JP2020184829A - Power conversion device and power conversion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device and a power conversion control device capable of discharging electric charges of a smoothing capacitor connected in parallel with a load in a shorter time. A power conversion device (3) includes a smoothing capacitor (36) connected in parallel with a load (2) and two switching elements (32a) connected in parallel with the smoothing capacitor and connected in series. And 32b, 33a and 33b) are a plurality of voltage conversion circuits (32, 33) having upper arms and lower arms, one end is connected to the power supply (1), and the other end constitutes one voltage conversion circuit. The reactor group (31) including the reactors (31a, 31b) connected between the two switching elements, and the first one including the smoothing capacitor by on / off driving of each switching element when discharging the charge of the smoothing capacitor. A closed circuit, and a control unit (35) that includes two or more reactors and a second closed circuit that includes each upper arm or each lower arm of two or more voltage conversion circuits and does not include a smoothing capacitor. Be prepared. [Selection diagram] Fig. 1

Description

The present invention relates to a plurality of voltage conversion circuits in which two switching elements are connected in series, a power conversion device in which two switching elements are connected in parallel with a smoothing capacitor, and a power conversion control device.

Some power conversion devices include a plurality of half-bridge circuits, which are voltage conversion circuits in which two switching elements are connected in series. In this type of power converter, a smoothing capacitor and a load are usually connected between both ends of the half-bridge circuit. To suppress the discharge current that flows when the electric charge stored in the smoothing capacitor is discharged, one end is a power supply and the other end is a reactor connected between two switching elements that make up one of the half-bridge circuits. It is also discharged through (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-17750

In a power converter with a high voltage applied to a smoothing capacitor, it is stipulated by law that the stored charge can be discharged immediately in order to prevent electric shock. Conventionally, the electric charge stored in the smoothing capacitor is discharged by turning on and off the switching elements constituting each half-bridge circuit to form a closed circuit including the smoothing capacitor, two reactors, and two half-bridge circuits. It has been

By forming this closed circuit, the electric charge stored in the smoothing capacitor can be discharged. However, it is desired that the time required for the discharge be shorter.

The present invention has been made to solve such a problem, and provides a power conversion device and a power conversion control device capable of discharging the electric charge of a smoothing capacitor connected in parallel with a load in a shorter time. The purpose is.

The power conversion device according to the present invention includes a smoothing capacitor connected in parallel with respect to the load and a plurality of switching elements connected in parallel with the smoothing capacitor and connected in series as an upper arm and a lower arm, respectively. A voltage conversion circuit, a reactor group including a reactor whose one end is connected to a power supply and whose other end is connected between two switching elements constituting one of a plurality of voltage conversion circuits, and a smoothing capacitor. When discharging the stored charge, the on / off drive of each switching element that constitutes a plurality of voltage conversion circuits constitutes a smoothing capacitor, two or more reactors that form a reactor group, and a plurality of voltage conversion circuits. A first closed circuit including one or more voltage conversion circuits, two or more reactors constituting a reactor group, and each upper arm or each lower arm of two or more voltage conversion circuits constituting a plurality of voltage conversion circuits. A control unit for forming a second closed circuit including the smoothing capacitor and not including the smoothing capacitor.

The power conversion control device according to the present invention includes a smoothing capacitor connected in parallel with respect to the load, and a plurality of switching elements connected in parallel with the smoothing capacitor and connected in series as an upper arm and a lower arm, respectively. A voltage conversion circuit, and a power conversion circuit having a reactor group including a reactor having one end connected to a power supply and the other end connected between two switching elements constituting one of a plurality of voltage conversion circuits. When discharging the charge stored in the smoothing capacitor, the switching elements that make up a plurality of voltage conversion circuits are driven on and off, and the smoothing capacitor, two or more reactors that make up the reactor group, and a plurality of voltage conversions are performed. On each of the first closed circuit including two or more voltage conversion circuits constituting the circuit, the two or more reactors constituting the reactor group, and the two or more voltage conversion circuits constituting the plurality of voltage conversion circuits. A process is performed to form a second closed circuit that includes an arm or each lower arm and does not include a smoothing capacitor.

According to the present invention, the electric charge of the smoothing capacitor connected in parallel with the load can be discharged in a shorter time.

It is a figure which shows the structural example of the power conversion apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the structural example of the power conversion control apparatus which concerns on Embodiment 1 of this invention. It is a figure explaining each signal example generated in the normal situation and the discharge execution situation respectively. It is a figure explaining the example of the closed circuit formed in mode 1. It is a figure explaining the example of the closed circuit formed in mode 2. It is a figure explaining the example of the closed circuit formed in mode 3. It is a figure explaining the example of the closed circuit formed in mode 4. It is a figure explaining the example of the change of the current value at the time of the discharge execution state of each reactor which constitutes a reactor group. It is a figure explaining the specific example of a reactor group. It is a figure which shows the structural example of the power conversion apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the structural example of the power conversion apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows the structural example of the power conversion control apparatus which concerns on Embodiment 3 of this invention. It is a figure explaining each signal example generated by the power conversion control device which concerns on Embodiment 3 of this invention in a normal situation and a discharge execution state respectively. It is a figure explaining the example of the change of the value of the current flowing through each reactor at the time of a discharge execution state in the power conversion apparatus which concerns on Embodiment 3 of this invention.

Hereinafter, embodiments of the power conversion device and the power conversion control device according to the present invention will be described with reference to the drawings. In each figure, the same elements, elements that can be regarded as the same, or corresponding elements are designated by the same reference numerals.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a power conversion device according to a first embodiment of the present invention. First, the configuration of the power conversion device 3 will be specifically described with reference to FIG.

The power conversion device 3 shown in FIG. 1 is a full-bridge type DC (Direct Current) / DC converter including two half-bridge circuits as voltage conversion circuits 32 and 33 for voltage conversion. A battery 1 is connected as a power source and a load 2 is connected to the power conversion device 3. As a result, the power conversion device 3 converts the voltage of the electric power supplied from the battery 1 into a voltage desirable for the load 2, and supplies the electric power after the voltage conversion to the load 2. The type of load 2 is not particularly limited. The load 2 may include another power conversion device such as an inverter.

