WO2017016747A1

WO2017016747A1 - Method and device for operating an electric system

Info

Publication number: WO2017016747A1
Application number: PCT/EP2016/063878
Authority: WO
Inventors: Gholamabas Esteghlal; Markus Kretschmer; Frank Haefele
Original assignee: Robert Bosch Gmbh
Priority date: 2015-07-28
Filing date: 2016-06-16
Publication date: 2017-02-02
Also published as: DE102015214231A1

Abstract

The invention relates to a method for operating an electric system (1) of a motor vehicle, which comprises at least one rechargeable energy storage device (5, 8), at least one consumer (9) and at least one multi-phase converter (4) with several direct current converters (4_1, 4_2,.... 4_N) which are connected in parallel. According to the invention, the direct current converters (4_1, 4_2, 4_N) are controlled in accordance with a current operational point of the electric system (1).

Description

description

title

The invention relates to a method for the operator of an electrical system, in particular of a motor vehicle, which has at least one rechargeable energy store, at least one consumer and at least one consumer

Has multi-phase converter with at least two, in particular parallel-connected DC-DC converters.

Furthermore, the invention relates to a device for operating the electrical system described above.

State of the art

Electrical systems in motor vehicles are becoming increasingly important in the automotive industry, in particular because of the use of electric drive machines. It is of particular importance that such electrical systems generally have sections with different voltage levels. It is thus known to form the section of the electrical system which has the electric drive machine as a high-voltage section which, in comparison to that forming the vehicle electrical system

Low voltage section has a higher voltage level.

Usually, the high voltage section and the

Low-voltage section electrically connected to each other by at least one DC-DC converter, for example, to charge an energy storage of the low-voltage section by energy from the high voltage section, thereby ensuring the operation of the system as a whole. Furthermore, DC-DC converters are known, which are designed as multi-phase converters, which two or more connected in parallel

DC-DC converter, for example flyback converter or resonant converter, in order to achieve a desired performance in particular uninterrupted,

Disclosure of the invention

The inventive method with the features of claim 1 has the advantage that the DC-DC converter can be controlled individually, for example, to optimize the life of the DC-DC converter and the performance of the multi-phase converter. According to the invention, provision is made for the DC-DC converters to be activated as a function of a current operating point of the electrical system. It is thus provided that first a current operating point of the electrical system is determined in order to decide which of the

DC-DC converter how to be driven or operated. This will accomplish that, depending on the current

Operating point, the DC-DC converter can be controlled individually to ensure optimum operation.

According to a preferred embodiment of the invention, it is provided that for determining the current operating point at least one actual current, a

Operating mode of the multi-phase converter, at least one output voltage of the multi-phase converter, at least one internal controlled variable of the

Multiphase converter and / or at least one desired current of

Multiphase converter are determined. The actual current is advantageously detected directly by means of sensors of the DC-DC converter. The operating mode of the multi-phase converter results in particular from a drive strategy, for example, a lopsided or non-lopsided operation of

Specifies DC-DC converter. The internal control variables can also be detected directly by a sensor system of the respective DC-DC converter. The desired current results in particular from the control of the electrical system, in particular from a higher-level instance, such as a motor vehicle control unit or the like.

Furthermore, it is preferably provided that, depending on the current

Operating point a desired current of at least one DC-DC converter, a desired output voltage of at least one DC-DC converter and / or a module state of at least one of the DC voltage converter can be specified or varied. As a function of the determined operating point, one or more setpoint currents, setpoint output voltages and / or module states are thus varied or predetermined in order to optimize the operation of the electrical system. In particular, for example, by specifying a module state "switched on" or "switched off", the number of operating DC-DC converters during operation of the electrical system is adapted to the respective operating point. It is preferably provided that, depending on the current operating point, one or more of the

DC converter depending on their respective operating state, resulting, for example, from an operating temperature or aging phenomena are selected.

