WO2017041977A1

WO2017041977A1 - Determination of intermediate circuit capacitance

Info

Publication number: WO2017041977A1
Application number: PCT/EP2016/069001
Authority: WO
Inventors: Harald Mangold; Andreas KNÖDLER; Stefan Walz
Original assignee: Robert Bosch Automotive Steering Gmbh
Priority date: 2015-09-07
Filing date: 2016-08-10
Publication date: 2017-03-16
Also published as: DE102015114916A1

Abstract

The description comprises an apparatus for measuring the intermediate circuit capacitance 1 of a control circuit for a servo drive of a steering system in a vehicle, comprising: a first output stage 2 for controlling a first machine part 10, a first current measuring apparatus 4, 5 for measuring a phase current I_U, I_W of the machine part 10 and a second resistor R2 and a third resistor R3 for forming a voltage divider for measuring the intermediate circuit voltage 1, wherein a switch S1 is arranged between a voltage supply UBAT for charging the intermediate circuit capacitance 1 and the intermediate circuit capacitance 1, wherein the switch S1 is open during measurement of the intermediate circuit capacitance.

Description

Determining the DC link capacity

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a device for measuring the

DC link capacitance of a drive circuit of a servo drive of a steering system of a vehicle, a steering system for a vehicle and a method for measuring the DC link capacity of a drive control of a steering system of a vehicle.

BACKGROUND OF THE INVENTION

In the prior art DC link capacitances are known, which also in

Ensure a constant DC voltage for a subsequent electronic unit. SUMMARY OF THE INVENTION

The measurement of a DC link capacitance can take place via a charging and / or discharging of this DC link capacitance. But there are big ones for that

DC link capacitances high currents required to obtain a measurement result in a manageable time. This results in large power losses, the

Use of large dimensioned components required. It is therefore an object to provide a method for measuring the DC link capacitance, which causes large power losses only to components that are already present in the circuit anyway for other reasons, and that are designed for these large power losses. Another task is to enable a measurement of the DC link capacity without additional hardware effort. It should only be used components that are present in the circuit for other reasons.

As a first embodiment of the invention, a device for measuring the DC link capacity of a drive circuit of a servo drive of a steering system of a vehicle is provided, comprising: a first output stage for driving a first divider, a first current measuring device for measuring a phase current of the divider and a second resistor and a third resistor for forming a voltage divider for measuring the DC link voltage, wherein a switch between a voltage supply for charging the DC link capacitance and the DC link capacitance is arranged, wherein the switch is open during the measurement of the DC link capacitance.

The device according to the invention is constructed in such a way that it uses the already existing elements of a drive of a servo drive to determine the DC link capacitance. Due to the double use, additional components for measuring the DC link capacitance can be dispensed with. Excluded is a resistor and / or a switch, the resistance between the

Supply voltage and the DC link capacitance is arranged and the switch can short-circuit the resistor. These two or at least one of these components must be arranged in addition and is not already available.

The switch and / or the resistor are necessary to allow discharge of the DC link capacitance. The job of the switch is in the

Normal operation to ensure a low-impedance current path to the sub-machines. During the measurement of the DC link capacitance, the switch is open. A sub-machine comprises several phases, in particular three or more than three phases, in which different phase currents can flow. All phase currents except one must be measured. The missing phase current can be calculated from the other phase currents. All phase currents together result in the discharge pattern with the switching pattern (PWM) of the final stage. The sum of

Phase currents are not equal to the discharge current. The relationship arises only when considering the different PWMs of the final stage half bridges associated with the phases. Typically, the phase currents

in terms of amount are a lot higher than the discharge current.

The task of the switch is to decouple the DC link from the supply voltage during the measurement of the DC link capacitance. In normal operation, the switch is closed so that the circuit and the sub-machines are connected to the supply voltage with low resistance.

As a second embodiment of the invention, a steering system for a vehicle is provided, wherein the steering system is a device according to one of

Claims 1 to 4 comprises.

As a third embodiment of the invention, a method is provided for measuring the DC link capacity of a drive control of a steering system of a vehicle, comprising the steps of: charging the DC link capacitance by a voltage supply, disconnecting the DC link

DC link capacitance from the power supply, measuring the voltage of the DC link capacitance, switching on a first output stage, so that the

DC link capacity is discharged by a phase current of a first sub-machine, measuring the discharge current and measuring the voltage of

DC link capacity.

