JPWO2020144796A1 - Power converter - Google Patents

Abstract

A power conversion device including two or more switching circuits (101, 102) in which output terminals are connected in parallel to each other and a control device (80) for controlling the switching circuit, and at least one of the switching circuits. The switching circuit is a switching circuit (101) that performs bidirectional conversion between the input terminal and the output terminal, and the control device (80) sets both power output directions of the switching circuit (101) that performs bidirectional conversion. Control is performed by switching between the bidirectional operation mode in which the direction is directed and the cross current suppression mode in which the mode is restricted in one direction.

Description

The present application relates to a power converter.

Devices that use power converters connected in parallel, such as those equipped with circuits with power conversion functions connected in parallel and devices that supply power converted from different power sources to one load or power source, are known. Has been done.
For example, Patent Document 1 has a control unit and a plurality of power supply units, and each of the power supply units has an output unit that converts and outputs an input power source and the output power exceeds the first power value. In this case, a transition request is issued to shift the stopped power supply unit to the power supply state, and when the output power falls below the second power value smaller than the first power value, the power supply unit being supplied is stopped. A power supply system with a control unit that transitions to a state is disclosed. In this system, it is disclosed that the output current of each power supply unit is controlled to have the same value by the current balance function, and the power supply unit is switched by the control unit to form a redundant system.

Further, Patent Document 2 discloses that a plurality of storage batteries are connected via a bidirectional inverter connected in parallel to a bus. When a voltage difference occurs between the storage batteries, a current (cross current) is generated between the storage batteries. Therefore, a cross flow prevention device is provided between the bidirectional inverter and the storage battery, and the current passes only in the charging direction during charging and only in the discharging direction during discharging. It is disclosed to let you.

JP-A-2018-85793 Japanese Unexamined Patent Publication No. 2014-54072 (FIGS. 10 and 11)

It is known that a circuit having a power conversion function is composed of a switching circuit composed of a plurality of switching elements. A plurality of power conversion circuits connected in parallel as described above are composed of a plurality of switching circuits, and at least one switching circuit has a function of performing power conversion in both directions, including a switching circuit having a bidirectional function. When power is supplied to a load by multiple switching circuits, an ineffective current called cross current is generated in which current flows from another switching circuit to a switching circuit having a bidirectional function, and the circuit efficiency deteriorates due to an increase in loss. There was a point.

In Patent Document 2, a cross flow prevention device that allows current to pass only in the charging direction during charging and only in the discharging direction during discharging is separately provided in response to charging / discharging of the storage battery, but the system is not connected to the storage battery. In, there were restrictions such as not being able to match the timing of charging and discharging.

The present application discloses a technique for solving the above-mentioned problems, and an object of the present application is to provide a highly efficient power conversion device by suppressing loss due to cross current in a power conversion device without separately providing a cross flow prevention device. It is said.

The power conversion device disclosed in the present application includes a plurality of switching circuits that perform power conversion between an input terminal and an output terminal, and a control device that controls the plurality of switching circuits. Each of the output terminals is connected in parallel, and at least one of the plurality of switching circuits is a switching circuit that performs bidirectional conversion between the input terminal and the output terminal, and the control device is the control device. Control is performed to switch between a bidirectional operation mode in which the power output direction of the switching circuit performing bidirectional conversion is bidirectional and a cross flow suppression mode in which the input terminal is restricted to the direction of the output terminal.

According to the power conversion device disclosed in the present application, when power is supplied to a load from two or more switching circuits, the switching circuit that performs bidirectional conversion operates not only in the bidirectional operation mode but also in the cross current suppression mode. Therefore, it is possible to suppress the loss by stopping the bidirectional operation and making it unidirectional, and it is possible to provide a highly efficient power conversion device without providing a cross current prevention device.

It is a circuit block diagram of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the switching pattern in the bidirectional operation mode of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a circuit block diagram which showed the electric power direction when the cross current is not generated of the electric power conversion apparatus which concerns on Embodiment 1. FIG. It is a circuit block diagram which showed the electric power direction at the time of cross current generation of the electric power conversion apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the switching pattern in the cross current suppression mode of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a flowchart which shows an example of the operation mode switching control in the power conversion apparatus which concerns on Embodiment 1. FIG. It is a circuit block diagram of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a figure which shows the switching pattern in the bidirectional operation mode of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a circuit block diagram which showed the electric power direction when the cross current is not generated of the electric power conversion apparatus which concerns on Embodiment 2. FIG. It is a circuit block diagram which showed the electric power direction at the time of the cross current occurrence of the electric power conversion apparatus which concerns on Embodiment 2. FIG. It is a figure which shows an example of the switching pattern in the cross current suppression mode of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a figure which shows an example of the switching pattern in the cross current suppression mode of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a circuit diagram which showed another example of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a hardware block diagram of the control device of the power conversion device which concerns on Embodiments 1 and 2.

Hereinafter, the present embodiment will be described with reference to the drawings. In each figure, the same reference numerals indicate the same or corresponding parts.