The positive electrode terminal of the battery 1 is connected to one end of the contactor 10. The negative electrode terminal of the battery 1 is connected to one end of the smoothing capacitor 37. The other end of the smoothing capacitor 37 is connected to the other end of the contactor 10. A voltage sensor 38 for detecting the voltage value V1 between both ends of the smoothing capacitor 37 is connected to both ends of the smoothing capacitor 37. The signal indicating the voltage value V1 is output from the voltage sensor 38 to the control device 35. The contactor 10 is provided in, for example, the battery 1, or is provided separately from the battery 1 and the power conversion device 3. Here, for convenience, it is assumed that the contactor 10 is provided as one component. When the power conversion device 3 is mounted on an electric vehicle, opening / closing control of the contactor 10 is performed by, for example, an ECU (Electronic Control Unit).

One ends of the reactors 31a and 31b constituting the reactor group 31 are connected to the other end of the smoothing capacitor 37. The other end of the reactor 31a is connected to a connection point 32c between the two switching elements 32a and 32b constituting the voltage conversion circuit 32. The other end of the reactor 31b is connected to a connection point 33c between the two switching elements 33a and 33b constituting the voltage conversion circuit 33.

The switching elements 32a to 33b used in the two voltage conversion circuits 32 and 33 are devices in which diodes are connected in parallel in opposite directions between collectors and emitters of IGBTs (Insulated Gate Bipolar Transistors). Thereby, the anode and cathode of the diode are connected to the emitter and collector, respectively. The switching elements 32a to 33b are not limited to devices using the IGBT. The switching elements 32a to 33b may be MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor), and are formed of wide bandgap semiconductors using SiC (Silicon Carbide), GaN (Gallium Nitride), or the like. There may be.

The reactors 31a and 31b connected to the voltage conversion circuits 32 and 33, respectively, have a function of boosting the voltage of the electric power supplied from the battery 1. It also has a function of suppressing the discharge current that flows when discharging the electric charge stored in the smoothing capacitor 36 connected between both ends of the load 2.

As shown in FIG. 9, the reactor group 31 may be a magnetically coupled type having reactors 31a and 31b connected in opposite polarities, for example, a transformer. When the magnetically coupled reactor group 31 is adopted, the reactor group 31 can be miniaturized, so that the power conversion device 3 can also be miniaturized.

The current sensor group 34 is a plurality of current sensors for detecting the current values IL2 and IL1 of the reactors 31a and 31b constituting the reactor group 31. Therefore, the current sensor group 34 includes a current sensor 34b for detecting the value IL2 of the current flowing through the reactor 31a, and a current sensor 34a for detecting the value IL1 of the current flowing through the reactor 31b. The signal indicating the current value IL2 is output from the current sensor 34b to the control device 35. The signal indicating the current value IL1 is output from the current sensor 34a to the control device 35. The current flowing through the reactor 31a corresponds to the current flowing through the voltage conversion circuit 32. The current flowing through the reactor 31b corresponds to the current flowing through the voltage conversion circuit 33.

The voltage conversion circuit 32 has a configuration in which two switching elements 32a and 32b are connected in series. The collector of the IGBT that constitutes the switching element 32b is connected to one end of the load 2 and one end of the smoothing capacitor 36. The emitter of the IGBT constituting the switching element 32a is connected to the other end of the load 2 and the other end of the smoothing capacitor 36. As a result, the connection point 32c is connected to the emitter of the IGBT that constitutes the switching element 32b and the collector of the IGBT that constitutes the switching element 32a.

The voltage conversion circuit 33 has a configuration in which two switching elements 33a and 33b are connected in series. The collector of the IGBT that constitutes the switching element 33b is connected to one end of the load 2 and one end of the smoothing capacitor 36. The emitter of the IGBT constituting the switching element 33a is connected to the other end of the load 2 and the other end of the smoothing capacitor 36. As a result, the connection point 33c is connected to the emitter of the IGBT that constitutes the switching element 33b and the collector of the IGBT that constitutes the switching element 33a.

A voltage sensor 39 for detecting the voltage value V2 between both ends of the smoothing capacitor 36 is connected between both ends of the smoothing capacitor 36. The signal indicating the voltage value V2 is output from the voltage sensor 39 to the control device 35.

The control device 35 processes one of the voltage values V1 and V2 detected by the two voltage sensors 38 and 39, and the current values IL2 and IL1 detected by the two current sensors 34a and 34b, respectively, and performs four switching. The elements 32a to 33b are driven on and off. The control device 35 corresponds to both the control unit and the power conversion control device in the present embodiment. Here, the portion of the power conversion device 3 other than the control device 35 is referred to as a “power conversion circuit” to distinguish it.

Next, with reference to FIG. 2, the configuration of the control device 35, that is, the power conversion control device according to the present embodiment will be specifically described. FIG. 2 is a diagram showing a configuration example of the power conversion control device according to the first embodiment of the present invention.

As shown in FIG. 2, the control device 35 includes a current error amount generation unit 351, a current controller 352, a duty generation unit 353, a gate signal generation unit 354, a first voltage control unit 355a, and a second voltage control unit 355b. , And a switch 356. In the present embodiment, the components other than the gate signal generation unit 354, for example, may be realized by one information processing device, for example, a microcomputer. In that case, the microcomputer becomes a part of the control device 35 by executing the process for realizing the components other than the gate signal generation unit 354. From this, in a broad sense, the power conversion control device according to the present embodiment includes all the components shown in FIG. In a narrow sense, the power conversion control device according to the present embodiment does not include the gate signal generation unit 354.

First, the outline of the operation of the control device 35 will be described. The control device 35 drives each of the switching elements 32a to 33b on and off by PWM (Pulse Width Modulation) control. In a normal state where the discharge of the electric charge of the smoothing capacitor 36 is not assumed, the control device 35 has a duty ratio for driving the switching elements 32a to 33b on and off so that the voltage value V2 matches the set reference voltage value V2ref. Determine the duty. The control device 35 operates this duty ratio duty so that the difference between the current values IL1 and IL2 becomes zero. By the operation, the duty ratio Duty 32 for the voltage conversion circuit 32 and the duty ratio Duty 33 for the voltage conversion circuit 33 are generated from the duty ratio Duty. The gate signal generation unit 354 is a signal for on / off driving the two switching elements 32a and 32b of the voltage conversion circuit 32 and the two switching elements 33a and 33b of the voltage conversion circuit 33 according to the generated duty ratios Duty 32 and Duty 33. Is generated and output.

