JP7371545B2 - Power conversion device and its control method - Google Patents

Power conversion device and its control method Download PDF

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JP7371545B2
JP7371545B2 JP2020048393A JP2020048393A JP7371545B2 JP 7371545 B2 JP7371545 B2 JP 7371545B2 JP 2020048393 A JP2020048393 A JP 2020048393A JP 2020048393 A JP2020048393 A JP 2020048393A JP 7371545 B2 JP7371545 B2 JP 7371545B2
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JP2021151076A (en
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剛 長野
宏二 丸山
悟 藤田
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Fuji Electric Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Description

本発明は、電力変換装置およびその制御方法に関し、より詳細には、入力された直流電力を三相の商用交流電力に変換して出力する電力変換装置およびその制御方法に関する。 The present invention relates to a power converter and a control method thereof, and more particularly to a power converter that converts input DC power into three-phase commercial AC power and outputs the same, and a control method thereof.

高圧および特別高圧の電力系統に接続される機器は、電力系統の高い電圧（例えば、３．３ｋＶまたは６．６ｋＶ）が半導体スイッチに印加される。高耐圧の半導体スイッチは、コストが高く、損失も大きいことから、低耐圧の半導体スイッチを用いたマルチセル電力変換装置が用いられる場合がある。 In devices connected to high-voltage and extra-high-voltage power systems, the high voltage of the power system (for example, 3.3 kV or 6.6 kV) is applied to semiconductor switches. Since high-voltage semiconductor switches have high costs and large losses, multi-cell power conversion devices using low-voltage semiconductor switches are sometimes used.

マルチセル電力変換装置は、低耐圧の半導体素子を用いた変換回路（例えば，単相２レベルフルブリッジインバータ等）で構成された変換器セルを複数備え、それぞれの変換器セルの出力端子を直列に接続することにより、低耐圧の半導体スイッチなどの部品を用いることができる。従って、単一の変換器セルにより高耐圧の半導体スイッチにより構成した電力変換装置と比較して、製造コストを削減することができる（例えば、特許文献１参照）。 A multi-cell power conversion device is equipped with a plurality of converter cells each made up of a conversion circuit (for example, a single-phase two-level full-bridge inverter) using low-voltage semiconductor elements, and the output terminals of each converter cell are connected in series. By connecting, components such as low voltage semiconductor switches can be used. Therefore, manufacturing costs can be reduced compared to a power conversion device configured with a single converter cell and a high-voltage semiconductor switch (see, for example, Patent Document 1).

マルチセル電力変換装置の適用例として、太陽光発電装置のＰＣＳ（Power Conditioning System）が知られており、変換セルを絶縁ＤＣ／ＤＣコンバータと単相インバータとにより構成し、変圧器を大幅に小型化・軽量化することができる。ＰＣＳは、太陽光発電パネルから出力された直流電力を商用交流電力に変換するだけでなく、電力系統（高圧または特別高圧）と系統連系することができる。系統連系する場合には、瞬時電圧低下が発生しても、運転を継続することが義務付けられている。しかしながら、一相短絡や二相短絡などにより電力系統の電圧が瞬時に不平衡に低下した場合、瞬時電圧低下の期間中、電力変換装置の出力電流によっては逆相電力を流す場合がある。例えば、電力系統が不平衡になっている場合、系統への出力電流が三相平衡のままだと各相の電力が不平衡となるため逆相電力が必要となる。 A known application example of multi-cell power conversion equipment is the PCS (Power Conditioning System) of solar power generation equipment, in which the conversion cell is composed of an isolated DC/DC converter and a single-phase inverter, which significantly reduces the size of the transformer. -Can be made lighter. A PCS not only converts DC power output from a photovoltaic panel into commercial AC power, but also can be interconnected with a power grid (high voltage or extra high voltage). When connected to the grid, it is mandatory to continue operation even if an instantaneous voltage drop occurs. However, when the voltage of the power system drops instantaneously and unbalanced due to a one-phase short circuit or a two-phase short circuit, reverse-sequence power may flow depending on the output current of the power conversion device during the period of the instantaneous voltage drop. For example, if the power system is unbalanced and the output current to the system remains balanced in three phases, the power in each phase will be unbalanced, and therefore, reverse phase power will be required.

特許第６４９６６０８号公報Patent No. 6496608 特許第５５３７２３５号公報Patent No. 5537235

図１に、電力系統の電圧が三相不平衡の状態で電力変換装置から三相平衡電流を流した際の出力電力を示す。一例として、電力系統の電圧が三相不平衡の状態（図１（ａ））で三相平衡の交流電流を出力する（図１（ｄ））場合について説明する。 FIG. 1 shows the output power when a three-phase balanced current flows from a power conversion device in a state where the voltage of the power system is three-phase unbalanced. As an example, a case will be described in which a three-phase balanced alternating current is output (FIG. 1(d)) when the power system voltage is in a three-phase unbalanced state (FIG. 1(a)).

