JP6121919B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that charges a secondary battery from an AC power supply.

  Conventionally, there is a power conversion device described in Patent Document 1 for the purpose of reducing the capacity of a smoothing capacitor.

  In the power conversion device described in Patent Literature 1, AC input power is rectified to generate a rectified voltage, and the generated rectified voltage is switched to generate a pulse voltage. Then, the generated pulse voltage is smoothed and supplied to the secondary battery. In addition, the switching duty ratio is changed to reduce the pulsating voltage so that the waveform of the AC input current includes a fundamental wave component and a harmonic component composed of a sine wave.

JP 2010-88150 A

  In the power conversion device described in Patent Document 1, no consideration is given to the abnormality of the AC power supply such as an instantaneous voltage drop. In general, since the response frequency of voltage control of the smoothing capacitor is low, the voltage applied to the smoothing capacitor cannot be stabilized when the AC power supply is abnormal. Therefore, even if the pulsation voltage can be reduced, the capacity of the smoothing capacitor must be taken into consideration when the voltage of the AC power supply is abnormal, and it is still necessary to increase the capacity of the capacitor.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power converter capable of reducing the capacity of a smoothing capacitor and stably operating even when an AC power supply is abnormal. It is in.

  The present invention has been made to solve the above-described problem, and is a power converter for charging a secondary battery with an AC power supply, and includes an input terminal to which the AC power supply is connected, and a plurality of An AC-DC converter having a switching element, an output terminal connected to the secondary battery, a plurality of switching elements, a DC-DC converter connected to the AC-DC converter, and an AC- A smoothing capacitor connected between the DC converter and the DC-DC converter, input current detection means for detecting a current flowing between the smoothing capacitor and the DC-DC converter, and an output from the DC-DC converter At least one of output current detection means for detecting a current to be detected, capacitor voltage detection means for detecting the voltage of the smoothing capacitor, a switching element of the AC-DC converter, and a switch of the DC-DC converter. A control circuit that performs ON / OFF control of the chucking element. The control circuit receives the current detected by the input current detection means or the current detected by the output current detection means and the voltage detected by the capacitor voltage detection means. The voltage of the smoothing capacitor is controlled by changing the duty ratio of the ON / OFF signal of the switching element of the DC-DC converter based on the voltage command value.

  Since the AC-DC converter suppresses harmonics of the input current by the PFC operation, it is necessary to make the control response frequency sufficiently lower than the frequency of the input power, for example, the frequency of the power of the AC power supply is 50 to 60 Hz. In the case of, it is designed to be about several Hz to 10 Hz. Therefore, if the AC-DC converter controls the capacitor voltage, the AC-DC controller control cannot follow the input AC power when the AC power supply is abnormal.

  In this regard, with the above configuration, the voltage of the smoothing capacitor is controlled by a DC-DC converter that does not have a restriction on the response frequency instead of an AC-DC converter that has a restriction on the response frequency. Even at times, the voltage of the smoothing capacitor can be kept constant. Therefore, the capacity of the smoothing capacitor does not need to be a capacity that takes into account the abnormality of the AC power supply, and as a result, the capacity of the smoothing capacitor can be reduced.

It is a circuit diagram of each embodiment. It is a control block diagram of a 1st embodiment. It is a figure which shows the electric current and voltage at the time of performing control in 1st Embodiment. It is a figure which shows the electric current and voltage when input voltage fluctuates in 1st Embodiment. It is a control block diagram of a 2nd embodiment. It is a control block diagram of a 3rd embodiment. It is a figure which shows the electric current and voltage at the time of performing control in 3rd Embodiment. It is a control block diagram of a 4th embodiment. It is a flowchart of a 4th embodiment. It is an electric power flow in case the electric power command value is larger than predetermined value in 4th Embodiment. In the fourth embodiment, the power flow is when the power command value is equal to or less than a predetermined value. It is a figure which shows the relationship between a capacitor | condenser capacity | capacitance and the allowable amount of a pulsation voltage. It is a figure which shows the relationship between a capacitor | condenser capacity | capacitance and the allowable amount of a pulsation voltage. It is a figure which shows the reduction effect of a capacitor | condenser capacity.

  Hereinafter, each embodiment will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

<First Embodiment>
The power conversion device according to the present embodiment is a power conversion device used for supplying power from an AC power source such as a household power source or a commercial power source to a secondary battery such as an in-vehicle battery.

