阅读说明：本技术 逆变器的控制装置、车辆的逆变器、车辆及操作逆变器的方法 (Control device for inverter, inverter for vehicle, vehicle and method for operating inverter ) 是由 卡斯滕·韦德曼 蒂穆尔·维尔纳 马库斯·雷曼 于 2019-09-19 设计创作，主要内容包括：本发明涉及一种用于逆变器(1)的控制装置(2),所述逆变器包括三个半桥(9u,9v,9w),每个半桥具有连接到第一DC电压电势(10)的第一功率开关元件(11u,11v,11w)和连接到第二DC电压电势(12)的第二功率开关元件(13u,13v,13w),其中,所述控制装置(2)设置为在正常操作模式下驱动所述功率开关元件(11u,11v,11w,13u,13v,13w),以将存在于所述DC电压电势(10,12)之间的DC电压转换成多相AC电流,并且将所述逆变器(1)从正常操作模式转换到安全操作模式,其中,所述控制装置(2)还设置为在安全操作模式下交替地驱动所述功率开关元件(11u,11v,11w,13u,13v,13w),以用于切换单相主动短路和用于切换两相主动短路。(The invention relates to a control device (2) for an inverter (1) comprising three half bridges (9 u, 9v, 9 w), each having a first power switching element (11 u, 11v, 11 w) connected to a first DC voltage potential (10) and a second power switching element (13 u, 13v, 13 w) connected to a second DC voltage potential (12), wherein the control device (2) is arranged to drive the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) in a normal operation mode to convert a DC voltage present between the DC voltage potentials (10, 12) into a multiphase AC current and to convert the inverter (1) from the normal operation mode into a safety operation mode, wherein the control device (2) is further arranged to alternately drive the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) for switching a single-phase active short circuit and for switching a two-phase active short circuit.)

1. A control device (2) for an inverter (1) comprising three half bridges (9 u, 9v, 9 w), each having a first power switching element (11 u, 11v, 11 w) connected to a first DC voltage potential (10) and a second power switching element (13 u, 13v, 13 w) connected to a second DC voltage potential (12), wherein the control device (2) is arranged to drive the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) in a normal operation mode to convert a DC voltage present between the DC voltage potentials (10, 12) into a multiphase AC current and to convert the inverter (1) from a normal operation mode into a safe operation mode,

the method is characterized in that:

the control device (2) is further arranged to alternately drive the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) in a safe operation mode for switching a single-phase active short circuit and for switching a two-phase active short circuit.

2. Control device according to claim 1, further arranged to drive the respective first power switching elements (11 u, 11v, 11 w) for conduction when switching a single-phase active short circuit, and to drive the respective two first power switching elements (11 u, 11v, 11 w) for conduction when switching a two-phase active short circuit.

3. The control device according to claim 2, further adapted to not drive the first power switching element (11 u, 11v, 11 w) when switching the two-phase active short circuit, the first power switching element being driven for conduction when switching the single-phase active short circuit for conduction.

4. The control device according to any of the preceding claims, further adapted to, at the start of a safe operation mode, first drive the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) to switch a single-phase active short circuit.

5. The control device according to claim 4, further arranged to determine phase current values of a multi-phase alternating current and to select power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) for the first single-phase active short-circuiting, the half-bridges (9 u, 9v, 9 w) of the first single-phase active short-circuiting carrying the phase current which is largest in magnitude when switching to a safe operation mode.

6. A control arrangement according to any one of the preceding claims, which is further arranged to switch the single-phase active short circuit in each case for a first period of time, and to switch the two-phase active short circuit in each case for a second period of time which is different from the first period of time.

7. A control arrangement according to any one of the preceding claims, wherein the inverter (1) comprises three further half bridges, each having a first and a second power switching element, wherein the control arrangement (2) is further arranged to drive the power switching elements of the further half bridges in a safe operating mode for driving a single-phase active short circuit when the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) of the first half bridge (9 u, 9v, 9 w) are driven to switch the two-phase active short circuit, and driving a two-phase active short circuit when the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) of the first half bridge (9 u, 9v, 9 w) are driven to switch the single-phase active short circuit.

