DC/AC system interconnection device and AC/AC system interconnection device

• US 10,177,572 B2
• Filed: 03/25/2016
• Issued: 01/08/2019
• Est. Priority Date: 03/31/2015
• Status: Active Grant

• Current Assignee: Fujitsu General Company Limited (Fujifilm Holdings Corporation)
• Original Assignee: Fujitsu General Company Limited (Fujifilm Holdings Corporation)
• Inventors: Ichiki, Satoshi
• Primary Examiner(s): Gblende, Jeffrey
• Assistant Examiner(s): Singh, David A.
• Application Number:
  US15/561,959
• Publication Number:
  US 20180115162A1
• Time in Patent Office: 1,019 Days
• CPC Class Codes: H02J 3/06 Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: H02M 5/2932 with automatic control of output voltage, current or power
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/797 using semiconductor devices only
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

A device includes a bidirectional switch circuit 10, a control unit 20 that performs virtual AC/DC conversion processing to acquire a plurality of interline voltage generation sections according to a plurality of modes divided according to a magnitude relation between voltages in each phase and that generates a switching pattern of the bidirectional switch circuit 10 to perform virtual DC/DC conversion processing corresponding to the plurality of interline voltage generation sections based on a second carrier waveform pattern CW2 according to the plurality of modes and a signal level G1 of a P-phase, a current setting unit 50 that inputs a current direction and an amount of current that flows in a power line LU, a current detection unit 51 that detects the current direction and the amount of current of the power line LU, and a current adjustment unit 52 that increases and decreases the signal level G1.

Claims

1. A DC/AC system interconnection device that is able to bidirectionally and directly perform power conversion between three-phase AC power and DC power, the device comprising:

a bidirectional switch circuit that is provided between a three-phase AC power supply and a DC power supply and turns on and off power between the three-phase AC power supply and the DC power supply;

a control unit that generates, in a predetermined switching cycle, a first carrier waveform pattern, which has a pattern that varies for each mode, according to a plurality of modes divided according to a magnitude relation between voltages in each phase in the three-phase AC power, that performs virtual AC/DC conversion processing to acquire a plurality of interline voltage generation sections, in which two phases of the three-phase AC power are selected, based on the first carrier waveform pattern in the predetermined switching cycle and a first control signal corresponding to a phase of the three-phase AC power, that generates a second carrier waveform pattern, which varies according the plurality of modes, corresponding to the plurality of interline voltage generation sections acquired from the virtual AC/DC conversion processing, and that generates a switching pattern of the bidirectional switch circuit to perform virtual DC/DC conversion processing, which varies according to the plurality of modes, on an interline voltage across two phases selected from the plurality of interline voltage generation sections based on the generated second carrier waveform pattern and a second control signal corresponding to a phase of the DC power;

a current setting unit that inputs a current set value indicating a current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit;

a current detection unit that detects the current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit; and

a current adjustment unit that generates the second control signal which increases and decreases a signal level such that the current direction and the amount of current detected by the current detection unit become the current set value.

2. The DC/AC system interconnection device according to claim 1, wherein the current adjustment unit makes an average DC voltage in the predetermined switching cycle generated from the virtual DC/DC conversion processing by the control unit larger than an interphase voltage of the DC power and generates the second control signal to adjust the amount of current based on a magnitude of a differential voltage between the interphase voltage of the DC power and the average DC voltage in a case where the three-phase AC power is converted to the DC power, and makes the average DC voltage smaller than the interphase voltage of the DC power and generates the second control signal to adjust the amount of current based on the magnitude of the differential voltage between the interphase voltage of the DC power and the average DC voltage in a case where the DC power is converted to the three-phase AC power.

3. The DC/AC system interconnection device according to claim 1, further comprising:

an inverting unit that sets the second control signal to a positive second control signal and generates a negative second control signal obtained by inverting the positive second control signal, wherein a magnitude of the average DC voltage corresponds to a difference between a signal level of the positive second control signal and a signal level of the negative second control signal.

4. The DC/AC system interconnection device according to claim 1, wherein the control unit recognizes a maximum voltage phase, a minimum voltage phase, and an intermediate voltage phase in the three-phase AC power and acquires the plurality of interline voltage generation sections by being divided into a first section corresponding to the intermediate voltage phase and the minimum voltage phase, a second section corresponding to the maximum voltage phase and the minimum voltage phase, and a third section corresponding to the maximum voltage phase and the intermediate voltage phase.

5. The DC/AC system interconnection device according to claim 1, wherein the second carrier waveform pattern has a pattern of which a level changes in a chevron that straddles two consecutive sections out of the plurality of interline voltage generation sections.

6. The DC/AC system interconnection device according to claim 1, wherein when a voltage phase with a larger voltage value is set as a +side phase and a voltage phase with a smaller voltage value is set as a −

side phase, out of two voltage phases in each of the plurality of interline voltage generation sections, the second carrier waveform pattern has a pattern of which a level is continuous in a chevron that straddles two interline voltage generation sections to be switched in a case where there is a phase common to +side phases or −

side phases when switching between the interline voltage generation sections, and has a pattern of which a level changes in a serrated shape at a boundary between two interline voltage generation sections to be switched in a case where there is a phase, which is inverted between a +side phase and a −

side phase, when switching between the interline voltage generation sections.