JP5802073B2 - Bidirectional power converter - Google Patents

Description

  The present invention relates to a bidirectional power converter.

  2. Description of the Related Art Conventionally, there is a power conversion device that converts a DC voltage into an AC voltage. Generally, a DC / DC converter that boosts or lowers a DC voltage, and a DC / DC that converts a DC voltage output from the DC / DC converter into an AC voltage. An AC converter (see, for example, Patent Document 1).

  For example, the power conversion device B illustrated in FIG. 9 includes a DC / DC conversion unit 101 and a DC / AC conversion unit 102.

  The DC / DC conversion unit 101 includes a switching circuit 1011, a high-frequency transformer Tr 101, a rectifier circuit 1012, a detection unit 1013, and a control circuit 1014.

  The switching circuit 1011 receives the DC voltage Vdc101 of the DC power supply E100 and drives a switching element (not shown) on and off to periodically invert the polarity of the current supplied from the DC power supply E100 and Supply to the primary winding. An induced voltage is generated in the secondary winding of the high-frequency transformer Tr101 and is rectified by the rectifier circuit 1012. A DC voltage Vdc102 is generated between the output terminals of the rectifier circuit 1012. The DC voltage Vdc102 is a voltage obtained by stepping up or down the DC voltage Vdc101.

  The detection unit 1013 detects the DC voltage Vdc102, and the control circuit 1014 performs switching control of the switching circuit 1011 so that the detected value of the DC voltage Vdc102 matches the target voltage. That is, the control circuit 1014 performs feedback control of the DC voltage Vdc102 to the target voltage.

  Next, the DC / AC conversion unit 102 includes a switching circuit 1021, a filter circuit 1022, a detection unit 1023, and a control circuit 1024.

  The switching circuit 1021 receives the DC voltage Vdc102 as an input, and converts the DC voltage Vdc102 into an AC voltage by driving a switching element (not shown) on and off. Then, the AC voltage output from the switching circuit 1021 passes through the filter circuit 1022, and the AC voltage Vac101 in which an unnecessary frequency band is attenuated is output from the filter circuit 1022.

  The detecting unit 1023 detects the AC voltage Vac101, and the control circuit 1024 performs switching control of the switching circuit 1021 so that the detected value of the AC voltage Vac101 matches the target voltage. That is, the control circuit 1024 performs feedback control of the AC voltage Vac101 to the target voltage.

  As described above, the power conversion apparatus B includes detection units 1013 and 1023 that detect outputs of the DC / DC conversion unit 101 and the DC / AC conversion unit 102, and control circuits 1014 and 1024 that perform feedback control based on the detection results. And.

JP 2010-44979 A

  As described above, in a power conversion device including a DC / DC conversion unit and a DC / AC conversion unit, improvement in power efficiency, reduction in the number of components, and downsizing are required. Furthermore, a function as a bidirectional DC / AC converter having not only a DC / AC conversion function for converting the DC voltage Vdc101 into the AC voltage Vac101 but also an AC / DC conversion function for converting the AC voltage Vac101 into the DC voltage Vdc101. Is also sought.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a DC / DC conversion unit and a DC / AC conversion unit that perform bidirectional voltage conversion to ensure the accuracy of the bidirectional output voltage. In addition, an object is to provide a bidirectional power conversion device that can improve power efficiency, reduce the number of components, and reduce the size.

The bidirectional power converter of the present invention is provided between the first DC circuit and the second DC circuit, and is a DC voltage obtained by DC / DC conversion of the DC voltage of the first DC circuit by open loop control. Is output to the second DC circuit, and a DC voltage obtained by DC / DC conversion of the DC voltage of the second DC circuit by open loop control is output to the first DC circuit. A DC / DC converter that performs bidirectional voltage conversion by switching between the operation and a second DC circuit and an AC circuit, and the DC voltage of the second DC circuit is DC-controlled by feedback control. A third operation for outputting an AC voltage obtained by / AC conversion to the AC circuit and a fourth operation for outputting a DC voltage obtained by AC / DC conversion of the AC voltage of the AC circuit by feedback control to the second DC circuit. And a DC / AC converter that performs bidirectional voltage conversion, the DC / DC converter performs the first operation, and the DC / AC converter performs the third operation. The DC mode is configured to be switchable between a first mode and a second mode in which the DC / DC converter performs the second operation and the DC / AC converter performs the fourth operation, and the DC The / AC converter is a first output detector that detects an AC voltage of the AC circuit, and a second that detects both the DC voltage of the first DC circuit and the DC voltage of the second DC circuit. Feedback control of the output voltage of the output detection unit and the AC voltage output to the AC circuit during the third operation in a direction in which the detection value of the first output detection unit matches a predetermined target value, The DC voltage output to the second DC circuit during operation is the second voltage The detection value of the output detection unit is characterized by comprising a control circuit for feedback control in a direction that matches a predetermined target value.

