltages of the n capacitors 32 included in the leg 2 of a certain phase are unbalanced in the leg 2, the output voltage of each unit converter 3 is individually controlled.
例えば、ｒ相のレグ２の１段目の単位変換器３のコンデンサ電圧が同レグ２中で高い場合、制御部５は同単位変換器３への電圧指令値ｖr1*に、変換器電流ｉrsと同位相の制御量を加算する。すると同単位変換器３から有効電力が流出し、同単位変換器３のコンデンサ電圧は低下する。同レグ２内の制御量の合計が零であれば、当該相の合計コンデンサ電圧または平均値には影響しない。このように段間のバランス制御は、制御部５が個別の電圧指令値でコンデンサ電圧の段間のバランスを制御する。 For example, when the capacitor voltage of the unit converter 3 in the first stage of the r-phase leg 2 is high in the leg 2, the control unit 5 sets the converter current irs to the voltage command value vr1 * to the unit converter 3. The control amount in the same phase as is added. Then, active power flows out from the unit converter 3, and the capacitor voltage of the unit converter 3 decreases. If the total amount of control in the leg 2 is zero, the total capacitor voltage or average value of the phase is not affected. Thus, in the balance control between the stages, the control unit 5 controls the balance between the stages of the capacitor voltage with the individual voltage command values.
図３は、制御部５による段間のバランス制御の過程を示す図である。本実施形態による段間のバランス制御において、制御部５は図３（Ｄ）に示すように、無効電力の出力停止時に段間のバランス制御のため零相電流指令値ｉ0*を与える。 FIG. 3 is a diagram illustrating a process of balance control between stages by the control unit 5. In the balance control between the stages according to the present embodiment, as shown in FIG. 3D, the control unit 5 gives a zero-phase current command value i0 * for balance control between the stages when the reactive power output is stopped.
図３（Ｃ）に示すように、無効電力指令ｑ*をタイミングｔ0の時点で停止させ、同時点以降は零として無効電力の出力を停止したものとする。 As shown in FIG. 3C, it is assumed that the reactive power command q * is stopped at the timing t0, and the output of reactive power is stopped after the simultaneous point with zero.
前記零相電流は流れるものの、電流量が微小であるために段間のバランス制御は有効に作用せず、図３（Ｂ）に示すようにｒ相を構成する複数段、例えば３段の単位変換器３のコンデンサ電圧ｖcr1，ｖcr2，ｖcr3は時間の経過と共にそれぞれ個体差に応じてアンバランスな状態となる。 Although the zero-phase current flows, since the amount of current is very small, the balance control between the stages does not work effectively. As shown in FIG. The capacitor voltages vcr1, vcr2, and vcr3 of the converter 3 are in an unbalanced state according to individual differences as time passes.
そのうち、例えば３段目の単位変換器３のコンデンサ電圧ｖcr3が、定格コンデンサ電圧値ｖc*に対して予め設定されている下限の閾値ｖclimと等しくなった場合、制御部５ではその状態を検出し、図３（Ｄ）に示すようにタイミングｔ1の時点から、ピーク電流ｉ0bとなるような零相電流指令ｉ0*を与える。ここでピーク電流ｉ0bは、段間のバランス制御を有効に作用させることができる零相電流量である。 For example, when the capacitor voltage vcr3 of the unit converter 3 at the third stage becomes equal to the lower limit threshold value vclim set in advance with respect to the rated capacitor voltage value vc * , the controller 5 detects the state. As shown in FIG. 3 (D), a zero-phase current command i0 * that gives a peak current i0b is given from the timing t1. Here, the peak current i0b is a zero-phase current amount capable of effectively performing balance control between stages.
ピーク電流ｉ0b〜−ｉ0b間で正弦波状に変位する零相電流ｉ0が当該レグ２に流れることにより、当該レグ２内の段間のバランス制御が作用して、タイミングｔ2の時点でコンデンサ電圧ｖcr1〜ｖcr3が収束して一致し、段間のバランスが成立する。 A zero-phase current i0 that is displaced in a sine wave shape between the peak currents i0b to -i0b flows into the leg 2, whereby the balance control between the stages in the leg 2 acts, and at the time t2, the capacitor voltage vcr1 to vcr3 converges and matches, and a balance between stages is established.
