JP2006025493A - Power converter and its current restriction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter which can exhibit the device capacity satisfactorily, while preventing the overheat breakage of a power element due to overload. <P>SOLUTION: A controller 20 decides that a state is one of current concentration state, when the current value I from an inverter 10 exceeds threshold Ith1. Then, the controller 20 sets a current limiting time to be longer the smaller the current value I is, with the time, when the current value I exceeds Ith<SB>-</SB>max as the shortest. Moreover, the controller 20 sets the current limitation time longer the lower the cooling water temperature of the inverter 10 is. For example, when the current value I exceeds Ith<SB>-</SB>max, the controller 20 sets the current limiting time to Δt1(Tw2) to be longer than Δt1(Tw3), if the cooling water temperature is Tw2 which is lower than Tw3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power conversion device and a current limiting method thereof, and more particularly to a power conversion device and a current limiting method thereof that limit an output current during overload to prevent overheating destruction of an element.

  If a high load state continues in a power conversion device such as an inverter, the power elements constituting the power conversion device will be destroyed by overheating. Therefore, if the high load state continues for a predetermined time, the output current from the power conversion device is limited. Has been conventionally performed (for example, see Patent Document 1).

Patent Document 1 discloses a technique for protecting an inverter from an overload state. According to the technique disclosed in Patent Document 1, it is determined whether or not an overload current is flowing by detecting the output current of the inverter. Is counted. When the duration of the overload current exceeds a predetermined time, it is determined that the inverter is in an overload state, and the inverter is stopped.
Japanese Patent Laid-Open No. 5-260761 JP-A-9-215388 Japanese Patent Laid-Open No. 10-14267

  However, Patent Document 1 does not disclose any method for setting the overload current duration for determining that the power converter (inverter) is in an overload state. The reason why the power conversion device is determined to be in an overload state and the output current is limited is to prevent the power element constituting the power conversion device from being overheated, but the power element is overheated. The time until this depends on the output current value at that time and the cooling performance of the power element.

  And if the overload current duration for determining that the power converter is in an overload state is set to a certain predetermined time, the predetermined time will be set under the strictest conditions. Even if it does not reach a state that causes overheat destruction, the output of the power conversion device is restricted, and the ability of the power conversion device is unnecessarily limited.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a power conversion device capable of sufficiently exhibiting the device capability while preventing overheating of the power element due to overload. Is to provide.

  Another object of the present invention is to provide a current limiting method for a power conversion device that can sufficiently exhibit the device capability while preventing overheating of the power element due to overload.

  According to this invention, the power conversion device limits the output current when the power conversion circuit and the output current from the power conversion circuit exceed a predetermined threshold and the state continues for a predetermined time. A control device that controls the power conversion circuit; and a temperature detection means that detects a temperature of a cooling body that cools the power conversion circuit. The control device increases the predetermined time as the cooling body temperature detected by the temperature detection means decreases. Set longer.

  According to the invention, the power conversion device includes a power conversion circuit, a current detection unit that detects an output current from the power conversion circuit, and a temperature detection unit that detects a temperature of a cooling body that cools the power conversion circuit. And a control device that controls the power conversion circuit so as to limit the output current when the output current detected by the current detecting means exceeds a predetermined threshold and the state continues for a predetermined time. The device sets the predetermined time longer as the output current is smaller in the range where the output current exceeds the predetermined threshold and the cooling body temperature detected by the temperature detecting means is lower.

  Preferably, the control device has a map including a predetermined time determined in advance for each of the current value of the output current and the cooling body temperature, and when the output current exceeds a predetermined threshold, the control device determines a predetermined value based on the map. Set the time.

  Preferably, the power conversion device further includes a cooling device that cools the power conversion circuit with cooling water, the temperature detection unit detects the temperature of the cooling water, and the control device detects the cooling water temperature detected by the temperature detection unit. Is used to set a predetermined time.

  Preferably, the power conversion circuit includes an inverter.

