# US 10,309,996 B2 · Method for determining the phase currents of an electric machine having a converter

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- Number: US 10,309,996 B2
- Document ID: US10309996B2
- Status: Granted
- Kind: B2
- Application number: 15/322,971
- Filed: 2015-06-09
- Published: 2017-05-18
- Granted: 2019-06-04
- Earliest claimed: 2014-07-04
- Assignees: Robert Bosch GmbH; SEG Automotive Germany GmbH
- Applicants: Robert Bosch GmbH
- Inventors: Arunkumar Motaganahalli Srinivasamurthy; Julian Roesner
- Web page: https://patentgrep.com/patent/US10309996B2

## CPC

- G01R 25/00: Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
- B60L 7/18: Controlling the braking effect (B60L7/12, B60L7/14, B60L7/16 take precedence)
- G01R 31/006: {on road vehicles, e.g. automobiles or trucks (testing of ignition installations peculiar to internal combustion engines F02P17/00)}
- G01R 31/34: Testing dynamo-electric machines
- H02P 23/14: Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
- H02P 25/22: Multiple windings; Windings for more than three phases
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 7/2195: {the switches being synchronously commutated at the same frequency of the AC input voltage}
- 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
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- 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)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A method for determining the phase currents of an electric machine having a power converter, and a stator, the power converter having, for each phase, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal. The power converter is operated in an active rectification mode in which each upper switch is closed only as long as a phase voltage at the relevant upper switch is higher than a voltage at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage at the relevant lower switch is lower than a voltage at the lower DC voltage terminal; phase branch currents being measured in all the lower branches.

## Claims

### Claim 1

A method for determining phase currents of an electric machine, the electric machine including a power converter and a stator having at least four phases, the power converter having, for each of the at least four phases, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal, the method comprising:
operating the power converter in an active rectification mode in which each upper switch is closed only as long as a phase voltage with respect to ground at the relevant upper switch is higher than a voltage with respect to ground at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage with respect to ground at the relevant lower switch is lower than a voltage with respect to ground at the lower DC voltage terminal;
while the power converter is operating in the active rectification mode, measuring in each lower branch of the lower branches, a respective low-side phase branch current in the lower branch, to provide a respective measured phase current for each of the lower branches, the measuring and the providing being for all of the lower branches;
determining for each phase of the at least four phases, via a processor, a respective phase current of the phase, wherein the determined respective phase currents of the at least four phases are determined from only two of the respective measured phase branch currents having the greatest absolute values, wherein the processor is coupled to power converter and is configured to receive the respective measured phase branch currents at an input, the processor having a non-transitory machine readable storage medium storing program code for performing at least the determining step; and
controlling an active braking torque during a generator mode of the electric machine using the determined respective phase currents.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the respective low-side phase branch currents are measured in all the lower branches simultaneously.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein the respective low-side phase branch currents are measured in all the lower branches by way of a respective measuring resistor in each of the lower branches.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein the respective low-side phase branch currents are measured in all the lower branches in a regular time pattern.

### Claim 5 (depends on 1)

The method as recited in claim 1, wherein the respective low-side phase branch currents are measured in all the lower branches independently of switching times of the active rectification mode.

### Claim 6 (depends on 1)

The method as recited in claim 1, wherein the determined phase currents are determined based on angular distances between the at least four phases.

### Claim 7 (depends on 1)

The method as recited in claim 1, wherein a battery voltage is applied between the upper DC voltage terminal and the lower DC voltage terminal.

### Claim 8

A computation unit for determining phase currents of an electric machine, the electric machine including a power converter and a stator having at least four phases, the power converter having, for each of the at least four phases, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal, comprising:
a computation device having program code stored on a non-transitory computer, which is executable by a processor, for performing the following:
operating the power converter in an active rectification mode in which each upper switch is closed only as long as a phase voltage with respect to ground at the relevant upper switch is higher than a voltage with respect to ground at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage with respect to ground at the relevant lower switch is lower than a voltage with respect to ground at the lower DC voltage terminal;
while the power converter is operating in the active rectification mode, measuring in each lower branch of the lower branches, a respective low-side phase branch current in the lower branch, to provide a respective measured phase current for each of the lower branches, the measuring and providing being for all of the lower branches;
determining for each phase of the at least four phases a respective phase current of the phase, wherein the determined respective phase currents of the at least four phases are determined from only two of the respective measured phase branch currents having the greatest absolute values; and
controlling an active braking torque during a generator mode of the electric machine using the determined respective phase currents;
wherein the processor is coupled to the power converter and is configured to receive and is configured to receive the respective measured phase branch currents at an input.

### Claim 9

A motor vehicle electrical system, comprising:
an electric machine having a power converter and a stator having at least four phases, the power converter having, for each of the at least four phases, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal; and
a computation unit for determining phase currents of the electric machine, the computation unit having a non-transitory machine readable storage medium storing program code, the program code, when executed by the computation unit, causing the computation unit to perform the following:
while the power converter is operating in the active rectification mode, operating the power converter in an active rectification mode in which each upper switch is closed only as long as a phase voltage with respect to ground at the relevant upper switch is higher than a voltage with respect to ground at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage with respect to ground at the relevant lower switch is lower than a voltage with respect to ground at the lower DC voltage terminal;
while the power converter is operating in the active rectification mode, measuring in each lower branch of the lower branches, a respective low-side phase branch current in the lower branch, to provide a respective measured phase current for each of the lower branches, the measuring and providing being for all of the lower branches;
determining for each phase of the at least four phases a respective phase current of the phase, wherein the determined respective phase currents of the at least four phases are determined from only two of the respective measured phase branch currents having the greatest absolute values; and
controlling an active braking torque during a generator mode of the electric machine using the determined respective phase currents;
wherein the computation unit is coupled to the power converter and is configured to receive and is configured to receive the respective measured phase branch currents at an input.

### Claim 10 (depends on 9)

The motor vehicle electrical system as recited in claim 9, further comprising:
an electrical energy reservoir that is connected between the upper DC voltage terminal and the lower DC voltage terminal.

### Claim 11

A non-transitory machine-readable storage medium on which is stored a computer program, which is executable by a processor, comprising:
a program code arrangement having program code for determining phase currents of an electric machine, the electric machine including a power converter and a stator having at least four phases, the power converter having, for each of the at least four phases, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal, the computer program, when executed by a computation unit, by performing the following:
operating the power converter in an active rectification mode in which each upper switch is closed only as long as a phase voltage with respect to ground at the relevant upper switch is higher than a voltage with respect to ground at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage with respect to ground at the relevant lower switch is lower than a voltage with respect to ground at the lower DC voltage terminal;
while the power converter is operating in the active rectification mode, measuring, in each lower branch of the lower branches, a respective low-side phase branch current in the lower branch, to provide a respective measured phase current for each of the lower branches, the measuring and providing being for all of the lower branches;
determining for each phase of the at least four phases a respective phase current of the phase, wherein the determined respective phase currents of the at least four phases are determined from only two of the respective measured phase branch currents having the greatest absolute values; and
controlling an active braking torque during a generator mode of the electric machine using the determined respective phase currents;
wherein the computation unit is coupled to the power converter is configured to receive the respective measured phase branch currents at an input.