ELECTRICAL ENERGY CONVERTER AND DRIVE DEVICE

Abstract

Electrical energy converter comprising the following features: - a conversion unit (100) for electrical energy, which performs a bidirectional transfer of electrical energy between one terminal and the other terminal; - a first voltage detection unit (201) that detects a voltage (Vin) between the terminals of one terminal of the electrical energy conversion unit (100); - a second voltage detection unit (202) that detects a voltage (Vout) between the terminals of the other terminal of the electrical energy conversion unit (100); and - a control unit (300) that controls the operation of the electrical energy conversion unit (100), wherein the control unit (300) comprises the following: - a first calculation unit (310) that calculates a main duty cycle value (Dmain) based on a difference between a predetermined set voltage (Vout*) and the voltage (Vout) between the terminals of the other terminal, which is detected by means of the second voltage detection unit (202), and - a second calculation unit (320) that calculates an estimated value (Vincal) of the voltage (Vin) between the terminals of one terminal, based on the main duty cycle value (Dmain) calculated by the first calculation unit (310) and the voltage (Vout) between the terminals of the other terminal, detected by the second voltage detection unit (202), and wherein it then calculates a sub-duty duty cycle value (Dsub) based on the estimated value (Vincal) and the voltage (Vin) between the terminals of one terminal, detected by the first voltage detection unit (201), and - wherein the control unit calculates a duty cycle value for operating the electrical energy conversion unit (100) based on the main duty cycle value (Dmain) and the sub-duty duty cycle value (Dsub).

Description

Technical area

[0001] The present invention relates to an electric power converter that converts a voltage applied from the outside and then transmits electric power, and a drive device using such an electric power converter. State of the art

[0002] In various types of applications such as hybrid vehicles and electric vehicles, an electric power converter is used that can transmit electric power bidirectionally such that it performs a power operation for converting a DC electric power voltage supplied from a DC power source such as a battery to supply the voltage to a motor, and such that it performs a regeneration operation for supplying DC electric power generated by the motor to the DC power source.

[0003] The output voltage supplied from the electrical power converter to the motor fluctuates due to various factors, such as the fluctuation of the target voltage, motor load fluctuation, and dead time. Regarding these fluctuations in the output voltage, a control device for a boost converter is already known (see, for example, JP 2013-17302 A), which adjusts the gain in the feedback control and feedforward control of the output voltage based on the difference between the target voltage and the output voltage, as well as the rate of change of the target voltage.

[0004] JP 2010-259190 A discloses a control device for a DC / DC converter. The control device is configured to determine, when the output voltage of the DC / DC converter fluctuates by an amount equal to or greater than a voltage estimated for maximum load fluctuation, that a duty cycle fluctuation is caused by dead time, output a dead time compensation value corresponding to the prevailing converter load condition, and add the dead time compensation value to the duty cycles that operate switching elements of the DC / DC converter. In this way, the voltage fluctuation caused by the dead time is suppressed.

[0005] JP 2007 - 97 392 A shows a control device for a DC / DC converter, which is designed to determine a choke current setpoint, wherein the following steps are carried out: inputting a choke current setpoint into a high-pass filter; multiplying the thus obtained value by an inductance value of the choke; dividing the thus obtained value by the output voltage of the DC / DC converter; and controlling switching elements of the DC / DC converter based on the result of the division.

[0006] DE 11 2011 102 550 T5 discloses a DC / DC converter in which a smoothing capacitor on the high-voltage side is connected in parallel to a series circuit containing four switching devices connected in series via first to third connecting parts. A charging / discharging capacitor is connected between the first and third connecting parts. A voltage on the low-voltage side, which is applied to the second connecting part via a choke coil, is boosted by switching of the switching devices and then output from the series circuit.A first control unit calculates a first operating value based on the difference between an output voltage target value and an output voltage; a second control unit calculates a second operating value based on the difference between a voltage target value of the charge-discharge capacitor and a voltage of the charge-discharge capacitor; control blocks perform addition and subtraction for the first and second operating values; and the conductance ratios of the switching devices are controlled by gate signals.

[0007] JP 2011 - 167 011 A shows a DC / DC converter system that is installed between an energy storage device and a load driving device and performs voltage conversion by controlling a duty cycle of a switching element based on an output voltage command value.

[0008] JP 2010 - 200 517 A describes a DC / DC converter in which an actual coil current is detected and an estimated coil current is calculated for each switching cycle based on operating conditions such as input voltage, output voltage, coil inductance, and switching cycle. A fault current is determined, which is the difference between the actual coil current detected in the last cycle and the estimated coil current calculated in the last cycle. The calculation unit calculates the corrected estimated coil current based on the fault current. In a control unit, the actual coil current is controlled according to the estimated coil current.

[0009] JP 2010-268596 A discloses a control device for a converter that steps up or down the output voltage from a DC power source, comprising: a PWM control unit for performing PWM control of the converter based on a predetermined duty cycle; and a dead-time compensator for performing dead-time compensation depending on the state of a reactor current flowing in a reactor included in the converter. When at least one of the minimum and maximum values ​​of the reactor current in a switching period is within a predetermined range, the dead-time compensator compensates the duty cycle with a compensation amount within the predetermined range according to the parameter associated with the deviation between the target voltage relative to the converter and the output voltage. Summary of the inventionTechnical problem

[0010] In an electric power converter that transfers electrical power bidirectionally, the state in which the charging and discharging currents of a battery become zero occurs when switching from power operation to regeneration operation or when switching from regeneration operation to power operation. The above-mentioned fluctuations in the output voltage due to dead time occur when the charging and discharging currents of the battery are approximately zero. In a conventional auxiliary converter, a control method is used in which the charging and discharging currents of a battery are detected and then a dead time correction value is determined based on whether the detected current is positive or negative.

[0011] To prevent the output voltage controllability from deteriorating due to dead time, it is necessary to accurately determine whether the battery charging current is positive or negative, and to do so close to zero. In practice, however, the problem arises that this determination is not performed correctly due to a fault in the current measurement function or faulty detection by the measurement unit, and consequently, the output voltage controllability further deteriorates.

[0012] The present invention was conceived to solve the aforementioned problems. Its object is to provide an electrical energy converter that increases the target tracking capability of the control system even when dead time leads to fluctuations in the output voltage. Solution to the problem

[0013] The object is achieved by an electrical energy converter having the features of claim 1. Furthermore, the object is achieved by an electrical energy converter having the features of claim 3. Advantageous further developments arise from subclaims 2 and 4 to 6. Furthermore, the object is achieved by a drive device having the features of claim 7. Advantages of the invention

