OPTIMIZED CONTROL OF A POWER CONVERTER IN RESPONSE TO LOAD CONDITIONS

• US 20130307339A1
• Filed: 03/05/2013
• Published: 11/21/2013
• Est. Priority Date: 05/16/2012
• Status: Active Grant

• Current Assignee: Acleap Power Incorporated
• Original Assignee: General Electric Company
• Inventors: Reddy, Raghothama, Subramanium, Palanivel, Smith, Darwin
• Granted Patent: US 9,373,964 B2
• Time in Patent Office: Days
• US Class Current: 307/66
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2300/20 The dispersed energy generation being of renewable origin
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: Y02B 10/10 Photovoltaic [PV]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A power converter and a method of operating the same is described, for use in a power conversion system that is capable of receiving power from various sources, including renewable sources, for delivering power to a load. Power type detection circuitry is provided for identifying the type of power source at the input of each power detector, based on attributes of the time-varying power received. The power converter is constructed of a boost stage followed by a galvanically isolated DC-DC converter stage. If a renewable input power source is detected, the boost stage is controlled to operate at a maximum power point, and the DC-DC converter stage is operated in an open loop manner when load exceeds available power at input. The load falls below available input power, the boost stage is controlled to regulate its output voltage and DC-DC converter stage is also placed under closed loop control. If the AC grid is detected as the input power source, the boost stage is controlled to attain maximum power factor, and the DC-DC converter stage is placed under feedback control of the output voltage.

Claims

1. A power converter, comprising:

a power converter circuit having a converter input to receive a renewable-source power;

controller circuitry having a controller output, the controller output coupled to a second converter input of the power converter circuit;

the power converter circuit having a converter output, the converter output coupled to a controller input of the controller circuitry; and

within the controller circuitry, a controller circuitry setup to operate the power converter circuit at an operating point selected to maximize power converted from the renewable-source power and the controller circuitry setup further to supply the converter output at a higher priority for renewable-source power than for metered power for a power converter output load above a user-set threshold.

2. The power converter of claim 1, wherein the power converter circuit comprises:

a boost stage having a boost input node and a boost output node, wherein the boost input node comprises an input node of the power converter circuit;

a DC-DC converter stage having a DC-DC converter first input and a DC-DC converter output;

the DC-DC converter first input is coupled to the boost output node; and

the DC-DC converter output is galvanically isolated from the DC-DC converter first input, wherein the DC-DC converter stage is configured to generate DC power responsive to a boost stage voltage.

3. The power converter of claim 1, wherein the controller circuitry is configured to control an output voltage at the converter output according to a setpoint voltage responsive to the output voltage below the user-set threshold.

4. A method of operating a power converter to convert received from a power source to DC power, the method comprising:

operating a boost stage in the power converter to generate a DC boost voltage from the received power;

operating a resonant DC-DC converter in the power converter to produce DC power at an output from the DC boost voltage;

comparing a monitored voltage corresponding to the DC boost voltage with a low load threshold;

responsive to the monitored voltage being below the low load threshold, controlling the power converter according to a first control mode, comprising;

controlling the boost stage to operate at an operating point selected to maximize power converted from the power source; and

responsive to the monitored voltage being above the low load threshold, controlling the power converter according to a second control mode, comprising;

applying power factor compensation or feedback control at the boost stage; and

controlling the DC-DC converter to produce DC power at the output according to a setpoint voltage.

5. The method of claim 4, wherein the DC-DC converter includes a resonant type;

and wherein the controlling the power converter according to the first control mode further comprises controlling the DC-DC converter to operate at resonance.

6. The method of claim 4, wherein the comparing comprises:

sampling the voltage corresponding to the DC boost voltage;

and wherein the controlling comprise executing program instructions at programmable logic on a sequence of the sampled voltages.

7. The method of claim 4, further comprising:

after the controlling the power converter according to the second control mode, and responsive to the monitored voltage being below a second threshold, then controlling the power converter according to the first control mode.

8. A power converter system for producing a DC output voltage from one or more of a plurality of power sources, comprising:

a plurality of isolating power converters, each comprising;

a power converter circuit having an input and an output, and configured to receive input power from a power source and to present DC power at its output; and

controller circuitry, coupled to the power converter circuit to receive a bus voltage corresponding to the voltage at the output of the power converter circuit, the controller circuitry configured to operate the power converter circuit at an operating point selected to maximize power converted from the power source responsive to the bus voltage above a low load threshold, and configured to control the voltage at the output of the power converter circuit according to a setpoint voltage responsive to the bus voltage below the low load threshold.

wherein the outputs of the isolating power converters are connected together at for coupling to a load.

9. The power converter system of claim 8, further comprising:

a battery backup subsystem coupled to the outputs of the isolating power converters.

10. The power converter system of claim 8, wherein each of the isolating power converters comprises:

a boost stage configured to generate a DC boost voltage from power received at the input of the power converter circuit; and

a converter stage, having an input coupled to receive the DC boost voltage, and having an output galvanically isolated from its input, the converter stage configured to generate DC power at its output responsive to the DC boost voltage;

and wherein the controller circuitry comprises;

a pulse width modulator, having an output coupled to the boost stage;

a maximum power point tracking controller, having a first input coupled to the power type detection function, having a current sense input coupled to an input to the boost stage, and having an output;

a power factor compensation function or a feedback control function, having a first input coupled to an input to the boost stage, having a second input coupled to an output of the boost stage, and having an output; and

a control mode select function, having an input coupled to the boost stage to receive the bus voltage, configured to couple the output of the maximum power point tracking controller to an input of the pulse width modulator responsive to the bus voltage above a low load threshold, and to couple the output of the power factor compensation function to the input of the pulse width modulator responsive to the bus voltage below the low load threshold.

11. The power converter system of claim 8, further comprising:

power type detection circuitry operable to detect a type of power received at the input of the power converter circuit; and

wherein the controller circuitry is coupled to the power type detection circuitry, and is configured to operate the power converter circuit at an operating point selected to maximize power converted from the power source responsive to the power type detection circuit detecting that the power at the input is of a first type in combination with the bus voltage above a low load threshold and, and to apply power factor compensation in the power converter circuit responsive either to the power type detection circuit detecting that the power at the input is of a second type or to the power type detection circuit detecting that the power at the input is of a first type in combination with the bus voltage below the low load threshold;

wherein power of the first type comprises power generated from a source selected from the group consisting of solar cell arrays, wind-powered generators, geothermal-powered generators, and water-powered generators;

and wherein power of the second type comprises power generated from a source selected from the group consisting of the AC electrical grid and fossil-fueled generators.

12. The power converter system of claim 8, further comprising:

a system controller, coupled to each of the isolating power converters, configured to set the setpoint voltage of the controller circuitry of each of the isolating power converters.