  According to the present invention, the current limiting method for the power converter includes a first step of determining whether or not the output current from the power converter circuit exceeds a predetermined threshold value, and the output current is a predetermined value. A second step for determining whether or not the duration of the state exceeds a predetermined time when it is determined that the threshold is exceeded, and an output current when it is determined that the duration exceeds a predetermined time In the second step, the predetermined time is set longer as the temperature of the cooling body that cools the power conversion circuit is lower.

  According to the present invention, the current limiting method for the power converter includes a first step of determining whether or not the output current from the power converter circuit exceeds a predetermined threshold value, and the output current is a predetermined value. A second step for determining whether or not the duration of the state exceeds a predetermined time when it is determined that the threshold is exceeded, and an output current when it is determined that the duration exceeds a predetermined time In the second step, the output current is small in the range where the output current exceeds a predetermined threshold value, and the temperature of the cooling body that cools the power conversion circuit is low. The predetermined time is set longer.

  Preferably, the cooling body temperature is a temperature of cooling water for cooling the power conversion circuit.

  In the power conversion device according to the present invention, the control device sets the predetermined time until the output current is limited as the cooling body temperature detected by the temperature detecting means is lower, so that the control device has high cooling performance. In spite of this, it is judged that the power element can be overheated and the output current from the power conversion circuit is limited.

  Therefore, according to this invention, the capability which a power converter device has can fully be exhibited, preventing the overheating destruction of a power element.

  In the power conversion device according to the present invention, the control device has a smaller output current in a range where the output current exceeds a predetermined threshold value, and the lower the cooling body temperature detected by the temperature detection means, Since the predetermined time until the output current is limited is set to be long, the power element is overheated even though the predetermined time can be set long in view of the magnitude of the output current and the cooling performance of the power converter. A situation in which the output current from the power conversion circuit is determined to be obtained is limited is avoided.

  Therefore, according to this invention, the capability which a power converter device has can be exhibited to the maximum, preventing overheating destruction of a power element.

  Further, in the power conversion device according to the present invention, the control device uses the cooling water temperature detected by the temperature detection means, so that the existing cooling water temperature sensor can be used.

  Therefore, according to the present invention, the current limiting control of the power converter can be realized at low cost.

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

  FIG. 1 is an electric circuit diagram showing a configuration of a power converter according to an embodiment of the present invention.

  Referring to FIG. 1, the power conversion device according to this embodiment includes an inverter 10, a control device 20, current sensors 32-36, a temperature sensor 38, a capacitor C, a power supply line PL, and a ground line SL. And U, V, W phase lines UL, VL, WL. Inverter 10 is connected to DC power supply B through power supply line PL and ground line SL. Inverter 10 is connected to motor generator MG via U, V, and W phase lines UL, VL, and WL. Capacitor C is connected between power supply line PL and ground line SL.

  The DC power source B is made of a secondary battery such as nickel hydride or lithium ion. DC power supply B supplies the generated DC power to inverter 10 via power supply line PL and ground line SL. DC power supply B is charged by inverter 10 through power supply line PL and ground line SL.

  Motor generator MG is formed of, for example, a three-phase AC synchronous motor generator. Motor generator MG receives three-phase AC power from inverter 10 via U, V, and W phase lines UL, VL, and WL, and generates rotational torque by the received three-phase AC power. Motor generator MG supplies regenerative power generated during braking to inverter 10 via U, V, W phase lines UL, VL, WL.

  Inverter 10 includes U-phase arm 42, V-phase arm 44, and W-phase arm 46. U-phase arm 42, V-phase arm 44 and W-phase arm 46 are connected in parallel between power supply line PL and ground line SL. The U-phase arm 42 includes power transistors Q1 and Q2 connected in series, the V-phase arm 44 includes power transistors Q3 and Q4 connected in series, and the W-phase arm 46 includes power connected in series. It consists of transistors Q5 and Q6.

  Each of power transistors Q1-Q6 is made of, for example, an IGBT (Insulated Gate Bipolar Transistor). Diodes D1 to D6 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the power transistors Q1 to Q6, respectively. The connection point of each power transistor in each phase arm is connected to the anti-neutral point side of each phase coil of motor generator MG via U, V, W phase lines UL, VL, WL.

