JP6946041B2 - Power converter - Google Patents

Description

An embodiment of the present invention relates to a power conversion device.

A power conversion device including a multi-level circuit composed of a large number of semiconductor switching elements can output a multi-level stepped voltage waveform by turning on / off the semiconductor switching elements. In a multi-level circuit, the combination of a large number of semiconductor switching elements may increase the number of parts and increase the cost, weight, and size. However, when trying to reduce the number of parts in a conventional multi-level circuit, it may not be possible to output a voltage of a desired level.

Special Table 2007-508792

An object to be solved by the present invention is to provide a power conversion device capable of ensuring required performance while reducing the number of parts.

The power conversion device of the embodiment includes a first switching circuit, a second switching circuit, a third switching circuit, a fourth switching circuit, a first input terminal, a second input terminal, a first output terminal, and the like. It has a capacitor, a detection unit, and a control unit. The second switching circuit is connected to the first switching circuit via the first contact. The third switching circuit is connected to the second switching circuit via a second contact. The fourth switching circuit is connected to the third switching circuit via a third contact. The first input terminal is connected to a terminal on the opposite side of the terminal connected to the first contact in the first switching circuit. The second input terminal is connected to a terminal on the opposite side of the terminal connected to the third contact in the fourth switching circuit. The first output terminal is connected to the second contact. The capacitor is provided on the line connecting the first contact and the third contact. The detection unit detects the first voltage of the capacitor. The control unit causes the first voltage detected by the detection unit to approach a target voltage which is one-third of the second voltage supplied between the first input terminal and the second input terminal. It controls the first switching circuit, the second switching circuit, the third switching circuit, and the fourth switching circuit.

The figure which shows an example of the structure of the power conversion apparatus of embodiment. The figure which shows an example of the structure of the 1st circuit of embodiment. The figure which showed the function of the control part for controlling the voltage of the capacitor of an embodiment as a control block diagram. The figure which shows an example of the method of controlling a capacitor voltage of an embodiment. The figure which shows the simulation waveform which controlled the capacitor voltage of an embodiment. The figure which shows the simulation waveform of the output voltage of the power conversion apparatus of embodiment. FIG. 6 is an enlarged view of a part of FIG. FIG. 6 is an enlarged view of a part of FIG. FIG. 6 is an enlarged view of a part of FIG. FIG. 6 is an enlarged view of a part of FIG. FIG. 6 is an enlarged view of a part of FIG. The figure which shows the circuit structure of the power conversion apparatus of embodiment. The figure which shows the simulation waveform of the output voltage of the power conversion apparatus of embodiment. The figure which shows an example of the circuit structure of the power conversion apparatus 3 of 3rd Embodiment of Embodiment. The figure which shows an example of the method of controlling two capacitor voltages of an embodiment. The figure which shows the simulation waveform of the output voltage of the power conversion apparatus of embodiment. The figure which shows an example of the structure of the conventional multi-level circuit for one phase. The figure which shows an example of another configuration of the conventional multi-level circuit for one phase.

Hereinafter, the power conversion device of the embodiment will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram showing an example of the configuration of the power conversion device 1 of the first embodiment. The power conversion device 1 includes, for example, a first circuit 10, a control unit 20, a power supply unit 30, and a detection unit 40. The power conversion device 1 generates and outputs a plurality of levels of pulse voltages under the control of the control unit 20 based on the power supply voltage input from the power supply unit 30 to the first circuit 10.

FIG. 2 is a diagram showing an example of the configuration of the first circuit 10. The first circuit 10 includes, for example, a first switching circuit S1, a second switching circuit S2, a third switching circuit S3, a fourth switching circuit S4, a first output terminal O, a first input terminal P, and the like. A second input terminal N and a capacitor Cf1 are provided. In the first circuit 10, the first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are connected in series. The first circuit 10 is a multi-level circuit that outputs a voltage of four levels by a configuration including one capacitor Cf.

The first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are connected to the control unit 20, and are turned on (conducted or closed) or off (conducted or closed) by the control unit 20. It is controlled to the shut-off state or open state). The first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are semiconductor switching elements. In the semiconductor switching element, a freewheeling diode D is connected in parallel to an NMOS-FET 19 that operates on and off under the control of the control unit 20. The freewheeling diode D protects the NMOS-FET 19 by returning the backflow current generated at the time of switching to the power supply unit 30.