[0014] An electrical power converter according to the present invention enables control with a high response speed for a dead time deviation value. Consequently, the target tracking capability of the output voltage control for the dead time effect can be increased. Short description of the drawings Fig. 1 is a configuration diagram illustrating an electric power converter and a driving device described in Embodiment 1 of the present invention; Fig. 2 is a configuration diagram illustrating a control unit in the electric power converter described in Embodiment 1 of the present invention; Fig. 3 is a diagram illustrating the relationship between a gate signal and a current flowing in a reactor in the electric power converter described in Embodiment 1 of the present invention; Fig. 4 is a diagram illustrating the waveforms of a current and the like in a conventional electric power converter; Fig. 5 is a diagram illustrating the waveforms of a current and the like in the electric power converter described in Embodiment 1 of the present invention; Fig. 6 is a configuration diagram illustrating a control unit in an electric power converter described in Embodiment 2 of the present invention; Fig. 7 is a flowchart for calculating a coefficient in the control unit of the electric power converter described in Embodiment 2 of the present invention; Fig. 8 is a configuration diagram illustrating a control unit in an electric power converter described in Embodiment 3 of the present invention; Fig. 9 is a flowchart for calculating an under-duty value in the control unit of the electric power converter described in Embodiment 3 of the present invention; Fig. 10 is a configuration diagram illustrating an electric power converter and a driving device described in Embodiment 4 of the present invention; Fig. 11 is a configuration diagram illustrating a control unit in the electric power converter described in Embodiment 4 of the present invention; Fig. 12 is a configuration diagram illustrating a control unit in an electric power converter described in Embodiment 5 of the present invention; Fig. 13 is a configuration diagram illustrating an electric power converter and a driving device described in Embodiment 6 of the present invention; Fig. Fig. 14 is a diagram illustrating the relationship between a gate signal and a current flowing in a reactor in the electric power converter described in Embodiment 6 of the present invention; and Fig. 15 is a block diagram illustrating the configuration of each of the control units described in Embodiments 1 to 6 of the present invention. Description of embodimentsEmbodiment 1

[0015] An electric power converter and a driving device according to Embodiment 1 of the present invention will be described using the drawings. Fig. 1 is a configuration diagram illustrating an electric power converter and a driving device according to Embodiment 1 of the present invention. Fig. Figure 2 is a circuit diagram showing the configuration of a control unit. A drive device used in Fig. 1, is provided with a DC power source 10, an electrical power converter 20, and a motor 30. The electrical power converter 20 is provided with an electrical power conversion unit 100 and a control unit 300. The DC power source 10 is connected to one terminal of the electrical power conversion unit 100, and the motor 30 is connected to the other terminal thereof.

[0016] According to Fig. 1, the motor 30 is a motor that drives and rotates the axle of an automobile and can be operated as an electric power generator. When the motor 30 is driven, electric power transfer (power operation) is performed from the DC power source 10 to the motor 30; when the motor 30 generates electric power, electric power transfer (regenerative operation) is performed from the motor 30 to the DC power source 10.

[0017] That is, the drive device described in Embodiment 1 is a system that can bidirectionally transmit the electric power of the battery and the mechanical power of the motor. The following description assumes that the motor 30 is used to drive and rotate the axle of an automobile, a railway vehicle, or the like according to the running state of the automobile or railway vehicle, and the power operation and the regeneration operation are mutually switched as needed.

[0018] In Fig. 1, the DC power source 10 is a battery. When the power operation is performed, the battery's electric charges are discharged to the motor 30 while controlling the voltage to be applied to the motor 30. When the regeneration operation is performed, the battery is charged with DC electric power generated by the motor 30 while controlling the voltage to be applied to the motor 30. The DC power source 10 is not limited to a battery, and it can be any device as long as it is a circuit or device that can receive and output DC electric power.

[0019] The electrical power converter 20 is equipped with the electrical power conversion unit 100 and the control unit 300. The electrical power conversion unit 100 is a bidirectional electrical power conversion circuit capable of bidirectional electrical power transfer between the low-voltage side and the high-voltage side. It includes a first terminal 100a, a second terminal 100b, a third terminal 100c, and a fourth terminal 100d. The first and second terminals 100a and 100b, which are terminals on the low-voltage side, are connected to the respective ends of the DC power source 10. The third and fourth terminals 100c and 100d, which are terminals on the high-voltage side, are connected to the respective ends of the motor 30.

[0020] The electric power conversion unit 100 is a step-up chopper circuit comprising an input capacitor (C1) 101, a choke coil (L1) 102, a first switching device (Q1) 103, a second switching device (Q2) 104, and an output capacitor (C2) 105. The electric power conversion unit 100 is also equipped with two voltage detection circuits.

[0021] The following components are provided: an input voltage detection unit (a first voltage detection unit) 201 that detects the voltage across the terminals on the side of the DC power source 10, ie, the voltage across the input capacitor (C1) 101 (hereinafter referred to as input voltage Vin), and an output voltage detection unit (a second voltage detection unit) 202 that detects the voltage across the terminals on the side of the motor 30, ie, the voltage across the output capacitor (C2) 105 (hereinafter referred to as an output voltage Vout).

[0022] The input capacitor (C1) 101 is connected in parallel to the DC power source 10, and one of the terminals of the choke coil (L1) 102 is connected to the input capacitor (C1) 101. One of the terminals of the output capacitor (C2) 105 is connected to the drain of the second switching device (Q2) 104, and the other terminal is connected to the input capacitor (C1) 101.

[0023] The drain of the first switching device (Q1) 103 is connected to the other of the terminals of the choke coil (L1) 102, and its source is connected to the other of the terminals of the input capacitor (C1) 101. The source of the second switching device (Q2) 104 is connected to the junction between the choke coil (L1) 102 and the first switching device (Q1). As each of the first switching device (Q1) 103 and the second switching device (Q2) 104, which are switching semiconductors, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or the like is used.

[0024] The first switching device (Q1) 103 and the second switching device (Q2) 104 perform complementary switching based on the gate signals generated by a gate signal output unit in the control unit 300. To prevent short-circuiting resulting from the phenomenon that both the first switching device (Q1) 103 and the second switching device (Q2) 104 are turned on, a period (dead time) is provided in which both the first switching device (Q1) 103 and the second switching device (Q2) 104 are turned off.

[0025] The input voltage detection unit 201, connected across the input capacitor (C1) 101, is a voltage sensor that detects the input voltage Vin of the electrical power converter 20. The output voltage detection unit 202, connected across the output capacitor (C2) 105, is a voltage sensor that detects the output voltage Vout of the electrical power converter 20.

[0026] To prevent erroneous detection resulting from ripple voltage or noise corresponding to a switching frequency, each of these detection circuits has an appropriate low-pass filter circuit. It is not essential that the input voltage detection unit 201 and the output voltage detection unit 202 be formed within the electrical power conversion unit 100. They may also be formed outside the electrical power conversion unit 100.

[0027] The control unit 300 is a control unit that controls the electric power conversion unit 100. That is, based on the input voltage Vin detected by the input voltage detection unit 201, the output voltage detected by the output voltage detection unit 202, and a target voltage Vout*, the control unit 300 determines a duty cycle value and then outputs gate signals to the electric power conversion unit 100 for controlling the first switching device (Q1) 103 and the second switching device (Q2) 104.

[0028] Fig. 2 is a circuit diagram illustrating the detailed configuration of the control unit 300. The control unit 300 includes a first calculation unit 310 that calculates a main duty value Dmain using the output voltage Vout and the target voltage Vout*, a second calculation unit 320 that calculates a sub-duty value Dsub using the main duty value Dmain calculated by the first calculation unit 310, the input voltage Vin, and the output voltage Vout, and an adder 330 that adds Dmain and Dsub to calculate a duty value.

[0029] The output voltage (Vout) is controlled to follow the target voltage Vout*, which is preliminarily set by an unillustrated external device or the like according to the driving condition. The control unit 300 calculates the respective duty cycles for the first switching device (Q1) 103 and the second switching device (Q2) 104 of the electric power conversion unit 100, and then performs control based on the calculated duty cycles using the gate signals. As a result, for example, the motor efficiency can be increased.

