JP6939094B2 - Power converter control device and refrigeration device - Google Patents

Description

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

A power conversion device having an LC filter in the DC link portion has been proposed. Specifically, the power conversion device includes a diode bridge and an inverter connected in series with each other via a DC link unit. The diode bridge converts the input AC voltage into a DC voltage and outputs the DC voltage to the DC link unit.

The DC link unit is composed of a pair of DC lines. A capacitor is connected between the pair of DC lines. A reactor is provided on one of the pair of DC bus wires between the capacitor and the diode bridge. The reactor and capacitor form an LC filter.

The inverter converts the voltage across the capacitor into an AC voltage and outputs this AC voltage to, for example, an electric motor.

Patent Documents 1 to 3 are posted in relation to the present invention.

Japanese Unexamined Patent Publication No. 2015-84637 Japanese Unexamined Patent Publication No. 2015-145742 Japanese Unexamined Patent Publication No. 2010-175194

When the current flowing through the reactor changes with time, an eddy current corresponding to the change flows to the core of the reactor, and the reactor generates heat due to this eddy current.

Therefore, an object of the present invention is to provide a control device and a refrigerating device for a power conversion device capable of suppressing an increase in the calorific value of the reactor.

The first aspect of the control device of the power conversion device according to the present invention is a plurality of input terminals (P11, P12) connected to an AC power supply, a pair of DC lines (LH, LL), and a plurality of output ends (P11, P12). Pu, Pv, Pw), connected between the plurality of input ends and the pair of DC lines, and connected between the rectifying circuit (1) that performs AC / DC conversion and the pair of DC lines. Between the capacitor (C1), the reactor (L1) provided on one (LH) of the pair of DC lines between the capacitor and the rectifying circuit, and between the pair of DC lines and the plurality of output ends. A device that controls a power conversion device that is connected and includes an inverter (2) that performs DC / AC conversion. The voltage detection unit (4) that detects the voltage (VL) of the reactor and the voltage detection unit To control the direct current so as to reduce the AC power output by the direct current when the first condition that the detected absolute value of the voltage (VL) is larger than the voltage reference value (Vref) is satisfied. It is equipped with a control unit (3) that executes power reduction control that generates the control signal of.

The second aspect of the control device of the power conversion device according to the present invention is the control device of the power conversion device according to the first aspect, and the control unit (3) is said to be via the plurality of input ends. When both the second condition that the amplitude (im) of the alternating current input to the rectifier circuit (1) is larger than the amplitude reference value (iref) and the first condition are satisfied, the power reduction control is performed. Run.

The third aspect of the control device of the power conversion device according to the present invention is the control device of the power conversion device according to the first or second aspect, and the control unit (3) is the first condition. Is repeatedly determined, and when the number of times (N) of the first condition being satisfied within the predetermined time is larger than the predetermined number of times (Nref), the power reduction control is executed.

The fourth aspect of the control device of the power conversion device according to the present invention is the control device of the power conversion device according to the third aspect, and the control unit (3) has started the execution of the power reduction control. Later, when the number of times the first condition is satisfied (N) within the predetermined time is less than the predetermined number of times (Nref), the power reduction control is terminated.

The refrigerating device according to the present invention includes a control device for a power conversion device according to any one of the first to fourth aspects, and the power conversion device.

According to the first aspect of the control device of the power conversion device and the refrigerating device according to the present invention, the first condition that the absolute value of the voltage of the reactor is larger than the voltage reference value is satisfied, and the power reduction control is executed. Therefore, the AC power output from the inverter is reduced. Along with this, the current flowing through the reactor is also reduced. As a result, the eddy current flowing through the core of the reactor can be reduced, and the heat generated in the reactor can be suppressed. Therefore, when the current flowing through the reactor is distorted and the calorific value of the reactor increases, the power reduction control is executed to suppress the increase in the calorific value.

According to the second aspect of the control device of the power conversion device according to the present invention, the power reduction control can be executed when the calorific value of the reactor is remarkably increased.

According to the third aspect of the control device of the power conversion device according to the present invention, reduction of output power due to noise can be suppressed or avoided.

According to the fourth aspect of the control device of the power conversion device according to the present invention, it is possible to suppress or avoid an increase in the period during which the AC power is reduced.

