JP2023008084A - Power conversion device and power conversion method - Google Patents

Abstract

To accurately detect temperature difference between power conversion units connected in parallel.SOLUTION: A power conversion device includes: a plurality of power conversion units 14, 15 connected in parallel, respectively having first switching elements 24, 34 and second switching elements 25, 35 connected in series in each power conversion unit; temperature sensors 41, 42 for detecting internal temperatures for each of the power conversion units 14, 15; and a signal generation part 120 for generating on/off command signals for control electrodes of the first switching elements 24, 34 and the second switching elements 25, 35 for each of the power conversion units 14, 15, according to the detection results of the temperature sensors 41, 42. The signal generation part 120 detects temperatures at the respective power conversion units when the power conversion device 1 outputs DC current, using the temperature sensors 41, 42.SELECTED DRAWING: Figure 7

Description

The present invention relates to a power conversion device and a power conversion method for converting power between input and output.

In order to reduce the world's energy consumption, there is a demand for higher efficiency in power converters that use semiconductor switching elements, such as inverters that drive motors, converters that supply power to inverters, and charging/discharging devices for electric vehicles. ing. These power converters are sometimes configured by connecting in parallel a plurality of power conversion units each having a switching element.

For example, Patent Document 1 states, "When IGBT modules are connected in parallel, temperature variations occur in the IGBT chips due to variations in characteristics and structures, and if the absolute maximum temperature is suppressed, the size of the device increases and the cost increases. A temperature detector is installed in each module with an embedded detection sensor, and the magnitude of the temperature difference is determined by a comparator, and the temperature is lowered by delaying the turn-on timing of the module with a high temperature using an integration circuit of resistors and capacitors. .”

JP 2009-159662 A

Generally, a power conversion unit includes switching elements called upper and lower arms. The technique described in Patent Literature 1 can suppress the temperature imbalance between switching elements arranged in parallel. However, there is little temperature imbalance between the power conversion units connected in parallel at the time of AC current output, so there is a problem that the detection accuracy of the temperature difference between the power conversion units is low.

In view of the above situation, there has been a demand for a technique capable of detecting the temperature difference between power conversion units connected in parallel with high accuracy.

In order to solve the above problems, a power conversion device according to one aspect of the present invention includes a plurality of power conversion units connected in parallel, each power conversion unit including a first switching element and a second switching element connected in series; A temperature sensor for detecting the internal temperature of each power conversion unit, and generating an on/off command signal for the control electrodes of the first switching element and the second switching element for each power conversion unit according to the detection result of the temperature sensor. and a signal generator, wherein the signal generator uses a temperature sensor to detect the temperature of each power conversion unit when the power converter outputs direct current.

According to at least one aspect of the present invention, the temperature difference between the power conversion units can be detected with high accuracy by detecting the temperature of the power conversion units connected in parallel when the power conversion device outputs direct current.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a figure showing an example of the whole elevator system composition concerning one embodiment of the present invention. 1 is a configuration diagram showing an example of a conventional power converter (inverter system) and its drive circuit; FIG. 4 is a timing chart showing an example of waveforms of signals measured at each part when there is no turn operation delay in switching elements between power conversion units connected in parallel. 4 is a timing chart showing an example of waveforms of signals measured at each part when turn-on delay time variations exist in switching elements between power conversion units connected in parallel. 4 is a timing chart showing an example of waveforms of signals measured at each part when switching elements between power conversion units connected in parallel have variations in turn-off delay time; FIG. 3 is a diagram showing an example of velocity characteristics with respect to time per one operation period of the elevator system according to one embodiment of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows an example of the power converter device (inverter system) which concerns on one Embodiment of this invention, and its drive circuit. FIG. 4 is a diagram showing an example of a DC current output to a motor by a three-phase inverter system during a startup compensation period; 4 is a graph showing the characteristics of detected temperature versus output current of the inverter system; 4 is a flowchart showing an example procedure of processing for reducing temperature differences between power conversion units connected in parallel according to an embodiment of the present invention.

Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, constituent elements having substantially the same function or configuration are denoted by the same reference numerals, and overlapping descriptions are omitted.

2. Description of the Related Art A power conversion device can convert DC power into AC power or vice versa by switching operation of a semiconductor device, and is applied in many fields such as elevators, railways, and automobiles. 2. Description of the Related Art Inverter devices, which are an example of a power conversion device, are required to have a higher output density, and power conversion devices are becoming smaller and lighter. As power semiconductor modules equipped with power semiconductor elements, power conversion units (parts of power converters) that integrate parts such as capacitors and bus bars become smaller, the size of drive circuits for driving power semiconductor elements is becoming smaller. There is an increasing need for more compact and low-cost products.