  In this invention, the control circuit feedback-controls the DC voltage output to the second DC circuit during the fourth operation in the direction in which the DC voltage of the second DC circuit matches the first target value. After that, it is preferable to perform feedback control in a direction in which the DC voltage of the first DC circuit matches the second target value.

  As described above, the present invention includes the DC / DC conversion unit and the DC / AC conversion unit that perform bidirectional voltage conversion, ensures the accuracy of the bidirectional output voltage, improves the power efficiency, and There is an effect that the number of parts can be reduced and the size can be reduced.

It is a block block diagram which shows the bidirectional | two-way power converter device of Embodiment 1. It is a circuit block diagram which shows a DC / DC conversion part same as the above. It is a circuit block diagram which shows a DC / AC conversion part same as the above. It is a wave form diagram which shows the voltage and electric current in a diode. FIG. 3 is a waveform diagram showing voltage and current in the diode of the first embodiment. It is a wave form diagram which shows a resonance current same as the above. It is a block block diagram which shows the bidirectional | two-way power converter device of Embodiment 2. It is a block block diagram which shows the bidirectional | two-way power converter device of Embodiment 3. It is a block block diagram which shows the conventional power converter device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a block configuration of a bidirectional power conversion device A1 of the present embodiment, and the bidirectional power conversion device A1 includes a DC / DC conversion unit 1 and a DC / AC conversion unit 2. The DC / DC conversion unit 1 and the DC / AC conversion unit 2 are internally connected through a DC circuit W2 (second DC circuit). The DC / DC converter 1 is connected between a DC electric circuit W1 (first DC electric circuit) and a DC electric circuit W2 (second DC electric circuit) from the outside. The DC / AC converter 2 is connected between the DC electric circuit W2 and the AC electric circuit W3 from the outside. The DC voltage of the DC circuit W1 is defined as a DC voltage Vdc1, the DC voltage of the DC circuit W2 is defined as a DC voltage Vdc2, and the AC voltage of the AC circuit W3 is defined as an AC voltage Vac1.

  The DC / DC conversion unit 1 includes a rectification switching circuit 11, a high frequency transformer Tr1, and a rectification switching circuit 12. FIG. 2 shows a circuit configuration of the DC / DC conversion unit 1.

  The rectifying switching circuit 11 includes a parallel circuit of switching elements Q11 and Q12 connected in series and switching elements Q13 and Q14 connected in series. Each of switching elements Q11 to Q14 has capacitors C11 to C14 connected in parallel, and diodes D11 to D14 connected in reverse parallel. A primary winding N1 of the high-frequency transformer Tr1 is connected between the connection midpoints of the switching elements Q11 and Q12 and the switching elements Q13 and Q14. A capacitor C15 is connected in parallel to the series circuit of the switching elements Q11 and Q12.

  Then, the drive circuit K11 drives the switching elements Q11 and Q14 and the switching elements Q12 and Q13 alternately on and off, so that the rectifying switching circuit 11 operates as a switching circuit that outputs the high-frequency transformer Tr1 side. Further, the driving circuit K11 maintains the switching elements Q11 to Q14 in the off state, so that the rectifying switching circuit 11 operates as a rectifying circuit having the high frequency transformer Tr1 side as an input.

  Next, an inductor Ls and a capacitor Cs are connected in series to the secondary winding N2 of the high-frequency transformer Tr1, and a series resonant circuit K2 is formed by the inductor Ls, the capacitor Cs, and the secondary winding N2 of the high-frequency transformer Tr1. Composed.

  Next, the rectifying switching circuit 12 includes a parallel circuit of switching elements Q21 and Q22 connected in series and switching elements Q23 and Q24 connected in series. Each of switching elements Q21 to Q24 has capacitors C21 to C24 connected in parallel, and diodes D21 to D24 connected in reverse parallel. A series resonant circuit K2 is connected between the connection midpoints of the switching elements Q21, Q22 and the switching elements Q23, Q24. A capacitor C25 is connected in parallel to the series circuit of the switching elements Q21 and Q22.

  The drive circuit K21 drives the switching elements Q21 and Q24 and the switching elements Q22 and Q23 alternately on and off, so that the rectifying switching circuit 12 operates as a switching circuit that outputs the high frequency transformer Tr1 side. Further, the drive circuit K21 maintains the switching elements Q21 to Q24 in the off state, so that the rectification switching circuit 12 operates as a rectification circuit having the high frequency transformer Tr1 side as an input.

  In the DC / DC converter 1 configured as described above, the rectifier switching circuit 11 operates as a switching circuit, and the rectifier switching circuit 12 operates as a rectifier circuit, so that the DC / AC converter 2 side serves as an output. It functions as a DC / DC converter. In this case, the direct current power source E1 connected to the direct current circuit W1 serves as an input of the DC / DC converter 1, and the direct current voltage Vdc2 obtained by stepping up or down the direct current voltage Vdc1 (DC / DC conversion) is output from the DC / DC converter 1. (First operation).