It is a figure which shows typically an example of the structure of a refrigerating apparatus. It is a figure which shows typically an example of the structure of the power conversion apparatus. It is a figure which shows typically an example of the AC voltage input to a rectifier circuit, the current flowing through a reactor, and the voltage applied to a reactor. It is a figure which shows typically an example of the AC voltage input to a rectifier circuit, the current flowing through a reactor, and the voltage applied to a reactor. It is a flowchart which shows an example of the operation of a control part. It is a figure which shows typically an example of the AC voltage input to a rectifier circuit, the current flowing through a reactor, and the voltage applied to a reactor. It is a flowchart which shows an example of the operation of a control part. It is a flowchart which shows an example of the operation of a control part. It is a figure which shows typically an example of the structure of the power conversion apparatus.

The first embodiment.
<1. Freezer ＞
FIG. 1 is a diagram schematically showing an example of a configuration of a refrigerating device to which the power conversion device according to the present embodiment can be applied. The refrigerating device 100 is also called a heat pump unit, and is used in equipment such as a dedicated refrigerating machine, an air conditioner, or a water heater. The air conditioner will be described below as an example. The refrigerating device 100 includes a user-side unit 200 and a heat source-side unit 300. The user-side unit 200 is arranged indoors, and the heat source-side unit 300 is arranged outdoors.

The user-side unit 200 includes, for example, a heat exchanger 210, a fan 220, and a control unit 250. The heat source side unit 300 includes, for example, a heat exchanger 310, an expansion valve 360, a fan 320, a compressor 330, a four-way valve 340, and a control unit 350. The heat exchangers 210 and 310, the expansion valve 360, the compressor 330, and the four-way valve 340 form a refrigerant circuit.

The compressor 330 has a suction port 331 and a discharge port 332. The compressor 330 sucks the refrigerant from the suction port 331, compresses the sucked refrigerant, and discharges it from the discharge port 332. The compressor 330 has an electric motor, and the compression operation is performed by the rotation of the electric motor.

The four-way valve 340 is connected to the suction port 331 and the discharge port 332 of the compressor 330, one end 211 of the heat exchanger 210, and one end 311 of the heat exchanger 310 via a refrigerant pipe, respectively. The four-way valve 340 selectively connects the suction port 331 of the compressor 330 to either one of the one end 211 of the heat exchanger 210 and the one end 311 of the heat exchanger 310, and connects the discharge port 332 to the other.

One end of the expansion valve 360 is connected to the other end 212 of the heat exchanger 210 via a refrigerant pipe, and the other end of the expansion valve 360 is connected to the other end 312 of the heat exchanger 310 via a refrigerant pipe. The expansion valve 360 throttles and expands the refrigerant.

The fan 220 blows air to the heat exchanger 210 to promote heat exchange of the heat exchanger 210, and blows out the air after the heat exchange into the room. The fan 320 blows air to the heat exchanger 310 to promote heat exchange in the heat exchanger 310. The fans 220 and 320 have an electric motor, and the fans 220 and 320 blow air when the electric motor rotates.

The control units 250 and 350 are communicably connected to each other and cooperate with each other to control the refrigerating apparatus 100. The control unit 250 controls various configurations of the user-side unit 200 (for example, fan 220), and the control unit 350 controls various configurations of the heat source-side unit 300 (for example, fan 320, expansion valve 360, compressor 330, and four-way valve 340). do.

The refrigerating device 100 executes a cooling operation for cooling the air in the room. In this cooling operation, the control units 250 and 350 communicate with each other to control the above components. For example, the control unit 350 controls the four-way valve 340 to connect the suction port 331 of the compressor 330 to one end 211 of the heat exchanger 210 and the discharge port 332 of the compressor 330 to one end 311 of the heat exchanger 310. .. As a result, the heat exchanger 210 of the user-side unit 200 can function as an evaporator, and the heat exchanger 310 of the heat source-side unit 300 can function as a condenser. Therefore, the heat exchanger 210 of the user-side unit 200 absorbs heat from the indoor air to cool the indoor air. Further, in the cooling operation, the control units 250 and 350 rotate the fans 220 and 320, respectively. Since the air from the fan 220 of the user-side unit 200 is supplied to the room via the heat exchanger 210, cooling of the room can be promoted.

Further, the freezing device 100 executes a heating operation for warming the air in the room. In this heating operation, the control units 250 and 350 communicate with each other to control the above components. For example, the control unit 350 controls the four-way valve 340 to connect the suction port 331 of the compressor 330 to one end 311 of the heat exchanger 310 and the discharge port 332 of the compressor 330 to one end 211 of the heat exchanger 210. .. As a result, the heat exchanger 210 of the user-side unit 200 can function as a condenser, and the heat exchanger 310 of the heat source-side unit 300 can function as an evaporator. Therefore, the heat exchanger 210 of the user-side unit 200 releases heat to the indoor air to warm the indoor air. Also in the heating operation, the control units 250 and 350 rotate the fans 220 and 320, respectively. Since the air from the fan 220 is supplied to the room via the heat exchanger 210, heating in the room can be promoted.