[0030] The first calculation unit 310 has a subtractor 311 that calculates the difference between the target voltage Vout* and the output voltage Vout, and a first controller 312 that calculates a main duty value (Dmain) from a difference value (Verr) obtained from the subtractor 311.The second calculation unit 320 has a subtractor 321 that calculates the difference between "1" and Dmain obtained by the first calculation unit 310, a multiplier 322 that multiplies the difference value obtained by the subtractor 321 by the output voltage Vout, a subtractor 323 that obtains the difference between the value obtained by the multiplier 322 and the input voltage Vin, a second controller 324 that performs calculation processing using the value obtained by the subtractor 323, and a divider 325 that calculates the quotient of the value obtained by the second controller 324 divided by the output voltage Vout.

[0031] The motor 30 has an inverter circuit which is Fig. 1 is not shown. A DC voltage supplied to the motor 30 is converted into an AC voltage to drive and rotate a drive unit for the motor 30. The respective on-time ratios of the first switching device (Q1) 103 and the second switching device (Q2) 104 are controlled so that a target voltage is applied to the DC unit of the inverter circuit, thereby driving the motor 30.

[0032] Next, the operation of the electric power converter and the drive device according to Embodiment 1 will be explained. As the operating state of the electric power converter 20, there are two operating elements, namely, a state (power operation) in which electric power is supplied from the DC power source 10 to the motor 30 so that the motor is driven, and a state (regenerative operation) in which electric power generated by the motor 30 in a power generation state is supplied to the DC power source 10.

[0033] Fig. 3 shows the respective waveforms of the gate signal voltages for the first switching device (Q1) 103 and the second switching device (Q2) 104, as well as the respective waveforms of the inductor currents IL flowing in the inductor (L1) 102. In Fig. 3 give Fig. 3(a) and Fig. 3(b) shows the waveform of the gate signal for the first switching device (Q1) 103 and the waveform of the gate signal for the second switching device (Q2) 104, respectively.

[0034] Each of the switching devices performs an on / off operation according to an input gate signal. Each of Fig. 3(c) to 3(e) illustrate the waveform of the current flowing in the reactor (L1) 102. It shows the waveform corresponding to the value of the average current IL_ave in the reactor L1. Where Ir indicates the ripple current in the reactor L1, (c), (d), and (e) represent the case where [IL_ave ≥ Ir / 2], the case where [-Ir / 2 < IL_ave < Ir / 2], and the case where [II, ave ≤ -Ir / 2], respectively.

[0035] During power operation, the control unit 300 transmits the respective gate signals to the first switching device (Q1) 103 and the second switching device (Q2) 104, so that the first switching device (Q1) 103 and the second switching device (Q2) 104 are operated. While the first switching device (Q1) 103 and the second switching device (Q2) 104 are configured to repeatedly perform the on / off operation and, consequently, the voltage to be applied across the motor 30 is stepped up to a target voltage, the supplied electrical energy from the DC power source 10 is transmitted to the motor 30.

[0036] In the motor 30, into which the DC electric power is input through the electric power converter 20, the internal inverter circuit converts the DC electric power into AC electric power, so that the drive unit of the motor 30 is driven and rotated.

[0037] In Fig. 3, during the period in which the first switching device (Q1) 103 is turned off and the second switching device (Q2) 104 is turned on, the energy input from the DC power source 10 to the electrical energy converter 20 is accumulated in the output capacitor 105. In turn, during the period in which the first switching device (Q1) 103 is turned on and the second switching device (Q2) 104 is turned off, the energy accumulated in the output capacitor 105 is discharged.

[0038] The time ratio (the duty value having the value between 0 and 1) of the period in which the first switching device (Q1) 103 is turned on is appropriately set so that the output voltage Vout between the third terminal 100c and the fourth terminal 100d is controlled to be an arbitrary voltage.

[0039] In this situation, the control unit 300 determines the duty cycle value. Based on the determined duty cycle value, the control unit 300 transmits the respective gate signals to the switching devices, thus controlling the electrical energy conversion unit 100. The method for calculating the duty cycle value will be described later.

[0040] Next, the regeneration operation, ie, the case where [IL_ave < 0], is described. As in the case of the power operation, in the regeneration operation, the control unit 300 transmits the respective gate signals to the first switching device (Q1) 103 and the second switching device (Q2) 104, so that the first switching device (Q1) 103 and the second switching device (Q2) 104 are operated.

[0041] While the first switching device (Q1) 103 and the second switching device (Q2) 104 are configured to repeatedly perform the switching-on / off operation and consequently the voltage to be applied across the motor 30 is stepped up to a target voltage, the supplied electric power from the motor 30 is transferred to the DC power source 10, so that the DC power source 10 is charged with the DC electric power.

[0042] In Fig. 3, during the period in which the first switching device (Q1) is off and the second switching device (Q2) is on, the energy accumulated in the output capacitor 105 is discharged. In turn, during the period in which the first switching device (Q1) is on and the second switching device (Q2) is off, the energy input from the motor 30 is accumulated in the output capacitor 105. As in the case of the power operation, the timing relationships (duty values) of these operation modes are appropriately adjusted so that the output voltage Vout between the third terminal 100c and the fourth terminal 100d is controlled to be an arbitrary voltage. In this situation, the control unit 300 determines the duty values.

[0043] The control unit 300 then transmits the respective gate signals to the electrical energy conversion unit 100 so that the operation can be performed based on the calculated duty cycle values. The method for calculating the duty cycle value will be described later.

[0044] In this situation, the method in which the control unit 300 calculates the duty cycle value will be explained. The control unit 300 is characterized in that it calculates the main duty cycle value (Dmain) and the sub-duty cycle value (Dsub) based on the input voltage Vin and the output voltage Vout calculated by the input voltage detection unit 201 and the output voltage detection unit 202, respectively, formed in the electric power conversion unit 100, and a target voltage Vout*, and that it calculates the duty cycle value using the calculated main duty cycle value (Dmain) and the sub-duty cycle value (Dsub).

[0045] The control process is performed continuously or repeatedly, at a specified time (e.g., every few microseconds), so that a suitable duty cycle value can be maintained. The details are explained below.

[0046] When the duty cycle value control operation is implemented, the control unit 300 receives the input voltage Vin and the output voltage Vout detected by the input voltage detection unit 201 and the output voltage detection unit 202, respectively. In the first calculation unit 310, the subtractor 311 calculates the difference value Verr between the target voltage Vout*, which is a value determined in advance according to the driving condition and the like, and the output voltage Vout.

[0047] The first control unit 312 calculates the main duty cycle value (Dmain) using the differential value (Verr). That is, the main duty cycle value (Dmain) is determined such that the differential value (Verr) approaches zero. The first controller 312 determines the main duty cycle value (Dmain), for example, using P control, PI control, PID control, or the like. The first calculation unit 310 ensures the response to a change in the output voltage Vout.

[0048] In addition, even if the output voltage Vout deviates from the target voltage Vout* due to a sharp fluctuation of the motor 30, the first calculation unit 310 can be operated such that the output voltage Vout follows the target voltage Vout* by the response determined by the control unit 300, the electric power conversion unit 100, and the output voltage detection unit 202.