電力系統の電圧の相回転が正方向の電圧成分（図１（ｂ））を、 The voltage component in which the phase rotation of the power system voltage is in the positive direction (Fig. 1(b)) is

Figure 0007371545000001
Figure 0007371545000001

とし、相回転が逆方向の電圧成分（図１（ｃ））を、 The voltage component with the phase rotation in the opposite direction (Fig. 1(c)) is

Figure 0007371545000002
Figure 0007371545000002

とする。前者は対象座標上における正相電圧、後者は逆相電圧である。ここでは対象座標上における零相電圧はないものとする。電力系統に流れる三相平衡の交流電流（図１（ｄ）、正相成分のみ）は、 shall be. The former is a positive sequence voltage on the target coordinates, and the latter is a negative sequence voltage. Here, it is assumed that there is no zero-sequence voltage on the target coordinates. The three-phase balanced alternating current (Figure 1(d), positive phase component only) flowing in the power system is:

Figure 0007371545000003
Figure 0007371545000003

である。 It is.

電力系統に出力される電力の平衡分である正相電力（図１（ｅ））は、正相電圧と正相電流の積であるのに対し、不平衡分である逆相電力（図１（ｆ））は、逆相電圧と正相電流の積（および正相電圧と逆相電流の積）となる。この場合，電力系統に流入する電力は正相電力に加え，逆相電力を含んだ波形となる（図１（ｇ））。 Positive-sequence power (Figure 1(e)), which is the balanced portion of power output to the power grid, is the product of positive-sequence voltage and positive-sequence current, whereas negative-sequence power, which is the unbalanced portion (Figure 1 (e)), is the product of positive-sequence voltage and positive-sequence current. (f)) is the product of the negative sequence voltage and the positive sequence current (and the product of the positive sequence voltage and the negative sequence current). In this case, the power flowing into the power system has a waveform that includes negative-sequence power in addition to positive-sequence power (Fig. 1(g)).

この逆相電力を発生させないために、各相の出力電力が平衡になるように三相電流を不平衡にすると、電圧低下と電圧不平衡率によっては過電流となり、電力系統側の機器に影響を与える可能性がある。そのため，過電流の問題を考慮すると、三相平衡電流を流すことが望ましい。 In order to prevent this negative phase power from being generated, if the three-phase current is made unbalanced so that the output power of each phase is balanced, overcurrent may occur depending on the voltage drop and voltage unbalance rate, affecting equipment on the power system side. It is possible to give Therefore, considering the problem of overcurrent, it is desirable to flow a three-phase balanced current.

図２に、従来のマルチセル電力変換装置を概略の構成を示す。マルチセル電力変換装置１０は、Ｕ，Ｖ，Ｗ相の各々の相ごとに、複数の変換器セルからなるクラスタ１１Ｕ，１１Ｖ，１１Ｗを備えている。各クラスタの入力端子が並列に接続され、太陽光発電装置、蓄電池などの直流電源に接続されている。各クラスタの出力端子は、Ｙ結線（スター結線）方式で電力系統１４に接続されている。各々の変換器セルは、絶縁ＤＣ／ＤＣコンバータである直流－直流変換器１２と、単相インバータである直流－交流変換器１３とが縦続接続されている。各々の変換器セルの入力端子が並列に接続され、出力端子が直列に接続されて、電力系統１４の１つの相に接続されている。 FIG. 2 shows a schematic configuration of a conventional multi-cell power conversion device. The multi-cell power converter device 10 includes clusters 11U, 11V, and 11W each consisting of a plurality of converter cells for each of the U, V, and W phases. The input terminals of each cluster are connected in parallel and connected to a DC power source such as a solar power generation device or a storage battery. The output terminal of each cluster is connected to the power system 14 in a Y-connection (star connection) manner. Each converter cell has a DC-DC converter 12, which is an isolated DC/DC converter, and a DC-AC converter 13, which is a single-phase inverter, connected in cascade. The input terminals of each converter cell are connected in parallel and the output terminals are connected in series and connected to one phase of the power system 14.

マルチセル電力変換装置１０が逆相電力を出力する場合、各クラスタへの入力電力が均等に流入する（例えば、２００ｋＷ）のに対して、各クラスタからの出力電力は不平衡となるため（正相電力と逆相電力の和）、各クラスタの入出力電力の平均値に不一致が生じる。この入出力電力の差分は、各変換器セルのコンデンサに充放電される。入出力電力の差分の平均が０であれば、コンデンサ電圧は、電力脈動によるリプルを含みつつある一定の値となる。しかしながら、入出力電力の差分の平均が０でない場合、すなわち入力電力平均値と出力電力平均値とが一致していない場合には、各クラスタに含まれる変換器セルのコンデンサ電圧が継続的に上昇または低下する。 When the multi-cell power converter 10 outputs negative-phase power, the input power to each cluster flows equally (for example, 200 kW), but the output power from each cluster becomes unbalanced (for example, 200 kW). (the sum of the power and the negative-phase power), a mismatch occurs in the average value of the input and output power of each cluster. This difference in input and output power is charged and discharged into the capacitor of each converter cell. If the average difference between input and output power is 0, the capacitor voltage has a constant value that is beginning to include ripples due to power pulsations. However, if the average difference between input and output power is not 0, that is, if the average input power value and the average output power value do not match, the capacitor voltage of the converter cells included in each cluster will continue to increase. or decrease.