8. An inverter (1) for a vehicle (22), the inverter comprising three half bridges (9 u, 9v, 9 w), each having a first power switching element (11 u, 11v, 11 w) connected to a first DC voltage potential (10) and a second power switching element (13 u, 13v, 13 w) connected to a second DC voltage potential (12), and a control device (2) according to any one of the preceding claims.

9. A vehicle (22) comprising an electric machine (8) adapted to driving the vehicle (22), and an inverter (1) according to claim 8 adapted to powering the electric machine (8).

10. A method for operating an inverter (1) comprising three half bridges (9 u, 9v, 9 w), each half bridge having a first power switching element (11 u, 11v, 11 w) connected to a first DC potential (10) and a second power switching element (13 u, 13v, 13 w) connected to a second DC potential (12), the method comprising the steps of:

driving the power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w) in a normal operation mode to convert a DC voltage present between the DC potentials (10, 12) into a multi-phase AC current;

-switching the inverter (1) from a normal operation mode to a safe operation mode; and

in the safety operating mode, the single-phase active short circuit and the two-phase active short circuit are alternately switched by means of power switching elements (11 u, 11v, 11w, 13u, 13v, 13 w).

Technical Field

The invention relates to a control arrangement for an inverter comprising three half bridges, each having a first power switching element connected to a first DC voltage potential and a second power switching element connected to a second DC voltage potential, the control arrangement being arranged to drive the power switching elements in a normal operating mode to convert a DC voltage present between the DC voltage potentials into a multiphase AC current and to switch the inverter from the normal operating mode into a safe operating mode.

Furthermore, the invention relates to an inverter for a vehicle, a vehicle and a method for operating an inverter.

Background

The inverter is used to convert a DC voltage present at the DC voltage input into a multi-phase AC current. In particular, when an inverter is used to power a motor in a drive train of an electric vehicle, it is necessary to switch the inverter from the normal operation mode to the safe operation mode. This may be necessary after a power train failure or to protect the power train.

It has been proposed to implement the safe operating mode by means of freewheeling (safe pulse off-SPO) or by means of fully active short-circuiting (ASC). Depending on the method used, an undesirably high DC link voltage and/or an undesirably high phase current and/or an undesirably high braking torque caused by the energy stored in the inductor of the electric machine may occur when the inverter is switched from the normal operating mode to the safe operating mode. To counteract undesired DC link voltages or phase currents, it is known to design the components of the inverter in an excessive manner, which is not necessary for the normal operation mode, nor does it lead to an improvement in the operation performance. One example of such an oversize is the use of high temperature magnets or the use of semiconductors with higher current carrying capacity than desired. Conventional inverters are correspondingly expensive and material intensive.

It is therefore an object of the present invention to specify an improved way of achieving a safe mode of operation, whereby in particular high phase currents and high DC-link voltages are to be avoided.

Disclosure of Invention

In order to achieve this object, according to the invention, a control device of the type mentioned at the outset is provided in which: the control means is further arranged to alternately drive the power switching elements in the safe mode of operation for switching the single-phase active short circuit and for switching the two-phase active short circuit.

The invention is based on the recognition that: transient phase currents can also be generated when switching single-phase or two-phase short circuits. However, their characteristics are significantly different. The present invention takes advantage of this difference and alternately switches between a single-phase active short circuit and a two-phase active short circuit, so that the generation of high phase currents can be limited so that they are below the maximum allowable value for the operation of the inverter or the drive train including the inverter.

Advantageously, the phase current induced by the inductance of the electric machine decays rapidly during the control of the control device according to the invention without exceeding a maximum permissible value. In this way, oversizing of the inverter or components of the drive train including the inverter can be avoided. Thus, a high level of safety is achieved without expensive components, such as high temperature magnets and/or current-proof power switching elements in particular. At the same time, the alternate switching is relatively easy to implement and largely independent of the final operating state in the normal operating mode. This brings further advantages such as cost reduction, development effort, installation space (in particular for DC link capacitors), and elimination of the use of complex components and long service life and robustness of the drive train.