In addition, by installing multiple power conversion units that integrate parts such as power semiconductor modules, capacitors, busbars, and gate circuits, and by working to standardize parts and improve output capacity, the cost of power conversion equipment can be reduced. Realized. By increasing the number of parallel power conversion units, it is possible to increase the capacity of the power converter.

When power semiconductor modules are connected in parallel, the power semiconductor elements have characteristic variations such as the turn-on delay time and turn-off delay time of the power semiconductor elements. As a result, current concentrates in some power semiconductor elements, increasing switching loss and conduction loss, and causing temperature imbalance.

Conventionally, in consideration of current imbalance, when connecting power semiconductor elements, ie, power conversion units, in parallel, it was necessary to design a current value smaller than the rated current of each power semiconductor element. Therefore, it has not been possible to maximize the performance of the power semiconductor device.

As a method of detecting the current imbalance, there is a method of measuring the current of each power semiconductor element with a current sensor, but the same number of current sensors as the number of power semiconductor elements is required. Therefore, the cost increases by the number of added current sensors. Here, there is known a method of using a temperature sensor, which is less expensive than the current sensor, instead of the current sensor by utilizing the fact that temperature imbalance occurs when the current of the power semiconductor element becomes unbalanced. However, in the elevator system, the direct current output and the alternating current output are switched depending on the operation state, so the detection result changes depending on the temperature detection timing. Therefore, the problem is how to detect the temperature. A power converter according to an embodiment of the present invention in which a temperature sensor is provided in the power converter unit will be described below.

<One embodiment>
FIG. 1 is a diagram showing an example of the overall configuration of an elevator system according to one embodiment of the present invention. In the illustrated elevator system 1, AC power supplied from a system 2 is input via a filter circuit 3 to a three-phase converter system 10 in which a plurality of power conversion units 12 and 13 are connected in parallel. AC power input to converter system 10 is converted from AC to DC via power conversion units 12 and 13 in converter system 10 . A three-phase inverter system 11 in which a plurality of power conversion units 14 and 15 are connected in parallel drives a motor 5 via a filter circuit 4 . Filter circuits 3 and 4 remove harmonic components from input sine waves (square waves).

The load of the motor 5 includes an elevator car 7 connected to a rope 6 and a weight 8 for balancing the car 7 . The power supplied to the motor 5 is consumed to hoist the rope 6 and move the elevator car 6 up and down.

The converter system 10 and the inverter system 11 are controlled by the control circuit section 9 . The control circuit section 9 controls the on/off of the switching elements provided in the power conversion units 14 and 15 to control the current output to the load side.

[Configuration of conventional power converter]
FIG. 2 is a configuration diagram showing an example of a conventional power converter and its drive circuit. In order to avoid complication of the drawing, only one phase of the bus is shown and the other phases are omitted. As shown in FIG. 2, in an inverter system 100, which is a power conversion device, power conversion units 14 and 15 are connected in parallel. Input sides of the power conversion units 14 and 15 are connected in parallel to a DC power supply 102 (corresponding to the converter system 10 ), and output sides are connected to a resistive load 104 and an inductive load 105 of the inverter system 100 . A resistive load 104 and an inductive load 105 are provided as output loads. A current sensor 106 is attached to the wiring between the output terminal of the inverter system 100 and the load.

The power conversion unit 14 includes a capacitor 21 , an upper arm gate circuit 22 , a lower arm gate circuit 23 , an upper arm switching element 24 , a lower arm switching element 25 , an upper arm switching freewheeling diode 26 and a lower arm switching freewheeling diode 27 . An upper arm switching freewheeling diode 26 and a lower arm switching freewheeling diode 27 are connected in antiparallel to the upper arm switching element 24 and the lower arm switching element 25, respectively. A switching leg consisting of an upper arm switching element 24 and a lower arm switching element 25 connected in series is connected in parallel with the capacitor 21 .

A connection midpoint between the upper arm switching element 24 and the lower arm switching element 25 is connected to the output terminal T1 via a resistance load 28 and an inductive load 29 connected in series. Output terminals of the upper arm gate circuit 22 and the lower arm gate circuit 23 are connected to gate terminals (control electrodes) of the upper arm switching element 24 and the lower arm switching element 25, respectively.

The power conversion unit 15 includes a capacitor 31 , an upper arm gate circuit 32 , a lower arm gate circuit 33 , an upper arm switching element 34 , a lower arm switching element 35 , an upper arm switching freewheeling diode 36 and a lower arm switching freewheeling diode 37 . An upper arm switching freewheeling diode 36 and a lower arm switching freewheeling diode 37 are connected in antiparallel to the upper arm switching element 34 and the lower arm switching element 35, respectively. A switching leg consisting of an upper arm switching element 34 and a lower arm switching element 35 connected in series is connected in parallel with the capacitor 31 .