そこで、各クラスタの出力端子をΔ結線（デルタ結線）方式で電力系統に接続し、循環電流により逆相電力を補償することが知られている（例えば、特許文献２参照）。しかしながら、Δ結線方式の場合、電力系統１４の線間電圧（例えばＵＶ相間）が直列接続した変換器セルに印加されるのに対し、Ｙ結線方式では、電力系統１４の相電圧（例えばＵ相）が直列接続した変換器セルに印加される。このため、変換器セルの段数が同じであるとすると、Δ結線方式は、Ｙ結線方式に比べて、印加電圧が３1/2倍となって、適用素子に要求される耐圧が高くなってしまい、装置コストの増加を招くという問題があった。 Therefore, it is known to connect the output terminal of each cluster to the power grid using a delta connection method and compensate for the negative phase power using a circulating current (for example, see Patent Document 2). However, in the case of the Δ connection system, the line voltage (for example, between UV phases) of the power system 14 is applied to the converter cells connected in series, whereas in the case of the Y connection system, the line voltage (for example, between the U phase) of the power system 14 is applied to the converter cells connected in series. ) is applied to the series connected converter cells. Therefore, assuming that the number of stages of converter cells is the same, the applied voltage in the delta connection method is 3 1/2 times that of the Y connection method, and the withstand voltage required for the applicable element is higher. There was a problem in that this resulted in an increase in device cost.

本発明の目的は、Ｙ結線方式で電力系統に接続することができ、逆相電力を補償することができる電力変換装置およびその制御方法を提供することにある。 An object of the present invention is to provide a power conversion device that can be connected to a power system using a Y-connection method and can compensate for negative phase power, and a control method thereof.

本発明は、このような目的を達成するために、一実施態様は、直流電力から三相交流電力または三相交流電力から直流電力のいずれかに変換する電力変換装置であって、 各々の相ごとに少なくとも１つの変換器セルからなるクラスタであって、前記変換器セルの直流側の端子が並列に接続され、前記変換器セルの交流側の端子がスター結線方式で電力系統に接続されるクラスタと、前記電力系統側の逆相電力に合わせて各相の前記クラスタの直流電力を不均等にする相間電力制御部とを備えたことを特徴とする。 In order to achieve such an object, the present invention provides a power conversion device that converts DC power into three-phase AC power or three-phase AC power into DC power, the A cluster consisting of at least one converter cell per unit, wherein the DC side terminals of the converter cells are connected in parallel, and the AC side terminals of the converter cells are connected to the power grid in a star connection system. The present invention is characterized by comprising a cluster, and an interphase power control unit that makes the DC power of the cluster of each phase uneven in accordance with the reverse phase power on the power system side.

本発明によれば、Ｙ結線方式で電力系統に接続し、各クラスタへの直流側の入力電力に不平衡分を加えることにより、各変換器セルのコンデンサ電圧の継続的な上昇もしくは減少を起こさずに、逆相電力を補償することができるので、電力変換装置の信頼性を保ちつつコストを低減することが可能となる。 According to the present invention, by connecting to the power grid using a Y-connection method and adding an unbalanced component to the input power on the DC side to each cluster, a continuous increase or decrease in the capacitor voltage of each converter cell is caused. Since it is possible to compensate for the negative phase power without any noise, it is possible to reduce the cost while maintaining the reliability of the power conversion device.

電力系統の電圧が三相不平衡の状態で電力変換装置から三相平衡電流を流した際の出力電力を示す図である。FIG. 2 is a diagram illustrating output power when a three-phase balanced current is passed from a power conversion device in a state where the voltage of the power system is three-phase unbalanced. 従来のマルチセル電力変換装置を概略の構成を示す図である。1 is a diagram schematically showing the configuration of a conventional multi-cell power conversion device. 本発明の一実施形態にかかるマルチセル電力変換装置を示す図である。FIG. 1 is a diagram showing a multi-cell power converter device according to an embodiment of the present invention. 本実施形態のマルチセル電力変換装置の制御系を示す図である。FIG. 2 is a diagram showing a control system of a multi-cell power conversion device according to the present embodiment. 本実施形態の正相逆相分離部の構成を示す図である。FIG. 3 is a diagram showing the configuration of a normal-phase and reverse-phase separation section of the present embodiment. 第１の実施形態にかかる相間電力制御部の構成を示す図である。FIG. 3 is a diagram showing the configuration of an interphase power control section according to the first embodiment. 第２の実施形態にかかる相間電力制御部の構成を示す図である。FIG. 7 is a diagram showing the configuration of an interphase power control section according to a second embodiment. 第３の実施形態にかかる相間電力制御部の構成を示す図である。FIG. 7 is a diagram showing the configuration of an interphase power control section according to a third embodiment. 第４の実施形態にかかる相間電力制御部の構成を示す図である。It is a figure showing the composition of the interphase power control part concerning a 4th embodiment.

以下、図面を参照しながら本発明の実施形態について詳細に説明する。 Embodiments of the present invention will be described in detail below with reference to the drawings.

