JP2012157145A - Bidirectional converter, control circuit thereof, and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsibility of a bidirectional converter at the time when switching is made between charging and discharging of an electric power storage device.SOLUTION: A target voltage setting part 101 sets a target voltage Vwhich represents a target voltage of a load device. A voltage PI control part 103 acquires a target current Irepresenting a target current that flows during charging and discharging of the electric power storage device by PI control which is based on a difference between the set target voltage Vand a voltage Vof the load device. A current PI control part 106 acquires a corrective voltage ΔV by PI control which is based on a difference between the target current Iand a current Ithat flows during charging and discharging of the electric power storage device. A duty ratio deciding part 110 acquires a duty ratio that specifies a degree of conversion between a voltage of the electric power storage device and a voltage of the load device according to the correction voltage ΔV. A voltage conversion part steps up or steps down the voltage according to the acquired duty ratio, for conversion between the voltage of the electric power storage device and the voltage of the load device.

Description

  The present invention relates to a bidirectional converter that is placed between an electric power storage device and a load device and converts the magnitude of a DC voltage, its control circuit, and its control method.

For example, in a hybrid vehicle or a train, the electric power of the electric power storage device is supplied to the motor during power running operation, while the motor functions as a generator during the regenerative operation, and the electric power output from the motor is supplied to the electric power storage device.
In such a vehicle or the like, the voltage of the electric power storage device is boosted and applied to the motor in order to increase the driving force of the motor. Further, the voltage generated by the motor is stepped down and applied to the electric power storage device to charge the electric power storage device. For this reason, a bidirectional converter for converting the voltage is provided between the electric power storage device and the load device including the motor.

As a control method of such a bidirectional converter, Patent Document 1 performs PI (proportional / integral) control so that the difference between the target voltage and the voltage on the load device side is reduced, and both the boost operation and the step-down operation are not distinguished. Disclosed is a method for PWM (Pulse Width Modulation) control of two switching elements included in a directional converter.
Further, Patent Document 2 performs PI control so that the difference between the target voltage and the voltage on the load device side is reduced, and among the two switching elements included in the bidirectional converter, the switching element for boosting is PWMed during boosting. Disclosed is a method of controlling and PWM controlling a step-up switching element during step-down.

  Here, the direction of the current flowing from the electrical storage device to the load device is positive, and the direction of the current flowing from the load device to the electrical storage device is negative. That is, it is defined that a negative current flows during regenerative operation and a positive current flows during power running operation.

JP 2010-115056 A JP 2009-303423 A

In the bidirectional converter using the control method disclosed in Patent Document 1, when the motor stops the function of the generator and starts to be driven by the voltage of the electric power storage device, the current flowing between the electric power storage device and the load device When the current I _A is viewed macroscopically, the current I _A changes from negative to positive through zero and switches from charging to discharging of the electric power storage device.
In this case, ideally, the current I _A when viewed macroscopically linearly changed, the state current value thereof is 0 only occur instantaneously. However, in practice, the response of the bi-directional converter is deteriorated, the value of the current I _A phenomenon occurs sticking around 0. When this occurs, the value of the current I _A does not easily increase, the actual current I _A is smaller than the ideal current I _A. Then, after the value of the current I _A is followed by a long time the state of stagnant near 0, the normal boosting operation is ready, the value of the current I _A is momentarily increased, the surge is generated.

  In the bidirectional converter using the control method disclosed in Patent Document 2, the current response is delayed in a region where the current close to the switching point between the step-up operation and the step-down operation is small. A dead zone area that cannot be performed appears. For this reason, in the invention described in Patent Document 2, it is determined whether or not it is in the dead zone region, and if it is in the dead zone region, the proportional gain and integral gain of PI control are increased to improve the responsiveness.

  The present invention has been made in view of the above-described circumstances, and can be controlled without distinction between a step-up operation and a step-down operation, and both can improve responsiveness when charging and discharging of an electric power storage device are switched. An object of the present invention is to provide a direction converter, a control circuit thereof, and a control method thereof.

In order to achieve the above object, the bidirectional converter of the present invention comprises:
A bi-directional converter for converting the voltage of the electrical storage device and the voltage of the load device between the electrical storage device capable of charging and discharging and a load device capable of transferring DC power,
A voltage conversion unit that converts the voltage of the electric power storage device and the voltage of the load device according to a duty ratio that specifies a degree of voltage conversion;
Based on the difference between the target voltage indicating the voltage target of the load device and the voltage of the load device, a target current indicating the target of the current that flows during charging and discharging of the electric power storage device is obtained, and the target current and the electric power A control unit for obtaining the duty ratio based on a difference between a current flowing during charging and discharging of the power storage device;
Is provided.