The source of the first switching circuit S1 is connected to the drain of the second switching circuit S2 via the first contact 11. A first input terminal P is connected to a drain which is a terminal on the opposite side of the source connected to the first contact 11 in the first switching circuit S1. The source of the second switching circuit S2 is connected to the drain of the third switching circuit S3 via the second contact 12. The source of the third switching circuit S3 is connected to the drain of the fourth switching circuit S4 via the third contact 13. A second input terminal N is connected to a source which is a terminal on the opposite side of the drain connected to the third contact 13 in the fourth switching circuit S4.

The first output terminal O is connected to the second contact. A capacitor Cf is provided on the line connecting the first contact 11 and the third contact 13. The capacitor Cf functions as a so-called flying capacitor. Further, the configuration shown in FIG. 2 shows one phase of the three-phase configuration of the first circuit 10. Hereinafter, the entire leg including the capacitor Cf is referred to as a flying capacitor leg. A detection unit 40 for detecting the capacitor voltage (first voltage) vcf is connected to the capacitor Cf.

In the first circuit 10, a DC power supply unit 30 is connected between the first input terminal P of the positive electrode and the second input terminal N of the negative electrode, and power is supplied by the supply voltage (second voltage) Vdc. .. Alternating current is output from the first output terminal O.

The first switching circuit S1 so that the capacitor voltage vcf detected by the detection unit 40 approaches the target voltage which is 1/3 of the supply voltage Vdc supplied between the first input terminal P and the second input terminal N. , The second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are controlled. A part or all of the functions of the control unit 20 are realized by, for example, a processor such as a CPU (Central Processing Unit) executing a program. Further, a part or all of the functions of the control unit 20 may be realized by hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or software. And hardware may work together.

Next, the control of the power conversion device 1 will be described. FIG. 3 is a diagram showing the function of the control unit 20 for controlling the voltage of the capacitor Cf as a control block diagram. The control unit 20 includes a filter processing unit 22, a comparison unit 23, and an offset processing unit 24.

When the capacitor voltage vcf is input to the control unit 20, the filter processing unit 22 performs a filter process to remove the switching frequency component. A method such as a low-pass filter or a moving average is used for this filtering, and when a low-pass filter is adopted, a value lower than the switching frequency is selected for the cutoff frequency. The control unit 20 may be configured without using a filter. The comparison unit 23 obtains the difference between the rated capacitor voltage v * cf, which is the target voltage, and the filtered capacitor voltage vcf #.

The offset processing unit 24 determines the rate of change αv * of the voltage command value v * by PI control as shown in the following equation (1) using the difference of the comparison unit 23.

αv * = KP · | vcf # -v * cf | + KI · ∫ | vcf # -v * cf | dt ... (1)

Here, KP is the proportional gain in the feedback control, and KI is the integrated gain in the feedback control.

The offset processing unit 24 multiplies the rate of change αv * by the voltage command value v * up to that point, adds or subtracts it from the voltage command value v * up to that point, and adds or subtracts a new voltage command value v * 1 or Derivation of v2 *. The voltage command value v * 1 is the voltage command value that drives the second switching circuit S2 and the third switching circuit S3, and the voltage command value v * 2 is the voltage command that drives the first switching circuit S1 and the fourth switching circuit S4. The value.

FIG. 4 is a diagram showing an example of a method of controlling the capacitor voltage vcf. The control unit 20 generates, for example, two triangular waves, a carrier wave (first carrier wave) car1 and a carrier wave (second carrier wave) car2. The two carrier waves car1 and car2 are generated in opposite phases to each other. The control unit 20 generates a switching control signal by using a triangular wave comparison method that compares the two carrier waves car1 and car2 with the command value v * of the generated voltage, and controls the power conversion device 1. The voltage command value v * may fluctuate according to the target waveform, with the waveform of the generated voltage value as the target waveform.

A basic control method of the power conversion device 1 by the two carrier waves car1 and car2 will be described. The control unit 20 generates two first carrier wave car1 wave and second carrier wave car2 having opposite phases, compares the first carrier wave and the second carrier wave car2 with the voltage command value, and is based on the result of comparison. The first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are controlled.