（マルチセル電力変換装置）
図３に、本発明の一実施形態にかかるマルチセル電力変換装置を示す。マルチセル電力変換装置２０は、Ｕ，Ｖ，Ｗ相の各々の相ごとに、複数の変換器セルからなるクラスタ２１Ｕ，２１Ｖ，２１Ｗを備えている。各クラスタの直流側の入力端子が並列に接続され、太陽光発電装置、蓄電池などの直流電源に接続されている。各クラスタの交流側の出力端子は、Ｙ結線方式で電力系統２４に接続されている。各々の変換器セルは、絶縁ＤＣ／ＤＣコンバータである直流－直流変換器２２と、単相インバータである直流－交流変換器２３とが縦続接続されている。各々の変換器セルの直流側の入力端子が並列に接続され、交流側の出力端子が直列に接続されて、電力系統２４の１つの相に接続されている。本実施形態では、直流側を入力とし、交流側を出力として説明するが、直流側に蓄電池を接続することもでき、交流側の電力系統から直流側に電力を伝送することもできる。 (Multi-cell power converter)
FIG. 3 shows a multi-cell power conversion device according to an embodiment of the present invention. The multi-cell power converter 20 includes clusters 21U, 21V, and 21W each consisting of a plurality of converter cells for each of the U, V, and W phases. The input terminals on the DC side of each cluster are connected in parallel and connected to a DC power source such as a solar power generation device or a storage battery. The output terminal on the AC side of each cluster is connected to the power system 24 using a Y-connection method. Each converter cell has a DC-DC converter 22, which is an isolated DC/DC converter, and a DC-AC converter 23, which is a single-phase inverter, connected in cascade. The input terminals on the DC side of each converter cell are connected in parallel, and the output terminals on the AC side are connected in series and connected to one phase of the power system 24. In this embodiment, the DC side is used as an input and the AC side is used as an output. However, a storage battery can be connected to the DC side, and power can also be transmitted from the power system on the AC side to the DC side.

直流－直流変換器２２は、直流電力を高周波の交流電力に変換するインバータ回路ＩＮ１と、この交流電力出力を所定の交流電圧に変成する高周波変圧器Ｔと、変成された交流電力を所定の電圧の直流電力に変換するトランジスタで構成されたコンバータ回路ＣＮ１とにより構成されている。この直流電力出力を平滑するためのコンデンサＣ１を介して、直流－交流変換器２３が接続されている。直流－交流変換器２３は、直流電力を交流電力に変換するトランジスタブリッジで構成されたインバータ回路ＩＮ２からなる。 The DC-DC converter 22 includes an inverter circuit IN1 that converts DC power into high-frequency AC power, a high-frequency transformer T that transforms this AC power output into a predetermined AC voltage, and a high-frequency transformer T that converts the transformed AC power into a predetermined voltage. The converter circuit CN1 includes a transistor that converts the power into DC power. A DC-AC converter 23 is connected via a capacitor C1 for smoothing this DC power output. The DC-AC converter 23 includes an inverter circuit IN2 configured with a transistor bridge that converts DC power into AC power.

本実施形態では、各クラスタからの出力電力が不平衡となる（正相電力と逆相電力の和）場合に、交流側の逆相電力に応じて、各クラスタの直流側の入力電力の分配を調整する。入力電力の分配は、クラスタ間のみで調整し、同じクラスタに含まれる変換器セルへの入力電力は均等に分配しておく。 In this embodiment, when the output power from each cluster is unbalanced (sum of positive sequence power and negative sequence power), the input power on the DC side of each cluster is distributed according to the negative sequence power on the AC side. Adjust. The distribution of input power is adjusted only between clusters, and the input power to converter cells included in the same cluster is equally distributed.

ここで、電力系統の正相電圧、逆相電圧、正相電流および逆相電流を下記に示す。 Here, the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current of the power system are shown below.

Figure 0007371545000004
Figure 0007371545000004

この時、各相の正相電力は、 At this time, the positive sequence power of each phase is

Figure 0007371545000005
Figure 0007371545000005

となり、各相の逆相電力は、下記の通りとなる。 Therefore, the negative phase power of each phase is as follows.

Figure 0007371545000006
Figure 0007371545000006

例えば、 for example,

Figure 0007371545000007
Figure 0007371545000007

とすると、各相の正相電力と逆相電力は以下のようになる。 Then, the positive-sequence power and negative-sequence power of each phase are as follows.

Figure 0007371545000008
Figure 0007371545000008

図３に示したように、各クラスタへの直流側の入力電力に不平衡分を加えることにより、各クラスタの入力電力の平均値と出力電力の平均値とが一致して、逆相電力を補償することができる。また、各クラスタの入力電力の平均値と出力電力の平均値とが一致しているので、各クラスタに含まれる変換器セルのコンデンサ電圧が一定に保たれる。 As shown in Figure 3, by adding an unbalanced component to the DC side input power to each cluster, the average value of the input power and the average value of the output power of each cluster match, and the negative phase power is can be compensated. Furthermore, since the average value of input power and the average value of output power of each cluster match, the capacitor voltage of the converter cells included in each cluster is kept constant.