Furthermore, it is preferably provided that the desired currents or desired powers of the DC-DC converters are adjusted in dependence on the actual currents or actual powers of the individual DC-DC converters such that the actual currents / actual powers have the same current value or power value. There is thus a power equalization and / or

Power equalization of the DC-DC converter. This will be

manufacturing tolerance-related differences of the DC-DC converter with the same load, which lead to different actual currents and / or actual powers, compensated. By modifying the desired currents or desired power for different DC-DC converter is the same

Amount of electricity or amount of benefit for this

DC-DC converter achieved

According to a preferred embodiment of the invention is further provided that the DC-DC converter are de-energized to determine an electrical voltage of the at least one energy storage. Are all DC voltage converter de-energized, the

So multi-phase converter thus disabled altogether, for example by opening all semiconductor switches of the multi-phase converter, it is achieved that the electrical connection between the high-voltage section and low-voltage section is interrupted. Thus, for example, corresponds to the current voltage in the low voltage section of the (charge) voltage of the

Energy storage in the low voltage section, at least if at the Low voltage ungsabschnitt connected consumers are disabled, this deactivation can also be done by separation from the low voltage section.

According to a preferred embodiment of the invention, it is provided that for determining the current operating point current quality factors of

DC voltage converter can be determined, wherein depending on the determined quality factors the DC-DC converter controlled, in particular Betriebsbeziehungsweise module conditions are specified. Depending on the current quality factors, which give an indication of the respective operating state of the DC-DC converter, in particular the activation

or deactivation of the individual DC-DC converter performed. If a DC-DC converter should not be switched on or off by means of a regulator, but according to a predetermined time or dynamics, then this partial function preferably switches the affected one

Module / DC-DC converter or parts thereof on or off.

Furthermore, it is preferably provided that an electrical load of the electrical system, in particular of the low-voltage section of the electrical system, is determined as a function of the determined actual currents. In particular, output signals of a control complex or module of the multi-phase converter are taken into account in order to determine or at least estimate the load. In this case, the energy store is preferred

especially the low voltage section understood as another consumer of the system. Depending on the calculated set currents, the load, external specifications, in particular external setpoint voltage specifications, the estimated / determined battery voltage and optionally external current setpoints, the setpoint currents, voltages and setpoint module states are determined and controllers or hardware drivers of

Multiphase converter provided. By the presented

Operating strategy are the individual DC-DC converter

or the individual modules of the multi-phase converter evenly loaded, thereby increasing their life and switching operations are optimized. The device according to the invention with the features of claim 8 is characterized by a specially prepared control unit, which has an operating strategy module that performs the method according to the invention. This results in the already mentioned advantages, Further features and advantages will become apparent from the above-described and from the claims.

In the following, the invention will be explained in more detail with reference to the drawing. Show this

Figure 1 is a schematic representation of an electrical

System of a motor vehicle,

Figure 2 shows a structure of a control system of the electrical

Systems,

Figure 3 is a schematic representation of an advantageous

Operating strategy module of the electrical system,

FIGS. 4A to 4C schemes for current equalization,

FIG. 5 shows a method for module deactivation,

FIG. 6 shows a method for determining a setpoint voltage,

Figure 7 shows a method for determining a desired current and

FIG. 8 shows a method for determining a quality factor.

1 shows a simplified representation of an electrical system 1 of a motor vehicle not shown here. The electrical system 1 has a high voltage section 2 and a low voltage section 3, which are electrically connected together by a multi-phase converter 4. In the present case, the high-voltage section 2 comprises a rechargeable high-voltage energy store 5, an inverter 6 and an electric machine 7 which is operated by the inverter 6. The electric machine 7 can be operated by a motor or generator and is designed in particular as a drive machine of the motor vehicle. Of the

Low-voltage section 3 includes a low-voltage energy storage 8, which is also designed to be rechargeable, and one or more

Consumers 9, together form the energy store 8 and the consumer 9, the electrical system 10 of the motor vehicle,

Figure 2 shows a further illustration of the electrical system 1 with a controller complex 11, with the multi-phase converter 4, the N has parallel-connected DC-DC converter The multi-phase converter 4 has a high voltage section side input voltage U _in and a

Low voltage section side output voltage U _out , resulting from the parallel connection and the operation of the DC-DC converter 4_1, 4_2 to 4_N. By driving the DC-DC converter of

Multiphase converter 4 results in an actual voltage U _is , which is provided to the electrical system 10 available. The controller 11, a target complex stream _so l n and a target voltage U n _as well as an actual current to be supplied to the multiphase converter 4 on the high voltage side _hv l as well as the low voltage side. In particular, from this and from the actual current, the control of the multiphase converter 4 results.

