WO2008135327A1 - Error correction in an electrical machine of a hybrid drive - Google Patents

Abstract

The invention relates to a method for correcting errors in an electrical machine of a hybrid drive, comprising the following steps: detection of whether at least one operation parameter of the electrical machine exceeds an assigned operation parameter threshold; activation of a power supply connection of the electrical machine for a time interval assigned to the operation parameter, following detection of the at least one operation parameter which exceeds the assigned operation parameter threshold; and bypassing of the power supply connection to earth at the end of the time interval. The invention further relates to a monitor circuit for carrying out the method. The monitor circuit is provided for an electrical machine of a hybrid drive and comprises an override output, a bypass output, a timer circuit, and at least one detection input for at least one operation parameter. The monitor circuit is set up to send out an override signal via the override output when a threshold value assigned to the at least one operation parameter is exceeded. The timer circuit provides a time interval for each of the at least one operation parameters, wherein the time interval begins when the threshold value is exceeded. At the end of the time interval, the bypass output sends out a bypass signal.

Description

 description

title

Error treatment in an electric machine of a hybrid drive

State of the art

The invention is based on hybrid vehicles with synchronous electric motor. In order to avoid permanent damage to the vehicle and the synchronous motor, the operation of the synchronous motor is monitored and shorted to ground in the event of a fault. According to the prior art, therefore, upon detection of a fault, the power connection of the synchronous motor is grounded directly.

However, such an approach may result in permanent damage to the synchronous motor in some types of failure, and may also adversely affect the driving operation of the vehicle powered by the hybrid drive.

Disclosure of the invention

The invention is based on the consideration that measures taken in the event of a fault should depend on the type of fault that occurs in the electric machine of a hybrid drive. According to one aspect of the invention, when certain types of faults occur, the electrical connection of the electrical machine is not grounded directly after the fault has occurred, but is first enabled for a certain period of time, ie decoupled from the power supply, in order to interrupt the flow of current. It has been recognized that in the case of short circuiting, especially of synchronous motors, damaging current peaks can occur, which can be avoided if the power connection of the synchronous motor is first enabled before short-circuiting. Although short-circuiting to ground is mandatory to bring the electric machine, in particular a synchronous motor, to the safe state, safe operation of the hybrid drive in the event of a fault is not adversely affected if between the onset of the fault and short-circuiting to ground for a short period of time that is, for example, a few microseconds, the power connection of the synchronous motor is enabled. For detecting faults, at least one current sensor and / or at least one voltage sensor are preferably used, which measure the current flowing into the electric machine and measure the voltage applied to the power supply of the electrical machine or the electric machine itself. Preferably, the power supply is provided by a pulse inverter whose output voltage is measured.

According to a further aspect of the invention, it is checked whether the current flowing into the electrical machine exceeds a limit and / or whether the output voltage of the power supply of the electrical machine exceeds a maximum voltage, that is a limit value. According to the invention, when the current flowing into the electric machine exceeds a threshold, that is, when a phase overcurrent fault occurs, the terminal of the electric machine is released for a long time before going into the short-circuited state as compared with the case where the voltage applied to the terminals of the electric machine or to the power supply of the electric machine exceeds a threshold, that is, when an overvoltage fault occurs.

Phase overcurrent faults or overvoltage faults can occur if the power supply of the electrical machine is defective, if a fault occurs in the electrical machine, if the mechanical load at the output of the electric machine has failed

Limit exceeds or similar errors occur. If the electric machine has several phases and thus several electrical connections, then preferably each one

Monitored input for the applied voltage and the current flowing through it. If an error occurs in one phase, then preferably the entire electrical

Machine according to the method described above after a short freewheeling period on

Ground shorted.

The detection of the current or the voltage can be provided digitally or analogously, wherein, for example, a voltage sensor, in particular a direct tap of the applied voltage, is supplied to an evaluation element which outputs a signal when a limit voltage is exceeded. This can be provided for example by means of a comparator or by means of a correspondingly connected operational amplifier. The current is preferably detected by the power supply has a sense MOSFET on whose sense output from the current flowing through the power amplifier can be detected. Alternatively or in combination with this, the magnetic field generated by the current can be detected, for example by means of Hall sensors or magnetoresistive resistors for detecting the static magnetic field, or by using inductances for Detection of the dynamic magnetic field. Furthermore, shunt resistors can be used, at which a voltage drops, which is proportional to the current flowing through them. The recorded current or voltage values can be further processed in analog or digital form.

