WO2021070279A1 - Power conversion device - Google Patents

Abstract

A power conversion device (100) is provided with: an AC/DC converter (10) that converts AC power from an AC circuit (1) into DC power, and performs power factor improvement control; a DC/DC converter (20) that performs voltage conversion for the DC power; and a DC capacitor (3) that is connected between the AC/DC converter (10) and the DC/DC converter (20), wherein a ripple voltage command value is generated for controlling the DC voltage of the DC capacitor (3) to a DC voltage on which voltage pulsation having a waveform exhibiting a minimum value at the zero cross phase and a maximum value at the peak phase of the AC voltage from the AC circuit (1) is superposed, and the AC/DC converter (10) and/or the DC/DC converter (20) is controlled by using this ripple voltage command value.

Description

Power converter

This application relates to a power conversion device.

Conventionally, an AC / DC converter that controls the power factor improvement of an AC power supply and converts the AC power from the AC power supply into DC power and a DC side connected to the DC side of the AC / DC converter to perform voltage conversion of the DC power. A power conversion device including a DC / DC converter to be performed and a DC capacitor connected between the positive and negative DC bus lines between the AC / DC converter and the DC / DC converter is disclosed. In such a power conversion device having a configuration in which an AC / DC converter and a DC / DC converter that convert power with an AC power supply power factor improvement control are connected via a DC capacitor, the aim is to reduce the size of the device. When the capacity of the DC capacitor is reduced, the ripple voltage of the DC voltage that fluctuates at a frequency twice the power supply frequency increases, especially when the AC power supply is single-phase. An increase in the ripple voltage causes an increase in the switching loss of the element and an increase in the size of the device due to an increase in the withstand voltage of the parts used. Therefore, the following power conversion devices capable of suppressing the ripple voltage without increasing the capacity of the DC capacitor are disclosed.

That is, in the conventional power converter, in the AC / DC converter and the control circuit that controls the output of the DC / DC converter, the AC current command that becomes the minimum value at the zero cross phase and the maximum value at the peak phase of the single-phase AC power supply. Is superimposed on the DC current command to generate the output current command of the DC / DC converter, and the output control of the DC / DC converter is performed using the output current command to control the allowable power pulsation of the DC / DC converter. Is output from (see, for example, Patent Document 1).

International Publication No. WO2016 / 075996 (paragraphs [0010] to [0055], FIGS. 1 to 12)

In the above-mentioned conventional power conversion device, the ripple voltage in the DC capacitor is suppressed without increasing the capacity of the DC capacitor by superimposing the AC current component of the set waveform on the output current of the DC capacitor. .. However, in the power conversion device having such a configuration, the ripple voltage increases when the capacity of the DC capacitor is further reduced, so that there is a limit to reducing the capacity of the DC capacitor. Therefore, there is a problem that the device cannot be sufficiently miniaturized.
The present application discloses a technique for solving the above-mentioned problems, and an object of the present application is to provide a compact power conversion device capable of reducing the capacity of a DC capacitor.

The power converter disclosed in the present application is
An AC / DC converter that converts AC power from an AC circuit into DC power and controls the power factor improvement of the AC power, and a DC / DC that is connected to the DC side of the AC / DC converter and performs voltage conversion of DC power. A DC converter, a DC capacitor connected between the positive and negative DC bus lines between the AC / DC converter and the DC / DC converter, a control unit that controls the AC / DC converter and the DC / DC converter, and the like. With
The control unit controls the DC voltage of the DC capacitor to a DC voltage on which a voltage pulsation having a waveform having a waveform that becomes a minimum value at the zero cross phase and a maximum value at the peak phase of the AC voltage from the AC circuit is superimposed. A command value is generated, and at least one of the AC / DC converter and the DC / DC converter is controlled by using the ripple voltage command value.
It is a thing.

According to the power conversion device disclosed in the present application, the capacity of the DC capacitor can be reduced, so that a small power conversion device can be provided.

It is a block diagram which shows the schematic structure of the power conversion apparatus according to Embodiment 1. It is a control block diagram of the control circuit of the power conversion apparatus according to Embodiment 1. FIG. It is a control block diagram of the voltage ripple command generator according to Embodiment 1. FIG. FIG. 5 is a control block diagram of a power factor command calculator according to the first embodiment. FIG. 5 is a control block diagram of an intermediate voltage command calculator according to the first embodiment. It is a figure which shows the energy secured by the DC capacitor in the power conversion apparatus of the comparative example. It is a figure which shows the energy secured by the DC capacitor of the power conversion apparatus according to Embodiment 1. FIG. It is a figure which shows the simulation waveform using the power conversion apparatus by this Embodiment 1. It is a figure which shows the simulation waveform using the power conversion apparatus by the comparative example. It is a block diagram which shows the schematic structure of the power conversion apparatus according to Embodiment 1. It is a control block diagram of the control circuit of the power conversion apparatus according to Embodiment 2. It is a control block diagram of the intermediate voltage command arithmetic unit according to Embodiment 2. It is a control block diagram of the power factor command calculator according to Embodiment 2. It is a control block diagram of the output current command arithmetic unit according to Embodiment 2. It is a figure which shows the simulation waveform using the power conversion apparatus by this Embodiment 2. It is a figure which shows the simulation waveform using the power conversion apparatus by the comparative example 1. FIG. It is a figure which shows the simulation waveform using the power conversion apparatus by the comparative example 2. FIG. It is a block diagram which shows the schematic structure of the power conversion apparatus according to Embodiment 3.

Embodiment 1.
FIG. 1 is a block diagram showing a schematic configuration of the power conversion device 100 according to the first embodiment.
As shown in FIG. 1, the power conversion device 100 is provided between a single-phase AC power supply as an AC circuit (hereinafter, simply referred to as an AC power supply 1) and a load 5, and supplies AC power from the AC power supply 1 to DC. It includes a main circuit that converts it into electric current and outputs it to the load 5, and a control circuit 30 as a control unit that controls the main circuit.

The main circuit consists of an AC / DC converter 10 that converts AC power into DC power, a DC / DC converter 20 that is connected to the DC output side of the AC / DC converter 10 and performs DC power voltage conversion, and the AC / DC converter 20. A DC capacitor 3 connected between positive and negative DC bus wires between the DC converter 10 and the DC / DC converter 20 is provided.
Further, the main circuit includes a current limiting reactor 2 on the input side and a smoothing capacitor 4 on the output side.

In this case, the AC / DC converter 10 is composed of a semi-bridgeless circuit, and includes diode elements 10a and 10b and semiconductor switching elements 10c and 10d.
In this case, the DC / DC converter 20 includes a full-bridge inverter 21 composed of an isolated full-bridge converter circuit and composed of semiconductor switching elements 21a, 21b, 21c, and 21d, a high-frequency isolated transformer 23 as an insulating transformer, and the like. It includes a full-wave rectifier circuit 22 composed of diode elements 22a, 22b, 22c, and 22d, and a reactor 24 for current control.
The high-frequency isolation transformer 23 has a primary coil 23a connected to the AC output side of the full bridge inverter 21 and a secondary coil 23b connected to the AC input side of the full-wave rectifier circuit 22.

