JP2016032307A - Power converter and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for PFC control by current continuous mode, without monitoring the output current over the entire switching period.SOLUTION: A power converter 10 includes a rectifying and smoothing circuit 11 for outputting a DC voltage, obtained by rectifying and smoothing an AC voltage outputted from an AC power supply PS, between node N1 and node N2, an inductor L11 having one end connected with the node N1, a switching element Q11 for electrically connecting or insulating between the other end of the inductor L11 and the node N2, a diode D15 having an anode connected with the other end of the inductor L11, and a control unit 12 for searching a peak time position in the switching period where the maximum value of the absolute value of an output current I3 is monitored, for a monitor period that is a partial period of a first switching period, and monitoring the output current I3 during the monitor period, around a peak time position in the switching period, in the second switching period.SELECTED DRAWING: Figure 4

Description

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

  Conventionally, bidirectional inverters are known as one of power conversion circuits (Patent Documents 1 and 2). A bidirectional inverter converts AC power input from an AC power source such as a commercial power source into DC power and outputs it to an external load (converter operation). Conversely, it converts DC power input from a battery or the like into AC power. Output (inverter operation).

  In order to clear the harmonic current regulation, it is necessary to perform PFC (Power Factor Correction) control when converting AC power to DC power even in a bidirectional inverter. In recent years, PFC control is increasingly performed by digital control using a DSP (Digital Signal Processor) or the like instead of analog control. In this case, the current (output current) flowing through the switching element is monitored at predetermined time intervals, and the switching element is controlled using a control signal generated based on the monitored current value.

JP 2009-33800 A JP2013-90413A

  The bidirectional inverter disclosed in Patent Document 2 includes an LC filter 1 having inductors L1 and L2 and a smoothing capacitor C1, and a bridge circuit 2 having switching elements Q1 to Q4.

  From the viewpoint of the inverter operation, it is preferable that the inductances of the inductors L1 and L2 (that is, the output inductance when viewed as an inverter) are large. This is because the smoothing capacitor C1 can be downsized when the inductances of the inductors L1 and L2 are larger.

  However, if the inductances of the inductors L1 and L2 are increased, the output current is less likely to decrease when the converter operation is performed. As a result, PFC control is performed in the continuous current mode, and the output current must be monitored over the entire switching period.

  In that case, there is a problem that the A / D converter included in the DSP that performs PFC control cannot be used for other processing (for example, monitoring of the output voltage of the bidirectional inverter, monitoring of the charging voltage of the battery, etc.). . There is also a problem that a DSP dedicated to PFC control is required. These problems lead to an increase in size and cost of the bidirectional inverter.

  The present invention has been made based on the above technical recognition, and an object thereof is a power conversion device capable of performing PFC control in a continuous current mode without monitoring an output current over the entire switching period. And a control method thereof.

A power conversion device according to one embodiment of the present invention includes:
A rectifying and smoothing circuit for outputting a DC voltage obtained by rectifying and smoothing an AC voltage between the first node and the second node;
An inductor having one end connected to the first node to which the DC voltage is supplied;
A switching element for electrically connecting or insulating between the other end of the inductor and the second node;
A diode having an anode connected to the other end of the inductor;
A smoothing capacitor having one end connected to the cathode of the diode and the other end connected to the second node;
A control unit that controls the switching element to be turned on at a constant switching period and controls the switching element to be turned off within the switching period, and monitors an output current flowing through the switching element;
With
The control unit searches for a peak time position in the switching period in which the maximum value of the absolute value of the output current is monitored for a monitoring period that is a part of the first switching period among consecutive switching periods. In the second switching period following the first switching period, the output current is monitored during the monitoring period centering on the peak time position in the switching period.

In the power converter,
The peak time position in the switching period is a position of a time slot in which the maximum value is monitored among first to n-th time slots obtained by dividing the switching period into n equal parts (n: a positive integer). May be.