Embodiment 1.
The power conversion device according to the first embodiment will be described with reference to FIGS. 1 to 6.
FIG. 1 is a circuit diagram showing a basic configuration of the power conversion device according to the first embodiment. In FIG. 1, the power conversion device performs power conversion between two power supplies 11 and 12 and a power supply 13 corresponding to a load. Here, each power source is a DC power source. The voltage / current detection unit 41 is connected to the DC power supply 11, and the capacitor 21, the switching circuit 101, and the output terminal of the switching circuit 101 to which the input terminal of the switching circuit 101 is connected are connected to the rear side of the voltage / current detection unit 41. The capacitors 23 are connected in series. Similarly, the DC power supply 12 is connected to the voltage / current detection unit 42, and the capacitor 22, the switching circuit 102, and the output terminal of the switching circuit 102 to which the input terminal of the switching circuit 102 is connected to the rear side of the voltage / current detection unit 42. The connected capacitors 24 are connected in series. The capacitor 23 and the capacitor 24 are connected in parallel with the voltage / current detection unit 43, and the voltage / current detection unit 43 is connected to the DC power supply 13.

The switching circuit 101 is a bidirectional converter having a switching element S11 and a switching element S12 connected in series, a reactor 31 between a connection terminal between the switching element S11 and the switching element S12 and one end of a capacitor 23, and is a DC power supply 11 The step-down operation is performed in the direction of the DC power supply 13 and the step-up operation is performed in the direction of the DC power supply 11 from the DC power supply 13.
That is, in the figure, the reactor 31 is connected between the connection terminals of the two switching elements S11 and S12 and the positive terminals of the output terminals of the switching circuit 101. The reactor 31 may be connected between the positive terminal of the input terminal of the switching circuit 101 and the connection terminals of the two switching elements S11 and S12.

On the other hand, the switching circuit 102 is a unidirectional converter having a switching element S21 and a diode D21 connected in series, a reactor 32 between a connection terminal between the switching element S21 and the diode D21 and one end of the capacitor 24, and is a DC power supply 12 The step-down operation is performed in the direction of the DC power supply 13.

The voltage value and current value detected by the voltage / current detection units 41 to 43 are input to the control device 80, and the respective switching circuits 101 and 102 are controlled by the control device 80 based on the detected voltage value and current value. ..

FIG. 2 is a diagram showing a switching pattern when the switching circuit 101 is operated in the bidirectional operation mode. The switching element S11 and the switching element S12 are provided with a dead time Td and alternately switched (soft switching). In a state where power is transmitted from the DC power supply 11 to the DC power supply 13, the transmission power is controlled by the ratio of the on-time Ton of the switching element S11 to the switching cycle Ts. On the other hand, by turning on the switching element S12 during the off time of the switching element S12, the synchronous rectification operation becomes possible and the circuit efficiency can be improved.

Each switching element includes a MOSFET (Metal-Oxide-Semiconductor-Field-Effect-Transistor) which is a switch and a diode connected in antiparallel to the switch. When the switching element is on, the switch is on.
In the switching element, a current in one direction flows by applying a voltage higher than the gate threshold voltage to the gate of the switch, and a current in the opposite direction flows regardless of whether a voltage higher than the gate threshold voltage is applied to the gate of the switch. Pass through. When a current flows in the opposite direction, if a voltage higher than the gate threshold voltage is not applied to the gate of the switch, the diodes connected in antiparallel are conducted. On the other hand, when a voltage higher than the gate threshold voltage is applied to the gate of the switch, if the voltage drop of the switch is lower than the forward voltage drop of the diode, a current flows through the switch (synchronous rectification) and the forward voltage drop of the diode. If the voltage drop of the switch is higher than that, current flows through the diode.

FIG. 3 shows an arrow indicating the power direction when no cross current is generated in the power conversion device according to the first embodiment. In this state, power is supplied from the DC power supply 11 to the DC power supply 13 by the switching circuit 101, and power is supplied from the DC power supply 12 to the DC power supply 13 by the switching circuit 102. That is, it shows a state in which power is supplied from two different DC power supplies 11 and 12 to one DC power supply 13.

On the other hand, FIG. 4 shows an arrow indicating the power direction when a cross current is generated in the power conversion device according to the first embodiment. The power input from the DC power supply 12 to the connection points Q1 and Q2 via the switching circuit 102 in a transient state such as the voltage relationship between the capacitor 21 and the capacitor 23 and the load fluctuation is transmitted to the DC power supply 11 via the switching circuit 101. A cross current that flows in the direction and is then added to the power supplied from the DC power supply 11 and supplied to the DC power supply 13 via the switching circuit 101 is generated. Since the cross current becomes a current reciprocating in the switching circuit 101, an excessive loss may be generated in the switching circuit 101, which may lead to deterioration of the efficiency of the power conversion device.

Therefore, as shown in FIG. 5, a cross flow suppression mode is provided in which the switching element S12 is always turned off. In the cross flow suppression mode, only the switching element S11 switches, the switching element S21 is always off, and the diode in the element is in a conductive state. As a result, the switching circuit 101 is limited to unidirectional operation in which power is transmitted only in the direction from the DC power supply 11 to the DC power supply 13, that is, in the direction from the input terminal to the output terminal. That is, the synchronous rectification operation is stopped and the occurrence of cross current is suppressed.