First, the control during the period (A) will be described. In the period (A), a plurality of levels of voltage are output without controlling the voltage command value v * of the indicated value. In this case, general pulse width modulation (PWM) is used for control. The control unit 20 compares the voltage command value v * with the carrier wave car1, and when the voltage command value v * is larger, turns on the second switching circuit S2 and turns off the third switching circuit S3. The control unit 20 compares the voltage command value v * with the carrier wave car1, and when the voltage command value v * is smaller, turns off the second switching circuit S2 and turns on the third switching circuit S3.

Further, the control unit 20 compares the voltage command value v * with the carrier wave car2, and when the voltage command value v * is larger, turns on the first switching circuit S1 and turns off the fourth switching circuit S4. do. The control unit 20 compares the voltage command value v * with the carrier wave car2, and when the voltage command value v * is smaller, turns off the first switching circuit S1 and turns on the fourth switching circuit S4. The switching states of the first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are complementary to each other.

When the above conditions are combined, the output voltage vout is output from the first output terminal O under the following conditions (1) to (4). Here, the output voltage vout is the potential difference of the first output terminal O with respect to the neutral point of the supply voltage Vdc.

(1) When the first switching circuit S1 = ON, the second switching circuit S2 = ON, the third switching circuit S3 = OFF, and the fourth switching circuit S4 = OFF, the output voltage vout has a voltage value that is half the DC voltage Vdc. Vdc / 2 (third voltage) is output.

(2) When the first switching circuit S1 = ON, the second switching circuit S2 = OFF, the third switching circuit S3 = ON, and the fourth switching circuit S4 = OFF, the output voltage vout has a voltage value Vdc / 2-vfc =. Vdc / 2-Vdc / 3 = Vdc / 6 (fourth voltage) is output.

(3) When the first switching circuit S1 = OFF, the second switching circuit S2 = ON, the third switching circuit S3 = OFF, and the fourth switching circuit S4 = ON, the output voltage vout has a voltage value −Vdc / 2 + vfc = −. Vdc + Vdc / 3 = -Vdc / 6 (fifth voltage) is output.

(4) When the first switching circuit S1 = OFF, the second switching circuit S2 = OFF, the third switching circuit S3 = ON, and the fourth switching circuit S4 = ON, the voltage value Vdc / 2 appears in the output voltage vout.

Although the case of the condition (4) is not described in FIG. 4, for example, when the value of the voltage command value v * drops and the condition is satisfied, the output value of the output voltage vout is the output value of the condition (4). It is output.

The control unit 20 switches the order in which the first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 are turned on or off and the conduction period, respectively, to switch the first output terminal O. From, the voltage value Vdc / 2 which is 1/2 of the supply voltage Vdc, the voltage value Vdc / 6 which is 1/6 of the supply voltage Vdc, the voltage value -Vdc / 6 which is -1/6 of the supply voltage Vdc, and the supply voltage Vdc. The voltage value of -1 / 2 of -Vdc / 2 is adjusted so that each of the four levels of voltage value is repeatedly output in a predetermined order, output period, and frequency.

When the current io output from the first output terminal O is in the direction shown in FIG. 2, the current flows into the capacitor Cf and the capacitor Cf is charged in the output period when the output voltage vout shows the voltage value Vdc / 6. NS. In the output period in which the output voltage vout indicates the voltage value −Vdc / 6, a current flows out from the capacitor Cf, and the capacitor Cf is discharged. Theoretically, the capacitor Cf is repeatedly charged and discharged, and the capacitor voltage vcf becomes constant. However, the actual capacitor voltage vcf is not constant due to various factors. Therefore, it is necessary to control the capacitor voltage vcf.

The control of the power conversion device 1 for adjusting the capacitor voltage vcf during the period (B) will be described. A case where the capacitor voltage vcf detected by the detection unit 40 is smaller than the target voltage and the capacitor voltage vcf is increased will be described.

The control unit 20 subtracts or adds the control amount vcon to the voltage command value v * to obtain the correction voltage command value v1 * and the correction voltage command value v2 *, respectively. Since the corrected voltage command value v1 * is smaller than the voltage command value v *, when the carrier wave car1 and the corrected voltage command value v1 * are compared, the output period in which the output voltage vout indicates the voltage value Vdc / 6 is in (A). It will be longer than the output period. This period is the period during which the capacitor Cf is charged.

