JP6169459B2 - Power converter and control method - Google Patents

Description

  The present invention relates to a power conversion device and a control method.

  As background art in this technical field, there is JP-A-9-84351 (Patent Document 1). This publication states that “an element failure determination circuit 6 for determining the number of parallel faults of the semiconductor element, and a current reference value of the power converter according to the number of parallel faults of the semiconductor element in response to the element failure determination circuit 6. An overcurrent level for reducing the protection level of the current reference changing circuit 13 for reducing the overcurrent protection circuit that protects the power converter from overcurrent in response to the element failure determination circuit 6 according to the number of parallel faults of the semiconductor elements A power conversion device comprising a change circuit 11-3, which reduces the output current of the power conversion device according to the number of parallel faults of the semiconductor elements and also reduces the overcurrent protection level. " (See summary).

  Moreover, there exists Unexamined-Japanese-Patent No. 2012-125092 (patent document 2). In this publication, “the detected value of the current flowing through the IGBT by the current detector 6 by supplying the current / current controlled to the load 2 by the on / off control of each semiconductor switch element (IGBT) constituting the main circuit of the inverter 1. Is an overcurrent protection device that protects the IGBT from overcurrent when the overcurrent determination level of the IGBT exceeds the overcurrent determination level. The overcurrent determination level variable circuit 3A is configured to detect the overcurrent determination level as the DC voltage Ed of the main circuit decreases. When the comparator 3B determines that the detected current Idet has exceeded the set / adjusted overcurrent determination level Ij, the comparator 3B performs load control by turning off the gate voltage output of the drive circuit 4 and the like. Or the current of the IGBT is cut off "(see summary).

  There is also JP-A-6-105562 (Patent Document 3). In this publication, “the arithmetic device sets the frequency f1 mode in the initial state (S1). Compares the detected current value IP with the threshold value K1 with an appropriate arithmetic cycle (S4). The mode is maintained (S4: N) When the overcurrent occurs, the mode is switched from the frequency f1 mode to the frequency f2 mode (S5), the switching loss is reduced, the heat generation of the switching element is suppressed, and the arithmetic unit is switched to the frequency f2 mode After the switching, the return of IP to the steady range is monitored (S6) .When the steady state is reached (S6: Y), the frequency f1 mode is switched to return to the steady operation (S7) "(see summary) ).

  There is also JP-A-11-69830 (Patent Document 4). This publication states that “the control device 10 is composed of an oscillator 1, a frequency dividing device that divides the output frequency of the oscillator 1 into 1 / N1 or 1 / N2, a carrier wave generation circuit 3, an overload detector 4, and the like. When the load is within the rated range, the overload detector 4 sends an off signal b to the frequency divider 2, and the frequency divider 2 divides the signal a of the oscillator 1 by 1 / N1 to obtain the signal d. The carrier wave generation circuit 3 generates a triangular wave switching frequency and outputs a signal e. In the case of an overload, the overload detector 4 sends an ON signal b to the frequency divider 2 to The frequency device 2 divides the signal a of the oscillator 1 by 1 / N2 and outputs the signal d, and the carrier wave generation circuit 3 outputs the signal e, N1 <N2, and switching loss is reduced by lowering the switching frequency. ”(See summary).

JP-A-9-84351 JP 2012-125092 A JP-A-6-105562 JP-A-11-69830

  In Patent Document 1, in a power conversion device in which each arm is composed of at least a plurality of semiconductor elements connected in parallel, an element failure determination circuit for determining the number of parallel faults of the semiconductor elements and a response to the element failure determination circuit A current reference changing circuit that lowers the current reference value of the power converter according to the number of parallel faults of the semiconductor element, and an overcurrent protection circuit that protects the power converter from overcurrent in response to the element fault determination circuit. An overcurrent level changing circuit for lowering the protection level according to the number of parallel faults of the semiconductor element is provided, and the output current of the power converter is lowered according to the number of parallel faults of the semiconductor element and the overcurrent protection level is also reduced. The mechanism to make it described.