Synchronous rectification originally suppresses the loss during power conversion, but by introducing the cross flow suppression mode, even if the loss generated by the cross flow exceeds the loss reduction amount due to the synchronous rectification operation, it is always bidirectional. It is possible to improve the circuit efficiency as compared with operating in the operation mode.
The control device 80 switches between the cross flow suppression mode and the bidirectional operation mode.

Next, switching control between the cross flow suppression mode and the bidirectional operation mode in the control device 80 will be described.
The control device 80 compares the detection results of the voltage / current detection units 41 to 43 with a predetermined threshold value, determines whether or not the conditions for generating cross current are satisfied, and switches between the bidirectional operation mode and the cross flow suppression mode.

[Control Example 1-1]
The input power from the DC power supply 12 is calculated using the voltage value and the current value detected by the voltage / current detection unit 42, compared with the input power threshold value in the DC power supply 12 determined in advance, and the bidirectional operation mode and the cross flow suppression. You can switch between modes.
For example, when the power output to the DC power supply 13 as a load fluctuates, the input power P12in from the DC power supply 12 decreases, and exceeds a predetermined input power threshold Pth, a cross flow occurs in the switching circuit 101. It is judged that the condition is satisfied, and the bidirectional operation mode is switched to the cross flow suppression mode. On the contrary, when the power output to the DC power supply 13 fluctuates and the input power P12in from the DC power supply 12 increases and exceeds the input power threshold Pth, it is determined that it is out of the condition that cross current occurs in the switching circuit 101. Switch from cross-flow suppression mode to bidirectional operation mode.

The cross current generation condition is related to the magnitude of the output power to the DC power supply 13 which is a load. In this example, assuming a low load, it is assumed that when the input power P12in from the DC power supply 12 becomes smaller than the input power threshold value Pth, a cross current generation condition is satisfied. Depending on the magnitude of the load, that is, the magnitude of the output power to the DC power supply 13, the cross current generation condition is reversed, and when the input power P12in becomes larger than the input power threshold Pth, the cross current generation condition is satisfied, which is the opposite of the above. The operation mode may be switched.

Further, the input power threshold value Pth, which is the threshold value of the input power from the DC power supply 12, can be set to a different value depending on the switching direction of the operation mode. In this case, when the power output to the DC power supply 13 as a load fluctuates and the input power P12in from the DC power supply 12 decreases and exceeds the predetermined first input power threshold value Pth1, the switching circuit 101 is reached. It is determined that the conditions under which cross current occurs are satisfied, and the bidirectional operation mode is switched to the cross flow suppression mode. On the contrary, when the power output to the DC power supply 13 fluctuates and the input power P12in from the DC power supply 12 increases and exceeds the second input power threshold value Pth2, it is out of the condition that a cross flow to the switching circuit 101 occurs. Is determined, and the cross flow suppression mode is switched to the bidirectional operation mode.

FIG. 6 shows a flowchart of the above control example.
In step ST1, the switching circuit 101 is controlled by the control device 80 in the bidirectional operation mode to operate.
In step ST2, the voltage value and the current value detected by the voltage / current detection unit 42 are input to the control device 80, and the input power P12in from the DC power supply 12 is calculated.
In step ST3, when the input power P12in from the DC power supply 12 decreases and exceeds the predetermined input power threshold first Pth1 (YES in step ST3), it is determined that the cross current generation condition is satisfied, and step ST4 is performed. move on. In step ST4, the switching circuit 101 is controlled and operated by switching from the bidirectional operation mode to the cross flow suppression mode by the control device 80.
In step ST3, if the predetermined input power threshold first Pth1 is not exceeded (NO in step ST3), the operation in the bidirectional operation mode continues.

The switching circuit 101 that operates in the cross current suppression mode after step ST4 is set to YES in step ST3 when the input power P12in from the DC power supply 12 increases and exceeds a predetermined second input power threshold Pth2 (YES in step ST4). ), Returning to step ST1, the switching circuit 101 is controlled and operated by switching from the cross flow suppression mode to the bidirectional operation mode by the control device 80.
The switching circuit 101 that operates in the cross current suppression mode after step ST4 has a second input power P12in from the DC power supply 12 if it does not exceed a predetermined second input power threshold Pth2 (NO in step ST4). The operation in the cross current suppression mode is continued until the input power threshold Pth2 is exceeded.
When a plurality of input power threshold values Pth are not provided, it can be explained by replacing step ST3 with P12in <Pth and step ST5 with P12in> Pth in FIG.

[Control Example 1-2]
The input power from the DC power supply 12 is calculated using the voltage value and current value detected by the voltage / current detection unit 42, and the DC power supply 13 is output using the voltage value and current value detected by the voltage / current detection unit 43. The output power of the DC power supply 13 is calculated, the ratio of the input power from the DC power supply 12 to the output power to the DC power supply 13 is calculated, and the bidirectional operation mode and the cross current suppression mode are determined and switched by comparing with a predetermined ratio threshold value. You may.
For example, when the power ratio R (p12p13) = P12in / P13out between the output power P13out to the DC power supply 13 as a load and the input power P12in from the DC power supply 12 decreases and exceeds the first power ratio threshold value Rth1. It is determined that the condition for generating cross current to the switching circuit 101 is satisfied, and the cross flow suppression mode is switched to the bidirectional operation mode. On the contrary, when the power ratio R (p12p13) increases and the second power ratio threshold value Rth2 is exceeded, it is determined that the condition is out of the condition that the cross flow to the switching circuit 101 occurs, and the bidirectional operation mode is switched to the cross flow suppression mode. ..