The positive terminal of the DC capacitor 3 is connected to the positive DC bus connecting the P terminal on the DC output side of the AC / DC converter 10 and the P terminal on the DC input side of the DC / DC converter 20.
Further, the N-side terminal of the DC capacitor 3 is connected to a negative-side DC bus connecting the N-terminal on the DC output side of the AC / DC converter 10 and the N-terminal on the DC input side of the DC / DC converter 20. The DC capacitor 3 has an energy buffer function and smoothes the difference between the power input by the AC / DC converter 10 and the power output by the DC / DC converter 20.

Further, the AC voltage vac of the AC power supply 1, the voltage Vdc of the DC capacitor 3, and the load voltage Vout which is the voltage of the smoothing capacitor 4 are detected by the voltage sensor and input to the control circuit 30. Further, the AC current iac from the AC power supply 1 and the load current iout flowing through the load 5 are detected by the current sensors and input to the control circuit 30.

The semiconductor switching elements used in the AC / DC converter 10 and the full bridge inverter 21 are IGBTs (Insulated Gate Bipolar Transistor) in which diodes are connected in antiparallel, and MOSFETs (METal) in which diodes are connected between the source and drain. It is preferable to use an Diode Semiconductor File Effect Inverter) or the like. Further, as the feedback diode, a diode built in the IGBT or MOSFET may be used, or a diode may be separately provided externally.

Further, the DC capacitor 3 can be composed of an aluminum electrolytic capacitor, a film capacitor, a ceramic capacitor, a tantalum capacitor, an EDLC (Electric double-layer capacitor electric double layer capacitor) and the like. Further, it may be composed of a battery such as a lithium ion battery.
Further, the load 5 may be an electric device driven by a DC voltage, or a power storage element such as a battery or a capacitor.

The control circuit 30 has a gate signal G10 (G10c, G10d) to the semiconductor switching elements 10c and 10d, and a gate signal to the semiconductor switching elements 21a, 21b, 21c, 21d based on the voltage and current information detected by each sensor. G21 (G21a, G21b, G21c, G21d) is generated to control the AC / DC converter 10 and the DC / DC converter 20, respectively.
In the following description, Vac is the voltage effective value of the AC power supply 1, Iac is the current effective value of the AC power supply 1, Vdc is the DC voltage component of the DC capacitor 3, Vout is the voltage effective value of the load 5, and Iout is the load 5. Each is shown as an effective value of the current flowing through.

Next, the operation of each part constituting the power conversion device 100 will be described.
The AC / DC converter 10 has a leg in which diode elements 10a and 10b are connected in series with each other, and a leg in which semiconductor switching elements 10c and 10d are connected in series with each other. Then, the AC / DC converter 10 boosts the voltage while controlling the AC current iac flowing in the current limiting reactor 2 with a high power factor by high-frequency switching of these legs, and outputs DC power. It is a power factor converter.

In this power factor control, the AC / DC converter 10 applies a positive voltage to the diversion reactor 2 in a mode in which the diode element 10a and the semiconductor switching element 10c are turned on in the positive AC cycle of the AC voltage Vac. Then, a negative voltage is applied to the current limiting reactor 2 in a mode in which the diode element 10a and the semiconductor switching element 10d are turned on. Further, in the negative AC cycle, a mode in which the diode element 10b and the semiconductor switching element 10d are turned on and a mode in which the diode element 10b and the semiconductor switching element 10c are turned on are used. In this way, the increase / decrease of the current flowing through the current limiting reactor 2 is controlled, and the AC current iac is controlled at a high power factor so that the input power factor from the AC power supply 1 becomes 1.

The DC / DC converter 20 controls the output DC voltage from the AC / DC converter 10 via the DC capacitor 3 in the full bridge inverter 21 to turn on / off the semiconductor switching elements 21a to 21d based on the gate signal G21. Converts to a high-frequency AC voltage. After that, the high-frequency AC voltage is boosted or stepped down by the secondary side coil 23b while being electrically insulated, and rectified to a DC voltage by the full-wave rectifier circuit 22. After rectification, the high frequency component is removed by the reactor 24 for current control and the smoothing capacitor 4, and DC power is supplied to the load 5.

Hereinafter, the configuration of the control circuit 30 and the outline of its operation will be described with reference to FIG.
FIG. 2 is a control block diagram of the control circuit 30 of the power conversion device 100 according to the first embodiment.
The control circuit 30 includes a voltage ripple command generator 40, a power factor command calculator 60, an intermediate voltage command calculator 80, and gate signal generators 31 and 32.

The voltage ripple command generator 40 uses the AC voltage vac and the load voltage Vout detected by the sensor to control the DC voltage Vdc of the DC capacitor 3 to the DC voltage on which the desired voltage pulsation is superimposed. Generate the value Vdc_ripple (details below).
The generated ripple voltage command value Vdc_ripple is input to the power factor command calculator 60 and the intermediate voltage command calculator 80.

The power factor command calculator 60 uses the input ripple voltage command value Vdc_ripple and the AC current iac, AC voltage vac, and DC voltage Vdc detected by the sensor to increase the power factor of the AC current iac. Generates a duty ratio signal Duty_PFC to be controlled to.
The intermediate voltage command calculator 80 uses the input ripple voltage command value Vdc_ripple and the load current iout, load voltage Vout, and DC voltage Vdc detected by the sensor to command the DC voltage Vdc of the DC capacitor 3. Generates a duty ratio signal Duty_Vdc to follow.

The gate signal generator 31 controls the gate signals G10c and G10d to the semiconductor switching elements 10c and 10d by PWM (Pulse Width Modulation) control for comparing the duty ratio signal Duty_PFC calculated by the power factor command calculator 60 with the carrier frequency. Is output.
The gate signal generator 32 gates to the semiconductor switching elements 21a, 21b, 21c, and 21d by PWM (Pulse Width Modulation) control for comparing the duty ratio signal Duty_Vdc calculated by the intermediate voltage command calculator 80 with the carrier frequency. The signals G21a, G21b, G21c, and G21d are output.
The carrier frequency may be a sawtooth wave or a triangular wave.

As described above, the power factor command calculator 60 and the intermediate voltage command calculator 80 use the ripple voltage command value Vdc_ripple generated by the voltage ripple command generator 40 to convert the AC / DC converter 10 and the DC / DC converter 20, respectively. Generate a gate signal for control. As a result, a circuit operation that follows the ripple voltage command value Vdc_ripple is realized.

The control circuit 30 of the first embodiment assumes a case where a constant voltage source such as a battery is connected as the load 5, and the control circuit 30 shown in FIG. 2 has an output voltage (load voltage Vout). ) Is a fixed value, and the input AC current iac is controlled to an arbitrary value.