  In the mechanism of Patent Document 1, when an element failure occurs, the parallel number of failure arms of the rectifier decreases, so that the current sharing value of the healthy semiconductor element of the arm where the element failure occurs increases, and the healthy element Therefore, it is difficult to output the rated output of the rectifier. Therefore, the purpose is to provide redundancy (usually one redundancy number) so that the rated output can be continued even when one parallel number of elements fails. However, in the method of Patent Document 1, if the element is to be protected when the element is normal, it is necessary to perform control to reduce the current reference value and the overcurrent level during operation. In some cases, motor torque characteristics are insufficient and tripping is likely to occur. For this reason, when it is different from the purpose described in Patent Document 1, that is, when an element of a power converter in a normal state is targeted, another method is required.

  In Patent Document 2, power / current controlled by a load is controlled by on / off control of each semiconductor switching element constituting a main circuit, and current flowing through the semiconductor switching element is detected directly or indirectly. An overcurrent protection device for a power converter that protects the semiconductor switch element from overcurrent when a value exceeds an overcurrent determination level of the semiconductor switch element, the lower the DC voltage of the main circuit, There is described a mechanism characterized by comprising overcurrent determination level setting / adjustment means for setting / adjusting the current determination level to a high value.

  The mechanism of Patent Document 2 sets and adjusts the overcurrent determination level to a higher value as the DC voltage of the main circuit of the power conversion device is lower. Overcurrent judgment and protection operation can be prevented. However, the method of Patent Document 2 does not consider changes in the temperature of the element, and in order to prevent element destruction, it is necessary to determine an overcurrent level at a safe level with respect to possible environmental temperatures. For this reason, it may be necessary to set the overcurrent level low so that the temperature can be taken safely. In order to limit the current characteristics of the motor drive, the motor torque characteristics may be insufficient or tripping may occur easily. .

  In the above-mentioned Patent Document 3, the heat generation of the element is prevented by reducing the carrier frequency after the overcurrent state is recognized. However, the mechanism of Patent Document 3 describes a method of reducing element loss by lowering the carrier frequency, but does not describe an overcurrent level for preventing element destruction. When the electric power converter drives the electric motor, even if the carrier frequency is lowered, the electric current can only flow up to a current level that does not destroy the switching element, and it is assumed that the electric power converter is driven below that current. For this reason, when the electric current which flows into a power converter device grows sharply, it may lead to destruction of a switching element. For this reason, even if the carrier frequency is lowered, if there is a possibility of returning, if the maximum carrier frequency is high, an extra durable switching element is used, which may increase the product cost.

  In Patent Document 4, in an inverter device including a control device that controls pulse width modulation (PWM), the control device includes an oscillator, a frequency dividing device that divides the output of the oscillator, and a switching frequency of a switching element. It is composed of a carrier wave generation circuit that generates and an overload detection device that detects an overcurrent of the inverter device, and in the normal time when there is no output from the overload detector, the frequency divider has a predetermined frequency set in advance. The frequency divider outputs a frequency lower than the predetermined frequency when there is an overload that is output and the output from the overload detector is present. However, although the mechanism of Patent Document 4 describes a method of reducing element loss by lowering the carrier frequency, it does not describe an overcurrent level for preventing element destruction. When the electric power converter drives the electric motor, even if the carrier frequency is lowered, the electric current can only flow up to a current level that does not destroy the switching element, and it is assumed that the electric power converter is driven below that current. For this reason, when the electric current which flows into a power converter device grows sharply, it may lead to destruction of a switching element. For this reason, even if the carrier frequency is lowered, if there is a possibility of returning, if the maximum carrier frequency is high, an extra durable switching element is used, which may increase the product cost.

  In the case of using an inexpensive switching element while suppressing the electromagnetic noise of the motor during normal operation, the present invention uses a mechanism that prevents the element from being destroyed and drives in a tripless manner, or uses a switching element with a margin. If it does, it aims at providing the mechanism which drives without a trip, preventing destruction of an element and utilizing the power conversion performance of a power converter device to the maximum.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-described problems. For example, a power converter that converts a DC voltage into a desired AC voltage, and a current output from the power converter are detected. A current detector and a control circuit for controlling on / off of the switching element of the power converter, the control circuit controls the carrier frequency based on the current detected by the current detector, and sets the carrier frequency to The overcurrent level is set on the basis of this.