The signal generated by the gate signal generation unit 354 is a signal input to the gate of each IGBT constituting the switching elements 32a to 33b. “Gate_32a” shown in FIG. 2 represents a signal input to the gate of the IGBT constituting the switching element 32a. Similarly, "Gate_32b", "Gate_33a", and "Gate_33b" represent signals input to the gates of the respective IGBTs constituting the switching elements 32b to 33b, respectively.

The amount of operation of the duty ratio Duty is determined by using the current values IL1 and IL2. In the present embodiment, paying attention to this, at the time of discharging assuming discharge of the electric charge of the smoothing capacitor 36, the operation amount is switched to the one assuming discharge. Thereby, the electric charge of the smoothing capacitor 36 can be discharged in a shorter time. Higher safety is ensured by discharging the electric charge of the smoothing capacitor 36 in a shorter time.

The current error amount generation unit 351 normally generates and outputs the difference ILERr1 between the current values IL1 and IL2 as the current error amount ILERr. Further, when the electric charge of the smoothing capacitor 36 is discharged, the current error amount generation unit 351 adds a set value to the difference ILERr1 and outputs the addition result as the current error amount ILERr1. Therefore, the current error amount generation unit 351 includes a set value switch 351a, a subtractor 351b, and an adder 351c.

The subtractor 351b calculates the difference ILERr1 by subtracting the current value IL2 from the current value IL1. The adder 351c calculates the current error amount ILERr by adding the value ILERr2 output by the set value switcher 351a to the difference ILERr1. This current error amount ILERr is output from the current error amount generation unit 351 to the current controller 352.

The current values IL1 and IL2 both fluctuate. Therefore, the actual current values IL1 and IL2 used for the subtraction by the subtractor 351b are, for example, the average value at a predetermined time or the filtered value.

The set value switcher 351a switches the content of the output value ILERr2 according to the instruction 1 which is a binary signal functioning as a command, that is, a signal having two states of H (High) and L (Low). H, in other words, indication 1 having a logical value of 1 requires a charge discharge operation of the smoothing capacitor 36. L, in other words, the instruction 1 having a logical value of 0 requests a normal operation, that is, a power supply operation to the load 2.

When the load 2 includes a motor, the instruction 1 indicates a situation in which the charge of the smoothing capacitor 36 should be discharged, and a situation in which regenerative power, which is the power from the motor functioning as a generator, is supplied. Sometimes it becomes H. Both the discharge current and the regenerative power in these two situations can be used for charging the battery 1 and supplying power to another load connected to the battery 1. The second voltage control unit 355b assumes charging of the battery 1 and power supply to another load.

Even when the regenerative power is used for power supply, the regenerative power is consumed in the power conversion circuit. As a result, the power conversion circuit also functions as a regenerative brake when the power conversion device 3 is mounted on an electric vehicle or the like. Therefore, the braking force required for the mechanical brake mounted on the electric vehicle is smaller.

The contactor 10 allows the electrical connection between the battery 1 and the power converter 3 and the disconnection of the connection. In the situation where power is supplied from the battery 1, the contactor 10 is closed and the battery 1 and the power converter 3 are connected to each other. In a situation where a discharge current flows and a situation in which regenerative power is supplied, the contactor 10 is in either an open state or a closed state in which the connection between the battery 1 and the power conversion device 3 is disconnected. This is because, for example, if the battery 1 is in a rechargeable state, both the discharge current and the regenerative power can be used to charge the battery 1 as described above. Hereinafter, in order to avoid confusion, the situation in which power is supplied to the load 2 is referred to as a “normal situation”, and the other situations are collectively referred to as a “discharge execution situation”. The discharge execution status includes a situation in which the discharge current due to the electric charge of the smoothing capacitor 36 or the regenerative power is simply consumed, and a situation in which the discharge current or the regenerative power is used to supply power to the battery 1 or another load. Is done.

When the instruction 1 is L, the set value switch 351a outputs the value ILERr2 of 0. As a result, the current error amount generation unit 351 outputs the difference ILERr1 as the current error amount ILERr. As a result, the current error amount generation unit 351 functions to match the current values IL1 and IL2.

On the other hand, when the instruction 1 is H, the set value switch 351a outputs, for example, the set set value ILset as the value ILR2. Therefore, the current error amount generation unit 351 outputs the addition result obtained by adding the set value ILset to the difference ILERr1 as the current error amount ILERr. As a result, the current error amount generation unit 351 functions so that the electric charge of the smoothing capacitor 36 can be efficiently discharged.

The current controller 352 calculates the operation amount ΔD of the duty ratio duty using the current error amount ILERr input from the current error amount generation unit 351 and outputs it to the duty generation unit 353. Well-known techniques such as P control, PI control, or PID (Proportional-Integral-Differential) control can be used to calculate the manipulated variable ΔD.

The first voltage control unit 355a generates a duty ratio Duty 2 for matching the voltage value V2 with the reference target voltage value V2ref. Therefore, the first voltage control unit 355a includes a subtractor 3551 and a voltage controller 3552.

The subtractor 3551 calculates the difference V2err between them by subtracting the voltage value V2 from the target voltage value V2ref. The voltage controller 3552 uses the difference V2err to calculate the duty ratio Duty 2 for matching the voltage value V2 with the target voltage value V2err. The calculated duty ratio Duty2 is output to the switch 356. Well-known techniques such as P control, PI control, or PID control can be used to calculate the duty ratio Duty2 using the difference V2err.

Unlike the first voltage control unit 355a, the second voltage control unit 355b generates a duty ratio Duty1 for matching the voltage value V1 with the reference target voltage value V1ref, and switches the generated duty ratio Duty1. Output to device 356. Therefore, the second voltage control unit 355b includes a subtractor 3551 and a voltage controller 3552, similarly to the first voltage control unit 355a. Since the operation of these components is the same as that of the first voltage control unit 355a, detailed description thereof will be omitted.

