Power conversion system and control device for same

Patent metadata

Field	Value
Publication number	US-12381397-B2
Application number	US-202018251194-A
Country	US
Kind code	B2
Filing date	Nov 11, 2020
Priority date	Nov 11, 2020
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

In a power conversion system, a first power converter is connected between a first AC power system, and a first DC main line and a DC return line. A second power converter is connected between the first AC power system, and the DC return line and a second DC main line. A first control device controls the first power converter in accordance with a first active power command value. A second control device controls the second power converter in accordance with a second active power command value. A common control device sets the first active power command value and the second active power command value by distributing a command value of total active power output from the entire power conversion system to the first AC power system. The common control device makes the first active power command value and the second active power command value different from each other.

First claim

The invention claimed is:

1. A power conversion system comprising:
a first power converter connected between
a first AC power system, and
a first DC main line and a DC return line;

a second power converter connected between
the first AC power system, and
the DC return line and a second DC main line;

a third power converter connected between
a second AC power system, and
the first DC main line and the DC return line; and

a fourth power converter connected between
the second AC power system, and
the DC return line and the second DC main line;

a first control device to control the first power converter in accordance with a first active power command value;
a second control device to control the second power converter in accordance with a second active power command value; and
a common control device to set the first active power command value and the second active power command value by distributing a command value of total active power output from the entire power conversion system to the first AC power system, wherein
the common control device makes the first active power command value and the second active power command value different from each other, and
the common control device distributes the total active power command value to the first active power command value and the second active power command value such that a sum of losses at the first power converter, the second power converter, the third power converter, the fourth power converter, the first DC main line, the DC return line, and the second DC main line is minimized.

2. The power conversion system according to claim 1 , wherein the common control device sets the first active power command value to be larger than the second active power command value when a loss of the first power converter is smaller than a loss of the second power converter and a loss of the third power converter is smaller than a loss of the fourth power converter.

3. The power conversion system according to claim 1 , wherein
each of the first power converter and the second power converter is a modular multilevel converter including a plurality of cascade-connected converter cells,
each of the plurality of converter cells included in the first power converter includes a plurality of switching elements that are pulse-width controlled according to a first carrier frequency,
each of the plurality of converter cells included in the second power converter includes a plurality of switching elements that are pulse-width controlled according to a second carrier frequency, and
the common control device sets the second carrier frequency to be lower than the first carrier frequency.

4. A power conversion system comprising:
a first power converter connected between
a first AC power system, and
a first DC main line and a DC return line;

a second power converter connected between
the first AC power system, and
the DC return line and a second DC main line;

a first control device to control the first power converter in accordance with a first active power command value;
a second control device to control the second power converter in accordance with a second active power command value; and
a common control device to set the first active power command value and the second active power command value by distributing a command value of total active power output from the entire power conversion system to the first AC power system, wherein
the common control device makes the first active power command value and the second active power command value different from each other,
each of the first power converter and the second power converter is a modular multilevel converter, and
when the total active power command value is set to zero, the common control device sets magnitude of the first active power command value to be equal to magnitude of the second active power command value, and sets a sign of the first active power command value to be opposite to a sign of the second active power command value.

5. A power conversion system comprising:
a first power converter connected between
a first AC power system, and
a first DC main line and a DC return line; and

a second power converter connected between
the first AC power system, and
the DC return line and a second DC main line, wherein

each of the first power converter and the second power converter is a modular multilevel converter including a plurality of cascade-connected converter cells, and
each of the plurality of converter cells includes a plurality of switching elements,
the power conversion system further comprising:
a first control device to perform pulse-width control on the plurality of switching elements of each of the plurality of converter cells included in the first power converter according to a first carrier frequency; and
a second control device to perform the pulse-width control on the plurality of switching elements of each of the plurality of converter cells included in the second power converter according to a second carrier frequency smaller than the first carrier frequency.

Assignees

• Mitsubishi Electric Corp

Inventors

• Kikuchi Takeshi
• Nakamura Fuminori
• Uda Ryosuke

Classifications

• H02M7/4835

  comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage · CPC title

• H02M7/7575 Primary

  for high voltage direct transmission link · CPC title

• H02J3/36 Primary

  Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links · CPC title

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title