図４に、本実施形態のマルチセル電力変換装置の制御系を示す。各クラスタの入力電力の分配を調整するために、マルチセル電力変換装置２０は、相間電力制御部３１と正相逆相分離部３２とを備えている。正相逆相分離部３２は、系統電圧と系統電流の測定結果から、式（１）に示した正相電圧、逆相電圧、正相電流、逆相電流を分離する。相間電力制御部３１は、正相逆相分離部３２の出力から各クラスタの逆相電力（式（３））を求め、逆相電力と直流バス電圧とから各クラスタの電流補正値を算出する。制御部３３からの電流指令は、各クラスタに均等に送出されるが、これに相間電力制御部３１からの電流補正値を加えて、各クラスタへの入力電力を調整する。 FIG. 4 shows a control system of the multi-cell power conversion device of this embodiment. In order to adjust the distribution of input power to each cluster, the multi-cell power conversion device 20 includes an interphase power control section 31 and a positive phase/negative phase separation section 32. The normal phase/negative phase separation unit 32 separates the positive sequence voltage, negative sequence voltage, positive sequence current, and negative sequence current shown in equation (1) from the measurement results of the system voltage and system current. The interphase power control unit 31 calculates the negative phase power (formula (3)) of each cluster from the output of the positive phase and negative phase separation unit 32, and calculates the current correction value of each cluster from the negative phase power and the DC bus voltage. . The current command from the control unit 33 is sent out equally to each cluster, and the current correction value from the interphase power control unit 31 is added to this to adjust the input power to each cluster.

図５に、本実施形態の正相逆相分離部の構成を示す。測定された系統電圧と系統電流のそれぞれを、ａｂｃ相からｄｑ軸変換を行い、正相分と逆相分に分離して、正相電圧、逆相電圧、正相電流および逆相電流を算出する。 FIG. 5 shows the configuration of the normal-phase and reverse-phase separation section of this embodiment. Each of the measured grid voltage and grid current is converted from the abc phase to the dq axis, separated into positive and negative phase components, and the positive sequence voltage, negative sequence voltage, positive sequence current, and negative sequence current are calculated. do.

（第１の実施形態）
図６に、第１の実施形態にかかる相間電力制御部の構成を示す。相間電力制御部３１は、正相逆相分離部３２の出力である正相電流と逆相電圧とを乗算し、逆相電流と正相電圧とを乗算し、２つの乗算結果を合算して、Ｕ，Ｖ，Ｗ相の各々の相ごとに、式（３）の逆相電力ＰUN，ＰVN，ＰWNを算出する。この逆相電力を直流側の端子間電圧である直流バス電圧の測定結果により除算して、各クラスタ２１Ｕ，２１Ｖ，２１Ｗに与える電流指令の電流補正値を算出する。電流補正値は、図３に示した入力電力に加えられる不平衡分に相当する。 (First embodiment)
FIG. 6 shows the configuration of the interphase power control section according to the first embodiment. The phase-to-phase power control unit 31 multiplies the positive-sequence current and the negative-sequence voltage, which are the outputs of the positive-phase and negative-phase separation unit 32, multiplies the negative-sequence current and the positive-sequence voltage, and adds up the two multiplication results. , U, V, and W phases, the negative phase powers P UN , P VN , and P WN of Equation (3) are calculated. This negative phase power is divided by the measurement result of the DC bus voltage, which is the voltage between terminals on the DC side, to calculate the current correction value of the current command given to each cluster 21U, 21V, 21W. The current correction value corresponds to the unbalanced amount added to the input power shown in FIG.

マルチセル電力変換装置の制御部３３からの電流指令は、各クラスタに均等に配分される。この各クラスタに与えられる電流指令に、それぞれ電流補正値を加えることにより、各クラスタの入力電力に、逆相電力に応じた不平衡分を加える。 A current command from the control unit 33 of the multi-cell power conversion device is equally distributed to each cluster. By adding current correction values to the current commands given to each cluster, an unbalanced amount corresponding to the negative phase power is added to the input power of each cluster.

（第２の実施形態）
図７に、第２の実施形態にかかる相間電力制御部の構成を示す。式（１）中の逆相電力には、いずれも振動成分（３０ｋＷ×ｃｏｓ２ωｔ）を含んでいるので、振動成分除去部３４において、下式 (Second embodiment)
FIG. 7 shows the configuration of the interphase power control section according to the second embodiment. Since the negative phase power in equation (1) both includes a vibration component (30kW×cos2ωt), the vibration component removal unit 34 calculates the following equation.

Figure 0007371545000009
Figure 0007371545000009

により求めた振動成分を、各クラスタに加える電流補正値から差し引くこともできる。 The vibration component determined by can also be subtracted from the current correction value added to each cluster.

