Mitsubishi Electric Corporation

Toshiba Mitsubishi-electric Industrial Systems Corporation

Akito Nakayama

Takuya Kajiyama

Miwako Tanaka

Takushi Jimichi

Taichiro Tsuchiya

Yuki Ishii

Jumpei Isozaki

Toshiyuki Fujii

A power converter includes at least one arm for each phase, and each arm is formed by connecting, in series, a plurality of converter cells each having a plurality of semiconductor switching elements and a DC capacitor. A control device generates, for each arm, an arm voltage command for the plurality of convener cells, to control the power converter. The control device includes a voltage information calculation unit for calculating a voltage information value on the basis of voltage of at least one DC capacitor in the power converter, and a overall voltage control unit for changing a voltage total value of all the DC capacitors so that the voltage information value becomes close to a set lower limit value.

Power conversion device

Unit converters each comprises a capacitor, a switching element having a flat surface on one side, a P-pole connection conductor where a second terminal hole at one end for fixing an electrode corresponding to a P-pole of the switching element and a first terminal hole at the other end for fixing a terminal of the capacitor are formed, and an N-pole connection conductor where a second terminal hole at one end for fixing an electrode corresponding to a N-pole of the switching element and a first terminal hole at the other end for fixing a terminal of the capacitor are formed. The unit-converters each including the connection conductors arranged to overlap in the thickness direction with their insulation maintained make the cooling surfaces of the switching elements be opposed to each other with a cooling device therebetween.

A controlling circuitry of a power conversion device has a first control mode for controlling circulation current circulating among leg circuits for the respective phases in a power converter so that an AC component having a frequency that is an even multiple other than a multiple of 3 with respect to the frequency of a fundamental component of AC is contained in the circulation current, and determines whether to make the first control mode active or inactive, on the basis of the voltage value of an energy storage element.

A first voltage control circuitry controls a first representative value, i.e., an average-value corresponding value of DC capacitor voltages of all converter cells to follow an overall voltage command value. A phase balance control circuitry controls second representative values, i.e., average-value corresponding values of DC capacitor voltages of the converter cells in leg circuits for respective phases to follow the first representative value. A positive-negative balance control circuitry controls deviations of third representative values, i.e., average-value corresponding values of the DC capacitor voltages of the converter cells in the positive and negative arms of the leg circuits for respective phases to become zero between the positive and negative arms. An individual balance control circuitry controls DC capacitor voltages of all the converter cells to follow the third representative values.

A power conversion device includes: a power converter including, for respective phases of AC, leg circuits each including a pair of arms connected in series, the arms including a plurality of converter cells which are connected in series and each of which has an energy storage element and a plurality of semiconductor elements, the leg circuits being connected in parallel between positive and negative DC terminals, the power converter being configured to perform power conversion between multiphase AC and DC; and a control unit. The control unit corrects an AC voltage command value for controlling AC voltage of the power converter, by a zero-phase-sequence voltage command value having a set amplitude and a set phase, and performs adjustment control for adjusting at least either the amplitude or the phase of the zero-phase-sequence voltage command value on the basis of electric energy variation in the arm.

Power conversion device having converter cells connected in series in a multiplexed manner and each including an energy storage element

A power converter to be tested is supplied with arm current from a hysteresis converter in a state in which it is connected to an auxiliary converter through a line. In the power converter and the auxiliary converter, a circulation operation is performed in which a current path bypassing power storage elements is formed between an output terminal of the power converter and an output terminal of the auxiliary converter, after the start of output of arm current in accordance with a reference current command value in which an AC component and a DC component are superimposed, until a DC component of arm current reaches a predetermined level. After execution of the circulation operation, in the power converter and the auxiliary converter, voltage control of the power storage elements and the output terminals is started.

Testing device and testing method for power converters

A power converter includes two arms for each phase between DC terminals, and each arm is formed by connecting a plurality of converter cells in series. A control device includes an arm voltage command generation unit which generates, for each arm, an arm voltage command for the plurality of converter cells. The arm voltage command is generated by superimposing a zero-phase-sequence voltage command having a frequency component that is three times an AC fundamental frequency. Phase adjustment of the zero-phase-sequence voltage command is performed on the basis of voltage of a DC capacitor in the converter cell and the arm voltage command.

A power conversion device includes, for respective phases of an AC circuit, leg circuits each having a pair of arms connected in series to each other, each arm including a plurality of converter cells which are connected in series and each of which has an energy storage element. A controlling circuitry includes a zero-phase-sequence voltage command value adjustment unit for correcting arm voltage command values for the arms by a zero-phase-sequence voltage command value. The command value correction circuitry performs adjustment control for adjusting the zero-phase-sequence voltage command value so that at least one arm voltage command value becomes equivalent to a limit value of the output voltage range of the arm.

A main circuit power supply device includes: a plurality of voltage-division power storage elements connected in series; voltage adjustment circuits for adjusting each of voltages of the plurality of voltage-division power storage elements through mutual transfer of power between the plurality of voltage-division power storage elements; and at least one DC/DC converter which is connected to at least one of the voltage-division power storage elements and supplies a control power source to a main circuit control circuitry to control a main circuit.

A master converter and a plurality of slave converters each have an input connected to an associated one of a plurality of power storage elements, respectively, and an output connected to an output terminal in parallel. The master converter converts the voltage of the associated capacitor based on a duty ratio for matching an output voltage to a voltage command value, outputs the converted voltage to the output terminal, and transmits a control signal indicative of the duty ratio to the plurality of slave converters via a signal insulation unit. Each of the plurality of slave converters converts the voltage of the associated capacitor in response to the control signal transmitted via the signal insulation unit and outputs the converted voltage to the output terminal. A correction means is configured to correct at least the duty ratio in the master converter such that the duty ratio in the master converter matches the duty ratio in each of the plurality of slave converters.

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Tokyo, Japan

Akito Nakayama