JP2022074951A - Electric power converting system and air conditioner - Google Patents

Abstract

To suppress current harmonic.SOLUTION: In an electric power conversion system 200, a first converter 11 converts three phases of a three-phase AC power source 100 into a direct current voltage, a second converter 21 converts one phase or two phases of the three-phase AC power source 100 into a second direct current voltage, an imbalance detection unit 34 determines whether or not imbalance occurs among currents of three phases which are input from the three-phase AC power source 100 to the first converter 11, and a control unit 36 controls the first converter 11 so as to solve the imbalance when the imbalance occurs among the currents of the three phases. The first direct current voltage is converted into first three-phase AC power by the first inverter 12 to be supplied to a motor M1, and the second direct current voltage is converted into second three-phase AC power by the second inverter 22 to be supplied to a motor M2.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to power converters and air conditioners.

An outdoor unit of an air conditioner having a compressor and a fan is referred to as a fan motor (hereinafter referred to as a "fan motor") in addition to a compressor motor (hereinafter sometimes referred to as a "compressor motor"). There is) is installed. Since the load of the fan motor is lighter than the load of the compressor motor, some air conditioners that use the three-phase AC power supply as the input power supply use the three-phase AC power supply as the input power supply to the drive circuit of the compressor motor. As the input power supply to the drive circuit of the fan motor, there is one that uses any one phase of the three-phase AC power supply.

Japanese Unexamined Patent Publication No. 2005-337563

However, if the fan motor is driven by one of the three-phase AC power supplies while the compressor motor is driven by the three-phase AC power supply, the load of the fan motor may fluctuate. The load may be out of balance. When the load is out of balance as seen from the three-phase power supply, the input current between the three phases varies and the current harmonics increase. Hereinafter, the variation in the input current between the three phases may be referred to as “unbalance”.

Therefore, this disclosure proposes a technique capable of suppressing current harmonics.

The power conversion device of the present disclosure includes a first converter, a second converter, a determination unit, and a control unit. The first converter converts the three phases of the three-phase AC power supply into the first DC voltage. The second converter converts one or two phases of the three-phase AC power supply into a second DC voltage. The determination unit determines whether or not an imbalance has occurred between the three-phase currents input from the three-phase AC power supply to the first converter. When the imbalance is occurring, the control unit controls the first converter to eliminate the imbalance.

According to the disclosed technique, current harmonics can be suppressed.

FIG. 1 is a diagram showing a configuration example of a power conversion device and an outdoor unit according to an embodiment of the present disclosure. FIG. 2 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 3 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 4 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 5 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 6 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 7 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 8 is a diagram for explaining an operation example of the power conversion device according to the embodiment of the present disclosure. FIG. 9 is a flowchart showing an example of a processing procedure in the power conversion device according to the embodiment of the present disclosure.

Hereinafter, examples of the present disclosure will be described with reference to the drawings. In the following examples, the same configurations are designated by the same reference numerals.

[Example]
<Structure of power converter>
FIG. 1 is a diagram showing a configuration example of a power conversion device and an outdoor unit according to an embodiment of the present disclosure. For example, the power conversion device 200 shown in FIG. 1 is mounted on an outdoor unit 300 having a plurality of motors M1 and M2, and can be used for an air conditioner having an outdoor unit 300 and an indoor unit.

In FIG. 1, the outdoor unit 300 includes a power conversion device 200, a first inverter 12, a second inverter 22, a motor M1, and a motor M2. The power conversion device 200 is connected to the three-phase AC power supply 100, the first inverter 12, and the second inverter 22. The three-phase AC power supply 100 is used as an input power source for the power conversion device 200. The first inverter 12 is connected to the motor M1, and the second inverter 22 is connected to the motor M2. In terms of the magnitude of the load, the motor M2 is smaller than the motor M1. An example of the motor M2 is a fan motor, an example of the motor M1 is a compressor motor, and the outdoor unit 300 is composed of the fan motor and the compressor motor.

The power converter 200 includes a first converter 11 and a second converter 21. The R-phase, S-phase, and T-phase of the three-phase AC power supply 100 are connected to the input of the first converter 11, while the R-phase of the three-phase AC power supply 100 is connected to the input of the second converter 21. , One or two of the S phase and the T phase are connected. In FIG. 1, when the second converter 21 is driven by a single-phase power supply, the S-phase one-phase and the neutral point N of the three-phase AC power supply 100 are used as input power supplies to the second converter 21. An example is a case where two phases of R phase and T phase are used as an input power supply to the second converter 21 when the two converter 21 is driven by a two-phase power supply. However, one phase of R phase or T phase may be used as the single phase power supply of the second converter 21, and two phases of R phase and S phase or S may be used as the two phase power supply of the second converter 21. Two phases, a phase and a T phase, may be used.

