JP2011250558A - Leakage detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To normally perform leakage detection in an electric vehicle in which control for varying carrier frequencies is performed to reduce operating noise of an inverter.SOLUTION: In a normal state, an inverter control unit 280 applies a random carrier for varying carrier frequencies to operate inverters 210 and 220. When leakage detection is performed, a control circuit 310 gives an instruction to the inverter control unit 280 so that the carrier frequencies of the inverters 210 and 220 are fixed. When a predetermined period of time passes after the previous leakage detection, the control circuit 310 determines whether noise generated by a vehicle is small, or the vehicle is in a state where a user can easily hear the operating noise of the inverters 210 and 220. When the noise generated by the vehicle is not small, a leakage detection device 300 performs leakage detection.

Description

  The present invention relates to a leakage detection device, and more particularly to a leakage detection device mounted on an electric vehicle.

  There is known a leakage detection device for detecting a decrease in insulation resistance provided between a high-voltage power source mounted on an electric vehicle and the vehicle body. For example, Japanese Patent Laid-Open No. 2003-219551 (Patent Document 1) discloses leakage detection used in a vehicle equipped with a drive system that converts DC power from a battery into a three-phase AC voltage suitable for driving a motor using an inverter circuit. The configuration of the device is described.

  In an inverter circuit used for controlling a driving motor as described in Patent Document 1, pulse width modulation control (PWM control) is generally applied. Further, since a relatively large current is used in the drive motor, there is a possibility that the operation sound due to switching of the inverter is perceived by the user as noise.

  Japanese Patent Laying-Open No. 2007-020320 (Patent Document 2) describes that the carrier frequency is changed in order to make it difficult for the user to hear the operation sound of the inverter. According to Patent Document 2, the carrier frequency that determines the frequency of the PWM pulse is changed periodically or randomly within a predetermined frequency range around an arbitrary carrier frequency. Further, Patent Document 2 describes that the fluctuation range of the carrier frequency is changed from an electric motor current value or a frequency command value.

JP 2003-219551 A JP 2007-020320 A

  As shown in Patent Document 1, the leakage detection device generates a voltage pulse signal having a predetermined frequency that is applied to the insulation resistance via a coupling capacitor. Then, a decrease in leakage resistance is detected depending on whether or not the amplitude of the voltage pulse signal decreases at the connection point with the coupling capacitor.

  Therefore, when the control for changing the carrier frequency of the inverter as described in Patent Document 2 and the leakage detection by the leakage detection device described in Patent Document 1 are performed simultaneously, the change in the carrier frequency is: There is concern about the influence on the voltage pulse signal of the leakage detector. In particular, there is a concern that a decrease in insulation resistance cannot be detected, or that a decrease is erroneously detected, that is, leakage detection cannot be performed normally.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an electric leakage in an electric vehicle to which control for changing the carrier frequency is applied in order to reduce the operating noise of the inverter. It is to perform detection normally.

  According to the present invention, a leakage detection device mounted on an electric vehicle including a plurality of inverters includes a coupling capacitor, a detection resistor connected in series with an insulation resistance of the electric vehicle via the coupling capacitor, Pulse generation means, voltage detection means, and control means for controlling execution of leakage detection are provided. The pulse generation means applies a pulse signal having a predetermined frequency to a series circuit including an insulation resistance, a coupling capacitor, and a detection resistance when executing leakage detection. The voltage detection means detects a connection point voltage between the coupling capacitor and the detection resistor. The control means includes means for determining whether or not the vehicle state requires carrier frequency control for varying each carrier frequency in order to reduce operating noise of a plurality of inverters, and a vehicle that does not require carrier frequency control. Based on the voltage component of the predetermined frequency of the connection point voltage when issuing an instruction to fix the carrier frequency to each inverter and executing leakage detection when it is determined to be in the state and executing leakage detection Means for determining whether or not the insulation resistance is reduced.