More conveniently, the power switching element comprises an Insulated Gate Bipolar Transistor (IGBT) or a power MOSFET. The first DC voltage potential and the second DC voltage potential are different. Here, the first DC potential is typically lower than the second DC potential. However, the first DC potential may also be higher than the second DC potential. Preferably, the control device is further arranged to switch the inverter from the normal operation mode to the safe operation mode when the control device receives a control signal indicating the switching, in particular from an external control device.

Preferably, the control device according to the invention is further arranged to control one first power switching element for conduction in each case when switching a single-phase active short circuit and two first power switching elements for conduction in each case when switching a two-phase active short circuit. As a result, both single-phase and two-phase short-circuiting is performed by the power switching elements connected to the same DC potential. It may also be provided that the control means is arranged such that the first power switching element, which is controlled to be conductive when switching a single-phase active short circuit, is not controlled to be conductive when switching a two-phase active short circuit.

In general, power switching elements that are not controlled to be on are controlled to be off.

Advantageously, the control device according to the invention may also be arranged to trigger the power switching element first to switch the single-phase active short circuit at the start of the safe operating mode. This enables the energy stored in the windings of the electric machine to decay particularly quickly at the beginning of the safe operating mode.

In this context, it is particularly preferred that the control device is further arranged to determine phase current values of the multi-phase alternating current and to select the power switching element for a first single-phase active short-circuit, the half-bridge of which carries the phase current which is largest in magnitude when switching to the safe operating mode. It is therefore advantageous to first convert the electrical energy of the phase with the phase current that is greatest in terms of magnitude when the safety state is requested.

According to a particular embodiment, the control device according to the invention is further arranged to switch the single-phase active short circuit in each case for a first period of time and to switch the two-phase active short circuit in each case for a second period of time which is different from the first period of time. Particularly preferably, the first time period or the second time period is at most 45%, particularly preferably at most 40%, of the sum of the first time period and the second time period. This allows the control device to be flexibly adapted to the design characteristics of the inverter and/or the electric machine.

Alternatively or additionally, it may be provided that the inverter has three further half-bridges, each further half-bridge having a first power switching element and a second power switching element, the control means being further arranged to drive the power switching elements of the further half-bridges in a safe operating mode for switching the single-phase active short-circuit when the power switching elements of the first half-bridge are controlled to switch the single-phase active short-circuit and for switching the two-phase active short-circuit when the power switching elements of the first half-bridge are controlled to switch the single-phase active short-circuit. In the case of a six-phase or multi-phase alternating current, the current flow can thus be distributed in a particularly balanced manner in the safe operating mode.

The invention further relates to an inverter for a vehicle, comprising three half bridges, each having a first power switching element connected to a first DC voltage potential and a second power switching element connected to a second DC voltage potential, and a control device according to the invention.

The invention also relates to a vehicle comprising an electric machine adapted to drive the vehicle, and an inverter according to the invention adapted to power the electric machine.

Finally, the invention also relates to a method for operating an inverter comprising three half bridges, each half bridge having a first power switching element connected to a first DC potential and a second power switching element connected to a second DC potential, the method comprising the steps of:

driving the power switching element in a normal operation mode to convert a DC voltage existing between DC potentials into a multi-phase AC current;

converting the inverter from a normal operation mode to a safe operation mode; and

in the safe operation mode, the single-phase active short circuit and the two-phase active short circuit are alternately switched by means of the power switching element.

Drawings

All embodiments relating to the control device of the invention can be similarly applied to the inverter of the invention, the vehicle of the invention and the method of the invention, so that the above-mentioned advantages can also be achieved.