The switch 356 selects one of the input duty ratios Duty1 and Duty2 according to the instruction 2 which is a binary signal similar to the instruction 1, and outputs the selected one to the duty generation unit 353 as the duty ratio Duty. To do. For example, when the instruction 2 is L, the switch 356 selects the duty ratio Duty 2 and outputs the selected duty ratio Duty 2 as the duty ratio Duty. When the instruction 2 is H, the switch 356 selects the duty ratio Duty 1 and outputs the selected duty ratio Duty 1 as the duty ratio Duty.

The instruction 2 becomes H when the discharge is executed and when the voltage value V1 should be maintained. (For example, an important device to the system is connected to the battery 1 side, and the contactor 10 is opened before the discharge execution status is reached. An important device to the system is connected to the battery 1 as another load. In such a case, the voltage value V1 needs to be maintained. The instruction 1 needs to be set to H after the switch 356 outputs the duty ratio Duty 1 as the duty ratio Duty. Therefore, the instruction 1 is set to H. After the instruction 2 becomes H, it becomes H.

In this embodiment, it is also assumed that power is supplied to another load connected to the battery 1 during the discharge execution state. However, that assumption does not have to be made. As a result, the second voltage control unit 355b does not have to be provided. When the second voltage control unit 355b is not provided, instead of the duty ratio Duty1, a predetermined duty ratio, for example, a duty ratio fixed at 50% is assumed, and a set value ILset to be output as the value ILR2 to the set value switcher 351a is set. Just set it.

The duty generation unit 353 generates duty ratios Duty 32 and Duty 33 used for on / off driving of the switching elements 32a to 33b. The duty ratios Duty 32 and Duty 33 are generated by operating the duty ratio Duty input from the switch 356 using the operation amount ΔD input from the current controller 352. Therefore, the duty generation unit 353 includes a subtractor 353a and an adder 353b.

The subtractor 353a subtracts the manipulated variable ΔD from the duty ratio Duty. The subtraction result is output to the gate signal generation unit 354 as a duty ratio Duty 32.

On the other hand, the adder 353b adds the manipulated variable ΔD to the duty ratio Duty. The addition result is output to the gate signal generation unit 354 as a duty ratio Duty 33.

The gate signal generator 354 includes two signal generators 354a and 354b. The duty ratio Duty 32 is input to the signal generator 354a, and the duty ratio Duty 33 is input to the signal generator 354b.

The signal generator 354a generates signals Gate_32a and Gate_32b for on / off driving the two switching elements 32a and 32b constituting the voltage conversion circuit 32 according to the duty ratio Duty 32. The signals Gate_32a and Gate_32b are complementary signals to each other, and when one is H, the other is L. The duty ratio Duty 32 is a value indicating the ratio of the time during which the IGBT constituting the switching element 32b is driven on in one cycle. This cycle is a cycle that is a unit time for performing PWM control, that is, a switching cycle.

The signal generator 354b generates signals Gate_33a and Gate_33b for on / off driving the two switching elements 33a and 33b constituting the voltage conversion circuit 33 according to the duty ratio Duty 33. The signals Gate_33a and Gate_33b are also complementary signals, and when one signal is H, the other signal is L. Since there are two voltage conversion circuits 32 and 33, the signals Gate_33a and Gate_33b are out of phase with the signals Gate_32a and Gate_32b, that is, they are 180 degrees out of phase.

In the above configuration, the first voltage control unit 355a corresponds to the first condition setting unit in the present embodiment. The generated duty ratio Duty 2 corresponds to the first driving condition. The second voltage control unit 355b corresponds to the third condition setting unit in the present embodiment. The generated duty ratio Duty 1 corresponds to the third driving condition. The duty generation unit 353 corresponds to the second condition setting unit in the present embodiment. Both the duty ratios Duty32 and Duty33 correspond to the second driving condition. The switch 356 corresponds to the selection unit in this embodiment.

The subtractor 351b of the current error amount generation unit 351 and the current controller 352 correspond to the change amount determination unit in the present embodiment. The operation amount ΔD corresponds to the change amount in the present embodiment. The set value switch 351a and the adder 351c correspond to the change amount operation unit in the narrow sense in the present embodiment. The change amount operation unit in a broad sense further includes a current controller 352. This is because the final result of the set value switcher 351a outputting the set value ILset as the value ILERr2 is obtained by the processing of the current controller 352. The gate signal generation unit 354 corresponds to the signal generation unit in the present embodiment.

FIG. 3 is a diagram illustrating an example of each signal generated in a normal situation and a discharge execution situation, respectively. In FIG. 3, the upper row shows an example of each signal generated in a normal situation, and the lower row shows an example of each signal generated in a discharge execution situation. The normal situation is a situation where the instruction 1 is 0, that is, L, and the discharge execution situation is a situation where the instruction 1 is 1, that is, H. In FIG. 3, each signal, that is, the signals Gate_32a, Gate_32b, Gate_33a, and Gate_33b represents the signal level by two values of H and L.

In FIG. 3, "Tsw" represents a switching period. “Ta” represents the H time, which is the time during which H of the signal Gate_32a continues in a normal situation, in other words, the L time, which is the time during which L of the signal Gate_32b continues. "Ta'" represents the H time of the signal Gate_32a in the discharge execution state. As a result, in a normal situation, the duty ratio Duty32 = Ta / Tsw.

Further, "Tb" represents the H time of the signal Gate_33a in a normal situation, in other words, the L time of the signal Gate_33b. "Tb'" represents the H time of the signal Gate_33a in the discharge execution state.

As for the difference between H time Ta and Ta'(= Ta-Ta'), the manipulated variable ΔD was used assuming that the duty ratio duty is the same and the sum of the current values IL1 and IL2 (= IL1 + IL2) is also the same. It is caused by the subtraction operation. Under that assumption, between the current error amount ILERr used by the current controller 352 to generate the manipulated variable ΔD in the normal situation and the current error amount ILERr used by the current controller 352 to generate the manipulated variable ΔD in the discharge execution situation. Has a difference in the set value ILset as described above. From this, FIG. 3 shows that the content of the manipulated variable ΔD can be indirectly controlled by the set value ILset.