Next, the details of the operation performed by the control circuit 30 configured as described above will be described.
In the description of the operation details, the detailed configuration of each part constituting the control circuit 30 will also be described.
First, the configuration of the voltage ripple command generator 40 will be described with reference to FIG.
FIG. 3 is a control block diagram of the voltage ripple command generator 40 according to the first embodiment.

The voltage ripple command generator 40 generates the ripple voltage command value Vdc_ripple by using the AC voltage Vac of the AC power supply 1 and the load voltage Vout of the load 5 detected by the sensor.
As described above, the ripple voltage command value Vdc_ripple is a voltage command value for controlling the DC voltage Vdc of the DC capacitor 3 to a DC voltage on which a desired voltage pulsation is superimposed.

This ripple voltage command value Vdc_ripple is generated based on the ripple command value Ripple represented by the following equation (1).
Ripple = ((√2Vac- (Vout / N)) * K1) sinωt + (Vout / N) ... (1)
However, N is the turns ratio of the high-frequency isolation transformer 23, and K1 is a correction coefficient of 1 or more.

Hereinafter, the operation of generating the ripple voltage command value Vdc_ripple performed by the voltage ripple command generator 40 will be described.
As shown in FIG. 3, first, the voltage ripple command generator 40 obtains the DC of the DC capacitor 3 obtained by dividing the detected peak value of the AC voltage Vac and the detected load voltage Vout by the turns ratio N. The deviation 41 compared with the voltage Vdc is calculated.

Next, the signal 42 is generated by multiplying the deviation 41 by the correction coefficient K1 (K ≧ 1) set in the voltage corrector 49.
Next, the PLL calculator 43 multiplies the signal 42 by a sine wave sin (ωt) having the same period as the AC voltage vac to generate a sine wave signal 44 synchronized with the AC voltage vac.
Next, the absolute value generator 45 generates a full-wave rectified waveform signal 46 by full-wave rectifying the sine wave signal 44. Then, the Ripple command value represented by the above equation (1) is generated by adding the DC voltage Vdc of the DC capacitor 3 obtained from the detected load voltage Vout to the full-wave rectified waveform signal 46.

The Ripple command value derived in this way is the voltage command value that controls the DC voltage Vdc of the DC capacitor 3 to the DC voltage on which the voltage pulsation of the waveform obtained by full-wave rectifying the sine wave synchronized with the AC voltage vac is superimposed. Become.
Here, the amplitude of the voltage pulsation at the Ripple command value is determined by (√2Vac- (Vout / N)) * K1) as shown by the above equation (1).

Next, the ripple range limiter 47 limits the upper limit of the voltage pulsation to be equal to or less than the set first value by using the correction coefficient K2 (K2 ≧ 1) set by the voltage corrector 48. The ripple voltage command value Vdc_ripple is generated by limiting the lower limit value of the voltage pulsation to be equal to or higher than the set second value.
By following this process, the voltage pulsation superimposed on the DC voltage Vdc is not only the case where it becomes a full-wave rectified waveform of a sine wave, but also the DC waveform part where the peak part of the full-wave rectified waveform of a sine wave is cut. In some cases, the waveform may be a mixture of the sine wave portion. In any of these cases, the superimposed voltage pulsation is a voltage pulsation having a waveform that is minimized at the zero cross phase of the AC voltage vac and maximized at the peak phase.

The first value that limits the upper limit of the voltage pulsation is set from the withstand voltage of the semiconductor element. As a result, it is possible to prevent the DC voltage vdc from pulsating beyond the withstand voltage of the semiconductor element, suppress the increase in size of the device due to the increase in withstand voltage, and reduce the switching loss.
The second value that limits the lower limit of the voltage pulsation is set by multiplying the load voltage Vout by the turns ratio N by the correction coefficient K2 (K2 ≧ 1). As a result, voltage pulsation that is significantly lower than the DC voltage Vdc can be suppressed, and boost control by the AC / DC converter 10 can be compensated for over one AC cycle.
Further, the first value and the second value may be determined according to the computing power and the response speed of the control circuit 30. This enables stable control according to the performance of the control circuit 30 used.

The control for adjusting the ripple voltage command value Vdc_ripple so that the maximum value of the superimposed voltage pulsation is equal to or less than the first value is called the maximum value limit control, and the minimum value of the superimposed voltage pulsation is the second value. The control for adjusting the ripple voltage command value Vdc_ripple so as to exceed the value is called the minimum value limit control.
Further, the maximum value adjustment control and the minimum value adjustment control are not limited to those that perform both at the same time, and at least one of the maximum value adjustment control and the minimum value adjustment control may be performed.
For example, if the amplitude of the voltage pulsation in the Ripple command value is within the voltage range from the second value to the first value, the limitation by the maximum value adjustment control and the minimum value adjustment control becomes unnecessary.

Next, the generation of the duty ratio signal Duty_PFC by the power factor command calculator 60 using the ripple voltage command value Vdc_ripple will be described with reference to FIG.
FIG. 4 is a control block diagram of the power factor command calculator 60 according to the first embodiment.

First, the power factor command calculator 60 uses the PLL calculator 61 to generate a sine wave sin (ωt) having the same period as the AC voltage vac with respect to the effective value command Iac * of the AC current iac as the first current command value. It is multiplied to generate a sine wave signal 62 synchronized with the AC voltage vac1. After that, a signal 64 indicating the deviation between the absolute values of the alternating current iac detected by the sensor and the sine wave signal 62 is generated. The voltage command 65 is generated by controlling the signal 64 by PI so as to follow the command value.

Normalize by dividing the generated voltage command 65 by the ripple voltage command value Vdc_ripple. After that, by adding the signal of the FF (Feed Field) control calculator 66, a duty ratio signal Duty_PFC capable of responding to a steep fluctuation of the FB (Feed Back) value is generated.

The calculation of the FF control calculator 66 is shown in the following equation (2).
Duty_FF = 1- | Vac | / (Vdc_ripple + Vdc *) ... (2)

Next, the calculation of the duty ratio signal Duty_Vdc by the intermediate voltage command calculator 80 using the ripple voltage command value Vdc_ripple will be described with reference to FIG.
FIG. 5 is a control block diagram of the intermediate voltage command calculator 80 according to the first embodiment.
The intermediate voltage command calculator 80 calculates the duty ratio signal Duty_Vdc such that the intermediate capacitor voltage Vdc follows the command value.

First, the intermediate voltage command calculator 80 generates a control value 82 by P-controlling the deviation 81 between the DC voltage Vdc detected by the sensor and the ripple voltage command value Vdc_ripple. By PI-controlling the deviation 83 between the control value 82 and the load current iout detected by the sensor, a control value 84 that controls the current flowing through the reactor 24 for current control is generated.
Next, the voltage command signal 85 obtained by adding the load voltage Vout to the control value 84 is standardized by dividing the DC capacitor voltage command value Vdc_ripple by the winding ratio N to generate the duty ratio signal Duty_Vdc. ..