<2. Power converter ＞
FIG. 2 is a block diagram showing an example of the configuration of the power conversion device 10. The power conversion device 10 is provided in, for example, the refrigeration device 100. The power conversion device 10 outputs an AC voltage to, for example, the electric motor M1 provided in any of the fans 220 and 320 and the compressor 330 to drive the electric motor M1.

The power conversion device 10 includes a plurality of input terminals P11, P12, a pair of DC lines LH, LL, a plurality of output terminals Pu, Pv, Pw, a rectifier circuit 1, a capacitor C1, a reactor L1, and an inverter 2. And have.

The AC power supply E1 is connected to the input terminals P11 and P12. The AC power supply E1 is, for example, a commercial single-phase AC power supply, and an AC voltage is applied between the input terminals P11 and P12.

The rectifier circuit 1 is connected between the input terminals P11 and P12 and the pair of DC lines LH and LL to perform AC / DC conversion. Specifically, the rectifier circuit 1 converts the AC voltage input via the input terminals P11 and P12 into a DC voltage, and applies the DC voltage between the pair of DC lines LH and LL. The rectifier circuit 1 is, for example, a diode rectifier circuit. The rectifier circuit 1 has, for example, a diode bridge, and full-wave rectifies the AC voltage.

In the example of FIG. 1, the AC power supply E1 is a single-phase AC power supply and the rectifier circuit 1 is a single-phase rectifier circuit. It may be a rectifier circuit.

The capacitor C1 is connected between a pair of DC lines LH and LL. The reactor L1 is provided on the DC line LH between the capacitor C1 and the rectifier circuit 1. The reactor L1 has a core (not shown) and a winding (not shown) wound around the core. The reactor L1 and the capacitor C1 form a so-called LC filter. The reactor L1 may be provided on the DC line LL between the capacitor C1 and the rectifier circuit 1.

This LC filter can reduce current noise caused by switching of the inverter 2, for example. The inductance of the reactor L1 and the capacitance of the capacitor C1 are set small, for example. As a result, the power conversion device 10 can be miniaturized. Since the capacitance of the capacitor C1 is small, the DC voltage applied to the capacitor C1 fluctuates due to the AC voltage. Conversely, the capacitance of the capacitor C1 is set to such an extent that the DC voltage fluctuates according to the fluctuation of the AC voltage. For example, when the rectifier circuit 1 full-wave rectifies a single-phase AC voltage, the DC voltage pulsates at a frequency twice that of the AC voltage.

The inductance of the reactor L1 is set to, for example, about several hundred [μH], and the capacitance of the capacitor C1 is set to, for example, about several tens [μF].

The inverter 2 is connected between the pair of DC lines LH, LL and the output terminals Pu, Pv, Pw, and performs DC / AC conversion. In the example of FIG. 2, the voltage across the capacitor C1 is input to the inverter 2 as a DC voltage. The inverter 2 converts this DC voltage into a three-phase AC voltage, and outputs the three-phase AC voltage to the output terminals Pu, Pv, and Pw.

The inverter 2 includes, for example, switching elements S1 to S6 and diodes D1 to D6. Each of the switching elements S1, S3, and S5 is, for example, a transistor, and is connected between each of the output terminals Pu, Pv, and Pw and the DC line LH. Each of the switching elements S2, S4, and S6 is, for example, a transistor, and is connected between each of the output terminals Pu, Pv, and Pw and the DC line LL. The diodes D1 to D6 are connected in parallel to the switching elements S1 to S6, respectively. The forward direction of the diodes D1 to D6 is the direction from the DC line LL to the DC line LH.

The output terminals Pu, Pv, and Pw are connected to the motor M1. The electric motor M1 may be, for example, an electric motor provided in the compressor 330, or may be, for example, an electric motor provided in either one of the fans 220 and 320. The electric motor M1 rotates according to the AC voltage input from the inverter 2.

The control device that controls the power conversion device 10 includes a control unit 3 and a voltage detection unit 4. The control unit 3 includes, for example, a main control unit 30 and a motor control unit 31. For example, the main control unit 30 is the control unit 350 of the heat source side unit 300 when the power conversion device 10 drives the motor M1 of the fan 320 or the compressor 330, and the power conversion device 10 drives the motor M1 of the fan 220. When driving, it is the control unit 250 of the user-side unit 200. The main control unit 30 outputs a command value for the motor M1 (for example, a rotation speed command value ω * for the rotation speed ω of the motor M1) to the motor control unit 31.