しかし零相電流ｉ0は相間バランスを制御するものであるため、図３（Ａ）に示すように各相のコンデンサ電圧平均値ｖcr，ｖcs，ｖctはそれまでのバランスした状態からアンバランスな状態に変化している。 However, since the zero-phase current i0 controls the balance between phases, as shown in FIG. 3A, the average capacitor voltage values vcr, vcs, vct of each phase are changed from the balanced state to the unbalanced state. It has changed.
タイミングｔ2の時点で、ｒ相の各コンデンサ電圧ｖcr1〜ｖcr3が指令値ｖc*と一致していないのは、相間にアンバランスが生じてｒ相のコンデンサ電圧平均値ｖcrが低下しているためである。 The reason why the r-phase capacitor voltages vcr1 to vcr3 do not coincide with the command value vc * at the timing t2 is that the r-phase capacitor voltage average value vcr is lowered due to imbalance between the phases. is there.
これを是正するため制御部５は、図３（Ｄ）に示すようにタイミングｔ2の時点からタイミングｔ3の時点の間、それまでと逆方向の零相電流指令ｉ0*を与える。この場合は、タイミングｔ1の時点からタイミングｔ2の時点に与えた零相電流指令ｉ0*に対し、位相を反転して、各相の有効電力の流入／流出関係を逆としたものを与える。 In order to correct this, as shown in FIG. 3D, the controller 5 gives a zero-phase current command i0 * in the opposite direction from the time t2 to the time t3. In this case, the phase is inverted with respect to the zero-phase current command i0 * given from the timing t1 to the timing t2, and the inflow / outflow relationship of the active power of each phase is reversed.
このような統括した制御により、コンデンサ電圧の段間のバランスがとれると共に、相間のバランスもとれることになる。タイミングｔ3の時点で相間のコンデンサ電圧もバランスするため、その後に零相電流ｉ0を流す必要はない。 By such integrated control, the capacitor voltage stages can be balanced and the phases can be balanced. Since the capacitor voltage between the phases is also balanced at the timing t3, it is not necessary to flow the zero-phase current i0 thereafter.
このように、制御部５は無効電力指令ｑ*を停止しても、相間のバランス制御のために零相電流ｉ0を調整し、図３（Ａ）に示すようにｒ相のコンデンサ電圧平均値ｖcr、ｓ相のコンデンサ電圧平均値ｖcs、ｔ相のコンデンサ電圧平均値ｖctをバランスさせて、定格コンデンサ電圧値ｖc*に一致させることができる。 Thus, even if the reactive power command q * is stopped, the control unit 5 adjusts the zero-phase current i0 for balance control between the phases, and the r-phase capacitor voltage average value as shown in FIG. It is possible to balance vcr, the s-phase capacitor voltage average value vcs, and the t-phase capacitor voltage average value vct so as to match the rated capacitor voltage value vc * .
以上に詳述した如く本実施形態によれば、無効電力の出力停止中も各単位変換器３のコンデンサ電圧を全て定格値ｖc*となるように制御することができるため、電力変換部１の出力電圧と出力電流の双方に歪みを生じない。 As described in detail above, according to the present embodiment, the capacitor voltage of each unit converter 3 can be controlled so as to all become the rated value vc * even when the reactive power output is stopped. No distortion occurs in both output voltage and output current.
なお本実施形態ではｒ相での制御を例にとって説明したが、他のｓ相、ｔ相の制御についても同様である。 In this embodiment, the control in the r phase has been described as an example, but the same applies to the control in the other s phase and t phase.
段間のバランスをとるための零相電流指令ｉ0*の大きさ(±)ｉ0bは、小さすぎると段間のバランスを制御できない。また大きすぎても相間のアンバランスが過大になるため、段間のバランスを制御できる最小値であることが望ましい。最小値は計算や実験から求められ、制御上の定数として与えられる。 If the magnitude (±) i0b of the zero-phase current command i0 * for balancing the stages is too small, the balance between the stages cannot be controlled. Moreover, since the imbalance between phases becomes excessive even if it is too large, it is desirable that the value be the minimum value that can control the balance between stages. The minimum value is obtained from calculation or experiment and is given as a control constant.