The gate signal generator 31 generates gate signals G10 (G10c, G10d) to the semiconductor switching elements 10c and 10d by PWM-controlling the duty ratio signal Duty_PFC and the carrier wave.
The gate signal generator 32 generates gate signals G21 (G21a, G21b, G21c, G21d) to the semiconductor switching elements 21a, 21b, 21c, 21d by PWM-controlling the duty ratio signal Duty_Vdc and the carrier wave.

The AC / DC converter 10 driven based on the duty ratio signal Duty_PFC thus generated controls the alternating current iac to a high power factor and an arbitrary value.
Further, the DC / DC converter 20 driven based on the duty ratio signal Duty_Vdc generated in this way controls the DC voltage Vdc of the DC capacitor 3 to a DC voltage on which a desired voltage pulsation is superimposed.

Hereinafter, the energy secured by the DC capacitor of the power conversion device 100 of the present embodiment will be described in comparison with the power conversion device of the comparative example.
FIG. 6 is a diagram showing the energy secured by the DC capacitor in the power conversion device of the comparative example.
FIG. 7 is a diagram showing energy secured by the DC capacitor 3 in the power conversion device 100 of the present embodiment.
In both figures, the waveforms of the input power Pin, the output power Pout, the AC current iac, and the AC voltage vac, which are input to the DC capacitor, are shown, and the energy secured by the DC capacitor is shown in shaded areas.

The power conversion device of the comparative example shown in FIG. 6 has a circuit configuration in which an AC / DC converter and a DC / DC converter that perform power conversion accompanied by power factor improvement control of an AC power supply are connected via a DC capacitor. However, it is assumed that the voltage of the DC capacitor 3 is not controlled as in the control circuit 30 of the present embodiment.
Further, in FIG. 6, the DC power (output power Pout) is set to an ideal waveform, and the pulsation of the frequency component twice the AC voltage is not considered.

In the power conversion device of the comparative example shown in FIG. 6, the input power Pin is the minimum in the vicinity of the zero cross phase of the AC voltage vac, and as shown by the shaded area, the energy secured by the DC capacitor 3 with respect to the output power Pout is It turns out that it is big. Further, since the input power Pin becomes maximum in the vicinity of the peak phase of the AC voltage vac, it can be seen that the energy secured by the DC capacitor 3 with respect to the output power Pout is large even in this case as shown by the shaded area.

On the other hand, in the power conversion device 100 of the present embodiment, the load current iout also pulsates due to the pulsation of the DC voltage Vdc synchronized with the AC voltage vac, and the output power Pout pulsates in synchronization with the AC voltage vac. Since the power output by the DC / DC converter 20 pulsates in synchronization with the AC voltage vac in this way, most of the AC power from the AC power supply 1 can be directly output to the load 5. Therefore, as shown in FIG. 7, the energy secured by the DC capacitor 3 with respect to the output power Pout is small. Since the amplitude of the voltage pulsation superimposed on the DC voltage Vdc is adjusted as shown in the equation (1), the power pulsation in the output power is also within the permissible range.

Hereinafter, the effect of the power conversion device 100 of the present embodiment will be described in comparison with the power conversion device of the comparative example.
FIG. 8 is a diagram showing main waveforms in the simulation results when the power conversion device 100 of the present embodiment is used.
FIG. 9 is a diagram showing main waveforms in the simulation results when the power conversion device of the comparative example is used.

In the power conversion device of the comparative example, the capacity of the DC capacitor capable of obtaining the same power factor as the power conversion device 100 of the present embodiment is used.
As an operating condition, it is assumed that the input power is several kW and a constant voltage source is connected to the load 5.
In both figures, in order from the top, a diagram showing the AC voltage vac, the DC voltage Vdc of the DC capacitor 3, and the load voltage Vout, a diagram showing the AC current iac, and a diagram showing the load current iout are shown side by side.

The capacity of the DC capacitor used in the power conversion device of the comparative example of FIG. 8 is 1 mF, and the capacity of the DC capacitor 3 used in the power conversion device 100 of the present embodiment of FIG. 9 is 10 μF.
Therefore, it can be seen that the capacity of the DC capacitor 3 can be reduced to 1/100 by using the power conversion device 100 of the present embodiment.

Next, the reason why the amplitude of the voltage pulsation at the Ripple command value is determined by (√2Vac- (Vout / N)) * K1 as shown by the above equation (1) will be described with reference to FIG.
The amplitude of the voltage pulsation in the Ripple command value shown in the equation (1) is the difference between the maximum value of the detected AC voltage Vac and the value obtained by dividing the load voltage Vout by the turns ratio N (Vout / N) (FIG. 8). (Shown as B in the above) is multiplied by one or more correction coefficients K1.
As a result, the amplitude of the voltage pulsation of the DC voltage Vdc becomes B or more. That is, the maximum value of the voltage pulsation of the DC voltage Vdc is equal to or higher than the maximum value of the AC voltage vac.

By adjusting the amplitude of the voltage pulsation in the Ripple command value in this way, even if the voltage pulsation is superimposed on the DC voltage Vdc, it is possible to prevent the DC voltage Vdc from falling below the AC voltage vac due to this pulsation. In this way, since the DC voltage Vdc can be maintained above the AC voltage vac over the entire AC cycle, the boosting operation in the AC / DC converter 10 can always be realized.
In the voltage waveform shown in FIG. 8, it can be seen that the boosting operation of the AC / DC converter 10 can always be realized, and the AC current iac can be operated in a state close to the power factor 1.

The closer the correction coefficient K is to 1, the smaller the amplitude of the voltage pulsation of the DC voltage Vdc can be minimized, but the margin of control becomes smaller. Therefore, it is preferable to set a value of 1 or more including a margin for noise or the like. ..

Here, it is assumed that the capacity of the DC capacitor of the power converter of the comparative example is reduced in the operating state shown in FIG. In this case, the amplitude of the ripple voltage of the double frequency component of the AC power supply 1 generated in the voltage of the DC capacitor increases, and when the lower limit of the ripple voltage becomes equal to or lower than the AC voltage, a state of step-down operation occurs. In the circuit system in which the AC / DC converter cannot step down, the power factor control of the AC current iac becomes unstable and the control fails. Therefore, in the power conversion device of the comparative example, there is a limit to the capacity reduction of the DC capacitor, and it becomes difficult to significantly reduce the capacity.

Since the load 5 serves as a constant voltage source, a current in which a pulsating component superimposed on the voltage of the DC capacitor flows flows in both the power conversion device 100 of the present embodiment and the power conversion device of the comparative example. As shown in FIGS. 8 and 9, the power conversion device 100 of the present embodiment has a larger amplitude of voltage pulsation at the DC voltage Vdc. Therefore, the pulsation of the current flowing through the load 5 also becomes large, but the pulsation of the current can be within the permissible range by adjusting the amplitude of the voltage pulsation.

In FIG. 8, the case where the center of amplitude (Vout / N, referred to as a reference voltage) in the sine wave before full-wave rectification synchronized with the AC voltage vac is located below the maximum value of the AC voltage vac. Indicated. Then, in this case, the control for preventing the DC voltage Vdc from falling below the AC voltage vac by adjusting the amplitude of the voltage pulsation is shown. However, the adjustment of the amplitude of the voltage pulsation may be unnecessary in the case described below, for example.