  ADVANTAGE OF THE INVENTION According to this invention, the power converter device and control method which made it possible to extend the use range of a power converter device, preventing destruction of a switching element are provided. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the block diagram of the power converter device in Example 1,2. It is the example which showed the electric current, voltage, and loss characteristic of a switching element. FIG. 6 is a diagram showing the relationship between the carrier frequency fsw and the collector current Ic and the change in the collector-emitter voltage Vce when the loss P is constant. 4 is a flowchart for determining overcurrent determination, carrier frequency change, and overcurrent level change in the first embodiment. 4 is a flowchart of carrier frequency change in the first embodiment. It is the example which showed the relationship between the carrier frequency fc in Example 1, the electric current I, an overcurrent level, and a reduction level. It is a flowchart which judges the overcurrent determination in Example 2, a carrier frequency change, and an overcurrent level change. 10 is a flowchart of carrier frequency change in the second embodiment. It is the example which showed the relationship between the carrier frequency fc and the electric current I in Example 2, and an overcurrent level and a reduction level.

  Hereinafter, examples will be described with reference to the drawings.

  In the present embodiment, when the current detected by the power converter increases, carrier reduction is performed to suppress the heat generation of the element, and at the same time, the overcurrent level setting is changed to maximize the usage range of the element, An example will be described in which when an overcurrent occurs instantaneously, a cutoff is performed to prevent destruction of the element.

  FIG. 1 is an example of a configuration diagram in which an AC motor 103 is connected to the power conversion device of the present embodiment.

  In the present embodiment, a DC smoothing unit 101, a power conversion unit 102, an AC motor 103, a current detector 104, a control circuit unit 105, a current detection unit 106, a voltage detection unit 107, a control command unit 108, and a voltage detector 109 are provided. .

  The DC smoothing unit 101 is configured by, for example, a smoothing capacitor, and smoothes a DC voltage supplied from a generator or a DC voltage supplied from a generator to, for example, a three-phase AC voltage supplied from an electric power company, and converts the DC voltage into power. To the unit 102. Further, the DC smoothing unit 101 outputs a DC voltage value to the voltage detection unit 107 of the control circuit 105.

  The power conversion unit 102 includes switching elements such as IGBTs, MOSFETs, and GTOs, for example, receives the DC voltage of the DC smoothing unit 101 as input, converts the DC voltage into AC voltage, and outputs the AC voltage to the AC motor 103. The AC motor 103 may be an induction motor or a synchronous motor, and may be connected to an AC power source.

  The current detector 104 is composed of, for example, a Hall CT or a shunt resistor, and is arranged at the output unit of the power conversion device to detect the current flowing through the AC motor 103, and the current detection unit 106 of the control circuit unit 105 detects the current. Output as a value. The current detector 104 may be disposed anywhere as long as the collector current Ic flowing through the switching element can be estimated or directly detected. FIG. 1 shows an example in which the current flowing through the AC motor 103 is detected.

  The control circuit unit 105 is configured by software and hardware circuits mounted on an MCU, for example. The control circuit unit 105 may be configured only by hardware, or may be configured by a storage element or other IC element.

  The current detection unit 106 outputs the current detection value input from the current detector 104 to the control command unit 108 as output current data. The data output from the current detection unit 104 may be a three-phase current or a DC current converted as a primary current.

  The voltage detector 109 is a voltage detection circuit that divides a DC voltage using, for example, a resistor and inputs the voltage to the MCU. The voltage detection value input from the DC smoothing unit 101 is used as the DC voltage data. To the voltage detection unit 107. The voltage detector 109 may directly detect the collector-emitter voltage Vce of the switching element.

  The voltage detection unit 107 outputs the voltage detection value input from the voltage detector 109 to the control command unit 108 as DC voltage data.

  The control command unit 108 receives current data from the current detection unit 106 and DC voltage data from the voltage detection unit 107, determines a carrier frequency based on the current information, and outputs element on / off information to the power conversion unit 102. In addition, the control command unit 108 determines an overcurrent level from the carrier frequency and the DC voltage data, compares the current data with the overcurrent level, and shuts off the output of the element when the current data exceeds the overcurrent level. .