（第３の実施形態）
図８に、第３の実施形態にかかる相間電力制御部の構成を示す。第１および第２の実施形態では、直流－直流変換器２２に対する電流指令に補正値を加えて、入力電力に不平衡分を加えることにより、逆相電力を補償した。第３の実施形態では、直流－交流変換器２３に対するフィードバック制御において、各クラスタ２１Ｕ，２１Ｖ，２１Ｗに与える電圧指令に対して補正値を加える。 (Third embodiment)
FIG. 8 shows the configuration of the interphase power control section according to the third embodiment. In the first and second embodiments, a correction value is added to the current command for the DC-DC converter 22, and an unbalanced component is added to the input power to compensate for the negative phase power. In the third embodiment, in feedback control for the DC-AC converter 23, a correction value is added to the voltage command given to each cluster 21U, 21V, 21W.

制御部４１は、直流－交流変換器２３の各変換器セルの平滑コンデンサＣ１の端子間電圧を測定し、全セルのコンデンサ電圧の平均値に基づいて電圧指令を算出する。電圧指令は、各クラスタに均等に配分され、この電圧指令に、それぞれ電流補正値を加えることにより、各クラスタの入力電力を調整する。なお、各クラスタ（各相）のコンデンサ電圧の平均値、すなわち相平均値に基づいて相電圧指令を算出し、段間バランス制御を行い、各クラスタへのセル電圧指令を算出することもできる。このとき、クラスタごとのセル電圧指令のそれぞれに、上記の電流補正値を加える。 The control unit 41 measures the voltage between the terminals of the smoothing capacitor C1 of each converter cell of the DC-AC converter 23, and calculates a voltage command based on the average value of the capacitor voltages of all cells. The voltage command is equally distributed to each cluster, and the input power of each cluster is adjusted by adding a current correction value to the voltage command. Note that it is also possible to calculate the phase voltage command based on the average value of the capacitor voltage of each cluster (each phase), that is, the phase average value, perform interstage balance control, and calculate the cell voltage command to each cluster. At this time, the above current correction value is added to each cell voltage command for each cluster.

また、第３の実施形態では、相間バランス制御部４２において、相平均値を全セル平均値に近づける相間バランス制御を行う。相間バランス制御は、各クラスタ、各変換器セルにおける容量のばらつき、検出誤差、スイッチングに伴うコンデンサ電圧の変動を補正するための制御である。 Further, in the third embodiment, the inter-phase balance control unit 42 performs inter-phase balance control to bring the phase average value closer to the all-cell average value. Interphase balance control is control for correcting variations in capacitance in each cluster and each converter cell, detection errors, and fluctuations in capacitor voltage due to switching.

一方、相間電力制御部３１による制御は、フィードフォワード制御であり、直流－交流変換器２３が出力しようとする逆相電力に合わせて、直流－直流変換器２２から逆相電力分相当の電力を供給させる。クラスタごとに見れば、直流－直流変換器２２から供給される平均電力と直流－交流変換器２３から供給される平均電力とが一致し、コンデンサ電圧は一定になるので、相間電力制御と相間バランス制御とは別個に制御することができる。 On the other hand, the control by the phase-to-phase power control unit 31 is feedforward control, in which power equivalent to the negative-sequence power is output from the DC-DC converter 22 in accordance with the negative-sequence power that the DC-AC converter 23 attempts to output. Let it be supplied. Looking at each cluster, the average power supplied from the DC-DC converter 22 and the average power supplied from the DC-AC converter 23 match, and the capacitor voltage becomes constant, so interphase power control and interphase balance are achieved. It can be controlled separately from the control.

（第４の実施形態）
図９に、第４の実施形態にかかる相間電力制御部の構成を示す。第３の実施形態では、制御部４１は、直流－交流変換器２３の各変換器セルの平滑コンデンサＣ１の端子間電圧を測定し、フィードバック制御を行って、各クラスタへのセル電圧指令を送出し、相間バランス制御部４２において、相平均値を全セル平均値に近づける相間バランス制御を行っていた。 (Fourth embodiment)
FIG. 9 shows the configuration of the interphase power control section according to the fourth embodiment. In the third embodiment, the control unit 41 measures the voltage across the terminals of the smoothing capacitor C1 of each converter cell of the DC-AC converter 23, performs feedback control, and sends a cell voltage command to each cluster. However, the interphase balance control section 42 performs interphase balance control to bring the phase average value closer to the all cell average value.

第４の実施形態では、この相間バランス制御を用いて、各クラスタの入力電力に、逆相電力に応じた不平衡分を加える。すなわち、逆相電力に伴う平滑コンデンサＣ１の変動を抑えるように、各クラスタに与えられる電流指令に、それぞれ電流補正値を加える。相間バランス制御部５１では、平滑コンデンサＣ１の端子間電圧の相平均値と全セル平均値から電流補正値を算出することにより、直流－交流変換器２３から供給される平均電力に対し直流－直流変換器２２から供給される平均電力を一致させる。これにより、各変換器セルのコンデンサ電圧の継続的な上昇もしくは減少を起こさずに、逆相電力を補償することができる。 In the fourth embodiment, this interphase balance control is used to add an unbalanced amount corresponding to the negative phase power to the input power of each cluster. That is, a current correction value is added to each current command given to each cluster so as to suppress fluctuations in the smoothing capacitor C1 due to negative phase power. The phase-to-phase balance control unit 51 calculates a current correction value from the phase average value and all-cell average value of the voltage between the terminals of the smoothing capacitor C1, thereby adjusting the DC-DC current for the average power supplied from the DC-AC converter 23. The average power supplied by the converters 22 is matched. This makes it possible to compensate for negative sequence power without continuously increasing or decreasing the capacitor voltage of each converter cell.