Preferably, the bidirectional converter of the present invention comprises:
The voltage conversion unit includes a coil that generates a voltage at both ends due to a current flowing when the electric power storage device is charged and discharged.
The control unit is
Obtaining the target current by PI control based on the difference between the target voltage and the voltage of the load device;
A correction voltage is obtained by PI control based on a difference between the target current and a current flowing during charging and discharging of the electric power storage device,
The duty ratio is obtained based on the voltage of the electric power storage device, the voltage generated at both ends of the coil, and the correction voltage.

Preferably, the bidirectional converter of the present invention comprises:
The voltage converter is
A negative electrode line connected to both the electric power storage device and the load device;
A first positive electrode line connected to the electric power storage device and one end of the coil;
A second positive line connected to the load device;
A gate signal generation unit that generates a first gate signal and a second gate signal based on the duty ratio;
A first conductive path having one end connected to the second positive electrode line and the other end connected to the other end of the coil, the conduction and non-conduction of which are controlled by the first gate signal; A first element having a second conductive path that allows current to flow only in a direction from the other end of the one conductive path toward the one end;
One end connected to the other end of the conductive path of the first element, the other end connected to the negative electrode line, and a third conductive path whose conduction and non-conduction are controlled by the second gate signal; A second element having a fourth conductive path that allows current to flow only in a direction from the other end of the third conductive path toward the one end;
With
The control unit is
A target voltage setting unit for setting the target voltage;
A target current determination unit that obtains a difference between the target voltage set by the target voltage setting unit and the voltage of the load device, and obtains the target current by PI control based on the difference;
A correction voltage determining unit that calculates a difference between the target current determined by the target current determining unit and a current that flows when the electric power storage device is charged and discharged, and calculates the correction voltage by PI control based on the difference;
A coil voltage acquisition unit for obtaining a voltage generated at both ends of the coil based on a current flowing during charging and discharging of the electric power storage device;
A voltage for obtaining a voltage corresponding to a duty ratio based on the correction voltage obtained by the correction voltage determination unit, the voltage generated at both ends of the coil obtained by the coil voltage acquisition unit, and the voltage of the electric power storage device A decision unit;
A duty ratio determining unit for determining the duty ratio based on a voltage corresponding to the duty ratio determined by the voltage determining unit and a voltage of the load device;
Is provided.

Preferably, the bidirectional converter of the present invention comprises:
The control unit is
A storage unit storing a current limit value of a current flowing during charging and a current limit value of a current flowing during discharging according to the charge / discharge characteristics of the electric power storage device,
When the electric power storage device is charged or discharged, when the target current value exceeds the current limit value stored in the storage unit, the current limit value stored in the storage unit Limiter to replace with
Is provided.

Preferably, the bidirectional converter of the present invention comprises:
The load device includes a motor that functions as a generator,
The limiter of the control unit, when the value of the target current exceeds the current limit value of the output current of the motor determined based on the current limit value of the current that flows when charging the electric power storage device, the value of the target current Is replaced with a current limit value of the output current of the motor,
The bidirectional converter according to claim 4.

The control circuit of the bidirectional converter of the present invention is
The voltage of the electric power storage device and the voltage of the load device are between the electric power storage device capable of charging and discharging and the load device capable of transferring DC power, and the voltage of the electric power storage device according to the duty ratio that specifies the degree of voltage conversion A bidirectional converter control circuit comprising a voltage converter for converting
Based on the difference between the target voltage indicating the voltage target of the load device and the voltage of the load device, a target current indicating the target of the current that flows during charging and discharging of the electric power storage device is obtained, and the target current and the electric power The duty ratio is obtained based on the difference between the current flowing when the power storage device is charged and discharged.

Further, the bidirectional converter control method of the present invention includes:
The voltage of the electric power storage device and the voltage of the load device are between the electric power storage device capable of charging and discharging and the load device capable of transferring DC power, and the voltage of the electric power storage device according to the duty ratio that specifies the degree of voltage conversion A bidirectional converter control method including a voltage conversion unit for converting
Obtaining a target current indicating a target of a current flowing during charging and discharging of the electric power storage device based on a difference between a target voltage indicating a target voltage of the load device and a voltage of the load device;
Obtaining the duty ratio based on a difference between the target current and a current flowing when the electric power storage device is charged and discharged;
Is provided.