また零相電流指令ｉ0*を与えるタイミングの判断としては、コンデンサ電圧を監視し、下限値ｖclimを下回るコンデンサが現れた時点としたが、無効電力の出力を停止してから所定の時間が経過した時点としても良い。 The timing of giving the zero-phase current command i0 * is determined when the capacitor voltage is monitored and a capacitor below the lower limit value vclim appears, but a predetermined time has elapsed since the output of reactive power was stopped. It is good as a time.
前記図３では、段間でバランスするタイミングｔ2の時点まで、相間でアンバランスな状態となる方向の零相電流指令ｉ0*を与え、その後、逆に相間がバランスする方向の零相電流指令ｉ0*を与えているが、アンバランスな状態となる方向の後にバランスする方向への零相電流を流すことを見越して、段間で完全にバランスする前に、バランス方向の零相電流指令ｉ0*を与えることで、制御に要する時間をより短縮できる。 In FIG. 3, the zero-phase current command i0 * is given in a direction in which the phases are unbalanced until the timing t2 at which the phases are balanced, and then the zero-phase current command i0 in the direction in which the phases are balanced. * , But in anticipation of flowing the zero-phase current in the direction of balancing after the direction of the unbalanced state, the zero-phase current command i0 * By giving, the time required for control can be further shortened.
また、零相電流ｉ0が相間でアンバランスとなる方向と、相間でバランスする方向の１回の組合せ制御で段間をバランスさせずに、複数回に分けて前記組合せの零相電流ｉ0を流して段間でバランスさせても良い。また最初に相間がバランスしていない場合は、バランスする方向の零相電流ｉ0を流して段間のバランスを制御しても良い。 Also, the zero-phase current i0 of the combination is divided into a plurality of times without balancing the stages by one combination control in the direction in which the zero-phase current i0 is unbalanced between the phases and the direction in which the phases are balanced. You may balance between steps. If the phases are not balanced at first, the balance between the stages may be controlled by supplying a zero-phase current i0 in the direction of balancing.
また無効電力を出力しても問題ない場合は、零相電流ｉ0を流す代わりに、段間のバランスをとるために無効電流指令を与えて電流を流しても構わない。レグ２に十分な大きさの無効電流が流れることで、段間のバランス制御が作用する。 If there is no problem even if reactive power is output, instead of supplying the zero-phase current i0, a reactive current command may be given to flow the current in order to balance the stages. When a sufficiently large reactive current flows in the leg 2, the balance control between the stages acts.
また前記図１及び図２では、各相において直列接続された複数段の単位変換器３をデルタ結線した電力変換部１を例にとって説明しているが、Ｙ結線であってもよい。 1 and 2, the power conversion unit 1 in which a plurality of unit converters 3 connected in series in each phase is delta-connected is described as an example, but Y-connection may be used.
また全ての実施形態の共通事項として、図１ではリアクトル４を各相に入れているが、これを用いずに変圧器６の漏れリアクタンスで代用しても構わない。また前記図１では変圧器６を介して電力系統ｖsに連系しているが、変圧器６を介さずに連系してもよい。また前記図１では制御部５は変換器電流ｉrs，ｉst，ｉtrに基づいて制御しているが、系統電流ｉr，ｉs，ｉtに基づいて制御するものとしてもよい。 Moreover, as a common matter of all the embodiments, the reactor 4 is included in each phase in FIG. 1, but the leakage reactance of the transformer 6 may be used instead of this. In FIG. 1, the power system vs is connected via the transformer 6, but the power system vs may be connected without the transformer 6. In FIG. 1, the control unit 5 controls based on the converter currents irs, ist, itr, but may control based on the system currents ir, is, it.
（第２の実施形態）
以下、第２の実施形態に係る電力変換器について説明する。
図４は、ＨＶＤＣ変換器などに使用するＤＣ／ＡＣ変換器に本実施形態を適用した場合の電力変換部１′の構成を示す図である。なお、以下においては、前記図１に示す電力変換部１の構成要素と同一または相当する構成要素には、図１で使用した符号と同一の符号を付して説明する。
(Second Embodiment)
Hereinafter, a power converter according to the second embodiment will be described.
FIG. 4 is a diagram showing a configuration of the power conversion unit 1 ′ when the present embodiment is applied to a DC / AC converter used for an HVDC converter or the like. In the following description, the same or equivalent components as those of the power conversion unit 1 shown in FIG. 1 are denoted by the same reference numerals as those used in FIG.