The motor control unit 31 generates a control signal S based on a command value from the main control unit 30, and outputs this control signal to the inverter 2 (specifically, switching elements S1 to S6). Although a known method may be adopted as the method for generating the control signal S, an example of a method for feedback-controlling the rotation speed ω will be briefly described below.

In the example of FIG. 2, a current detection unit 5 for detecting the AC currents iu, iv, and iwa output by the inverter 2 is provided. The motor control unit 31 calculates the rotation speed ω of the motor M1 based on the alternating currents iu, iv, and iwa detected by the current detection unit 5. In the example of FIG. 2, although the current detection unit 5 is provided on the output side of the inverter 2, the current detection unit may be provided on the input side of the inverter 2. This current detection unit detects the DC current flowing through the DC line LH or the DC line LL on the inverter 2 side of the capacitor C1, and outputs the detected value to the motor control unit 31. The motor control unit 31 detects the alternating currents iu, iv, iv by associating the direct current with the alternating currents iu, iv, iwa based on the switching patterns of the switching elements S1 to S6 of the inverter 2. Such a detection method is also called a one-shunt method.

Next, the motor control unit 31 calculates the deviation between the rotation speed command value ω * and the rotation speed ω, and performs proportional integral control with respect to the deviation to generate the current command value. This current command value is a command value for the alternating current output by the inverter 2. Next, the motor control unit 31 generates a voltage command value from the current command value using, for example, the voltage equation of the motor M1. This voltage command value is a command value for the AC voltage output by the inverter 2. The motor control unit 31 compares the voltage command value with the carrier wave (triangle wave) to generate the control signal S. The frequency of the carrier wave is set to, for example, a number (for example, 5.9) [kHz]. The motor control unit 31 outputs this control signal S to the inverter 2.

The inverter 2 converts a DC voltage into an AC voltage based on the control signal S, and outputs this AC voltage to the motor M1. As a result, the rotation speed ω of the electric motor M1 is controlled based on the rotation speed command value ω *.

Here, the main control unit 30 and the motor control unit 31 are configured to include a microcomputer and a storage device. The microcomputer executes each processing step (in other words, a procedure) described in the program. The storage device is composed of one or a plurality of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), a rewritable non-volatile memory (EPROM (Erasable Programmable ROM), etc.), and a hard disk device. It is possible. The storage device stores various information, data, and the like, stores a program executed by a microcomputer, and provides a work area for executing the program. It should be noted that the microcomputer can be grasped as functioning as various means corresponding to each processing step described in the program, or can be grasped as realizing various functions corresponding to each processing step. Further, the main control unit 30 and the motor control unit 31 are not limited to this, and various procedures executed by the main control unit 30 or the motor control unit 31, or various means or various functions to be realized are partially or entirely hardware. It may be realized with.

The voltage detection unit 4 detects the voltage VL applied to the reactor L1 and outputs the detected value to the control unit 3. In the example of FIG. 1, the voltage detection unit 4 includes resistors R1 to R6. The resistors R1 to R3 are connected in series with each other between the end of the reactor L1 on the rectifier circuit 1 side and the DC line LL, and the resistors R4 to R6 are connected to the end of the reactor L1 on the inverter 2 side and the DC line LL. They are connected in series with each other. The resistors R1 to R3 are arranged in this order in the direction from the DC line LH to the DC line LL, and the resistors R4 to R6 are arranged in this order in the direction from the DC line LH to the DC line LL. The ratio of the combined resistance value of the resistors R1 and R2 to the resistance value of R3 is set to be substantially equal to the ratio of the combined resistance value of the resistors R4 and R5 and the resistance value of the resistor R6. The connection point P41 connecting the resistors R2 and R3 and the connection point P42 connecting the resistors R5 and R6 are each connected to the control unit 3 (more specifically, the motor control unit 31). The voltage between the connection points P41 and P42 is input to the motor control unit 31 as a value proportional to the voltage VL. Since the resistors R1 to R6 function as voltage dividing resistors, the voltage value input to the motor control unit 31 can be reduced.

FIG. 3 is a diagram schematically showing an example of an AC voltage Vin input to the rectifier circuit 1, a current iL flowing through the reactor L1, and a voltage VL of the reactor L1. The AC voltage Vin has a sinusoidal shape. The current iL ideally corresponds to the absolute value of a sine wave. Since the voltage VL is represented by the product of the inductance of the reactor L and the time change rate of the current iL, it fluctuates according to the time change rate of the current iL. However, since the inductance of the reactor L1 is small and the fundamental frequency of the current iL is as low as twice the fundamental frequency of the AC voltage Vin (for example, about 100 to 120 Hz), the voltage VL is schematically shown as zero in FIG. Has been done.