For example, when the center of amplitude (reference voltage Vout / N) in the sinusoidal wave before full-wave rectification synchronized with the AC voltage vac is located above the maximum value of the AC voltage vac (not shown), it is superimposed. If the voltage pulsation is adjusted to be synchronized with the AC voltage vac, the DC voltage Vdc does not fall below the AC voltage vac even if the voltage pulsation is superimposed on the DC voltage Vdc. Therefore, it may be determined whether or not the amplitude of the voltage pulsation needs to be adjusted according to the value of the center of amplitude (reference voltage Vout / N) in the sine wave before full-wave rectification.

Further, the AC / DC converter 10 may be a conversion circuit having a power factor improving PFC (Power Factor Rectification) function, and may be configured by a one-stone PFC circuit, a totem pole system, or an interleave system. The DC / DC converter 20 may be a converter having a transformer, and may be configured by a flyback converter, a half-bridge system, or a center tap system.

Hereinafter, the power conversion device 100a having a configuration different from that of the power conversion device 100 shown in FIG. 1 will be described.
FIG. 10 is a block diagram showing a schematic configuration of the power conversion device 100a according to the first embodiment.
As shown in FIG. 10, the reactor 2 for limiting current may be divided into a positive generatrix and a negative generatrix connected to the AC power supply 1 and arranged. By arranging the positive and negative generatrix separately, the positive and negative current paths are not biased, so that the generation of common mode noise in the circuit can be suppressed.

The power conversion device of the present embodiment configured as described above is
An AC / DC converter that converts AC power from an AC circuit into DC power and controls the power factor improvement of the AC power, and a DC / DC that is connected to the DC side of the AC / DC converter and performs voltage conversion of DC power. A DC converter, a DC capacitor connected between the positive and negative DC bus lines between the AC / DC converter and the DC / DC converter, a control unit that controls the AC / DC converter and the DC / DC converter, and the like. With
The control unit controls the DC voltage of the DC capacitor to a DC voltage on which a voltage pulsation having a waveform having a waveform that becomes a minimum value at the zero cross phase and a maximum value at the peak phase of the AC voltage from the AC circuit is superimposed. A command value is generated, and at least one of the AC / DC converter and the DC / DC converter is controlled by using the ripple voltage command value.
It is a thing.

As described above, the control circuit controls the DC voltage of the DC capacitor to the DC voltage on which the voltage pulsation having the waveform having the minimum value at the zero cross phase of the AC voltage and the maximum value at the peak phase is superimposed. In this way, the load current is pulsated by the voltage pulsation of the DC capacitor that matches the waveform of the AC voltage, and the output power is pulsated according to the AC voltage. As a result, the energy secured by the DC capacitor can be significantly reduced, so that the capacity of the DC capacitor can be reduced and a small power conversion device can be realized.
The power conversion device of the present embodiment obtains a high effect when the AC power supply has a single phase, but the same effect can be obtained with a multi-phase AC power supply.

Further, the power conversion device of the present embodiment configured as described above is
The control unit adjusts the ripple voltage command value so that the maximum value of the voltage pulsation is equal to or less than the set first value, and the second value in which the minimum value of the voltage pulsation is set. At least one of the minimum value limit control for adjusting the ripple voltage command value so as to be as described above is performed.
It is a thing.

In this way, by limiting the maximum and minimum values of the voltage pulsation superimposed on the DC voltage of the DC capacitor, it is possible to prevent the DC voltage from pulsating beyond the withstand voltage of the semiconductor element. In this way, the voltage value applied to each element constituting the power conversion device can be limited to suppress the increase in size of the device due to the increase in withstand voltage, and at the same time, the loss of the circuit can be reduced. In this way, a smaller and more efficient power conversion device can be realized.

Further, the power conversion device of the present embodiment configured as described above is
The AC / DC converter is a step-up AC / DC converter that rectifies and boosts the input AC voltage.
The control unit adjusts the ripple voltage command value so that the maximum value of the voltage pulsation is equal to or higher than the maximum value of the AC voltage.
It is a thing.

In this way, the superimposed voltage pulsation is adjusted so that the maximum value of the voltage pulsation of the DC capacitor is equal to or greater than the maximum value of the AC voltage. Therefore, when a step-up AC / DC converter is used, the AC cycle The boosting operation can be compensated for the entire cycle. In this way, the power factor control can be stabilized, and a more efficient and highly reliable power conversion device can be realized.

Further, the power conversion device of the present embodiment configured as described above is
The voltage pulsation has a waveform obtained by full-wave rectifying a sine wave synchronized with the AC voltage.
It is a thing.

In this way, by making the superimposed voltage pulsation a waveform obtained by full-wave rectifying the limiting wave synchronized with the AC voltage, it is possible to reliably generate a voltage pulsation component that matches the waveform of the AC voltage.

Further, the power conversion device of the present embodiment configured as described above is
In a configuration in which the reference voltage at the center of the amplitude of the sine wave is equal to or less than the maximum value of the AC voltage.
The control unit
The ripple voltage command value is adjusted so that the amplitude of the voltage pulsation is equal to or greater than the difference between the maximum value of the AC voltage and the reference voltage.
It is a thing.

In this way, even when the reference voltage, which is the center of the amplitude of the sine wave synchronized with the AC voltage before full-wave rectification, is equal to or less than the maximum value of the AC voltage, the amplitude of the superimposed voltage pulsation is changed to the AC voltage. Control so that it is greater than or equal to the difference between the maximum value of and the reference voltage. As a result, the boosting operation can be compensated by surely setting the DC voltage to the maximum value or more of the AC voltage over the entire AC cycle.
In this way, the power factor control can be stabilized, and a more efficient and highly reliable power conversion device can be realized.

Further, the power conversion device of the present embodiment configured as described above is
The first value and the second value are determined based on at least one of the computing power of the control unit, the response speed of the control unit, and the withstand voltage of the semiconductor element constituting the power conversion device.
It is a thing.

This can reliably prevent the DC voltage from pulsating beyond the withstand voltage of the semiconductor element. In addition, stable control according to the performance of the control circuit 30 used becomes possible. In this way, a more reliable power conversion device can be realized.

Further, the power conversion device of the present embodiment configured as described above is
In a configuration in which the output voltage of the DC / DC converter is constant and the AC current from the AC circuit follows the set first current command value.
The control unit
The alternating current is controlled by controlling the AC / DC converter based on the first current command value.
By controlling the DC / DC converter based on the ripple voltage command value, the DC voltage of the DC capacitor is controlled to the DC voltage on which the voltage pulsation is superimposed.
It is a thing.

In this way, the control circuit can be applied even when the input current from the AC circuit is made to follow the command value.