Further, the power conversion device 200 includes a zero cross detection unit 31, an input voltage detection unit 32, an input current detection unit 33, an imbalance determination unit 34, a DC voltage detection unit 35, a control unit 36, and a storage unit 37. And have. The zero-cross detection unit 31, the input voltage detection unit 32, the input current detection unit 33, the unbalance determination unit 34, the DC voltage detection unit 35, and the control unit 36 are realized by hardware, for example, an MCU (Micro Control Unit). The storage unit 37 is realized as hardware, for example, by a memory.

The first converter 11 converts the three phases of the R phase, S phase, and T phase of the three-phase AC power supply 100 into the DC voltage DC1 and converts the DC voltage DC1 into the first inverter 12 under the switching control from the control unit 36. Supply to. Here, the operation of the first converter 11 to convert the three phases of the R phase, S phase, and T phase of the three-phase AC power supply 100 into the DC voltage DC 1, includes, for example, rectification, power factor improvement, and boosting.

The first inverter 12 converts the DC voltage DC1 supplied from the first converter 11 into U-phase, V-phase, and W-phase three-phase AC power under switching control from the control unit 36, and converts the DC voltage DC1 into three-phase AC power. Power is supplied to the motor M1.

When the second converter 21 is driven by a single-phase power supply, one phase of the S phase is converted into a DC voltage DC2, and the DC voltage DC2 is supplied to the second inverter 22. Further, when the second converter 21 is driven by a two-phase power supply, the two phases of S phase and T phase are converted into a DC voltage DC2, and the DC voltage DC2 is supplied to the second inverter 22. The second converter 21 may convert one phase of the R phase or the T phase into a DC voltage DC2 when driven by a single-phase power supply. Further, the second converter 21 may convert two phases of R phase and S phase or two phases of R phase and T phase into a DC voltage DC2 when driven by a two-phase power supply. That is, the second converter 21 converts one or two of the R phase, S phase, and T phase of the three-phase AC power supply 100 into a DC voltage.

The second inverter 22 converts the DC voltage DC2 supplied from the second converter 21 into U-phase, V-phase, and W-phase three-phase AC power under switching control from the control unit 36, and converts the DC voltage DC2 into three-phase AC power. Power is supplied to the motor M2.

As an example of the first converter 11, a bridge rectifier circuit having a boosting function for improving the power factor in a circuit of each phase configured by using a reactor, a switching element, and a diode can be mentioned. Examples of switching elements include IGBTs (Insulated Gate Bipolar Transistors), FETs (Field Effect Transistors), and the like. Further, as an example of the second converter 21, a bridge rectifier circuit composed of a diode can be mentioned.

The zero-cross detection unit 31 refers to an R-phase current waveform (hereinafter, may be referred to as “R-phase waveform”) and an S-phase current waveform (hereinafter, “S-phase”) with respect to the three-phase AC power supply 100, which is an input power source. The zero cross point in the current waveform of each phase of the waveform of the T-phase current (sometimes referred to as the "T-phase waveform" below) is detected, and the detection result is determined by the imbalance determination unit. Output to 34 and the control unit 36. Hereinafter, the R-phase current, the S-phase current, and the T-phase current may be collectively referred to as an “input current”, and the R-phase waveform, the S-phase waveform, and the T-phase waveform may be collectively referred to as an “input current waveform”.

The input voltage detection unit 32 detects the R-phase voltage value, the S-phase voltage value, and the T-phase voltage value as the input voltage value of the first converter 11, and outputs the detection result to the control unit 36. Hereinafter, the R-phase voltage value, the S-phase voltage value, and the T-phase voltage value may be collectively referred to as “input voltage value”.

The input current detection unit 33 detects the R-phase current value, the S-phase current value, and the T-phase current value as the input current values of the first converter 11, and outputs the detection results to the imbalance determination unit 34 and the control unit 36. .. Hereinafter, the R-phase current value, the S-phase current value, and the T-phase current value may be collectively referred to as “input current value”.

The DC voltage detection unit 35 detects the value of the DC voltage DC1 output from the first converter 11 and outputs the detected DC voltage value to the control unit 36.

The unbalance determination unit 34 determines whether or not the input current between the three phases is unbalanced based on the zero cross point in the input current waveform and the input current value, that is, the R phase waveform, the S phase waveform, and the T phase. It is determined whether or not the waveform is in an unbalanced state, and the determination result (hereinafter, may be referred to as “unbalanced determination result”) is output to the control unit 36.

The control unit 36 performs switching control for the first converter 11 based on the zero cross point of the input current waveform, the input voltage value, the input current value, the DC voltage value, and the imbalance determination result. For example, the control unit 36 performs switching control at the timing when the zero cross point arrives (hereinafter, may be referred to as “zero cross timing”) or at the timing after a predetermined time has elapsed from the zero cross timing.

<Operation of power converter>
2 to 8 are diagrams provided for explaining an operation example of the power conversion device according to the embodiment of the present disclosure.