The duty ratio duty operation according to the set value ILset may be performed separately from the operation using the operation amount ΔD. That is, the duty ratio duty operation according to the set value ILset may be performed directly.

Numerical values 1, 3, and 4 are shown as modes in the upper and lower rows of FIG. This mode corresponds to the closed circuit formed in the power conversion circuit, and the numerical value represents the type of the closed circuit actually formed. Here, with reference to FIGS. 4 to 7, the closed circuit formed by each node will be specifically described. 4 to 7 are diagrams illustrating an example of a closed circuit formed in modes 1 to 4, respectively.

In mode 1, as shown in FIG. 4, a closed circuit including the smoothing capacitor 36, that is, a smoothing capacitor 36 → switching element 32b → reactor 31a → reactor 31b → switching element 33a → smoothing capacitor 36 is discharged from the smoothing capacitor 36. A closed circuit through which current flows is formed. By this closed circuit, in mode 1, the electric charge stored in the smoothing capacitor 36 can be directly discharged and the energy can be transferred to the reactors 32a and 32b.

In mode 4, as shown in FIG. 7, a closed circuit including the smoothing capacitor 36, that is, a smoothing capacitor 36 → switching element 33b → reactor 31b → reactor 31a → switching element 32a → smoothing capacitor 36 is discharged from the smoothing capacitor 36. A closed circuit through which current flows is formed. By this closed circuit, even in mode 4, the electric charge stored in the smoothing capacitor 36 can be directly discharged and the energy can be transferred to the reactors 31a and 31b.

In mode 2, as shown in FIG. 5, the closed circuit including the smoothing capacitor 36 is not formed, and the closed circuit including the reactor group 31 is formed. In the closed circuit, the energy stored in the reactor group 31 causes a current to flow in the path of, for example, reactor 31a → reactor 31b → switching element 33b → switching element 32b → reactor 31a. When the discharge current flows from the smoothing capacitor 36, energy is stored in the reactor group 31. Therefore, when a current flows through this closed circuit, conduction loss, that is, power loss in the power conversion circuit occurs even if a closed circuit through which the discharge current from the smoothing capacitor 36 flows is not formed, and the smoothing capacitor 36 is used. Discharge of the charge of the power conversion circuit including is realized.

Even in mode 3, as shown in FIG. 6, a closed circuit including the smoothing capacitor 36 is not formed, and a closed circuit including the reactor group 31 is formed. In the closed circuit, the energy stored in the reactor group 31 causes a current to flow in the path of, for example, reactor 31a → reactor 31b → switching element 33a → switching element 32a → reactor 31a. Since the current flows through this closed circuit, the electric charge of the power conversion circuit including the smoothing capacitor 36 is discharged even in the mode 3.

Both the closed circuit formed in the mode 1 and the mode 4 correspond to the first closed circuit in the present embodiment. The closed circuit formed in mode 2 corresponds to the second closed circuit in the present embodiment.

In the lower part of FIG. 3, the modes transition cyclically in the order of mode 1 → mode 3 → mode 4 → mode 3. The transition changes depending on the boost ratio. Depending on the boost ratio, the mode transitions cyclically in the order of mode 1 → mode 2 → mode 4 → mode 2.

In the transition as described above, a closed circuit is always formed. However, a period during which the closed circuit is not formed may be provided within the switching cycle. For this reason, the mode transition, that is, the type of closed circuit to be formed, the order thereof, and the like are not particularly limited.

By the mode transition as shown in the lower part of FIG. 3, in addition to the closed circuit including the smoothing capacitor 36, the closed circuit not including the smoothing capacitor 36 is formed. Therefore, the power in the power conversion circuit is consumed even while the closed circuit including the smoothing capacitor 36 is not formed. Due to this power consumption, the electric charge of the smoothing capacitor 36 can be discharged more efficiently. As a result, the electric charge of the smoothing capacitor 36 can be discharged in a shorter time.

The electric charge is stored in the smoothing capacitor 37 in addition to the smoothing capacitor 36. The electric charge stored in the smoothing capacitor 37 can be discharged by the closed circuit formed in the mode 1 and the mode 4. In this embodiment, the closed circuit including the smoothing capacitor 37 is also formed in mode 3. Therefore, the electric charge of the smoothing capacitor 37 can be discharged in a shorter time.

FIG. 8 is a diagram illustrating an example of a change in the current value of each of the reactors constituting the reactor group when the discharge is executed. FIG. 8 shows the target voltage values V1ref and V2ref switched by the indications 1, 2, and 2 in addition to the current values IL1 and IL2 of the reactors 31a and 31b. The current values IL1 and IL2 here are average values or filtered values as described above.

“I1” in FIG. 8 represents the current value of the electric power supplied from the battery 1. Since the power conversion device 3 includes two voltage conversion circuits 32 and 33, the sum of the current values IL1 and IL2 is I1, and the current values IL1 and IL2 are usually I1 / 2.

As described above, in a normal situation, both instruction 1 and instruction 2 are L. When the contactor 10 is opened from the normal state, the connection with the battery 1 is cut off, and the state changes to the discharge execution state, the instruction 1 becomes H after the instruction 2 becomes H, as shown in FIG. When the instruction 1 becomes H, the on / off drive of the switching elements 32a to 33b assuming the discharge of the charge of the smoothing capacitor 36 is started. In other words, the direct discharge of the electric charge of the smoothing capacitor 36 due to the formation of the closed circuit as shown in FIGS. 4 to 7 and the consumption of the energy generated in the reactor group 31 by the discharge are started. As a result, as shown in FIG. 8, a difference in the set value ILset set by the current error amount generation unit 315 occurs between the current values IL2 and IL1 of the reactors 31a and 31b.

The upper limit temperature is usually set for the parts used in the power conversion circuit. From this, a temperature sensor for temperature detection is used in at least one of the switching elements 32a to 33b, at least one of the smoothing capacitors 36 and 37, and at least one of the reactors 31a and 31b. May be provided and the detected temperature may be used for control. For example, when the detected temperature exceeds a predetermined upper limit value, the instruction 1 may be changed from H to L. Even so, since the amount of current per unit time is lower than before the temperature exceeds the upper limit value, not only the parts in which the temperature exceeding the upper limit value is detected but also the parts whose temperature rises due to other currents The temperature can also be lowered. Therefore, the components constituting the power conversion circuit can be further protected.