FIG. 3 shows a schematic representation of an operating strategy instance, which is designed as an operating strategy module 12 of a control device of the motor vehicle. The operating strategy module 12 decides how many modules depending on a current operating point of the electrical system 1

or DC-DC converter 4_1, 4_2 ... 4_N or which parts of a module, such as a Tiefsatzsteller to be active. The operating strategy instance receives the desired voltage in the output U _SO ii as the state variable, the current currents L, run the

Low-voltage side and the high-voltage side, the operating mode of Muitiphasenswandlers 4 (lückender- or non-lopsided operation), the currently measured at the output of the multi-phase transformer 4 voltage U, _5t and internal control variables (feedforward control, adaptations and control output signal of the controller complex 11). Optionally, the operating strategy module 12 is also the target current l _! | as input value l _so n_extem and a setpoint voltage U _S0 [ _Lextem supplied. In this way, an external instance can generate a desired setpoint current for one or more of the modules or DC / DC converters 4_1, 4 2, ... _'4-n pretend. The output of the operating strategy instance represents in addition to the target currents I _SO K and voltages U _so u also provides module states M _m.

The operating strategy module 12 includes a module 13 for determining voltage, current, and module conditions, a load estimation module 14, a module state determination module 15, a current equalization module 16, and a state of charge or aging module 17 Low Voltage Energy Storage 8.

The operating strategy instance thus fulfills the following tasks in short form;

Electricity equalization / power equalization: due to the tolerance of the components, the modules can deliver different currents and / or powers under the same load. To different loads of

Modules / DC-DC converter to prevent, by modifying the target currents / target power for different modules the same

Amount of electricity / amount of benefits reached.

Battery charging voltage estimate: when the charging voltage of the

Low voltage energy storage 8 is not available, this is estimated by the module 17.

Module state determination: The current states of the modules are calculated. Depending on the detected states, these are activated or deactivated. If a module is not switched on or off by the controller, but after a given time or dynamics, then this is

Subfunction to turn on or off the affected module or parts of it.

Load Estimation: Depends on the measured currents and

Output signals of the controller complex 11, the present on-board power supply 10 is estimated.

Determination of setpoints: Depending on the calculated setpoint currents, the

Load current, external setpoint voltage specifications, estimated charging voltage and optional external current setpoint, the setpoint currents, voltages and Target module states determined and provided to controllers or hardware drivers of the multi-phase converter 4 available.

By the operating strategy instance or the operating strategy module 12, the DC-DC converter of the multi-phase converter 4 gleichmäBtg charged, optimized switching operations and the life of the electric

Systems 1 and the multi-phase converter 4 increases. In the following, the individual operating strategy will be dealt with or modules will be discussed in more detail:

If several of the DC-DC converter 4_1, 4_2, 4_N connected in parallel at the output or in a resonant converter with several

Bucks at the output, different currents can flow or achievements can be achieved due to the different component tolerances. This means that the components are loaded differently and thus age differently. To the multi-phase converter 4

To be able to load life optimally, the modules 16 equate the flows or services, in particular so that everyone

DC converter delivers, for example, 50% of its rated power. For this purpose, either the high-voltage side or low-voltage side, the actual DC currents are measured. When trained as a PSFB converter

Multiphase converter (PS FB = Phase Shifted Filled Bridge), can be influenced by driving the semiconductor switches on the high voltage side, the wetting of the converter. Therefore, if necessary, the measured currents of the low-voltage side are first converted to the high-voltage side. In a resonant converter (LLC converter), by driving the