  According to the present invention, in an electric vehicle to which control for changing the carrier frequency for reducing the operating noise of the inverter is applied, the leakage detection can be normally executed without providing a special configuration in the leakage detection device. .

1 is a schematic configuration diagram of a hybrid vehicle shown as an example of an electric vehicle on which a leakage detection device according to an embodiment of the present invention is mounted. FIG. 2 is a collinear diagram showing a relationship of rotational speed between an engine and a motor generator in the hybrid vehicle of FIG. 1. It is a block diagram which shows the structure of the high voltage electric system in the hybrid vehicle of FIG. It is a conceptual diagram explaining the carrier frequency control in each inverter. It is a conceptual diagram explaining the effect by the carrier frequency control shown in FIG. It is a flowchart explaining the leak detection operation | movement by the leak detection apparatus by embodiment of this invention.

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

FIG. 1 is a schematic configuration diagram of a hybrid vehicle shown as an example of an electric vehicle on which a leakage detection device according to an embodiment of the present invention is mounted. The electric vehicle is a generic term for vehicles including a vehicle driving force generation source (typically a motor) using electric energy, such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle.

  Referring to FIG. 1, a hybrid vehicle includes an engine 100, a first motor generator 110 (hereinafter also simply referred to as “MG1”), a second motor generator 120 (hereinafter also simply referred to as “MG2”), and power. A split mechanism 130, a speed reducer 140, and a battery 150 are provided.

  The hybrid vehicle shown in FIG. 1 travels by driving force from at least one of engine 100 and MG2. Engine 100, MG1 and MG2 are connected via power split device 130. The power generated by the engine 100 is divided into two paths by the power split mechanism 130. One is a path for driving the front wheels 190 via the speed reducer 140. The other is a path for driving MG1 to generate power.

  Each of MG1 and MG2 is typically a three-phase AC rotating electric machine. MG1 generates power using the power of engine 100 divided by power split device 130. The electric power generated by MG1 is selectively used according to the running state of the vehicle and the SOC (State Of Charge) of battery 150. For example, during normal travel, the electric power generated by MG1 becomes the electric power for driving MG2 as it is. On the other hand, when the SOC of battery 150 is lower than a predetermined value, the electric power generated by MG1 is converted from AC to DC by an inverter described later. Thereafter, the voltage is adjusted by a converter described later and stored in the battery 150.

  When MG1 is acting as a generator, MG1 generates a negative torque. Here, the negative torque means a torque that becomes a load on engine 100. When MG1 receives power supply and acts as a motor, MG1 generates a positive torque. Here, the positive torque means a torque that does not become a load on the engine 100, that is, a torque that assists the rotation of the engine 100. The same applies to MG2.

  MG2 is typically a three-phase AC rotating electric machine. MG2 is driven by at least one of the electric power stored in battery 150 and the electric power generated by MG1.

  The driving force of MG2 is transmitted to the front wheels 190 via the speed reducer 140. Thereby, MG2 assists engine 100 or causes the vehicle to travel by the driving force from MG2. The rear wheels may be driven instead of or in addition to the front wheels 190.

  During regenerative braking of the hybrid vehicle, MG2 is driven by the front wheels 190 via the speed reducer 140, and MG2 operates as a generator. Thus, MG2 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by MG2 is stored in battery 150.

  Power split device 130 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate. The sun gear is connected to the rotation shaft of MG1. The carrier is connected to the crankshaft of engine 100. The ring gear is connected to the rotation shaft of MG 2 and the speed reducer 140.

  Engine 100, MG1 and MG2 are connected via power split mechanism 130 made of planetary gears, so that the rotational speeds of engine 100, MG1 and MG2 are connected in a straight line in the collinear diagram as shown in FIG. It becomes a relationship.

