Switched power converter

• US 9,391,538 B2
• Filed: 09/21/2011
• Issued: 07/12/2016
• Est. Priority Date: 09/21/2011
• Status: Active Grant

• Current Assignee: Canadian Solar Sses (UK) Ltd.
• Original Assignee: Princeton Power Systems Incorporated
• Inventors: Mohajerani, Zahra
• Primary Examiner(s): Wagner, Jenny L
• Assistant Examiner(s): Moats, Jr., Michael E
• Application Number:
  US13/238,688
• Publication Number:
  US 20130070499A1
• Time in Patent Office: 1,756 Days
• Field of Search: 363/13, 363/44, 363/45, 363/47, 363/48, 363/74, 363/78, 363/95, 363/97, 363/98
• US Class Current: 1/1
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: H02M 7/757 using semiconductor devices only

Abstract

A power converter includes a DC port and an AC port. A set of controllable “DC” switches couples the DC port to a central series-resonant circuit, and a set of “AC switches couples the central circuit through a filter to the AC port. A switch control circuit responds to secondary-to-tertiary and inversion time percentages, and a modulator is responsive to the AC filter voltage and to the current at the AC port, for generating the inversion (inv) and secondary-to-tertiary (s2t) time percentages.

Claims

1. A power converter, comprising:

a DC port;

a three-phase AC port;

a central resonant circuit having a resonant period;

a set of controllable “

DC”

switches for electrically interconnecting said DC port and said central resonant circuit;

a filter electrically connected to said AC port, said filter generating a voltage during operation of said converter;

a set of controllable “

AC”

switches for electrically interconnecting the central resonant circuit and said filter;

a switch control circuit responsive to a phase order, to a secondary-to-tertiary time percentage, and to an inversion time percentage for controlling inversion and normal conduction times of said DC and AC switches; and

a modulator responsive to said voltage at said DC port, to said voltage of said filter, to current command signals, and to the voltage at the AC port, for generating the phase order, the inversion time percentage and the secondary-to-tertiary time percentage;

wherein said phase order designates a first phase of the three-phase AC port as primary, and designates a second phase of the three-phase AC port as secondary, and designates a third phase of the three-phase AC port as tertiary;

wherein said inversion time percentage is a percentage of the resonant period of the central resonant circuit,

said inversion time percentage being used to determine a time of an end of an inversion state of a set of controllable switches, and said secondary-to-tertiary time percentage is used to determine a time of occurrence of a pulse transition from the secondary phase to the tertiary phase;

wherein said inversion time percentage is generated by said modulator based on said voltage at said DC port, on said voltage of said filter, on said current command signals, and on said voltage at the AC port; and

wherein said inversion time percentage is further used to determine a time when a polarity of the DC switches is flipped.

2. A converter according to claim 1, wherein said resonant circuit is a series-resonant circuit.

4. A converter according to claim 1, wherein said switch control circuit comprises:

a receiver for receiving said secondary-to-tertiary transition time and said inversion percentage command, and for calculating the switching times therefrom;

a current direction determining arrangement for finding the central link current direction;

a current polarity determining arrangement for determining the input and output current polarities;

an active switch finder for finding the active switches; and

a signal generator for generating the ON and OFF switch control signals for the active switches.

8. A power converter according to claim 1, wherein said central resonant circuit is a series resonant circuit.

3. A converter, comprising:

a DC port;

a three-phase AC port;

a central resonant circuit having a resonant period;

a set of controllable “

DC”

switches for electrically interconnecting said DC port and said central resonant circuit;

a filter electrically connected to said AC port,

said filter generating a voltage during operation of said converter;

a set of controllable “

AC”

switches for electrically interconnecting the central resonant circuit and said filter;

a switch control circuit responsive to a phase order, to a secondary-to-tertiary time percentage, and to an inversion time percentage for controlling inversion and normal conduction times of said DC and AC switches; and

a modulator responsive to said voltage at said DC port, to said voltage of said filter, to current command signals, and to the voltage at the AC port, for generating the phase order, the inversion time percentage and the secondary-to-tertiary time percentage

wherein said phase order designates a first phase of the three-phase AC port as primary, and designates a second phase of the three-phase AC port as secondary, and designates a third phase of the three-phase AC port as tertiary;

wherein said inversion time percentage is a percentage of the resonant period of the central resonant circuit, said inversion time percentage being used to determine a time of an end of an inversion state of a set of controllable switches, and said secondary-to-tertiary time percentage is used to determine a time of occurrence of a pulse transition from the secondary phase to the tertiary phase;