A connection midpoint of the upper arm switching element 34 and the lower arm switching element 35 is connected to the output terminal T2 via a resistance load 38 and an inductive load 39 connected in series. Output terminals of the upper arm gate circuit 32 and the lower arm gate circuit 33 are connected to gate terminals (control electrodes) of the upper arm switching element 34 and the lower arm switching element 35, respectively.

In the following description, the upper arm switching element 24, the lower arm switching element 25, the upper arm switching element 34, and the lower arm switching element 35 may be abbreviated as "switching elements". Also, the upper arm gate circuit 22, the lower arm gate circuit 23, the upper arm gate circuit 32, and the lower arm gate circuit 33 may be abbreviated as "gate circuits".

The switching elements forming the power conversion units 14 and 15 are, for example, IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductors). The same applies to the switching elements of power conversion units 12 and 13 .

One end of the capacitor 21 of the power conversion unit 14 is connected to one electrode (eg, positive electrode) of the DC power supply 102 , and the other end of the capacitor 21 is connected to the other electrode (eg, negative electrode) of the DC power supply 102 . The other electrode of DC power supply 102 is connected to ground 103 . The same applies to capacitor 31 of power conversion unit 15 . The output terminal T1 and the output terminal T2 are connected to the output terminal T3 (on the load side) via the resistive load 104 and the inductive load 105 . A current sensor 106 for detecting an output current is connected to wiring connecting the resistive load 104 and the inductive load 105 to the output terminal T3.

Note that if the inductance of the inductive load 105 of the inverter system 100 can be substituted by the inductance of wiring, the inductive load 105 may be omitted. Also, if the load connected to the output terminal T3 has a sufficiently large inductance, such as the motor 5, or if it has characteristics that can be regarded as a current source, the inductive load 105 may be omitted.

The control circuit section 9 shown in FIG. 1 controls ON/OFF of the switching elements 24 , 25 , 34 , 35 provided in the power conversion units 14 , 15 and controls the output current Itotal detected by the current sensor 106 . The output current Itotal is the sum of the output current I1 of the power conversion unit 14 and the output current I2 of the power conversion unit 15 . Based on the output current Itotal detected by the current sensor 106, the control circuit unit 9 controls the switching elements 24, 25, 34 and 35 to turn on/off. The power conversion units 14, 15 are provided with gate circuits 22, 23, 32, 33 that supply gate signals to the switching elements 24, 25, 34, 35, respectively. The control circuit unit 9 outputs a control command to a gate circuit corresponding to each of the switching elements 24 , 25 , 34 and 35 to control switching operations (ON/OFF) of the switching elements 24 , 25 , 34 and 35 .

The control circuit unit 9 is a controller composed of, for example, a microcomputer. The control circuit unit 9 includes an analog/digital (A/D) conversion circuit 9a that converts the output current Itotal detected by the current sensor 106 into a digital signal, a processor 9b, a memory 9c, and the like. The processor 9b is, for example, a processing device such as a CPU (Central Processing Unit). As a processing device, an MPU (Micro-Processing Unit) may be used instead of the CPU. The memory 9c is a storage device such as a semiconductor memory that stores software program codes (control programs) for realizing each function according to the present embodiment. The control circuit unit 9 includes a network interface (not shown), and receives a target value of output current (load current) from, for example, an ECU (Electronic Control Unit) of the controlled system. The processor 9b reads and executes the control program from the memory 9c, and controls the switching elements 24, 25, 34, 35 based on the current detection value of the current sensor 106 input from the A/D conversion circuit 9a and the target value. A control command (input signal 101) is output to the gate circuit corresponding to .

An input signal 101 is output from the control circuit portion 9 as a control command, and the input signal 101 is input to gate circuits 22 , 23 , 32 and 33 . The gate circuits 22, 23, 32 and 33 respectively generate gate signals (gate voltage pulses) for driving the switching elements 24, 25, 34 and 35 based on the input signal 101, and use the gate signals for upper arm switching. Input to gate terminals of elements 24 and 34 and lower arm switching elements 25 and 35 . The gate signal is a signal (on/off command signal) that commands the switching element to turn on/off.

When the gate signal of the upper arm switching elements 24, 34 and the lower arm switching elements 25, 35 is switched from high level to low level (turned on), the source terminal and the drain terminal are electrically connected to turn on, and current flows. Conversely, when the gate signal of the upper arm switching elements 24, 34 and the lower arm switching elements 25, 35 switches from low level to high level (turns off), there is no conduction between the source terminal and the drain terminal and the switching elements 25, 35 turn off. does not flow.