  According to the present invention, the step-up operation and the step-down operation can be controlled without distinction, and the responsiveness of the bidirectional converter when the charging and discharging of the electric power storage device is switched can be improved.

It is a figure which shows an example of a structure of the power supply system containing the bidirectional | two-way converter which concerns on embodiment of this invention. It is a figure which shows an example of the waveform of the gate reference signal GBS used as the reference | standard of the gate signal G1 and the gate signal G2, the gate signal G1, and the gate signal G2. It is a figure which shows an example of the change of the electric current which flows through a coil. It is a figure which shows an example of a structure of a PWM control circuit. It is a figure which shows an example of the flow of the PWM control process in a PWM control program.

  Hereinafter, a bidirectional converter according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the configuration of a power supply system including a bidirectional converter 10 according to an embodiment of the present invention.
This power supply system includes a bidirectional converter 10, an electric power storage device 20, and a smoothing capacitor 30.
Bidirectional converter 10 is arranged between electric power storage device 20 and load device 40. The bidirectional converter 10 boosts the voltage of the electric power storage device 20 to the voltage of the load device 40 when the electric power storage device 20 is discharged, and supplies the voltage of the load device 40 to the electric power when the electric power storage device 20 is charged. The voltage is stepped down to the voltage of the power storage device 20.
Electric power storage device 20 has a positive electrode terminal and a negative electrode terminal connected to positive electrode line PL1 and negative electrode line NL, respectively. The electric power storage device 20 is a DC power source that can be charged and discharged, and includes, for example, a secondary battery such as nickel hydride or lithium ion, a large-capacity capacitor, and the like. Voltage V _B of electric power storage device 20 is a DC voltage between positive line PL1 and negative line NL.
Smoothing capacitor 30 is connected in parallel with load device 40 between positive electrode line PL2 and negative electrode line NL. The smoothing capacitor 30 smoothes the voltage _VDC of the load device 40.
Load device 40 has a positive terminal and a negative terminal connected to positive line PL2 and negative line NL, respectively. The load device 40 includes, for example, a motor that functions as a generator. The voltage V _DC of the load device 40 is a DC voltage between the positive electrode line PL2 and the negative electrode line NL.

For example, when a motor included in the load device 40 functions as an electric motor driven by the voltage of the electric power storage device 20, the electric power storage device 20 is discharged and power is supplied from the electric power storage device 20 to the load device 40. At this time, it flows through a positive current I _A toward the electric power storage device 20 to the load device 40.
On the other hand, for example, when a motor included in the load device 40 functions as a generator, electric power is supplied from the load device 40 to the electric power storage device 20, and the electric power storage device 20 is charged. At this time, a negative current I _A flows from the load device 40 to the electric power storage device 20.

Bidirectional converter 10 includes a switching element 11, a switching element 12, a diode 13, a diode 14, a coil 15, a gate signal generation unit 16, and a PWM control circuit 100 described later.
In the present embodiment, it is assumed that the switching element 11 and the switching element 12 are configured by IGBT (Insulated Gate Bipolar Transistor). However, the switching element 11 and the switching element 12 can also be comprised by other switching elements, such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a bipolar transistor.

Switching element 11 and switching element 12 are connected in series between positive electrode line PL2 and negative electrode line NL. A gate signal G 1 and a gate signal G 2 are input to the gates of the switching element 11 and the switching element 12. The gate signal G1 and the gate signal G2 are examples of the first gate signal and the second gate signal, respectively.
Switching element 11 has a collector connected to positive line PL <b> 2 and an emitter connected to the collector of switching element 12. The switching element 11 has a conductive path whose conduction and non-conduction are controlled by the gate signal G1 between the collector and the emitter. The collector and the emitter are examples of one end and the other end of the conductive path of the switching element 11, respectively.
Switching element 12 has a collector connected to the emitter of switching element 11 and a collector connected to negative electrode line NL2. The switching element 12 has a conductive path whose conduction and non-conduction are controlled by the gate signal G2 between the collector and the emitter. The collector and the emitter are examples of one end and the other end of the conductive path of the switching element 12, respectively.