A power conversion device according to one embodiment of the present invention includes:
A power converter that converts AC power output from an AC power source into DC power, and converts DC power output from the DC power source into AC power,
A first input / output terminal; and a second input / output terminal for connecting the AC power supply between the first input / output terminal;
A fourth input / output terminal for connecting an external load between the third input / output terminal and the third input / output terminal;
A first smoothing capacitor having one end connected to the first input / output terminal and the other end connected to the second input / output terminal, and a first smoothing capacitor having one end connected to one end of the first smoothing capacitor An LC filter having an inductor and a second inductor having one end connected to the other end of the first smoothing capacitor;
A second smoothing capacitor having one end connected to the third input / output terminal and the other end connected to the fourth input / output terminal;
A first switching element having one end connected to the third input / output terminal and the other end connected to the other end of the second inductor, and a first switching element from the other end of the first switching element; A first rectifying element that allows current to flow only in the direction of one end of the
A second switching element having one end connected to the other end of the second inductor and the other end electrically connected to the fourth input / output terminal; and a second switching element from the other end of the second switching element to the second A second rectifying element that allows current to flow only in the direction of one end of the switching element;
A third switching element having one end connected to the third input / output terminal and the other end connected to the other end of the first inductor; and a third switching element from the other end of the third switching element. A third rectifying element that allows current to flow only in the direction of one end of the
A fourth switching element having one end connected to the other end of the first inductor and electrically connected to the other end of the fourth input / output terminal; A fourth rectifying element that allows current to flow only in the direction of one end of the switching element;
On / off control of the first to fourth switching elements and at least one of a first output current flowing through the second switching element and a second output current flowing through the fourth switching element A control unit for performing a current monitoring operation for monitoring
With
The controller is
When performing the converter operation of converting the AC power output from the AC power source connected between the first and second input terminals into DC power and outputting the DC power from the third and fourth input / output terminals, the second And the fourth switching element is controlled to be turned on at a constant switching cycle, and then controlled from on to off within the switching cycle, and in a part of the first switching cycle among the continuous switching cycles. For a certain monitoring period, a peak time position in the switching period in which the maximum absolute value of the first output current or the second output current is monitored is searched, and a second switching period following the first switching period is searched. Then, during the monitoring period with the peak time position in the switching period as a center, the current monitoring operation is performed.
It is characterized by that.

In the power converter,
The control unit monitors an AC voltage input from the AC power source in the converter operation, and the first output current or the second output current monitored in the second switching period is changed to the AC voltage. When the threshold current determined based on the threshold current is reached, the second and fourth switching elements may be controlled to be turned off.

In the power converter,
The external load is a DC-DC converter or a battery that steps down or boosts a DC voltage output from the third and fourth input / output terminals to a voltage suitable for a battery connected to the output of the external load. There may be.

In the power converter,
In the case of performing an inverter operation in which DC power output from a DC power source connected between the third and fourth input / output terminals is converted into AC power and output from the first and second input / output terminals, the control is performed. And the second switching element and the third switching element with respect to on / off of the first switching element and the fourth switching element so that the first to fourth switching elements perform a full bridge operation. These switching elements may be switched on / off in a complementary manner.

A control method for a power conversion device according to an aspect of the present invention includes:
A rectifying and smoothing circuit that outputs a DC voltage obtained by rectifying and smoothing an AC voltage between a first node and a second node, and an inductor having one end connected to the first node to which the DC voltage is supplied A switching element that electrically connects or insulates between the other end of the inductor and the second node, a diode having an anode connected to the other end of the inductor, and one end at the cathode of the diode A smoothing capacitor connected to the second node and connected to the other end of the second node, the switching element is controlled to be turned on at a constant switching period, and the switching element is controlled to be turned off within the switching period. A control method of a power converter comprising a control unit that monitors the output current flowing through
The controller is
For a monitoring period that is a part of the first switching period among consecutive switching periods, search for a peak time position in the switching period in which the maximum value of the absolute value of the output current is monitored,
In the second switching period following the first switching period, the output current is monitored during the monitoring period centering on the peak time position in the switching period.
It is characterized by that.

A control method for a power conversion device according to an aspect of the present invention includes:
A power conversion device that converts AC power output from an AC power source into DC power and converts DC power output from the DC power source into AC power, comprising: a first input / output terminal; and the first input / output terminal; And a fourth input / output terminal for connecting an external load between the third input / output terminal and the third input / output terminal. A first smoothing capacitor having one end connected to the first input / output terminal and the other end connected to the second input / output terminal, and one end connected to one end of the first smoothing capacitor. An LC filter having one inductor and a second inductor having one end connected to the other end of the first smoothing capacitor, one end connected to the third input / output terminal, and the fourth input / output terminal. A second smoothing capacitor with the other end connected to And a first switching element having one end connected to the third input / output terminal and the other end connected to the other end of the second inductor, and a first switching element from the other end of the first switching element. A first rectifying element that allows current to flow only in the direction of one end of the switching element, one end connected to the other end of the second inductor, and the other end electrically connected to the fourth input / output terminal. One end is connected to the second switching element, the second rectifying element that allows current to flow only from the other end of the second switching element to the one end of the second switching element, and the third input / output terminal. , A third switching element having the other end connected to the other end of the first inductor, and a third switching element that allows current to flow only from the other end of the third switching element to one end of the third switching element. A rectifying element and the first input; A fourth switching element having one end connected to the other end of the capacitor and electrically connected to the fourth input / output terminal, and a fourth switching element from the other end of the fourth switching element. The fourth rectifying element that allows current to flow only in the direction of one end and the first to fourth switching elements are on / off controlled, and the first output current that flows through the second switching element and the fourth A control unit for performing a current monitoring operation for monitoring at least one of the second output currents flowing through the switching element,
When performing the converter operation in which AC power output from the AC power source connected between the first and second input terminals is converted into DC power and output from the third and fourth input / output terminals, the control unit Is
The second and fourth switching elements are controlled to be turned on at a constant switching period, and then controlled from on to off within the switching period,
The switching period peak time during which the maximum value of the absolute value of the first output current or the second output current is monitored for a monitoring period which is a part of the first switching period among consecutive switching periods. Search for a location
In the second switching period following the first switching period, the current monitoring operation is performed during the monitoring period around the peak time position in the switching period.
It is characterized by that.