  FIG. 2 shows the relationship between the collector current Ic flowing through the transistor of the switching element, the collector-emitter voltage Vce, and the element loss P at that time. For example, the detected current data is used as the collector current Ic flowing through the transistor. For example, the collector-emitter voltage Vce flowing through the transistor uses data obtained by halving the DC voltage data. The loss P is expressed by the following equation using the switching loss Psw and the steady loss Psat.

  The switching loss Psw is expressed by the following equation using the carrier frequency fsw, the carrier period T, the turn-on current ion (t), the turn-on voltage von (t), the turn-off current ioff (t), and the turn-off voltage voff (t). It is represented by

  The steady loss Psat is expressed by the following equation using one carrier cycle T, on-current i (t), on-voltage v (t), and on-duty D.

  In the calculation of steady loss, even though the switching element is turned off, loss occurs due to the influence of leakage current or the like, but this is not considered here because it is minute.

  FIG. 3 is a diagram showing the relationship between the carrier frequency fsw and the collector current Ic when the loss P is made constant based on the above equation. IGBT, MOSFET, GTO, etc., which are switching elements of power converters, increase the temperature of the element when the loss P increases, resulting in thermal breakdown exceeding the maximum junction temperature, which is the absolute rating of the element, or thermal breakdown Even if not, the lifetime is shortened due to the generation of the temperature gradient of the element, leading to the power cycle life. Since the steady loss Psat does not depend on the carrier frequency fsw with respect to the carrier frequency fsw, the steady loss Psat becomes a constant value due to the collector current Ic, sat and the collector-emitter voltage Vce, sat. The switching loss Psw depends on the carrier frequency fsw, the collector current Ic, on and the collector-emitter voltage Vce, on when the switching element is turned on, the collector current Ic, off and the collector-emitter voltage Vce, off when the switching element is turned off. The allowable collector current Ic increases as the carrier frequency fsw decreases. When the collector-emitter voltage Vce increases, the allowable level of the collector current Ic decreases accordingly, and when the collector-emitter voltage Vce decreases, the collector-emitter voltage Vce decreases accordingly. Accordingly, the allowable level of collector current Ic increases. The conditions relating to the lifetime and withstand capability of these elements may be calculated from element information obtained from the switching element manufacturer, or may be actually measured.

  In this embodiment, when the current increases, the switching loss of the element is suppressed by reducing the carrier, and when the current needs to flow by changing the overcurrent level according to the carrier reduction, for example, the torque of the AC motor When the device is required, the overcurrent level increases according to the loss curve related to the lifetime and breakdown of the device, so that the device can be used to the maximum extent and when an overcurrent occurs instantaneously. Describes a method of blocking in order to prevent thermal destruction of the element.

  FIG. 4 illustrates a method in which the control command unit 109 changes the carrier frequency and performs overcurrent determination. The control command unit 109 first acquires current data from the current detection unit 106 (S201), and determines whether or not the carrier frequency needs to be changed (S202). When it is determined that the carrier frequency needs to be changed, the carrier frequency is changed according to the current data (S203), and is output as a command to the switching element of the current conversion unit 102, and the changed carrier frequency and the acquired DC voltage The overcurrent level is changed according to the data (S204). Thereby, the loss of the switching element is reduced, that is, the current control range is maximized while suppressing the temperature rise of the element. As a method of changing the carrier frequency according to the current data and changing the overcurrent level according to the carrier frequency, for example, a storage element such as a ROM is prepared, and a loss curve related to the lifetime / destruction of the element is converted in advance. And may be changed by referring to the table at the time of change, or may be changed by causing the MCU or the like to calculate a loss curve related to the lifetime / destruction of the element. Next, the control command unit 109 compares the output current data with the changed overcurrent level in order to protect the switching element from an instantaneous current jump and prevent a temperature rise due to a sudden increase in loss ( If the output current data exceeds the overcurrent level (S205), the power conversion unit is cut off as a command (S206).