  FIG. 1 is a circuit diagram of this embodiment. The power conversion apparatus according to this embodiment includes an AC-DC conversion circuit 100, a DC-DC conversion circuit 200, and a control circuit 300. The AC power supply 400 is connected to the input terminal of the AC-DC conversion circuit 100, and the input terminal of the DC-DC conversion circuit 200 is connected to the output terminal of the AC-DC conversion circuit 100. On the other hand, the output terminal of the DC-DC conversion circuit 200 is connected to the secondary battery 500.

  The AC-DC conversion circuit 100 includes a first smoothing reactor 11 including a first bridge circuit 10, a first reactor 11a, and a second reactor 11b. The AC power supply 400 is connected to the first reactor 11 a and the second reactor 11 b of the first smoothing reactor 11 through the input terminal of the AC-DC conversion circuit 200.

  The first bridge circuit 10 is a bridge circuit including a diode D1, a diode D2, a switching element Q1 that is a MOSFET, and a switching element Q2. The diode D1 and the diode D2 are provided on the upper arm on the high voltage side, and the switching element Q1 and the switching element Q2 are provided on the lower arm on the low voltage side. The cathode of the diode D1 is connected to the high voltage side wiring, and the anode is connected to the drain terminal of the switching element Q1 and the first reactor 11a. The cathode of the diode D2 is connected to the high-voltage side wiring, and the anode is connected to the drain terminal of the switching element Q2 and the second reactor 11b. The source terminal of the switching element Q1 and the source terminal of the switching element Q2 are both connected to the low voltage side wiring.

  The DC-DC conversion circuit 200 includes a second bridge circuit 20, a transformer 21 including a first coil 21a and a second coil 21b, a diode bridge circuit 22, a second smoothing reactor 23, a smoothing capacitor 24, Is provided.

  The second bridge circuit 20 is a bridge circuit including switching elements Q3 to Q6 that are MOSFETs. The switching element Q3 and the switching element Q5 are provided on the upper arm on the high voltage side, and the switching element Q4 and the switching element Q6 are provided on the lower arm on the low voltage side. The drain terminal of the switching element Q3 is connected to the high voltage side wiring, and the source terminal is connected to the drain terminal of the switching element Q4 and one end of the first coil 21a. The drain terminal of the switching element Q5 is connected to the high voltage side wiring, and the source terminal is connected to the drain terminal of the switching element Q6 and the other end of the first coil 21a. The source terminal of the switching element Q4 and the source terminal of the switching element Q6 are both connected to the low voltage side wiring.

  The diode bridge circuit 22 is a bridge circuit including diodes D3 to D6. The diode D3 and the diode D5 are provided on the upper arm on the high voltage side, and the diode D4 and the diode D6 are provided on the lower arm on the low voltage side. The cathode of the diode D3 is connected to the high voltage side wiring, and the anode is connected to the cathode of the diode D4 and one end of the second coil 21b. The cathode of the diode D5 is connected to the high voltage side wiring, and the anode is connected to the cathode of the diode D6 and the other end of the second coil 21b. Both the anode of the diode D4 and the anode of the diode D6 are connected to the low-voltage side wiring. The high-voltage side wiring is connected to the positive electrode of the secondary battery 500 via the second smoothing reactor 23 via the output end, and the low-voltage side wiring is connected to the negative electrode of the secondary battery 500 via the output end.

  The smoothing capacitor 24 is provided at the input end of the DC-DC conversion circuit 200, and is connected in parallel with the second bridge circuit 20 by connecting one end to the high voltage side wiring and the other end to the low voltage side wiring. .

  The power converter according to this embodiment includes a first current detector 12 that functions as an AC input current detection unit, a first voltage detector 13 that functions as an AC voltage detection unit, and a second function that functions as an input current detection unit. A current detector 25, a second voltage detector 26 functioning as capacitor voltage detection means, a third current detector 27 functioning as output current detection means, and a third voltage detector 28 are provided.