[Operating waveform when there is no turn operation delay time variation]
FIG. 3 is a timing chart showing an example of waveforms of signals measured at each part when switching elements between the power conversion units 14 and 15 connected in parallel have no variation in turn operation delay time. The horizontal axis of FIG. 3 indicates time [s]. The vertical axis of FIG. 3 represents, from the top, the gate signal of the power conversion unit 14, the gate signal of the power conversion unit 15, the output voltage of the power conversion unit 14, the output voltage of the power conversion unit 15, the output current of the power conversion unit 14, They are the output current of the power conversion unit 15 , the temperature of the power conversion unit 14 , and the temperature of the power conversion unit 15 . In this specification, the case where the inductance of the inductive load 105 and the inductance of the load side is sufficiently large and the current Itotal of the inductive load 105 can be regarded as constant will be explained. Also, the voltage applied to the capacitors 21 and 31 is equal to the voltage of the DC power supply 102.

When gate signals with the same pulse waveform are input to the switching elements 24, 25, 34, and 35 of the power conversion units 14 and 15, and there is no delay time variation in these switching elements, the output voltage of the power conversion units 14 and 15 The turn-on delay times Ton1 and Ton2 are equal. Similarly, the turn-off delay times Toff1 and Toff2 are also equal. As a result, the output currents of power conversion units 14 and 15 are equal. Also, the temperatures of the power conversion units 14 and 15 become equal.

[Operating waveform when turn-on delay time varies]
FIG. 4 is a timing chart showing an example of waveforms of signals measured at each part when switching elements between the power conversion units 14 and 15 connected in parallel have variations in turn-on delay time. The relationship between the horizontal axis and the vertical axis in FIG. 4 is the same as in FIG.

When gate signals having the same pulse waveform are input to the switching elements 24, 25, 34, and 35 of the power conversion units 14 and 15, the turn-on delay times Ton1 and Ton2 of these switching elements vary (Ton1<Ton2). The pulse width of the output voltage of power conversion unit 15 is narrower than that of power conversion unit 14 . As a result, the output current of power conversion unit 15 becomes smaller, and the output current of power conversion unit 14 becomes larger than that of power conversion unit 15 . As a result, the temperature of power conversion unit 14 becomes higher than that of power conversion unit 15 .

[Operating waveform when turn-off delay time varies]
FIG. 5 is a timing chart showing an example of waveforms of signals measured at each part when switching elements between the power conversion units 14 and 15 connected in parallel have variations in turn-off delay time. The relationship between the horizontal axis and the vertical axis in FIG. 5 is the same as in FIG.

When gate signals having the same pulse waveform are input to the switching elements 24, 25, 34, and 35 of the power conversion units 14 and 15, the turn-off delay times Toff1 and Toff2 of these switching elements vary (Toff1<Toff2). The pulse width of the output voltage of power conversion unit 15 is wider than that of power conversion unit 14 . As a result, the output current of power conversion unit 15 becomes large, and the output current of power conversion unit 14 becomes smaller than that of power conversion unit 15 . As a result, the temperature of power conversion unit 14 is lower than that of power conversion unit 15 .

If the output current between the power conversion units 14 and 15 connected in parallel is unbalanced, the current concentrates in some switching elements, switching loss and conduction loss increase, and the temperature of the switching element (between the power conversion units 14 and 15) increases. imbalance occurs.

Therefore, the problem is how to detect the occurrence of an imbalance in the output currents between the power conversion units 14 and 15 at a lower cost than the method using the current sensor 106 and with high accuracy even when using a temperature sensor.

[Speed characteristics of elevator system]
FIG. 6 is a diagram showing an example of velocity characteristics with respect to time per operation period of the elevator system 1. In FIG. The horizontal axis in FIG. 6 represents time [s], and the vertical axis represents velocity [m/s]. As shown, the elevator system 1 includes a starting compensation period 150, an acceleration period 151, a constant speed period 152, and a deceleration period 153 in one operation period.

In the starting compensation period 150, the elevator system 1 fixes the motor 5 and causes the motor 5 to generate torque by applying a direct current. At this stage, the motor 5 is still stopped and the car 7 does not move. In the acceleration period 151 , the elevator system 1 outputs alternating current from the power conversion device, and increases the frequency of the output current to increase the rotational speed of the motor 5 and accelerate the car 6 . During the constant speed period 152, the elevator system 1 keeps the frequency of the output current constant and the rotational speed of the motor 5 constant. During the deceleration period 153, the elevator system 1 reduces the frequency of the output current to slow down the rotational speed of the motor 5 and decelerate the car 6. FIG.

Resistive loads 28, 38 having resistance components and inductive loads 29, 39 having inductance components are present between the power conversion units 14, 15 connected in parallel. Since the load during DC current output has no inductance component and only a resistance component, the cross current flowing between the power conversion units 14 and 15 connected in parallel increases, and the output current imbalance of the power conversion units 14 and 15 becomes unbalanced. become maximum. Here, the greater the imbalance between the output currents of the power conversion units 14 and 15, the greater the temperature difference (temperature imbalance) between the power conversion units 14 and 15, and the greater the temperature difference becomes.