Further, since the correction voltage command value v * 2 is larger than the voltage command value v *, when the carrier wave car2 and the correction voltage command value v2 * are compared, the output period in which the output voltage vout indicates the voltage value −Vdc / 6 is It is shorter than the output period in (a). This period is the period during which the capacitor Cf is discharged. When the output period in which the capacitor Cf is charged is long and the output period in which the capacitor Cf is discharged is short as compared with the case where control is not performed, the capacitor Cf is charged and the capacitor voltage vcf rises.

That is, the control unit 20 adjusts the output period of the voltage value Vdc / 6 in which the capacitor Cf is charged to be long, charges the capacitor Cf in the long adjusted output period, and discharges the capacitor Cf. By adjusting the output period of −Vdc / 6 to be short and discharging the capacitor Cf in the short adjusted output period, the capacitor voltage vcf is raised on average and the capacitor voltage vcf is controlled to the target voltage.

When the voltage of the capacitor Cf detected by the detection unit 40 is larger than the target voltage v * cf and the process of lowering the voltage of the capacitor Cf is performed, the sign of the control amount vcon is reversed, so that the output voltage vout is the voltage value. The output period indicating Vdc / 6 is shorter than the output period in (A). Then, the output period in which the capacitor Cf whose output voltage vout indicates the voltage value −Vdc / 6 is discharged is longer than the output period in (A).

That is, the control unit 20 adjusts so as to shorten the output period of the voltage value Vdc / 6 in which the capacitor Cf is charged, charges the capacitor Cf in the short adjusted period, and discharges the voltage value Vdc. By adjusting the output period of / 6 to be long and discharging the capacitor Cf in the long adjusted period, the capacitor voltage vcf is raised on average and the capacitor voltage vcf is controlled to the target voltage.

In this way, the control unit 20 sets each of the first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4 based on the capacitor voltage vcf detected by the detection unit 40. It is controlled by turning it on or off to adjust the capacitor voltage vcf to a voltage value of 1/3 of the supply voltage Vdc to the target voltage. Since the adjustment of the capacitor voltage vcf is performed by adjusting the on / off timing of each switching circuit in the process of outputting the four-level voltage, the power conversion device 1 is configured to include one capacitor Cf which is a flying capacitor. Can output 4 levels of voltage.

FIG. 5 is a diagram showing a simulation waveform in which the capacitor voltage vcf is controlled. Here, the DC voltage Vdc input to the first input terminal P and the second input terminal N is set to 360V, and the rated capacitor voltage v * cf is set to 120V. As shown, the capacitor voltage vcf is controlled to maintain the target voltage of 120V.

FIG. 6 is a diagram showing a simulation waveform of an output voltage vout when a sinusoidal voltage command value is given to the power conversion device 1. As shown in the figure, the power converter 1 outputs four levels of voltage. 7 to 11 are enlarged views of a part of FIG. 6. 7 to 11 show enlarged waveforms of the respective regions (a) to (e) in FIG. The output voltage is output at four levels of voltage according to the modulation rate of the output voltage output from the power converter 1.

The first circuit 10 described above illustrates a leg for one phase, but in the power conversion device 1, the total number of phases may be one phase or three phases. In the present embodiment, the power conversion device 1 illustrates the case where the capacitor Cf is composed of one stage, but it may be composed of two or more stages.

As described above, according to the power conversion device 1, it is possible to output a voltage of four levels by configuring a multi-level circuit including one capacitor Cf, and the device configuration can be simplified. As a result, according to the power conversion device 1, the filter unit such as the reactor is miniaturized to reduce the loss, and the attached cooler or the like is also miniaturized to reduce the size, cost, and loss of the device configuration. You can also.

(Second Embodiment)
The power conversion device 1 of the first embodiment shows a configuration in which a voltage of four levels is output by the first circuit 10 which is a flying capacitor leg. The power conversion device 2 of the second embodiment adds an NPC (Neutral-Point-Clamped) circuit to the first circuit 10 and outputs a voltage of 7 levels.

FIG. 12 is a diagram showing a circuit configuration of the power conversion device 2 of the second embodiment. In the following description, the same reference numerals and the same names will be used for the same configuration as the power conversion device 1 of the first embodiment, and duplicate description will be omitted as appropriate. The power conversion device 2 includes a first circuit 10 and a second circuit 50. The power conversion device 2 is configured by combining the first circuit 10 which is a flying capacitor leg and the second circuit 50, and illustrates the configuration of one leg. The second circuit 50 is an NPC circuit that outputs a voltage of three levels.