[0049] The second calculation unit 320, in turn, calculates the sub-duty value (Dsub) using the main duty value (Dmain) calculated by the first calculation unit 310, the input voltage Vin, and the output voltage Vout. Specifically, the subtractor 321 calculates (1-Dmain), and then the multiplier 322 calculates (1-Dmain) with the detected output voltage Vout. The result is an input voltage estimate Vincal. Equation (1) is a calculation formula intended for processing in the subtractor 321 and the multiplier 322. (1−Dmain)×Vout=Vincal

[0050] The subtractor 323 calculates the difference value between Vincal obtained from the multiplier 322 and the input voltage Vin detected by the input voltage detection unit 201, and then outputs the calculated difference value to the second controller 324. The second control unit 324 performs calculation processing, for example, using P control, PI control, PID control, or the like.

[0051] In Embodiment 1, it is assumed that each of the gains of the controllers has a fixed value. However, each of the gains can also have a variable value. The divider 325 divides the result obtained by the second controller 324 by the detected output voltage Vout to obtain a value corresponding to the duty cycle value. This result is the sub-duty cycle value Dsub.

[0052] The first calculation unit 310 calculates Dmain so that the difference between the target voltage Vout* and the detected output voltage Vout approaches zero. Meanwhile, the second calculation unit 320 calculates Dsub so that the duty cycle value is maintained, which corresponds to the difference between the input voltage estimate Vincal obtained by an ideal calculation and the detected input voltage Vin.

[0053] The first controller 312 and the second controller 324 have different control means or different gains, so that the response speed based on the duty value for the difference between the target voltage Vout* and the detected output voltage Vout and the response speed at the time when a deviation from the ideal state occurs and consequently the duty cycle suddenly changes can be set to the respective individual response speeds.

[0054] Next, the effect is described. First, the fluctuation of the output voltage Vout due to a dead time, which is to be solved by the present invention, is calculated based on the waveforms in Fig. 4 and Fig. 5 described. Fig. Figure 4 is a diagram illustrating the waveforms related to a conventional electrical power converter. Fig. Fig. 5 is a diagram showing the waveforms concerning the electric power converter described in Embodiment 1. In each of Fig. 4 and Fig. 5 the following applies.

[0055] Fig. 4(a) and Fig. 5(a) shows a diagram illustrating the waveform of the average value (IL_ave) of a current flowing in the reactor (L1); when the operation mode of the electric power converter 20 changes from the power operation to the regeneration operation, IL_ave changes from a positive value to a negative value; Fig. 4(b) and Fig. 5(b) shows a diagram illustrating a duty value to be set by the control unit 300; Fig. 4(c) and Fig. 5(c) shows a diagram illustrating the output voltage Vout of the electrical energy converter 20.

[0056] In the case where the control is performed using the output voltage Vout of the electric power conversion unit 100 and the target voltage Vout*, the effect of a dead time may increase the difference between the output voltage Vout and the target voltage Vout*, as shown in Fig. 4. Where don, T, td, IL_ave, and Ir respectively indicate the duty cycle value for the first switching device (Q1) 103, the switching period, the dead time, the average current in the inductor L1, and the ripple current in the inductor L1, then the dead time and the on-time of the first switching device (Q1) 103 do not overlap when [IL_ave ≧ Ir / 2] is satisfied. Therefore, the relationship between the input voltage Vin and the output voltage Vout is given in the form of equation (2). (1−Dmain)×Vout=Vincal

[0057] On the other hand, when [-Ir / 2 < IL_ave < Ir / 2] is satisfied, one side of the dead period and the turn-on time of the first switching device (Q1) 103 overlap. Consequently, the relationship between the input voltage Vin and the output voltage Vout is given by equation (3). Vout=11−(don+tdT)Vin

[0058] When [IL_ave ≤ -Ir / 2] is satisfied, each of the two sides of the dead period and the turn-on time of the first switching device overlaps. Therefore, the relationship between the input voltage Vin and the output voltage Vout is given by Equation (4). Vout=11−(don+2tdT)Vin

[0059] As described above, even if driving is performed with one and the same duty cycle value, the effect of dead time causes the output voltage Vout to deviate from equation (2), which is the relationship equation of an ideal boost converter in which the dead time has no effect.

[0060] In this situation, on the basis of Fig. 4 explains the waveforms at a time when a control unit does not have a second calculation unit 320, but only the first calculation unit 310 is formed.

[0061] When the operating mode of the electric power converter changes from the power mode to the regeneration mode, the relationship between the average current IL_ave of the reactor current and the ripple current Ir from the aforementioned equation (2) transitions to equation (3) and equation (4), in that order. The dead time td is superficially added to the duty value for the first switching device (Q1) 103; accordingly, in the case where the duty value calculated by the control unit corresponds to the duty value don for the first switching device (Q1) 103, the Dmain calculated by the first calculation unit 310 decreases by the dead time td each time the state transitions. In the case where the second calculation unit 320 is not formed, Dmain becomes a duty value for controlling the electric power conversion unit 100.

[0062] In a transition period in which the state transitions from equation (2) to equation (3) and in a transition period in which the state transitions from equation (3) to equation (4), the waveform of the current in the reactor L1 is discontinuous, and consequently, the on-time duty value based on the feedback control is not reflected in the effect shown in the output voltage.

[0063] As a result, the output voltage Vout does not follow the target voltage Vout*, and overshoot occurs. If the gain of the first controller 312 is too high, undershoot occurs continuously from the moment the current discontinuous state ends. If the gain of the first controller 312 is too low, the overshoot value increases. Similarly, if the system's operating mode changes from regeneration mode to power mode, the output voltage Vout does not follow the target voltage Vout*, and undershoot occurs.

[0064] Based on Fig. 5, the waveforms associated with the electrical energy converter having the second calculation unit 320 characteristic of the present invention will be described next.

[0065] The second calculation unit 320 calculates the under-duty value Dsub based on the value of the deviation from the ideal state, as expressed by equation (1). In the case where the second controller 324 performs P control, the current in the reactor L1 is discontinuous, and the second calculation unit 320 changes Dsub proportionally to the difference when overshoot occurs. Since the value corresponding to the time ratio (Td / fsw) of the dead time is calculated according to each operating state, no undershoot occurs in the state, as indicated by equation (3), at a time when the discontinuous state ends.

[0066] As a result, the first calculation unit 310 is designed to have a sufficient response speed for fluctuations in the target voltage, and the second calculation unit 320 is designed to calculate a deviation value caused by the dead time with a high response speed. Consequently, it is possible to ensure appropriate response to various disturbances with a single duty cycle value.

[0067] The electric power converter and the drive device described in Embodiment 1 are configured as described above. Therefore, even in the case where the current value flowing in the internal reactor approaches zero in the situation of switching between the power operation and the regeneration operation, deterioration of controllability can be suppressed, and thus the target tracking ability of the control can be increased, even for a fluctuation in the output voltage caused by the dead time. Embodiment 2

[0068] In the electric power converter described in Embodiment 1, the duty value is set, while the gain of each of the controllers is fixed in the control unit. However, with respect to the electric power converter described in Embodiment 2, the case in which the gain of a controller is variable will be described. The configurations of an electric power converter and a drive device according to Embodiment 2 are the same as those of the electric power converter and the drive device described in Fig. 1. Therefore, the explanations for them are omitted.

[0069] Fig. 6 illustrates the configuration of a control unit 300 according to Embodiment 2. The configuration of the control unit 300 according to Embodiment 2 is the same as that of the control unit according to Embodiment 1. However, the operation of a second controller 324a is different. Details thereof will be described below.

[0070] The operations of the electric power converter and the drive device according to Embodiment 2 are the same as those of the electric power converter and the drive device according to Embodiment 1, except for the setting method for the duty value in the control unit 300. Therefore, explanations thereof will be omitted. The setting method for the duty value is the same as in Embodiment 1, except for the setting method for the duty value in the second controller 324a.