  The first current detector 12 is provided between the drain terminal of the switching element Q2 of the first bridge circuit 10 and the anode of the diode D2, and between the second reactor 11b of the first smoothing reactor 11, and outputs the reactor current IL. To detect. The first voltage detector 13 is provided at the input end of the AC-DC conversion circuit 100 and detects the input voltage Vac input from the AC power supply 400. The second current detector 25 is provided between the second bridge circuit 20 and the smoothing capacitor 24 and detects an input current Iin input to the second bridge circuit 20 via the smoothing capacitor 24. The second voltage detector 26 is connected in parallel to the smoothing capacitor 24 and detects the capacitor voltage Vc applied to the smoothing capacitor 24. The third current detector 27 is provided on the low voltage wiring side between the diode bridge circuit 22 and the secondary battery 500, and detects the output current Iout output from the DC-DC conversion circuit 200 to the secondary battery 500. . The third voltage detector 28 is connected in parallel to the secondary battery 500 and detects the voltage V0 of the secondary battery.

  The control circuit 300 includes a first control unit 31 and a second control unit 32. The control circuit 300 is provided for maintaining the measured current value and voltage value, the power command value Pin * determined based on the remaining capacity of the secondary battery 500, and the capacitor voltage Vc at a predetermined voltage value. The voltage command value Vc * is input. The 1st control part 31 and the 2nd control part 32 perform calculation using each inputted current value, each voltage value, and each command value. The first control unit 31 transmits a control signal for changing the duty ratio to the switching elements Q1 and Q2, and the second control unit 32 transmits a control signal for changing the duty ratio to the switching elements Q3 to Q6.

  FIG. 2 is a control block diagram of the present embodiment. The first control unit 31 receives the power command value Pin *, the input voltage Vac, the reactor current IL, and the capacitor voltage Vc. Then, the duty ratio of the switching elements Q1 and Q2 of the first bridge circuit 10 is controlled so that the power input from the AC-DC conversion circuit 100 to the DC-DC conversion circuit 200 follows the power command value Pin *.

  First, the effective value of the input voltage Vac is calculated, and the current command value | Iac * | is obtained by dividing the power command value Pin *. On the other hand, | sin θ | is obtained by detecting the phase of Vac and performing absolute value processing. Then, the reactor current command value | IL * | is obtained by multiplying the current command value | Iac * | and | sinθ |. Next, a difference between the obtained reactor current command value | IL * | and the inputted reactor current absolute value | IL | is taken to obtain a reactor current deviation dIL. The obtained reactor current deviation dIL is input to the PI controller, and the deviation between the output and the absolute value of the power supply voltage | Vac | is divided by the capacitor voltage Vc to obtain a required duty ratio. Then, by generating a PWM signal based on the obtained duty ratio, an ON / OFF signal is output to the switching elements Q1, Q2.

  On the other hand, ON / OFF control of the switching elements Q1, Q2 by the first control unit 31 is performed so that the AC-DC conversion circuit 100 also functions as a PFC circuit. Here, when the AC frequency is 60 Hz, the response frequency of the ON / OFF control needs to be about several Hz to 10 Hz in order to suppress harmonics of the input current. Therefore, the response frequency is about several Hz to 10 Hz for the control for causing the power input from the AC-DC conversion circuit 100 to the DC-DC conversion circuit 200 to follow the power command value Pin *.

  The second control unit 32 receives the voltage command value Vc *, the capacitor voltage Vc, and the output current Iout. Then, the switching elements Q3 to Q6 of the second bridge circuit 20 are controlled so that the capacitor voltage Vc follows the voltage command value Vc *.

  First, the current value I_ref is obtained by taking the deviation between the voltage command value Vc * and the capacitor voltage Vc and inputting it to the PI controller. By taking a deviation between the obtained current value I_ref and the output current Iout and inputting it again to the PI controller, the minor loop has feedback control of the capacitor voltage Vc and feedback control of the output current Iout. Thereafter, the required duty ratio is obtained by dividing the output value of the PI controller by the capacitor voltage Vc. Then, an ON / OFF signal is output to the switching elements Q3 to Q6 by generating a PWM signal based on the obtained duty ratio.

  Here, the control of the switching elements Q3 to Q6 by the second control unit 32 is different from the control of the switching elements Q1 and Q2 by the first control unit 31, and the response frequency is not restricted. Therefore, the control of the switching elements Q3 to Q6 by the second control unit 32 can have a response frequency of about 1 kHz to 10 kHz.

  FIG. 3 shows the input current input from the AC power source 400, the capacitor voltage Vc measured by the second voltage detector 26, and the DC-DC conversion circuit 200 when the control according to this embodiment is performed. It is a figure which shows the DC-DC converter output current input into the secondary battery 500. FIG. In FIG. 3, the electric power Pin input from the AC power source 400 is 3400 W, the frequency is 50 Hz, and the average value VH_ave of the maximum value of the input voltage Vac is 380V.

