# US 2014/0152093 A1 · Method for operating an electrical system, and apparatus for controlling an electrical system

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- Number: US 2014/0152093 A1
- Document ID: US20140152093A1
- Status: Published application
- Kind: A1
- Application number: 14/233,951
- Filed: 2012-07-04
- Published: 2014-06-05
- Earliest claimed: 2011-07-21
- Assignees: Robert Bosch GmbH
- Inventors: Klaus-Juergen Wald; Martin Wirth
- Web page: https://patentgrep.com/patent/US20140152093A1

## CPC

- B60L 58/12: responding to state of charge [SoC]
- B60L 3/0046: {relating to electric energy storage systems, e.g. batteries or capacitors}
- B60L 3/04: Cutting off the power supply under fault conditions (protective devices and circuit arrangements in general H01H; H02H)
- B60L 7/14: for vehicles propelled by AC motors
- B60L 50/15: with additional electric power supply (with capacitors charged by engine-driven generators B60L50/40; with batteries charged by engine-driven generators B60L50/61)
- B60L 50/16: with provision for separate direct mechanical propulsion
- B60L 50/61: by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
- B60L 2210/40: DC to AC converters
- B60L 2240/421: Speed
- B60L 2240/427: Voltage
- B60L 2260/28: Four wheel or all wheel drive
- Y02T 10/62: Hybrid vehicles
- Y02T 10/64: Electric machine technologies in electromobility
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- Y02T 10/7072: Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
- Y02T 10/72: Electric energy management in electromobility
- 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
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

The present invention relates to a method (50) for operating an electrical system (44), particularly in a motor vehicle (10), wherein the electrical system (44) has at least two electrical machines (14, 34) which are connected to the electrical system (44) via one controllable inverter (32, 42) each, wherein a regulated generator mode for a first instance of the electrical machines (14, 34) is initiated (60), characterized in that a first step (54) involves detection of a drop below a first prescribable voltage value for the electrical voltage available in the electrical system (44), and then a second step (56), on the basis of an induced freewheeling voltage that is to be expected for one of the electrical machines (14, 32), involves one of the inverters (32, 42) being selected, which is associated with an electrical machine (14, 32), and being actuated such that the electrical machine (14, 34) connected thereto is operated in electrical freewheel, with the result that the rotation of said machine causes it to induce a freewheeling voltage which is applied in the electrical system (44), and then a third step (58) involves detection of the rise above a second prescribable voltage value for the induced electrical freewheeling voltage available in the electrical system (44), and then a fourth step (60) involves the inverter (32, 42) of the first electrical machine (14, 34) being actuated such that the first electrical machine (14, 34) connected thereto is operated in regulated generator mode.

## Claims

### Claim 1

A method (50) for operating an electrical system (44), wherein the electrical system (44) has at least two electrical machines (14, 34) which are connected to the electrical system (44) by a controllable inverter (32, 42) in each case, wherein a regulated generator mode of a first of the electrical machines (14, 34) is initiated (60), characterized in that, in a first step (54), detecting a situation of the electrical voltage which is available in the electrical system (44) falling below a first predefinable voltage value, and then, in a second step (56), depending on an expected induced freewheeling voltage of one of the electrical machines (14, 32), one of the inverters (32, 42), which is associated with one of the electrical machines (14, 32), is selected and is actuated such that the electrical machine (14, 34) which is connected to the selected and actuated one of the inverters (32, 42) is operated in electrical freewheel mode, so that said electrical machine, as a result of its rotation, induces a freewheeling voltage which is applied to the electrical system (44), and then, in a third step (58), detecting the situation of the induced electrical freewheeling voltage which is available in the electrical system (44) exceeding a second predefinable voltage value, and then, in a fourth step (60), the inverter (32, 42) of the first electrical machine (14, 34) is actuated such that the first electrical machine (14, 34) which is connected to it is operated in the regulated generator mode.

### Claim 2 (depends on 1)

The method as claimed in claim 1, characterized in that the electrical system (44) has at least one electrical energy store (46), and in that a regulated generator mode of a first of the electrical machines (14, 34) is initiated during operation of the vehicle after disconnection (54) of the electrical energy store (46) from the electrical system (44), for the further supply of electrical energy to the electrical system (44).

