POWER CONVERTER, POWER GENERATION SYSTEM, CONTROL APPARATUS, AND POWER CONVERSION METHOD

• US 20150280612A1
• Filed: 03/20/2015
• Published: 10/01/2015
• Est. Priority Date: 03/31/2014
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: IDE, Kozo, NARITA, Tetsumi, FUJISAKI, Seiji, TAKAKI, Mamoru, MORIMOTO, Shinya
• Granted Patent: US 9,509,233 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A power converter according to embodiments includes a boost circuit, a single-phase inverter, a current controller, and a power conversion controller. The current controller generates a voltage reference based on a difference between current output from the single-phase inverter and a current reference. The power conversion controller controls the single-phase inverter to generate a first portion of the AC voltage, and controls the boost circuit to generate a second portion of the AC voltage. The first portion corresponds to the voltage reference of which an absolute value is smaller than the voltage of the DC power supply. The second portion corresponds to the voltage reference of which an absolute value is greater than the voltage of the DC power supply.

Claims

1. A power converter comprising:

a boost circuit configured to boost a voltage of a direct-current (DC) power supply;

a single-phase inverter configured to output an alternating-current (AC) voltage based on a voltage output from the boost circuit;

a current controller configured to generate a voltage reference based on a difference between a current output from the single-phase inverter and a current reference; and

a power conversion controller configured to control the single-phase inverter to generate a first portion of the AC voltage, and to control the boost circuit to generate a second portion of the AC voltage, the first portion according to the voltage reference of which an absolute value is smaller than the voltage of the DC power supply, and the second portion according to the voltage reference of which an absolute value is greater than the voltage of the DC power supply.

2. The power converter according to claim 1, further comprising:

a maximum power point tracking (MPPT) controller configured to generate a supply voltage reference to maximize a power supplied from the DC power supply to the boost circuit, based on the voltage and a current of the DC power supply; and

a supply voltage controller configured to generate the current reference based on a difference between the supply voltage reference and the voltage of the DC power supply.

3. The power converter according to claim 1, wherein

the power conversion controller includes:

a boost controller configured to perform boost control on the boost circuit based on the voltage reference;

a single-phase inverter controller configured to perform pulse width modulation (PWM) control on the single-phase inverter based on the voltage reference; and

a switch configured to switch between the boost control of the boost controller and the PWM control of the single-phase inverter controller, based on the voltage reference and the voltage of the DC power supply.

4. The power converter according to claim 1, wherein

the current controller includes:

a current distortion extractor configured to extract a distortion component of a current output from the single-phase inverter; and

a corrector configured to correct the voltage reference based on the distortion component extracted by the current distortion extractor, and

the power conversion controller controls the boost circuit and the single-phase inverter based on the voltage reference corrected by the corrector.

5. The power converter according to claim 1, wherein

the current controller includes:

a coordinate converter configured to convert a current output from the single-phase inverter into a pair of signals orthogonal to each other on orthogonal coordinates;

a phase detector configured to detect a voltage phase of an AC power supply connected to the single-phase inverter; and

a dq converter configured to convert the pair of signals into a d-axis component and a q-axis component in a dq coordinate system by using rotation coordinate transformation by the voltage phase detected by the phase detector,

the current reference includes a d-axis current reference and a q-axis current reference, and

the current controller generates a d-axis voltage reference based on a difference between the d-axis current reference and the d-axis component and generates a q-axis voltage reference based on a difference between the q-axis current reference and the q-axis component.

6. The power converter according to claim 1, wherein

the boost circuit includes:

a reactor having one end connected to the DC power supply;

a first switching element connected in parallel with the DC power supply through the reactor;

a diode connected between the other end of the reactor and the single-phase inverter; and

a second switching element connected in inverse parallel with the diode, and

the power conversion controller alternately turns on the first switching element and the second switching element in a period in which the boost circuit is controlled such that the boost circuit generates the second portion of the AC voltage.

7. The power converter according to claim 6, wherein a set of one or more switching elements of the boost circuit, a set of switching elements of the single-phase inverter, or both of the sets include wide-bandgap semiconductors containing gallium nitride (GaN) or silicon carbide (SiC).

8. The power converter according to claim 1, wherein the power conversion controller adjusts a percent modulation determined based on the voltage reference and the voltage of the DC power supply by using an adjustment gain and controls the boost circuit to generate the second portion of the AC voltage, based on the adjusted percent modulation.

9. The power converter according to claim 1, wherein the current controller sets a current control gain in a case where the voltage reference having an absolute value greater than the voltage of the DC power supply is generated, to be greater than a current control gain in a case where the voltage reference having an absolute value smaller than the voltage of the DC power supply is generated.

10. A power generation system comprising:

the power converter as claimed in claim 1; and

a power generator that supplies DC power to the power converter, the power generator corresponding to the DC power supply.

11. A control apparatus comprising:

a current controller configured to generate a voltage reference based on a difference between a current reference and a current output from a single-phase inverter that outputs an alternating-current (AC) voltage based on a voltage output from a boost circuit that boosts voltage of a direct-current (DC) power supply; and

a power conversion controller configured to control the single-phase inverter to generate a first portion of the AC voltage, and to control the boost circuit to generate a second portion of the AC voltage, the first portion according to the voltage reference of which an absolute value is smaller than the voltage of the DC power supply, and the second portion according to the voltage reference of which an absolute value is greater than the voltage of the DC power supply.

12. A power converter comprising:

a boost circuit configured to boost a voltage of a direct-current (DC) power supply;

a single-phase inverter configured to output an alternating-current (AC) voltage based on a voltage output from the boost circuit;

means for switching between voltage control on the boost circuit and voltage control on the single-phase inverter; and

means for suppressing a distortion of a current output from the single-phase inverter when the switching is performed.

13. A power conversion method comprising:

generating a voltage reference based on a difference between a current reference and a current output from a single-phase inverter that outputs an alternating-current (AC) voltage based on a voltage output from a boost circuit connected to a direct-current (DC) power supply;

boosting, in the boost circuit, a voltage of the DC power supply to a voltage according to the voltage reference, of which an absolute value is greater than the voltage of the DC power supply, to generate a first portion of the AV voltage; and

generating, in the single-phase inverter, a second portion of the AC voltage according to the voltage reference, of which an absolute value is smaller than the voltage of the DC power supply.