  In the present embodiment, since the capacitor voltage Vc is controlled in the DC-DC conversion circuit 200, the amplitude of the capacitor voltage Vc is suppressed within 20V. On the other hand, the power input to the secondary battery 500 is controlled by the AC-DC conversion circuit 100. Therefore, a pulsating current is generated in the current output from the DC-DC conversion circuit 200 and input to the secondary battery 500.

  FIG. 4 is a graph when the input voltage Vac input from the AC power supply 400 has a voltage drop of 50%. In FIG. 4, the power Pin input from the AC power supply 400 is 3400 W, the frequency is 50 Hz, and the average value VH_ave of the maximum value of the input voltage Vac that is input is 380V.

  Since the capacitor voltage Vc is controlled by the second controller 32, the amplitude of the capacitor voltage Vc is suppressed to within 20V, as in the case of FIG. On the other hand, the peak value of the current output from the DC-DC conversion circuit 200 input to the secondary battery 500 as the power Pin input from the AC power supply 400 temporarily decreases due to the voltage drop of the input voltage Vac. Decreases to about 50%.

  This embodiment has the following effects by the above configuration.

  Since the capacitor voltage Vc applied to the smoothing capacitor 24 is controlled not by the AC-DC converter circuit 100 having a limited response frequency but by the DC-DC converter circuit 200 having no response frequency, the AC power supply 400 is in an abnormal state. In this case, the capacitor voltage Vc can be kept constant. Therefore, the capacity of the smoothing capacitor 24 does not need to be a capacity that takes into account the abnormality of the AC power supply 400, and as a result, the capacity of the smoothing capacitor 24 can be reduced.

Second Embodiment
FIG. 5 is a control block diagram of the present embodiment. The control in this embodiment is performed by the same circuit as that in the first embodiment. In this embodiment, the 1st control part 31 performs control similar to 1st Embodiment, and transmits a control signal to switching element Q1, Q2. On the other hand, in the present embodiment, the control performed by the second control unit 32 is different from the first embodiment.

  The second control unit 32 receives the voltage command value Vc *, the capacitor voltage Vc, and the input current Iin. Then, the switching elements Q3 to Q6 of the second bridge circuit 20 are controlled so that the capacitor voltage Vc follows the voltage command value Vc *.

  First, the current value I_ref is obtained by taking the deviation between the voltage command value Vc * and the capacitor voltage Vc and inputting it to the PI controller. The deviation between the obtained current value I_ref and the input current Iin is taken and input to the peak current controller to obtain the required duty ratio. Then, an ON / OFF signal is output to the switching elements Q3 to Q6 by generating a PWM signal based on the obtained duty ratio.

  In this embodiment, the responsiveness of the current control of the DC-DC conversion circuit 200 can be further increased by the above configuration. As a result, the responsiveness of the voltage control of the capacitor voltage Vc can be further increased.

<Third Embodiment>
FIG. 6 is a control block diagram of the present embodiment. The control in this embodiment is performed by the same circuit as that in the first embodiment. In this embodiment, the 1st control part 31 performs control similar to 1st Embodiment and 2nd Embodiment, and transmits a control signal to switching element Q1, Q2. On the other hand, in the present embodiment, the control performed by the second control unit 32 is different from the first embodiment and the second embodiment.

  The second control unit 32 receives the voltage command value Vc *, the capacitor voltage Vc, and the input current Iin. Then, the switching elements Q3 to Q6 of the second bridge circuit 20 are controlled so that the capacitor voltage Vc follows the voltage command value Vc *.

  First, the current value I_ref is obtained by taking the deviation between the voltage command value Vc * and the capacitor voltage Vc and inputting it to the PI controller. The obtained current value I_ref is input to the limiter, and the upper limit value and the lower limit value are limited within a predetermined value. Thereafter, the deviation between the current value I_ref after the limiter and the input current Iin is taken and input to the peak current controller to obtain the required duty ratio. Then, an ON / OFF signal is output to the switching elements Q3 to Q6 by generating a PWM signal based on the obtained duty ratio.

