# US 2014/0197774 A1 · Method and apparatus for controlling power converter with inverter output filter

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- Number: US 2014/0197774 A1
- Document ID: US20140197774A1
- Status: Published application
- Kind: A1
- Application number: 13/742,405
- Filed: 2013-01-16
- Published: 2014-07-17
- Earliest claimed: 2013-01-16
- Assignees: Rockwell Automation Technologies, Inc.
- Inventors: Jingbo Liu; Thomas Nondahl; Peter Schmidt; Semyon Royak
- Web page: https://patentgrep.com/patent/US20140197774A1

## CPC

- H02M 7/44: by static converters
- H02M 1/126: {using passive filters}
- H02P 21/0003: {Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control}
- H02P 21/06: Rotor flux based control involving the use of rotor position or rotor speed sensors
- H02P 23/28: Controlling the motor by varying the switching frequency of switches connected to a DC supply and the motor phases
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

Power converters and methods are presented for driving an AC load connected through an intervening filter circuit, in which at least one filter current or voltage signal or value is determined according to feedback signals or values representing an output parameter at an AC output of the power converter, and AC electrical output power is generated at the AC output based at least partially on the at least one filter current or voltage signal or value.

## Claims

### Claim 1

A power conversion system for driving a load through an intervening filter circuit, the power conversion system comprising:
an inverter comprising a DC input, an AC output, and a plurality of switching devices coupled between the DC input and the AC output and operative according to inverter switching control signals to convert DC electrical power received at the DC input to provide AC electrical output power at the AC output;
a controller configured to determine at least one filter current or voltage signal or value representing a filter capacitor current or filter inductor voltage of the intervening filter circuit based on at least one inverter output feedback signal or value representing an output current at the AC output of the inverter, and to provide the inverter switching control signals to the inverter at least partially according to the at least one filter current or voltage signal or value.

### Claim 2 (depends on 1)

The power conversion system of claim 1, wherein the controller is operative to:
compute at least one current setpoint value based on a desired velocity value and a motor velocity signal or value;
compute a filter capacitor current value representing current flowing in a filter capacitor of the intervening filter circuit based on:
the motor velocity signal or value,
a compensated voltage reference value, and
a filter capacitance value;
compute a compensated current setpoint value based on the at least one current setpoint value and the filter capacitor current value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated current setpoint value.

### Claim 3 (depends on 2)

The power conversion system of claim 2, wherein the controller is operative to:
compute a voltage reference value based on the compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
compute a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, the motor velocity signal or value, the filter capacitor current value, and a filter inductance value;
compute a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 4 (depends on 1)

The power conversion system of claim 1, wherein the controller is operative to:
compute a voltage reference value based on a compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
compute a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, a motor velocity signal or value, a filter capacitor current value, and a filter inductance value;
compute a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 5 (depends on 1)

The power conversion system of claim 1, wherein the power conversion system is a motor drive, and wherein the inverter provides the AC electrical output power at the AC output to drive a motor load through the intervening filter circuit.

### Claim 6 (depends on 5)

The power conversion system of claim 5, wherein the controller is operative to:
compute at least one current setpoint value based on a desired velocity value and a motor velocity signal or value;
compute a filter capacitor current value representing current flowing in a filter capacitor of the intervening filter circuit based on:
the motor velocity value,
a compensated voltage reference value, and
a filter capacitance value;
compute a compensated current setpoint value based on the at least one current setpoint value and the filter capacitor current value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated current setpoint value.

### Claim 7 (depends on 6)

The power conversion system of claim 6, wherein the controller is operative to:
compute a voltage reference value based on the compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
compute a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, the motor velocity signal or value, the filter capacitor current value, and a filter inductance value;
compute a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 8 (depends on 5)

The power conversion system of claim 5, wherein the controller is operative to:
compute a voltage reference value based on a compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
compute a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, a motor velocity signal or value, a filter capacitor current value, and a filter inductance value;
compute a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
provide the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 9

A method for controlling an AC electric motor connected to a motor drive through an intervening filter circuit, the method comprising:
determining at least one filter current or voltage signal or value representing a filter capacitor current or filter inductor voltage of the intervening filter circuit based on at least one motor drive output feedback signal or value representing an output current at an AC output of the motor drive; and
generating AC electrical output power at an AC output of the motor drive at least partially according to the at least one filter current or voltage signal or value.