FIG. 4 is a diagram schematically showing an example of an AC voltage Vin, a current iL, and a voltage VL when the AC voltage Vin is distorted. In the example of FIG. 4, a substantially impulse-like voltage change occurs periodically (for example, half of the basic period of the AC voltage Vin) in the AC voltage Vin. In the example of FIG. 4, the period during which this voltage change occurs is shorter than, for example, a quarter period of the AC voltage Vin.

Due to the distortion of the AC voltage Vin, the current iL is also distorted. In the example of FIG. 4, a substantially impulse-like current change similar to the AC voltage Vin occurs periodically. More specifically, the current iL increases sharply in the impulse shape and decreases sharply as well. That is, the current iL increases and decreases at a time change rate higher than the maximum value of the time change rate in the sine wave during the period in which the impulse-like current change is recognized.

Further, the voltage VL is also distorted due to the distortion of the current iL. In the example of FIG. 4, since the time change rate of the current iL increases sharply in the strain, the voltage VL fluctuates greatly due to the distortion of the current iL. Specifically, the voltage VL takes a large positive value when the current iL sharply increases, and takes a small negative value when the current iL sharply decreases. That is, the larger the fluctuation (time change rate) of the current iL, the larger the absolute value | VL | of the voltage VL.

In the following, the waveform of the current iL when there is no distortion is referred to as an ideal component, and the distortion component generated in the current iL is also referred to as a distortion component.

By the way, in the core of the reactor L1, a larger eddy current is generated as the fluctuation of the current iL is larger. That is, the eddy current is generated by the ideal component of the current iL when the current iL does not have a distortion component, and further increases according to the distortion component when the current iL has a distortion component. This eddy current generates heat (Joule heat) due to the electrical resistance of the core. When the current iL is distorted, the eddy current increases due to this, and the calorific value of the reactor L1 increases. The temperature rise of the reactor L1 due to the distortion of the current iL is not preferable.

Therefore, the control unit 3 reduces the AC power output by the inverter 2 when the first condition that the absolute value | VL | of the voltage VL detected by the voltage detection unit 4 is larger than the voltage reference value Vref is satisfied. The power reduction control for generating the control signal S is executed so as to cause the control signal S to be generated.

FIG. 5 is a flowchart showing an example of the operation of the control unit 3. This series of processes is repeatedly executed.

First, in step ST1, the voltage detection unit 4 detects the voltage VL of the reactor L1 and outputs this to the motor control unit 31. Next, in step ST2, the motor control unit 31 determines whether or not the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref. This determination can be made, for example, using a comparator. When it is determined that the absolute value | VL | of the voltage VL is smaller than the voltage reference value Vref, the process ends.

When it is determined that the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref, the control unit 3 in step ST3 reduces the AC power output by the inverter 2 (hereinafter, also referred to as output AC power). Perform reduction control. As an example of specific power conversion control, for example, the motor control unit 31 performs droop control for reducing the rotation speed of the motor M1. The motor control unit 31 outputs the droop request signal N1 to the main control unit 30. When the main control unit 30 receives the drooping request signal N1, the main control unit 30 makes a correction for lowering the rotation speed command value ω *. For example, the main control unit 30 makes a correction to reduce the rotation speed command value ω * by a predetermined amount. The main control unit 30 outputs the corrected rotation speed command value ω * to the motor control unit 31.

The motor control unit 31 generates a control signal S based on the corrected rotation speed command value ω *, and outputs the control signal S to the inverter 2. The inverter 2 outputs an AC voltage based on the control signal S to the motor M1. As a result, the rotation speed ω of the motor M1 decreases. Therefore, the output AC power of the inverter 2 is reduced.

FIG. 6 is a diagram schematically showing an example of an AC voltage Vin, a current iL, and a voltage VL when power reduction control is performed. In the example of FIG. 6, the current iL and the voltage VL before the power reduction control is performed are shown by the alternate long and short dash lines. As shown in FIG. 6, the current iL is reduced by the power reduction control. The reason will be briefly explained below.