Therefore, the start-up compensation period 150 in which the DC current is output is compared with the acceleration period 151, the constant speed period 152, and the deceleration period 153 in which the AC current is output. A significant temperature difference is occurring. Therefore, during the startup compensation period 150, the temperature difference between the power conversion units 14 and 15 can be detected with high accuracy. Therefore, by detecting the temperature difference between the power conversion units 14 and 15 during the startup compensation period 150 in which the cross current is output, the imbalance of the output currents between the power conversion units 14 and 15 can be accurately detected. can be done.

[Configuration of power converter according to one embodiment]
Next, a power converter and its drive circuit according to an embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a configuration diagram showing an example of a power converter and its drive circuit according to one embodiment of the present invention. The inverter system 11, which is a power conversion device, is the same as the conventional inverter system 100 (FIG. 2) in that it includes power conversion units 14 and 15, but supplies power to the gate terminals of the gate circuits 22 to 33. The control signal (gate voltage pulse width) is different.

As shown in FIG. 7 , the input sides of power conversion units 14 and 15 are connected in parallel to DC power supply 102 , and the output sides are connected in parallel to resistive load 104 and inductive load 105 of inverter system 11 . A current sensor 106 is attached to the wiring on the output side of the inverter system 11 . Since the internal configuration of the power conversion units 14 and 15 is the same as the configuration shown in FIG. 2, the different points will be described.

The power conversion unit 14 has a temperature sensor 41 arranged near the upper arm switching element 24 and the lower arm switching element 25 . The distances between the upper arm switching element 24 and the lower arm switching element 25 and the temperature sensor 41 are designed to be appropriate distances for measuring the temperatures of the switching elements 24 and 25 through experiments or the like. Also, the power conversion unit 15 has a temperature sensor 42 arranged near the upper arm switching element 34 and the lower arm switching element 35 . Temperature sensor 41 detects switching elements 24 and 25 of power conversion unit 14 , that is, the temperature within power conversion unit 14 , and temperature sensor 41 detects switching elements 34 and 35 of power conversion unit 15 , that is, the temperature within power conversion unit 15 . to detect The detected temperature information is input to the temperature storage unit 121 .

The control circuit section 9 includes a signal generation section 120 that generates control signals to be supplied to the gate circuits 22 , 23 , 32 and 33 . The signal generation section 120 has a temperature storage section 121 and an on/off time adjustment section 122 . The temperature storage unit 121 is composed of a processor 9b and a memory 9c, and stores temperature information measured by the temperature sensors 41 and . The temperature information accumulated in the temperature accumulation section 121 and the input signal 101 are inputted to the on/off time adjustment section 122 . The ON/OFF time adjustment unit 122 adjusts the pulse width of the input signal 101 (gate voltage pulse) based on the temperature information and the input signal 101, and uses the adjusted input signal 101 as an ON/OFF command signal for each gate circuit 22. , 23, 32, 33. Input signal 101 may be input to on/off time adjustment section 122 via temperature storage section 121 .

FIG. 8 shows an example of the DC current that the three-phase inverter system 11 outputs to the motor 5 during the startup compensation period 150. As shown in FIG. The phase difference of each phase with respect to the reference axis is determined by the position of the motor 5 (the position of the rotating shaft). The motor position during start-up compensation is the motor position when the motor 5 was stopped in the previous operation mode, and the motor position is irregular. Therefore, the output currents of the power conversion units 14 and 15 become irregular during the startup compensation period 150 .

[Temperature characteristics against output current]
FIG. 9 is a graph showing the characteristics (rate of change) of the detected temperature with respect to the output current of the inverter system 11. As shown in FIG. In FIG. 9, the horizontal axis represents the magnitude (absolute value) [A] of the output current Itotal of the power converter (inverter system 11), and the vertical axis represents the temperature difference ΔT [°C] between the power conversion units 14 and 15 connected in parallel. represents.

Hereinafter, in this specification, the temperature characteristic with respect to the output current of the inverter system 11 is called a rate of change. During elevator operation, a DC current is output only during the startup compensation period 150 . Since the imbalance of the output current is the largest when the DC current is output, the temperature difference can be detected with high accuracy. Therefore, it is desirable to detect it during start-up compensation for outputting a DC current. However, as described with reference to FIG. 8, when the DC current is output, a different DC output current is obtained each time detection is performed depending on the position of the motor (the position of the rotating shaft).