The second circuit 50 includes, for example, a fifth switching circuit S5, a sixth switching circuit S6, a seventh switching circuit S7, an eighth switching circuit S8, neutral point capacitors Cdc1 and Cdc2, and a third input terminal P2. A fourth input terminal N2 and a neutral point G are provided. In the second circuit 50, the fifth switching circuit S5, the sixth switching circuit S6, the seventh switching circuit S7, and the eighth switching circuit S8 are connected in series.

The source of the fifth switching circuit S5 is connected to the drain of the sixth switching circuit S6 via the fifth contact 51. A third input terminal P2 is connected to a drain which is a terminal on the opposite side of the source connected to the fifth contact 51 in the fifth switching circuit S5. The source of the sixth switching circuit S6 is connected to the drain of the seventh switching circuit S7 via the sixth contact 52. The source of the seventh switching circuit S7 is connected to the drain of the eighth switching circuit S8 via the seventh contact 53. A fourth input terminal N2 is connected to a source which is a terminal on the opposite side of the drain connected to the seventh contact 53 in the eighth switching circuit S8.

The first input terminal P of the first circuit 10 is connected to the fifth contact 51. The second input terminal N of the first circuit 10 is connected to the seventh contact 53. Neutral point capacitors Cdc1 and Cdc2 are connected in series on the line connecting the third input terminal P2 and the fourth input terminal N2. The neutral point capacitor Cdc1 and the neutral point capacitor Cdc2 are connected via the neutral point G. The neutral point G is connected to the sixth contact 52.

In the second circuit 50, a DC power supply unit 30 is connected between the third input terminal P2 of the positive electrode and the fourth input terminal N2 of the negative electrode, and power is supplied by the supply voltage (second voltage) Vdc. .. A pulse-modulated AC voltage is output from the first output terminal O.

The second circuit 50 conducts the entire first circuit 10 (flying capacitor leg) between P2-G or GN2. As a result, the output of the first circuit 10 is divided into a positive side output and a negative side output. In the power conversion device 2, a general NPC circuit control method is used as the control method of the second circuit 50. In the power conversion device 2, the method of controlling the voltage output of the first circuit 10 and the method of controlling the capacitor voltage vcf are the same as those of the first embodiment.

FIG. 13 is a diagram showing a simulation waveform of the output voltage vout of the power conversion device 2. According to the power conversion device 2, a voltage of 7 levels is output by combining the first circuit 10 and the second circuit 50. The reason why the voltage level fluctuates in the figure is that the load current flows through the power converter 2, so that the capacitor voltage vcf and the capacitor voltages vdc1 and vdc2 of the neutral point capacitors Cdc1 and Cdc2 of the second circuit 50 fluctuate. Because it is.

As described above, according to the power conversion device 2 of the second embodiment, it is possible to output a multi-level voltage while reducing the number of capacitors in the flying capacitor circuit and simplifying the device configuration.

(Third Embodiment)
The power conversion device 2 of the second embodiment illustrates a device that outputs multi-level power by combining the second circuit 50 (NPC circuit) and the first circuit 10 (flying capacitor leg). In the third embodiment, two flying capacitor legs are combined with the NPC circuit to further increase the multi-level and reduce the loss.

FIG. 14 is a diagram showing an example of the circuit configuration of the power conversion device 3 of the third embodiment. The power conversion device 3 is configured by further adding a flying capacitor leg to the configuration of the power conversion device 2 of the second embodiment.

The power conversion device 3 includes two first circuits 10A and 10B and a second circuit 50, whereby one leg is formed. The two first circuits 10A and 10B have basically the same configuration as the first circuit 10, and are connected in parallel to the second circuit 50. A reactor L is provided on a line connecting the second output terminals 12A and 12B of the first circuit 10A and 10B, respectively. The first output terminal O is connected to the reactor L. The reactor L suppresses the cross flow of the current between the two first circuits 10A and 10B.

The respective control methods of the first circuits 10A and 10B are the same as those of the first embodiment. In the power converter 3, the carrier waves that control the two first circuits 10A and 10B are out of phase between the two first circuits 10A and 10B. FIG. 15 is a diagram showing an example of a method of controlling two capacitor voltages. In the first circuits 10A and 10B, the phase shift is set to, for example, 90 °, but the phase shift is not limited to this, and other values may be used as long as the phase shift can be discriminated.