The diode 13 has an anode and a cathode connected to the emitter and collector of the switching element 11, respectively. The diode 13 flows current only in the direction from the emitter to the collector of the switching element 11. The diode 14 has an anode and a cathode connected to the emitter and collector of the switching element 12, respectively. The diode 14 allows current to flow only in the direction from the emitter to the collector of the switching element 12.
The diode 13 and the diode 14 may be integrated in the switching element 11 and the switching element 12, respectively, or the switching element 11 and the switching element 12 may be separately attached. Good.

One end of coil 15 is connected to positive electrode line PL1, and the other end is connected to connection node ND to which the emitter of switching element 11 and the collector of switching element 12 are connected. Voltage V _e of the connection node ND is the voltage between the other end and a negative electrode line NL of the coil 15.
The current I _A (I _L ) flows from the electric power storage device 20 toward the load device 40 when the electric power storage device 20 is discharged, and flows from the load device 40 toward the electric power storage device 20 when the electric power storage device 20 is charged. However, this current I _A (I _L ) is also a current flowing through the coil 15. When the current I _A (I _L ) flows, a voltage V _L is generated at both ends of the coil 15. Here, as described with reference to FIG. 3 below, the current I _L is the current actually flowing through the coil 15, the current I _A is the current flowing in the coil 15 when viewed macroscopically.

The PWM control circuit 100 (see FIG. 4) described later generates a duty ratio α that specifies the degree of conversion between the voltage of the electric power storage device and the voltage of the load device, and sends the duty ratio α to the gate signal generation unit 16. The gate signal generator 16 generates a gate signal G1 and a gate signal G2 according to the received signal indicating the duty ratio α.
FIG. 2 shows an example of the waveforms of the gate reference signal GBS, the gate signal G1, and the gate signal G2, which serve as a reference for the gate signal G1 and the gate signal G2.
When the period of the gate reference signal GBS is T and the period during which the potential level is high is Th, the duty ratio of the gate reference signal GBS is defined as Th / T. The gate signal generation unit 16 generates the gate reference signal GBS so that the duty ratio of the gate reference signal GBS matches the duty ratio α transmitted from the PWM control circuit 100.
Then, the gate signal generation unit 16 generates the gate signal G1 so that the gate signal G1 rises with a delay by the dead time d1 from the rise of the gate reference signal GBS, and the gate reference signal GBS falls and falls. Further, the gate signal generation unit 16 generates the gate signal G2 such that it rises with a delay of the dead time d2 from the fall of the gate reference signal GBS and falls as the gate reference signal GBS rises.

The gate signal G1 is supplied to the gate of the switching element 11. The switching element 11 is turned on (conductive) during a period when the potential level of the gate signal G1 is high, and the switching element 11 is turned off (non-conductive) while the potential level of the gate signal G1 is low.
The gate signal G2 is supplied to the gate of the switching element 12. The switching element 12 is turned on (conductive) during the period when the potential level of the gate signal G2 is high, and the switching element 12 is turned off (non-conductive) while the potential level of the gate signal G2 is low.
During the period of dead time d1 and dead time d2, both switching element 11 and switching element 12 are turned off. As a result, switching element 11 and switching element 12 are simultaneously turned on (conducted) to prevent short circuit between positive electrode line PL2 and negative electrode line NL.

When the duty ratio α decreases, the period during which the switching element 12 is on increases. At this time, the current I _A flowing through the coil 15 when viewed macroscopically increases in the positive direction.
For example, in a hybrid vehicle or the like, when the driver is stepping on the brake, the electric power storage device 20 is charged. At this time, if the driver releases the brake and steps on the accelerator, the PWM control circuit 100 decreases the duty ratio α in order to flow current to the load device 40 side. When the duty ratio α is small, as shown in FIG. 3, actually current I _L flowing through the coil is cyclically repeatedly increases and decreases in accordance with the period of the gate the reference signal GBS, but the coil 15 when viewed macroscopically current I _a flowing is the first negative, positive changes from negative at time t0 gradually increased to.

Conversely, when the duty ratio α increases, the period during which the switching element 11 is on becomes longer. At this time, the current I _A flowing through the coil 15 when viewed macroscopically increases (that is, decreases) in the negative direction.
Incidentally, when the current _{I A} is negative, the current _{I A} flows toward the electric power storage device 20 from the load device 40. On the other hand, when the current _{I A} is positive, the current _{I A} flows toward the electric power storage device 20 to the load device 40.