  In the power conversion device according to one aspect of the present invention, the control unit has a maximum absolute value of the output current flowing through the switching element for a monitoring period that is a partial period in the first switching period among the continuous switching periods. The peak time position in the switching period in which the value is monitored is searched, and in the second switching period following the first switching period, the output current is calculated during the monitoring period with the peak time position in the searched switching period as the center. Monitor. Thus, according to the present invention, it is possible to perform PFC control in the continuous current mode without monitoring the output current over the entire switching period.

It is a figure showing a schematic structure of power converter 1 concerning a 1st embodiment of the present invention. It is a time waveform figure for demonstrating the control method which concerns on this invention. FIG. 3 is an enlarged time waveform diagram for switching periods P2 and P3 of FIG. 2. It is a figure which shows schematic structure of the power converter device 10 which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
The power conversion device 1 according to the first embodiment is a bidirectional inverter capable of performing a converter operation and an inverter operation.

  As shown in FIG. 1, the power conversion device 1 includes input / output terminals T1 to T4, a control unit 2, a noise filter 3, an LC filter 4, a bridge circuit 5, an AC voltage detection circuit 6, and a DC voltage. A detection circuit 7 and a smoothing capacitor C2 are provided.

  When power converter 1 is operated as a converter, AC power supply PS is connected between input / output terminals T1 and T2, and external load 30 is connected between input / output terminals T3 and T4. In this case, the power conversion device 1 converts the AC power output from the AC power source PS connected between the input terminals T1 and T2 into DC power, and outputs the DC power from the input / output terminals T3 and T4.

  On the other hand, when operating the power converter 1 as an inverter, an external load is connected between the input / output terminals T1 and T2, and a DC power source is connected between the input / output terminals T3 and T4. In this case, the power conversion device 1 converts DC power output from a DC power source connected between the input / output terminals T3 and T4 into AC power, and outputs the AC power from the input / output terminals T1 and T2.

  The converter operation is performed, for example, when the battery is charged with an AC power supply. The inverter operation is performed, for example, when an AC-driven electric device is operated by a charged battery.

  Next, each component of the power converter device 1 will be described in detail.

  The input / output terminals T1 and T2 are terminals for connecting an AC power source PS as shown in FIG. In other words, the input / output terminal T2 is connected to the AC power supply PS between the input / output terminal T1.

  The input / output terminals T3 and T4 are terminals for connecting an external load 30 as shown in FIG. In other words, the external load 30 is connected between the input / output terminal T4 and the input / output terminal T3.

  The external load 30 is not particularly limited. For example, the DC voltage output from the input / output terminals T3 and T4 is stepped down (or boosted) to a voltage suitable for the battery connected to the output of the external load 30. ) DC-DC converter. Alternatively, the external load 30 may be a battery.

  The AC voltage detection circuit 6 is a circuit for detecting an AC voltage between the input / output terminals T1 and T2. Specifically, the AC voltage detection circuit 6 is configured using a transformer as shown in FIG. The AC voltage detection circuit 6 detects the AC voltage of the AC power source PS connected to the input / output terminals T1 and T2 during the converter operation, and detects the AC voltage output from the input / output terminals T1 and T2 during the inverter operation.

  The DC voltage detection circuit 7 is a circuit for detecting a DC voltage between the input / output terminals T3 and T4. Specifically, the DC voltage detection circuit 7 is configured by a voltage dividing circuit composed of resistors connected in series. The DC voltage detection circuit 7 detects a DC voltage output from the input / output terminals T3 and T4 during the converter operation, and detects a DC voltage input from the input / output terminals T3 and T4 during the inverter operation.

  The noise filter 3 is a filter for suppressing noise, and is provided between the input / output terminals T 1 and T 2 and the LC filter 4. Specifically, as shown in FIG. 1, the noise filter 3 includes common mode inductors L3 and L4 and capacitors C3, C4, and C5.

  More specifically, the inductor L3 has one end connected to the input / output terminal T1 and the other end connected to one end of the smoothing capacitor C1. The inductor L4 has one end connected to the input / output terminal T2 and the other end connected to the other end of the smoothing capacitor C1. The capacitors C3 and C4 connected in series are provided between the input / output terminal T1 and the input / output terminal T2. The connection point between the capacitor C3 and the capacitor C4 is grounded. Capacitor C5 is connected in parallel to capacitors C3 and C4 connected in series.

  The noise filter 3 is not limited to the above configuration. Moreover, you may abbreviate | omit the noise filter 3 as needed.

  As shown in FIG. 1, the LC filter 4 includes a smoothing capacitor C1 and normal mode inductors L1 and L2.