  Returning to FIG. 1, the battery 150 is an assembled battery including a plurality of secondary battery cells. The voltage of the battery 150 is about 200V, for example. Battery 150 may be charged by electric power supplied from an external power source of the vehicle in addition to electric power generated by MG1 and MG2.

  Engine 100, MG1 and MG2 are controlled by an ECU (Electronic Control Unit) 170. ECU 170 may be divided into a plurality of ECUs.

  ECU 170 is composed of a CPU (Central Processing Unit) (not shown) and an electronic control unit having a built-in memory, and performs arithmetic processing using detection values from each sensor based on a map and a program stored in the memory. Composed. Alternatively, at least a part of the ECU may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  Hybrid vehicle 5 shown in FIG. 1 has an electric system that drives motor generators MG1 and MG2 by the electric power of battery 150. Since the battery 150 used for driving the motor has a high voltage of about 200 V, it needs to be sufficiently insulated from other electric systems. In the unlikely event that the insulation resistance with respect to the ground (vehicle body) decreases, it is important for safety to reliably detect the occurrence of electric leakage.

  FIG. 3 is a block diagram showing a configuration of a high-voltage electric system in the hybrid vehicle of FIG.

  Referring to FIG. 3, high voltage circuit system 200 is connected to battery 150. High voltage circuit system 200 includes a converter 205, inverters 210 and 220 for rotationally driving MG1 and MG2, respectively, and an inverter control unit 280 for controlling operations of inverters 210 and 220. Inverter control unit 280 corresponds to a functional part related to inverter control in ECU 170 shown in FIG.

  Converter 205 performs DC voltage conversion on output voltage Vb of battery 150 and outputs DC voltage VH by a switching operation by a built-in power semiconductor switching element (not shown). Converter 205 controls DC voltage VH according to the voltage command value. Inverters 210 and 220 convert DC voltage VH from converter 205 into an AC voltage and supply it to MG1 and MG2 by a switching operation by a built-in power semiconductor switching element (not shown). At this time, MG1 and MG2 output a positive torque.

  On the other hand, when MG1 and MG2 output negative torque to generate electric power, inverters 210 and 220 convert the AC voltage generated by MG1 and MG2 into a DC voltage and output it to converter 205. Converter 205 charges battery 150 with the DC voltage from inverters 210 and 220 by DC voltage conversion through control of DC voltage VH.

  Leakage detection device 300 detects a decrease in insulation resistance Ri with respect to ground 30 of battery 150 and high-voltage circuit system 200. The ground 30 corresponds to the vehicle body of the hybrid vehicle 5. As illustrated in FIG. 3, the insulation resistance Ri is equivalently indicated by a resistance value between the negative electrode of the battery 150 (corresponding to the ground of the high-voltage circuit system 200) and the earth (vehicle body) 30. A common mode capacitor (not shown) may be disposed between the ground 30 and the ground of the high-voltage circuit system 200, that is, in parallel with the insulation resistance Ri in FIG.

  Leakage detection device 300 includes a control circuit 310, a voltage detector 320, a pulse generator 360, a detection resistor 370, a coupling capacitor 380, a bandpass filter 390, and overvoltage protection diodes 391 and 392. .

  The pulse generator 360 generates a pulse signal 365 having a predetermined frequency (predetermined period Tp). The detection resistor 370 is connected between the pulse generator 360 and the node N1. Coupling capacitor 380 is connected between battery 150 that is a leakage detection target and node N1. Bandpass filter 390 is connected between nodes N1 and N2. The passband frequency of the bandpass filter 390 is designed according to the frequency of the pulse signal 365.

  Overvoltage protection diodes 391 and 392 connected to node N2 remove surge voltage (high voltage, negative voltage). The voltage detector 320 detects the voltage at the node N2 at a predetermined sampling period Ts. In order to detect a periodic voltage change at the node N2 in response to the pulse signal 365, the sampling period Ts of the voltage detector 320 is set sufficiently shorter than the period Tp of the pulse signal 365. Thereby, the maximum voltage (peak voltage), minimum voltage, etc. within the pulse voltage period corresponding to the pulse signal period can be detected. Note that the maximum voltage (peak voltage) is set by inputting the pulse signal 365 from the pulse generator 360 to the voltage detector 320 and setting the voltage sampling timing of the node N2 in consideration of synchronization with the pulse signal 365. A minimum voltage or the like may be detected.