FIG. 16 is a diagram showing a simulation waveform of the output voltage vout of the power conversion device 3. The power conversion device 3 can output a voltage of 13 levels by the above configuration. The reason why the voltage level fluctuates in the figure is that the load current flows through the power converter 3, and the capacitors Cf and the capacitor voltages vdc1 and vdc2 of the neutral point capacitors Cdc1 and Cdc2 of the second circuit 50 fluctuate. Because there is.

As described above, according to the power converter 3, the two first circuits 10A and 10B are connected in parallel, so that a multi-level circuit having a larger number of voltage levels and low loss can be realized. According to the power converter 3, the two first circuits 10A and 10B are connected in parallel, and the currents are separated and passed through, so that the conduction loss of the flying capacitor leg can be halved, which is low. Loss can be realized.

Hereinafter, a comparison between the prior art and the power conversion device of the embodiment will be described.

FIG. 17 is a diagram showing an example of the configuration of the conventional multi-level circuit 100 for one phase. This circuit is a general flying capacitor circuit. The multi-level circuit 100 includes six switching circuits S101, S102, S103, S104, S105, S106 and two capacitors Cf101, Cf102.

The source of the first switching circuit S101 is connected to the drain of the second switching circuit S102 via the first contact 111. A first input terminal P is connected to a drain which is a terminal on the opposite side of the source connected to the first contact 111 in the first switching circuit S101. The source of the second switching circuit S2 is connected to the drain of the third switching circuit S103 via the second contact 112. The source of the third switching circuit S3 is connected to the drain of the fourth switching circuit S4 via the third contact 113.

The source of the fourth switching circuit S104 is connected to the drain of the fifth switching circuit S105 via the fourth contact 114. The source of the fifth switching circuit S105 is connected to the drain of the sixth switching circuit S106 via the fifth contact 115. A second input terminal N is connected to a source which is a terminal on the opposite side of the drain connected to the fifth contact 115 in the sixth switching circuit S106.

The first output terminal O is connected to the third contact 113. A capacitor Cf101 is provided on the line connecting the second contact 112 and the fourth contact 114. A capacitor Cf102 is provided on the line connecting the first contact 111 and the fifth contact 115. The capacitors Cf101 and Cf102 function as so-called flying capacitors.

Here, the capacitor Cf101 has a voltage of 1/3 of the DC voltage Vdc, and the capacitor Cf102 has a voltage of 2/3 of the Vdc. As a result, the multi-level circuit 100 can output a 4-level output voltage vout.

Further, when the capacitor Cf101 has a voltage of 1/4 of the DC voltage Vdc and the capacitor Cf102 has a voltage of 1/2 of Vdc, the multi-level circuit 100 can output a 5-level output voltage vout. In the multi-level circuit 100 that outputs 4 or 5 levels, 6 switching circuits S101 to S106 and 2 capacitors Cf101 and Cf102 are required for each phase.

On the other hand, according to the power conversion device 1 of the above embodiment, the multi-level circuit 100 has a circuit configuration in which the capacitor Cf102, the first switching circuit S101, and the sixth switching circuit S106 are omitted. If the capacitor Cf102, the first switching circuit S101, and the sixth switching circuit S106 are simply omitted from the multi-level circuit 100, the circuit outputs a voltage of three levels. According to the power conversion device 1, a configuration in which one capacitor Cf and four switching circuits are provided and the capacitor voltage vcf is controlled to 1/3 of the supply voltage Vdc outputs a four-level output voltage, so that the number of parts is increased. It is possible to secure the required performance while reducing the number of devices and simplifying the device configuration.

FIG. 18 is a diagram showing an example of another configuration of the conventional one-phase multi-level circuit 300. The multi-level circuit 300 is a circuit in which the neutral point clamp circuit 200 is combined with the flying capacitor circuit of FIG. The neutral point clamp circuit 200 is an NPC circuit having the same configuration as the second circuit 50, and outputs a voltage of three levels. The first input terminal P3 of the multi-level circuit 100 is connected to the fifth contact 201 of the neutral point clamp circuit 200. The second input terminal N3 of the multi-level circuit 100 is connected to the seventh contact 203. As a result, the multi-level circuit 300 includes two capacitors Cf101 and Cf102, ten switching circuits S101 to S110, and two neutral point capacitors Cdc1 and Cdc2 per phase.