この電力変換部１′において、２つの半導体スイッチング素子３１と、直流電圧源としてのコンデンサ３２により構成されたハーフブリッジ構成の単位変換器３′を複数段分、直列接続してレグ２を構成する。 In this power conversion unit 1 ′, a leg 2 is formed by connecting a plurality of stages of unit converters 3 ′ having a half bridge configuration including two semiconductor switching elements 31 and a capacitor 32 as a DC voltage source. .
ｒ相、ｓ相、ｔ相の３相共、前記レグ２とリアクトル４を直列接続した回路を２つ直列に接続して構成し、直流電圧源Ｖdcに対してこれら３相を並列接続する。各相それぞれを上レグ、下レグに分けて考えた場合、その中間点から交流出力端子を引き出して電力変換部１′を構成するものとし、この電力変換部１′を制御する制御部５′を備える。 In each of the three phases of r phase, s phase, and t phase, two circuits in which the leg 2 and the reactor 4 are connected in series are connected in series, and these three phases are connected in parallel to the DC voltage source Vdc. When each phase is divided into an upper leg and a lower leg, an AC output terminal is drawn from the middle point to constitute a power converter 1 ', and a controller 5' for controlling this power converter 1 '. Is provided.
本実施形態では、各相に単位変換器３′をｎ個ずつ備えている。前述した如く本実施形態では、ＨＶＤＣ変換器などに使用するＤＣ／ＡＣ変換器を例に想定しているが、ＡＣ／ＤＣ変換器であっても回路構成は本実施形態と同様である。ＤＣ／ＡＣ変換器は、直流側と交流側で電力をやり取りする。交流直流間での電力のやり取りが無い場合は負荷電流は流れない。 In this embodiment, n unit converters 3 'are provided for each phase. As described above, in the present embodiment, a DC / AC converter used for an HVDC converter or the like is assumed as an example, but the circuit configuration is the same as that of the present embodiment even in the case of an AC / DC converter. The DC / AC converter exchanges power between the direct current side and the alternating current side. When there is no exchange of power between AC and DC, no load current flows.
前記リアクトル４は、単位変換器３′のスイッチングに伴って瞬時的に生じる線間短絡の際の電流増加を抑制する。 The reactor 4 suppresses an increase in current at the time of a short circuit between lines that occurs instantaneously with the switching of the unit converter 3 '.
制御部５′は、電圧ｖac，ｖdc、電流ｉrp，ｉrn，ｉsp，ｉsn，ｉtp，ｉtn、コンデンサ電圧ｖcr1〜ｖcrn，ｖcs1〜ｖcsn，ｖct1〜ｖctnに基付いて各相の電圧指令値ｖr*，ｖs*，ｖt*を演算し、それに基付いて実際に各スイッチング素子３１を駆動するゲート信号を出力する。また、単位変換器３′が備えるコンデンサ３２の電圧を定格値ｖc*に維持するため、各種電圧制御を行なう。 The control unit 5 'determines the voltage command values vr * , vr * , vct, dc, currents rp, irn, isp, isn, itp, itn, capacitor voltages vcr1 to vcrn, vcs1 to vcsn, vct1 to vctn. VS * and VT * are calculated, and a gate signal for actually driving each switching element 31 is output based on the calculation. Various voltage controls are performed to maintain the voltage of the capacitor 32 provided in the unit converter 3 'at the rated value vc * .
図５は、制御部５′による電圧制御の過程を、電力変換部１′の１相分のみを抽出して示す図である。各相の上下レグ２の備える合計ｎ個のコンデンサ３２の平均電圧を制御するため、制御部５′は図示するように電源と変換器側を通る循環電流ｉ0を流す。この循環電流ｉ0は交流ｖac側に流れないため、負荷電力に影響なく制御することができる。 FIG. 5 is a diagram illustrating a voltage control process by the control unit 5 ′ by extracting only one phase of the power conversion unit 1 ′. In order to control the average voltage of a total of n capacitors 32 provided in the upper and lower legs 2 of each phase, the control unit 5 'causes a circulating current i0 to flow through the power supply and the converter side as shown in the figure. Since this circulating current i0 does not flow to the AC vac side, it can be controlled without affecting the load power.