When comparing the temperature difference between the power conversion units 14 and 15, it is necessary to compare the same DC output current, but since the DC output current is irregular depending on the motor position, it is difficult to compare the temperature difference with the same DC output current. is. Therefore, the temperature of the power conversion units 14 and 15 is detected multiple times and the temperature information for the DC current is accumulated. The stored information allows calculation of the rate of change of the temperature difference between the power conversion units 14 and 15 with respect to the DC output current. By using the change rate of the temperature difference, it is possible to detect the temperature imbalance occurring between the power conversion units 14 and 15 connected in parallel.

The inverter system 11 detects the temperature of the power conversion unit 14 and the power conversion unit 15 when outputting a direct current. A temperature difference between the power conversion units 14 and 15 connected in parallel is calculated from the detected temperature, and information on the output current and the temperature difference is accumulated. Information on the output current and the temperature difference is accumulated at least twice or more times, and the change rate 200 of the temperature difference with respect to the output current is calculated from the detection results.

When the rate of change 200 is large, the temperature imbalance is large and loss concentrates in some switching elements, so it is necessary to eliminate the imbalance. Therefore, the control for resolving the imbalance in accordance with the change rate of the temperature difference will be described next.

The output current and temperature imbalance of the power conversion units 14 and 15 depend on the pulse width variations of the output voltages of the power conversion units 14 and 15 caused by the delay time variations in the turn operation of the switching elements. Therefore, in order to eliminate the imbalance of the output current, it is necessary to adjust the gate signal supplied to each gate circuit according to the relationship between the change rate of the temperature difference and the threshold value.

Further, as a method of controlling imbalance elimination according to the rate of change of the temperature difference, for example, when the rate of change 200 exceeds a threshold, the on/off time adjusting section 122 delays the turn-on time of the power conversion unit on the high temperature side. By increasing the pulse width, the pulse width is narrowed, and control is performed to reduce the imbalance. After the control, the temperature of the power conversion units 14 and 15 is detected and stored again, and the rate of change 201 of the temperature difference between the power conversion units 14 and 15 is calculated.

The rate of change 201 after control is lower than the rate of change 200, and since the temperature difference changes less with respect to the output current of the inverter system 11, the temperatures of the power conversion units 14 and 15 are uniformed. . As a result, the temperature imbalance of the power conversion units 14 and 15 is reduced, so it is possible to suppress an increase in switching loss and conduction loss of some switching elements. If the change rate of the temperature difference is equal to or less than the threshold, it is determined that there is no temperature imbalance and adjustment is not performed.

When the rate of change 200 exceeds the threshold, the pulse width is widened by delaying the turn-off time of the power conversion unit on the low temperature side, and the rate of change 200 is reduced. A method of equalizing the temperature between the power conversion units 14 and 15 by doing so may also be used.

Thus, the signal generator 120 has a function of correcting at least one of the turn-on time and turn-off time of the on/off command signal according to the detected temperature imbalance between the power conversion units 14 and 15 .

[Procedure example of temperature difference reduction processing]
Next, a procedure example of processing for reducing the temperature difference between the power conversion units 14 and 15 connected in parallel according to one embodiment of the present invention will be described with reference to FIG.

FIG. 10 is a flow chart showing an example of the procedure for reducing the temperature difference between the power conversion units 14 and 15 connected in parallel. The signal generator 120 repeats the processing of the following steps S2 to S4 until the count value of the number of times of detection reaches a predetermined number (a plurality of times) (S1). First, the signal generation unit 120 determines whether or not the current activation compensation period is 150 (S2). No determination in S2), the determination processing in step S2 is executed again.

Next, signal generation unit 120 detects the temperature of power conversion units 14 and 15 and the output current of inverter system 11 using temperature sensors 41 and 42 and current sensor 106 in startup compensation period 150, and detects the detected temperature and the output current of inverter system 11. Information on the output current is stored in the temperature storage unit 121 (S3). Next, the signal generator 120 increments the count value of the number of detections of the temperature and the output current by "1" (S4).

Next, the signal generation unit 120 calculates the change rate α of the temperature difference between the power conversion units 14 and 15 with respect to the output current (for example, the change rate 200 in FIG. 9) from the accumulated temperature and output current information (S5). . When the rate of change α is greater than the threshold (Yes determination in S6), the signal generator 120 adjusts the gate voltage pulse width (S7). For example, the signal generator 120 uses the on/off time adjuster 122 to delay the turn-on time of the switching element included in the power conversion unit on the high temperature side, and the change rate α of the temperature difference between the power conversion units 14 and 15 to be smaller. By reducing the rate of change α, the temperatures of the power conversion units 14 and 15 can be controlled to be uniform.