Next, the operation of leakage detection device 300 will be described.
When the leakage detection is performed by the leakage detection device 300, the pulse generator 360 generates a pulse signal 365. The generated pulse signal 365 is applied to a series circuit including a detection resistor 370, a coupling capacitor 380, and an insulation resistor Ri. As a result, the node N1 corresponding to the connection point of the detection resistor 370 and the coupling capacitor 380 has a voltage dividing ratio of the insulation resistance Ri and the detection resistor 370 (resistance value Rd): Ri / (Rd + Ri) and the amplitude of the pulse signal 365 ( A pulse voltage having a peak value as a product of the power supply voltage + B) is generated. That is, when the insulation resistance Ri decreases, the amplitude of the pulse voltage at the node N1 decreases.

  The pulse voltage generated at the node N1 is attenuated by components other than the frequency of the pulse signal 365 by the band-pass filter 390, the surge voltage is removed by the overvoltage protection diodes 391 and 392, and transmitted to the node N2.

  The control circuit 310 detects a decrease in the insulation resistance Ri based on the voltage at the node N2 detected by the voltage detector 320 according to the sampling period Ts. Specifically, when the voltage at the node N2 is lower than the determination value, a decrease in insulation resistance, that is, a leakage is detected. The operation of the control circuit 310 is generally processed in software by a microcomputer or the like. Therefore, the control circuit 310 can be realized as a function of an electronic control unit (ECU).

Next, control of the inverters 210 and 220 will be described.
MG1 and MG2 are provided with a position sensor 230 that detects the rotational phase of the rotor and a current sensor 240 that detects each phase current.

  Inverter control unit 280 controls the switching operation in inverters 210 and 220 so that MG1 and MG2 are rotationally driven according to the command values (torque and rotational speed) based on the detection values of position sensor 230 and current sensor 240. .

  As the inverters 210 and 220, a general three-phase inverter configured using a power semiconductor switching element can be applied, and the detailed configuration thereof will not be described. Generally, pulse width modulation (PWM) control is applied to switching control in such an inverter.

  In the PWM control, on / off of the power semiconductor switching element of the inverter is controlled according to a voltage comparison between a carrier signal using a triangular wave or a sawtooth wave and a sinusoidal AC voltage command value. By this on / off control, a pseudo AC voltage composed of a set of square wave output voltages whose pulse widths are controlled is applied from the inverters 210 and 220 to the MG1 and MG2.

  Therefore, in inverters 210 and 220, the power semiconductor switching element is turned on / off at the frequency of the carrier signal (hereinafter also referred to as “carrier frequency”). Therefore, electromagnetic noise at the carrier frequency may be generated and detected as noise by the user of the hybrid vehicle 5. Therefore, the inverters 210 and 220 execute carrier frequency control for noise suppression as described below.

FIG. 4 shows carrier frequency control in each of the inverters 210 and 220.
Referring to FIG. 4, carrier frequency f1 of inverter 210 is changed periodically or randomly according to the passage of time according to a predetermined pattern within a predetermined frequency range. The center value of the frequency range is predetermined fa, the upper limit value (f1max) is fa + Δfa, and the lower limit value (f1min) is fa−Δfa.

  Similarly, the carrier frequency f2 of the inverter 210 is changed periodically or randomly according to the passage of time according to a predetermined pattern within a predetermined frequency range. The center value of the frequency range is predetermined fb, the upper limit (f2max) is fb + Δfb, and the lower limit (f2min) is fb−Δfb. Note that fa and fb are predetermined different frequencies.