The processing flow can be explained by replacing step ST3 in FIG. 6 with R (p12p13) <Rth1 and step ST5 with R (p12p13)> Rth2.

[Control Example 1-3]
The input power from the DC power supply 11 is calculated using the voltage value and current value detected by the voltage / current detection unit 41, and the voltage value and current value detected by the voltage / current detection unit 43 are used to connect to the DC power supply 13. The output power of the DC power supply 13 may be calculated, and the ratio of the input power from the DC power supply 11 to the output power to the DC power supply 13 may be calculated.

As described above, the threshold value for shifting from the bidirectional operation mode to the cross flow suppression mode and the threshold value for shifting from the cross flow suppression mode to the bidirectional operation mode may be different values when switching the operation mode, and the same threshold value may be used for operation. You may switch the mode.
As described above, if the hysteresis characteristic is provided by setting the threshold value for shifting from the bidirectional operation mode to the cross flow suppression mode and the threshold value for shifting from the cross flow suppression mode to the bidirectional operation mode as different values, chattering occurs at the time of mode transition. Can be prevented. In control example 1-1, Pth1 <Pth2 may be set. Further, the opposite Pth2 <Pth1 may be set.

In the above example, a control example is shown in which the input power from the DC power supplies 11 and 12 and the output power to the DC power supply 13 are calculated, the threshold value of the power is set, and the operation mode is switched. When the DC power supplies 11 to 13 are devices such as converters that perform constant voltage control, they operate by comparing the current value detected by the voltage / current detectors 41 to 43 with the preset current threshold value without performing power calculation. You can switch modes.
Further, the voltage value detected by the voltage / current detection unit 41 is compared with the voltage value detected by the voltage / current detection unit 43, and the voltage value detected by the voltage / current detection unit 41 is detected by the voltage / current detection unit 43. When the voltage value is higher than the voltage value, it may be switched to operate in the cross current suppression mode, and when it is lower than the voltage value, it may be switched to operate in the bidirectional operation mode.

This control method is particularly effective when the input / output voltage or input / output current of the inverter can be set, the cross current generation conditions are clear, and the threshold value can be set.

In the above description, the control device 80 compares the detection results of the voltage / current detection units 41 to 43 with a predetermined threshold value to determine whether or not the conditions for generating cross current are satisfied, and sets the bidirectional operation mode and the cross flow suppression mode. Although the switching has been performed, an example of switching the operation mode by comparing the magnitude of the loss in each operation mode will be described below.

A loss map in which a loss value corresponding to an input / output voltage or a current is calculated for the switching circuit 101 is provided in advance in the control device 80, and bidirectionally so that the circuit loss is reduced based on the detection result of the voltage / current detection unit 41 or 43. The operation mode and the cross current suppression mode are determined and switched. The circuit loss may be calculated using the voltage value and the current value detected by the control device 80, and an operation of switching between the bidirectional operation mode and the cross current suppression mode may be performed so that the circuit loss becomes small. In this case, it is particularly effective when the conditions for generating cross currents are complicated.

For example, the loss maps of the cross flow suppression mode and the bidirectional operation mode according to the voltage and current of the DC power supplies 11 to 13 are stored in the control device 80 in advance, and the voltage values detected by the voltage and current detectors 41 to 43 are stored in advance. And, it is determined which operation mode has the smallest circuit loss from the current value and switched.
The control method using this loss map is particularly effective when the conditions for generating cross currents are complicated.

Although the switching circuits 101 and 102 have been described in FIG. 1 as an example in which a step-down chopper circuit that performs a step-down operation from the DC power supplies 11 and 12 to the DC power supply 13 is configured, the present invention is not limited to this. The boost chopper may be configured to perform a boost operation in the direction from the DC power supplies 11 and 12 to the DC power supply 13, or the switching circuit 101 and the switching circuit 102 may be different circuits.
Further, both the switching circuits 101 and 102 may have a circuit configuration capable of bidirectional conversion. In this case, cross current may occur in both switching circuits 101 and 102, and the control operation of the switching element of each circuit becomes more complicated than in the above case.

Further, although the example in which the power supplies 11 to 13 are used as the DC power supplies 11 to 13 has been described, any or all of the DC power supplies 11 to 13 may be used as an AC power supply and an AC / DC converter.

As described above, according to the present embodiment, the operation modes of the switching circuit capable of bidirectional power conversion by detecting the input / output voltage value and the current value of the power conversion device are set to the bidirectional operation mode and the cross flow. Since the control is performed so as to stop the on operation of the switching element capable of conducting power in the generation direction and switch to the cross flow suppression mode in which the power is unidirectionally operated, the switching circuit is performed without providing a dedicated cross flow suppression device or the like. It is possible to suppress the loss due to the cross current and provide a highly efficient power conversion device.