Further advantages and details of the invention will become apparent from the embodiments described below and from the drawings. The figures are schematic representations and show:

fig. 1 is a circuit diagram of an inverter according to a first embodiment of the invention and a control device according to an embodiment of the invention;

FIG. 2 is a graph of pulses over time driving the power switching elements of the inverter shown in FIG. 1;

FIG. 3 is a graph of phase current and torque during operation of the inverter shown in FIG. 1;

FIG. 4 is a trace of phase current in dq coordinates during operation of the inverter shown in FIG. 1;

FIG. 5 is a graph of phase current and torque during operation of a prior art inverter;

FIG. 6 is a trace of space vector current during operation of a prior art inverter; and is

Fig. 7 is a schematic block diagram of a vehicle according to an embodiment of the invention.

Detailed Description

Fig. 1 is a circuit diagram of an inverter 1 according to an embodiment of the present invention and a control device 2 according to an embodiment of the present invention.

Furthermore, the inverter 1 comprises a DC voltage input 3, an AC voltage output 4, a power unit 5 and a DC link capacitor 6 connected in parallel with the DC voltage input 3. The inverter 1 converts a voltage U, which is applied to the DC voltage input 3 and is provided by the high voltage battery 7, into a multi-phase AC current (in this case a three-phase AC current) provided at the AC current output 4. An electric machine 8, here in the form of a permanently excited synchronous machine for example, is connected to the AC output 4.

The power unit 5 comprises three half-bridges 9u, 9v, 9w, each formed by a series connection of a first power switching element 11u, 11v, 11w and a second power switching element 13u, 13v, 13 w. The first power switching elements 11u, 11v, 11w are connected to a first DC voltage potential 10 of the DC voltage input 3, the second power switching elements 13u, 13v, 13w are connected to a second DC voltage potential 12 of the DC voltage input 3. Exemplarily, in fig. 1, the first DC potential 10 is a potential provided for connection to the negative terminal of the high voltage battery 7, and the second DC potential 12 is a potential provided for connection to the positive terminal of the high voltage battery 7. However, the second DC voltage potential and the second power switching element may also provide potentials for connection to the negative terminal and the power switching element connected thereto, respectively, and the first DC voltage potential and the first power switching element may provide potentials for connection to the positive terminal and the power switching element connected thereto, respectively, without any further modification or limitation.

Each of the power switching element elements 11u, 11v, 11w, 13u, 13v, 13w includes an Insulated Gate Bipolar Transistor (IGBT) 14 and a flywheel diode 15 connected in parallel thereto. Alternatively, the respective power switching elements 11u, 11v, 11w, 13u, 13v, 13w may be implemented by power MOSFETs. The center attack 16 of the respective half-bridge 11u, 11v, 11w is connected to the AC output 4, where the phase current I of the multiphase AC current is supplied to the motor 8 at the AC output 4_u、I_v、I_w。

The control means 2 are arranged to control the power switching elements 11U, 11v, 11w, 13U, 13v, 13w in a normal operation mode for converting a DC voltage U applied to the DC voltage input 3 into a multi-phase AC current applied to the AC current output 4. For driving, the control device 2 is connected to the control inputs 17 of the respective power switching element elements 11u, 11v, 11w, 13u, 13v, 13 w.

When the external control device 18 detects a fault condition, a transition of the inverter 1 from the normal operation mode to the safe operation mode is initiated. The control means are arranged to alternately activate the power switching elements 11u, 11v, 11w, 13u, 13v, 13w in the safety mode of operation for switching a single-phase active short circuit and for switching a two-phase active short circuit. The switching strategy is applied by the control device as soon as the control device receives a signal 19 from the external control device 18 indicating a switch to the safe operating mode.

The single-phase active short circuit is generally characterized in that the first power switching element 11u, 11v, 11w or the second power switching element 13u, 13v, 13w is driven to be conductive, while all the other power switching elements 11u, 11v, 11w, 13u, 13v, 13w are driven to be blocking. In contrast, in a two-phase active short circuit, normally two first power switching elements 11u, 11v, 11w or two second power switching elements 13u, 13v, 13w are driven to be conductive, while all remaining power switching elements 11u, 11v, 11w, 13u, 13v, 13w are driven to be blocking.