  7 shows the input current input from the AC power source 400, the capacitor voltage Vc measured by the second voltage detector 26, and the DC-DC conversion circuit 200 when the control according to this embodiment is performed. It is a figure which shows the DC-DC converter output current input into the secondary battery 500. FIG. In FIG. 7, the electric power Pin input from the AC power source 400 is 3400 W, the frequency is 50 Hz, and the average value VH_ave of the maximum value of the input voltage Vac is 380V.

  In the present embodiment, an upper limit value and a lower limit value are provided for the current value input to the secondary battery 500 by a limiter. Therefore, the pulsation of the current output from the DC-DC conversion circuit 200 and input to the secondary battery 500 can be kept within a predetermined range.

  In the present embodiment, the current flowing through the diode bridge circuit 22 and the second smoothing reactor 23 constituting the DC-DC conversion circuit 200 can be kept within a predetermined range by the above configuration. Accordingly, it is possible to employ a diode having a smaller rated current for each of the diodes D3 to D6 and the second smoothing reactor 23 constituting the diode bridge circuit 22.

<Fourth embodiment>
FIG. 8 is a control block diagram of the present embodiment. The control in this embodiment is performed by the same circuit as that in the first embodiment. In the present embodiment, the control is switched according to whether or not the power command value Pin * is greater than the threshold value Pref.

  First, control when the power command value Pin is larger than the threshold value Pref will be described. In this case, the control performed by the first control unit 31 and the control performed by the second control unit 32 are the same controls as in the third embodiment. Then, an ON / OFF signal is transmitted from the first control unit 31 to the switching elements Q1, Q2, and an ON / OFF signal is transmitted from the second control unit 32 to the switching elements Q3-Q6.

  Next, control when the power command value Pin * is equal to or less than the threshold value Pref will be described. The first control unit 31 receives a voltage command value Vc *, an input voltage Vac, a reactor current IL, and a capacitor voltage Vc. Then, the duty ratio of the switching elements Q1 and Q2 of the first bridge circuit 10 is controlled so that the capacitor voltage Vc follows the voltage command value Vc *.

  First, the current command value | Iac * | is obtained by taking the difference between the voltage command value Vc * and the capacitor voltage Vc and inputting it to the PI controller. On the other hand, | sin θ | is obtained by detecting the phase of Vac and performing absolute value processing. Then, the reactor current command value | IL * | is obtained by multiplying the current command value | Iac * | and | sinθ |. Next, a difference between the obtained reactor current command value | IL * | and the inputted reactor current absolute value | IL | is taken to obtain a reactor current deviation dIL. The obtained reactor current deviation dIL is input to the PI controller, and the deviation between the output and the absolute value of the power supply voltage | Vac | is divided by the capacitor voltage Vc to obtain a required duty ratio. Then, by generating a PWM signal based on the obtained duty ratio, an ON / OFF signal is output to the switching elements Q1, Q2.

  The second control unit 32 receives the power command value Pin *, the capacitor voltage Vc, and the input current Iin. Then, the switching elements Q3 to Q6 of the second bridge circuit 20 are controlled so that the power output from the DC-DC conversion circuit 200 follows the power command value Pin *.

  First, the deviation between the power command value Pin * and the capacitor voltage Vc is taken to obtain the current value I_ref. The deviation between the obtained current value I_ref and the input current Iin is taken and input to the peak current controller to obtain the required duty ratio. Then, an ON / OFF signal is output to the switching elements Q3 to Q6 by generating a PWM signal based on the obtained duty ratio.

  FIG. 9 is a flowchart of this embodiment. The control according to this flowchart is executed at a predetermined cycle. First, in S101, it is determined whether or not a charging request has been made. In S101, if it is not determined that a charge request has been made, a series of processing ends. On the other hand, if it is determined in S101 that a charge request has been made, it is determined in S102 whether or not the power command value Pin * is greater than the threshold value Pref. When it is determined in S102 that the power command value Pin * is greater than the threshold value Pref, in S103, the DC-DC conversion circuit 200 performs control to set the capacitor voltage Vc to the voltage command value Vc *, thereby performing AC-DC conversion. The circuit 100 controls the output power to be a power command value Pin *. On the other hand, when it is determined in S102 that the power command value Pin * is equal to or less than the threshold value Pref, in S104, the AC-DC conversion circuit 100 performs control to set the capacitor voltage Vc to the voltage command value Vc *, thereby performing DC-DC conversion. The circuit 200 controls the output power to be a power command value Pin *.