For temperature suppression, it is desirable to increase the frequency of the reactors 31a and 31b, and it is desirable to decrease the frequency of the switching elements 32a to 33b. For this reason, a plurality of temperature sensors may be provided to detect the temperature of one of the reactors 31a and 31b and any of the switching elements 32a to 33b. When a plurality of temperature sensors are provided in this way, the switching cycle, that is, the switching frequency may be changed according to the type of component whose detected temperature exceeds the upper limit value.

An abnormality may occur in any of the current sensors constituting the current sensor group 34. If an abnormality occurs in any of the current sensors, appropriate feedback control using the current values IL1 and IL2 becomes impossible. For this reason, when an abnormality occurs in any of the current sensors, the manipulated variable ΔD may be set to a predetermined fixed value so that the current values IL1 and IL2 are not reflected in the feedback control. By preparing two or more fixed values, for example, the fixed values may be switched depending on whether or not the instruction 1 is L. When the fixed value is switched in this way, the power conversion device 3 can be operated in both the normal situation and the discharge execution situation. When the discharge is executed, the time required for discharging the electric charge of the smoothing capacitor 36 can be shortened.

The abnormality may occur in any of the switching elements 32a to 33b. When an off failure that cannot be driven on occurs in any of the switching elements 32b and 33b that are the arms, the on / off drive of the switching element in which the off failure occurred is stopped, and the remaining switching elements excluding the failed switching element On / off drive may be performed. When such on-off drive is performed, the switching element in which the off failure occurs is used only as a diode.

The use of the switching element in which the off failure has occurred only as a diode can be realized, for example, by causing each of the two signal generators 354a and 354b to change the content of the signal generated according to the switching element in which the off failure has occurred. .. As described above, by changing the content of the generated signal according to the arm in which the off failure occurs, the power conversion device 3 can be operated even after the occurrence of the off failure. In order to prevent the control from becoming complicated, it is desirable to stop the feedback control using the current values IL1 and IL2.

Embodiment 2.
FIG. 10 is a diagram showing a configuration example of the power conversion device according to the second embodiment of the present invention. In this embodiment, two smoothing capacitors 37B and 37C are used instead of the smoothing capacitor 37. As shown in FIG. 10, the smoothing capacitor 37B is connected between one end of the reactor 31a on the battery 1 side and the negative electrode terminal of the battery 1. The smoothing capacitor 37C is connected between one end of the reactor 31b on the battery 1 side and the negative electrode terminal of the battery 1.

Even if the power conversion circuit has a configuration as shown in FIG. 10, basically, the control device 35 of the first embodiment can be used as the control device 35. By using the control device 35, the same effect as that of the first embodiment can be obtained in the present embodiment as well.

Embodiment 3.
In the first and second embodiments, the power conversion circuit includes two voltage conversion circuits. On the other hand, in the third embodiment, there are three voltage conversion circuits.

FIG. 11 is a diagram showing a configuration example of the power conversion device according to the third embodiment of the present invention. In the present embodiment, as shown in FIG. 11, a voltage conversion circuit 41 having a configuration in which switching elements 41a and 41b are connected in series is further connected between both ends of the smoothing capacitor 36. A reactor 31c is connected between the positive electrode terminal of the battery 1 and the connection point 41c between the two switching elements 41a and 41b. A current sensor 34c is added to detect the current value IL3 of the current flowing through the reactor 31c.

FIG. 12 is a diagram showing a configuration example of the power conversion control device according to the third embodiment of the present invention. In FIG. 12, a configuration example is shown by extracting a different portion from the first embodiment. That is, in the present embodiment, the control device 35 includes a first voltage control unit 355a, a second voltage control unit 355b, and a switch 356 in addition to the components shown in FIG.

In the present embodiment, as shown in FIG. 12, the current error amount generation unit 351 includes a first command value generation unit 501, a second command value generation unit 502, and a third command value generation unit 503. ..

The first command value generation unit 501 includes an arithmetic unit 511 and three subtractors 512a to 512c. The arithmetic unit 511 inputs the current values IL1 to IL3 and calculates the average value ILrefX. This average value ILrefX can be obtained by ILrefX = (IL1 + IL2 + IL3) / 3. The average value ILrefX is output to each subtractor 512a to 512c.

The subtractor 512a subtracts the current value IL1 from the average value ILrefX, and outputs the subtraction result ILerrX1 to the third command value generation unit 503. The subtractor 512b subtracts the current value IL2 from the average value ILrefX, and outputs the subtraction result ILerrX2 to the third command value generation unit 503. The subtractor 512c subtracts the current value IL3 from the average value ILrefX, and outputs the subtraction result ILerrX3 to the third command value generation unit 503.

The second command value generation unit 502 includes a drift wave generator 521. This drift wave generator 521 is mounted in place of the set value switch 351a because there are three voltage conversion circuits. The drift wave generator 521 generates and outputs the subtraction result ILERrX1 to ILERrX3 as the manipulated variable to the third command value generation unit 503.

The generation method of these values ILErrY1 to ILErrY3 differs depending on whether or not the discharge execution state, that is, the situation where the instruction 1 is H. When the instruction 1 is L, for example, the values ILErrY1 to ILErrY3 are all 0. When the instruction 1 is H, for example, the values ILErrY1 to ILErrY3 are generated as follows.
ILErrY1 = Asinωt
ILRY2 = Asin (ωt + 2π / 3)
ILErrY3 = Asin (ωt-2π / 3)
Here, A is a constant, ω is an angular velocity corresponding to the switching frequency, and t is the time elapsed since the indication 1 becomes H.

The drift wave generator 521 generates the values ILERrY1 to ILERrY3 as the drift wave value when the instruction 1 is H. The values ILERrY1 to ILERrY3 function like the set value ILset in the first embodiment. The total value of the values ILERrY1 to ILERrY3 is 0.