例えばｒ相の上下レグ２のコンデンサ電圧の平均値ｖcrが定格値ｖc*より低い場合、ｒ相に正の循環電流ｉ0rを流すことで有効電力が流入し、同レグ２のコンデンサ電圧の平均値ｖcrが増加する。このように制御部５′は、循環電流ｉ0の大きさにより各レグのコンデンサ電圧平均値を制御する。 For example, when the average value vcr of the capacitor voltage of the upper and lower legs 2 of the r phase is lower than the rated value vc *, the active power flows in by flowing a positive circulating current i0r to the r phase, and the average value of the capacitor voltage of the same leg 2 vcr increases. Thus, the control unit 5 'controls the average capacitor voltage value of each leg according to the magnitude of the circulating current i0.
上下各レグ２の備える計ｎ個のコンデンサ３２の電圧が同相内でアンバランスとなった場合、各単位変換器３′の出力電圧を個別に制御する。例えばｒ相１段目の単位変換器３′のコンデンサ電圧が同レグ２の中で低い場合、電流ｉrpが正であれば、同単位変換器３′の電圧指令値ｖr1*に、正の制御量を加算する。すると同単位変換器３′に有効電力が流入し、コンデンサ電圧は増加する。同相内の制御量の合計が零であれば、当該相の出力電圧には影響しない。このように、個別の電圧指令値でコンデンサ電圧の段間のバランスを制御する。 When the voltages of a total of n capacitors 32 provided in the upper and lower legs 2 are unbalanced in the same phase, the output voltage of each unit converter 3 'is individually controlled. For example, when the capacitor voltage of the unit converter 3 'in the first stage of the r phase is low in the leg 2, if the current irp is positive, the voltage command value vr1 * of the unit converter 3' is positively controlled. Add the amount. Then, active power flows into the unit converter 3 'and the capacitor voltage increases. If the total amount of control in the same phase is zero, the output voltage of the phase is not affected. In this way, the balance between the capacitor voltage stages is controlled by the individual voltage command values.
図６は、制御部５′が実行する、段間のバランス制御の過程を示す図である。制御部５′は図６（Ｄ）に示すように、無効電力の出力停止時に段間のバランス制御を行なうための循環電流指令値ｉ0*を与えている。 FIG. 6 is a diagram showing a process of balance control between stages executed by the control unit 5 ′. As shown in FIG. 6 (D), the control unit 5 'gives a circulating current command value i0 * for performing balance control between stages when reactive power output is stopped.
図６（Ｃ）に示す負荷電流ｉload*を停止したタイミングｔ0の時点で停止させ、同時点以降は零として負荷電流の出力を停止させている。負荷電流の出力を停止しても、循環電流ｉ0が制御され、ｒ相のレグのコンデンサ電圧平均値ｖcrは定格コンデンサ電圧値ｖc*に一致する。 The load current iload * shown in FIG. 6C is stopped at the timing t0 when the load current iload * is stopped, and the output of the load current is stopped as zero after the simultaneous point. Even when the output of the load current is stopped, the circulating current i0 is controlled, and the capacitor voltage average value vcr of the r-phase leg matches the rated capacitor voltage value vc * .
この場合、循環電流ｉ0は流れるものの、その値が微小であるために段間のバランス制御は有効に作用せず、ｒ相を構成する複数段、例えば３段の単位変換器３′のコンデンサ電圧ｖcr1，ｖcr2，ｖcr3は時間の経過と共にそれぞれ個体差に応じてアンバランスとなる。 In this case, although the circulating current i0 flows, the value thereof is very small, so that balance control between stages does not work effectively, and the capacitor voltage of a plurality of stages, for example, three-stage unit converters 3 'constituting the r phase. vcr1, vcr2, and vcr3 become unbalanced according to individual differences over time.
そのうち、例えば３段目の単位変換器３のコンデンサ電圧ｖcr3が、定格コンデンサ電圧値ｖc*に対して予め設定されている下限の閾値ｖclimと等しくなった場合、制御部５′ではその状態を検出し、図６（Ｄ）に示すようにタイミングｔ1の時点から、ピーク電流−ｉ0bとなるような循環電流指令ｉ0*を与える。ここでピーク電流ｉ0bは、段間のバランス制御を有効に作用させることができる循環電流量である。 Among them, for example, when the capacitor voltage vcr3 of the unit converter 3 in the third stage becomes equal to the lower limit threshold value vclim set in advance with respect to the rated capacitor voltage value vc * , the controller 5 'detects the state. Then, as shown in FIG. 6D, a circulating current command i0 * that gives a peak current −i0b is given from the timing t1. Here, the peak current i0b is an amount of circulating current that can effectively cause balance control between stages.