  Referring to FIG. 5, reference numeral 400 indicates a frequency distribution of sound pressure levels when the carrier frequency is fixed to f1 = fa (or f2 = fb). In this case, since the sound pressure level of the fixed frequency corresponding to the frequency fa (or fb) is increased, the operation sound of the frequency is easily detected by the user.

  On the other hand, reference numeral 410 denotes the frequency distribution of the sound pressure level when the carrier frequency f1 (f2) is varied in the frequency range from the lower limit value f1min (f2min) to the upper limit value f1max (f2max) as shown in FIG. is there. By shortening the period for changing the carrier frequency (for example, about 2 to 10 [ms]), the human auditory perception recognizes the sound as a uniform intensity in the frequency range.

  As a result, as indicated by reference numeral 410, the sound pressure level can be dispersed within the frequency region, so that the sound pressure level of the operating sound can be reduced.

  However, with the operation of the inverters 210 and 220, a switching noise signal having a frequency fc represented by the following equation (1) corresponding to the difference between the carrier frequencies is generated. In Expression (1), m and n are natural numbers.

fc = | f1 × m−f2 × n | (1)
Here, when the frequency fc becomes close to the frequency of the pulse signal 365 of the leakage detection device 300, the leakage detection by the leakage detection device 300 may not be normally performed due to the influence of switching noise of the frequency fc. For this reason, the leakage detection device according to the embodiment of the present invention controls the execution timing of leakage detection as follows.

  FIG. 6 is a flowchart showing a processing procedure of a leakage detection operation by the leakage detection apparatus according to the embodiment of the present invention. The processing procedure according to the flowchart shown in FIG. 6 is executed by the control circuit 310 at a predetermined cycle.

  Referring to FIG. 6, control circuit 310 counts the elapsed time from the previous execution of leakage detection in step S100. In step S110, the control circuit 310 determines whether the elapsed time counted in step S100 exceeds a predetermined value T0.

  When the elapsed time exceeds T0 (when YES is determined in S110), the control circuit 310 advances the process to step S120 to mean the generated sound of the hybrid vehicle 5 (generated sound other than the inverter operating sound). The same shall apply hereinafter) to determine whether the vehicle state is small. The determination at step S120 can be executed based on, for example, the rotational speeds of engine 100, MG1, and MG2. That is, when the rotational speed of any one of these elements is high, it is determined that the vehicle is in a state where it is difficult for the user to detect the operation sound due to the carrier signals of the inverters 210 and 220 by these generated sounds.

  The control circuit 310 proceeds to step S130 to stop the leakage detection when the vehicle state is low in generated sound (YES in S120). In step S140, control circuit 310 instructs inverter control unit 280 to execute a random carrier whose carrier frequency is changed by the carrier frequency control shown in FIG. Thereby, inverter control part 280 controls inverters 210 and 220, after reducing an operation sound by execution of a random carrier.

  That is, when the generated sound of the vehicle is small, the operating sound in the inverters 210 and 220 is easy to be detected by the user, and therefore the operating noise reduction due to the execution of the random carrier has priority. In order to prevent erroneous detection of leakage, leakage detection is stopped.

  On the other hand, control circuit 310 executes steps S150 and S160 in order to execute leakage detection at this opportunity when the generated sound is not in a low vehicle state (NO in S120). In step S150, control circuit 310 instructs inverter control unit 280 to control inverters 210 and 220 while fixing the carrier frequency. Thereby, the carrier frequencies in inverters 210 and 220 are fixed to the frequencies fa and fb shown in FIG. The frequencies fa and fb are determined in advance so that | fa × m−fb × n | is not close to the frequency of the pulse signal 365 of the leakage detection device 300.