  FIG. 5 illustrates a method in which the control command unit 109 determines in FIG. 4 (S202). The control command unit 109 first acquires current data from the current detection unit 106 (S301). The control command unit 109 compares the acquired current data with the carrier frequency fc determination level a (S302). If the acquired current data exceeds the carrier frequency fc determination level a, the control command unit 109 decreases the carrier frequency (S303). . Next, the acquired current data is compared with the carrier frequency fc determination level b (S304), and if the acquired current data is below the carrier frequency fc determination level b, the carrier frequency is increased (S305). Carrier frequency fc determination levels a and b to be compared with current data are stored in advance as a conversion table of a loss curve related to the lifetime / destruction of the element, and may be changed by referring to the table when changing, The loss curve related to the lifetime / destruction of the element may be changed by causing the MCU or the like to calculate it. In addition, the intention of dividing the carrier frequency fc determination levels a and b is to consider the effect when the carrier frequency fluctuates due to fluctuations in the output current, so that the carrier frequency fc determination level is a> b. Is provided with hysteresis. The relationship of the carrier frequency fc determination level may be a = b.

  FIG. 6 shows an operation when the DC voltage data is substantially constant and the current data I acquired by the current detection unit 106 (here, for example, the primary current) increases. The control command unit 109 secures a life required for an instantaneous current increase ((1)) and a steady current increase ((2)) from a loss curve related to the life / destruction of the element calculated in advance. It shows how the carrier frequency fc is lowered while monitoring the current data I according to the curve data that can be used (dotted line). The loss curves related to the lifetime / destruction of these elements may be calculated from element information obtained from the switching element manufacturer, or may be measured. When the maximum current that can be flowed as the power converter is 10 A, the control command unit 109 decreases the carrier frequency along the dotted line as the current increases from the carrier frequency setting of 20 kHz. Can be used up to the maximum current (reach (3) in FIG. 6). In addition, the control command unit 109 sets the overcurrent level according to the carrier frequency at that time for the purpose of protecting the element when the carrier reduction speed is slow with respect to current growth, for example, when the calculation capacity of the MCU is low. When it reaches, it is determined as an overcurrent, and a cutoff command is sent to the power converter 102 ((4) in FIG. 6). Also, if the control command unit 109 proceeds to decrease before the current data reaches the overcurrent level, the control command unit 109 restores the carrier frequency accordingly.

  As described above, when the current increases, the carrier is reduced to suppress the heat generation of the element, and at the same time, the overcurrent level setting is changed to maximize the usage range of the element and instantaneously overcurrent. If this happens, it is shut off to prevent destruction of the device.

  As described above, in the power conversion device according to the present embodiment, in a state where the current or DC voltage detected by the power conversion device is low, the motor electromagnetic noise is suppressed low by keeping the carrier frequency high, and the motor control voltage Power conversion device that stabilizes motor control by speeding up the update cycle, lowers the carrier frequency and increases the overcurrent level or overvoltage level in a state where the current or DC voltage is high, and prevents the destruction of the switching element There is an effect that it is possible to widen the use range of. In addition, an inexpensive switching element can be used to the maximum, and the cost can be suppressed.

  In this embodiment, when the current or DC voltage detected by the power converter or both the current and DC voltage increases, the carrier is reduced to suppress the heat generation of the element, and at the same time, the loss applied to the element is judged and cut off. Explains an example in which the maximum operating range of the element can be achieved by making changes, and when loss increases instantaneously, for example, when overcurrent or overvoltage occurs, the element is shut down to prevent element destruction To do. In the present embodiment, the description of the components with the same reference numerals as those in the drawings of the first embodiment is omitted, and only the configuration having an operation different from that of the first embodiment will be described.

  The second embodiment has the same configuration as that of the first embodiment, for example, as shown in FIG.

  In the present embodiment, the description of the components with the same reference numerals as those in the drawing of the first embodiment is omitted, and only the configuration having an action different from that of the first embodiment will be described.

  The control command unit 108 receives the current data from the current detection unit 106 and the DC voltage data from the voltage detection unit 107, determines the carrier frequency based on the current information and the voltage information, and converts the element on / off information into the power conversion unit 102. Output to. Further, the control command unit 108 determines the overcurrent level or the overvoltage level from the result of selectively adopting the carrier frequency, the current data, or the DC voltage data, and sets the current data, the overcurrent level, the DC voltage data, and the overvoltage level. In comparison, when the current data exceeds the overcurrent level or when the DC voltage data exceeds the overvoltage level, the output of the element is cut off.