  The smoothing capacitor C1 has one end connected to the input / output terminal T1 via the inductor L3 and the other end connected to the input / output terminal T2 via the inductor L4. When the noise filter 3 is not provided, one end of the smoothing capacitor C1 is directly connected to the input / output terminal T1, and the other end of the smoothing capacitor C1 is directly connected to the input / output terminal T2.

  The inductor L1 has one end connected to one end of the smoothing capacitor C1, and the inductor L2 has one end connected to the other end of the smoothing capacitor C1.

  As shown in FIG. 1, the bridge circuit 5 includes switching elements Q1, Q2, Q3, and Q4 and diodes D1, D2, D3, and D4.

  The switching element Q1 has one end connected to the input / output terminal T3 and the other end connected to the other end of the inductor L2 of the LC filter 4. The switching element Q2 has one end connected to the other end of the inductor L2 of the LC filter 4 and the other end electrically connected to the input / output terminal T4. The switching element Q3 has one end connected to the input / output terminal T3 and the other end connected to the other end of the inductor L1 of the LC filter 4. The switching element Q4 has one end connected to the other end of the inductor L1 of the LC filter 4 and the other end electrically connected to the input / output terminal T4.

  The switching elements Q1 to Q4 are IGBTs (Insulated Gate Bipolar Transistors) in FIG. 1, but are not limited thereto, and may be semiconductor switches such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and bipolar transistors.

  The diode D1 has a cathode connected to one end of the switching element Q1, and an anode connected to the other end of the switching element Q1. The diode D2 has a cathode connected to one end of the switching element Q2, and an anode connected to the other end of the switching element Q2. The diode D3 has a cathode connected to one end of the switching element Q3 and an anode connected to the other end of the switching element Q3. The diode D4 has a cathode connected to one end of the switching element Q4 and an anode connected to the other end of the switching element Q4.

  Note that when the switching elements Q1 to Q4 are MOSFETs, the diodes D1 to D4 may be parasitic diodes in the MOSFET. That is, the diodes D1 to D4 are diodes provided separately for the switching elements Q1 to Q4, and may be parasitic diodes in the switching elements Q1 to Q4.

  Therefore, more generally speaking, the diode D1 is a rectifying element that allows current to flow only in the direction from the other end of the switching element Q1 to one end of the switching element Q1, and the diode D2 is connected to the switching element Q2 from the other end of the switching element Q2. A rectifying element that allows current to flow only in the direction of one end, the diode D3 is a rectifying element that allows current to flow only in the direction of one end of the switching element Q3 from the other end of the switching element Q3, and a diode D4 from the other end of the switching element Q4 This is a rectifying element that allows current to flow only in the direction of one end of the switching element Q4.

  The control unit 2 outputs a control signal (gate voltage) of the switching elements Q1 to Q4 to the bridge circuit 5, and performs on / off control of the switching elements Q1 to Q4. More specifically, the control unit 2 is configured to PWM control the switching elements Q1 to Q4. Specifically, the control unit 2 controls on / off of the switching elements Q1 to Q4 by applying control signals to the gate terminals of the switching elements Q1 to Q4, respectively.

  The on / off control of the switching elements Q1 to Q4 by the control unit 2 differs between when the power conversion device 1 is operated as a converter and when the power conversion device 1 is operated as an inverter.

  When performing the converter operation, the control unit 2 controls the switching elements Q2 and Q4 to be turned on at a constant switching cycle, and then controls from on to off within the switching cycle. Details will be described later with reference to FIG.

  Preferably, when performing the converter operation, control unit 2 controls switching element Q2 and switching element Q4 on / off in synchronization, and fixes switching element Q1 and switching element Q3 to be off. As a result, AC / DC conversion can be performed by driving the switching elements Q2 and Q4 irrespective of the normal phase / reverse phase of the AC voltage VAC of the AC power supply PS. It is no longer necessary to detect the orientation of.

  Further, in the converter operation, in order to improve the power factor, the control unit 2 switches the switching elements Q2, Q4 so that the current flowing through the switching elements Q2, Q4 is similar to the waveform of the AC voltage VAC of the AC power supply PS. ON / OFF control.

  On the other hand, when the inverter operation is performed, the control unit 2 performs on / off control of the switching elements Q1 to Q4 so as to perform a full bridge operation. Specifically, control unit 2 controls switching element Q1 and switching element Q4 to be turned on / off in synchronization, and switching element Q2 and switching element Q3 are turned on / off by switching elements Q1 and Q4 being turned on / off. ON / OFF control so as to be complementary.

  Control unit 2 monitors output current I1 flowing through switching element Q2 and output current I2 flowing through switching element Q4. Specifically, as shown in FIG. 1, a resistor R1 is provided between the other end of the switching element Q2 and the input / output terminal T4, and the control unit 2 connects the resistor R1 and the switching element Q2. A point voltage is input, and the current value flowing through the switching element Q2 is grasped based on the voltage. Similarly, a resistor R2 is provided between the other end of the switching element Q4 and the input / output terminal T4, and the control unit 2 inputs a voltage at a connection point between the resistor R2 and the switching element Q4, and the voltage Based on the above, the value of the current flowing through the switching element Q4 is grasped.