ピーク電流−ｉ0bとなる循環電流ｉ0が当該レグ２に流れることにより、当該レグ２内の段間のバランス制御が作用して、タイミングｔ2の時点でコンデンサ電圧ｖcr1〜ｖcr3が収束して一致し、段間のバランスが成立する。 When the circulating current i0 having the peak current -i0b flows through the leg 2, the balance control between the stages in the leg 2 acts, and the capacitor voltages vcr1 to vcr3 converge and coincide at the timing t2. Balance between steps is established.
しかし循環電流ｉ0は、上下各レグ２のコンデンサ電圧の平均値を制御するものであるため、図６（Ａ）に示すようにコンデンサ電圧の平均値ｖcrはそれまでのバランスした定格値からアンバランスな状態に変化している。 However, since the circulating current i0 controls the average value of the capacitor voltage of the upper and lower legs 2, the average value vcr of the capacitor voltage is unbalanced from the balanced rated value so far as shown in FIG. It has changed to a different state.
タイミングｔ2の時点で、ｒ相の各コンデンサ電圧ｖcr1〜ｖcr3が指令値ｖc*と一致していないのは、相間にアンバランスが生じてｒ相のコンデンサ電圧の平均値ｖcrが低下しているためである。 The reason why the r-phase capacitor voltages vcr1 to vcr3 do not coincide with the command value vc * at the timing t2 is that an imbalance occurs between the phases and the average value vcr of the r-phase capacitor voltage is lowered. It is.
これを是正するために制御部５′は、図６（Ｄ）に示すようにタイミングｔ2の時点からタイミングｔ3の時点の間、それまでと逆方向の零相電流指令ｉ0*を与える。この場合は、タイミングｔ1の時点からタイミングｔ2の時点に与えた零相電流指令ｉ0*に対し、正負を反転して、各相の有効電力の流入／流出関係を逆としたものを与える。 In order to correct this, as shown in FIG. 6 (D), the control unit 5 'gives a zero-phase current command i0 * in the reverse direction from the timing t2 to the timing t3. In this case, with respect to the zero-phase current command i0 * given from the time point t1 to the time point t2, the positive / negative is reversed and the inflow / outflow relationship of the active power of each phase is reversed.
このような統括した制御により、コンデンサ電圧の平均値も、段間のバランスもとれた状態となる。タイミングｔ3の時点でレグ２のコンデンサ電圧の平均値ｖcがその定格値ｖc*に一致していれば、その後は循環電流ｉ0rを流す必要はない。 By such integrated control, the average value of the capacitor voltage is also balanced. If the average value vc of the capacitor voltage of the leg 2 coincides with the rated value vc * at the timing t3, it is not necessary to flow the circulating current i0r thereafter.
以上に詳述した如く本実施形態によれば、制御部５′は負荷電流の出力を停止しても、コンデンサ電圧をすべて定格値ｖc*となるように制御できるため、電力変換部１′の出力電圧ｖacと出力電流ｉrの双方に歪みを生じない。 As described above in detail, according to the present embodiment, the control unit 5 ′ can control all the capacitor voltages to the rated value vc * even when the output of the load current is stopped. No distortion occurs in both the output voltage vac and the output current ir.
なお本実施形態ではｒ相での制御を例にとって説明したが、他のｓ相、ｔ相の制御についても同様である。 In this embodiment, the control in the r phase has been described as an example, but the same applies to the control in the other s phase and t phase.
段間のバランスをとるための循環電流指令ｉ0*の大きさ(±)ｉ0bは、小さすぎると段間のバランスを制御できない。また大きすぎてもレグ２のコンデンサ電圧の平均値の変化が過大になるため、段間のバランスを制御できる最小値であることが望ましい。この最小値は計算や実験から求められ、制御上の定数として与えられる。 If the magnitude (±) i0b of the circulating current command i0 * for balancing the stages is too small, the balance between the stages cannot be controlled. Moreover, since the change of the average value of the capacitor voltage of the leg 2 becomes excessive even if it is too large, it is desirable that the value be the minimum value that can control the balance between stages. This minimum value is obtained from calculation or experiment and is given as a control constant.