  In this embodiment, when the current or DC voltage increases, the increase in switching loss of the element is suppressed by the carrier reduction, and the current is passed by changing the overcurrent level or the overvoltage level according to the carrier reduction and the referenced data. When necessary, for example, when the torque of the AC motor is required, or when the DC voltage rises, for example, when regenerative power returns from the AC motor, the loss curve related to the lifetime and breakdown of the element can be obtained. The overcurrent level or overvoltage level rises accordingly, so that the device can be used to the maximum extent, and when an overcurrent or instantaneous overvoltage occurs instantaneously, the device is shut down to prevent thermal destruction of the device. A method will be described.

  FIG. 7 shows a method in which the control command unit 109 changes the carrier frequency and determines overcurrent and overvoltage. The control command unit 109 first acquires current data from the current detection unit 106 and DC voltage data from the voltage detection unit 107 (S401), and determines whether or not the carrier frequency needs to be changed (S402). It is stored in a storage element such as a RAM, for example, whether the cause of the change in the carrier frequency is current data, DC voltage data, or both. Next, the control command unit 109 changes the carrier frequency (S403). For example, when the carrier frequency is changed by current data due to the necessity of changing the carrier frequency, the overvoltage level is changed by the DC voltage data. When the carrier frequency is changed, the overcurrent level is used, or the product of DC current data and current data is used as load power data, and the cutoff level calculated from the loss thymus is determined (S404). Alternatively, the control command unit 109 may determine each cutoff level according to the carrier frequency so that it can be blocked when the loss increases. The control command unit 109 compares the changed overcurrent level and current data, or the changed overvoltage level and DC voltage level, or the load power and cutoff level (S405), and the current data exceeds the overcurrent level. Alternatively, when the DC voltage data exceeds the overvoltage level or the load power exceeds the cutoff level, the output of the power conversion unit 102 is cut off (S406).

  FIG. 8 illustrates an example in which the control command unit 109 performs carrier frequency determination from loss data as a method of determination in FIG. 7 (S402). First, the control command unit 109 acquires current data from the current detection unit 106 and DC voltage data from the voltage detection unit 107, and calculates a product of the current data and the DC voltage data as load power data (S501). The control command unit 109 compares the calculated load power data with the carrier frequency fc determination level c (S502). If the calculated load power data exceeds the carrier frequency fc determination level c, the control command unit 109 decreases the carrier frequency ( S503). Next, the calculated load power data is compared with the carrier frequency fc determination level d (S504). If the calculated load power data is below the carrier frequency fc determination level d, the carrier frequency is increased (S505). The carrier frequency fc determination levels c and d to be compared with the load power data may be changed by previously storing a loss curve relating to the lifetime / destruction of the element as a conversion table and referring to the table when changing the carrier curve. The loss curve related to the lifetime / destruction of the element may be changed by causing the MCU or the like to calculate it. In addition, the intention of dividing the carrier frequency fc determination levels c and d is to consider the effect when the carrier frequency fluctuates due to fluctuations in the calculated load power data, and the carrier frequency fc determination level is c> d Hysteresis is provided so that The relationship of the carrier frequency fc determination level may be c = d. The method of determination in FIG. 7 (S402) is the same as that of FIG. 5 of the first embodiment except that only current data is determined and the current / overcurrent portion of FIG. 5 is replaced with a value corresponding to the DC voltage / overvoltage level. Alternatively, only the DC voltage data may be determined, or the respective determinations may be determined at the same time.