According to a preferred embodiment of the invention, the detected digital or analog values of continuous current or voltage signals from an error detection circuit are compared with a respective limit value. If the respective value exceeds the limit value, the error detection circuit preferably outputs a voltage level that differs from the voltage level that is output when the respective value is below the limit value. For example, a high level (HIGH) signal may be output when the threshold is exceeded, otherwise a low level signal such as a LOW signal is output. Such a conversion of continuous-value signals into discrete error signals facilitates further processing by means of one or more corresponding timer circuits.

In a further embodiment of the invention, the fault detection circuit is followed by a timer circuit which, depending on the error signal and its level and depending on a time constant, releases the electrical machine before it is short-circuited.

The time constant may be implemented by connecting an input of a comparator to an RC element so that a level change from 0 to 1, that is from a low level to a high level, will not affect the output of the comparator until the comparator Capacitor has a corresponding voltage level. Other implementations are LC or LR links as networks that determine the time constant, in combination with digital logic circuits in CMOS or TTL technology, such as AND, OR or XOR gates, or in the form of logic gates, the are switched as monoflop over the networks. The circuits which determine the time constant may further comprise a temperature compensation element which at least partially compensates for a dependence of the time constant on the temperature of the components used. Furthermore, elements can be provided which compensate for the dependence on the operating voltage of the circuit, for example voltage regulators. The circuit which specifies the time interval may also be predetermined by a digital circuit, for example a timer (in particular a quartz crystal) and a counter, the elapsed time or the reaching of the end of the time interval being determined by comparing the counter value with a predetermined value becomes. These circuits can be made of individual components, or it can be integrated circuits such as programmable circuits, such as ASICs or field programmable memory devices are used. As a timing generator, a flip-flop or other constant-frequency signal source may be used instead of a quartz circuit. The time interval between fault detection and short-circuiting of the electric motor thus provided is preferably a few microseconds, for example between 0.1 and 10 microseconds, preferably between 1 and 5 microseconds. Further, the time constant is preferably provided such that when a phase overcurrent fault occurs and thereafter an overvoltage fault occurs, for example, within the time interval associated with the phase overcurrent fault, then the time interval between detection of the overvoltage fault and shorting has a length corresponding to the overvoltage fault.

To implement the freewheeling and short-circuiting to ground, the electric machine is preferably connected via a power switching device to the power supply, which interrupts the current flow to the electric machine depending on freewheeling or short-circuit signals or short-circuits the current input of the electric machine, preferably to ground. Parts of the power switching device can also be implemented in the power supply, for example, as an additional emergency stop input, the output stages of the power supply decoupled from the output or sets the output of the power amplifier to ground. According to a further embodiment of the invention, the power switching device can be linked to overload fuses that protect the electrical machine.

In a further embodiment of the invention, the time intervals depend not only on the types of errors but also on further operating parameters of the hybrid drive, for example the speed of the vehicle driven by the hybrid drive, the operating mode of an internal combustion engine provided in the hybrid drive or from other safety-relevant operating parameters such as the temperature of the components of the drive. According to a further embodiment of the invention, the time interval between fault detection and short-circuiting is extended until a current present at the terminals of the electrical machine is below a limit value.

It will be apparent to those skilled in the art that the above measures may be combined to determine the time constant, and that the measures for driving and performing the short-circuiting and disconnecting the power supply may be combined.