Embodiment 2.
FIG. 7 is a circuit diagram showing a basic configuration of the power conversion device according to the second embodiment. In FIG. 7, the power conversion device according to the second embodiment performs power conversion between the two DC power supplies 11 and 12 and the DC power supply 13 corresponding to the load, similarly to the power conversion device according to the first embodiment. It is a thing. The description of the same parts and the same operations as in the first embodiment is omitted.
The voltage / current detection unit 41 is connected to the DC power supply 11, and is connected to the capacitor 21, the switching circuit 201, and the output terminal of the switching circuit 201 connected to the input terminal of the switching circuit 201 on the rear side of the voltage / current detection unit 41. In addition, the capacitors 23 are connected in series. Similarly, the voltage / current detection unit 42 is connected to the DC power supply 12, and the capacitor 22, the switching circuit 202, and the output terminal of the switching circuit 202 connected to the input terminal of the switching circuit 202 on the rear side of the voltage / current detection unit 42. The capacitors 24 connected to the are connected in series. The capacitor 23 and the capacitor 24 are connected in parallel with the voltage / current detection unit 43, and the voltage / current detection unit 43 is connected to the DC power supply 13.

The switching circuit 201 includes a primary side switching circuit composed of four switching elements S11 to S14, a secondary side switching circuit composed of four switching elements S15 to S18, and an AC terminal of the primary side switching circuit at one end. The reactor 31 connected to one end of the reactor 31, the reactor 33 whose one end is connected to one end of the AC terminal of the secondary side switching circuit, and one end of the primary winding to the other end of the reactor 31 and the other end to the primary side. It is composed of an isolation transformer 51 connected to the other end of the AC terminal of the switching circuit, one end of the secondary winding connected to the other end of the reactor 33, and the other end connected to the other end of the AC terminal of the secondary side switching circuit. To.

On the other hand, the switching circuit 202 includes a primary side switching circuit composed of four switching elements S21 to S24, a secondary side rectifying circuit composed of four diodes D22 to D25, and one end of the primary side switching circuit. The reactor 32 connected to one end of the AC terminal and one end of the primary winding are connected to the other end of the reactor 32 and the other end is connected to the other end of the AC terminal of the primary switching circuit, and both ends of the secondary winding. Is composed of an isolated transformer 52 connected to a secondary side rectifying circuit.

FIG. 8 is a diagram showing a switching pattern when the switching circuit 201 is operated in the bidirectional operation mode. The switching element S11 and the switching element S12, the switching element S13 and the switching element S14, the switching element S15 and the switching element S16, and the switching element S17 and the switching element S18 are respectively provided with a dead time Td to perform switching alternately. In a state where power is transmitted from the DC power supply 11 to the DC power supply 13, the ratio of the on-time Ton1 of the primary side switching circuit to the switching cycle Ts, the ratio of the on-time Ton2 of the secondary side switching circuit, and the primary side switching circuit. And the phase difference Φ of the secondary side switching circuit is used to control the transmission power.

FIG. 9 shows a circuit configuration diagram in which the power direction when no cross current is generated in the power conversion device according to the second embodiment is indicated by an arrow. In this state, the switching circuit 201 supplies power in the direction from the DC power supply 11 to the DC power supply 13, and the switching circuit 202 supplies power in the direction from the DC power supply 12 to the DC power supply 13. That is, it is a state in which power is supplied from two different DC power sources to one DC power source.

On the other hand, FIG. 10 is a circuit configuration diagram showing the power direction when a cross current is generated in the power conversion device according to the second embodiment by arrows. The power input from the DC power supply 12 to the connection points Q3 and Q4 via the switching circuit 202 in a transient state such as the voltage relationship between the capacitor 21 and the capacitor 23 and the load fluctuation is transferred to the DC power supply 11 via the switching circuit 201. A cross flow is generated which flows in the direction of the above and then is added to the electric power supplied from the DC power source 11 and supplied to the DC power source 13 via the switching circuit 201. Since the cross current becomes a current reciprocating in the switching circuit 201, an excessive loss may occur in the switching circuit 201, which may lead to deterioration of the efficiency of the power conversion device.

Therefore, as shown in FIGS. 11 and 12, a cross flow suppression mode is provided in which two switching elements of the secondary side switching circuit are always turned off. FIG. 11 shows a case where the switching element S15 and the switching element S16, which are two elements of one leg of the leg consisting of a pair of upper and lower arms of the secondary side switching circuit, are turned off, and FIG. 12 shows the secondary side switching circuit. This is a case where the switching element S15 and the switching element S17, which are two elements of the upper arms of the above, are turned off.

In the cross flow suppression mode, only two switching elements of the primary side switching circuit and the secondary side switching circuit are switched, and two of the secondary side switching circuits are always turned off. As a result, the switching circuit 201 is limited to unidirectional operation in which power is transmitted only in the direction from the DC power supply 11 to the DC power supply 13. That is, it is possible to suppress the occurrence of cross current in the switching circuit 201.

By introducing the cross flow suppression mode, it is possible to prevent the occurrence of loss due to the cross flow, and it is possible to improve the circuit efficiency as compared with the case where the circuit is always operated in the bidirectional operation mode.