相間バランス制御部５１は、逆相電力に伴うコンデンサ電圧変動から、間接的に各相に分配する電力を求めていることになるから、相間電力制御部３１による制御を兼ねることができる。ただし、ＰＩ制御によるため、系統電圧の瞬時的な電圧低下など外乱の瞬間的な変化に追従できない可能性があるが、定常的な変動には対応することができる。 Since the phase-to-phase balance control section 51 indirectly determines the power to be distributed to each phase from the capacitor voltage fluctuation due to the negative phase power, it can also serve as the control by the phase-to-phase power control section 31. However, since it is based on PI control, it may not be able to follow instantaneous changes in disturbances such as instantaneous voltage drops in the grid voltage, but it can respond to steady fluctuations.

本実施形態によれば、Ｕ，Ｖ，Ｗ相の各々の相ごとに、少なくとも１の変換器セルからなるクラスタを備え、変換器セルの直流側の端子が並列に接続された電力変換装置において、変換器セルの交流側の端子をＹ結線方式で電力系統に接続することができ、平滑コンデンサの端子間電圧を維持しつつ逆相電力を出力できるため、電力変換装置の信頼性を保ちつつコストを低減することができる。 According to the present embodiment, in a power converter device including a cluster consisting of at least one converter cell for each of the U, V, and W phases, the DC side terminals of the converter cells are connected in parallel. , the AC side terminals of the converter cell can be connected to the power grid using a Y-connection method, and negative-phase power can be output while maintaining the voltage between the terminals of the smoothing capacitor, thereby maintaining the reliability of the power converter. Cost can be reduced.

（他の実施形態）
第１～第３の実施形態では、直流－直流変換器２２として、ＤＡＢ（Dual Active Bridge）コンバータを例にして説明したが、ＬＬＣコンバータを適用してもよい。 (Other embodiments)
In the first to third embodiments, a DAB (Dual Active Bridge) converter is used as an example of the DC-DC converter 22, but an LLC converter may also be applied.

本実施形態では、ＰＣＳに適用されるような、入力された直流電力を交流電力に変換して出力する電力変換装置について説明した。双方向に電力変換できることは明らかであるから、例えば、高圧の系統交流電源（６６００Ｖ）から、通信機器室内の通信機器に供給する直流電力（－４８Ｖ）を供給する電力変換装置に適用することができる。 In this embodiment, a power conversion device that converts input DC power into AC power and outputs the AC power, which is applied to a PCS, has been described. Since it is clear that power can be converted in both directions, it can be applied, for example, to a power conversion device that supplies DC power (-48V) from a high-voltage grid AC power supply (6600V) to communication equipment in a communication equipment room. can.

１０，２０ マルチセル電力変換装置
１１Ｕ，１１Ｖ，１１Ｗ，２１Ｕ，２１Ｖ，２１Ｗ クラスタ
１２，２２ 直流－直流変換器
１３，２３ 直流－交流変換器
１４，２４ 電力系統
３１ 相間電力制御部
３２ 正相逆相分離部
３３，４１ 制御部
３４ 振動成分除去部
４２，５１ 相間バランス制御部
ＣＮ１，ＣＮ２ コンバータ回路
ＩＮ１，ＩＮ２ インバータ回路
Ｃ１，Ｃ２，Ｃ３ コンデンサＣａ
Ｔ 高周波変圧器 10, 20 Multi-cell power converter 11U, 11V, 11W, 21U, 21V, 21W Cluster 12, 22 DC-DC converter 13, 23 DC-AC converter 14, 24 Power system 31 Inter-phase power control section 32 Positive phase and negative phase Separation section 33, 41 Control section 34 Vibration component removal section 42, 51 Interphase balance control section CN1, CN2 Converter circuit IN1, IN2 Inverter circuit C1, C2, C3 Capacitor Ca
T High frequency transformer

Claims (7)