In FIG. 2, the R-phase waveform, the S-phase waveform, and the T-phase waveform are in a well-balanced state among the three phases of the R-phase, the S-phase, and the T-phase (hereinafter, may be referred to as a “three-phase balanced state”). An example of the case where is shown in. That is, in the three-phase balanced state, between the current value of the peak point PS of the S-phase waveform IS, the current value of the peak point PT of the T-phase waveform IT, and the current value of the peak point PR of the R-phase waveform IR. All of the absolute values of the mutual differences are below the predetermined threshold Y. Further, in the three-phase balanced state, the elapsed time tS from the zero crossing point ZS of the S phase waveform IS to the peak point PS, the elapsed time tT from the zero crossing point ZT of the T phase waveform IT to the peak point PT, and the R phase waveform IR. The elapsed time tR from the zero cross point ZR to the peak point PR is the same as each other.

Hereinafter, operation examples 1 to 3 when the second converter 21 is driven by a single-phase power supply and operation examples 4 to 6 when the second converter 21 is driven by a two-phase power supply will be described separately. Further, FIGS. 3 and 6 show an operation example when the absolute value of the difference between the current values at the peak points (hereinafter, may be referred to as “peak difference value”) becomes the threshold value Y or more in the three-phase input current waveform. 1 and 4 are shown. Further, in FIGS. The operation examples 2 and 5 of the above are shown. Further, FIGS. 5 and 8 show operation examples 3 and 6 when the peak difference value is equal to or higher than the threshold value Y and there is a phase whose peak point arrival time is different from that of other phases in the three-phase input current waveform. ..

In the following, the peak point of the R-phase waveform will be referred to as the "R-phase peak point", the peak point of the S-phase waveform will be referred to as the "S-phase peak point", and the peak point of the T-phase waveform will be referred to as the "T-phase peak point". I may call it. In the following, the current value at the R-phase peak point is referred to as "R-phase peak value", the current value at the S-phase peak point is referred to as "S-phase peak value", and the current value at the T-phase peak point is referred to as "T-phase peak". Sometimes called "value".

Further, as shown in FIG. 1, operation examples 1 to 3 in the case where one phase of the S phase is used as an input power supply to the second converter 21 when the second converter 21 is driven by a single-phase power supply will be described below. do. Further, in the following, as shown in FIG. 1, when the second converter 21 is driven by the two-phase power supply, the two phases of the R phase and the T phase are used as the input power supply to the second converter 21. 6 will be described.

<Operation example 1 (Fig. 3)>
When the S-phase waveform IS11A, the T-phase waveform IT11A, and the R-phase waveform IR11A are in the state shown in FIG. The peak value PT11A and the R phase peak value PR11A in the R phase waveform IR11A are detected. Further, the imbalance determination unit 34 detects the peak point arrival time tS in the S-phase waveform IS11A, the peak point arrival time tT in the T-phase waveform IT11A, and the peak point arrival time tR in the R-phase waveform IR11A.

In FIG. 3, the T-phase peak value PT11A and the R-phase peak value PR11A are smaller than the S-phase peak value PS11A. On the other hand, in FIG. 3, the peak point arrival time tS, the peak point arrival time tT, and the peak point arrival time tR are the same as each other.

Therefore, the imbalance determination unit 34 calculates the peak difference value ΔPST1 between the S-phase peak value PS11A and the T-phase peak value PT11A, and the peak difference value ΔPSR1 between the S-phase peak value PS11A and the R-phase peak value PR11A. Further, the imbalance determination unit 34 determines whether or not the absolute value of the peak difference value ΔPST1 and the absolute value of the peak difference value ΔPSR1 are equal to or greater than the threshold value Y.

Then, in the unbalance determination unit 34, when the condition C1 that both the absolute value of the peak difference value ΔPST1 and the absolute value of the peak difference value ΔPSR1 are equal to or higher than the threshold value Y is satisfied, the input currents of the three phases are in an unbalanced state. Judged to be in. Here, since one phase of the S phase is used as an input power source to the second converter 21, the imbalance determination unit 34 determines that an imbalance between the T phase and the R phase has occurred in the S phase. do.

On the other hand, when the condition C1 is not satisfied, the unbalance determination unit 34 determines that the three-phase input current is in the three-phase balanced state. Here, it is assumed that the condition C1 is satisfied. Therefore, the unbalance determination unit 34 outputs a signal indicating that the condition C1 is satisfied to the control unit 36 as an unbalance determination result, and also outputs the S phase peak value PS11A, the T phase peak value PT11A, and the R phase peak value PR11A. , The peak difference value ΔPST1 and the peak difference value ΔPSR1 are output to the control unit 36.

When the signal indicating that the condition C1 is not satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 is in a three-phase balanced state because the three-phase input current is in a three-phase balanced state. Switching control (hereinafter, may be referred to as "normal switching control") for improving the power factor and controlling the output voltage is performed on the first converter 11.