The third command value generation unit 503 includes three adders 531a to 531c. The adder 531a adds the value ILERrY1 to the subtraction result ILERrX1, and outputs the addition result to the current controller 352a as the difference ILERr11. Similarly, the adder 531b adds the value ILERrY2 to the subtraction result ILERrX2, and outputs the addition result as the difference ILERr12 to the current controller 352b. The adder 531c adds the value ILERrY3 to the subtraction result ILERrX3, and outputs the addition result as the difference ILERr13 to the current controller 352c.

The difference ILERr11, ILERr12, and ILERr13 are all information corresponding to the difference ILERr1 in the first embodiment. Similar to the first embodiment, the current controller 352a generates the manipulated variable ΔDa by using the difference ILR11 and outputs it to the duty generation unit 353. Similarly to the first embodiment, the current controller 352b also generates the manipulated variable ΔDb by using the difference ILERr12 and outputs it to the duty generation unit 353. Similarly to the first embodiment, the current controller 352c also generates the manipulated variable ΔDc by using the difference ILR13 and outputs it to the duty generation unit 353.

The duty generation unit 353 includes three adders 353b to 353d. The adder 353c adds the operation amount ΔDa to the duty ratio Duty input from the switch 356, and outputs the addition result to the gate signal generation unit 354 as the duty ratio Duty 32. The adder 353b adds the manipulated variable ΔDb to the duty ratio Duty, and outputs the addition result to the gate signal generation unit 354 as the duty ratio Duty 33. The adder 353d adds the manipulated variable ΔDc to the duty ratio Duty, and outputs the addition result to the gate signal generation unit 354 as the duty ratio Duty 41.

The gate signal generator 354 includes three signal generators 354a to 354c. The duty ratio Duty 32 is input to the signal generator 354a, the duty ratio Duty 33 is input to the signal generator 354b, and the duty ratio Duty 41 is input to the signal generator 354c.

The signal generator 354a generates signals Gate_32a and Gate_32b for on / off driving the two switching elements 32a and 32b constituting the voltage conversion circuit 32 according to the duty ratio Duty 32. The signals Gate_32a and Gate_32b are complementary signals to each other, and when one signal is H, the other signal is L.

The signal generator 354b generates signals Gate_33a and Gate_33b for on / off driving the two switching elements 33a and 33b constituting the voltage conversion circuit 33 according to the duty ratio Duty 33. The signals Gate_33a and Gate_33b are also complementary signals to each other.

The signal generator 354c generates signals Gate_41a and Gate_41b for on / off driving the two switching elements 41a and 41b constituting the voltage conversion circuit 41 according to the duty ratio Duty 41. The signals Gate_41a and Gate_41b are also complementary signals to each other.

FIG. 13 is a diagram illustrating an example of each signal generated by the power conversion control device according to the third embodiment of the present invention in a normal situation and a discharge execution state, respectively. In FIG. 13, the upper row shows each signal example generated in the normal situation, and the lower row shows each signal example generated in the discharge execution situation.

“Tc” in FIG. 13 represents the H time of the signal Gate_41a in a normal situation, in other words, the L time of the signal Gate_41b. Under normal circumstances, the duty ratio Duty41 = Tc / Tsw.

In this embodiment, three voltage conversion circuits 32, 33, and 41 gs are provided. As a result, as shown in FIG. 13, the phases of the signals Gate_32a and Gate_32b and the signals Gate_33a and Gate_33b are shifted by 120 degrees. Similarly, the phases of the signals Gate_33a and Gate_33b and the signals Gate_41a and Gate_41b are also shifted by 120 degrees. The phases of the signals Gate_32a and Gate_32b and the signals Gate_41a and Gate_41b are also 120 degrees out of phase.

Each signal shown in the lower part of FIG. 13 sequentially forms a closed circuit including a smoothing capacitor 36, three voltage conversion circuits 32, 33, 41, and three reactors 31a to 31c in the discharge execution state. In the closed circuit formed, two voltage conversion circuits in which the upper arm of the three voltage conversion circuits 32, 33, 41 is driven on, and the lower arm of the voltage conversion circuits 32, 33, 41 are driven on. A closed circuit formed by one voltage conversion circuit is included. In the signal example shown in FIG. 13, the arms are driven on by the voltage conversion circuits 33 and 41, and the lower arm is driven on by the remaining voltage conversion circuits 32. This closed circuit corresponds to the third closed circuit in the present embodiment.

The impedance of such a closed circuit as a whole is compared to a closed circuit containing only two of the smoothing capacitors 36, three voltage conversion circuits 32, 33, 41, and two of the three reactors 31a-31c. Becomes smaller. Therefore, in the closed circuit including the three voltage conversion circuits 32, 33, 41, the amount of current flowing per unit time is larger than that in the closed circuit including only the two voltage conversion circuits. As a result, the electric charge stored in the smoothing capacitor 36 can be discharged in a shorter time.

FIG. 14 is a diagram illustrating an example of a change in the value of the current flowing through each reactor during a discharge execution state in the power conversion device according to the third embodiment of the present invention. In a normal situation where instruction 1 is L
Since the power from the battery 1 is evenly distributed even if there are three voltage conversion circuits, the current values IL1 to IL3 of the reactors 31a to 31c are I1 / 3.

On the other hand, even in the discharge execution state in which the instruction 1 is H, the two switching elements constituting the voltage conversion circuits 32, 33, and 41 are driven on and off by signals that are out of phase by 120 degrees. As a result, the phases of the current values IL1 to IL3 are shifted by 120 degrees. Further, the current values IL1 to IL3 change with the angular velocity ω.

In the present embodiment, the number of voltage conversion circuits is three, but the number of voltage conversion circuits may be four or more. Even if the number of voltage conversion circuits is four or more, a closed circuit including the smoothing capacitor 36 and three or more voltage conversion circuits may be formed in the discharge execution state.

1 Battery (power supply), 2 Load, 3 Power converter, 10 Contactor, 31 Reactor group, 31a to 31c Reactor, 32, 33, 41 Voltage conversion circuit, 32a, 32b, 33a, 33b, 41a, 41b Switching element, 34 Current sensor group, 34a to 34c current sensor, 35 control device (power conversion control device), 36 smoothing capacitor, 37, 37B, 37C smoothing capacitor, 38 voltage sensor, 39 voltage sensor, 351 current error amount generator, 352, 352a ~ 352c Current controller, 353 duty generator, 354 gate signal generator, 354a to 354c signal generator, 355a first voltage control unit, 355b second voltage control unit, 356 switcher.