Exemplary embodiments are set forth in the dependent claims

described. According to an exemplary embodiment of the invention, a device is provided, wherein a first resistance between the

Power supply and the DC link capacity is arranged.

By arranging a resistor between the voltage supply of the DC link capacitance and the DC link capacitance, a discharge of the DC link capacitance can be made possible. By using a switch which decouples the supply voltage from the intermediate circuit voltage, alternatively, a measurement of

DC link capacity are enabled. If no measurement takes place, closing the switch may cause a low-resistance connection between the

Supply voltage and the DC link are ensured.

According to a further exemplary embodiment of the present invention, a device is provided, the device comprising a second output stage for driving a second sub-machine and a second current-measuring device for measuring a phase current of the sub-machine.

By at least two output stages can be carried out in opposite directions, the generation of a discharge current while avoiding a

Torque relieved. According to an exemplary embodiment of the invention, an apparatus is provided, wherein between the second resistor and the third resistor, an analog-to-digital converter of a microcomputer or a microprocessor is arranged. According to an exemplary embodiment of the invention, a method is provided, comprising the step of switching on a second output stage, so that the DC link capacitance through a phase current of a second

Part machine is unloaded.

Torque relieved.

A torque can be avoided even with only one power amplifier and only one sub-machine. However, this is more difficult to realize because the phase currents in this case must be set exactly according to the position of the rotor.

In a further embodiment according to the invention, a method is provided, comprising the step: calculating the DC link capacitance as (discharge current · discharge time) / (first voltage - second voltage).

According to another embodiment of the present invention, there is provided a method wherein the measuring of the discharge current and the measurement of the intermediate circuit voltage is performed by a microprocessor or a microcomputer (μθ).

In one embodiment, the discharge time is not measured but by the

Microprocessor specified by switching on the power amplifier. The discharge current and the first and second voltages of the DC link capacitance are measured to determine the DC link capacitance.

As an idea of the invention can be considered to measure the

DC link capacitance only a partial discharge of the capacitors

Make the DC link capacitance and calculate the DC link capacitance based on the resulting measured values. Advantageously, the existing hardware can be used for this purpose. This can be one or both

Power amplifiers with their controlled sub-machines, current measuring shunts and an existing measuring device for measuring the DC link voltage be used. For the application of the method, the presence of two power amplifiers and dividing machines is not absolutely necessary, but it facilitates the generation of a discharge current while avoiding a torque by opposing control.

Of course, the individual features can also be combined with each other, which can also be partially beneficial effects that go beyond the sum of the individual effects. BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention will be apparent from the in the

Drawing illustrated embodiment clearly. 1 shows a circuit with DC link capacitors and power amplifiers.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS FIG. 1 shows a circuit with DC link capacitors C 1, C 2, C 3, which together form the DC link capacitance 1. The circuit has a first and a second output stage 2, 3, which are supplied by the DC voltage UBAT. Furthermore, current measuring shunt resistors 4, 5, 6, 7 are arranged. For measuring the intermediate circuit capacitance of the formula is used: C = (I _s Tiade * At _ent i _a de) / AU _e ntiade- The discharge current I _s Tiade can be determined by the current measurement shunts 4, 5, 6,. 7 The voltage loss AU _en tiade can be achieved by the already existing DC link voltage measuring device with an analog digital converter of the

Microprocessor μC ADC be made. The whole

DC link capacitance 1 results as the sum of the individual capacitances of the capacitors C1, C2 and C3. The DC link capacitance 1 is fiction, by a current flow through the power amplifier 2 and / or the power amplifier 3 and the sub-machine 10 and / or sub-machine 11 during a predetermined period of time discharged. The control of the power amplifier 2 and / or 3 is carried out so that at the

Overall machine no torque is generated. This results in a voltage drop of the DC link voltage 8. The DC link voltage 8 can via the

Resistor divider R2, R3 are measured by the microprocessor or microcomputer μC. By the partial discharge instead of a full discharge long-lasting high currents and high power losses can be avoided and a measurement of the DC link capacity can be made in a relatively short time. The switch Sl is opened during the measurement, so that a voltage drop of the intermediate circuit voltage 8 can result. The DC link capacitors C1, C2, C3 have charged themselves to UBAT via Rl or the closed switch S1 before starting a measurement. During a measurement, the switch S1 is opened and a discharge of the DC link capacitance takes place, wherein a first voltage value and a second voltage value are measured. The intermediate circuit voltage 8 can be measured by means of the voltage divider R2, R3 by the microprocessor μC at its ADC input ^ C ADC). A PWM is switched to the output stages 2 and / or 3, whereby the respective sub-machines 10, 11 are driven and a discharge of the DC link capacitance 1 takes place. The control can advantageously be such that on the overall machine no