Further, the power conversion device of the present embodiment configured as described above is
The DC / DC converter
An isolated DC / DC converter equipped with an isolation transformer having a primary coil and a secondary coil.
The control unit calculates the minimum value of the voltage pulsation based on the turns ratio of the isolation transformer.
It is a thing.

In this way, the second value that limits the lower limit of the voltage pulsation can be derived based on the circuit constants in the DC / DC converter. For example, the load voltage is divided by the turns ratio N and the correction coefficient K2 is multiplied. It is also possible to set with the specified value. As a result, the lower limit of the voltage pulsation based on the load voltage can be set, so that the power factor control can be stabilized, and a more efficient and highly reliable power conversion device can be realized.

Embodiment 2.
Hereinafter, the second embodiment of the present application will be described with reference to the parts different from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
The main circuit configuration of the power conversion device according to the second embodiment is the same as that of the first embodiment, and the configuration of the control circuit 230 is different.
FIG. 11 is a control block diagram of the control circuit 230 of the power conversion device according to the second embodiment.

The control circuit 230 includes a voltage ripple command generator 40, a power factor command calculator 260, an intermediate voltage command calculator 280, an output current command calculator 290, and gate signal generators 31 and 32.
Since the voltage ripple command generator 40 and the gate signal generators 31 and 32 have the same configuration as that of the first embodiment and have the same operation, the description thereof will be omitted.
The ripple voltage command value Vdc_ripple generated by the voltage ripple command generator 40 is input to the power factor command calculator 260, the intermediate voltage command calculator 280, and the output current command calculator 290.

The intermediate voltage command calculator 280 generates the voltage command value Vdc_ref of the DC capacitor 3 by using the input ripple voltage command value Vdc_ripple and the DC voltage Vdc detected by the sensor. The generated voltage command Vdc_ref is input to the power factor command calculator 260.

The power factor command calculator 260 uses the input ripple voltage command value Vdc_ripple, the voltage command Vdc_ref, and the AC current iac, AC voltage vac, DC voltage Vdc, and load voltage Vout detected by the sensor. While controlling the power factor of the current iac to a high power factor, a duty ratio signal Duty_PFC that causes the DC voltage Vdc to follow the command value is generated.

The output current command calculator 290 uses the input ripple voltage command value Vdc_ripple, the AC voltage vac, the load voltage Vout, and the load current iout detected by the sensor, and the duty ratio signal Duty_iout that controls the load current iout. To generate.

In the second embodiment, it is assumed that a constant voltage source such as a battery is connected to the load 5, and the control circuit 230 shown in FIG. 11 has a fixed output voltage (load voltage Vout). , This is a configuration in which the load current iout is controlled to an arbitrary value.

Hereinafter, the details of the control operation performed by the control circuit 230 configured as described above will be described. In the detailed description of this control operation, the detailed configurations of the power factor command calculator 260, the intermediate voltage command calculator 280, and the output current command calculator 290 that constitute the control circuit 230 will also be described.

First, the configuration of the intermediate voltage command calculator 280 will be described with reference to FIG.
FIG. 12 is a control block diagram of the intermediate voltage command calculator 280 according to the second embodiment.
The intermediate voltage command calculator 280 calculates the deviation 281 between the DC voltage Vdc detected by the sensor and the ripple voltage command value Vdc_ripple. Then, the intermediate voltage command calculator 280 PI-controls this deviation 281 to calculate the voltage command value Vdc_ref.

Next, the generation of the duty ratio signal Duty_PFC by the power factor command calculator 260 will be described with reference to FIG.
FIG. 13 is a control block diagram of the power factor command calculator 260 according to the second embodiment.
The power factor command calculator 260 performs PI control so that the power factor of the alternating current iac becomes 1 while making the DC voltage Vdc of the DC capacitor 3 follow the command value.
In the power factor control of the alternating current iac, the power factor command calculator 260 derives the instantaneous power Pout (t) of the output power Pout with the power factor set to 1, which is represented by the following equation (3).

Instantaneous power Pout (t) = Instantaneous voltage vout (t) * Instantaneous current iout (t)
= √2Vsin (ωt) * √2Isin (ωt)
= 2VIsin ^ 2 (ωt)
= VI (1-cos (2ωt))
= VI (1-sin (2ωt + π / 2)) ... (3)

As shown in FIG. 13, the power factor command calculator 260 generates a signal 261 by multiplying the load current command value iout * as the second current command value and the load voltage Vout detected by the sensor. After that, by adding the voltage command value Vdc_ref generated by the intermediate voltage command calculator 280, the power command 262 on which the desired voltage pulsation is superimposed is calculated.
Next, the instantaneous power command value 265 is calculated by multiplying the power command 262 by a waveform signal 264 including a delay of 90 degrees in a double cycle of the AC voltage vac generated by the PLL calculator 263. Then, the instantaneous power 266 based on the AC voltage vac detected by the sensor and the AC current iac is calculated, and the deviation 267 between the instantaneous power command value 265 and the sensed instantaneous power value 266 is controlled by PI to generate the voltage command value 268. To do.
In the above, the signal 261 is generated by multiplying the load current command value iout * and the load voltage Vout detected by the sensor, but the load current iout detected by the sensor may be used instead of the load current command value iout *. Good. When the control is performed using the load current command value iout *, a command value that is not affected by components such as noise can be generated, so that control with a higher power factor becomes possible.

Then, this voltage command value 268 is standardized by dividing it by the ripple voltage command value Vdc_ripple, and by adding the signal of the FF control calculator 269, a duty ratio signal Duty_PFC capable of responding to a steep fluctuation of the sensor value is generated. To do.
The calculation of the FF control calculator 269 is the same as that of the equation (2) shown in the first embodiment.

Next, the output current command calculator 290 will be described with reference to FIG.
FIG. 14 is a control block diagram of the output current command calculator 290 according to the second embodiment.
As described above, the output current command calculator 290 calculates the duty ratio signal Duty_iout such that the load current iout follows the command value.
As shown in FIG. 14, the output current command calculator 290 delays the load current command value iout * as the second current command value by 90 degrees with respect to the double cycle of the AC voltage vac generated by the PLL calculator 291. A signal 293 is generated by multiplying the included waveform signal 292. By doing so, the current pulsation synchronized with the AC voltage vac, which is twice the cycle of the AC voltage vac generated in the DC voltage Vdc of the DC capacitor 3, is output to the load 5.

After that, the difference 294 between the signal 293 and the load current iout detected by the waveform sensor is PI-controlled to generate a signal 295 that controls the current flowing through the reactor 24 for current control. After that, the signal 296 obtained by adding the load voltage Vout to the signal 295 is standardized by dividing by the signal 297 obtained by multiplying the ripple voltage command value Vdc_ripple by the winding ratio N to generate the duty ratio signal Duty_iout.