When the neutral point clamp circuit 200 is combined with the multi-level circuit 100, an output voltage of 7 levels can be obtained when the multi-level circuit 100 has 4 levels, and a 9-level output voltage can be obtained when the multi-level circuit 100 has 5 levels.

On the other hand, according to the power conversion device 2 of the above embodiment, the multi-level circuit 300 has a circuit configuration in which the capacitor Cf102, the first switching circuit S101, and the sixth switching circuit S106 are omitted. If the capacitor Cf102, the first switching circuit S101, and the sixth switching circuit S106 are simply omitted from the multi-level circuit 300, the circuit outputs a voltage of five levels.

According to the power conversion device 2, the first circuit 10 having one capacitor Cf and four switching circuits and the second circuit 50 which is an NPC circuit are provided, and the capacitor voltage vcf is reduced to 1/3 of the supply voltage Vdc. Since a 7-level output voltage is output depending on the controlled configuration, it is possible to secure the required performance while reducing the number of parts and simplifying the device configuration.

According to at least one embodiment described above, the power conversion device 1 is connected to the first switching circuit 1, the first switching circuit S1, the second switching circuit S2 connected via the first contact 11, and the second switching. The third switching circuit S3 connected via the circuit S2 and the second contact 12, the fourth switching circuit S4 connected via the third switching circuit S3 and the third contact 13, and the first switching circuit S1. The first input terminal P connected to the terminal on the opposite side of the terminal connected to the 1 contact 11 and the second input terminal connected to the terminal on the opposite side to the terminal connected to the third contact 13 in the fourth switching circuit S4. Detects the input terminal N, the first output terminal O connected to the second contact 12, the capacitor Cf provided on the line connecting the first contact 11 and the third contact 13, and the first voltage of the capacitor Cf. The first voltage detected by the detection unit 40 and the detection unit 40 approaches the target voltage which is 1/3 of the second voltage supplied between the first input terminal P and the second input terminal N. By having a control unit 20 for controlling the first switching circuit S1, the second switching circuit S2, the third switching circuit S3, and the fourth switching circuit S4, the output voltage at a required level while reducing the number of parts is reduced. Can be output.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1, 2, 3 ... Power converters 10, 10A, 10B ... 1st circuit, 11 ... 1st contact, 12 ... 2nd contact, 12A ... 2nd output terminal, 12B ... 2nd output terminal, 13 ... 3rd Contact, 20 ... Control unit, 22 ... Filter processing unit, 23 ... Comparison unit, 24 ... Offset processing unit, 30 ... Power supply unit, 40 ... Detection unit, 50 ... Second circuit, 51 ... Fifth contact, 52 ... 6th Contact, 53 ... 7th contact, 100 ... Multi-level circuit, 200 ... Neutral point clamp circuit, 300 ... Multi-level circuit, Cdc1 ... Neutral point capacitor, Cdc2 ... Neutral point capacitor, Cf ... Capacitor, Cf1 ... Capacitor, Cf101 ... Capacitor, Cf102 ... Capacitor, D ... Reflux diode, L ... Reactor, N ... 2nd input terminal, N2 ... 4th input terminal, O ... 1st output terminal , P ... 1st input terminal, P2 ... 3rd input Terminal, S1 ... 1st switching circuit, S2 ... 2nd switching circuit, S3 ... 3rd switching circuit, S4 ... 4th switching circuit, S5 ... 5th switching circuit, S6 ... 6th switching circuit, S7 ... 7th switching circuit , S8 ... 8th switching circuit, S101 ... switching circuit, S102 ... switching circuit, S103 ... switching circuit, S104 ... switching circuit, S105 ... switching circuit, S106 ... switching circuit, 111 ... first contact, 112 ... second contact, 113 ... 3rd contact, 113 ... 3rd contact, 114 ... 4th contact, 201 ... 5th contact, 202 ... 6th contact, 203 ... 6th contact

Claims (10)