また循環電流指令ｉ0*を与えるタイミングの判断としては、コンデンサ電圧を監視し、下限値ｖclimを下回るコンデンサが現れた時点としたが、同様に上限値を設定し、あるいは負荷電流の電力の出力を停止してから所定の時間が経過した時点としても良い。 The timing of giving the circulating current command i0 * is determined by monitoring the capacitor voltage and when a capacitor below the lower limit value vclim appears. Similarly, the upper limit value is set or the output of the load current power is set. It may be the time when a predetermined time has passed since the stop.
前記図６では、段間でバランスするタイミングｔ2の時点まで、平均値が減少する方向の循環電流指令ｉ0*を与え、その後、逆に平均値が増加する方向の循環電流指令ｉ0*を与えているが、平均値が減少する方向の後に平均値が増加する方向への循環電流を流すことを見越して、段間で完全にバランスする前に、平均値が増加する方向の循環電流指令ｉ0*を与えることで、制御に要する時間をより短縮できる。 In FIG. 6, the circulating current command i0 * in the direction in which the average value decreases is given until the timing t2 when balancing between the stages, and then the circulating current command i0 * in the direction in which the average value increases is given. However, in anticipation of flowing the circulating current in the direction in which the average value increases after the direction in which the average value decreases, the circulating current command i0 * in the direction in which the average value increases before completely balancing between stages . By giving, the time required for control can be further shortened.
また、循環電流ｉ0の平均値が減少する方向と、平均値が増加する方向の１回の組合せ制御で段間をバランスさせずに、複数回に分けて前記組合せの循環電流ｉ0を流して段間でバランスさせても良い。また最初にレグ２のコンデンサ電圧の平均値が定格値でない場合は、定格値制御を行なう方向の循環電流ｉ0を流して段間のバランスを制御しても良い。さらに循環電流ｉ0は、はじめに平均値が増加する方向に流し、その後に平均値が減少する方向に流しても構わない。 In addition, the combination of the circulating current i0 in the direction in which the average value of the circulating current i0 decreases and the combination control in one direction in which the average value increases does not balance the stages, and the circulating current i0 of the combination is supplied in multiple steps. You may balance between them. Further, when the average value of the capacitor voltage of the leg 2 is not the rated value at first, the balance between the stages may be controlled by supplying the circulating current i0 in the direction of performing the rated value control. Further, the circulating current i0 may flow first in the direction in which the average value increases, and then flow in the direction in which the average value decreases.
また負荷電流を出力しても問題ない場合は、循環電流ｉ0を流す代わりに、段間のバランスをとるために負荷電流指令ｉload*を与えて電流を流しても構わない。レグ２に十分な大きさの電流が流れることで、段間のバランス制御が作用する。 If there is no problem even if the load current is output, instead of supplying the circulating current i0, the current may be supplied by giving a load current command iload * to balance the stages. When a sufficiently large current flows in the leg 2, the balance control between the stages acts.
（第３の実施形態）
以下、第３の実施形態に係る電力変換器について簡単に説明する。
本実施形態に係る電力変換器の構成と動作は、前記第１の実施形態及び第２の実施形態と基本的に同様である。ただし、変換器１と交流系は、前記図１に示した如く変圧器６を介して電力系統ｖsと接続されるものとする。
(Third embodiment)
Hereinafter, the power converter according to the third embodiment will be briefly described.
The configuration and operation of the power converter according to the present embodiment are basically the same as those in the first and second embodiments. However, the converter 1 and the AC system are connected to the power system vs through the transformer 6 as shown in FIG.
本実施形態では、前記第１及び第２の実施形態と異なり、制御部５が段間のバランス制御のために流す電流を、変圧器６の励磁電流とする。 In the present embodiment, unlike the first and second embodiments, the current that the control unit 5 flows for balance control between stages is used as the exciting current of the transformer 6.
本実施形態によれば、負荷電流の出力停止中もコンデンサ電圧を全て定格値ｖc*に制御することができるため、変圧器６の出力電圧、そして電流に歪みを生じない。 According to the present embodiment, since all capacitor voltages can be controlled to the rated value vc * even when the output of the load current is stopped, the output voltage and current of the transformer 6 are not distorted.