On the other hand, when the rate of change α is equal to or less than the threshold (No determination in S6), it is determined that there is no temperature imbalance between the power conversion units 14 and 15 or the temperature imbalance is slight, and the gate voltage pulse width is not adjusted. After the process of step S7, or in the case of No determination in step S6, the process of this flowchart is terminated.

According to the power conversion apparatus according to the embodiment of the present invention described above, when the inverter system 11 outputs a direct current, the temperatures of the power conversion units 14 and 15 connected in parallel are detected multiple times and stored in the temperature storage section 121 . . Then, the inverter system 11 adjusts the pulse width of the gate signal of each switching element when the change rate α of the temperature difference between the power conversion units 14 and 15 with respect to the output current exceeds the threshold. As a result, the inverter system 11 according to this embodiment can detect the temperature difference between the power conversion units 14 and 15 with higher precision than the conventional technology.

[Adjustment of upper and lower arms according to output current]
Further, it is necessary to switch the upper arm switching elements 24, 34 and the lower arm switching elements 25, 35 according to the direction of the output current of the inverter system 11, and adjust the gate signals respectively. Therefore, next, a method of adjusting the upper and lower arms according to the output current of the inverter system 11 will be described.

Current flows through the upper arm switching elements 24 and 34 when current is output from the inverter system 11, and current flows through the lower arm switching elements 25 and 35 when current is being drawn into the inverter system 11. The challenge is how to change the arm that adjusts the gating signal accordingly.

Therefore, the current sensor 106 is used to detect whether the current is being output or drawn from the inverter system 11, and the arm for adjusting the gate signal is switched. As a result, variations in the pulse width of the gate voltage can be suppressed separately for the upper and lower arms. A current detected by the current sensor 106 is used to determine whether a current is being drawn from the inverter system 11 .

In this way, the signal generation unit 120 switches the upper arm switching elements 24 and 25 and the lower arm switching elements 25 and 35 by the on/off time adjustment unit 122 according to the output current Itotal of the inverter system 11 to turn on/off the switching elements. It has a function of correcting at least one of the turn-on time and turn-off time of the off command signal.

That is, when current is output from the inverter system 11, the signal generator 120 determines the turn-on time or turn-off time of the switching elements 24, 34 corresponding to the upper arm among the upper arm switching elements 24, 34 and the lower arm switching elements 25, 35. Correct at least one. Further, when current is drawn into the inverter system 11, the signal generator 120 determines the turn-on time or the turn-off time of the switching elements 25, 35 corresponding to the lower arm among the upper arm switching elements 24, 34 and the lower arm switching elements 25, 35. Correct at least one.

Since the signal generator 120 has such a correction function, it is possible to select an appropriate arm from the lower arm and the upper arm at the time of current output and current draw of the inverter system 11, and adjust the delay time of the turn operation. can be done.

As described above, the power converter (inverter system 11) according to the present embodiment includes the first switching elements (upper arm switching elements 24, 34) and the second switching elements (upper arm switching elements 25, 35) connected in series. Each power conversion unit (power conversion units 14, 15) has a plurality of power conversion units connected in parallel, a temperature sensor (temperature sensors 41, 42) for detecting the internal temperature of each power conversion unit, and a temperature sensor. a signal generator (signal generator 120) that generates an ON/OFF command signal (gate signal) for the control electrodes of the first switching element and the second switching element for each power conversion unit according to the detection result of There is a power conversion device. Then, the signal generator uses the temperature sensor to detect the temperature of each power conversion unit when the power conversion device outputs the direct current.

In addition, in the power conversion device (inverter system 11) according to the present embodiment, the DC current output time is the startup compensation period of the motor connected to the power conversion device.

In addition, in the power conversion device (inverter system 11) according to the present embodiment, the signal generation section includes a storage device (temperature accumulation section 121) that accumulates the detected temperature information of each power conversion unit. Then, the power conversion device accumulates the output current of the power conversion device and the temperature information of each power conversion unit detected by the temperature sensor. The temperature imbalance between the power conversion units is detected by calculating the rate of change and comparing the rate of change of the temperature difference with the threshold.

According to the power conversion device according to the present embodiment described above, the temperature of the power conversion units connected in parallel when the power conversion device outputs a direct current is detected and stored multiple times. A temperature difference between the conversion units can be detected.

[Modification]
In the above-described embodiment, the start compensation period 150 of the motor 5 is used as the DC current output time of the inverter system 11, but other methods may be used. For example, in a system such as the elevator system 1, the power converter (inverter system 11) is provided with a DC current output mode, and when the DC current output mode is selected, each power conversion unit when the power converter outputs DC current. Temperature may be detected.

Also, in this specification, the configuration of the power conversion device (inverter system 11) in which two power conversion units are connected in parallel has been described, but the number of power conversion units connected in parallel may be three or more. In that case, for example, the change rate of the temperature difference between the power conversion units may be obtained for all combinations of a plurality of combinations of power conversion units, or the temperature difference may be calculated for only one or more combinations of power conversion units specified in advance. A rate of change of the difference may be determined.