In FIG. 11, a case where the switching element S15 and the switching element S16 of one leg of the secondary side switching circuit are turned off has been described. However, the switching element S15 and the switching element S16 are switched to operate the other of the secondary side switching circuits. The leg switching element S17 and the switching element S18 may be turned off.
Further, in FIG. 12, a case where the switching element S15 and the switching element S17, which are elements between the upper arms of the secondary side switching circuit, are turned off has been described. However, the switching element S15 and the switching element S17 are switched to operate on the lower side. The switching element S16 and the switching element S18, which are elements between the arms, may be turned off.
Switching between the cross flow suppression mode and the bidirectional operation mode is performed by the control device 80.

Similar to the first embodiment, in the control device 80, the voltage value and the current value detected by the voltage / current detection units 41 to 43 are compared with a predetermined threshold value, and the bidirectional operation mode and the cross flow suppression mode are switched. ..
[Control Example 2-1]
The input power from the DC power supply 12 is calculated using the voltage value and the current value detected by the voltage / current detection unit 42, compared with the input power threshold value in the DC power supply 12 determined in advance, and the bidirectional operation mode and the cross flow suppression. You can switch between modes.
For example, when the power output to the DC power supply 13 as a load fluctuates, the input power P12in from the DC power supply 12 decreases, and exceeds a predetermined input power threshold Pth, a cross flow occurs in the switching circuit 101. It is judged that the condition is satisfied, and the bidirectional operation mode is switched to the cross flow suppression mode. On the contrary, when the power output to the DC power supply 13 fluctuates and the input power P12in from the DC power supply 12 increases and exceeds the input power threshold Pth, it is determined that it is out of the condition that cross current occurs in the switching circuit 201. Switch from cross-flow suppression mode to bidirectional operation mode.

The cross current generation condition is related to the magnitude of the output power to the DC power supply 13 which is a load. In this example, it is assumed that a low load is assumed as in the first embodiment, and that when the input power P12in from the DC power supply 12 becomes smaller than the input power threshold value Pth, a cross current generation condition is established. Depending on the magnitude of the load, that is, the magnitude of the output power to the DC power supply 13, the cross current generation condition is reversed, and when the input power P12in becomes larger than the input power threshold Pth, the cross current generation condition is satisfied, which is the opposite of the above. The operation mode may be switched.

Further, the input power threshold value Pth, which is the threshold value of the input power from the DC power supply 12, can be set to a different value depending on the switching direction of the operation mode. In this case, when the power output to the DC power supply 13 as a load fluctuates and the input power P12in from the DC power supply 12 decreases and exceeds the predetermined first input power threshold value Pth1, the switching circuit 201 is reached. It is determined that the conditions under which cross current occurs are satisfied, and the bidirectional operation mode is switched to the cross flow suppression mode. On the contrary, when the power output to the DC power supply 13 fluctuates and the input power P12in from the DC power supply 12 increases and exceeds the second input power threshold value Pth2, it is out of the condition that a cross flow to the switching circuit 201 occurs. Is determined, and the cross flow suppression mode is switched to the bidirectional operation mode.
The processing flow of this control example is the same as that of FIG. 6 of the first embodiment.

[Control Example 2-2]
The input power from the DC power supply 12 is calculated using the voltage value and current value detected by the voltage / current detection unit 42, and the DC power supply 13 is output using the voltage value and current value detected by the voltage / current detection unit 43. The output power of the DC power supply 13 is calculated, the ratio of the input power from the DC power supply 12 to the output power to the DC power supply 13 is calculated, and the bidirectional operation mode and the cross current suppression mode are determined and switched by comparing with a predetermined ratio threshold value. You may.
For example, when the power ratio R (p12p13) = P12in / P13out between the output power P13out to the DC power supply 13 as a load and the input power P12in from the DC power supply 12 decreases and exceeds the first power ratio threshold value Rth1. In addition, it is determined that the condition for generating cross current to the switching circuit 201 is satisfied, and the cross flow suppression mode is switched to the bidirectional operation mode. On the contrary, when the power ratio R (p12p13) increases and the second power ratio threshold value Rth2 is exceeded, it is determined that the condition is out of the condition that the cross flow to the switching circuit 201 occurs, and the bidirectional operation mode is switched to the cross flow suppression mode. ..

[Control Example 2-3]
The input power from the DC power supply 11 is calculated using the voltage value and current value detected by the voltage / current detection unit 41, and the voltage value and current value detected by the voltage / current detection unit 43 are used to connect to the DC power supply 13. The output power of the DC power supply 13 may be calculated, and the ratio of the input power from the DC power supply 11 to the output power to the DC power supply 13 may be calculated.

As described above, the threshold value for shifting from the bidirectional operation mode to the cross flow suppression mode and the threshold value for shifting from the cross flow suppression mode to the bidirectional operation mode may be different values when switching the operation mode, and the same threshold value may be used for operation. You may switch the mode.
As described above, if the hysteresis characteristic is provided by setting the threshold value for shifting from the bidirectional operation mode to the cross flow suppression mode and the threshold value for shifting from the cross flow suppression mode to the bidirectional operation mode as different values, chattering occurs at the time of mode transition. Can be prevented. In control example 2-1 it may be set that Pth1 <Pth2. Further, the opposite Pth2 <Pth1 may be set.