In mode 1, as shown in FIG. 4, a closed circuit including the smoothing capacitor 36, that is, a smoothing capacitor 36 → switching element 32b → reactor 31a → reactor 31b → switching element 33a → smoothing capacitor 36 is discharged from the smoothing capacitor 36. A closed circuit through which current flows is formed. By this closed circuit, in mode 1, the electric charge stored in the smoothing capacitor 36 can be directly discharged and the energy can be transferred to the reactors 3 1 a and 3 1 b.

Claims (11)

A smoothing capacitor connected in parallel with the load,
A plurality of voltage conversion circuits including two switching elements connected in parallel with the smoothing capacitor and connected in series as an upper arm and a lower arm, respectively.
A reactor group including a reactor having one end connected to a power supply and the other end connected between the two switching elements constituting one of the plurality of voltage conversion circuits.
When the electric charge stored in the smoothing capacitor is discharged, the smoothing capacitor, the two or more reactors constituting the reactor group, and the plurality of reactors are driven by on / off driving of each switching element constituting the plurality of voltage conversion circuits. A first closed circuit including two or more voltage conversion circuits constituting the voltage conversion circuit, two or more reactors constituting the reactor group, and two or more voltages constituting the plurality of voltage conversion circuits. A control unit that includes each upper arm or each lower arm of the conversion circuit and forms a second closed circuit that does not include the smoothing capacitor.
A power converter equipped with. The reactors are magnetically coupled,
The power conversion device according to claim 1. A voltage sensor that detects the voltage value between both ends of the smoothing capacitor,
Further, a plurality of current sensors for detecting the current value of each reactor constituting the reactor group are provided.
The control unit
Using the voltage value detected by the voltage sensor, a first condition setting unit for determining a first drive condition for on / off driving each of the switching elements constituting the plurality of voltage conversion circuits, and a first condition setting unit.
Using the current value detected by each of the plurality of current sensors, a change amount determining unit for determining the change amount with respect to the first driving condition, and a change amount determining unit.
A second condition setting unit that sets a second drive condition, which is a drive condition after changing the first drive condition, using the change amount.
A signal generation unit that generates a signal for on / off driving the switching elements constituting the plurality of voltage conversion circuits according to the second drive condition set by the second condition setting unit.
The power conversion device according to claim 1 or 2. With other smoothing capacitors connected in parallel with the power supply,
Further provided with another voltage sensor for detecting the voltage value between both ends of the other smoothing capacitor.
The control unit
Using the voltage value detected by the other voltage sensor, a third condition setting unit for determining a third drive condition for on / off driving each of the switching elements constituting the plurality of voltage conversion circuits, and a third condition setting unit.
A selection unit for selecting one of the first drive condition set by the first condition setting unit and the third drive condition set by the third condition setting unit is further provided.
The second condition setting unit changes one of the first drive condition and the third drive condition selected by the selection unit using the change amount, and changes the second drive condition. To set,
The power conversion device according to claim 3. The selection unit selects the third driving condition when discharging the electric charge stored in the smoothing capacitor.
The power conversion device according to claim 4. Further comprising at least one reactor constituting the reactor group, at least one switching element constituting the plurality of power conversion circuits, and a temperature sensor for detecting the temperature of any one of the smoothing capacitors.
When the temperature detected by the temperature sensor exceeds the upper limit value determined by the temperature sensor in a situation where the electric charge stored in the smoothing capacitor is discharged, the control unit constitutes each of the switching elements constituting the plurality of power conversion circuits. Change the switching cycle for driving on / off,
The power conversion device according to any one of claims 1 to 5. Further comprising at least one reactor constituting the reactor group, at least one switching element constituting the plurality of power conversion circuits, and a temperature sensor for detecting the temperature of any one of the smoothing capacitors.
When the temperature detected by the temperature sensor exceeds the upper limit value set by the control unit in a situation where the electric charge stored in the smoothing capacitor is discharged, the unit time flows through the first and second closed circuits. The amount of current per hit is lowered compared to before the temperature exceeds the upper limit.
The power conversion device according to any one of claims 1 to 5. When an abnormality occurs in one of the plurality of current sensors, the control unit is subjected to the change amount determination unit that reflects the current value in a situation where the electric charge stored in the smoothing capacitor is discharged. Stop determining the amount of change,
The power conversion device according to claim 3. When an abnormality occurs in which one switching element constituting the plurality of power conversion circuits is not driven on when the charge stored in the smoothing capacitor is discharged, the control unit causes the switching element in which the abnormality has occurred. Drives the switching elements on and off, except
The power conversion device according to any one of claims 1 to 8. When the plurality of voltage conversion circuits are three or more voltage conversion circuits,
When the charge stored in the smoothing capacitor is discharged, the control unit can be used as the smoothing capacitor and the upper arm or the lower arm by on / off driving of each switching element constituting the three or more voltage conversion circuits. A third closed circuit containing at least two voltage conversion circuits in which the switching element used is driven on is formed.
The power conversion device according to any one of claims 1 to 9. A smoothing capacitor connected in parallel to the load, a plurality of voltage conversion circuits including two switching elements connected in parallel with the smoothing capacitor and connected in series as an upper arm and a lower arm, and one end is a power supply. A power conversion circuit having a reactor group including a reactor connected to the other end and connected between the two switching elements constituting one of the plurality of voltage conversion circuits, and stored in the smoothing capacitor. In the case of discharging the charged charge, the switching elements constituting the plurality of voltage conversion circuits are driven on and off, and the smoothing capacitor, the two or more reactors constituting the reactor group, and the plurality of voltage conversion circuits are formed. On each of a first closed circuit including two or more voltage conversion circuits constituting the same, two or more reactors constituting the reactor group, and two or more voltage conversion circuits constituting the plurality of voltage conversion circuits. Performing a process of forming a second closed circuit that includes an arm or each lower arm and does not include the smoothing capacitor.
Power conversion control device.

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