Granted Patent B2

US 12,651,973 · App. 18/023,798 · Granted Jun 9, 2026

Inventors: Michail Vasiladiotis (Zurich, CH); Nicolas Sierro (Uvrier, CH)

Assignee: Hitachi Energy Ltd.

H02M5/2932H02M1/0025H02M7/219H02M7/53871

Abstract

Claims (69)

1 . A method for operating a converter that comprises a control arrangement and Z modular-multilevel converters that are coupled in a parallel circuit, wherein each of the Z modular-multilevel converters comprises M branches, each of the M branches comprises cells with a capacitor and respective semiconductor switches, each of the Z modular-multilevel converters is configured to accept or provide a three-phase AC voltage, corresponding inputs of each of the Z modular-multilevel converters are connected together, corresponding outputs of each of the Z modular-multilevel converters are connected together, and Z and M are each an integer greater than one, the method comprising:

generating Z first voltage reference signals by a control module of the control arrangement as a function of a DC voltage reference and Z measured signals gained at the Z modular-multilevel converters;

generating a second voltage reference signal by the control module as a function of a first terminal reference;

generating an inner voltage reference signal by the control module as a function of at least an average DC voltage reference and of branch capacitor voltage signals generated by detecting capacitor voltages of the capacitors of the cells of each branch;

combining the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal into a branch control signal for each branch of each modular-multilevel converter by a reference computation module of the control arrangement;

generating cell control signals by Z valve control modules of the control arrangement as a function of the branch control signals, wherein each cell control signal of the cell control signals is a function of the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal; and

providing the cell control signals to each of the respective semiconductor switches of each of the cells of each of the M branches of each of the Z modular-multilevel converters.

2 . The method of claim 1 , wherein the reference computation module adds or subtracts at least one of the Z first voltage reference signals, the second voltage reference signal or the inner voltage reference signal for combining these signals into the branch control signal for each branch of each modular-multilevel converter.

3 . The method of claim 1 , wherein the control module is configured to:

receive the branch capacitor voltage signals;

generate Z inner voltage reference signals as a function of Z average DC voltage references and of the branch capacitor voltage signals; and

provide the Z inner voltage reference signals to the reference computation module.

4 . The method of claim 1 , wherein the reference computation module comprises Z reference computation blocks, and wherein a block of the Z reference computation blocks is configured to:

generate the branch control signal as a function of a first voltage reference signal of the Z first voltage reference signals, the second voltage reference signal and an inner voltage reference signal of Z inner voltage reference signals; and

provide the branch control signal to a valve control module of the Z valve control modules.

5 . The method of claim 1 , wherein each branch comprises N cells and a branch inductance that form a series circuit, N being an integer greater than one.

6 . The method of claim 1 , wherein each modular-multilevel converter of the Z modular-multilevel converters comprises a first terminal and a second terminal and wherein the M branches are respectively coupled to the first terminal via a first inductance, a second inductance and a third inductance of the converter.

7 . The method of claim 1 , wherein each modular-multilevel converter of the Z modular-multilevel converters comprises a first terminal and a second terminal and wherein the M branches are respectively coupled to the second terminal via a fourth inductance, a fifth inductance and a sixth inductance of the converter.

8 . The method of claim 1 ,

wherein each branch of the M branches comprises N cells and a branch inductance which form a series circuit, N being an integer greater than one;

wherein each modular-multilevel converter of the Z modular-multilevel converter comprises a first terminal and a second terminal;

wherein the M branches are respectively coupled to the first terminal via a first inductance, a second inductance and a third inductance of the converter; and

wherein the M branches are respectively coupled to the second terminal via a fourth inductance, a fifth inductance and a sixth inductance of the converter.

9 . The method of claim 1 ,

wherein the converter is realized as a direct AC/AC converter; and

wherein each branch comprises N cells that are realized as full-bridge cells, N being an integer greater than one.

10 . The method of claim 1 ,

wherein the converter is realized as a double star AC/DC converter; and

wherein each branch comprises N cells which are realized as half-bridge or full-bridge cells, N being an integer greater than one.

11 . The method of claim 1 ,

wherein the DC voltage reference is realized as a DC link voltage reference or a virtual DC link voltage reference; and

wherein the first terminal reference is a motor speed reference, an active power reference or a further grid voltage reference.