  FIG. 9 shows the operation when the power loss W, which is the product of the current data I acquired by the current detection unit 106 (here, for example, the primary current) and the DC voltage data acquired by the voltage detection unit 107, is increased. ing. The control command unit 109 secures a life required for an instantaneous loss increase ((1)) and a steady loss increase ((2)) from a loss curve relating to the life / destruction of the element calculated in advance. It shows how the carrier frequency fc is lowered while monitoring the power loss W according to the curve data that can be used (dotted line). The loss curves related to the lifetime / destruction of these elements may be calculated from element information obtained from the switching element manufacturer, or may be measured. When the maximum loss that can be flowed as a power converter is 2 kW, the control command unit 109 reduces the carrier frequency along the dotted line when the power loss W increases from the carrier frequency setting of 20 kHz. It becomes possible to use up to the maximum current (going to (3) in FIG. 9). In addition, the control command unit 109, for example, when the calculation capacity of the MCU is low, when the carrier reduction rate is slow with respect to current growth or DC voltage growth, for the purpose of protecting the element, according to the carrier frequency at that time, When the loss power exceeds the loss cutoff level, a cutoff command is sent to the power converter 102 ((4) in FIG. 9). For example, as shown in FIG. 6, the control command unit 109 may compare and judge the overcurrent level and current data output from the carrier frequency and DC voltage data, and send a cutoff command to the power conversion unit 102. The relationship between the voltage and current may be switched, the overvoltage level derived from the carrier frequency and current data may be compared with the DC voltage data, and a cutoff command may be sent to the power converter 102.

  As described above, when the current or DC voltage increases, the carrier is reduced to suppress the heat generation of the element, and at the same time the element usage range is maximized by changing the loss level, overcurrent level, and overvoltage level settings. In the event that an abnormality occurs instantaneously, the device is shut down to prevent element destruction.

In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines are those that are considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 101 ... DC smoothing part, 102 ... Power conversion part, 103 ... AC electric motor, 104 ... Current detector, 105 ... Control circuit part, 106 ... Current detection part, 107 ...・ Voltage detector 108, control command unit 109, voltage detector

Claims (10)

A DC smoothing unit for smoothing the DC voltage;
A power converter that converts a DC voltage into a desired AC voltage;
A current detector for detecting a current output from the power converter;
A voltage detector for detecting the voltage of the DC smoothing unit;
A control circuit for controlling on / off of the switching element of the power converter;
With
The control circuit controls a carrier frequency based on the current detected by the current detector, the voltage detected by the voltage detector, or both the detected current and the detected voltage, and the carrier frequency or An overvoltage level or an overcurrent level is set based on a result of selectively adopting the detected current or the detected voltage. The power conversion device according to claim 1 ,
The control circuit reduces the carrier frequency when the current value detected by the current detector exceeds a predetermined value. The power converter according to claim 1 or 2 ,
The control circuit reduces the carrier frequency when the voltage value detected by the voltage detector exceeds a predetermined value. The power conversion device according to any one of claims 1 to 3 ,
When the carrier frequency is lowered, the control circuit raises an overcurrent level accordingly. The power conversion device according to any one of claims 1 to 4 ,
The control circuit stores in advance the relationship between the detected current, the detected voltage, the carrier frequency, the overcurrent level, and the overvoltage level. A DC smoothing unit for smoothing the DC voltage;
A power converter that converts a DC voltage into a desired AC voltage;
A current detector for detecting a current output from the power converter;
A voltage detector for detecting the voltage of the DC smoothing unit;
A control circuit for controlling on / off of the switching element of the power converter;
A control method in a power converting apparatus Ru provided with,
The control circuit controls a carrier frequency based on the current detected by the current detector, the voltage detected by the voltage detector, or both the detected current and the detected voltage, and the carrier frequency or An overvoltage level or an overcurrent level is set based on a result of selectively adopting the detected current or the detected voltage. The control method according to claim 6 , comprising:
The control method, wherein the control circuit lowers the carrier frequency when the current value detected by the current detector becomes a predetermined value or more. The control method according to claim 6 or 7 , comprising:
The control method, wherein the control circuit lowers a carrier frequency when a voltage value detected by the voltage detector becomes a predetermined value or more. A control method according to any one of claims 6 to 8 ,
The control circuit, when the carrier frequency is lowered, the control method characterized by increasing the over-current level accordingly. A control method according to any one of claims 6 to 9 ,
The control circuit stores in advance a relationship between the detected current, the detected voltage, the carrier frequency, the overcurrent level, and the overvoltage level.

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