  Inverter 10 converts DC power received from power supply line PL and ground line SL into three-phase AC power based on a control signal from control device 20, and converts the converted three-phase AC power into each of U, V, and W. Output to motor generator MG via phase lines UL, VL, WL. Inverter 10 also rectifies three-phase AC power received from motor generator MG via U, V, and W phase lines UL, VL, and WL into DC power and supplies it to power supply line PL.

  Current sensors 32 to 36 are provided on the U, V, and W phase lines, respectively. Current sensors 32 to 36 detect current values Iu, Iv, and Iw flowing through the U, V, and W phase lines, respectively, and output the detected current values Iu, Iv, and Iw to control device 20.

  The temperature sensor 38 is provided in a cooling water channel in the cooling system of the inverter 10 described later. The temperature sensor 38 detects the cooling water temperature Tw of the inverter 10 and outputs the detected cooling water temperature Tw to the control device 20.

  Capacitor C is provided for smoothing the voltage of power supply line PL to which DC power supply B is connected, whereby the influence of ripple on DC power supply B due to the switching operation in inverter 10 is reduced.

  Control device 20 calculates each phase coil voltage of motor generator MG based on the torque command value and each phase current value of motor generator MG and the output voltage of DC power supply B, and power transistors Q1 to Q1 based on the calculation result. A PWM (Pulse Width Modulation) signal for turning on / off Q6 is generated and output to inverter 10.

  In addition, control device 20 controls the switching operation of power transistors Q1 to Q6 in order to rectify the regenerative power generated by motor generator MG by inverter 10 and charge DC power supply B.

  Further, control device 20 monitors whether inverter 10 is in a current concentration state based on current values Iu, Iv, and Iw received from current sensors 32 to 36. Here, the current concentration state means that, for example, when the motor generator MG is locked or in a high torque and low speed rotation state, the inverter 10 generates a current close to direct current to the motor generator MG so as to generate a rotation torque in the motor generator MG. It means the state that is flowing continuously.

  When control device 20 determines that inverter 10 is in the current concentration state, current limiting time Δt is based on current values Iu, Iv, Iw received from current sensors 32 to 36 and cooling water temperature Tw received from temperature sensor 38. When the current concentration state continues beyond the current limit time Δt, the switching operation of the power transistors Q1 to Q6 is controlled so that the output current from the inverter 10 is limited. Here, the current limit time Δt is a time during which the inverter 10 can continuously output a current without causing the power elements constituting the inverter 10 to be overheated.

  That is, the reason why the output current from the inverter 10 is limited when the current is concentrated is to prevent overheating destruction of the power elements constituting the inverter 10. Since the current limit time Δt is determined in consideration of not only the value but also the cooling performance (cooling water temperature Tw) of the inverter 10 at that time, the cooling water temperature Tw is sufficiently low and the cooling performance of the inverter 10 is high. A situation is sometimes avoided in which the output from the inverter 10 is unnecessarily limited due to the erroneous determination that the power element can be destroyed by overheating.

  In the power conversion device according to this embodiment, inverter 10 converts DC power output from DC power supply B into AC power to drive motor generator MG. Further, inverter 10 rectifies the regenerative power generated by motor generator MG and charges DC power supply B.

  In this power converter, the control device 20 determines that the power is concentrated, and the power concentration is determined based on the output current value from the inverter 10 and the coolant temperature Tw of the inverter 10. When the time Δt has elapsed, the control device 20 controls the inverter 10 to limit the output current from the inverter 10, and the inverter 10 limits the output current according to the control signal from the control device 20.

  In the above, inverter 10 constitutes a “power conversion circuit”.

  FIG. 2 is a block diagram showing a configuration of a cooling system of inverter 10 shown in FIG.