The output AC power of the inverter 2 is ideally equal to the input AC power input to the rectifier circuit 1. Further, when the AC power supply E1 connected to the rectifier circuit 1 is a commercial power supply, it can be regarded as a constant voltage source (the amplitude of the AC voltage Vin is substantially constant). Therefore, when the output AC power of the inverter 2 is reduced, the amplitude of the AC current input to the rectifier circuit 1 is reduced. Since the current iL flowing through the reactor L1 is ideally equal to the absolute value of the alternating current input to the rectifier circuit 1, the amplitude of the current iL is reduced as the amplitude of the alternating current is reduced. As the current iL is reduced, the peak value of the distortion component of the current iL is also reduced. Therefore, the fluctuation range of the voltage VL is also reduced. In the example of FIG. 6, the maximum value of the absolute value of the voltage VL is smaller than the voltage reference value Vref.

When the amplitude of the current iL of the reactor L1 and the peak value of the distortion component are reduced, the fluctuation (time change rate) of the current iL is reduced, so that the eddy current generated in the core of the reactor L1 is also reduced. Therefore, it is possible to suppress the temperature rise of the reactor L1 due to the eddy current.

As described above, according to the control unit 3, when the current iL is distorted and the absolute value | VL | of the voltage VL exceeds the reference value Vref, the output AC power of the inverter 2 is reduced to reduce the reactor L1. Current iL is reduced. As a result, the eddy current can be reduced, and the temperature rise of the reactor L1 can be suppressed.

Moreover, in the present embodiment, the distortion of the current iL is detected based on the voltage VL. According to this, it is easy to detect the distortion of the current iL. The details will be described below.

For example, in FIG. 4, the peak value A1 (= amplitude iLm of the current iL) when there is no distortion in the current iL and the peak value A2 due to the distortion take values close to each other. Further, when the magnitude of the distortion generated in the AC voltage Vin is small or the timing of occurrence is near the median value of the AC voltage Vin (here, 0: zero cross), the peak value A2 due to the distortion of the current iL becomes. It may be smaller than the peak value A1 of the ideal component. In this case, it is difficult to detect the distortion by comparing the current iL with the reference value.

On the other hand, the voltage VL takes a value according to the time change rate of the current iL. Normally, when the current iL is distorted, the maximum value of the time change rate of the distortion component tends to be higher than the maximum value of the time change rate of the ideal component. Therefore, the voltage VL changes remarkably due to the distortion component of the current iL. Therefore, it is easy to detect that the current iL is distorted by comparing the voltage VL with the reference value.

<3. Noise countermeasures>
In the above example, the power reduction control is executed when the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref. However, noise may occur in the voltage VL. It is not preferable that the power reduction control is executed due to such noise.

Therefore, the motor control unit 31 repeatedly determines whether or not the condition that the absolute value | VL | of the voltage VL of the reactor L1 is larger than the voltage reference value Vref is satisfied, and the number of times the condition is satisfied within a predetermined time is determined. The power reduction control may be executed when the number of times is greater than the predetermined number of times Nref.

FIG. 7 is a flowchart showing an example of the above operation of the control unit 3. This series of processes is repeatedly executed. In the following, the control when the power reduction control is not performed is also referred to as a normal control.

In step ST11, the motor control unit 31 acquires the timer value T. This timer value T is output by the timer circuit. This timer circuit is provided in, for example, the motor control unit 31.

Next, in step ST12, the motor control unit 31 determines whether or not the timer value T is larger than the Tref for a predetermined time. This predetermined time Tref is set to, for example, about several seconds (for example, 6 seconds). When it is determined that the timer value T is larger than the Tref for a predetermined time, the voltage detection unit 4 detects the voltage VL of the reactor L1 in step ST13.

Next, in step ST14, the motor control unit 31 determines whether or not the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref. When it is determined that the absolute value | VL | is smaller than the voltage reference value Vref, the motor control unit 31 executes step ST11 again. When it is determined that the absolute value | VL | is larger than the voltage reference value Vref, in step ST15, the motor control unit 31 increments the value N and executes step ST11 again. This value N indicates the number of times the condition that the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref is satisfied.

When it is determined in step ST12 that the timer value T is larger than the predetermined time Tref, the motor control unit 31 initializes the timer value T to zero in step ST16. Next, in step ST17, the motor control unit 31 determines whether or not the value N is larger than the predetermined number of times Nref. The value N at the time of execution of step ST17 indicates the number of times the above condition is satisfied in a predetermined time. The predetermined number of times Nref is set to, for example, several hundred times.

When it is determined that the value N is larger than the predetermined number of times Nref, the motor control unit 31 executes the power reduction control in step ST18. Next, in step ST19, the motor control unit 31 initializes the value N to zero and ends the process.