  After the control in S103 or the control in S104, it is determined in S105 whether the charging is finished. That is, it is determined whether or not the capacity of the secondary battery 500 has reached a predetermined value or more. If it is determined in S105 that the capacity of the secondary battery 500 is not equal to or greater than the predetermined value, the charging control is continued. On the other hand, when it is determined in S105 that the capacity of the secondary battery 500 has become equal to or greater than the predetermined value, the series of processes is terminated.

  FIG. 10 shows that when the power command value Pin * is larger than the threshold value Pref, that is, the DC-DC conversion circuit 200 controls the capacitor voltage Vc to be the voltage command value Vc *, and the AC-DC conversion circuit 100 It is a figure which shows an electric power flow at the time of performing control which uses output electric power as electric power command value Pin *.

  When the electric power command value Pin * is a value larger than the threshold value Pref, the voltage control of the capacitor voltage Vc is performed by the DC-DC conversion circuit 200 with no limitation on the response frequency. Therefore, the capacitor voltage Vc can be controlled so that no pulsating voltage is generated. On the other hand, since current control is not performed in the DC-DC conversion circuit 200, the secondary battery 500 is charged with pulsating electric power.

  FIG. 11 illustrates a case where the power command value Pin * is equal to or less than the threshold value Pref, that is, the AC-DC conversion circuit 100 performs control to set the capacitor voltage Vc to the voltage command value Vc *, and the DC-DC conversion circuit 200 outputs power It is a figure which shows an electric power flow at the time of performing control which makes electric power command value Pin *.

  When the power command value Pin * is equal to or less than the threshold value Pref, the AC-DC conversion circuit 100 performs PFC operation and voltage control of the capacitor voltage Vc. Here, as described above in the first embodiment, the response frequency of the AC-DC conversion circuit 100 is about several Hz to 10 Hz, so that the response is low compared to the frequency of the capacitor voltage Vc. As a result, the capacitor voltage Vc pulsates with a component twice the frequency of the AC power supply 400. Since the smoothing capacitor 24 absorbs pulsation, the smaller the capacity of the smoothing capacitor 24, the larger the pulsation.

  On the other hand, the DC-DC conversion circuit 200 controls the current based on the power command value Pin * to flow. Therefore, since the current flowing into the secondary battery 500 is constant, the secondary battery 500 is charged with DC power.

  FIG. 12 shows the capacity of the smoothing capacitor 24 when the AC-DC conversion circuit 100 performs control to set the capacitor voltage Vc to the voltage command value Vc * regardless of the value of the power command value Pin *. It is a graph which shows the relationship with permissible pulsation voltage (DELTA) V. In FIG. 12, the input power Pin is 3400 W, the frequency is 50 Hz, and the average value VH_ave of the maximum value of the input AC power is 380 V. In this case, if the capacity of the smoothing capacitor 24 is selected so that the maximum value of the pulsating voltage ΔV is 80 V, the capacity is required to be 370 μF.

  On the other hand, FIG. 13 is a graph showing the relationship between the capacity of the smoothing capacitor 24 and the allowable pulsation voltage ΔV when the control according to the present embodiment is performed. In the present embodiment, as described above, the AC-DC conversion circuit 100 controls the capacitor voltage Vc to be the voltage command value Vc * only when the power command value Pin * is equal to or less than the threshold value Pref. Therefore, in the power conversion device according to the present embodiment, the capacity of the smoothing capacitor 24 may be selected so that the pulsation voltage ΔV is 80 V when the power command value Pin * is equal to or less than the threshold value Pref. In FIG. 13, the input power Pin is 600 W, the frequency is 50 Hz, and the average value VH_ave of the maximum value of the input AC power is 380 V. In this case, if the capacity of the smoothing capacitor 24 is selected so that the pulsation voltage ΔV is 80 V, the capacity is 65 μF.

  FIG. 14 is a diagram illustrating the effect of reducing the capacitance of the smoothing capacitor 24 in the present embodiment. As shown in FIG. 12 and FIG. 13, when performing the control according to the present embodiment, if the capacitance of the smoothing capacitor 24 is selected so that the pulsation voltage ΔV is 80 V, it is 65 μF. On the other hand, when the control according to the present embodiment is not performed, 370 μF is required when the capacity of the smoothing capacitor 24 is selected so that the pulsation voltage ΔV is 80V.