変圧器６の励磁電流が、レグ２を構成する単位変換器３の各段間のバランス制御を作用させることができる程度の大きさである場合に、本実施形態の方式を適用できる。第１の実施形態で用いた零相電流や第２の実施形態で用いた循環電流のように、制御部５が特別な制御量を与えることなく、段間のバランス制御を実現できる利点がある。 The method of the present embodiment can be applied when the exciting current of the transformer 6 is large enough to allow balance control between each stage of the unit converter 3 constituting the leg 2. Like the zero-phase current used in the first embodiment and the circulating current used in the second embodiment, there is an advantage that balance control between stages can be realized without the control unit 5 giving a special control amount. .
以上、本発明のいくつかの実施形態を説明したが、これらの実施形態は、例として提示したものであり、発明の範囲を限定することは意図していない。これら実施形態は、その他の様々な形態で実施されることが可能であり、発明の趣旨を逸脱しない範囲で、種々の省略、置き換え、変更を行うことができる。これら実施形態やその変形は、発明の範囲や要旨に含まれると同様に、特許請求の範囲に記載された発明とその均等の範囲に含まれるものである。 As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.
１，１′…電力変換部、
２…レグ、
３，３′…単位変換器、
４…リアクトル、
５，５′…制御装置、
６…変圧器、
７…連系インピーダンス、
８…電源、
９…充電回路、
３１…半導体スイッチング素子、
３２…コンデンサ。
1, 1 '... power converter,
2 ... Leg,
3, 3 '... Unit converter,
4 ... Reactor,
5, 5 '... control device,
6 ... Transformer,
7 ... Interconnection impedance,
8 ... Power supply,
9 ... charging circuit,
31 ... Semiconductor switching element,
32: Capacitor.
Claims (10)
前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで負荷電力に影響を与えない電流ルートに電流を流すことを特徴とする電力変換装置。 A plurality of unit power converters including semiconductor switching elements and capacitors for each phase are connected in series, both ends are connected to a voltage source, and a plurality of phase legs and a predetermined voltage are output by controlling the unit power converter. A power conversion device comprising a control unit
The control unit includes the leg so that the voltage of the capacitor included in the unit power converter is the same in the same phase according to the balance in the phase while stopping the current output to the load. A power converter characterized by flowing a current through a current route that does not affect the power.
前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで零相電流ルートに電流を流すことを特徴とする電力変換装置。 A plurality of unit power converters including a semiconductor switching element and a capacitor for each phase are connected in series, and both ends are connected to a voltage source, a leg constituting a delta connection for a plurality of phases, and the unit power converter is controlled. In a power converter provided with a control unit that outputs a predetermined voltage,
The control unit includes the leg so that the voltage of the capacitor included in the unit power converter becomes the same in the same phase according to the balance in the phase while stopping the current output to the load. A power converter characterized by passing a current through a current route .
前記制御部は、負荷への電流出力を停止する間、相内のバランスに応じて前記単位電力変換器の備えるコンデンサの電圧が同一相内において同一となるように、当該レグを含んで交流側に流れない循環電流ルートに電流を流すことを特徴とする電力変換装置。 A plurality of unit power converters each including a semiconductor switching element and a capacitor for each phase are connected in series, both ends are connected to a DC voltage source, and an AC output terminal is drawn from an intermediate point. In a power converter including a control unit that controls a converter and outputs a predetermined voltage,
The control unit includes the leg so that the voltage of the capacitor included in the unit power converter becomes the same in the same phase according to the balance in the phase while stopping the current output to the load. A power converter characterized by causing a current to flow through a circulating current route that does not flow through the power.
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| CN106570226B (en) * | 2016-10-19 | 2019-11-15 | 哈尔滨工业大学 | Mean value model and emulation mode in modularization multi-level converter |
| CN106533235B (en) * | 2016-12-26 | 2019-02-01 | 中国西电电气股份有限公司 | A kind of half-bridge MMC inverter and control method containing Redundant Control |
| CN106505844B (en) * | 2016-12-26 | 2019-02-01 | 中国西电电气股份有限公司 | A kind of full-bridge MMC inverter and control method containing Redundant Control |
| CN106787087A (en) * | 2017-01-09 | 2017-05-31 | 许继集团有限公司 | Hybrid MMC sequences pressure charging method, startup method and device |
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