[0071] As in the case of the control unit described in Embodiment 1, the second controller 324a applies calculation processing to the result obtained in the subtractor 323. However, unlike the case described in Embodiment 1, its gain is variable. If y indicates the calculation result in the second controller 324a, the second controller 324a applies the calculation processing indicated by the following equation (5) to the calculation result (x) in the subtractor 323. y=Kd⋅x

[0072] The setting method for the value of a coefficient Kd by which the calculation result x is multiplied in the subtractor 323 is described using Fig. 7 described. Fig. 7 is a flowchart illustrating the setting method for the coefficient Kd in the second controller 324a. In step S101, it is determined whether or not the current operating state is the assist operating state or the boost operating state based on the target voltage Vout* and the input voltage Vin. If the determination result of [Vout*>Vin] is NO, the current operating state is not the assist operating state, and therefore, the dead time has no effect. Therefore, Kd is set to "0" in step S104.

[0073] In the case that the determination result in step S101 is YES, that is, in the case that the electric power converter 20 is in the assist operation state, Kd is determined according to the equation (6) in step S102. Kd=−Ca⋅Vin / Vout*+Cb

[0074] In Equation (6), Ca and Cb are arbitrary coefficients. Consequently, Kd becomes a variable value according to at least the ratio of the input voltage Vin to the target voltage Vout*. Generally, the amount of overshoot caused by dead time is large when the assist ratio (Vout* / Vin) is high, and small when the assist ratio (Vout* / Vin) is low.

[0075] When it is assumed that the feedback control has a characteristic that its stability is high when the assist ratio is high and that its stability is low when the assist ratio is low, it is allowed to use Kd as a variable gain using the calculation result to be determined in step S102.

[0076] As a calculation method for the variable gain to be used in step S102, a calculation based on the input voltage Vin, the output voltage Vout or the target voltage Vout*, the main duty value Dmain, the value of the current in the reactor (L1), or the like may be used.

[0077] As the calculation method for the variable gain in step S101, a linear equation or a quadratic equation may be used.

[0078] A calculation formula may be used to calculate an appropriate value of Kd based on the stability of the feedback control determined by the circuit constants of the first calculation unit, the second calculation unit, and the electrical energy conversion unit. In step S102, a method may be used in which the value of Kd is determined not using a calculation formula, but by providing a map based on the conditions of voltages, currents, and the like.

[0079] The electric power converter and drive device according to Embodiment 2 are configured as described above. Therefore, they can achieve an effect the same as that achieved in Embodiment 1. Furthermore, different values ​​are used as Kd of the second controller 324a according to the assist ratio or the reactor current, making it possible to realize control that has a great effect on suppressing overshoot according to various conditions and that is stable. Embodiment 3

[0080] In Embodiment 3, an electric power converter is described in which a limiter is formed in the control unit described in Embodiment 2. The configurations of an electric power converter and a drive device according to Embodiment 3 are the same as those of the electric power converter and the drive device described in Fig. 1. Therefore, the explanations for them are omitted.

[0081] Fig. Fig. 8 illustrates the configuration of a control unit 300 according to Embodiment 3. In Fig. 8, the explanations of the configurations are omitted, which are the same as those in Fig. 6 are. In Fig. 8, a limiter 326 is a calculation unit that applies limit processing to the calculation result in the divider 325, thus limiting its variable range. The operation will be described next.

[0082] The operations of the electric power converter and drive device according to Embodiment 3 are the same as those of the electric power converter and drive device according to Embodiment 1, except for the setting method for the duty cycle value in the control unit 300. Therefore, explanations thereof are omitted. The setting method for the duty cycle value is the same as in Embodiment 2, except for the limiting processing applied to the calculation result in the divider 325.

[0083] In the aforementioned embodiments, the calculation result of the divider 325 is referred to as the sub-duty value Dsub. However, in Embodiment 3, the calculation result of the divider 325 is denoted by a different reference symbol Dsub' for convenience. The variable range of Dsub is limited by applying limiting processing to Dsub', which is the calculation result of the divider 325. Through the feedback control by the second calculation unit 320, Dsub calculated by the second calculation unit 320 compensates for the fluctuations in the output voltage caused by the dead time.

[0084] Accordingly, the upper and lower limits are determined by the ratio of the dead time to the switching frequency. In the case of a fixed carrier, the width is set to "fsw × Td" based on the ratio between the dead time (Td) and the switching period (1 / fsw), and the variable range is set to "±fsw × Td ÷ 2". Based on Fig. 9 explains the limiting processing at a time when the switching frequency changes according to the operating condition.

[0085] Fig. 9 shows a flowchart for calculating the under-duty value. In step S201, the upper limit (Up_lim) and the lower limit (Low_lim) are calculated from the currently used switching frequency (fsw) and the dead time (Td). If Dsub' is less than the lower limit in step S202, the lower limit is set to Dsub in step S205. If Dsub' is greater than the upper limit in step S202, the upper limit is set to Dsub in step S206.

[0086] If neither the condition in step S202 nor the condition in step S203 is satisfied, Dsub is equal to Dsub'. The electric power converter and the drive device described in Embodiment 3 are configured as described above. Therefore, they can achieve the same effect as that achieved in Embodiment 1.

[0087] Furthermore, the sub-duty value Dsub to be calculated by the second calculation unit 320 is allowed to be as large as the duty value only to correct the dead time. The duty ratio (Td / fsw) of the dead time for each switching frequency (fsw) is calculated, and limiting processing is applied to the calculated duty ratio, so that the stability of the feedback control can be ensured. Embodiment 4

[0088] Regarding the electric power converter described in each of the above embodiments, a configuration is described in which a voltage detection unit is used to detect the state within the electric power converter. However, regarding the electric power converter according to Embodiment 4, the case in which a current detection unit is further formed and the under-duty value is calculated using a current flowing in the reactor will now be described.

[0089] Fig. 10 is a block diagram illustrating the configuration of an electric power converter and a drive device according to Embodiment 4. In Fig. 10, the devices or circuits are designated by reference numerals which are the same as those in Fig. 1 are the same or similar devices or circuits. Accordingly, the explanations for them are omitted.

[0090] A current detection unit 110 is a detector for detecting a current flowing in the choke coil (L1) 102. For example, the current detection unit 110 is a detector comprising a shunt resistor and an amplifier, or a Hall-type current detector. The addition of the current detection unit 110 makes it possible to detect the current IL in the choke coil (L1).

[0091] Fig. Fig. 11 illustrates the configuration of a control unit 300 according to Embodiment 4. Compared to the control unit shown in Fig. 6, a circuit for calculating the under-duty value using the current IL detected by the current detection unit 110 is added to the control unit 300. The devices or circuits designated by the same reference numerals as those in the Fig. 6, the same or similar devices or circuits are used in the control unit shown in Fig. 6. Consequently, explanations for this are omitted.

[0092] A multiplier 328 is a calculation unit that multiplies the current IL in the choke coil 102, detected by the current detection unit 110, by Lm / Ts. Here, Lm is the inductance value of the choke coil 102. In the case of continuous-time control, Ts is set to "1," and in the case of discrete-time control using a microcomputer or the like, Ts is the sampling time. An adder 327 is a calculation circuit for adding the result obtained by the subtractor 323 to the result obtained by the multiplier 328.

[0093] Next, the operation is described.