Fig. 2 is a pulse diagram of the power switching elements 11u, 11v, 11w, 13u, 13v, and 13w driving the inverter 1 with time t. Here, the pulse waveform 20u is assigned to the first power switching element 11u, the pulse waveform 20v is assigned to the first power switching element 11v, and the pulse waveform 20w is assigned to the first power switching element 11 w. Similarly, a pulse waveform 21u is associated with the second power switching element 13u, a pulse waveform 20v is associated with the second power switching element 21v, and a pulse waveform 21w is associated with the second power switching element 13 w.

At time t₀The control device 2 receives the signal 19 and terminates it at the time t < t₀The normal operating mode shown. The control unit 2 first determines at the instant t the setpoint value specified for the normal operating mode₀Which phase current I_u、I_v、I_wThe maximum in terms of amplitude. In the present case, this is the phase current I_w(see figure) 3. By means of the half-bridge 9w assigned to the phase current, the single-phase active short circuit is first of all at the time t₀And time t₁To switch between the first time periods. For this purpose, the control device 2 controls the first power switching element 11w for conduction and the further power switching elements 11u, 11v, 13u, 13v, 13w for blocking.

Then, at time t₁And time t₂In between, the control device 2 controls the other two first power switching elements 11u, 11v to be conductive and the remaining power switching elements 11w, 13u, 13v, 13b to be blocking. The pulse sequence being at time t₂And then continues periodically.

Fig. 3 shows the phase currents I of the electric machine 8_u、I_v、I_wAnd the torque M over time t, whereby the time axis in fig. 3 is compressed by a factor of 10 compared to the time axis in fig. 2. Fig. 2 thus shows the pulse diagram over a duration of approximately 1ms, while fig. 3 shows the curve over a duration of approximately 10 ms. The current and torque values shown are generated by a purely exemplary configuration.

It is evident that the above-described switching strategy leads to phase currents I_u、I_v、I_wThereby avoiding harmful current peaks. It can also be seen from the curve for the torque M that the torque M is at the time t₀The forward rapid decrease to a value of about 0 Nm and only negligible braking torque occurs.

FIG. 4 shows phase current I_u、I_v、I_wSpace vector current I generated by dq conversion_d、I_qThe trajectory of (2). Obviously, the space vector current I_d、I_qDirected on a very direct path close to the zero vector to achieve the safe state.

For comparison, FIG. 5 shows phase current I_u、I_v、I_wAnd torque M versus time t, fig. 6 shows the space vector current I in the case where a complete, i.e. triple, active short is switched instead of alternating between a single-phase active short and a two-phase active short as known in the prior art_d、I_qTrajectory in dq coordinates. Obviously, this results in phase currents I_u、I_v、I_wConsiderable overshoot and undesirable torque variations. The trajectory curve also shows the space vector current I_d、I_qThe steady state with the q-component close to zero is approached only in a damped oscillatory manner.

Although in the embodiment example described above the time periods during which the single-phase active short or the two-phase active short is switched are substantially equal in length, in other embodiment examples the ratio of the time periods may be different, for example 60: 40 in the first step.

According to another embodiment, the inverter 1 shown in fig. 1 has a total of six half-bridges for supplying the motor 8 with six-phase alternating current, in which case the first three half-bridges 9u, 9v, 9w are controlled in a safe operating mode as described before, and the other three half-bridges (not shown) are controlled differently in such a way that first the two-phase active short circuit is switched and then the single-phase active short circuit is switched. The switching strategy between the first half-bridge 9u, 9v, 9w and the other three half-bridges is thus in the opposite direction.

Fig. 7 is a schematic sketch of an embodiment of a vehicle 22, which vehicle 22, like in fig. 1, comprises an inverter 1 according to any of the embodiments described above, an electric machine 8, a high-voltage battery 7 and a control unit 18, which control unit 18, as a higher-level control unit, provides a signal 19 for activating a safe operating mode.