FIG. 4 shows an example of the configuration of the PWM control circuit 100.
The PWM control circuit 100 includes a target voltage setting unit 101, a subtractor 102, a voltage PI control unit 103, a limiter 104, a subtractor 105, a current PI control unit 106, a coil voltage acquisition unit 107, and an adder. 108, a subtractor 109, and a duty ratio determination unit 110.

Two voltage sensors (not shown) detect the voltage V _B of the electric power storage device 20 and the voltage V _DC of the load device 40, respectively, and send the detected values to the PWM control circuit 100.
Further, to detect the current I _L flowing through the actual coil 15 is a current sensor (not shown), and sends the detected value to the PWM control circuit 100. PWM control circuit 100 determines the current _{I A} when viewed macroscopically. At this time, PWM control circuit 100 may be determine the current I _A by sampling once current I _L for each cycle of the gate the reference signal GBS, sampled multiple times in each cycle of the gate the reference signal GBS and it may be obtained current I _a by averaging them.

The target voltage setting unit 101 sets a target voltage V ^* _DC indicating a target of the voltage V _DC of the load device 40 based on, for example, the torque and rotation speed of the motor included in the load device 40, the remaining capacity of the electric power storage device 20, and the like. Obtained and sent to the subtractor 102.
The subtractor 102 obtains a difference ε _V between the target voltage V ^* _DC and the voltage V _DC of the load device 40 using a voltage sensor as shown in the following equation (1), and sends the difference ε _V to the voltage PI control unit 103.

Voltage PI control unit 103, as shown in the following equation (2), determine the target current I ^* indicating the target of the current flowing in the coil 15 by performing a PI (proportional-integral) control based on the difference epsilon _V, Send to limiter 104. Here, K _Pi and K _li are generally constants, but may be variables.

Limiter 104, an excessive current I _A flows, in order to prevent damaging the power supply system or the like, the value of the target current I ^* is limited to fall within a predetermined range.
Furthermore, the charge / discharge management of the electric power storage device 20 can be controlled by the target current I ^* . For example, the current limiting value of charging / discharging of the electric power storage device 20 according to the voltage and current charging / discharging characteristics of the electric power storage device 20 (that is, the current limiting value of the current flowing during charging and the current limiting value of the current flowing during discharging) The information is stored in advance in a storage unit (not shown) provided in the PWM control circuit 100 including a ROM (Read Only Memory), a flash memory, and the like. When the value of the target current I ^* exceeds the stored current limit value at the time of charging or discharging, the limiter 104 replaces the value of the target current I ^* with the stored current limit value. Control of charge / discharge management can be performed simultaneously.

  Further, when the motor included in the load device 40 functions as a generator, the current limit value of the output current of the motor that is the load is set in conjunction with the current limit value of the current that flows when the electric power storage device 20 is charged. It is also possible. For example, on the principle of power invariance, the current limit value of the motor output current can be calculated from the current limit value of the current that flows when the electric power storage device 20 is charged. When the load device 40 drives the induction motor with an inverter, there is a relationship of the following equation (3).

Here, V _B is the voltage of the electric power storage device 20, I _{A_lim} is the current limit value of the current that flows when the electric power storage device 20 is charged, V _m is the voltage of the induction motor, and I _{m_lim1} is the voltage of the induction motor. The output current limit value, COSφ, is the power factor of the induction motor.
When the load device is a direct current motor, there is a relationship of the following equation (4).

Here, _VDC is the voltage of the load device 40, that is, the voltage of the DC motor, and _{Im_lim2} is the current limit value of the output current of the DC motor.
Therefore, the current limit values I _{m_lim1} and I _{m_lim2} of the motor output current can be calculated by the above formula (3) or (4). When the value of the target current I ^* exceeds the current limit value of the motor output current, the limiter 104 protects the load device 40 and the motor by replacing the value of the target current I ^* with the current limit value of the motor output current. be able to.
When calculating the current limit value of the current flowing when charging the electric power storage device 20 and the current limit value of the motor output current, the current limit value of the motor output current is set slightly smaller in consideration of errors. It is desirable to do.

Subtractor 105, as shown in the following equation (5), obtains a difference epsilon _A between the current _{I A} flowing through the target current ^{I *} and the coil 15, and sends the current PI control unit 106.

The current PI control unit 106 performs PI control based on the difference ε _A as shown in the following equation (6), obtains a correction voltage ΔV, and sends it to the subtractor 109. Here, K _Pv and K _lv are generally constants, but may be variables.