  In general, since the inductance values of the inductor L3 and the inductor L4 are equal, the output current I1 and the output current I2 of the converter operation are opposite in direction and have the same absolute value (size). Therefore, the control unit 2 may monitor only one of the output current I1 and the output current I2.

  Next, the operation of the control unit 2 in the converter operation will be described in detail with reference to FIG. FIG. 2 shows a time waveform (for the positive phase) of the AC voltage VAC of the AC power supply PS and a time waveform of the output current I. Here, the output current I indicates the output current I1 and / or the output current I2.

  FIG. 2 shows continuous switching periods P1 to P7. The time interval between the switching periods P1 to P7 is constant, for example, 50 μsec (20 kHz), for example.

  Each switching period P1 to P7 is composed of a predetermined number of time slots. In the example of FIG. 2, one switching cycle is composed of 13 time slots. However, the number of time slots is not limited to this value, and is based on, for example, the specifications and performance of the DSP constituting the control unit 2. Can be decided.

  As shown in FIG. 2, the control unit 2 controls the switching elements Q2 and Q4 to be turned on at the start time of each switching period P1 to P7, and maintains the on state during the on widths Ton1 to Ton7 for each switching period. . That is, the control unit 2 controls the switching elements Q2 and Q4 to be turned on at a constant switching period, and thereafter controls from on to off within the switching period.

  The control unit 2 monitors the AC voltage VAC input from the AC power source PS via the AC voltage detection circuit 6. Then, when the output current I monitored in the switching period reaches the threshold current, the control unit 2 controls the switching elements Q2 and Q4 to be turned off.

  Here, the threshold current is a current determined based on the AC voltage VAC monitored in the switching period. In FIG. 2, threshold currents Ith1 to Ith7 indicate currents determined for each of the switching periods P1 to P7. The threshold current is determined based on, for example, the current (current time slot) AC voltage VAC.

  The control unit 2 monitors the output current I only during the monitoring periods M1 to M7 for each switching period P1 to P7. The monitor periods M1 to M7 are time intervals having a predetermined width (for example, 5 time slots).

  Monitor periods M1 to M7 indicate periods during which the control unit 2 monitors the output current I in the switching periods P1 to P7. Each of the monitor periods M1 to M7 is a partial period of the switching periods P1 to P7, and is a period of 5 time slots in the example of FIG.

  As shown in FIG. 2, the time positions of the monitoring periods M1 to M7 are different for each of the switching periods P1 to P7. For example, the monitoring period M1 is a period of first to fifth time slots, the monitoring period M2 is a period of third to seventh time slots, and the monitoring period M3 is a period of fourth to eighth time slots.

  Note that the width of the monitoring period is not limited to the width illustrated in FIG. 2, and is determined in consideration of the performance of the DSP constituting the control unit 2 and the load due to monitoring processing other than the output current I, for example. Monitor processing other than the output current I includes monitoring of the AC voltage VAC, monitoring of the DC voltage via the DC voltage detection circuit 7, monitoring of the charging voltage of the battery connected to the DC-DC converter as the external load 30, and the like. Can be mentioned.

  Next, how to determine the time position of the monitoring period will be described in detail. FIG. 3 is an enlarged time waveform diagram for the switching periods P2 and P3 of FIG. With reference to FIG. 3, how to determine the monitoring period M3 in the switching period P3 will be described.

  First, the control unit 2 searches for the peak time position in the switching period where the maximum value (peak value) of the absolute value of the output current I is monitored for the monitoring period M2. The peak time position in the switching period is the position of the time slot in which the maximum value is monitored among the first to nth time slots obtained by dividing the switching period into n equal parts (n: a positive integer).

  In the example of FIG. 3, as a result of the search, it can be seen that the peak time position in the switching period in the switching period P2 is the sixth time slot.

  Then, in the switching period P3 following the switching period P2, the control unit 2 has a predetermined width (in this example, 5 time slots) around the peak time position in the switching period of the switching period P2 (that is, the sixth time slot). Min) during the monitoring period. Specifically, the monitoring period M3 is the fourth to eighth time slots as shown in FIG.

  The monitoring period is similarly determined for the switching period P4 and thereafter. The control unit 2 monitors the output current I only for the monitoring period thus determined. Although the method for determining the monitoring period in the time domain of the positive phase of the AC voltage VAC has been described, the monitoring period can be similarly determined for the time domain of the negative phase of the AC voltage VAC.

  As described above, in the present embodiment, the control unit 2 searches for the peak time position in the switching period where the maximum value of the absolute value of the output current I is monitored for the monitoring period of the previous switching period, and the previous switching period. In the current switching cycle subsequent to the cycle, the output current I is monitored during a monitoring period having a predetermined width centered on the searched peak time position in the switching cycle.