Brief description of the drawings Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

Figure 1 is a circuit diagram of an electric drive with the monitoring circuit according to the invention and

Figure 2 shows an embodiment of the monitoring circuit according to the invention.

embodiments

In the figure 1, an electric drive is shown in the form of a circuit diagram, which implements the monitoring circuit according to the invention. The illustrated electric drive is provided to implement the method according to the invention for error treatment. The electric drive comprises a voltage source 10, which supplies a pulse inverter 12 with voltage. This generates from the input voltage a pulse width modulated output voltage, which supplies an electrical machine 30 via a network 20. The pulse inverter is controlled by a drive controller (not shown), via which the operation of the electric machine 30 is controlled. The network 20 includes a voltage sensor 40 which measures the output voltage of the pulse-controlled inverter. Alternatively or in combination with this, the pulse-controlled inverter can output via a connection 42 an internal voltage or a corresponding voltage signal which represents an internal voltage which is linked to the output voltage or the output voltage itself. The network 20 further includes a current sensor 50 which measures the phase current flowing to the electric machine 30 and outputs a corresponding current signal. For monitoring the operation of the electric machine 30, a monitoring circuit 60 according to the invention is provided which detects a voltage signal from the voltage sensor 40 and a current signal from the current sensor 50. To detect these signals, the monitoring circuit 60 has a voltage input 62 and a current input 64.

The network 20 further includes a controllable flywheel switch 70 and a controllable short-circuit switch 80. The switches may be implemented as a relay, MOSFET, IGBT or equivalent power device. The controllable freewheeling switch 70 is provided between the output of the pulse inverter and the electric machine 30 in order to interrupt the power supply to the electric machine 30 in the event of a fault. FIG. 1 shows the controllable free-wheeling switch between the current sensor 50 and the pulse-controlled inverter 12. However, this can also be connected in series between the current sensor 50 and the be switched electrical machine 30. During normal operation, the controllable free-wheeling switch 70 is closed, so that current can flow from the pulse-controlled inverter 12 to the electric machine 30. The controllable freewheeling switch 70 has a control input, with which the switching state of the controllable freewheeling switch 70 can be controlled, and which is connected to the monitoring circuit 60 via a freewheeling output 66. If the monitoring circuit detects a corresponding error, the monitoring circuit according to the method according to the invention can interrupt the current flow between the pulse-controlled inverter and the electrical machine 30 by activating the controllable freewheeling switch. Similarly, the controllable short-circuit switch 80 has an input which is connected to an output 68 of the monitoring circuit according to the invention. If the monitoring circuit detects an error, it can control the controllable short-circuit switch 80 via the short-circuit output 68 in order to short-circuit the input of the electrical machine 30. Preferably, the monitoring circuit 60 comprises a logic circuit which ensures that the short-circuiting switch 80 is short-circuited or driven only to short-circuit when the controllable freewheeling switch is open. In FIG. 1, the controllable short-circuit switch 80 is connected directly in parallel to the electrical machine 30. Alternatively, however, this can also be connected to the electric machine via the current sensor 50. In a further embodiment, the short-circuiting switch is connected directly in parallel with the output terminals of the pulse-controlled inverter.

The electric machine 30 is preferably a synchronous machine, for example a synchronous machine with a permanent magnet as the exciter, wherein, alternatively, the electric machine 30 may also be a separately excited synchronous machine, a DC motor or an asynchronous motor. The power supply 10 is preferably the clock battery of a hybrid drive and can be provided by means of high-capacity lead-acid batteries or by means of suitable equivalent electrical energy stores. Furthermore, the circuit shown in Figure 1 may comprise overload fuses. The voltage output 42 of the pulse-controlled inverter can output an internal current signal or further operating parameters in combination or alternatively to the internal voltage signal. The signals output by voltage sensor 40 and current sensor 50 may be analog voltage signals, analog current signals, or digital equivalents thereof. In a further embodiment, the current sensor 40 and / or the voltage sensor 50 can additionally comprise a comparator circuit, which compares the detected voltage or the detected current with a manipulated value and therefore outputs a signal which corresponds to the exceeding of the respective manipulated value.

The inventive concept may be provided by the monitoring circuit 60, but also by a monitoring circuit comprising a voltage sensor and / or a Current sensor comprises, wherein such a reaction may further include the controllable free-wheeling switch and / or the controllable short-circuit switch, or not. According to a further realization variant of the invention, the monitoring circuit according to the invention may also comprise the controllable pulse inverter 12 or the voltage and current sensors provided therein.

1 shows a single-phase electric drive with the monitoring circuit according to the invention in a single-phase design. Alternatively, the electric machine may also be polyphase, wherein preferably each phase has a corresponding controllable free-wheeling switch and corresponding controllable shorting switch, which are connected to one or more monitoring circuits according to the invention. In a multi-phase design with multiple monitoring circuits, these are preferably connected together to transmit error signals, such as phase overcurrent signals and / or overvoltage signals associated with one or more phases.