Coil voltage acquiring unit 107, as shown in the following equation (7), obtains the voltage _{V L} generated across the coil 15 by flowing through the coil 15 a current _{I A,} and sends to the adder 108. Here, L is the inductance value of the coil 15, T is the period of the gate reference signal GBS, I _A (t) is the current I _A flowing through the coil 15 at time t, and I _A (t−T) is the time (t−T). ), that is, the current _{I a} flowing through the coil 15 in one period T before the time t.

As shown in the following equation (8), the adder 108 adds the voltage V _B of the electric power storage device 20 and the voltage V _L generated at both ends of the coil 15 to obtain the voltage Ve and sends the voltage _Ve to the subtractor 109.

Subtractor 109, as shown in the following equation (9), by subtracting the correction voltage ΔV obtained by the above equation (6) from the voltage V _e, obtains the voltage V _pwm corresponding to the duty ratio, the duty ratio determining Send to part 110.

As shown in the following equation (10), the duty ratio determination unit 110 divides the voltage V _pwm corresponding to the duty ratio by the voltage V _DC of the load device to obtain the duty ratio α. Then, the duty ratio determination unit 110 sends the duty ratio α to the gate signal generation unit 16.

  Each function of the PWM control circuit 100 can be realized not by hardware but by a computer or a DSP (Digital Signal Processor). In this case, each function of the PWM control circuit 100 is realized by executing a PWM control program stored in the storage device by a CPU (Central Processing Unit) of a computer or a DSP (hereinafter referred to as a computer or the like).

FIG. 5 shows an example of the flow of PWM control processing in the PWM control program.
Voltage V _B of the electric power storage device 20 detected by the two voltage sensors (not shown) and one current _sensor, a current I _L flowing through the voltage V _DC and the coil 15 of the load device 40 is sampled at a predetermined period. These are A / D (Analog-to-Digital) converted and input from an input device to a computer or the like. At this time, in order to remove electromagnetic noise, the numerical value obtained by A / D converting the voltage V _B of the electric power storage device 20 and the voltage V _DC of the load device 40 is obtained by a low pass filter LPF (Low Pass Filter) or a moving average. A smoothing process can also be performed.
In the following, the voltage _{V B} of the electric power storage device 20 which is converted into a digital signal, the voltage _{V B} of the voltage _{V DC} and the coil 15 respectively electrically power storage device current _{I L} flowing through 20 of the load device 40, the load device 40 voltage V _DC and that measurements of the current _{I L} flowing through the coil 15.

The CPU obtains a difference ε _V between the target value V ^* _{DC of} the load device voltage and the measured value of the load device voltage V _DC measured by the voltage sensor (S101), and performs PI control based on the difference ε _V. The target value I ^{* of the} current flowing through the coil is obtained (S102). Then, the CPU limits the current target value I ^* so that it falls within a predetermined range (S103).
The CPU obtains a difference ε _A between the target value I ^* of the current and the measured value of the current I _A flowing through the coil (S104), and performs a PI control based on the difference ε _A to obtain a correction value ΔV for obtaining the duty ratio α. Obtained (S105).

The CPU obtains the voltage _{V L} generated across the coil 15 by flowing through the coil 15 a current _{I A} (S106). Then, CPU obtains the voltage _{V e} by adding the voltage _{V B} of the electric power storage device 20 to the voltage _{V L,} the voltage V corresponding to the duty ratio by subtracting the correction value ΔV calculated in step S106 from the voltage _{V e pwm} is obtained (S107).
The CPU divides the voltage V _pwm according to the duty ratio by the voltage V _DC of the load device to obtain the duty ratio α (S108). Then, the CPU sends the obtained duty ratio α to the gate signal generation unit 16.

As shown in the above-described embodiment, the voltage V _pwm corresponding to the duty ratio is obtained by adding the voltage V _B of the electric power storage device 20 and the voltage _VL generated at both ends of the coil 15 as shown in the above equation (9). Further, it is obtained by subtracting the correction voltage ΔV.
Here, the change of the current I _A flowing through the coil 15 as can be seen from equation (7) becomes smaller, the voltage V _L becomes small. Therefore, when the value of the current _{I A} is stagnant in the vicinity of 0, the voltage _{V L} becomes small.
Further, when the value of the current I _A is stagnant in the vicinity of 0, the difference epsilon _A current I _A flowing through the target value I ^* and the coil 15 of the current represented by the equation (5) becomes larger. When the difference epsilon _A increases, the correction voltage ΔV represented by the above equation (6) is increased.