  With the above-described configuration, the power output from the DC-DC converter can be set to DC power without pulsation at the time of push-in charging in which the power output from the output terminal is reduced. Therefore, the accuracy when the battery is fully charged can be improved and the capacity of the smoothing capacitor 24 can be reduced.

<Modification>
In the third embodiment, the upper limit value and the lower limit value of the input current Iin are provided by the limiter. However, only the upper limit value of the input current Iin may be provided. Further, only the lower limit value may be provided.

  In the fourth embodiment, when the power command value Pin * is greater than the threshold value Pref, the same control as in the third embodiment is performed. However, the same control as in the first embodiment may be performed, You may perform control similar to 2 embodiment.

  In the first embodiment, the second control unit 32 performs calculation using the output current Iout. However, the calculation may be performed using the input current Iin instead of the output current Iout. In the second to fourth embodiments, the second controller 32 calculates using the input current Iin. However, the calculation may be performed using the output current Iout instead of the input current Iin.

  In each embodiment, the first bridge circuit 10 is configured by the two diodes D1 and D2 and the two switching elements Q1 and Q2. However, the first bridge circuit 10 may be configured by four switching elements.

  In each embodiment, the second bridge circuit 20 is configured by the four switching elements Q3 to Q6, but may be a half bridge circuit configured by the two switching elements.

  In each embodiment, the switching element is a MOSFET, but a field effect transistor other than a MOSFET can also be used. Each switching element may be a transistor such as a bipolar transistor. In this case, in each of the above embodiments, the drain may be read as a collector, and the source may be read as an emitter.

  24 ... smoothing capacitor, 25 ... second current detector, 26 ... second voltage detector, 27 ... third current detector, 100 ... AC-DC conversion circuit, 200 ... DC-DC conversion circuit, 300 ... control circuit, 400 ... AC power source, 500 ... Secondary battery, Q1-Q6 ... Switching element.

Claims (6)

A power conversion device for charging a secondary battery (500) with an AC power source (400),
An AC-DC converter (100) having an input terminal to which the AC power supply is connected and a plurality of switching elements (Q1, Q2);
A DC-DC converter (200) having an output terminal connected to the secondary battery and a plurality of switching elements (Q3 to Q6) and connected to the AC-DC converter;
A smoothing capacitor (24) connected between the AC-DC converter and the DC-DC converter;
Input current detection means (25) for detecting a current flowing between the smoothing capacitor and the DC-DC converter, and output current detection means (27) for detecting a current output from the DC-DC converter. And at least one of
Capacitor voltage detection means (26) for detecting the voltage of the smoothing capacitor;
A control circuit (300) for performing ON / OFF control of the switching element of the AC-DC converter and the switching element of the DC-DC converter;
The control circuit, based on the current detected by the input current detection means or the current detected by the output current detection means, the voltage detected by the capacitor voltage detection means, and the input voltage command value, -A power converter, wherein the voltage of the smoothing capacitor is controlled by changing the duty ratio of the ON / OFF signal of the switching element of the DC converter. The AC-DC converter has AC input current detection means (12) for detecting current input from the AC power supply, and AC voltage detection means (13) for detecting voltage input from the AC power supply. And
The control circuit controls the switching element of the AC-DC converter based on the current detected by the AC input current detection unit, the voltage detected by the AC voltage detection unit, and the input power command value. The power converter according to claim 1, wherein current control based on a power command value is performed by changing a duty ratio of an ON / OFF signal. The control circuit performs current control based on the power command value by controlling the duty ratio of the ON / OFF signal to the switching element of the DC-DC converter when the power command value is equal to or less than a predetermined value. The power converter according to claim 2, wherein the voltage of the smoothing capacitor is controlled by controlling the duty ratio of the ON / OFF signal of the switching element of the AC-DC converter. The control circuit controls the voltage of the smoothing capacitor by voltage feedback control in which a minor loop has feedback control of the current detected by the input current detection unit or the current detected by the output current detection unit. The power converter device of any one of Claims 1-3.   5. The power conversion device according to claim 1, wherein the control circuit limits an upper limit value of a current output from the DC-DC converter to a predetermined value. 6.   The said control circuit restrict | limits the lower limit of the electric current output from the said DC-DC converter to a predetermined value, The power converter device of any one of Claims 1-5 characterized by the above-mentioned.

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