FIG. 2 shows a preferred embodiment of the monitoring circuit according to the invention. The monitoring circuit shown in FIG. 2 comprises an overvoltage input 110, which detects a digital level change when the voltage of the pulse-controlled inverter exceeds a threshold value. To provide a signal detectable by input 110 from the analog voltage signal, a comparator may be used which compares an analog voltage signal with a threshold, or the voltage signal may be applied directly to the input of a digital logic element due to its digital nature also has a switching threshold.

Similarly, the monitoring circuit shown in FIG. 2 comprises a phase overcurrent input 120, which also preferably receives digital signals whose levels represent a phase overcurrent error. The overvoltage input 110 is connected, via NAND logic gates, to a first comparator 130 and a first RC network 140, which together define a time constant. The overvoltage input 110 is connected to the first RC network 140 via NAND logic gates, with the NAND gates 150 providing a reset input 155 which permits the reset of the overvoltage input 110 and the comparator 130, including the first RC network 140.

The phase overcurrent 130 is connected to a second comparator 170 via a second RC network 160. Both the first comparator 130 (OPEN COLLECTOR) and also the second comparator 170 (OPEN CORRECTOR) each have at least one pull-up resistor at their outputs.

When the level of the overvoltage input 110 and / or the phase overcurrent input 130 changes, first the respective capacitance 144, 164 is charged via a respective resistor 142, 162 of the respective first and second RC network. The first RC network thus includes a first resistor 142 and a first capacitor 144, whereas the second RC network comprises a second resistor 162 and a second capacitor 164. The rate of change in level change of the respective first and second RC network is thus determined by the resistance of the respective first and second resistors 142 and 162 and the first and second capacitances 144, 146 charged by the same. The first and the second, respectively RC network is further connected to the positive input of the first and second comparators 130, 170, respectively. The first comparator 130 and the second comparator 170 are each provided with at least one pull-up resistor on the output side.

The outputs of the first and second comparators 130, 170 are combined via summing NAND gates 180. The output of the summing NAND gate is provided via a NAND gate stage to a total summing NAND gate 190, which further receives a signal from a reset conditioning gate 200. The reset conditioning gate 200 is also a NAND gate that combines the phase overcurrent signal with the input signal of the first RC network 140.

The total summing NAND gate 190 outputs a signal to drive the controllable flywheel switch. The execution of the total summation NAND gate thus corresponds to the freewheel output 66 of FIG. 1.

In FIG. 2, the freewheel signal 110 corresponds to the output of the total summation NAND gate 190 and, in the embodiment shown in FIG. 1, forms the drive signal of the controllable freewheeling switch 70, which is controlled by the output 66 of the circuit 60.

Preferably, the monitoring circuit of Figure 2 further comprises a control circuit for the controllable short-circuit switch which detects the occurrence of an overvoltage fault or a phase overcurrent error and closes the controllable short-circuit switch 80 via a control signal when at least one of these faults occurs, when the freewheel signal returns to the inactive state. The freewheel signal returns to the inactive state, if it was previously triggered by the occurrence of one of the errors and the time interval provided by the monitoring circuit, which is provided by the monitoring circuit and is triggered by the occurrence of a phase overcurrent error or an override error, expires or has expired.

The monitoring circuit of FIG. 2 preferably also comprises a separate voltage supply circuit for the NAND gates used and the first and second comparators 130, 170, which smoothes a voltage originating from a vehicle electrical system by means of smoothing devices and / or regulating devices and frees them from voltage peaks by means of filtering.

According to a further embodiment of the invention shown in Figure 2, the signal output of the NAND gate 190 is connected to a power amplifier and / or a level converter to directly control the controllable free-wheeling switch and / or the controllable shorting switch. Furthermore, the reset input 155 may not be directly connected to a reset signal, but via another RC network, preferably with corresponding comparator or NAND gate circuitry, for applying a predetermined delay to a reset signal delivered to the monitoring circuit. Furthermore, the monitoring circuit of FIG. 2 may be provided with an enable signal input which resets the entire circuit to a state which prevails during normal operation.