直流電力から三相交流電力または三相交流電力から直流電力のいずれかに変換する電力変換装置であって、
各々の相ごとに少なくとも１つの変換器セルからなるクラスタであって、前記変換器セルの直流側の端子が並列に接続され、前記変換器セルの交流側の端子がスター結線方式で電力系統に接続されるクラスタと、
前記電力系統側の逆相電力に合わせて各相の前記クラスタの直流電力を不均等にする相間電力制御部と
を備えたことを特徴とする電力変換装置。 A power conversion device that converts DC power to three-phase AC power or three-phase AC power to DC power,
A cluster consisting of at least one converter cell for each phase, wherein the DC side terminals of the converter cells are connected in parallel, and the AC side terminals of the converter cells are connected to the power grid in a star connection manner. Connected clusters and
A power conversion device comprising: an interphase power control unit that makes DC power of the clusters of each phase unequal in accordance with reverse phase power on the power system side. 前記電力系統の系統電圧と系統電流を測定し、正相電圧、逆相電圧、正相電流および逆相電流を算出する正相逆相分離部を備え、
前記相間電力制御部は、前記正相電圧、前記逆相電圧、前記正相電流および前記逆相電流から前記逆相電力を算出し、直流側の端子間電圧で除算して電流補正値を算出して、各相の前記クラスタへの電流指令に加えることを特徴とする請求項１に記載の電力変換装置。 comprising a positive and negative phase separation unit that measures a system voltage and a system current of the power system and calculates a positive sequence voltage, a negative sequence voltage, a positive sequence current, and a negative sequence current;
The phase-to-phase power control unit calculates the negative-sequence power from the positive-sequence voltage, the negative-sequence voltage, the positive-sequence current, and the negative-sequence current, and calculates a current correction value by dividing the negative-sequence power by a DC side terminal-to-terminal voltage. 2. The power conversion device according to claim 1, wherein the power conversion device adds the current command to the cluster of each phase. 前記逆相電力の振動成分を、前記電流補正値から減算する振動成分除去部をさらに備えたことを特徴とする請求項２に記載の電力変換装置。 The power conversion device according to claim 2, further comprising an oscillation component removal unit that subtracts an oscillation component of the negative phase power from the current correction value. 前記変換器セルの直流電圧を測定する手段と、
前記クラスタ内の前記変換器セルの直流電圧の相平均値を、全ての前記変換器セルの直流電圧の全セル平均値に近づける制御を行う相間バランス制御部と
をさらに備えたことを特徴とする請求項１に記載の電力変換装置。 means for measuring the DC voltage of the converter cell;
The method further comprises: an interphase balance control unit that performs control to bring the phase average value of the DC voltage of the converter cells in the cluster closer to the all-cell average value of the DC voltages of all the converter cells. The power conversion device according to claim 1. 前記変換器セルの直流電圧を測定する手段を備え、
前記相間電力制御部は、測定された直流電圧から電流補正値を算出して、各相の前記クラスタへの電流指令に加えることを特徴とする請求項１に記載の電力変換装置。 comprising means for measuring the DC voltage of the converter cell,
The power conversion device according to claim 1, wherein the interphase power control unit calculates a current correction value from the measured DC voltage and adds it to the current command to the cluster of each phase. 直流電力から三相交流電力または三相交流電力から直流電力のいずれかに変換する電力変換装置であって、各々の相ごとに少なくとも１つの変換器セルを含み、前記変換器セルの直流側の端子が並列に接続され、前記変換器セルの交流側の端子がスター結線方式で電力系統に接続されたクラスタを含む電力変換装置の制御方法において、
前記電力系統の系統電圧と系統電流を測定し、逆相電力を算出するステップと、
前記逆相電力に合わせて各相の前記クラスタの直流電力の不均等分に相当する電流補正値を算出するステップと、
各相の前記クラスタへの電流指令に前記電流補正値を加えるステップと
を備えたことを特徴とする電力変換装置の制御方法。 A power converter for converting either DC power into three-phase AC power or from three-phase AC power into DC power, the power conversion device comprising at least one converter cell for each phase, wherein the DC side of the converter cell is A method for controlling a power converter including a cluster in which terminals are connected in parallel and the AC side terminals of the converter cells are connected to a power system in a star connection method,
Measuring the grid voltage and grid current of the power grid and calculating negative sequence power;
calculating a current correction value corresponding to the unequal portion of the DC power of the clusters of each phase according to the negative phase power;
A method for controlling a power conversion device, comprising: adding the current correction value to a current command to the cluster of each phase. 前記逆相電力の振動成分を、前記電流補正値から減算する振動成分除去ステップをさらに備えたことを特徴とする請求項６に記載の電力変換装置の制御方法。 7. The method of controlling a power conversion device according to claim 6, further comprising a vibration component removing step of subtracting the vibration component of the negative phase power from the current correction value.
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JP2000116148A (en) 1998-02-13 2000-04-21 Mitsubishi Electric Corp Power conversion apparatus
US20130057236A1 (en) 2011-09-06 2013-03-07 Che-Wei Hsu Low voltage ride-through control method for grid-connected converter of distributed energy resources
WO2015105081A1 (en) 2014-01-09 2015-07-16 住友電気工業株式会社 Power conversion device and three-phase alternating current power supply device
WO2018211624A1 (en) 2017-05-17 2018-11-22 三菱電機株式会社 Power conversion device

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JP2000116148A (en) 1998-02-13 2000-04-21 Mitsubishi Electric Corp Power conversion apparatus
US20130057236A1 (en) 2011-09-06 2013-03-07 Che-Wei Hsu Low voltage ride-through control method for grid-connected converter of distributed energy resources
WO2015105081A1 (en) 2014-01-09 2015-07-16 住友電気工業株式会社 Power conversion device and three-phase alternating current power supply device
WO2018211624A1 (en) 2017-05-17 2018-11-22 三菱電機株式会社 Power conversion device

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