Semiconductor switch on the low-voltage side, the behavior of the converter can be influenced. Therefore, if necessary, the measured currents are first converted from the high-voltage side to the low-voltage side. For parallel-connected DC-DC converters of the same type and

Performance class, the arithmetic mean of these currents is preferably formed and limited to a maximum allowable current and supplied as a target current to the module 13, where a further modification of the currents are performed as needed and then the controller complex 11 are provided. The task of the controller complex 11 is then by a suitable drive signal, in particular by a pulse-width modulated signal (PWM signal), to the semiconductor switches to equalize the currents or powers in particular percentage.

By equalizing the currents / powers becomes the asymmetric

Prevents load on the components and thus achieves optimum life of the multi-phase converter 4.

FIGS. 4A to 4C show different embodiments of the invention

Current equalization, Figure 4A shows a schematic representation of

Current equalization N parallel-connected DC-DC converter 4 1 to 4_W. FIG. 4B shows an exemplary embodiment for equalizing the current for two parallel-connected DC-DC converters of a PSFB converter with two current controls IC1 and IC2. FIG. 4C shows an exemplary embodiment of FIG

Current equalization for two parallel-connected DC-DC converters of a resonant converter with three buck-boosters (Bucks) and two corresponding current controllers 31C1 and 3IC2.

In the following, module 15 for module state determination will be explained in more detail. For this purpose, FIG. 5 shows in a flow diagram a method for implementing a module shutdown request. In a first step Sl, the modules of the scalable multiphase converter 4 are checked for a defect. If a defect is detected (j), the respective module is switched off in a step S2. In this case, the shutdown can be done on a vorgebare period or dynamics. If the query shows that the modules are not defective (s), it will be in one

following step S3, the magnitude of the peak power Psp is compared with a first limit value Gl. If the amount is smaller than the limit value Gl (]), then in a following step S4 the amount of the alternating power Pw is compared with a second limit value G2. If the alternating power or the amount of the alternating power is less than the second limit value D2 (j), then in a subsequent step S5, the basic power Pg with a third

Threshold G3 compared. If the basic power is less than the third limit value G3 (j), then in a step S6, the request for switching off the corresponding module or DC voltage converter, which is carried out in step S2. If one of the queries S3 to S6 yields a negative answer (s), the individual DC-DC converters are not switched off in accordance with step S7 and continue to operate. The fact that several DC-DC converters 4_1, 4_2 to 4_N are connected in parallel at the output, these can be switched off individually or turned on. How or when or which DC-DC converter should be switched on or off for the optimization of the switching losses or the life of the components, decides the operating strategy by specifying the desired current, nominal voltage and depending on the module state Mzu. The operating strategy has three manipulated variables, whereby the optimum can be influenced, namely the specification of the voltage to be set, limitation or equalization of the currents or powers and the direct shutdown of the individual modules / DC-DC converters.

Furthermore, the operating strategy has the task, a direct

Abschaltanforderung all modules to determine the battery voltage or the charging voltage of the low voltage energy storage 8 to perform.

Implementation module switch-off request: To change the charging voltage of the

To determine low-voltage energy storage 8 under load or in the zero load range, the module 17 is a shutdown of all

DC converter requested so that all the semiconductor switches of the DC-DC converter are opened simultaneously to a

To achieve power interruption. The operating strategy checks whether there is a load change. This test can be seen by the peak load or the alternating load calculated in Module 14. Is none

Load change before and the base load is less than a predetermined threshold or a predetermined limit, then all

DC-DC converter for a very short time, for example, 10 ms, switched off. A shutdown of the DC-DC converter due to the optimization takes place in the same way, unless there is a defect. In this case, the affected module is switched off immediately.