  Referring to FIG. 2, the cooling system includes an inverter 10, a motor generator MG, a radiator 50, a water pump 60, cooling water channels 72 to 78, and a temperature sensor 38. A cooling water passage 72 is provided between radiator 50 and inverter 10, and a cooling water passage 74 is provided between inverter 10 and motor generator MG. A cooling water passage 76 is provided between the motor generator MG and the water pump 60, and a cooling water passage 78 is provided between the water pump 60 and the radiator 50.

  Radiator 50 cools the cooling water received from inverter 10 and motor generator MG. The water pump 60 circulates cooling water in the direction of the arrow shown in the figure. The temperature sensor 38 is disposed in the cooling water passage 72, detects the cooling water temperature Tw immediately before the inverter 10 is cooled, and outputs the detected value of the cooling water temperature Tw to the control device 20 (not shown).

  In this cooling system, the cooling system of inverter 10 and motor generator MG is shared, and inverter 10 is arranged upstream of motor generator MG as seen from radiator 50. Then, the temperature sensor 38 detects the cooling water temperature Tw of the inverter 10 and outputs it to the control device 20.

  FIG. 3 is a diagram showing fluctuations in current when current concentration occurs in the inverter 10 shown in FIG.

  Referring to FIG. 3, the vertical axis represents the output current value I from the inverter 10 corresponding to the phase where current concentration has occurred, and the horizontal axis represents time. The current concentration determination flag is a flag that is turned on when the current concentration time indicated by Δt1 (Tw) or Δt2 (Tw) elapses, and is turned off when the current concentration state is avoided.

  In the power conversion device according to this embodiment, when current value I exceeds threshold value Ith1, it is determined that the current is concentrated. The current limit time is set longer as the current value I is smaller within the current concentration state range. FIG. 3 shows a case where the current value I at the time of current concentration is divided into four stages by threshold values Ith1 to Ith3 and Ith_max. That is, the current value I at the time of current concentration is divided into Ith1 <I ≦ Ith2, Ith2 <I ≦ Ith3, Ith3 <I ≦ Ith_max, and Ith_max <I.

  Line A shows a current waveform when the current value I at the time of current concentration exceeds the threshold value Ith_max. When current value I from inverter 10 exceeds threshold value Ith1 at time t1, control device 20 determines that the current is concentrated. Thereafter, when the amount of current continues to increase and the current value I exceeds the threshold value Ith_max, the control device 20 sets the current limit time to Δt1 (Tw). Here, Δt1 (Tw) means that the current limit time Δt1 when the current value I exceeds the threshold value Ith_max depends on the coolant temperature Tw of the inverter 10, as will be described later.

  At time t2, when the duration after the determination by the control device 20 as being in the current concentration state exceeds Δt1 (Tw), the control device 20 turns on the current concentration determination flag, and the current concentration determination flag is set. While it is on, the output current from the inverter 10 is limited in accordance with a command from the control device 20.

  Thereafter, when current value I falls below threshold value Ith1 at time t3, control device 20 turns off the current concentration determination flag, and the restriction on the output current from inverter 10 is released.

  On the other hand, the line B shows a current waveform when the current value I during current concentration is Ith1 <I ≦ Ith2. When output current I from inverter 10 exceeds threshold value Ith1 at time t1, control device 20 determines that the current is concentrated. Thereafter, the current value I changes between the threshold value Ith1 and the threshold value Ith2, and the control device 20 sets the current limit time to Δt2 (Tw) longer than Δt1 (Tw). Here, Δt2 (Tw) indicates that the current limit time Δt2 when the current value I during current concentration is in the range of Ith1 <I ≦ Ith2 depends on the cooling water temperature Tw of the inverter 10, as will be described later. means.

  Then, at time t4, when the duration after the determination by the control device 20 as being in the current concentration state exceeds Δt2 (Tw), the control device 20 turns on the current concentration determination flag, and the current concentration determination flag is set. While it is on, the output current from the inverter 10 is limited in accordance with a command from the control device 20.

  Thereafter, when current value I falls below threshold value Ith1 at time t5, control device 20 turns off the current concentration determination flag, and the restriction on the output current from inverter 10 is released.