On the other hand, when the signal indicating that the condition C1 is satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 has, as shown in FIG. 3, in addition to the normal switching control. T so that the T-phase peak value PT11A and the R-phase peak value PR11A are the same as the S-phase peak value PS11A, and the T-phase waveform IT11A and the R-phase waveform IR11A follow the S-phase waveform IS11A as the reference current waveform. Additional switching control in the phase and R phase is performed on the first converter 11. In the additional switching control in the T phase (T phase control shown in FIG. 3), the control unit 36 sets the peak difference value ΔPST1 to 0 (in the T phase) by increasing the T phase peak value PT11A to the T phase peak value PT11B. Switching control to make it zero) is performed to change the T-phase waveform IT11A into the T-phase waveform IT11B. Further, in the additional switching control in the R phase (R phase control shown in FIG. 3), the control unit 36 increases the peak difference value ΔPSR1 in the R phase by increasing the R phase peak value PR11A to the R phase peak value PR11B. Switching control to make it 0 (zero) is performed to change the R-phase waveform IR11A into the R-phase waveform IR11B. Therefore, by such additional switching control, the imbalance between the three phases of R phase, S phase and T phase is eliminated, and the input currents of the three phases of R phase, S phase and T phase are in the three phase balanced state. ..

The T-phase control and the R-phase control shown in FIG. 3 are switching controls in half a cycle of positive values of the T-phase waveform IT11A and the R-phase waveform IR11A. However, although not shown in the figure, switching control is performed even in a half cycle of a negative value. Similarly, in FIGS. 4 to 8 below, switching control is performed even in a half cycle of a negative value.

<Operation example 2 (Fig. 4)>
When the S-phase waveform IS12A, the T-phase waveform IT12A and the R-phase waveform IR12A are in the state shown in FIG. 4, the imbalance determination unit 34 determines the S-phase peak value in the S-phase waveform IS12A and the T-phase peak in the T-phase waveform IT12A. The value and the R phase peak value in the R phase waveform IR12A are detected. Further, the imbalance determination unit 34 detects the peak point arrival time tSA1 in the S-phase waveform IS12A, the peak point arrival time tTA1 in the T-phase waveform IT12A, and the peak point arrival time tRA1 in the R-phase waveform IR12A.

In FIG. 4, the peak point arrival time tTA1 and the peak point arrival time tRA1 are the same as each other and shorter than the peak point arrival time tSA1. On the other hand, in FIG. 4, the T-phase peak value, the R-phase peak value, and the S-phase peak value are the same as each other.

Therefore, the unbalance determination unit 34 compares the peak point arrival time tSA1 of the S phase, which is the single-phase power supply of the second converter 21, with the peak point arrival times tTA1 and tRA1 of the two phases other than the S phase. , It is determined whether or not the difference in arrival time is within the range of the allowable value Z. Then, in the imbalance determination unit 34, both the difference between the peak point arrival time tSA1 and the peak point arrival time tTA1 and the difference between the peak point arrival time tSA1 and the peak point arrival time tRA1 are within the allowable value Z. When it is, it is determined that the peak point arrival time tSA1, the peak point arrival time tTA1, and the peak point arrival time tRA1 are the same as each other. On the other hand, in the imbalance determination unit 34, at least one of the difference between the peak point arrival time tSA1 and the peak point arrival time tTA1 and the difference between the peak point arrival time tSA1 and the peak point arrival time tRA1 is within the allowable value Z range. If it is not within the range, it is determined that the peak point arrival time tSA1, the peak point arrival time tTA1, and the peak point arrival time tRA1 are not the same as each other.

Then, the imbalance determination unit 34 determines the three phases when the condition C2 that the peak point arrival time is different from the other two phases exists among the three phases of the R phase, the S phase, and the T phase. It is determined that the input current of is in an unbalanced state. Further, the imbalance determination unit 34 determines that an imbalance with the other two phases has occurred in one phase in which the peak point arrival time is different from the other two phases. Here, since one phase of the S phase is used as an input power source to the second converter 21, the imbalance determination unit 34 considers that an imbalance between the T phase and the R phase has occurred in the S phase. ..

On the other hand, when the condition C2 is not satisfied, that is, when the peak point arrival times are the same among the three phases of the R phase, the S phase, and the T phase, the imbalance determination unit 34 has three input currents of the three phases. It is determined that the phase is in a balanced state. Here, it is assumed that the condition C2 is satisfied. Therefore, the unbalance determination unit 34 outputs a signal indicating that the condition C2 is satisfied to the control unit 36 as an unbalance determination result, and also has a peak point arrival time tSA1, a peak point arrival time tTA1, and a peak point arrival time tRA1. Is output to the control unit 36.

When the signal indicating that the condition C2 is not satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 normally performs switching control to the first converter 11.