Torque is generated. For example, a discharge of the

DC link capacitance 1 by one volt, to which a discharge time At _ent i _a d _{e is} necessary. The currents I _U flowing in this case _; I _w , Ιχ and I _z are measured by the shunt resistors 4, 5, 6, 7. After the discharge time At _en tiade, a measurement of the lower intermediate circuit voltage 8 is made by the μC ADC. This results in all figures of the formula C = (I _s * At Tiade _ent i _a de) / AU ntiade _e and the intermediate circuit capacitor 1 can be calculated.

It should be noted that the term "comprise" further elements or

Does not preclude procedural steps, just as the term "a" and "an" does not preclude several elements and steps. The reference numerals used are for convenience of reference only and are not to be considered as limiting, the scope of the invention being indicated by the claims.

LIST OF REFERENCE SIGNS

1 DC link capacity

2 first power amplifier

3 second power amplifier

4 current measuring shunt

5 current measuring shunt

6 current measuring shunt

7 current measuring shunt

8 Voltage of the DC link capacitance

ADC analog digital converter

Cl capacitor

C2 capacitor

C3 capacitor

Ientiade Average discharge current flowing during the partial discharge (determined over several samples of the discharge current during the partial discharge)

Partial discharge)

Iu current through a phase U of the submachine 10

Iw current through a phase W of the submachine 10

Power through a phase X of the submachine 11

I _Y current through a phase Y of the submachine 11th

Rl resistance

R2 resistance

R3 resistance

Sl switch

GND reference potential to supply voltage

UBAT supply voltage

Atentiade time period during which the discharge current I _s flows Tiade

AUentiade Voltage loss at the DC link capacitance by the

partial discharge

μC microcomputer

Claims

1. Device for measuring the DC link capacitance (1) a

A drive circuit of a servo drive of a steering system of a vehicle comprising:

a first output stage (2) for controlling a first sub-machine (10), a first current-measuring device (4, 5) for measuring a phase current (I _U; I _w ) of the sub-machine (10) and

a second resistor (R2) and a third resistor (R3) to

Forming a voltage divider for measuring the intermediate circuit voltage (1),

characterized in that

a switch (S l) between a voltage supply (UBAT) to

Charging the DC link capacitance (1) and the DC link capacitance (1) is arranged, wherein the switch (S l) during the measurement of

DC link capacity is open.

2. Device according to claim 1, characterized in that a first resistor (Rl) between the voltage supply and the DC link capacitance (1) is arranged.

3. Device according to one of claims 1 or 2, characterized in that the device comprises a second output stage (3) for controlling a second sub-machine (11) and a second current measuring device (6, 7) for measuring a phase current (I _x , I _z ) of the dividing machine (11).

4. Device according to one of the preceding claims, characterized in that between the second resistor (R2) and the third resistor (R3) an analog-to-digital converter ^ C ADC) of a microcomputer (μθ) or a microprocessor is arranged.

5. steering system for a vehicle, characterized in that the steering system comprises a device according to one of the preceding claims.

6. Method for measuring the DC link capacitance (1) of a drive of a servo drive of a steering system of a vehicle comprising the steps:

Charging the DC link capacitance (1) by a power supply (UBAT),

Disconnecting the DC link capacitance (1) from the power supply, measuring the voltage of the DC link capacitance (1),

Switching on a first output stage (2) so that the intermediate circuit capacitance is discharged by a phase current of a first dividing machine (10), measuring the discharge current and

Measuring the voltage of the DC link capacitance (1).

7. The method according to claim 6, characterized by the step:

Switching on a second output stage (3), so that the DC link capacitance is discharged by a phase current of a second sub-machine (11).

8. The method according to any one of claims 6 or 7, characterized by the step:

Calculating the DC link capacitance (1) as (discharge current)

Discharge time) / (first voltage - second voltage).

9. The method according to any one of claims 6 to 8, characterized in that the measurement of the discharge current and the measurement of the DC link voltage with a microprocessor or with a microcomputer (μθ) takes place.