[0094] The operations of the electric power converter and drive device according to Embodiment 4 are the same as those of the electric power converter and drive device according to Embodiment 1, except for the setting method for the duty value in the control unit 300. Therefore, explanations thereof will be omitted. Until the calculation by the subtractor 323, the setting of the duty value is performed in the same way as the control unit 300 described in Embodiment 1 sets the duty value.

[0095] The multiplier 328 multiplies the current value IL in the reactor (L1) 102, detected by the current detection unit 110, by Lm / Ts. In an adder, the calculation result in the subtractor 327 is added to the calculation result in the multiplier 328. In the case of continuous-time control, Ts of the multiplier 328 is set to "1," and in the case of discrete-time control using a microcomputer or the like, a sampling time is used as Ts.

[0096] The inductance value of the reactor 102 is used as Lm. However, the minimum value, the maximum value, or the nominal value of the inductance value of a reactor to be used can also be assumed as Lm. In a second calculation unit 340, the under-duty value is calculated based on the calculation result in the adder 327 using the second controller 324a and the divider 325.

[0097] The electric power converter and the drive device according to Embodiment 4 are configured as described above. Therefore, they can achieve an effect the same as that of the electric power converter and the drive device described in Embodiment 1. Furthermore, the calculation of the dead time is also performed based on the reactor current. Consequently, the value of the sub-duty value Dsub can be calculated more accurately, and accordingly, the effect of further suppressing the amount of overshoot caused by the dead time can also be achieved. Embodiment 5

[0098] In Embodiment 5, an electric power converter is described that calculates a sub-duty value using a control unit configured differently from the control unit described in Embodiment 4. The configurations of an electric power converter and a drive device according to Embodiment 5 are the same as those of the electric power converter and the drive device described in Fig. 1. Therefore, the explanations for them are omitted. Fig. 12 shows the configuration of a control unit 300. In Fig. 12, the first calculation unit 310 is the same as the one shown in Fig. 2 is described.

[0099] As in the case with the second calculation unit described in Embodiment 1, a second calculation unit 350 calculates the sub-duty value (Dsub) using the main duty value (Dmain) determined by the first calculation unit 310. The second calculation unit 350 includes: the subtractor 321 that calculates (1-Dmain) using the main duty value (Dmain), a divider 329 that divides the input voltage Vin by the output voltage Vout, the subtractor 323 that calculates the difference between the calculation result in the subtractor 321 and the calculation result in the divider 329, a second controller 324a that applies calculation processing to the calculation result in the subtractor 323, and the limiter 326 that applies limiting processing to the calculation result in the second controller 324a.

[0100] Next, the operation is described.

[0101] The operations of the electric power converter and the drive device according to Embodiment 5 are the same as those of the electric power converter and the drive device according to Embodiment 1, except for the setting method of the duty value in the control unit 300. Therefore, the explanations thereof are omitted.

[0102] Regarding the setting method for the duty cycle value, the operations of the control unit described in Embodiment 1 and the second calculation unit 350 differ from each other. Therefore, the differences will be described below. In the second calculation unit 350, the subtractor 321 calculates an estimated value (1-Dmain) for the duty cycle value using the main duty cycle value Dmain calculated by the first calculation unit 310.

[0103] Divider 329 calculates Vin / Vout. Then, subtractor 323 calculates the difference between Vin / Vout calculated by divider 329 and the estimated value (1-Dmain) of the duty cycle value calculated by subtractor 321. The difference value is the one to which the calculation processing is applied in second controller 324a. This value is the value obtained by dividing the input voltage estimated value Vincal, as described in Embodiment 1, by the output voltage Vout.

[0104] The second controller 324a multiplies the calculation result in the subtractor 323 by the value of Kd. The value of Kd is calculated, for example, using P control, PI control, PID control, or the like. In this situation, either a fixed value or a variable value can be used as Kd, as described in Embodiment 2. In Embodiment 5, for simplicity, the calculation result in the second controller 324a is regarded as the sub-duty value Dsub'.

[0105] The limiter 326 applies appropriate limit processing to the obtained Dsub' to limit its value, so that the sub-duty value Dsub is calculated. The electric power converter and the drive device described in Embodiment 5 are configured as described above. Therefore, an effect the same as that of the electric power converter and the drive device described in Embodiment 1 can be achieved.

[0106] Compared with the electric power converter and drive device described in each of Embodiments 1 and 3, the circuit for the second calculation unit 320 can be omitted. In the case of implementation in SW (software) of a microcomputer or the like, the calculation processing in the second calculation unit 320 can be omitted. Embodiment 6

[0107] Regarding the electric power converter described in Embodiment 1, a configuration is described in which a DC / DC converter equipped with two switching devices is used as the electric power conversion unit. However, regarding the electric power converter described in Embodiment 6, a configuration is described in which a multi-level converter is used as the electric power conversion unit.

[0108] Fig. 13 is a configuration diagram illustrating the configurations of an electric power converter and a drive device according to Embodiment 6. In Fig. 13, the DC power source 10 and the motor 30 are the same as those in Embodiment 1. Therefore, explanations thereof are omitted. As the control unit 300 in the electric power converter 20, any of the control units described in the aforementioned embodiments can be used.

[0109] The electric power conversion unit 100 is a boost chopper circuit including the input capacitor (C1) 101, the choke coil (L1) 102, a first switching device (Q3) 106, a second switching device (Q4) 107, a third switching device (Q5) 108, a fourth switching device (Q6) 109, an output capacitor (C2) 105, and a flying capacitor (C0) 111. The following components are arranged therein: the input voltage detection unit 201, the output voltage detection unit 202, and a flying capacitor voltage detection unit 203 that detects the voltage across the respective capacitors.

[0110] The input capacitor (C1) 101 is connected in parallel to the DC power source 10, and one of the terminals of the choke coil (L1) 102 is connected to the input capacitor (C1) 101. One of the terminals of the output capacitor (C2) 105 is connected to the drain of the fourth switching device (Q6) 109, and the other terminal is connected to the input capacitor (C1) 101. The respective terminals of the flying capacitor (C0) 111 are connected to the connection point between the first and second switching devices and the connection point between the third and fourth switching devices.

[0111] The drain of the first switching device (Q3) 106 is connected to the source of the second switching device (Q4) 107, and its other terminal is connected to the input capacitor (C1) 101. The drain of the second switching device (Q4) 107 is connected to the other terminal of the choke coil (L1) 102. One of the terminals of the floating capacitor (C0) 111 is connected to the junction between the first switching device (Q3) 106 and the second switching device (Q4) 107.

[0112] The source of the third switching device (Q5) 108 is connected to the junction between the choke coil (L1) 102 and the second switching device (Q4) 107, and its drain is connected to the other terminal of the floating capacitor (C0) 111. The source of the fourth switching device (Q6) 109 is connected to the drain of the third switching device (Q5) 108, and its drain is connected to the output capacitor (C2) 105. The other terminal of the output capacitor (C2) 105 is connected to the junction between the input capacitor (C1) 101 and the first switching device (Q3) 106.

[0113] Each of the first switching device (Q3) 106, the second switching device (Q4) 107, the third switching device (Q5) 108, and the fourth switching device (Q6) 109 is a switching semiconductor; for example, an IGBT, a MOSFET, or the like is used. The first switching device (Q3) 106 and the fourth switching device (Q6) 109 perform complementary switching based on gate signals generated by the control unit 300. The second switching device (Q4) 107 and the third switching device (Q5) 108 perform complementary switching based on gate signals generated by the control unit 300.