Thus, current when the value of I _A stagnates near 0, the voltage V _L becomes small, the correction voltage ΔV is increased, the voltage V _pwm corresponding to the duty ratio represented by the equation (7) becomes smaller.
Since the duty ratio α is a value obtained by dividing the voltage V _pwm corresponding to the duty ratio by the voltage V _DC of the load device as shown in the above equation (8), at this time, the duty ratio α becomes small.
As the duty ratio α decreases, the current I _A flowing through the coil 15 increases.

Thus, PWM control circuit 100, the value of the current _{I A} is stagnant in the vicinity of 0, increasing the current _{I A} flowing through the coil 15. Therefore, even as a phenomenon that if sticking around value 0 of the current I _A occurs, the phenomenon is eliminated early.

As described above, according to the present invention, it obtains a target current I ^* of the value of the current I _A flowing through the coil 15 voltage V _DC of the load device 40 is controlled to be the target voltage V ^* _DC, further by current I _a flowing through the coil 15 is controlled to be the target current I ^*, it can be controlled without distinguishing between the boost operation and the buck operation, bidirectional in when switching the charging and discharging of electric power storage device The responsiveness of the converter 10 can be improved.
According to the present invention, even as a phenomenon in which the value of the current I _A flowing or phenomenon that the value of the current I _A flowing through the coil 15 from sticking in the vicinity of 0 is eliminated, or if the coil 15 is stuck around 0 occur, the phenomenon Is eliminated at an early stage, so that the response of the bidirectional converter is improved. For this reason, the capacity | capacitance of the smoothing capacitor connected in parallel with a load apparatus can be made small.
Further, according to the present invention, if for the phenomenon that the value of the current I _A flowing through the coil 15 from sticking in the vicinity of 0 even though occurs, the phenomenon is eliminated early, the power supply system described in Patent Document 1 Unlike, when the end of the state where the current I _a is stuck in the vicinity of 0, the current I _a increases rapidly, does not surge occurs.

Incidentally, PWM control circuit 100, a voltage control for controlling so that the voltage _{V DC} of the load device 40 described above becomes the target voltage ^V _{* DC,} and a current _{I A} is the current control for controlling so that the target current ^{I *} to carry out every once or every plurality of sampling periods, such as the current I _L of the coil 15 (tens of .mu.sec hundred .mu.sec), response of the bi-directional converter 10 is quickly. Thus, the capacity | capacitance of the smoothing capacitor | condenser connected in parallel with a load apparatus can also be made small by responsiveness becoming quick.
Furthermore, if the sampling period is shortened according to the calculation speed of the PWM control circuit 100 realized by a DSP or the like, the inductance value L of the coil 15 can be reduced. In that case, the switching sound of the bidirectional converter 10 can also be reduced as an accompanying effect.

While the embodiments of the present invention have been described above, various modifications and combinations required for design reasons and other factors are included in the scope of the present invention.
The present invention is not limited to a vehicle that performs power running operation and regenerative operation such as a hybrid vehicle or a train, but is a system that converts the magnitude of a DC voltage between an electric power storage device and a load device, and the electric power storage device The present invention can be applied to a system in which a current flows from the load device toward the electric power storage device during charging, and a current flows from the electric power storage device toward the load device when the electric power storage device is discharged.

DESCRIPTION OF SYMBOLS 10 ... Bidirectional converter, 11 ... Switching element, 12 ... Switching element, 13, 14 ... Diode, 15 ... Coil, 16 ... Gate signal production | generation part, 20 ... Electric power storage device, 30 ... Smoothing capacitor, 40 ... Load device, DESCRIPTION OF SYMBOLS 100 ... PWM control circuit 101 ... Target voltage setting part 102, 105, 109 ... Subtractor 103 ... Voltage PI control part 104 ... Limiter 106 ... Current PI control part 107 ... Coil voltage acquisition part 108 ... Addition 110, duty ratio determining unit

Claims (7)