  In this way, in the current switching cycle, the output current is monitored only during a monitoring period of a predetermined width, centered on the time position where the output current is maximized in the previous switching cycle. Since the AC voltage VAC has a sine waveform with a moderate fluctuation, it is assumed that the ON width of the switching element also changes gradually. For this reason, the timing at which the output current I reaches the threshold current can be efficiently captured by the above monitoring method.

  This eliminates the need for the control unit 2 to constantly monitor the output current I.

  Therefore, according to the first embodiment, it is possible to perform PFC control in the continuous current mode without monitoring the output current over the entire switching period.

  Accordingly, for example, the output current I can be monitored and other monitoring processes can be performed by one DSP, and there is no need to provide a DSP dedicated to PFC control. In addition, the degree of freedom in selecting the output inductance value of the bidirectional inverter, such as increasing the inductance of the inductors L1 and L2 of the LC filter, can be increased. As a result, a power converter such as a bidirectional inverter can be reduced in size and cost.

(Second Embodiment)
Next, the power converter device 10 according to the second embodiment will be described with reference to FIG. FIG. 4 shows a schematic configuration of the power conversion device 10 according to the second embodiment. The power conversion device 10 according to the second embodiment includes a power factor correction circuit (PFC circuit), and converts an AC voltage input from an AC power source into a DC voltage and outputs the DC voltage. In other words, the power conversion device 10 is a one-way operation power conversion device that performs only a converter operation without performing an inverter operation.

  As shown in FIG. 4, the power conversion device 10 includes input terminals T1, T2, output terminals T3, T4, a noise filter 3, a rectifying / smoothing circuit 11, a control unit 12, an input voltage detection circuit 13, An output voltage detection circuit 14 and a PFC circuit 15 are provided.

  Next, each component of the power converter 10 will be described in detail.

  The input terminals T1 and T2 are terminals for connecting an AC power source PS as shown in FIG. The output terminals T3 and T4 are terminals for connecting an external load 30 as shown in FIG. The external load 30 is a DC-DC converter, a battery, or the like, as in the first embodiment.

  The noise filter 3 is a filter for suppressing noise, and is provided between the input terminals T1 and T2 and the rectifying and smoothing circuit 11. Since the specific configuration of the noise filter 3 is the same as that of the first embodiment, detailed description thereof is omitted.

  The rectifying / smoothing circuit 11 rectifies and smoothes the AC voltage VAC output from the AC power source PS. As shown in FIG. 4, the rectifying and smoothing circuit 11 outputs a DC voltage obtained by rectifying and smoothing between the node N1 and the node N2. Here, the DC voltage output from the rectifying and smoothing circuit 11 is supplied to the node N1, and the node N2 is kept at the reference potential.

  Specifically, as shown in FIG. 4, the rectifying / smoothing circuit 11 includes a diode bridge composed of diodes D11, D12, D13, and D14, and a smoothing capacitor C11 for smoothing a pulsating voltage output from the diode bridge. And have.

  The input voltage detection circuit 13 is a circuit for detecting the input voltage of the PFC circuit 15, that is, the output voltage of the rectifying / smoothing circuit 11 (voltage between the node N1 and the node N2). The output voltage detection circuit 14 is a circuit for detecting the output voltage of the PFC circuit 15. Both the input voltage detection circuit 13 and the output voltage detection circuit 14 are configured by, for example, a voltage dividing circuit including resistors connected in series.

  The control unit 12 inputs a monitor value (monitor voltage) from the input voltage detection circuit 13, the output voltage detection circuit 14, and the PFC circuit 15, and outputs a switching control signal (gate voltage) to the PFC circuit 15.

  As shown in FIG. 4, the PFC circuit 15 includes an inductor L11, a switching element Q11, a diode D15, and a smoothing capacitor C12.

  One end of the inductor L11 is connected to a node N1 to which a DC voltage is supplied from the rectifying and smoothing circuit 11.

  Switching element Q11 electrically connects or insulates between the other end of inductor L11 and node N2. As shown in FIG. 4, the switching element Q11 is, for example, an N-type MOSFET. In this case, the drain terminal of the switching element Q11 is connected to the other end of the inductor L11, and the source terminal of the switching element Q11 is connected to the node N2 via the resistor R3.

  The switching element Q11 is not limited to a MOSFET, and may be a semiconductor switch such as an IGBT or a bipolar transistor.

  The diode D15 has an anode connected to the other end of the inductor L11 and a cathode connected to the output terminal T3.

  The smoothing capacitor C12 has one end connected to the cathode of the diode D15 and the other end connected to the node N2 and the output terminal T4.

  Next, the operation of the control unit 12 will be described in detail.

  The control unit 12 controls the switching element Q11 of the PFC circuit 15 to be turned on at a constant switching period, and thereafter controls the switching element Q11 to be turned off within the switching period.

  Further, in order to improve the power factor, the control unit 12 performs on / off control of the switching element Q11 so that the current flowing through the switching element Q11 is similar to the waveform of the AC voltage VAC of the AC power supply PS.