  That is, the above concept is that the current limit time is set according to the current value because the amount of heat generated by the inverter 10 depends on the current value.

  In the figure, the slight fluctuation when the current value I is in a steady state indicates current pulsation.

  FIG. 4 is a diagram showing a single thermal characteristic at the time of current concentration of the power transistor included in the inverter 10 shown in FIG. In addition, this single-piece | unit thermal characteristic is acquired in advance by offline measurement etc.

  Referring to FIG. 4, the vertical axis indicates the element temperature of the power transistor, and the horizontal axis indicates time. The temperature T1 is a heat resistant temperature of the power transistor, and the temperature T2 is a temperature lower than the heat resistant temperature T1 of the power transistor by a margin ΔT.

  Curve C shows the thermal characteristics when the current value I exceeding the threshold value Ith_max flows through the power transistor. Curve D shows the current value I within the range of Ith1 <I ≦ Ith2 flowing through the power transistor. The thermal characteristics are shown.

  The current limit time Δt corresponding to the current value I is provisionally determined from the single unit thermal characteristics. That is, the current limit time Δt is provisionally determined from the time from the heat-resistant temperature T1 of the power transistor to the temperature T2 that exceeds the margin by ΔT.

  Therefore, in the case of the curve C, that is, the current value I having Ith_max <I, the current limit time is Δt1, and in the case of the curve D, that is, the current value I in the range of Ith1 <I ≦ Ith2, The time limit is Δt2.

  The current limit times Δt1 and Δt2 are values determined based only on the current value I. As will be described below, the current limit times Δt1 and Δt2 are corrected by the coolant temperature Tw of the inverter 10. The

  FIG. 5 is a diagram for explaining the temperature dependence of the current limit time Δt.

  Referring to FIG. 5, the vertical axis indicates the current value I flowing through the power transistor of the inverter 10 during current concentration, and the horizontal axis indicates the current limit time Δt.

  As described above, in the power conversion device according to this embodiment, when the current is concentrated, the current limit time is set longer as the current value I is smaller. Further, the cooling water temperature Tw of the inverter 10 at that time is lower. The longer the current limit time is set.

  Lines E, F, and G indicate current limit times when the cooling water temperatures are Tw3, Tw2, and Tw1 (Tw3> Tw2> Tw1), respectively. For example, when the current value I at the time of current concentration is Ith_max <I and the coolant temperature is Tw3, the current limit time is set to Δt1 (Tw3). If the cooling water temperature is Tw2 lower than Tw3, the current limit time is set to Δt1 (Tw2) longer than Δt1 (Tw3), and if the cooling water temperature is Tw1 lower than Tw2, The time limit is set to Δt1 (Tw1) which is longer than Δt1 (Tw2).

  For example, when the current value I at the time of current concentration is Ith1 <I ≦ Ith2, if the coolant temperature is Tw3, the current limit time is set to Δt2 (Tw3). If the cooling water temperature is Tw2 lower than Tw3, the current limit time is set to Δt2 (Tw2) longer than Δt2 (Tw3), and if the cooling water temperature is Tw1 lower than Tw2, The time limit is set to Δt2 (Tw1) which is longer than Δt2 (Tw2).

  That is, the above idea is that the temperature rise rate of the power transistor at the time of current concentration can be suppressed as the cooling water temperature Tw is low and the cooling performance by the cooling system is high, so the cooling water temperature Tw is low. The current limit time Δt is set longer.

  FIG. 6 is a diagram showing a map structure for determining the current limit time Δt.

  Referring to FIG. 6, current limiting time Δt is mapped in advance according to cooling water temperature Tw and current value I. The coolant temperature Tw is divided into Tw (1) to Tw (m) (m is a natural number of 2 or more, and Tw (i) ≦ Tw (j), i <j), and the current value I Is divided into Ith (1) to Ith (n) (n is a natural number of 2 or more, and Ith (i) ≦ Ith (j), i <j).