Also, an example in which the power conversion device of the present invention is applied to a three-phase inverter system has been described, but the power conversion device of the present invention can of course also be applied to a three-phase converter system having parallel-connected power conversion units. . In addition, the power conversion device of the present invention can also be applied to a single-phase inverter system, a single-phase converter system, a boost converter system, a buck converter system, etc., which include power conversion units connected in parallel.

Furthermore, the present invention is not limited to the one embodiment described above, and it goes without saying that various other application examples and modifications can be made without departing from the gist of the present invention described in the claims. . For example, the above-described embodiment is a detailed and specific description of the configuration of an inverter system as a power conversion device in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the components described. . Moreover, it is also possible to add, replace, or delete other components for a part of the configuration of each embodiment.

Further, each of the configurations, functions, processing units, etc. described above may be realized by hardware, for example, by designing a part or all of them using an integrated circuit. As hardware, a broadly defined processor device such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) may be used.

Further, in the above-described embodiments, the control lines and information lines are those considered necessary for explanation, and not all the control lines and information lines are necessarily shown on the product. In practice, it may be considered that almost all components are interconnected.

DESCRIPTION OF SYMBOLS 1... Elevator system, 2... System, 3, 4... Filter circuit, 5... Motor (load), 6... Rope, 7... Car, 8... Weight, 9... Control circuit part, 9a... A/D conversion circuit, 9b Processor 9c Memory 10 Converter system 11 Inverter system 12 to 15 Power conversion unit 21, 31 Capacitor 22, 23, 32, 33 Gate circuit 24, 34 Upper arm switching element , 25, 35 ... lower arm switching element, 26, 36 ... upper arm switching freewheeling diode, 27, 37 ... lower arm switching freewheeling diode, 14, 15 ... power conversion unit, 28, 38 ... resistance load, 29, 39 ... induction 101 Input signal 102 DC power supply 103 GND 104 Resistive load (output load) 105 Inductive load (output load) 106 Current sensor 120 Signal generator (control circuit unit ), 121 temperature accumulation unit 122 ON/OFF time adjustment unit 150 startup compensation period 151 acceleration period 152 constant speed period 153 deceleration period 200, 201 rate of change

Claims (8)

a plurality of power conversion units connected in parallel, each power conversion unit having a first switching element and a second switching element connected in series; a temperature sensor for detecting an internal temperature of each power conversion unit; and a signal generation unit that generates an ON/OFF command signal for the control electrodes of the first switching element and the second switching element for each of the power conversion units according to a detection result of a sensor. hand,
The power conversion device, wherein the signal generation unit uses the temperature sensor to detect the temperature of each power conversion unit when the power conversion device outputs a direct current. The power conversion device according to claim 1, wherein the output time is a start-up compensation period of a motor connected to the power conversion device. The signal generation unit includes a storage device that accumulates detected temperature information of each power conversion unit,
accumulating the output current of the power conversion device and the temperature information of each power conversion unit detected by the temperature sensor, and calculating the change rate of the temperature difference between the power conversion units with respect to the output current from the detection results of a plurality of times; 3. The power converter according to claim 2, wherein the temperature imbalance between the power conversion units is detected by comparing the rate of change of the temperature difference with a threshold value. The signal generator is
4. The power converter according to claim 3, having a function of correcting at least one of turn-on time and turn-off time of said on/off command signal according to the detected temperature imbalance between said power conversion units. The signal generator is
5. A function of correcting at least one of the turn-on time and the turn-off time of the on/off command signal by switching between the first switching element and the second switching element according to the output current of the power conversion device. A power converter as described. The signal generator is
At least one of the turn-on time and the turn-off time of the switching element corresponding to the upper arm among the first switching element and the second switching element is corrected when current is output from the power converter, and when current is drawn into the power converter. 6. The power converter according to claim 5, having a function of correcting at least one of turn-on time and turn-off time of a switching element corresponding to a lower arm among said first switching element and said second switching element. The motor is a hoisting motor that hoists an elevator car using the output of the power conversion device,
The power converter according to claim 2, wherein the hoisting motor is stopped during the output. a plurality of power conversion units connected in parallel, each power conversion unit having a first switching element and a second switching element connected in series; a temperature sensor for detecting an internal temperature of each power conversion unit; and a signal generation unit that generates an ON/OFF command signal for the control electrodes of the first switching element and the second switching element for each power conversion unit according to a detection result of a sensor. A conversion method comprising:
The power conversion method, wherein the signal generator uses the temperature sensor to detect the temperature of each power conversion unit when the power conversion device outputs a direct current.

Images