When it is determined in step ST17 that the value N is smaller than the predetermined number of times Nref, the motor control unit 31 executes normal control in step ST20. For example, if the power reduction control has been executed at the time of step ST17, the motor control unit 31 ends the power reduction control and executes the normal control. In this case, for example, the motor control unit 31 may output a normal request signal to the main control unit 30. The main control unit 30 that has received the normal request signal ends the above correction for the rotation speed command value ω *, and outputs the rotation speed command value ω * to the motor control unit 31 without making the correction. As a result, the rotation speed ω of the electric motor M1 is controlled based on the rotation speed command value ω * that has not been corrected.

If the normal control has been executed at the time of step ST17, the motor control unit 31 executes the normal control as it is.

As described above, even if the above conditions are satisfied, the power reduction control is not executed when the number of times of establishment in the predetermined time is less than the predetermined number of times, and the power reduction control is performed when the number of times of establishment is larger than the predetermined number of times. Will be executed. Therefore, even if the absolute value | Vref | of the voltage VL accidentally exceeds the voltage reference value Vref due to noise or the like, the power reduction control is not executed. Therefore, the power reduction control caused by noise can be suppressed or avoided.

Further, in the above example, the control unit 3 ends the power reduction control when the number of times the above conditions are satisfied in a predetermined time after the execution of the power reduction control is less than the predetermined number of times. That is, the power reduction control ends when the peak value of the absolute value | VL | of the voltage VL falls below the voltage reference value Vref and a predetermined time elapses from the start of the power reduction control. That is, even if the AC voltage Vin continues to be distorted, the power reduction control ends after a lapse of a predetermined time. Then, when the number of times the above conditions are satisfied exceeds the predetermined number of times in the predetermined time after the end of the power reduction control, the power reduction control is executed again. As a result, the temperature rise of the reactor L1 can be suppressed. That is, even if the AC voltage Vin is distorted, the temperature rise of the reactor L1 can be suppressed by intermittently performing the power reduction control.

According to this, the execution period of the power reduction control can be shortened as compared with the case where the power reduction control is terminated after waiting for the distortion of the AC voltage Vin to be eliminated, for example. That is, it is possible to suppress or avoid the power reduction control being executed for an unnecessarily long time. Therefore, the period during which the motor M1 can be rotated at a desired rotation speed can be lengthened.

The second embodiment.
When the peak value A1 (that is, the amplitude iLm) of the ideal component of the current iL is large, the eddy current generated by this ideal component is also large. When the peak value A2 of the strain component of the current iL is also large, the eddy current caused by the ideal component and the strain component is large, so it is desired to reduce the eddy current in order to suppress the temperature rise of the reactor L1. On the other hand, when the peak value A1 of the ideal component of the current iL is small, the eddy current generated by this ideal component is small. Therefore, when the peak value A1 is small, the eddy current is not so large even if the peak value A2 of the distortion component of the current iL is large. In this case, the calorific value of the reactor L1 is not so large, so there is little need to reduce the eddy current.

By the way, the current iL flowing through the reactor L1 ideally matches the absolute value of the input AC current Iin. Therefore, when the amplitude im of the input AC current Iin is small, the amplitude iLm of the current iL is also small.

Therefore, in the second embodiment, it is intended to determine the necessity of power reduction control in consideration of the amplitude im of the input AC current Iin.

The control device of the power conversion device according to the second embodiment detects the input alternating current Iin input to the rectifier circuit 1. Although a current detection unit that directly detects the input AC current Iin may be provided, the current detection unit 5 illustrated in FIG. 2 may be utilized. For example, the motor control unit 31 estimates the input AC current Iin using the AC currents iu, iv, and iwa detected by the current detection unit 5. Since such an estimation is known, detailed description thereof will be omitted. The alternating currents iu, iv, and iwa may be detected by the one-shunt method as described in the first embodiment.

The electric power control unit 31 satisfies both the first condition that the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref and the second condition that the amplitude im of the input AC current Iin is larger than the amplitude reference value. When doing so, the power reduction control is executed. As a result, the power reduction control can be executed when the calorific value of the reactor L1 is remarkably increased.

In other words, when at least one of the first condition and the second condition is not satisfied, the motor control unit 31 does not execute the power reduction control because the calorific value of the reactor L1 is not so high. According to this, it is possible to suppress or avoid the execution of unnecessary power reduction control. In other words, it is possible to suppress or avoid an extension of the period during which the output AC power of the inverter 2 is reduced. Therefore, the period during which the motor M1 can be rotated at a desired rotation speed can be extended.