[0114] Furthermore, the respective phases of the gate signals of the first switching device (Q3) 103 and the second switching device (Q4) 104 are offset by 180° from each other with respect to the switching frequency (fsw). To avoid short-circuiting resulting from the phenomenon that both the first and fourth switching devices are turned on, a suitable dead period is provided during which both the first and fourth switching devices are turned off; to avoid short-circuiting resulting from the phenomenon that both the second and third switching devices are turned on, a suitable dead period is provided during which both the second and third switching devices are turned off.

[0115] The input voltage detection unit 201, connected across the input capacitor (C1) 101, is a voltage sensor that detects the input voltage Vin of the electrical power converter 20. The output voltage detection unit 202, connected across the output capacitor (C2) 105, is a voltage sensor that detects the output voltage Vout of the electrical power converter 20. The flying capacitor voltage detection unit 203 is connected across the flying capacitor (C0) 111.

[0116] To prevent erroneous detection resulting from ripple voltage or noise corresponding to a switching frequency, each of these detection circuits has an appropriate low-pass filter circuit. These detection units do not necessarily have to be incorporated into the electrical power conversion unit 100. They may also be mounted outside the electrical power conversion unit 100. The operation will be described next.

[0117] The calculation method for the duty cycle value of the electric power converter according to Embodiment 6 may be any of the methods described in Embodiments 1 to 5 above. The operation of each of the switching devices is controlled based on the calculated duty cycle value.

[0118] Fig. Figure 14 is a diagram illustrating the relationship between the gate signals and the currents flowing in the reactor in the electric power converter. The respective gate signals for the first to fourth switching devices Q3, Q4, Q5, and Q6 in the electric power conversion unit 100 and the reactor currents are calculated based on Fig. 14. In Fig. 14 places Fig. 14(a), Fig. 14(b), Fig. 14(c) and Fig. 14(d) shows the waveform of the gate signal for the first switching device (Q3) 106, the waveform of the gate signal for the fourth switching device (Q6) 109, the waveform of the gate signal for the second switching device (Q4) 107, and the waveform of the gate signal for the third switching device (Q5) 108, respectively.

[0119] Each of the switching devices performs an on / off operation according to an input gate signal. Each of the Fig. 14(e) to 14(g) shows the waveform of the current flowing in the choke coil (L1) 102. It shows the waveform corresponding to the value of the average current IL_ave in the choke coil L1. Where Ir indicates the ripple current in the choke coil L1, Fig. 14(e), Fig. 14(f) and Fig. 14(g) represents the case where [IL_ave ≥ Ir / 2], the case where [-Ir / 2 < IL_ave < Ir / 2], and the case where [IL_ave ≤ -Ir / 2], respectively.

[0120] First, the power operation will be described, that is, the case where the average value (IL_ae) of the current flowing in the reactor (L1) 102 is greater than "0." In the power operation, the control unit 300 transmits the respective gate signals to the first to fourth switching devices 106 to 109, causing each of the switching devices to perform the on / off operation. While each of the switching devices is caused to repeatedly perform the on / off operation, and consequently, the voltage to be applied across the motor 30 is stepped up to a target voltage, the supplied electric power from the DC power source 10 is transmitted to the motor 30.

[0121] In the motor 30 to which the DC electrical energy is transmitted through the electrical energy converter 20, the internal inverter circuit converts the DC electrical energy into AC electrical energy, so that the drive unit of the motor 30 is driven and rotated.

[0122] In Fig. 14, during the period in which the first switching device (Q3) 106 is turned on, the fourth switching device (Q6) 109 is turned off, the second switching device (Q4) 107 is turned on and the third switching device (Q5) 108 is turned off, the energy accumulated in the output capacitor 105 is discharged.

[0123] During the period in which the first switching device (Q3) 106 is turned on, the fourth switching device (Q6) 109 is turned off, the second switching device (Q4) 107 is turned off, and the third switching device (Q5) 108 is turned on, the energy accumulated in the output capacitor 105 is discharged, and energy input from the DC power source 10 to the electric power converter 20 is accumulated in the flying capacitor 111.

[0124] During the period in which the first switching device (Q3) 106 is turned off, the fourth switching device (Q6) 109 is turned on, the second switching device (Q4) 107 is turned on, and the third switching device (Q5) 108 is turned off, the energy input from the DC power source 10 to the electric power converter 20 is accumulated in the flying capacitor 111 and the output capacitor 105.

[0125] The time ratio (duty value) of the period during which the first switching device (Q3) 106 is turned on is appropriately adjusted so that the output voltage Vout between the third terminal 100c and the fourth terminal 100d can be controlled to assume any desired voltage. In this situation, the control unit 300 determines the duty value. Based on the determined duty value, the control unit 300 transmits the respective gate signals to the switching devices, thereby controlling the electrical energy conversion unit 100.

[0126] Next, the regeneration operation, ie, the case where [IL_ave < 0], will be described. As in the case of the power operation, the control unit 300 transmits the respective gate signals to the first to fourth switching devices 106 to 109 in the regeneration operation, causing each of the switching devices to operate.

[0127] While each of the switching devices is caused to repeatedly perform the turning-on / turn-off operation and consequently the voltage to be applied across the motor 30 is stepped up to a target voltage, the supplied electric power from the motor 30 is transferred to the DC power source 10, and DC electric power is charged into the DC power source 10.

[0128] In Fig. 14, during the period in which the first switching device (Q3) 106 is turned on, the fourth switching device (Q6) 109 is turned off, the second switching device (Q4) 107 is turned on and the third switching device (Q5) 108 is turned off, the energy supplied by the motor 30 is accumulated in the output capacitor 105.

[0129] During the period in which the first switching device (Q3) 106 is turned on, the fourth switching device (Q6) 109 is turned off, the second switching device (Q4) 107 is turned off, and the third switching device (Q5) 108 is turned on, the energy supplied from the motor 30 is accumulated in the output capacitor 105, and the energy in the flying capacitor 111 is discharged to the DC power source 10.

[0130] During the period in which the first switching device (Q3) 106 is turned off, the fourth switching device (Q6) 109 is turned on, the second switching device (Q4) 107 is turned on, and the third switching device (Q5) 108 is turned off, the energy accumulated in the output capacitor 105 is discharged into the DC power source 10, and energy is accumulated in the flying capacitor 111.

[0131] As in the case of power operation, the timing ratios (duty cycle values) of these operation modes are appropriately adjusted so that the output voltage Vout between the third terminal 100c and the fourth terminal 100d can be controlled to be any desired voltage. In this situation, the control unit 300 determines the duty cycle values. Then, the control unit 300 transmits the respective gate signals to the electrical energy conversion unit 100 so that the operation can be performed based on the calculated duty cycle values.

[0132] In both power mode and regeneration mode, the first switching device (Q3) 106 and the fourth switching device (Q6) 109 perform complementary switching, and the dead time (Td) is provided to prevent short-circuiting. The second switching device (Q4) 107 and the third switching device (Q5) 108 also perform complementary switching, and the dead time (Td) is provided to prevent short-circuiting.

[0133] The first switching device (Q3) 106 and the second switching device (Q4) 107 perform respective switching operations whose phases are shifted by 180° from each other. Each of the on-times of the first and second switching devices Q3 and Q4 is the multiplication of the on-time value calculated by the control unit by the switching period (1 / tsw = fsw).