The circuit shown in Figure 2 can be implemented by means of discrete components or integrated circuits. Alternatively or in combination with this, a programmable component, for example an ASIC, an FPGA or a microcontroller, can implement the method according to the invention or the monitoring circuit according to the invention. If a microcontroller or a CPU is used, the monitoring circuit according to the invention preferably comprises a non-volatile memory in which software modules are provided which implement at least part of the monitoring circuit. In the case of such a digital conversion, instead of an RC element, a digital equivalent in the form of a counter and a clock generator can be used with which time intervals can be determined. In general, the time intervals can be determined by counting discrete events, energy transfer events, such as occur in charging capacitances or generating a magnetic field in a coil, and by passing digital (or analog) signals through discrete elements, such as logic gates, with their Total Chain Delay determines the time interval.

The current or voltage sensors used can also comprise analog-to-digital converters for interference-free transmission, which transmit the detected current or voltage signal in to convert a digital value. Alternatively or in combination, the Strombzw. Voltage sensors also include active amplifiers that amplify the detected signal and thus change transmission interference. The output signals of the current or voltage sensors can be analog and at least partially linear, digital in the form of binary values or in the form of pulse widths or frequency-modulated signals. The current or voltage sensors may also be identical to the current or voltage sensors of the electric machine, which are used for the exact control of the machine during normal operation. Furthermore, instead of the sensors, the current or voltage signals can also originate from the output stage, which drive the electric motor.

Claims

claims A method of error handling an electric machine (30) of a hybrid drive, comprising the steps of: detecting whether at least one operating parameter of the electric machine (30) is above an associated operating parameter limit; Enabling a supply connection of the electrical machine (30) for a time interval associated with the operating parameter after detecting that the at least one operating parameter is above the associated operating parameter limit; and Short-circuit the supply connection to ground after expiry of the time interval. 2. The method of claim 1, wherein the operating parameters include a current flowing to the supply terminal and / or an output voltage of a driving device, which is connected to the supply terminal of the electric machine (30), wherein the time interval associated with the current, independently of the time interval associated with the output voltage can be selected. 3. The method of claim 2, wherein the time interval associated with the stream is greater than the time interval associated with the output voltage. 4. The method of claim 2 or 3, wherein the power supply for the time interval associated with the voltage is interrupted before the electric machine (30) is short-circuited when the current and simultaneously or subsequently the output voltage of the respective operating parameter Limit exceeds. 5. The method according to any one of the preceding claims, wherein the electric machine (30) is a synchronous machine with excitation winding and / or with permanent magnet and the drive means comprises a pulse inverter (12) which generates the current and the output voltage. A monitoring circuit (60) for monitoring an electric machine (30) of a hybrid drive comprising a free-wheeling output (66), a short-circuit output (68), a timer circuit and at least one detection input (62; 66) for at least one operating parameter the monitoring circuit (60) is established at Violation of a limit value, which is assigned to the at least one operating parameter to output a freewheeling signal via the freewheeling output, and the timer circuit for each of the at least one operating parameter provides a time interval, which with the Violation of the limit begins and at the end of the short-circuit output (68) outputs a short-circuit signal. 7. Monitoring circuit according to claim 6, wherein the freewheel output (64) and the short-circuit output (68) are arranged to control a drive device (12) which supplies the electrical machine (30) with the power supply to the freewheel signal, the supply terminals of the electric machine (30) and with the short-circuit signal to connect the supply terminals of the electric machine (30) to ground. The monitoring circuit of claim 6 or 7, wherein the at least one operating parameter comprises a current supplied to the electric machine (30) and a voltage applied to the electric machine (30), the time interval corresponding to the current is greater than the time interval associated with the voltage. 9. A monitoring circuit according to claim 8, wherein the time interval corresponds to the time interval associated with the voltage when it is detected at the detection input that simultaneously or sequentially the current limit and then the voltage limit is exceeded. 10. The monitoring circuit of claim 6, wherein the detection input is a serial or parallel input for at least one operating parameter in digital or analog form, and the timer circuit comprises: an analog circuit with an operational amplifier. 130, 170), a comparator, and / or a monostable multivibrator, and an RC, LR, or LC network (140, 160), or a digital circuit including a timer, a counter, and a count comparator.