  Control unit 12 monitors output current I3 flowing through switching element Q11. Specifically, as illustrated in FIG. 4, a resistor R3 is provided between the switching element Q11 (source terminal thereof) and the output terminal T4, and the control unit 12 determines whether the resistor R3 and the switching element Q11 are connected. The voltage at the connection point is input, and the current value flowing through the switching element Q11 is grasped based on the voltage.

  As in the first embodiment, the control unit 12 monitors the maximum value of the absolute value of the output current I3 for a monitoring period of a predetermined width that is a part of the first switching period among the continuous switching periods. The peak time position within the switching period is searched.

  Next, in the second switching period following the first switching period, the control unit 12 outputs the output current during the monitoring period (for example, during 5 time slots) with the peak time position in the switching period as a center. Monitor I3.

  In the case of digital control, the peak time position in the switching period is the maximum of the absolute value of the output current I3 in the first to nth time slots obtained by dividing the switching period into n equal parts (n: a positive integer). The value is the time slot position monitored.

  Thus, in the second switching cycle (current switching cycle), the output current is monitored around the time position at which the output current becomes maximum in the first switching cycle (previous switching cycle). The timing at which the output current I3 reaches the threshold current can be efficiently captured. This eliminates the need for the control unit 12 to constantly monitor the output current I3.

  Therefore, according to the second embodiment, PFC control in the continuous current mode can be performed without monitoring the output current over the entire switching period.

  As a result, for example, the output current I and other monitoring processes (such as monitoring the input / output voltage of the power converter 10) can be performed with one DSP, and there is no need to provide a DSP dedicated to PFC control. As a result, the power converter having the PFC circuit 15 can be reduced in size and cost.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. . You may combine suitably the component covering different embodiment. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1,10 Power converter 2,12 Control part 3 Noise filter 4 LC filter 5 Bridge circuit 6 AC voltage detection circuit 7 DC voltage detection circuit 11 Rectification smoothing circuit 13 Input voltage detection circuit 14 Output voltage detection circuit 15 PFC circuit 30 External load C1, C2, C11, C12 Smoothing capacitors C3, C4, C5 Capacitors D1-D4, D11-D15 Diodes I1, I2, I3
L1-L4, L11 Inductors Ith1-Ith7 Threshold currents M1-M7 Monitor period N1, N2 Nodes P1-P7 Switching cycle PS AC power supplies Q1-Q4, Q11 Switching elements R1, R2, R3 Resistors T1, T2, T3, T4 Input / output Terminals Ton1-Ton7 On width TS Time slot

Claims (9)