  FIG. 7 is a flowchart of the current limiting control executed when the current is concentrated by the control device 20 shown in FIG.

  Referring to FIG. 7, each phase current value output from inverter 10 is detected by current sensors 32 to 36 (step S <b> 2), and control device 20 determines whether any current value of each phase of U, V, or W is present. It is determined whether or not the threshold value Ith1 is exceeded (step S4). When control device 20 determines that the current value from inverter 10 is equal to or less than threshold value Ith1 (NO in step S4), the process is terminated.

  On the other hand, when control device 20 determines that the current value from inverter 10 exceeds threshold value Ith1 (YES in step S4), it determines that a current concentration state has occurred. Then, the control device 20 acquires the cooling water temperature Tw of the inverter 10 detected by the temperature sensor 38 (step S6), and based on a current limit time map stored in a ROM (Read Only Memory) or the like, the threshold is set. A current limit time Δt is set according to the current value I of the phase exceeding the value Ith1 and the coolant temperature Tw detected by the temperature sensor 38 (step S8).

  When the current limit time Δt is set, the control device 20 starts counting the current concentration determination flag counter (step S10). This current concentration determination flag counter is for measuring the duration of the current concentration state. Then, the control device 20 determines whether or not the count value exceeds the set current limit time Δt (step S12), and determines that the count value exceeds the current limit time Δt (YES in step S12). The switching operation of the inverter 10 is controlled so as to limit the output current (step S14).

  On the other hand, when the count value does not exceed the current limit time Δt or when the count value is reset by the current value I falling below the threshold value Ith1 before the count value exceeds the current limit time Δt (step The control device 20 ends the process (NO in S12).

  As described above, according to this embodiment, when the current value I from the inverter 10 exceeds the predetermined threshold value Ith1, the current value I is small and the coolant temperature Tw of the inverter 10 is Since the current limit time Δt is set longer as the value is lower, a situation in which the output current from the inverter 10 is unnecessarily limited is avoided. Therefore, according to this embodiment, it is possible to sufficiently bring out the capability of inverter 10 while preventing overheating destruction of the power transistor.

  Further, according to this embodiment, since the cooling water temperature of the inverter 10 is used, the existing cooling water temperature sensor can be used, and as a result, the current limiting control of the inverter 10 can be realized at low cost.

  In the above, the cooling water temperature Tw of the inverter 10 is used as a parameter of the current limiting time Δt in order to reflect the cooling performance of the inverter 10 in the current limiting time Δt, but as a parameter reflecting the cooling performance of the inverter 10. Is not limited to the cooling water temperature Tw of the inverter 10. For example, when the inverter 10 is air-cooled, the temperature of the cooling fin of the inverter 10 may be used, and the current limit time Δt may be set longer as the temperature of the cooling fin is lower.

  In the above description, the cooling system for inverter 10 is shared with motor generator MG. However, the cooling system for inverter 10 and the cooling system for motor generator MG may be configured separately.

  In the above description, the current limit time Δt is set using the map divided by the cooling water temperature Tw and the current value I of the inverter 10, but the cooling water temperature Tw is used without using the map. Alternatively, a function of the current limit time Δt may be generated using the current value I as a parameter, and the current limit time Δt may be calculated using the generated function.

  Further, in the above embodiment, the case of the inverter 10 as a power conversion device has been representatively described. However, the scope of application of the present invention is not limited to the inverter, and the power conversion device such as a converter is also applicable to this. The invention can be applied.

  The power conversion device according to the present invention is suitable for a hybrid vehicle and an electric vehicle that are attracting attention against the background of recent energy saving and environmental problems. A hybrid vehicle is a vehicle that uses a DC power source, an inverter, and a motor driven by the inverter as a power source in addition to a conventional engine. That is, a power source is obtained by driving the engine, a DC voltage from a DC power source is converted into an AC voltage by an inverter, and a motor is rotated by the converted AC voltage to obtain a power source. An electric vehicle is a vehicle that uses a DC power source, an inverter, and a motor driven by the inverter as a power source.

