JP5454067B2 - Cooling system for power converter - Google Patents

Description

  The present invention relates to a cooling system for a power converter that cools a power converter that performs power conversion between AC and DC.

  In the industrial field, an AC motor is often used as an actuator. In order to drive the electric motor at a variable speed, a DC-AC power converter (inverter) is required. An AC-DC power converter (converter) is used as a power source for the inverter. The power converter is composed of a plurality of power semiconductor elements.

  The power semiconductor element generates heat due to power loss or the like at a junction (also referred to as a junction). If this heat exceeds a predetermined allowable value, the power semiconductor element may be destroyed or deteriorated. For this reason, a cooling device for preventing overheating of the power semiconductor element is often attached to the power converter. There are various types of cooling devices, for example, there are an air cooling system for low capacity and a water cooling system for large capacity. The air cooling system uses a fan to circulate air, which is a refrigerant, in the power converter. On the other hand, in the water cooling system, a water cooling pump is used to circulate water as a refrigerant in the power converter.

  In general, the cooling capacity of the cooling device is determined so that the power semiconductor element is not destroyed even when the heat generated by the power converter (power semiconductor element) reaches a maximum value. The cooling device always drives a constant output while the power converter is powered on. Patent Document 1 discloses a cooling system including such a cooling device.

JP-A-11-341824

  In recent years, in the industrial field, there has been an increasing demand for reduction in running costs and energy saving of devices and the like from the viewpoint of protecting the global environment. Here, the calorific value of the power semiconductor element used in the power converter changes from moment to moment according to the operating condition of the power converter. Specifically, the amount of heat generated by the power semiconductor element greatly depends on conduction current, applied voltage, switching, and the like.

  For example, the power converter may be used for an apparatus that is loaded only when a material passes, such as a slab transfer table for a steel rolling line or a main rolling mill. Thus, when a load is intermittently applied to the power converter, the amount of heat generated by the power semiconductor element varies greatly depending on the load condition. In addition, the amount of heat generated by the power semiconductor element varies depending on the motor torque and speed of the slab transfer table, main machine rolling mill, and the like.

  Therefore, when the calorific value of the power semiconductor element is low, the cooling capacity of the cooling device may be reduced. However, the cooling device of Patent Document 1 is always driven on the assumption that the heat generation of the power semiconductor element is the maximum value. Therefore, excessive cooling of the power converter (semiconductor element) is performed until the cooling capacity of the cooling device may be reduced. Therefore, there was a problem that the cooling system could not save energy.

  Moreover, since the cooling device of Patent Document 1 is always operated in a high output state, there is a problem that noise from the cooling device (cooling system) cannot be reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cooling system for a power converter that can save energy and reduce noise in a cooling system that cools a semiconductor element.

A cooling system for a power converter according to the invention of the present application includes a semiconductor element having an IGBT and a diode used in the power converter , a DC capacitor, a DC capacitor voltage detecting unit connected to both ends of the DC capacitor, and the power conversion. A phase current detector for detecting the phase current of the detector, a cooling fin attached to the semiconductor element, a temperature detector for detecting the temperature of the cooling fin, a control circuit, the DC capacitor voltage detector, the phase The IGBT is connected to the current detection unit, the temperature detection unit, and the control circuit, and based on the information obtained therefrom, the turn-on loss of the IGBT, the turn-off loss of the IGBT, the steady loss of the IGBT, the forward loss of the diode, and the calculating a recovery loss of the diode, cooling a calculation unit for calculating the calorific value predicted value of the semiconductor element, the semiconductor element from these losses Comprising a retirement unit, and a cooling device control unit for controlling the cooling device. The cooling device control unit increases the cooling capacity of the cooling device when the predicted heat generation amount is high so that the temperature of the semiconductor element does not exceed a predetermined value, and the cooling device when the predicted heat generation amount is low. It is characterized by performing control with reduced capacity.

  According to the present invention, energy saving and noise reduction of a cooling system for a power converter can be achieved.

It is a block diagram of the cooling system for power converters. It is a flowchart explaining operation | movement of the cooling system for electric power conversion induction.

Embodiment This embodiment will be described with reference to FIGS. FIG. 1 is a block diagram of a cooling system for a power converter according to this embodiment. The power converter 11 of this embodiment includes a three-phase AC inverter and a DC capacitor 18. The power converter 11 includes an IGBT, an FWD ( free wheel diode), and a clamp diode as power semiconductor elements. The gate drive signal of the IGBT is transmitted by the gate circuit 22 connected to the gate of the IGBT. The gate circuit 22 receives switching information from the control circuit 20. On the other hand, the DC capacitor 18 is connected to the preceding stage of the three-phase AC inverter. The DC capacitor 18 is connected to a power source via a rectifier circuit, for example. A DC capacitor voltage detector 12 is connected to both ends of the DC capacitor 18. As a result, the voltage across the DC capacitor 18 can be measured.

  Further, a phase current detector 13 is connected to each phase (U phase, V phase, W phase) of the three-phase AC inverter, and the current of each phase is measured. Each phase is not particularly limited as long as it is a load, but is connected to the motor 24.

The parts that generate heat in the power converter 11 are IGBTs, FWDs , and clamp diodes (hereinafter, power semiconductor elements such as IGBTs, FWDs , and clamp diodes may be referred to as semiconductor elements, and FWDs , clamps). The diode may be referred to as a diode). These are mounted on a substrate with good heat dissipation. A cooling fin is attached to the substrate in order to cool the semiconductor element. Furthermore, in this embodiment, the temperature detection part 14 which detects the temperature of a cooling fin is fixed to this cooling fin.