12 . The method of claim 1 ,

wherein the average DC voltage reference includes Z average DC voltage references; and

wherein one of the Z average DC voltage references is a function of detected capacitor voltages of the capacitors of the cells of each branch of one of the Z modular-multilevel converters.

13 . A converter, comprising

Z modular-multilevel converters that are coupled in a parallel circuit, wherein each modular-multilevel converter of the Z modular-multilevel converters comprises M branches, each branch comprises cells with a capacitor and respective semiconductor switches, each modular-multilevel converter of the Z modular-multilevel converters is configured to accept or provide a three-phase AC voltage, corresponding inputs of each of the Z modular-multilevel converters are connected together, corresponding outputs of each of the Z modular-multilevel converters are connected together, and Z and M are each an integer greater than one; and

a control arrangement configured to:

generate Z first voltage reference signals as a function of a DC voltage reference and Z measured signals gained at the Z modular-multilevel converters;

generate a second voltage reference signal as a function of a first terminal reference;

generate an inner voltage reference signal as a function of an average DC voltage reference and of branch capacitor voltage signals generated by detecting capacitor voltages of the capacitors of the cells of each branch;

combine the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal into a branch control signal for each branch of each modular-multilevel converter;

generate cell control signals as a function of the branch control signals, wherein each cell control signal of the cell control signals is a function of the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal; and

provide the cell control signals to each of the respective semiconductor switches of each of the cells of each of the M branches of each of the Z modular-multilevel converters.

14 . The converter of claim 13 , wherein the control arrangement includes Z valve control modules that are configured to generate the cell control signals.

15 . The converter of claim 13 ,

wherein each branch comprises N cells and a branch inductance which form a series circuit, N being an integer greater than one;

wherein each modular-multilevel converter of the Z modular-multilevel converters comprises a first terminal and a second terminal;

wherein the branches are respectively coupled to the first terminal via a first inductance, a second inductance and a third inductance of the converter; and

wherein the branches are respectively coupled to the second terminal via a fourth inductance, a fifth inductance and a sixth inductance of the converter.

16 . The converter of claim 13 ,

wherein the converter is realized as a direct AC/AC converter; and

wherein each branch comprises N cells that are realized as full-bridge cells, N being an integer greater than one.

17 . The converter of claim 13 ,

wherein the converter is realized as a double star AC/DC converter; and

wherein each branch comprises N cells which are realized as half-bridge or full-bridge cells, N being an integer greater than one.

18 . The converter of claim 13 ,

wherein the DC voltage reference is realized as a DC link voltage reference or a virtual DC link voltage reference; and

wherein the first terminal reference is a motor speed reference, an active power reference or a further grid voltage reference.

19 . The converter of claim 13 ,

wherein the average DC voltage reference includes Z average DC voltage references; and

wherein one of the Z average DC voltage references is a function of detected capacitor voltages of the capacitors of the cells of each branch of one of the Z modular-multilevel converters.

20 . A non-transitory computer readable medium comprising instructions to cause a converter to execute a method, the converter comprising Z modular-multilevel converters that are coupled in a parallel circuit, wherein each of the Z modular-multilevel converters comprises M branches, each branch comprises cells with a capacitor and respective semiconductor switches, each modular-multilevel converter of the Z modular-multilevel converters is configured to accept or provide a three-phase AC voltage, corresponding inputs of each of the Z modular-multilevel converters are connected together, corresponding outputs of each of the Z modular-multilevel converters are connected together, and Z and M are each an integer greater than one, the method comprising:

generating Z first voltage reference signals as a function of a DC voltage reference and Z measured signals gained at the Z modular-multilevel converters;

generating a second voltage reference signal as a function of a first terminal reference;

generating an inner voltage reference signal as a function of at least an average DC voltage reference and of branch capacitor voltage signals generated by detecting capacitor voltages of the capacitors of the cells of each branch;

combining the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal into a branch control signal for each branch of each modular-multilevel converter;

generating cell control signals as a function of the branch control signals, wherein each cell control signal of the cell control signals is a function of the Z first voltage reference signals, the second voltage reference signal and the inner voltage reference signal; and

providing the cell control signals to each of the respective semiconductor switches of each cell of each of the M branches of each of the Z modular-multilevel converters.

Assignments (3)

Priority Claims (1)

Continuity (1)

References Cited (14)