POWER CONVERSION DEVICE AND TEST METHOD FOR SAME
FIG1 is a circuit block diagram showing a configuration of a power conversion device according to an embodiment of the present invention
FIG1 is a circuit block diagram showing a configuration of a power conversion device according to an embodiment of the present invention. In FIG1, this power conversion device is used as a reactive power compensator that compensates for reactive power of a power system 1 and includes switches S1 to S6, transformers 2 and 3, current-limiting resistors R1 to R3, AC lines UL, VL, and WL, current transformers C1 to C3, reactors L1 to L3, arms Al to A3, and a control device 4. Each of arms A1 to A3 includes a plurality of cascaded unit converters 5. Returning to FIG1, control device 4 controls each of three arms A1 to A3 (that is, each of a plurality of unit converters 5), based on external test signal TE, activation signal EN, and reactive power reference Qr, AC voltages Vu, Vv, and Vw from transformer 3, and AC currents Iuv, Ivw, and Iwu from current detectors C1 to C3. As shown in FIG1, it is assumed that each of switches S1 to S3 has one terminal connected to the corresponding one of three phase transmission lines 1u, 1v, 1w of power system 1. In this state, if normal operation of arms A1 to A3 is started immediately after switches S1 to S3 and switches S4 to S6 are successively turn on to charge capacitor 15 of each unit converter 5, power system 1 is adversely affected in the case of a fault of the power conversion device.
circuit block diagram
7
wave signal ϕ22 is same pulse width
5
unit converters unit converter
4
control device
10
inverter inverters
['1. A power conversion device comprising: three arms that are delta-connected; each of the three arms including a capacitor configured to store DC power, and an inverter configured to convert DC power into AC power; a first controller configured to control the inverter of each of the three arms such that circulating current of the three arms follows a first reference in a test period in which a power system is cut off from the three arms; and a second controller configured to control the inverter of each of the three arms such that electric power transferred between the power system and the three arms follows a second reference in normal operation in which there is electrical continuity between the power system and the three arms, wherein it is determined whether the power conversion device is normal, based on the circulating current in the test period.', '8. The power conversion device according to claim 1, wherein each of the three arms includes a plurality of unit converters, each of the unit converters includes the capacitor and the inverter, and a plurality of the inverters are cascaded.']