Determination of target voltage: The setpoint voltage U _so n is normally specified by an external instant (U _SO iLextem) such as a control unit or the like. In order to avoid an under- or overvoltage or a permanent charging and discharging of the low-voltage energy storage 18, the setpoint voltage U _SO ii at a load change or adjusted in the Nuiast range A zero load exists when the base load is lower than an applicable limit value. In this case, the energy store 8 is charged and the setpoint voltage can be equal to the battery voltage for

Charging voltage can be set. In the event of sudden switching on or off of large loads, overvoltages or undervoltages in the vehicle electrical system 10 can occur. Here, depending on the sign of the peak load and the currently specified external setpoint voltage U _{s0) Lextern} time the specifications for the controller complex 11 is changed. This behavior also applies to small loads, but with different parameters.

FIG. 6 shows a method for determining the setpoint voltage U _so n. For this purpose, steps S3, S4 and S5 are executed as described above. If the last condition according to step S5 is also satisfied, then in step S8 the setpoint voltage U _so n is predetermined as a function of the state of charge of the low-voltage energy storage device 8.

If the condition of step S3 is not fulfilled, the desired voltage as a function of the external reference voltage setting U _so n_ _extem or UsEx, a temporal voltage difference AU (t), and the sign of the

Peak power PSP (Sign (Psp)) determined in a step S9. Will the

Condition of step S4 not met (n), the target voltage is determined as a function of the external target voltage specification, the temporal voltage difference and the sign of the AC power Pw in a step S10.

If only the condition of step S5 is not fulfilled (n), then the externally specified setpoint voltage UsEx is determined as setpoint voltage U _so in a step S1 1.

FIG. 7 shows in a flowchart a method for determining a desired current or desired state of the individual modules of the multiphase DC-DC converter or the individual ones

DC converter. Depending on the current load PM1, PM2, the number of DC / DC converters required for operation will be

Multiphase converter 4 determined. If the current power can be provided by a single module or a single DC-DC converter, depending on a quality factor QMx, where x for the module or the respective DC-DC converter is checked, which of the modules is suitable for this purpose. The quality factor QM is a function of the active time tM, the current load and the module state. The module state is calculated in the instance or module 15. The figure of merit QM has a value between 0 and 1. "0" means that the module in question is defective and can not be used. ,, means that the module in question is ready for use and can be used, an intermediate value of, for example, less than or equal to 0.4 means that this module is too hot and should not be used In order not always to select the same module, the quality factor QM is also integrated as a function of time t.

Thus, after a predetermined time, the active module can be changed. In order not to select the module again immediately after deactivation, the time-dependent quality factor QM is again highly integrated to "1" according to a predefined function

Modul / DC converter is realized, is accordingly the

Number of modules increased. The switching on / off of the modules, if not realized via the setpoint specification of the controller complex 11, is implemented by the instance 15. This will turn on or off the affected module or parts thereof after a given time or dynamics. Switching on the non-defective modules takes place in particular non-stop.

FIG. 7 shows an embodiment of the state determination of module 15 and two DC-DC converters 4_1 and 4_2 connected in parallel. In this case, it is checked in a first step S12 whether the target power P = _υ Μ ιι x I is greater than the maximum value Pmx the current actual performance, with PX = Ps / Pmx>. 1

If this is not the case (n), it is checked whether the ratio of target power Ps to the minimum power value of the actual power Pmn <1 (step S13), with Pn = Ps / Pmn -5 1. If this is not the case ( n), the quality factor QM2 is compared with a limit value of 0.5 in a step S14. If the quality factor is less than 0.5

(n), the parallel-connected DC-DC converters 4_1 and 4_2 are activated in step S15. In the present case, at step S13, the quality factor QM1 is also compared with the limit value of 0.5 in a step S16. If the queries of step S14 and step S16 indicate that the quality factor QM1 is not greater than 0.5 and the quality factor QM2 is greater than 0.5, then in a step S17

Module 4_2 is activated and module 4_1 deactivated. Is the quality factor QM1, however greater than 0.5, the module 4_1 is activated in step S18 and the module 4_2 is deactivated.

If both modules 4_1 and 4_2 are activated according to step S15, the currents are as described above in a subsequent step S19

equal. In addition, the currents are then limited in each case in a step S20 to a maximum limit value and / or an external predetermined setpoint current.