On the other hand, when the signal indicating that the condition C2 is satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 has, as shown in FIG. 4, in addition to the normal switching control. The peak point arrival time tTA1 and tRA1 are the same as the peak point arrival time tSA1, and the T-phase waveform IT12A and the R-phase waveform IR12A follow the S-phase waveform IS12A as the reference current waveform. The additional switching control in is performed on the first converter 11. In the additional switching control in the T phase (T phase control shown in FIG. 4), the control unit 36 reaches the peak point in the T phase by increasing the peak point arrival time tTA1 to the peak point arrival time tTB1 in the T phase. Switching control is performed to match the length of time with the length of the peak point arrival time tSA1, and the peak point PT of the T-phase waveform is moved backward on the time axis as shown in FIG. As the peak point PT of the T-phase waveform moves backward on the time axis, the T-phase waveform IT12A changes to the T-phase waveform IT12B. Further, in the additional switching control in the R phase (R phase control shown in FIG. 4), the control unit 36 increases the peak point arrival time tRA1 to the peak point arrival time tRB1 in the R phase, so that the peak in the R phase is reached. Switching control is performed to match the length of the point arrival time with the length of the peak point arrival time tSA1, and the peak point PR of the R phase waveform is moved backward on the time axis as shown in FIG. As the peak point PR of the R-phase waveform moves backward on the time axis, the R-phase waveform IR12A changes to the R-phase waveform IR12B. Therefore, by such additional switching control, the imbalance between the three phases of R phase, S phase and T phase is eliminated, and the input currents of the three phases of R phase, S phase and T phase are in the three phase balanced state. ..

<Operation example 3 (Fig. 5)>
The operation example 3 is an operation example in which the operation example 1 and the operation example 2 are combined.

That is, when the T-phase waveform IT13A, the S-phase waveform IS13A and the R-phase waveform IR13A are in the state shown in FIG. 5, the T-phase peak value in the T-phase waveform IT13A and the R-phase peak value in the R-phase waveform IR13A are S. It is smaller than the S phase peak value in the phase waveform IS13A. Further, both the absolute value of the peak difference value between the S-phase peak value and the T-phase peak value and the absolute value of the peak difference value between the S-phase peak value and the R-phase peak value are equal to or higher than the threshold value Y.

Further, when the T-phase waveform IT13A, the S-phase waveform IS13A, and the R-phase waveform IR13A are in the state shown in FIG. 5, the peak point arrival time in the T-phase waveform IT13A and the peak point arrival time in the R-phase waveform IR13A are the same. Moreover, it is shorter than the peak point arrival time in the S-phase waveform IS13A. To determine whether or not the peak point arrival times of each phase are the same, it is determined whether or not the peak point arrival time difference between the phases is within the allowable value Z, as described above. If the peak point arrival time difference between each phase is within the allowable value Z, it is considered that the peak point arrival time of each phase is the same as each other.

Therefore, the unbalance determination unit 34 determines that the three-phase input current is in the unbalanced state, and outputs the determination result to the control unit 36.

Therefore, in addition to the normal switching control, the control unit 36 has T-phase and R so that the T-phase waveform IT13A and the R-phase waveform IR13A follow the S-phase waveform IS13A as the reference current waveform, as shown in FIG. Additional switching control in the phase is performed on the first converter 11.

In the additional switching control in the T phase (T phase control shown in FIG. 5), the control unit 36 increases the T phase peak value in the T phase to obtain the peak difference between the S phase peak value and the T phase peak value. Switching control is performed to set the value to 0 (zero). Further, in the additional switching control in the T phase, the control unit 36 increases the peak point arrival time in the T phase waveform IT13A in the T phase, thereby increasing the length of the peak point arrival time in the T phase to the peak in the S phase. Switching control is performed to match the length of the point arrival time. As a result, the T-phase waveform IT13A changes to the T-phase waveform IT13B.

Further, in the additional switching control in the R phase (R phase control shown in FIG. 5), the control unit 36 sets the S phase peak value and the R phase peak value by increasing the R phase peak value in the R phase. Switching control is performed to set the peak difference value to 0 (zero). Further, in the additional switching control in the R phase, the control unit 36 increases the peak point arrival time in the R phase waveform IR13A in the R phase, thereby increasing the length of the peak point arrival time in the R phase to the peak in the S phase. Switching control is performed to match the length of the point arrival time. As a result, the R-phase waveform IR13A changes to the R-phase waveform IR13B.

By such additional switching control, the T-phase waveform IT13A is changed to the T-phase waveform IT13B, and the R-phase waveform IR13A is changed to the R-phase waveform IR13B, so that the three phases of the R-phase, the S-phase, and the T-phase are changed. The imbalance is eliminated, and the input currents of the three phases of R phase, S phase and T phase are in the three phase balanced state.

<Operation example 4 (Fig. 6)>
When the S-phase waveform IS21A, the T-phase waveform IT21A, and the R-phase waveform IR21A are in the state shown in FIG. The peak value PT21A and the R phase peak value PR21A in the R phase waveform IR21A are detected. Further, the imbalance determination unit 34 detects the peak point arrival time tS in the S-phase waveform IS21A, the peak point arrival time tT in the T-phase waveform IT21A, and the peak point arrival time tR in the R-phase waveform IR21A.