  Further, in step S160, control circuit 310 performs leakage detection in a state where the carrier frequencies in inverters 210 and 220 are fixed at frequencies fa and fb. When the leakage detection is performed, the pulse generator 360 generates a pulse signal 365 having a predetermined frequency as described above. Further, the voltage at node N1 (pulse voltage amplitude) to which generated pulse signal 365 is transmitted is detected by voltage detector 320 via bandpass filter 390 and node N2, thereby reducing insulation resistance Ri. It is determined whether or not.

  Note that if the elapsed time does not reach the predetermined value T0 (NO determination) in step S110, the control circuit 310 determines that leakage detection is not necessary, skips step S120, and The processes of S130 and S140 are executed. That is, priority is given to lowering the operating noise of the inverters 210 and 220 due to the execution of random carriers.

  According to the flowchart of FIG. 6, the leakage detection device 300 basically attempts to perform leakage detection every cycle T0, but avoids a situation in which the operation sound of the inverters 210 and 220 is easily perceived by the user. After the random carriers at 210 and 220 are stopped, leakage detection is executed. Thereby, it can prevent that leakage detection becomes abnormal by the switching noise signal from the inverter by a random carrier. That is, leakage detection can be performed accurately even in a hybrid vehicle in which random carriers are applied to the inverters 210 and 220.

  On the other hand, in a situation where noise is easily perceived by the user, it is possible to temporarily stop the execution of leakage detection and to suppress the operation sound by the inverters 210 and 220 by executing random carriers. Therefore, it is possible to achieve both the accurate detection of electric leakage during traveling of the vehicle and the use of the carrier frequency control (random carrier) of the inverter so that the user does not sense noise.

  In addition, when the vehicle state where the generated sound is low continues for a long period of time, there is a possibility that the chance of detecting leakage is lost for a long period of time. In order to avoid such a situation, for example, the number of times that the determination in step S120 is NO is separately counted, and if this count exceeds a predetermined value, the determination in step S120 is forcibly set to YES. It may be determined. If it does in this way, it will become possible to ensure the opportunity of a leak detection according to the minimum period larger than basic period T0.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  5 Hybrid vehicle, 30 Ground (body), 100 Engine, 110 First motor generator (MG1), 120 Second motor generator (MG2), 130 Power split mechanism, 140 Reducer, 150 Battery (high voltage power supply), 190 Front wheel, 200 High Voltage Circuit System, 205 Converter, 210, 220 Inverter, 230 Position Sensor, 240 Current Sensor, 280 Inverter Control Unit, 300 Leakage Detector, 310 Control Circuit (ECU), 320 Voltage Detector, 360 Pulse Generator, 365 Pulse Signal, 370 detection resistor, 380 coupling capacitor, 390 bandpass filter, 391, 392 overvoltage protection diode, MG1, MG2 motor generator, N1, N2 node, Ri insulation resistance, T0 predetermined value (leakage detection) This cycle), VH DC voltage, Vb output voltage (battery), f1min, f2min lower limit, f1max, f2max upper limit, f1, f2 carrier frequency.

Claims (1)

An electric leakage detection device mounted on an electric vehicle including a plurality of inverters,
A coupling capacitor;
A detection resistor connected in series with an insulation resistance of the electric vehicle via the coupling capacitor;
A pulse generating means for applying a pulse signal having a predetermined frequency to a series circuit including the insulation resistance, the coupling capacitor, and the detection resistance when performing leakage detection;
Voltage detection means for detecting a connection point voltage of the coupling capacitor and the detection resistor;
Control means for controlling execution of the leakage detection,
The control means includes
Means for determining whether or not it is a vehicle state that requires carrier frequency control to vary each carrier frequency in order to reduce operating noise of the plurality of inverters;
Means for issuing an instruction to fix the carrier frequency to each of the inverters and executing the leakage detection when it is determined that the vehicle state does not require the carrier frequency control;
And means for determining whether or not the insulation resistance is lowered based on a voltage component of the predetermined frequency of the connection point voltage when the leakage detection is performed.

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