The quality factors QM1 and QM2 result as a function of the active time of the modules 4_1 and 4_2 (tM1, 2) and of the module states (Mzu1, Mzu2).

By way of example, a multiphase converter 4 is also considered, which comprises two modules or DC-DC converters 4_1 and 4_2.

FIG. 8 shows a method for determining the quality factor QM on the basis of the quality factor QM 1 of the module 4_1. For this, the module state Mzu1, the active time tM1 and a current load I _{B are} considered. In this case, the temperature value T of the DC-DC converter 4_1 is considered as the module state Mzu1. At a temperature value of T1, it is detected that the module is hot, at a temperature value of T2 that the module is too hot and threatened with damage, and at a T3 temperature value, it is assumed that the module is defective due to overheating. Become accordingly

Quality factors of QM1 ₀ = 1, QM1 i = 0.7, QM1 ₂ = 0.4 and QM1 ₃ = 0 given by way of example. Furthermore, the quality factor QM1 decreases with active time

(solid line). The longer the module is deactivated (dashed line), the more the quality factor QM increases again. Furthermore, the quality factor QM1 decreases with increasing current load. By combining and comparing the individual parameters, the quality factor QM1 results. Accordingly, the quality factor QM2 or each quality factor of each further module or DC-DC converter 4_N is used.

When more than one DC-to-DC converter module is active, the multi-phase converter becomes the currents and / or powers of the active modules

equal to achieve the same load on the modules as mentioned earlier. The currents of all modules are at their maximum value and

if necessary, limited to the target stream of the higher-level instance. Therefor the target current of the higher-level instance is determined by the number of

DC-DC converter divided and used as a limit for the individual modules.

Claims

Method for operating an electrical system (1) of a

Motor vehicle, the at least one rechargeable energy storage (5.8), at least one consumer (9) and at least one

Multiphase converter (4) with a plurality of in particular parallel-connected DC-DC converters (4_1, 4_2, 4_N), characterized

gekennieichnet that in response to a current operating point of the electrical system (i) the DC-DC converter (4_1, 4_2, 4_N) are controlled.

A method according to claim 1, characterized in that the

Determining the current operating point at least one actual current, an operating mode of the multi-phase converter (4), at least one

Output voltage of the multi-phase converter (4), at least one internal controlled variable of the multi-phase converter (4) and or at least one desired current of the multi-phase converter (4) can be determined.

Method according to one of the preceding claims, characterized

in that, as a function of the current operating point, a nominal current of at least one of the DC-DC converters (4_1, 4 2, 4_N), a nominal output voltage of at least one DC-DC converter (4_1, 4_2, 4_N) and / or a module state of at least one

DC voltage converter (4_1, 4_2, 4_N) can be specified or varied.

Method according to one of the preceding claims, characterized

characterized in that the desired currents or soli powers of the

DC-DC converter (4_1, 4_2, .... 4_N) depending on the Iststöme or actual powers of the DC-DC converter (4_1, 4_2, .... 4_N) are adapted such that the actual currents or actual powers have the same current value or power value , Method according to one of the preceding claims, characterized in that the DC-DC converter (4_1, 4_2, 4_N) are de-energized to determine a charging voltage of the at least one energy storage device (5,8).

Method according to one of the preceding claims, characterized in that for determining the operating point a quality factor of at least one of the DC voltage converter (4_1, 4 2, 4_N) is determined, wherein depending on the determining quality factor of the

ultiphasenwandler (4) is driven.

Method according to one of the preceding claims, characterized in that, depending on the determined actual currents, an electrical load of the electrical system, in particular a

Low-voltage section of the electrical system is determined.

Device for operating an electrical system, in particular a motor vehicle, the at least one rechargeable ble energy storage (5,8), at least one electrical load (9), at least one multi-phase converter (4) with at least two parallel-connected DC-DC converters (4_1, 4_2, 4_N ), characterized by a specially prepared control unit, which has an operating strategy module (12), that performs the method according to one or more of claims 1 to 7.