In FIG. 6, the S-phase peak value PS21A is smaller than the T-phase peak value PT21A and the R-phase peak value PR21A. On the other hand, in FIG. 6, the peak point arrival time tS, the peak point arrival time tT, and the peak point arrival time tR are the same as each other.

Therefore, the imbalance determination unit 34 calculates the peak difference value ΔPST2 between the S-phase peak value PS21A and the T-phase peak value PT21A, and the peak difference value ΔPSR2 between the S-phase peak value PS21A and the R-phase peak value PR21A. Further, the imbalance determination unit 34 determines whether or not the absolute value of the peak difference value ΔPST2 and the absolute value of the peak difference value ΔPSR2 are equal to or greater than the threshold value Y.

Then, in the unbalance determination unit 34, when the condition C3 that both the absolute value of the peak difference value ΔPST2 and the absolute value of the peak difference value ΔPSR2 are equal to or higher than the threshold value Y is satisfied, the input currents of the three phases are in an unbalanced state. Judged to be in. Here, since the two phases of the R phase and the T phase are used as the input power source to the second converter 21, the imbalance determination unit 34 causes an imbalance with the S phase in the R phase and the T phase. It is determined that there is.

On the other hand, when the condition C3 is not satisfied, the unbalance determination unit 34 determines that the three-phase input current is in the three-phase balanced state. Here, it is assumed that the condition C3 is satisfied. Therefore, the unbalance determination unit 34 outputs a signal indicating that the condition C3 is satisfied to the control unit 36 as an unbalance determination result, and also outputs the S phase peak value PS21A, the T phase peak value PT21A, and the R phase peak value PR21A. , The peak difference value ΔPST2 and the peak difference value ΔPSR2 are output to the control unit 36.

When the signal indicating that the condition C3 is not satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 normally performs switching control to the first converter 11.

On the other hand, when the signal indicating that the condition C3 is satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 has, as shown in FIG. 6, in addition to the normal switching control. S so that the S-phase peak value PS21A becomes the same as the T-phase peak value PT21A or the R-phase peak value PR21A, and the S-phase waveform IS21A follows the T-phase waveform IT21A or the R-phase waveform IR21A as the reference waveform. Additional switching control in the phase is performed on the first converter 11. In the additional switching control in the S phase (S phase control shown in FIG. 6), the control unit 36 increases the peak difference value ΔPST2 or the peak in the S phase by increasing the S phase peak value PS21A to the S phase peak value PS21B. Switching control is performed to set the difference value ΔPSR2 to 0 (zero), and the S-phase waveform IS21A is changed to the S-phase waveform IS21B. Therefore, by such additional switching control, the imbalance between the three phases of R phase, S phase and T phase is eliminated, and the input currents of the three phases of R phase, S phase and T phase are in the three phase balanced state. ..

<Operation example 5 (Fig. 7)>
When the S-phase waveform IS22A, the T-phase waveform IT22A and the R-phase waveform IR22A are in the state shown in FIG. 7, the imbalance determination unit 34 determines the S-phase peak value in the S-phase waveform IS22A and the T-phase peak in the T-phase waveform IT22A. The value and the R phase peak value in the R phase waveform IR22A are detected. Further, the imbalance determination unit 34 detects the peak point arrival time tSA2 in the S-phase waveform IS22A, the peak point arrival time tTA2 in the T-phase waveform IT22A, and the peak point arrival time tRA2 in the R-phase waveform IR22A.

In FIG. 7, the peak point arrival time tTA2 and the peak point arrival time tRA2 are the same as each other and are longer than the peak point arrival time tSA2. On the other hand, in FIG. 7, the T-phase peak value, the R-phase peak value, and the S-phase peak value are the same as each other. To determine whether or not the peak point arrival times of each phase are the same, it is determined whether or not the peak point arrival time difference between the phases is within the allowable value Z, as described above. If the peak point arrival time difference between each phase is within the allowable value Z, it is considered that the peak point arrival time of each phase is the same as each other.

Therefore, the imbalance determination unit 34 determines whether or not the peak point arrival time tSA2, the peak point arrival time tTA2, and the peak point arrival time tRA2 are the same as each other.

Then, the imbalance determination unit 34 determines the three phases when the condition C2 that the peak point arrival time is different from the other two phases exists among the three phases of the R phase, the S phase, and the T phase. It is determined that the input current of is in an unbalanced state. Further, the imbalance determination unit 34 determines that an imbalance with the other one phase has occurred in the two phases whose peak point arrival time is different from that of the other one phase. Here, since the two phases of the R phase and the T phase are used as the input power source to the second converter 21, the imbalance determination unit 34 causes an imbalance with the S phase in the R phase and the T phase. It is determined that there is.

