Conversion system and control method thereof

A control method for controlling a conversion system, wherein the conversion system comprises:

• N power converters, each of the power converters comprising a first side and a second side, the first sides of the N power converters being electrically coupled in series, and
• N controllers, one-to-one corresponding to the N power converters, and each of the controllers receiving a first side current and a second side voltage of a corresponding power converter;
• the control method comprising:
• S1, receiving, by each of at least (N−1) controllers of the N controllers, a neighboring direct current voltage signal which only reflects second side voltages of other M power converters;
• and
• S2, generating, by each of at least (N−1) controllers of the N controllers, a control signal for controlling the first side voltage of the corresponding power converter according to the neighboring direct current voltage signal, and the first side current and the second side voltage of the corresponding power converter,
• wherein N≥3, 1≤M≤(N−2), and M and N are integers,
• wherein the S2 comprises:
• S11, calculating a local common mode signal according to the neighboring direct current voltage signal and the second side voltage of the corresponding power converter;
• S12, generating a control command according to the local common mode signal, and the first side current and the second side voltage of the corresponding power converter;
• and
• S13, performing modulation on the control command, to generate the control signal,
• wherein the S12 comprises:
• S121, generating a given signal according to the local common mode signal and a preset voltage reference value;
• S122, generating a differential mode command according to the local common mode signal, and the second side voltage and the first side current of the corresponding power converter;
• S123, generating a common mode command according to a preset current reference value, the given signal and the first side current of the corresponding power converter;
• and
• S124 performing a calculation on the common mode command and the differential mode command, and generating the control command.

A conversion system, comprising:

• N power converters, each of the power converters comprising a first side and a second side, the first sides of the N power converters being electrically coupled in series, and
• N controllers, one-to-one corresponding to the N power converters, and each of the controllers receiving a first side current and a second side voltage of a corresponding power converter,
• wherein each of at least (N−1) controllers receives a neighboring direct current voltage signal which only reflects second side voltages of other M power converters in the conversion system, and generates a control signal for controlling the first side voltage of the corresponding power converter according to the neighboring direct current voltage signal, and the first side current and the second side voltage of the corresponding power converter, wherein N≥3, 1≤M≤(N−2), and M and N are integers,
• wherein an information transmission structure among the N controllers is a balanced diagram,
• wherein each of the N controllers comprises:
• a calculating unit, configured to calculate a local common mode signal according to the neighboring direct current voltage signal and the second side voltage of the corresponding power converter;
• a command generating unit, configured to generate a control command according to the local common mode signal, and the first side current and the second side voltage of the corresponding power converter;
• and
• a modulating unit, configured to perform modulation on the control command, to generate the control signal,
• wherein the command generating unit comprises:
• a common mode voltage loop, configured to generate a given signal according to the local common mode signal and a preset voltage reference value;
• a current loop, configured to generate a common mode command according to a preset current reference value, the given signal and the first side current of the corresponding power converter;
• a differential mode voltage loop, configured to generate a differential mode command according to the local common mode signal, and the second side voltage and the first side current of the corresponding power converter;
• and
• a command synthesis unit, configured to perform a calculation on the common mode command and the differential mode command, and generate the control command.