# US 2013/0154530 A1 · Variable Switching Frequency Power Converter

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- Number: US 2013/0154530 A1
- Document ID: US20130154530A1
- Status: Published application
- Kind: A1
- Application number: 13/716,877
- Filed: 2012-12-17
- Published: 2013-06-20
- Earliest claimed: 2011-12-16
- Assignees: Control Techniques Limited
- Inventors: Colin Hargis
- Web page: https://patentgrep.com/patent/US20130154530A1

## CPC

- H02P 27/06: using DC to AC converters or inverters (H02P27/05 takes precedence)
- H02P 27/08: with pulse width modulation
- H02P 2201/00: Indexing scheme relating to controlling arrangements characterised by the converter used
- H02P 2205/05: Torque loop, i.e. comparison of the motor torque with a torque reference
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A drive system for an electrical load such as an electric motor or generator comprises a PWM converter and a controller therefore. A signal indicative of a condition of the converter outpost is used in a controller to drive an optimal value of PWM switching frequency based on a load characteristic that is used to control the pulse switching frequency. The system takes account of the overall system in deriving an efficient PWM switching frequency.

## Claims

### Claim 1

A power converter system, comprising an electrical load, a power converter having a variable frequency output connected to the load, a controller operably connected to control the output of the power converter, means for producing a signal indicative of a load current, means for deriving a value of switching frequency of the output of the power converter based on an expression of a characteristic of the load and the signal, and means for setting the switching frequency of the power converter according to the value.

### Claim 2 (depends on 1)

A system as claimed in claim 1 in which the means for deriving include a look-up table.

### Claim 3 (depends on 1)

A system as claimed in claim 1 in which the means for deriving include means for running an algorithm.

### Claim 4 (depends on 1)

A system as claimed in claim 1 in which the means for deriving include means for running a mathematical expression, for example a polynomial expression.

### Claim 5 (depends on 1)

A system as claimed in claim 1 in which the means for producing a signal include a current transducer arranged in relation to the output of the power converter.

### Claim 6 (depends on 1)

A system as claimed in claim 1 in which the means for producing a signal include a current transducer arranged in relation to a supply to the power converter.

### Claim 7 (depends on 1)

A system as claimed in claim 1 in which the power converter produces an a.c. power output from a d.c. power input.

### Claim 8 (depends on 1)

A system as claimed in claim 1 in which the load is an electrical machine producing a mechanical output from an electrical power input, for example an electric motor, such as an a.c. induction motor.

### Claim 9 (depends on 1)

A system as claimed in claim 1 in which the load is an electrical power network and the power converter is supplied by a renewable energy source, such as photovoltaic cell or a wind power generator.

### Claim 10 (depends on 1)

A system as claimed in claim 1 in which means for setting are operable to set the switching frequency to optimise the efficiency of the system.

### Claim 11

A method of power conversion from a power converter having a variable frequency output connected to an electrical load, the method comprising producing a signal indicative of a load current, deriving a value of switching frequency of the output of the power converter based on an expression of a characteristic of the load and the signal, and setting the switching frequency of the power converter according to the value.