In the above example, a control example is shown in which the input power from the DC power supplies 11 and 12 and the output power to the DC power supply 13 are calculated, the threshold value of the power is set, and the operation mode is switched. When the DC power supplies 11 to 13 are devices such as converters that perform constant voltage control, they operate by comparing the current value detected by the voltage / current detectors 41 to 43 with the preset current threshold value without performing power calculation. You can switch modes.
Further, the voltage value detected by the voltage / current detection unit 41 is compared with the voltage value detected by the voltage / current detection unit 43, and the voltage value detected by the voltage / current detection unit 41 is detected by the voltage / current detection unit 43. When the voltage value is higher than the voltage value, it may be switched to operate in the cross current suppression mode, and when it is lower than the voltage value, it may be switched to operate in the bidirectional operation mode.

This control method is particularly effective when the input / output voltage or input / output current of the inverter can be set, the cross current generation condition is clear, and the threshold value can be set, as described in the first embodiment.

Next, in the control device 80, an example of switching the operation mode by comparing the magnitude of the loss in each operation mode will be described.

A loss map in which a loss value corresponding to an input / output voltage or a current is calculated for the switching circuit 201 is provided in advance in the control device 80, and bidirectionally so that the circuit loss is reduced based on the detection result of the voltage / current detection unit 41 or 43. The operation mode and the cross current suppression mode are determined and switched. The circuit loss may be calculated using the voltage value and the current value detected by the control device 80, and an operation of switching between the bidirectional operation mode and the cross current suppression mode may be performed so that the circuit loss becomes small. In this case, it is particularly effective when the conditions for generating cross currents are complicated.

For example, the loss maps of the cross flow suppression mode and the bidirectional operation mode according to the voltage and current of the DC power supplies 11 to 13 are stored in the control device 80 in advance, and the voltage values detected by the voltage and current detectors 41 to 43 are stored in advance. And, it is determined which operation mode has the smallest circuit loss from the current value and switched.
The control method using this loss map is particularly effective when the cross current generation conditions are complicated, as described in the first embodiment.

In the present embodiment, the phases of the switching elements S13 and S14 with respect to the switching elements S11 and S12 and the phases of the switching elements S17 and S18 with respect to the switching elements S15 and S16 have been described in a state of being delayed by 180 degrees. Even when it is used as a control variable, the same effect can be obtained by switching the operation mode.
When controlling the phases of the switching elements S13 and S14 with respect to the switching elements S11 and S12 and the phases of the switching elements S17 and S18 with respect to the switching elements S15 and S16, switching loss is reduced by connecting a capacitor in parallel with each switching element. A reduceable soft switching operation can be realized. In this case, since the secondary side switching circuit is hard switching in the cross flow suppression mode, the case where soft switching and cross flow occur in the bidirectional operation mode and the case where hard switching and cross flow are suppressed in the cross flow suppression mode are taken into consideration. It is possible to effectively switch between the bidirectional operation mode and the cross flow suppression mode so that the circuit loss is minimized.

Further, FIG. 13 shows a circuit configuration diagram of another power conversion device according to the second embodiment. A switching circuit that adjusts the output to the power supply 13 on the rear stage side in which the switching circuit 201 and the switching circuit 202 are connected in parallel. The configuration may be such that 203 is provided. In the determination of operation mode switching, the power may be calculated using the voltage value and the current value detected by the voltage / current detection unit 43 as the output power to the DC power supply 13, or the voltage / current detection unit 44 may detect the power. The power may be calculated using the voltage value and the current value. Further, as the voltage value and current value on the DC power supply 13 side, the value detected by either the voltage / current detection unit 43 or the voltage / current detection unit 44 may be used.

Further, as described in the first embodiment, the DC power supplies 11 to 13 may be configured such that any or all of the DC power supplies 11 to 13 are AC power supplies and AC / DC converters.

As described above, according to the second embodiment, as in the first embodiment, the operation mode of the switching circuit capable of bidirectional power conversion by detecting the input / output voltage value and the current value of the power conversion device is set. , Since the control is performed to switch between the bidirectional operation mode and the cross flow suppression mode in which the switching element capable of conducting power in the direction of generation of the cross flow is stopped and the cross flow suppression mode is performed in the unidirectional operation, a dedicated cross flow suppression device is used. It is possible to suppress the loss due to the cross current in the switching circuit and provide a highly efficient power conversion device without providing the above.

The switching elements S11 to S18, S21 to S24, and S31 of the first and second embodiments have been described by using MOSFETs as switches constituting the semiconductor switching elements, but other switching elements such as IGBTs (Insulated-Gate Bipolar Transistors) have been described. A switch can be used.

The control device 80 of the first and second embodiments is composed of a processor 1000 and a storage device 2000 as shown in FIG. 14 as an example of hardware. Although the storage device is not shown, it includes a volatile storage device such as a random access memory (RAM: Random Access Memory) and a non-volatile auxiliary storage device such as a flash memory. Further, an auxiliary storage device of a hard disk may be provided instead of the flash memory. The processor 1000 executes the program input from the storage device 2000. In this case, a program is input to the processor 1000 from the auxiliary storage device via the volatile storage device (EEPROM: Electrically Erasable Programmable Read Only Memory). Further, the processor 1000 may output data such as a calculation result to the volatile storage device of the storage device 2000, or may store the data in the auxiliary storage device via the volatile storage device. The processor 1000 may be provided with various logic circuits such as ASIC (Application Specific Integrated Circuit), IC (Integrated Circuit), DSP (Digital Signal Processor), and various signal processing circuits as arithmetic processing devices.