FIG. 8 is a flowchart showing an example of the above operation of the control unit 3. This series of processes is repeatedly executed. Steps ST31 and ST32 are the same as steps ST1 and ST2, respectively. When it is determined in step ST32 that the absolute value | VL | of the voltage VL is larger than the voltage reference value Vref, in step ST33, the motor control unit 31 determines that the amplitude im of the input AC current Iin is from the amplitude reference value iref. Is also large or not. When it is determined that the amplitude im is larger than the amplitude reference value iref, the motor control unit 31 executes the power reduction control in step ST34.

When it is determined in step ST33 that the amplitude im of the input AC current Iin is smaller than the amplitude reference value iref, the motor control unit 31 ends the process without executing step ST34.

Modification example.
FIG. 9 is a diagram schematically showing an example of the configuration of the power conversion device 10A according to the modified example. The power converter 10A differs from the power converter 10 in that it further includes a power buffer circuit 7. The power buffer circuit 7 includes, for example, a booster circuit. For example, a booster circuit includes a booster reactor, a switch element, and a capacitor. The capacitor is connected between the DC lines LH and LL. The booster reactor and the switch element are connected in series with each other between the DC lines LH and LL, and when the switch element is turned on, energy is stored in the booster reactor. When the switch element is turned off, the energy stored in the step-up reactor is released to the capacitor and the capacitor is charged. As a result, the voltage of the capacitor can be boosted. Further, as is known, such a power buffer circuit 7 can also improve the power factor (input power factor) on the input side of the rectifier circuit 1.

The control unit 3 described above can also be applied to such a power conversion device 10A.

Within the scope of the present invention, the power conversion devices 10 and 10A and the control unit 3 can appropriately modify or omit the various embodiments described above as long as they do not conflict with each other.

1 Rectifier circuit 2 Inverter 3 Control unit 4 Voltage detection unit C1 Capacitor L1 Reactor LH, LL DC line P11, P12 Input end Pu, Pv, Pw Output end

Claims (3)

Multiple input terminals (P11, P12) connected to an AC power supply,
A pair of DC lines (LH, LL) and
With multiple output ends (Pu, Pv, Pw),
A rectifier circuit (1) connected between the plurality of input terminals and the pair of DC lines to perform AC / DC conversion, and a rectifier circuit (1).
A capacitor (C1) connected between the pair of DC lines and
A reactor (L1) provided on one (LH) of the pair of DC lines between the capacitor and the rectifier circuit, and
A device that controls a power conversion device including an inverter (2) that is connected between the pair of DC lines and the plurality of output terminals and performs DC / AC conversion, and detects the voltage (VL) of the reactor. Voltage detector (4) and
The AC power output by the inverter is reduced when the first condition that the absolute value of the voltage (VL) detected by the voltage detection unit is larger than the voltage reference value (Vref) is satisfied. It is equipped with a control unit (3) that executes power reduction control that generates a control signal to control the inverter .
The control unit (3)
It is repeatedly determined whether or not the first condition is satisfied, and
When the number of times (N) that the first condition is satisfied within the predetermined time is larger than the predetermined number of times (Nref), the power reduction control is executed.
After starting the execution of the power reduction control, the control unit (3) performs the power when the number of times (N) of the first condition being satisfied within the predetermined time is less than the predetermined number of times (Nref). Exit the reduction control, the controller of the power converter. Multiple input terminals (P11, P12) connected to an AC power supply,
A pair of DC lines (LH, LL) and
With multiple output ends (Pu, Pv, Pw),
A rectifier circuit (1) connected between the plurality of input terminals and the pair of DC lines to perform AC / DC conversion, and a rectifier circuit (1).
A capacitor (C1) connected between the pair of DC lines and
A reactor (L1) provided on one (LH) of the pair of DC lines between the capacitor and the rectifier circuit, and
With an inverter (2) that is connected between the pair of DC lines and the plurality of output ends and performs DC / AC conversion.
A device that controls a power conversion device equipped with
A voltage detector (4) that detects the voltage (VL) of the reactor, and
The AC power output by the inverter is reduced when the first condition that the absolute value of the voltage (VL) detected by the voltage detection unit is larger than the voltage reference value (Vref) is satisfied. With the control unit (3) that executes power reduction control that generates a control signal to control the inverter
With
The control unit (3)
Both the second condition that the amplitude (im) of the alternating current input to the rectifier circuit (1) via the plurality of input ends is larger than the amplitude reference value (iref) and the first condition are satisfied. when you performs the power reduction control, the control device of the power converter. The control device for the power conversion device according to claim 1 or 2,
With the power converter
A refrigeration system.

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