In the gate signal generator 31 shown in FIG. 11, the duty ratio signal Duty_PFC and the carrier wave generated in this way are PWM-controlled to generate gate signals G10c and G10d to the semiconductor switching elements 10c and 10d, and AC. The AC current iac is controlled to a high power factor by the / DC converter 10.
The gate signal generator 32 generates gate signals G21a, G21b, G21c, and G21d to the semiconductor switching elements 21a, 21b, 21c, and 21d by PWM-controlling the duty ratio signal Duty_Vdc and the carrier wave generated in this way. Then, the DC / DC converter 20 controls the DC voltage Vdc to a DC voltage on which a desired voltage pulsation is superimposed.

Hereinafter, the effect of the power conversion device of the present embodiment will be described in comparison with the power conversion device of the comparative example.
FIG. 15 is a diagram showing a simulation waveform using the power conversion device 100 of the present embodiment.
FIG. 16 is a diagram showing a simulation waveform using the power conversion device of Comparative Example 1.
FIG. 17 is a diagram showing a simulation waveform using the power conversion device of Comparative Example 2.

Both the power conversion devices of Comparative Examples 1 and 2 have a circuit configuration in which an AC / DC converter and a DC / DC converter that perform power conversion with an AC power supply power factor improvement control are connected via a DC capacitor. Have.
Further, it is assumed that the power conversion device of Comparative Example 1 does not control the voltage of the DC capacitor 3 as in the control circuit 30 of the present embodiment.
Further, it is assumed that the power conversion device of Comparative Example 2 controls to superimpose an AC current command having a minimum value in the zero cross phase of the AC voltage and a maximum value in the peak phase on the DC current command.

Further, in the power conversion device of Comparative Example 1, the capacity of a DC capacitor capable of obtaining a power factor similar to that of the power conversion device 100 of the present embodiment is used.
As an operating condition, it is assumed that the input power is several kW and a constant voltage source is connected to the load.
In each figure, in order from the top, a diagram showing the AC voltage vac, the DC voltage Vdc of the DC capacitor 3, and the load voltage Vout, a diagram showing the AC current iac, and a diagram showing the load current iout are shown side by side.

The capacity of the DC capacitor 3 used in the power conversion device of the present embodiment of FIG. 15 is 10 μF, and the capacity of the DC capacitor 3 used in the power conversion device of Comparative Example 1 of FIG. 16 is 1 mF. Further, the capacity of the DC capacitor 3 used in the power conversion device of Comparative Example 2 of FIG. 17 is 10 μF, which is the same capacity as that of the power conversion device of the present embodiment.

From FIGS. 15 and 16, even if the capacity is reduced to 1/100 by using the power conversion device of the present embodiment, the boosting operation can always be realized, and the AC current iac operates in a state close to the power factor 1. I know I can do it.
Here, it is assumed that the capacity of the DC capacitor of the power conversion device of Comparative Example 1 is reduced in the operating state shown in FIG. In this case, the amplitude of the ripple voltage of the double frequency component of the AC power supply 1 generated in the voltage of the DC capacitor increases, and when the lower limit of the ripple voltage becomes equal to or lower than the AC voltage, a state of step-down operation occurs. In the circuit system in which the AC / DC converter cannot step down, the power factor control of the AC current iac becomes unstable and the control fails.

Further, from the waveform shown in FIG. 17, it can be seen that if the capacitor capacity of the power converter of Comparative Example 2 is lowered more than necessary, the power factor deteriorates in order to maintain the boosting operation in the AC / DC converter. ..

Further, since the load 5 serves as a constant voltage source, both the power conversion device of the present embodiment and the power conversion devices of Comparative Examples 1 and 2 have twice the frequency of the AC power supply 1 superimposed on the voltage of the DC capacitor 3. A current with superimposed components flows. Since the power conversion device of the present embodiment and the power conversion device of Comparative Example 2 are controlled so that the pulsation of the current flowing through the load 5 is a sine wave, it is compared with Comparative Example 1 in which the current control is not performed. The pulsation of the electric current becomes large.
However, as described above, the amplitude of the voltage ripple superimposed in the power conversion device of the present embodiment can be within an allowable range by adjusting the amplitude so as to be within a desired range.

The waveform signal shown in the power factor command calculator 260 and the output current command calculator 290, which includes a delay of 90 degrees in the double cycle of the AC voltage vac, is ± 3rd value degree with respect to 90 degrees. Margin may be included.
This third value may be set within a phase range in which the DC voltage Vdc of the DC capacitor 3 on which the voltage pulsation is superimposed is secured to be equal to or higher than the AC voltage Vac from the AC power supply 1.

The power conversion device of the present embodiment configured as described above is
In the control in which the output voltage of the DC / DC converter is constant and the output current of the DC / DC converter follows the set second current command value.
The control unit
The output current is controlled by controlling the DC / DC converter based on the second current command value.
By controlling the AC / DC converter based on the ripple voltage command value, the DC voltage of the DC capacitor is controlled to the DC voltage on which the voltage pulsation is superimposed.
It is a thing.

As a result, the same effect as that of the first embodiment can be obtained, and the energy secured by the DC capacitor can be significantly reduced. Therefore, the capacity of the DC capacitor can be reduced, a small power conversion device can be realized, and the control circuit can be DC. It can also be applied when the output current from the / DC converter is made to follow the command value.

Further, the power conversion device of the present embodiment configured as described above is
The control unit
Using the second current command value or the detected output current of the DC / DC converter and the detected output voltage of the DC / DC converter, the instantaneous power value of the output power of the DC / DC converter is determined. Derived and
Based on the instantaneous power value, the power factor improvement control of the AC / DC converter is performed.
It is a thing.

In this way, by performing the power factor improvement control based on the instantaneous power value of the output power of the DC / DC converter, the power factor control with a higher power factor that is not affected by the voltage pulsation superimposed on the DC capacitor. Is possible.

Further, the power conversion device of the present embodiment configured as described above is
The control unit
A waveform that is 90 ± third value degree out of phase with the phase of the AC voltage is superimposed on the second current command value at a period twice that of the AC voltage.
The third value is set to a value at which the DC voltage of the DC capacitor on which the voltage pulsation is superimposed is equal to or higher than the AC voltage from the AC circuit.
It is a thing.

In this way, the output current of the DC / DC converter is superposed with the pulsation synchronized with the AC voltage, which has a period twice the AC voltage. By controlling the pulsation to be superimposed on the output current and controlling the DC voltage of the DC capacitor by the power factor command calculator using the ripple voltage command value, the power factor control with a higher power factor can be achieved. Further reduction of the energy secured by the DC capacitor can be realized.

In the second embodiment as well, as in the first embodiment, the current limiting reactor 2 may be divided into a positive generatrix and a negative generatrix of the AC power supply 1 and arranged. As a result, the positive and negative current paths are not biased, so that the generation of common mode noise in the circuit can be suppressed.

Embodiment 3.
Hereinafter, the third embodiment of the present application will be described with reference to the parts different from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 18 is a block diagram showing a schematic configuration of the power conversion device 300 according to the first embodiment.
In the power conversion device 300 of the third embodiment, the configuration of the DC / DC converter 320 is different from the configuration of the DC / DC converter 20 shown in the first embodiment.