A rectifying and smoothing circuit for outputting a DC voltage obtained by rectifying and smoothing an AC voltage between the first node and the second node;
An inductor having one end connected to the first node to which the DC voltage is supplied;
A switching element for electrically connecting or insulating between the other end of the inductor and the second node;
A diode having an anode connected to the other end of the inductor;
A smoothing capacitor having one end connected to the cathode of the diode and the other end connected to the second node;
A control unit that controls the switching element to be turned on at a constant switching period and controls the switching element to be turned off within the switching period, and monitors an output current flowing through the switching element;
With
The control unit searches for a peak time position in the switching period in which the maximum value of the absolute value of the output current is monitored for a monitoring period that is a part of the first switching period among consecutive switching periods. In the second switching period following the first switching period, the output current is monitored during the monitoring period with the peak time position in the switching period as the center.   The peak time position in the switching period is the position of the time slot in which the maximum value is monitored among the first to nth time slots obtained by dividing the switching period into n equal parts (n: a positive integer). The power converter according to claim 1, wherein A power converter that converts AC power output from an AC power source into DC power, and converts DC power output from the DC power source into AC power,
A first input / output terminal; and a second input / output terminal for connecting the AC power supply between the first input / output terminal;
A fourth input / output terminal for connecting an external load between the third input / output terminal and the third input / output terminal;
A first smoothing capacitor having one end connected to the first input / output terminal and the other end connected to the second input / output terminal, and a first smoothing capacitor having one end connected to one end of the first smoothing capacitor An LC filter having an inductor and a second inductor having one end connected to the other end of the first smoothing capacitor;
A second smoothing capacitor having one end connected to the third input / output terminal and the other end connected to the fourth input / output terminal;
A first switching element having one end connected to the third input / output terminal and the other end connected to the other end of the second inductor, and a first switching element from the other end of the first switching element; A first rectifying element that allows current to flow only in the direction of one end of the
A second switching element having one end connected to the other end of the second inductor and the other end electrically connected to the fourth input / output terminal; and a second switching element from the other end of the second switching element to the second A second rectifying element that allows current to flow only in the direction of one end of the switching element;
A third switching element having one end connected to the third input / output terminal and the other end connected to the other end of the first inductor; and a third switching element from the other end of the third switching element. A third rectifying element that allows current to flow only in the direction of one end of the
A fourth switching element having one end connected to the other end of the first inductor and electrically connected to the other end of the fourth input / output terminal; A fourth rectifying element that allows current to flow only in the direction of one end of the switching element;
On / off control of the first to fourth switching elements and at least one of a first output current flowing through the second switching element and a second output current flowing through the fourth switching element A control unit for performing a current monitoring operation for monitoring
With
The controller is
When performing the converter operation of converting the AC power output from the AC power source connected between the first and second input terminals into DC power and outputting the DC power from the third and fourth input / output terminals, the second And the fourth switching element is controlled to be turned on at a constant switching cycle, and then controlled from on to off within the switching cycle, and in a part of the first switching cycle among the continuous switching cycles. For a certain monitoring period, a peak time position in the switching period in which the maximum absolute value of the first output current or the second output current is monitored is searched, and a second switching period following the first switching period is searched. Then, during the monitoring period with the peak time position in the switching period as a center, the current monitoring operation is performed.
The power converter characterized by the above-mentioned.   The control unit monitors an AC voltage input from the AC power source in the converter operation, and the first output current or the second output current monitored in the second switching period is changed to the AC voltage. 4. The power conversion device according to claim 3, wherein when the threshold current determined based on the threshold current is reached, the second and fourth switching elements are controlled to be turned off. 5.   The peak time position in the switching period is the position of the time slot in which the maximum value is monitored among the first to nth time slots obtained by dividing the switching period into n equal parts (n: a positive integer). The power converter according to claim 3 or 4, characterized by the above.   The external load is a DC-DC converter or a battery that steps down or boosts a DC voltage output from the third and fourth input / output terminals to a voltage suitable for a battery connected to the output of the external load. It exists, The power converter device in any one of Claims 3-5 characterized by the above-mentioned.   In the case of performing an inverter operation in which DC power output from a DC power source connected between the third and fourth input / output terminals is converted into AC power and output from the first and second input / output terminals, the control is performed. And the second switching element and the third switching element with respect to on / off of the first switching element and the fourth switching element so that the first to fourth switching elements perform a full bridge operation. The power conversion device according to claim 3, wherein on / off of the switching elements is switched complementarily. A rectifying and smoothing circuit that outputs a DC voltage obtained by rectifying and smoothing an AC voltage between a first node and a second node, and an inductor having one end connected to the first node to which the DC voltage is supplied A switching element that electrically connects or insulates between the other end of the inductor and the second node, a diode having an anode connected to the other end of the inductor, and one end at the cathode of the diode A smoothing capacitor connected to the second node and connected to the other end of the second node, the switching element is controlled to be turned on at a constant switching period, and the switching element is controlled to be turned off within the switching period. A control method of a power converter comprising a control unit that monitors the output current flowing through
The controller is
For a monitoring period that is a part of the first switching period among consecutive switching periods, search for a peak time position in the switching period in which the maximum value of the absolute value of the output current is monitored,
In the second switching period following the first switching period, the output current is monitored during the monitoring period centering on the peak time position in the switching period.
A method for controlling a power conversion device. A power conversion device that converts AC power output from an AC power source into DC power and converts DC power output from the DC power source into AC power, comprising: a first input / output terminal; and the first input / output terminal; And a fourth input / output terminal for connecting an external load between the third input / output terminal and the third input / output terminal. A first smoothing capacitor having one end connected to the first input / output terminal and the other end connected to the second input / output terminal, and one end connected to one end of the first smoothing capacitor. An LC filter having one inductor and a second inductor having one end connected to the other end of the first smoothing capacitor, one end connected to the third input / output terminal, and the fourth input / output terminal. A second smoothing capacitor with the other end connected to And a first switching element having one end connected to the third input / output terminal and the other end connected to the other end of the second inductor, and a first switching element from the other end of the first switching element. A first rectifying element that allows current to flow only in the direction of one end of the switching element, one end connected to the other end of the second inductor, and the other end electrically connected to the fourth input / output terminal. One end is connected to the second switching element, the second rectifying element that allows current to flow only from the other end of the second switching element to the one end of the second switching element, and the third input / output terminal. , A third switching element having the other end connected to the other end of the first inductor, and a third switching element that allows current to flow only from the other end of the third switching element to one end of the third switching element. A rectifying element and the first input; A fourth switching element having one end connected to the other end of the capacitor and electrically connected to the fourth input / output terminal, and a fourth switching element from the other end of the fourth switching element. The fourth rectifying element that allows current to flow only in the direction of one end and the first to fourth switching elements are on / off controlled, and the first output current that flows through the second switching element and the fourth A control unit for performing a current monitoring operation for monitoring at least one of the second output currents flowing through the switching element,
When performing the converter operation in which AC power output from the AC power source connected between the first and second input terminals is converted into DC power and output from the third and fourth input / output terminals, the control unit Is
The second and fourth switching elements are controlled to be turned on at a constant switching period, and then controlled from on to off within the switching period,
The switching period peak time during which the maximum value of the absolute value of the first output current or the second output current is monitored for a monitoring period which is a part of the first switching period among consecutive switching periods. Search for a location
In the second switching period following the first switching period, the current monitoring operation is performed during the monitoring period around the peak time position in the switching period.
A method for controlling a power conversion device.

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