wherein said inversion time percentage is generated by said modulator based on said voltage at said DC port, on said voltage of said filter, on said current command signals, and on said the voltage at the AC port and

wherein said inversion time percentage is further used to determine a time when a polarity of the DC switches is flipped wherein said modulator comprises;

a primary-secondary-tertiary selector electrically connected to said filter for determining the phase order;

a norm calculator for calculating the norm of current command signals in response to said current command signals;

a subtractor for subtracting said norm of the current command signal from signal representing a maximum possible value of said current command signals, to generate said inversion time percentage;

a secondary-to-primary current ratio calculator for generating ideal secondary-to-primary ratio in response to said current command signals and said phase order;

a secondary-to-primary current ratio calculator for generating actual secondary-to-primary ratio in response to said phase order and a sample of said current at the AC port;

a proportional-integral processor for generating secondary-to-tertiary percentage adjustment signal in response to said ideal and actual secondary-to-primary ratios;

a summing processor for summing said secondary-to-primary percentage adjustment signal with said ideal secondary-to-primary ratio in response to said ideal secondary-to-primary ratio and said secondary-to-tertiary percentage adjustment signals, to produce said secondary-to-primary time percentage.

5. A controller for a power converter, said controller comprising:

a switch element controller for generating on-off control signals for first and second controllable switch sets of said power converter in response to an inversion time percentage and a secondary-to-tertiary time percentage; and

a modulator responsive to a filter voltage of a filter of said power converter and to a current at an AC port of the power converter, for generating the inversion time percentage and the secondary-to-tertiary time percentage;

wherein said inversion time percentage is a percentage of a resonant period of a central resonant circuit, said inversion time percentage being is used to determine a time of an end of an inversion state of a controllable switch set, and said secondary-to-tertiary time percentage is used to determine a time of occurrence of a pulse transition from the secondary phase to the tertiary phase;

wherein said inversion time percentage is generated by said modulator based on said filter voltage and on said current; and

wherein said inversion time percentage is also used to determine a time when a polarity of a set of controllable switches is flipped.

6. A controller according to claim 5, wherein said resonant central link is a series-resonant circuit.

7. A power converter comprising:

a DC port;

a three-phase AC port;

a central resonant circuit having a resonant period;

a set of controllable “

DC”

switches for electrically interconnecting said DC port and said central resonant circuit;

a filter electrically connected to said AC port, said filter generating a voltage during operation of said converter;

a set of controllable “

AC”

switches for electrically interconnecting the central resonant circuit and said filter;

an internal command generator for calculating the currents at the AC port to satisfy at least the desired converter power and DC voltage, and for generating internal current commands representing said currents at the AC port;

a switch control circuit electrically interconnected with said DC and AC switches, for selecting active switches in response to sensor feedback and said internal current commands, and for calculating switch ON and OFF times based on an inversion time command and a secondary-to-tertiary time command; and

a modulator responsive to said internal current commands, for calculating a required inversion time percentage and a secondary-to-tertiary time percentage to satisfy the current commands from the internal command generator;

wherein said inversion time percentage is a percentage of the resonant period of the central resonant circuit, said inversion time percentage being used to determine a time of an end of an inversion state of a set of controllable switches, and said secondary-to-tertiary time percentage is used to determine a time of occurrence of a pulse transition from the secondary phase to the tertiary phase;

wherein said inversion time percentage is generated by said modulator based on said internal current commands to satisfy the current commands from the internal command generator; and

wherein said inversion time percentage is further used to determine a time when a polarity of the DC switches is flipped.

9. A method for controlling a power converter, said method comprising the steps of:

generating an inversion time percentage and a secondary-to-tertiary time percentage in response to a voltage produced by a filter of the power converter and a current at an AC port of the power converter; and

generating on-off control signals for first and second controllable switch sets of the power converter in response to the inversion time percentage and to the secondary-to-tertiary time percentage;

wherein said inversion time percentage is a percentage of a resonant period of a resonant circuit and is used to determine a time of an end of an inversion state of a controllable switch set, and said secondary-to-tertiary time percentage is used to determine a time of occurrence of a pulse transition from the secondary phase to the tertiary phase;

wherein said inversion time percentage is generated based on said voltage and on said current; and

wherein said inversion time percentage is further used to determine a time when a polarity of a set of controllable switches is flipped.