In this case, the DC / DC converter 320 is composed of a step-down chopper, and includes semiconductor switching elements 21a and 21b and a reactor 24 for current control.
In the third embodiment, it is assumed that a constant voltage source such as a battery is connected to the load 5 as in the first embodiment. In the configuration of the control circuit 30, the output voltage is a fixed value. It is assumed that the input AC current is controlled to an arbitrary value. In this case, the configuration of the control circuit of the present embodiment is the same as that of the control circuit of the first embodiment.

Next, the operation of the power conversion device 300 according to the third embodiment will be described.
Since the operation of the power conversion device 300 is the same as the operation of the power conversion device 100 according to the first embodiment, the description thereof will be omitted. Further, since the operation of the AC / DC converter 10 is the same as that of the first embodiment, the description thereof will be omitted.
The operation of the DC / DC converter 320 is different from that of the isolated DC / DC converter 20 of the first and second embodiments. Based on the gate signal 321 from the control circuit 30, the DC / DC converter 320 converts the DC voltage of the DC capacitor 3 into a rectangular wave by the switching operation of the semiconductor switching element 21a and the semiconductor switching element 21b, and together with the reactor 24 for current control. By smoothing to a DC voltage with the smoothing capacitor 4, a stepped-down voltage is generated.

Further, since the control circuit 30 has a configuration in which the DC / DC converter 320 does not have an isolation transformer, the turns ratio N used in the generation of the duty ratio signal Duty_PFC and the duty ratio signal Duty_Vdc shown in the first embodiment. Is calculated as 1. Since the operation of the other control circuits 30 is the same as that of the first embodiment, the description thereof will be omitted.

Even in the power conversion device 300 having such a configuration, the same effect as that of the first embodiment can be obtained, the energy secured by the DC capacitor can be significantly reduced, the capacity of the DC capacitor can be reduced, and a small power conversion device can be realized. it can.

Assuming that a constant voltage source such as a battery is connected to the load 5 as in the second embodiment, when the output voltage is fixed and the output DC current is controlled to an arbitrary value, a control circuit is used. The configuration of 30 may be changed to the control circuit 230 of the second embodiment and operated. In this case, the operation of the control circuit is the same as that of the second embodiment except that the winding ratio N used in the generation of the duty ratio signal Duty_iout is set to 1.
Further, the DC / DC converter 20 may have any configuration as long as it is a non-insulated DC / DC converter, and may be configured by a step-up chopper and a buck-boost chopper.

Further, the lower limit of the voltage pulsation may be derived based on the duty ratio of the DC / DC converter 320. As a result, the lower limit value of the voltage pulsation based on the load voltage can be set, so that the power factor control can be stabilized.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not illustrated are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1 AC power supply (AC circuit), 3 DC capacitor, 10 AC / DC converter, 20,320 DC / DC converter, 23 high frequency isolation transformer (isolation transformer), 23a primary side coil, 23b secondary side coil, 30,230 control Circuit (control unit), 100, 300 power converter.

Claims (12)

1. An AC / DC converter that converts AC power from an AC circuit into DC power and controls the power factor improvement of the AC power, and a DC / DC that is connected to the DC side of the AC / DC converter and performs voltage conversion of DC power. A DC converter, a DC capacitor connected between the positive and negative DC bus lines between the AC / DC converter and the DC / DC converter, a control unit that controls the AC / DC converter and the DC / DC converter, and the like. With
   The control unit controls the DC voltage of the DC capacitor to a DC voltage on which a voltage pulsation having a waveform having a waveform that becomes a minimum value at the zero cross phase and a maximum value at the peak phase of the AC voltage from the AC circuit is superimposed. A command value is generated, and at least one of the AC / DC converter and the DC / DC converter is controlled by using the ripple voltage command value.
   Power converter.
2. The control unit adjusts the ripple voltage command value so that the maximum value of the voltage pulsation is equal to or less than the set first value, and the second value in which the minimum value of the voltage pulsation is set. At least one of the minimum value limit control for adjusting the ripple voltage command value so as to be as described above is performed.
   The power conversion device according to claim 1.
3. The AC / DC converter is a step-up AC / DC converter that rectifies and boosts the input AC voltage.
   The control unit adjusts the ripple voltage command value so that the maximum value of the voltage pulsation is equal to or higher than the maximum value of the AC voltage.
   The power conversion device according to claim 1 or 2.
4. The voltage pulsation has a waveform obtained by full-wave rectifying a sine wave synchronized with the AC voltage.
   The power conversion device according to any one of claims 1 to 3.
5. In a configuration in which the reference voltage at the center of the amplitude of the sine wave is equal to or less than the maximum value of the AC voltage.
   The control unit
   The ripple voltage command value is adjusted so that the amplitude of the voltage pulsation is equal to or greater than the difference between the maximum value of the AC voltage and the reference voltage.
   The power conversion device according to claim 4.
6. The first value and the second value are determined based on at least one of the computing power of the control unit, the response speed of the control unit, and the withstand voltage of the semiconductor element constituting the power conversion device.
   The power conversion device according to claim 2.
7. In a configuration in which the output voltage of the DC / DC converter is constant and the AC current from the AC circuit follows the set first current command value.
   The control unit
   The alternating current is controlled by controlling the AC / DC converter based on the first current command value.
   By controlling the DC / DC converter based on the ripple voltage command value, the DC voltage of the DC capacitor is controlled to the DC voltage on which the voltage pulsation is superimposed.
   The power conversion device according to any one of claims 1 to 6.
8. In the control in which the output voltage of the DC / DC converter is constant and the output current of the DC / DC converter follows the set second current command value.
   The control unit
   The output current is controlled by controlling the DC / DC converter based on the second current command value.
   By controlling the AC / DC converter based on the ripple voltage command value, the DC voltage of the DC capacitor is controlled to the DC voltage on which the voltage pulsation is superimposed.
   The power conversion device according to any one of claims 1 to 6.
9. The control unit
   Using the second current command value or the detected output current of the DC / DC converter and the detected output voltage of the DC / DC converter, the instantaneous power value of the output power of the DC / DC converter is determined. Derived and
   Based on the instantaneous power value, the power factor improvement control of the AC / DC converter is performed.
   The power conversion device according to claim 8.
10. The control unit
    A waveform that is 90 ± third value degree out of phase with the phase of the AC voltage is superimposed on the second current command value at a period twice that of the AC voltage.
    The third value is set to a value at which the DC voltage of the DC capacitor on which the voltage pulsation is superimposed is equal to or higher than the AC voltage from the AC circuit.
    The power conversion device according to claim 8 or 9.
11. The DC / DC converter
    An isolated DC / DC converter equipped with an isolation transformer having a primary coil and a secondary coil.
    The control unit derives the minimum value of the voltage pulsation based on the turns ratio of the isolation transformer.
    The power conversion device according to any one of claims 1 to 10.
12. The control unit
    The minimum value of the voltage pulsation is derived based on the duty ratio of the DC / DC converter.
    The power conversion device according to any one of claims 1 to 10.

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