Switched Power Converter

• US 20130070499A1
• Filed: 09/21/2011
• Published: 03/21/2013
• 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
• Granted Patent: US 9,391,538 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• 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;

an AC port;

a central resonant circuit;

a set of controllable “

DC”

switches electrically communicating with said DC port and said central resonant circuit;

a filter electrically communicating with said AC port, said filter generating a voltage during operation of said converter;

a set of “

AC”

switches electrically communicating with the central resonant circuit and said filter;

a switch control circuit responsive to phase order, to secondary-to-tertiary time percentage, and to 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, inversion time percentage and secondary-to-tertiary time percentages.

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

3. A converter according to claim 1, wherein said modulator comprises:

a primary-secondary-tertiary selector electrically communicating with 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.

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.

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 a power converter in response to inversion and secondary-to-tertiary time percentages; 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 and secondary-to-tertiary time percentages.

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;

an AC port;

a central resonant circuit;

a set of controllable “

DC”

switches electrically communicating with said DC port and said central resonant circuit;

a filter electrically communicating with said AC port, said filter generating a voltage during operation of said converter;

a set of “

AC”

switches electrically communicating with 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 communicating with said DC and AC switches, for selecting the active switches in response to sensor feedback and said internal current commands, and for calculating switch ON and OFF times using “

inversion” and

“

secondary-to-tertiary”

time commands; and

a modulator responsive to said internal current commands, for calculating the required percentage of “

inversion” and

“

secondary-to-tertiary”

time percentages to satisfy the current commands from the internal command generator.

11. A power converter according to claim 10, wherein said central resonant circuit is a series resonant circuit.

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

generating the inversion and secondary-to-tertiary time percentages 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 inversion and secondary-to-tertiary time percentages.