On the other hand, when the condition C2 is not satisfied, that is, when the peak point arrival times are the same among the three phases of the R phase, the S phase, and the T phase, the imbalance determination unit 34 has three input currents of the three phases. It is determined that the phase is in a balanced state. Here, it is assumed that the condition C2 is satisfied. Therefore, the unbalance determination unit 34 outputs a signal indicating that the condition C2 is satisfied to the control unit 36 as an unbalance determination result, and also has a peak point arrival time tSA2, a peak point arrival time tTA2, and a peak point arrival time tRA2. Is output to the control unit 36.

When the signal indicating that the condition C2 is not satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 normally performs switching control to the first converter 11.

On the other hand, when the signal indicating that the condition C2 is satisfied is input from the unbalance determination unit 34 as the unbalance determination result, the control unit 36 has, as shown in FIG. 7, in addition to the normal switching control. The peak point arrival time tSA2 becomes the same as the peak point arrival time tTA2 or the peak point arrival time tRA2, and the S-phase waveform IS22A follows the T-phase waveform IT22A or the R-phase waveform IR22A as the reference waveform. Additional switching control in the phase is performed on the first converter 11. In the additional switching control in the S phase (S phase control shown in FIG. 7), the control unit 36 reaches the peak point in the S phase by increasing the peak point arrival time tTA2 to the peak point arrival time tTB2 in the S phase. Switching control is performed to match the length of time with the length of the peak point arrival time tTA2 or the peak point arrival time tRA2, and the peak point PS of the S-phase waveform is moved backward on the time axis as shown in FIG. .. As the peak point PS of the S-phase waveform moves backward on the time axis, the S-phase waveform IS22A changes to the S-phase waveform IS22B. Therefore, by such additional switching control, the imbalance between the three phases of R phase, S phase and T phase is eliminated, and the input currents of the three phases of R phase, S phase and T phase are in the three phase balanced state. ..

<Operation example 6 (Fig. 8)>
The operation example 6 is an operation example in which the operation example 4 and the operation example 5 are combined.

That is, when the T-phase waveform IT23A, the S-phase waveform IS23A and the R-phase waveform IR23A are in the state shown in FIG. 8, the T-phase peak value in the T-phase waveform IT23A and the R-phase peak value in the R-phase waveform IR23A are S. It is larger than the S phase peak value in the phase waveform IS23A. Further, both the absolute value of the peak difference value between the S-phase peak value and the T-phase peak value and the absolute value of the peak difference value between the S-phase peak value and the R-phase peak value are both equal to or higher than the threshold value Y, and The absolute value of the peak difference value between the T-phase peak value and the R-phase peak value is less than the threshold value Y.

Further, when the T-phase waveform IT23A, the S-phase waveform IS23A, and the R-phase waveform IR23A are in the state shown in FIG. 8, the peak point arrival time in the T-phase waveform IT23A and the peak point arrival time in the R-phase waveform IR23A are the same. Moreover, it is longer than the peak point arrival time in the S-phase waveform IS23A. To determine whether or not the peak point arrival times of each phase are the same, it is determined whether or not the peak point arrival time difference between the phases is within the allowable value Z, as described above. If the peak point arrival time difference between each phase is within the allowable value Z, it is considered that the peak point arrival time of each phase is the same as each other.

Therefore, the unbalance determination unit 34 determines that the three-phase input current is in the unbalanced state, and outputs the determination result to the control unit 36.

Therefore, in addition to the normal switching control, the control unit 36 adds the S-phase waveform IS23A in the S-phase so as to follow the T-phase waveform IT23A or the R-phase waveform IR23A as the reference current waveform, as shown in FIG. Switching control is performed on the first converter 11.

In the additional switching control in the S phase (S phase control shown in FIG. 8), the control unit 36 increases the S phase peak value in the S phase to obtain the peak difference between the S phase peak value and the T phase peak value. Switching control is performed so that the value or the peak difference value between the S-phase peak value and the R-phase peak value is set to 0 (zero). Further, in the additional switching control in the S phase, the control unit 36 increases the peak point arrival time in the S phase waveform IS23A in the S phase, thereby setting the length of the peak point arrival time in the S phase to the T phase and R. Switching control is performed to match the length of the peak point arrival time in the phase. As a result, the S-phase waveform IS23A changes to the S-phase waveform IS23B.

By changing the S-phase waveform IS23A to the S-phase waveform IS23B by such additional switching control, the imbalance among the three phases of R-phase, S-phase and T-phase is eliminated, and the R-phase, S-phase and T-phase are eliminated. The three-phase input current is in a three-phase balanced state.

<Processing procedure in the power converter>
FIG. 9 is a flowchart showing an example of a processing procedure in the power conversion device according to the embodiment of the present disclosure.