[0134] The voltage Vcf across the flying capacitor (C0) 111 is controlled to always be half of Vout. The waveform of the inductor current in this situation is shown. As in the case of Embodiment 1, the switching device that is turned on during the dead time (Td) changes depending on whether the inductor (L1) is positive or negative.

[0135] Therefore, it is necessary to change the duty cycle value. In a case where switching is performed using the electric power conversion unit 100 described in Embodiment 6 and the Fig. 14, the frequency of the choke coil current becomes twice as high as the switching frequency, and the voltage applied to the choke coil 102 becomes half that of Embodiment 1.

[0136] In the electric power converter and the drive device described in Embodiment 6, since the switching frequency of the reactor current is doubled, the state in which an intermittent current is caused by the dead time occurs twice as frequently as in Embodiment 1. Consequently, the effect of forming the second calculation unit 320 is much more pronounced. Furthermore, since a multi-level converter is used as the electric power conversion unit, the reactor 102 can be downsized.

[0137] The electric power converter described in Embodiment 6 is configured to use a multi-level converter with two levels. However, it should be understood that a multi-level converter with three or more levels may also be used.

[0138] Each of the calculation circuits of the control units described in Embodiments 1 to 6 can be implemented either in hardware or in software. When implemented in software, the calculation circuit can be implemented using a storage device and a processing device as shown in Fig. 15. The processing device (processor) reads and implements a program stored in the storage device (memory) so that the calculation circuit can be realized. List of reference symbols 10 DC power source 20 electrical energy converters 30 engine 100 conversion unit for electrical energy 100a - 100d connection 101 Input capacitor 102 Choke coil 103 first switching device 104 second switching device 105 Output capacitor 106 first switching device 107 second switching device 108 third switching device 109 fourth switching device 201 Input voltage detection unit (first voltage detection unit) 202 Output voltage detection unit (second voltage detection unit) 300 control unit 310 first calculation unit 311 Subtractors 312 first control 320 second calculation unit 321 subtractors 322 multipliers 323 Subtractors 324 second control 325 dividers 326 limiter 330 adders 340 second calculation unit 350 second calculation unit

Claims

[1] Electrical energy converter comprising: - an electrical energy conversion unit (100) which performs a bidirectional transfer of electrical energy between one terminal and the other terminal; - a first voltage detection unit (201) that detects a voltage (Vin) between the terminals of the one terminal of the electrical energy conversion unit (100); - a second voltage detection unit (202) which detects a voltage (Vout) between the terminals of the other terminal of the electrical energy conversion unit (100); and - a control unit (300) that controls the operation of the electrical energy conversion unit (100), the control unit (300) comprising: - a first calculation unit (310) which calculates a main duty cycle value (Dmain) on the basis of a difference between a predetermined target voltage (Vout*) and the voltage (Vout) between the terminals of the other terminal, which is detected by the second voltage detection unit (202), and - a second calculation unit (320) which calculates an estimated value (Vincal) of the voltage (Vin) between the terminals of one terminal, based on the main duty cycle value (Dmain) calculated by the first calculation unit (310) and the voltage (Vout) between the terminals of the other terminal, which is detected by the second voltage detection unit (202), and then calculates a sub-duty cycle value (Dsub) based on the estimated value (Vincal) and the voltage (Vin) between the terminals of the one terminal, which is detected by the first voltage detection unit (201), and - wherein the control unit calculates a duty cycle value for operating the electrical energy conversion unit (100) based on the main duty cycle value (Dmain) and the sub-duty cycle value (Dsub). [2] The electric power converter according to claim 1, wherein the second calculation unit (320) calculates the sub-duty value (Dsub) by multiplying a difference value between the estimated value (Vincal) and the voltage (Vin) between the terminals of the one terminal detected by the first voltage detection unit (201) by a variable coefficient determined on the basis of the voltage (Vin) between the terminals of the one terminal detected by the first voltage detection unit (201) and the voltage (Vout) between the terminals of the other terminal detected by the second voltage detection unit (202). [3] Electrical energy converter comprising: - an electrical energy conversion unit (100) which performs a bidirectional transfer of electrical energy between one terminal and the other terminal; - a first voltage detection unit (201) that detects a voltage (Vin) between the terminals of the one terminal of the electrical energy conversion unit (100); - a second voltage detection unit (202) which detects a voltage (Vout) between the terminals of the other terminal of the electrical energy conversion unit (100); and - a control unit (300) that controls the operation of the electrical energy conversion unit (100), the control unit (300) comprising: - a first calculation unit (310) which calculates a main duty cycle value (Dmain) on the basis of a difference between a predetermined target voltage (Vout*) and the voltage (Vout) between the terminals of the other terminal, which is detected by the second voltage detection unit (202), and - a second calculation unit (320) that calculates a difference value (1-Dmain) by subtracting the main duty value (Dmain) calculated by the first calculation unit (310) from 1, and then calculates the sub-duty value (Dsub) on the basis of the difference value (1-Dmain), the voltage (Vin) between the terminals of one terminal detected by the first voltage detection unit (201), and the voltage (Vout) between the terminals of the other terminal detected by the second voltage detection unit (202), wherein the control unit calculates a duty value for operating the electrical energy conversion unit (100) on the basis of the main duty value (Dmain) and the sub-duty value (Dsub). [4] An electric power converter according to any one of claims 1 to 3, wherein the second calculation unit (320) has a limiter that applies limiting processing to the sub-duty value (Dsub). [5] An electric power converter according to any one of claims 1 to 3, further comprising a current detection unit (110) that detects a current flowing in a reactor (L1) formed in the electric power conversion unit (100), wherein the second calculation unit (320) calculates the sub-duty value (Dsub) based on the current detected by the current detection unit (110). [6] An electric power converter according to any one of claims 1 to 5, wherein the electric power conversion unit (100) performs bidirectional transmission of electric power between the one terminal and the other terminal using a multi-level converter. [7] A drive device comprising a DC power source (10), a motor (30) and an electrical energy converter (20) having one terminal connected to the DC power source (10) and the other terminal connected to the motor (30), the electrical energy converter (20) comprising: - an electrical energy conversion unit (100) that performs a bidirectional transfer of electrical energy between the DC power source (10) and the motor (30); - a first voltage detection unit (201) that detects a voltage (Vin) between the terminals on the DC power source (10) side of the electrical energy conversion unit (100); - a second voltage detection unit (202) which detects a voltage (Vout) between the terminals on the motor side (30) of the electrical energy conversion unit (100); and - a control unit (300) that controls the conversion operation of the electrical energy conversion unit (100), the control unit (300) comprising: - a first calculation unit (310) which calculates a main duty cycle value (Dmain) on the basis of a predetermined target voltage (Vout*) and the voltage (Vout) between the terminals on the motor side (30) detected by the first voltage detection unit (202), and - a second calculation unit (320) that calculates an estimated value (Vincal) of the voltage (Vin) between the terminals on the DC power source (10) side based on the main duty cycle (Dmain) calculated by the first calculation unit (310) and the voltage (Vout) between the terminals on the motor side (30) detected by the second voltage detection unit (202), and calculates a sub-duty cycle (Dsub) based on the estimated value (Vincal) and the voltage (Vin) between the terminals on the DC power source (10) side detected by the second voltage detection unit (201), and wherein the control unit (300) calculates a duty cycle value for operating the electrical energy conversion unit (100) based on the main duty cycle value (Dmain) and the sub-duty cycle value (Dsub). calculated.

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