### Claim 10 (depends on 9)

The method of claim 9, comprising:
determining a filter capacitor current value representing current flowing in a filter capacitor of the intervening filter circuit based on:
a motor velocity signal or value,
a compensated voltage reference value, and
a filter capacitance value;
computing a compensated current setpoint value based at least partially on the filter capacitor current value; and
providing inverter switching control signals to an inverter of the motor drive at least partially according to the compensated current setpoint value.

### Claim 11 (depends on 10)

The method of claim 10, comprising:
determining at least one current setpoint signal or value based at least partially on a desired motor velocity and the motor velocity signal or value; and
computing the compensated current setpoint value based on the at least one current setpoint value and the filter capacitor current value.

### Claim 12 (depends on 11)

The method of claim 11, comprising:
computing a voltage reference value based on the compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
computing a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, the motor velocity signal or value, the filter capacitor current value, and a filter inductance value;
computing a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
providing the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 13 (depends on 12)

The method of claim 12, comprising:
receiving a plurality of motor drive output feedback signals or values representing output currents at an AC output of the motor drive;
determining d and q axis inverter output current feedback signals or values in a stationary reference frame based at least partially on the plurality of motor drive output feedback signals or values;
computing the voltage reference value based on the compensated current setpoint value, and the d and q axis inverter output current feedback signals or values; and
computing the feed forward voltage reference value based on the d and q axis inverter output current feedback signals or values, the motor velocity signal or value, the filter capacitor current value, and the filter inductance value.

### Claim 14 (depends on 9)

The method of claim 9, comprising:
computing a voltage reference value based on a compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
computing a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, a motor velocity signal or value, a filter capacitor current value, and a filter inductance value;
computing a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
providing inverter switching control signals to an inverter of the motor drive at least partially according to the compensated voltage reference value.

### Claim 15 (depends on 14)

The method of claim 14, comprising:
receiving a plurality of motor drive output feedback signals or values representing output currents at an AC output of the motor drive;
determining d and q axis inverter output current feedback signals or values in a stationary reference frame based at least partially on the plurality of motor drive output feedback signals or values;
computing the voltage reference value based on the compensated current setpoint value, and the d and q axis inverter output current feedback signals or values; and
computing the feed forward voltage reference value based on the d and q axis inverter output current feedback signals or values, the motor velocity signal or value, the filter capacitor current value, and the filter inductance value.

### Claim 16

A non-transitory computer readable medium with computer executable instructions for controlling an AC electric motor connected to a motor drive through an intervening filter circuit, the computer readable medium comprising computer executable instructions for:
determining at least one filter current or voltage signal or value representing a filter capacitor current or filter inductor voltage of the intervening filter circuit based on at least one motor drive output feedback signal or value representing an output current at an AC output of the motor drive; and
generating AC electrical output power at an AC output of the motor drive at least partially according to the at least one filter current or voltage signal or value.

### Claim 17 (depends on 16)

The computer readable medium of claim 16, comprising computer executable instructions for:
determining a filter capacitor current value representing current flowing in a filter capacitor of the intervening filter circuit based on:
a motor velocity signal or value,
a compensated voltage reference value, and
a filter capacitance value;
computing a compensated current setpoint value based at least partially on the filter capacitor current value; and
providing inverter switching control signals to an inverter of the motor drive at least partially according to the compensated current setpoint value.

### Claim 18 (depends on 17)

The computer readable medium of claim 17, comprising computer executable instructions for:
determining at least one current setpoint signal or value based at least partially on a desired motor velocity and the motor velocity signal or value; and
computing the compensated current setpoint value based on the at least one current setpoint value and the filter capacitor current value.

### Claim 19 (depends on 18)

The computer readable medium of claim 18, comprising computer executable instructions for:
computing a voltage reference value based on the compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
computing a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, the motor velocity signal or value, the filter capacitor current value, and a filter inductance value;
computing a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
providing the inverter switching control signals to the inverter at least partially according to the compensated voltage reference value.

### Claim 20 (depends on 16)

The computer readable medium of claim 16, comprising computer executable instructions for:
computing a voltage reference value based on a compensated current setpoint value, and at least one inverter output current feedback signal or value representing an output current at the AC output of the inverter;
computing a feed forward voltage reference value based on the at least one inverter output current feedback signal or value, a motor velocity signal or value, a filter capacitor current value, and a filter inductance value;
computing a compensated voltage reference value based on the voltage reference value, and the feed forward voltage reference value; and
providing inverter switching control signals to an inverter of the motor drive at least partially according to the compensated voltage reference value.