A bi-directional converter for converting the voltage of the electrical storage device and the voltage of the load device between the electrical storage device capable of charging and discharging and a load device capable of transferring DC power,
A voltage conversion unit that converts the voltage of the electric power storage device and the voltage of the load device according to a duty ratio that specifies a degree of voltage conversion;
Based on the difference between the target voltage indicating the voltage target of the load device and the voltage of the load device, a target current indicating the target of the current that flows during charging and discharging of the electric power storage device is obtained, and the target current and the electric power A control unit for obtaining the duty ratio based on a difference between a current flowing during charging and discharging of the power storage device;
A bidirectional converter characterized by comprising: The voltage conversion unit includes a coil that generates a voltage at both ends due to a current flowing when the electric power storage device is charged and discharged.
The control unit is
Obtaining the target current by PI control based on the difference between the target voltage and the voltage of the load device;
A correction voltage is obtained by PI control based on a difference between the target current and a current flowing during charging and discharging of the electric power storage device,
Obtaining the duty ratio based on the voltage of the electric power storage device, the voltage generated at both ends of the coil, and the correction voltage;
The bidirectional converter according to claim 1. The voltage converter is
A negative electrode line connected to both the electric power storage device and the load device;
A first positive electrode line connected to the electric power storage device and one end of the coil;
A second positive line connected to the load device;
A gate signal generation unit that generates a first gate signal and a second gate signal based on the duty ratio;
A first conductive path having one end connected to the second positive electrode line and the other end connected to the other end of the coil, the conduction and non-conduction of which are controlled by the first gate signal; A first element having a second conductive path that allows current to flow only in a direction from the other end of the one conductive path toward the one end;
One end connected to the other end of the conductive path of the first element, the other end connected to the negative electrode line, and a third conductive path whose conduction and non-conduction are controlled by the second gate signal; A second element having a fourth conductive path that allows current to flow only in a direction from the other end of the third conductive path toward the one end;
With
The control unit is
A target voltage setting unit for setting the target voltage;
A target current determination unit that obtains a difference between the target voltage set by the target voltage setting unit and the voltage of the load device, and obtains the target current by PI control based on the difference;
A correction voltage determining unit that calculates a difference between the target current determined by the target current determining unit and a current that flows when the electric power storage device is charged and discharged, and calculates the correction voltage by PI control based on the difference;
A coil voltage acquisition unit for obtaining a voltage generated at both ends of the coil based on a current flowing during charging and discharging of the electric power storage device;
A voltage for obtaining a voltage corresponding to a duty ratio based on the correction voltage obtained by the correction voltage determination unit, the voltage generated at both ends of the coil obtained by the coil voltage acquisition unit, and the voltage of the electric power storage device A decision unit;
A duty ratio determining unit for determining the duty ratio based on a voltage corresponding to the duty ratio determined by the voltage determining unit and a voltage of the load device;
Comprising
The bidirectional converter according to claim 2. The control unit is
A storage unit storing a current limit value of a current that flows during charging and discharging according to the charge / discharge characteristics of the electric power storage device,
When the electric power storage device is charged or discharged, when the target current value exceeds the current limit value stored in the storage unit, the current limit value stored in the storage unit Limiter to replace with
The bidirectional converter according to any one of claims 1 to 3, further comprising: The load device includes a motor that functions as a generator,
The limiter of the control unit, when the value of the target current exceeds the current limit value of the output current of the motor determined based on the current limit value of the current that flows when charging the electric power storage device, the value of the target current Is replaced with a current limit value of the output current of the motor,
The bidirectional converter according to claim 4. The voltage of the electric power storage device and the voltage of the load device are between the electric power storage device capable of charging and discharging and the load device capable of transferring DC power, and the voltage of the electric power storage device according to the duty ratio that specifies the degree of voltage conversion A bidirectional converter control circuit comprising a voltage converter for converting
Based on the difference between the target voltage indicating the voltage target of the load device and the voltage of the load device, a target current indicating the target of the current that flows during charging and discharging of the electric power storage device is obtained, and the target current and the electric power A control circuit for a bidirectional converter, characterized in that the duty ratio is obtained based on a difference between a current flowing during charging and discharging of a power storage device. The voltage of the electric power storage device and the voltage of the load device are between the electric power storage device capable of charging and discharging and the load device capable of transferring DC power, and the voltage of the electric power storage device according to the duty ratio that specifies the degree of voltage conversion A bidirectional converter control method including a voltage conversion unit for converting
Obtaining a target current indicating a target of a current flowing during charging and discharging of the electric power storage device based on a difference between a target voltage indicating a target voltage of the load device and a voltage of the load device;
Obtaining the duty ratio based on a difference between the target current and a current flowing when the electric power storage device is charged and discharged;
A control method for a bidirectional converter, comprising:

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