In FIG. 9, in step S300, the control unit 36 determines whether the second converter 21 is driven by a single-phase power supply or a two-phase power supply. For example, information on whether the second converter 21 is driven by a single-phase power supply or a two-phase power supply (hereinafter, may be referred to as “power supply information”) is stored in advance in the storage unit 37, and is stored in the control unit 36. Determines whether the second converter 21 is driven by a single-phase power supply or a two-phase power supply by referring to the power supply information stored in the storage unit 37. When the second converter 21 is driven by the single-phase power supply (step S300: Yes), the process proceeds to step S305, and when the second converter 21 is driven by the two-phase power supply (step S300: No). , The process proceeds to step S320.

In step S305, the unbalance determination unit 34 determines whether or not one of the three phases of the R phase, the S phase, and the T phase, which is used as the single-phase power supply, is unbalanced with the other two phases. That is, it is determined whether or not a single-phase imbalance has occurred. When single-phase imbalance has occurred (step S305: Yes), the process proceeds to step S310, and when single-phase imbalance has not occurred, that is, the three phases of R phase, S phase, and T phase have occurred. When it is in the three-phase balanced state (step S305: No), the process proceeds to step S315.

In step S310, in addition to the normal switching control, the control unit 36 additionally switches in two phases other than the one phase used as the single-phase power supply among the three phases of R phase, S phase and T phase. Control is performed on the first converter 11.

Further, in step S320, the imbalance determination unit 34 causes an imbalance with the other one phase in the two phases used as the two-phase power supply among the three phases of the R phase, the S phase and the T phase. Whether or not, that is, whether or not a two-phase imbalance has occurred is determined. When the two-phase imbalance has occurred (step S320: Yes), the process proceeds to step S325, and when the two-phase imbalance has not occurred, that is, the three phases of R phase, S phase and T phase have occurred. When it is in the three-phase balanced state (step S320: No), the process proceeds to step S315.

In step S325, in addition to the normal switching control, the control unit 36 performs additional switching in one of the three phases of the R phase, the S phase, and the T phase other than the two phases used as the two-phase power supply. Control is performed on the first converter 11.

On the other hand, in step S315, the control unit 36 does not perform additional switching control on the first converter 11, but only performs normal switching control.

Note that FIG. 9 shows a flowchart in which the power supply supplied to the second converter 21 is switched between the single-phase power supply and the two-phase power supply. However, the power supply supplied to the second converter 21 may be fixed to either a single-phase power supply or a two-phase power supply. When the power supplied to the second converter 21 is fixed to either a single-phase power supply or a two-phase power supply, step S300 is deleted from the flowchart of FIG. 9, and the flowchart of FIG. 9 shows the case of a single-phase power supply. It is divided into two separate flowcharts (steps S305, S310, S315) and a flowchart (steps S320, S325, S315) in the case of a two-phase power supply.

The examples have been described above.

As described above, the power conversion device (power conversion device 200 of the embodiment) of the present disclosure includes a first converter (first converter 11 of the embodiment), a second converter (second converter 21 of the embodiment), and the like. It has a determination unit (unbalance determination unit 34 of the embodiment) and a control unit (control unit 36 of the embodiment). The first converter converts the three phases of the three-phase AC power supply (three-phase AC power supply 100 of the embodiment) into the first DC voltage. The second converter converts one or two phases of a three-phase AC power supply into a second DC voltage. The determination unit determines whether or not an imbalance has occurred between the three-phase currents input from the three-phase AC power supply to the first converter. The control unit controls the first converter to eliminate the imbalance when an imbalance occurs between the three-phase currents.

For example, the determination unit determines whether or not an imbalance has occurred based on the peak value of the three-phase current input from the three-phase AC power supply to the first converter.

Further, for example, the determination unit determines whether or not an imbalance has occurred based on the elapsed time from the zero cross point to the peak point in the current waveform of the three-phase current input from the three-phase AC power supply to the first converter. judge.

By doing so, the three-phase current input from the three-phase AC power supply to the first converter can be maintained in a three-phase balanced state, so that current harmonics can be suppressed. In particular, current harmonics can be suppressed in a power conversion device for driving a plurality of loads having different sizes.

200 Power converter 11 First converter 21 Second converter 31 Zero cross detection unit 32 Input voltage detection unit 33 Input current detection unit 34 Unbalance determination unit 35 DC voltage detection unit 36 Control unit 37 Storage unit

Claims (4)

A first converter that converts the three phases of a three-phase AC power supply to the first DC voltage,
A second converter that converts one or two phases of the three-phase AC power supply into a second DC voltage,
A determination unit for determining whether or not an imbalance has occurred between the three-phase currents input from the three-phase AC power supply to the first converter, and
A control unit that controls the first converter to eliminate the imbalance when the imbalance is occurring.
A power conversion device equipped with. The determination unit determines whether or not the imbalance has occurred based on the peak value of the three-phase current.
The power conversion device according to claim 1. The determination unit determines whether or not the imbalance has occurred based on the elapsed time from the zero cross point to the peak point in the current waveform of the three-phase current.
The power conversion device according to claim 1. An air conditioner comprising the power conversion device according to any one of claims 1 to 3.

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