### Claim 3 (depends on 1)

The method as claimed in claim 1, characterized in that the electrical system (44) further has a voltage regulator (48) which regulates the induced generator voltage in the electrical system (44) in the regulated generator mode of the first electrical machine (14, 34).

### Claim 4 (depends on 1)

The method as claimed in claim 1, wherein the first electrical machine (14) is connected to a crankshaft (20) of an internal combustion engine (16) of the motor vehicle (10), and the at least one further electrical machine (34) is connected to an axle of the motor vehicle (10).

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein the first electrical machine (14) and the at least one further electrical machine (34) are operated at different rotation speeds.

### Claim 6 (depends on 1)

The method as claimed in claim 1, wherein the first electrical machine (14) and the at least one further electrical machine (34) have different freewheeling characteristic curves.

### Claim 7 (depends on 1)

The method as claimed in claim 1, wherein the expected induced freewheeling voltage of the respective electrical machine (14, 34) is determined on the basis of the respective rotation speed and the respective freewheeling characteristic curve.

### Claim 8 (depends on 7)

The method as claimed in claim 7, wherein a regulated generator mode of a first of the electrical machines (14, 34) is initiated for generating a generator voltage in the electrical system (44) with a predefined generator voltage setpoint value, wherein the electrical machine (14, 34) selected for generating the freewheeling voltage in the electrical system (44) is that of which the expected induced freewheeling voltage deviates least from a predefined generator voltage setpoint value.

### Claim 9 (depends on 7)

The method as claimed in claim 7, wherein that electrical machine of which the expected induced freewheeling voltage lies outside a permissible voltage range is precluded from being used as the electrical machine (14, 34) for generating the freewheeling voltage in the electrical system (44).

### Claim 10 (depends on 1)

The method as claimed in claim 1, wherein the regulated generator mode of the first electrical machine is performed by a pulse-width-modulation method.

### Claim 11 (depends on 1)

The method as claimed in claim 1, characterized in that the first and the second predefinable voltage values have the same magnitude.

### Claim 12 (depends on 1)

An apparatus (48) for controlling an electrical system (44), comprising a voltage detector (49) configured to detect an electrical voltage in the electrical system (44), and a control unit (48) which is configured to execute the method (50) as claimed in claim 1.

### Claim 13 (depends on 12)

An electrical system (44), comprising an electrical energy store (46), and at least two electrical machines (14, 34) which are connected to the electrical system (44) by a controllable inverter (32, 42) in each case, and comprising a control unit (48) as claimed in claim 12.

### Claim 14 (depends on 1)

The method as claimed in claim 1, wherein the electrical system (44) is an electrical system of a motor vehicle (10).

### Claim 15 (depends on 1)

The method as claimed in claim 1, wherein the least one electrical energy store (46), is an electrical high-voltage energy store (46).

### Claim 16 (depends on 1)

The method as claimed in claim 1, wherein the first electrical machine (14) is connected to a crankshaft (20) of an internal combustion engine (16) of the motor vehicle (10), and the at least one further electrical machine (34) is connected to a wheel (40R, 40L) of the motor vehicle (10).

### Claim 17 (depends on 1)

The method as claimed in claim 1, wherein the expected induced freewheeling voltage of the respective electrical machine (14, 34) is determined on the basis of the respective rotation speed.

### Claim 18 (depends on 1)

The method as claimed in claim 1, wherein the expected induced freewheeling voltage of the respective electrical machine (14, 34) is determined on the basis of the respective freewheeling characteristic curve.

### Claim 19 (depends on 12)

The apparatus (48) as claimed in claim 12, wherein the electrical system (44) is an electrical system (44) of a motor vehicle (10).

### Claim 20 (depends on 13)

The electrical system (44), as claimed in claim 13, wherein the electrical system (44) is an electrical system (44) of a motor vehicle (10) and the electrical energy store (46) is an electrical high-voltage energy store (46).