  In such hybrid vehicles and electric vehicles, current concentration occurs when driving at a high torque and low speed such as when starting uphill, or when the motor is locked for some reason. In this case, according to the power conversion device of the present invention, the current limit time is appropriately set based on the current value at the time of current concentration and the cooling water temperature, so that the inverter output limit is not made unnecessary. The driving capacity of hybrid vehicles and electric vehicles can be maximized.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

1 is an electric circuit diagram showing a configuration of a power conversion device according to an embodiment of the present invention. It is a block diagram which shows the structure of the cooling system of the inverter shown in FIG. It is a figure which shows the fluctuation | variation of an electric current when electric current concentration generate | occur | produces in the inverter shown in FIG. It is a figure which shows the single-piece | unit thermal characteristic at the time of the current concentration of the power transistor contained in the inverter shown in FIG. It is a figure for demonstrating the temperature dependence of electric current limitation time. It is a figure which shows the structure of the map which determines current limiting time. It is a flowchart of the current limiting control performed at the time of current concentration by the control apparatus shown in FIG.

Explanation of symbols

  10 inverter, 20 control device, 32-36 current sensor, 38 temperature sensor, 42 U-phase arm, 44 V-phase arm, 46 W-phase arm, 50 radiator, 60 water pump, 72-78 cooling water channel, B DC power supply, C Capacitor, MG motor generator, PL power supply line, SL ground line, UL U phase line, VL V phase line, WL W phase line, Q1-Q6 power transistor, D1-D6 diode.

Claims (8)

A power conversion circuit;
A control device for controlling the power conversion circuit so as to limit the output current when the output current from the power conversion circuit exceeds a predetermined threshold and the state continues for a predetermined time;
Temperature detecting means for detecting the temperature of a cooling body for cooling the power conversion circuit,
The said control apparatus is a power converter device which sets the said predetermined time long, so that the said cooling body temperature detected by the said temperature detection means is low. A power conversion circuit;
Current detection means for detecting an output current from the power conversion circuit;
Temperature detecting means for detecting the temperature of a cooling body for cooling the power conversion circuit;
A control device for controlling the power conversion circuit so as to limit the output current when the output current detected by the current detection means exceeds a predetermined threshold and the state continues for a predetermined time; Prepared,
The control device increases the predetermined time as the output current is small in a range where the output current exceeds the predetermined threshold and the cooling body temperature detected by the temperature detecting unit is low. The power conversion device to be set.   The control device includes a map including the current value of the output current and the predetermined time determined in advance for each cooling body temperature, and when the output current exceeds the predetermined threshold, the map The power conversion device according to claim 2, wherein the predetermined time is set based on the parameter. A cooling device for cooling the power conversion circuit with cooling water;
The temperature detection means detects the temperature of the cooling water,
4. The power conversion device according to claim 1, wherein the control device sets the predetermined time using the cooling water temperature detected by the temperature detection unit. 5.   The power conversion device according to claim 1, wherein the power conversion circuit includes an inverter. A first step of determining whether an output current from the power conversion circuit exceeds a predetermined threshold;
When it is determined that the output current exceeds the predetermined threshold, a second step of determining whether or not the duration of the state exceeds a predetermined time;
A third step of limiting the output current when it is determined that the duration exceeds the predetermined time;
In the second step, the predetermined time is set longer as the temperature of the cooling body that cools the power conversion circuit is lower. A first step of determining whether an output current from the power conversion circuit exceeds a predetermined threshold;
When it is determined that the output current exceeds the predetermined threshold, a second step of determining whether or not the duration of the state exceeds a predetermined time;
A third step of limiting the output current when it is determined that the duration exceeds the predetermined time;
In the second step, as the output current is smaller in a range where the output current exceeds the predetermined threshold and the temperature of the cooling body that cools the power conversion circuit is lower, the predetermined time is A method for limiting the current of the power conversion device, which is set long.   The current limiting method for a power conversion device according to claim 6 or 7, wherein the cooling body temperature is a temperature of cooling water for cooling the power conversion circuit.

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