The first switching circuit and
A second switching circuit connected to the first switching circuit via the first contact,
A third switching circuit connected to the second switching circuit via a second contact,
A fourth switching circuit connected to the third switching circuit via a third contact,
A first input terminal connected to a terminal opposite to the terminal connected to the first contact in the first switching circuit, and a first input terminal.
A second input terminal connected to a terminal opposite to the terminal connected to the third contact in the fourth switching circuit, and a second input terminal.
The first output terminal connected to the second contact and
A capacitor provided on the line connecting the first contact and the third contact,
A detector that detects the first voltage of the capacitor and
The first switching circuit so that the first voltage detected by the detection unit approaches a target voltage which is 1/3 of the second voltage supplied between the first input terminal and the second input terminal. A control unit that controls the second switching circuit, the third switching circuit, and the fourth switching circuit.
Power converter. The control unit switches the order in which the first switching circuit, the second switching circuit, the third switching circuit, and the fourth switching circuit are turned on or off and the conduction period, respectively, to switch the first output terminal. Therefore, control is performed so that each of the four levels of voltage values is repeatedly output in a predetermined order and in an output period.
The power conversion device according to claim 1. When the first voltage detected by the detection unit is lower than the target voltage, the control unit adjusts to lengthen the output period in which the capacitor is charged and the output period in which the capacitor is discharged. The first voltage is raised by adjusting the voltage to be shorter.
The power conversion device according to claim 2. When the first voltage detected by the detection unit is higher than the target voltage, the control unit adjusts to shorten the output period during which the capacitor is charged, and at the same time, the output period during which the capacitor is discharged. By adjusting to lengthen, the first voltage is lowered.
The power conversion device according to claim 2 or 3. Wherein the control unit generates a reverse phase first carrier wave and a second carrier wave of two mutually, the first switching based on the comparison result of the first carrier wave and the second carrier wave and voltage command value Controls the circuit, the second switching circuit, the third switching circuit, and the fourth switching circuit.
The power conversion device according to any one of claims 2 to 4. When the first voltage detected by the detection unit is lower than the target voltage, the control unit lowers the command value to adjust the output period for charging the capacitor to be longer, and raises the command value. The output period during which the capacitor is discharged is adjusted to be short, and the first voltage is increased.
The power conversion device according to claim 5. When the first voltage detected by the detection unit is higher than the target voltage, the control unit raises the command value to shorten the output period during which the capacitor is charged, and lowers the command value. The output period during which the capacitor is discharged is adjusted to be longer, and the first voltage is lowered.
The power conversion device according to claim 5 or 6. The first switching circuit and
A second switching circuit connected to the first switching circuit via the first contact,
A third switching circuit connected to the second switching circuit via a second contact,
A fourth switching circuit connected to the third switching circuit via a third contact,
A first input terminal connected to a terminal opposite to the terminal connected to the first contact in the first switching circuit, and a first input terminal.
A second input terminal connected to a terminal opposite to the terminal connected to the third contact in the fourth switching circuit, and a second input terminal.
The first output terminal connected to the second contact and
A capacitor provided on the line connecting the first contact and the third contact,
A detector that detects the first voltage of the capacitor and
The first switching circuit so that the first voltage detected by the detection unit approaches a target voltage which is 1/3 of the second voltage supplied between the first input terminal and the second input terminal. A first circuit including the second switching circuit, the third switching circuit, and a control unit for controlling the fourth switching circuit.
With the 5th switching circuit
The sixth switching circuit connected to the fifth switching circuit via the fourth contact, and the sixth switching circuit.
A seventh switching circuit connected to the sixth switching circuit via a fifth contact,
The eighth switching circuit connected to the seventh switching circuit via the sixth contact, and the eighth switching circuit.
A third input terminal connected to the opposite side of the terminal connected to the fourth contact in the fifth switching circuit, and a third input terminal.
A fourth input terminal connected to the opposite side of the terminal connected to the sixth contact in the eighth switching circuit, and a fourth input terminal.
A fifth input terminal connected to the fifth contact, the fourth contact and the first input terminal are connected, and the sixth contact and the second input terminal are connected. With 2 circuits,
Power converter. With the second circuit
A plurality of the first circuits in which the fourth contact and the first input terminal are connected and the sixth contact and the second input terminal are connected.
A fourth circuit including a second output terminal in which a plurality of the first output terminals of the first circuit are connected to each other via a reactor is provided.
The power conversion device according to claim 8. Each of the control units of the plurality of first circuits generates two first carrier waves and second carrier waves having opposite phases, and from the first carrier wave, the second carrier wave, and the first output terminal. Based on the result of comparing the difference between the output voltage and the command value of the output voltage, the first switching circuit, the second switching circuit, the third switching circuit, and the fourth switching circuit are turned on or off at predetermined intervals. The output voltage is adjusted by switching the order of each, and the carrier waves of the plurality of first circuits have a phase difference from each other.
The power conversion device according to claim 9.

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