  The power converter cooling system of the present embodiment includes a calculation unit 15. The calculating part 15 is a part which calculates the predicted heat generation value of the junction part of the semiconductor element. The calculation unit 15 is connected to the DC capacitor voltage detection unit 12, the phase current detection unit 13, the temperature detection unit 14, and the control circuit 20. Therefore, the calculating part 15 can acquire the information of the voltage of the DC capacitor 18, the phase current, the cooling fin temperature, and the switching state of the IGBT.

  A cooling device control unit 16 is connected to the calculation unit 15. As will be described later, the cooling device control unit 16 performs control to adjust the cooling capacity of the cooling device 17. Here, the cooling device 17 in this embodiment is a cooling fan. Therefore, the cooling fin is cooled by the air cooling function of the cooling fan, and cools (dissipates heat) the semiconductor element. The power converter 11 and the power converter cooling system of the present embodiment have the above-described configuration.

  Hereinafter, the operation of the cooling system for the power converter will be described with reference to FIG. FIG. 2 is a flowchart for explaining the operation of the cooling system for the power converter. First, the computing unit 15 acquires the values of the conduction current and applied voltage of the semiconductor element (step 50). The conduction current of the semiconductor element is grasped from the current of the phase current detector 13 and information on the switching state of the IGBT obtained from the control circuit 20. On the other hand, the applied voltage of the semiconductor element is grasped by the voltage of the DC capacitor voltage detector 12.

  Next, the process proceeds to step 51. In step 51, the calculation unit 15 calculates the predicted heat generation values of the IGBT junction unit and the diode junction unit. First, the calculation of the predicted heat generation value of the IGBT junction will be described. The loss generated in the IGBT is divided into a turn-on loss, a turn-off loss, and an on-steady loss. The turn-on loss and the turn-off loss are losses generated when the IGBT is switched. These losses are obtained from the product of the conduction current at switching and the applied voltage. The on-state steady loss is obtained by time integration of the product of the saturation voltage and the conduction current when on. The predicted heat generation value of the IGBT junction is calculated from the sum of these losses and the thermal resistance from the IGBT junction to the temperature detector 14.

  Next, calculation of the predicted heat generation value of the diode junction portion will be described. The loss generated in the diode is divided into forward loss and recovery loss. The forward loss is a loss when a current is conducted to the diode. The forward loss is obtained from the time integration of the product of the saturation voltage and the conduction current when the diode is conducting. The recovery loss is a loss that occurs when the diode changes from a conductive state to a non-conductive state. The recovery loss is obtained from the product of the conduction current and the applied voltage when the diode is changed from the conductive state to the non-conductive state. The predicted value of heat generation at the diode junction is calculated from the sum of these losses and the thermal resistance from the diode junction to the temperature detector 14. In addition, the calculating part 15 acquires the temperature of the temperature detection part 14 in step 50 or 51.

  Next, the process proceeds to step 52. In step 52, the predicted heat generation value calculated by the calculation unit 15 is transmitted to the cooling device control unit 16.

  Next, the process proceeds to step 53. The cooling device control unit 16 controls the cooling device 17 with reference to the predicted heat generation value so that the temperature of the junction portion of the semiconductor element does not exceed a predetermined value. That is, when the predicted heat generation value is high, control is performed to increase the cooling capacity of the cooling device. And when the calorific value prediction value is low, control which reduced the cooling capacity of the cooling device is performed. The cooling device is controlled by turning on / off the cooling fan or adjusting the power supplied to the cooling fan.

  According to the cooling system for a power converter of the present embodiment, the cooling capacity of the cooling device is adjusted according to the predicted calorific value. Therefore, excessive cooling of the power converter can be avoided until the cooling capacity of the cooling device may be reduced. Therefore, energy saving of the cooling system for the power converter can be achieved.

  Moreover, since the cooling system for power converters of this embodiment may reduce the cooling capacity of the cooling device even during operation of the power converter, noise from the cooling device can be reduced.

  Although the cooling device of this embodiment cools the cooling fins with a cooling fan, the present invention is not limited to this. That is, instead of the cooling fan, a water cooling pump using water as a refrigerant may be used. A plurality of cooling fins or water cooling pumps may be provided. Thereby, the cooling capacity of a cooling device can be increased / decreased by increase / decrease in the drive number of a cooling fin or a water cooling pump.

  DESCRIPTION OF SYMBOLS 11 Power converter, 12 DC capacitor voltage detection part, 13 Phase current detection part 13, 15 Calculation part, 16 Cooling device control part, 17 Cooling device, 18 DC capacitor, 20 Control circuit, 24 Motor

Claims (2)

A semiconductor device having an IGBT and a diode used in a power converter ;
A DC capacitor;
A DC capacitor voltage detector connected to both ends of the DC capacitor;
A phase current detector for detecting a phase current of the power converter;
Cooling fins for cooling the semiconductor element;
A temperature detector for detecting the temperature of the cooling fin;
A control circuit;
Connected to the DC capacitor voltage detector, the phase current detector, the temperature detector, and the control circuit, and based on information obtained from these, the turn-on loss of the IGBT, the turn-off loss of the IGBT, and the steady loss of the IGBT Calculating a forward loss of the diode, and a recovery loss of the diode, and calculating a predicted heat generation amount of the semiconductor element from these losses ;
A cooling device for cooling the semiconductor element;
A cooling device control unit for controlling the cooling device,
The cooling device control unit increases the cooling capacity of the cooling device when the predicted heat generation amount is high and prevents the cooling when the predicted heat generation value is low so that the temperature of the semiconductor element does not exceed a predetermined value. A cooling system for a power converter characterized by performing control with reduced capacity. The cooling device includes a plurality of fans or a plurality of water cooling pumps,
2. The cooling system for a power converter according to claim 1, wherein the cooling device control unit increases or decreases the cooling capacity by increasing or decreasing the number of driving of the plurality of fans or the plurality of water cooling pumps.

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