Although the present disclosure describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are those of a particular embodiment. It is not limited to application, 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 herein. 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.

11-13 power supply, 21-26 capacitor, 31-34 reactor, 41-44 voltage / current detector, 51, 52 isolation transformer, S11-S18, S21-S24, S31 switching element, D21-D25, D31 diode, 101, 102, 201-203 switching circuit, 80 controller, 1000 processor, 2000 storage device

The power conversion device disclosed in the present application includes a plurality of switching circuits that perform power conversion between an input terminal and an output terminal, and a control device that controls the plurality of switching circuits. Each of the output terminals is connected in parallel, and at least one of the plurality of switching circuits is a switching circuit that performs bidirectional conversion between the input terminal and the output terminal, and is a switching circuit of the plurality of switching circuits. It has a first voltage / current detection unit connected to at least one of the input terminals, and a second voltage / current detection unit connected to the output terminals connected in parallel with the plurality of switching circuits. In the control device, the power output direction of the switching circuit that performs bidirectional conversion is bidirectional based on the values detected by the first voltage / current detection unit and the second voltage / current detection unit. Control is performed to switch between the bidirectional operation mode and the cross current suppression mode that limits the direction from the input terminal to the output terminal.

Claims (9)

Multiple switching circuits that perform power conversion between the input terminal and the output terminal,
A control device for controlling the plurality of switching circuits is provided.
The output terminals of the plurality of switching circuits are connected in parallel.
At least one of the plurality of switching circuits is a switching circuit that performs bidirectional conversion between the input terminal and the output terminal.
The control device controls to switch between a bidirectional operation mode in which the power output direction of the switching circuit performing bidirectional conversion is bidirectional and a cross flow suppression mode in which the input terminal is restricted to the direction of the output terminal. Power converter. In the switching circuit that performs bidirectional conversion,
The switching element that performs the switching operation in the bidirectional operation mode includes a switch and a diode connected in antiparallel to the switch.
The power conversion device according to claim 1, wherein in the cross flow suppression mode, the switch of the switching element is turned off to conduct the diode. The switching circuit that performs bidirectional conversion is
Two switching elements connected in series and
A chopper circuit having a reactor between either the positive terminal of the input terminal or the positive terminal of the output terminal and the connection terminal of the two switching elements connected in series is provided.
The two switching elements each have the switch and the diode connected in antiparallel to the switch.
The power conversion device according to claim 2, wherein in the cross flow suppression mode, the switch of the switching element is turned off to conduct the diode. The switching circuit that performs bidirectional conversion is
An isolated converter in which the AC terminal of the secondary side full bridge circuit having the plurality of the switching elements is connected to the secondary side winding of the isolation transformer, and the series terminal of the full bridge circuit is the output terminal.
The power conversion device according to claim 2, wherein in the cross flow suppression mode, the switches of two of the switching elements constituting the full bridge circuit are turned off. The switch according to claim 4, wherein the switch to be turned off in the cross flow suppression mode is the switch provided in each of the two switching elements of one of the two legs constituting the full bridge circuit. Power converter. The power conversion device according to claim 4, wherein the switch to be turned off in the cross flow suppression mode is the switch provided in each of the two switching elements of the upper arms or the lower arms of the full bridge circuit. .. A first voltage / current detector connected to the input terminal of each of the plurality of switching circuits,
A second voltage / current detection unit connected to the output terminal connected in parallel of the plurality of switching circuits is provided.
The control device compares the values detected by the first voltage / current detection unit and the second voltage / current detection unit with a predetermined threshold value, and sets the bidirectional operation mode and the cross flow suppression mode. The power conversion device according to claim 1. A first voltage / current detector connected to the input terminal of each of the plurality of switching circuits,
A second voltage / current detection unit connected to the output terminal connected in parallel of the plurality of switching circuits is provided.
The switching circuit that performs bidirectional conversion performs a soft switching operation in the bidirectional operation mode and a hard switching operation in the cross flow suppression mode.
The control device is based on the values detected by the first voltage / current detection unit and the second voltage / current detection unit.
2. Claim 2 in which the loss generated when operated in the cross flow suppression mode is compared with the loss generated when operated in the bidirectional operation mode, and control is performed to select an operation mode having a small generated loss. The power converter described in. The switching circuit that performs bidirectional conversion is
The AC terminal of the full bridge circuit on the primary side having the plurality of switching elements is connected to the primary winding of the isolation transformer.
An isolated type in which the AC terminal of the secondary side full bridge circuit having the plurality of switching elements is connected to the secondary side winding of the isolation transformer, and the series terminal of the secondary side full bridge circuit is the output terminal. Is a converter
The power conversion device according to claim 8, wherein the control device performs power conversion by phase shift control for both the primary side and secondary side full bridge circuits in the bidirectional operation mode.

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