  Further, the DC / DC converter 1 operates as a DC / DC converter having the DC / AC converter 2 side as an input by the rectifier switching circuit 11 operating as a rectifier circuit and the rectifier switching circuit 12 operating as a switching circuit. Function. In this case, the DC voltage Vdc2 input from the DC / AC converter 2 becomes the input of the DC / DC converter 1, and the DC voltage Vdc1 obtained by stepping up or down (DC / DC conversion) the DC voltage Vdc2 is the DC / DC converter. 1 (second operation).

  That is, the DC / DC conversion unit 1 has a bidirectional DC / DC conversion function, and the input / output direction can be switched by switching each operation of the drive circuits K11 and K21 in conjunction with each other.

  Here, the drive circuits K11 and K21 are switching elements having a predetermined switching frequency (on period, off period) related to each value of the DC voltages Vdc1 and Vdc2 input / output to / from the DC / DC converter 1. Q11 to Q14 and Q21 to Q24 are turned on / off. That is, the DC / DC converter 1 generates a DC voltage Vdc2 obtained by boosting or stepping down the DC voltage Vdc1 or a DC voltage Vdc1 obtained by boosting or stepping down the DC voltage Vdc2 by open loop control. Therefore, a detection unit for detecting the input / output state of the DC / DC conversion unit 1 and a control circuit for feedback control of the DC voltages Vdc1 and Vdc2 are not required, improving power efficiency by reducing power consumption and reducing the number of components. Miniaturization can be achieved.

  Next, the DC / AC conversion unit 2 includes a switching circuit 21, a filter circuit 22, a detection unit 23 (first output detection unit), a control circuit 24, and a detection unit 25 (second output detection unit). FIG. 3 shows a circuit configuration of the DC / AC converter 2.

  The switching circuit 21 includes a parallel circuit of switching elements Q31 and Q32 connected in series and switching elements Q33 and Q34 connected in series. In addition, capacitors C31 to C34 are connected in parallel to switching elements Q31 to Q34, and diodes D31 to D34 are connected in reverse parallel. A filter circuit 22 is connected between the connection midpoints of the switching elements Q31 and Q32 and the switching elements Q33 and Q34. A capacitor C35 is connected in parallel to the series circuit of the switching elements Q31 and Q32.

  The filter circuit 22 includes inductors L41 and L42 and a capacitor C41. Inductor L41 has one end connected to the midpoint of connection between switching elements Q33 and Q34, inductor L42 has one end connected to the midpoint of connection between switching elements Q31 and Q32, and capacitor C41 includes each of inductor L41 and inductor L42. Connected between the ends.

  Then, the drive circuit K31 drives the switching elements Q31 and Q34 and the switching elements Q32 and Q33 alternately on and off, so that the switching circuit 21 operates as a DC / AC inverter that outputs the filter circuit 22 side. . In this case, the DC voltage Vdc2 output from the DC / DC converter 1 becomes the input of the DC / AC converter 2, and the DC voltage Vdc2 is DC / AC converted into the AC voltage Vac1 and output (third operation).

  Further, the driving circuit K31 maintains the switching elements Q31 and Q33 in the off state and intermittently turns on the switching elements Q32 and Q34, so that the switching circuit 21 has an AC / DC converter with the filter circuit 22 side as an input. Works as. In this case, the AC power supply E2 connected to the AC power circuit W3 serves as an input to the DC / AC conversion unit 2, and AC / DC converts the AC voltage Vac1 into the DC voltage Vdc2 and outputs it (fourth operation).

  That is, the DC / AC conversion unit 2 has a bidirectional DC / AC conversion function, and the input / output direction can be switched by the control circuit 24 switching the operation of the drive circuit K31.

  Therefore, the DC / DC converter 1 functions as a DC / DC converter that converts the DC voltage Vdc1 into the DC voltage Vdc2, and the DC / AC converter 2 serves as a DC / AC inverter that converts the DC voltage Vdc2 into the AC voltage Vac1. When functioning, the bidirectional power converter A1 functions as a DC / AC inverter (first mode). Further, the DC / AC converter 2 functions as an AC / DC converter that converts the AC voltage Vac1 into the DC voltage Vdc2, and the DC / DC converter 1 functions as a DC / DC converter that converts the DC voltage Vdc2 into the DC voltage Vdc1. When functioning, bidirectional power converter A1 functions as an AC / DC converter (second mode). In the bidirectional power converter A1, the first mode and the second mode are configured to be switchable.

  The detection unit 23 detects the AC voltage Vac1, and the control circuit 24 sets the detected value of the AC voltage Vac1 to the target voltage when the bidirectional power converter A1 functions as a DC / AC inverter. Switching control of the switching circuit 21 is performed so as to match. That is, the control circuit 24 performs feedback control of the AC voltage Vac1 to the target voltage.

  The detecting unit 25 detects the DC voltage Vdc2, and the control circuit 24 sets the detected value of the DC voltage Vdc2 to the target voltage when the bidirectional power converter A1 functions as an AC / DC converter. Switching control of the switching circuit 21 is performed so as to match. That is, the control circuit 24 performs feedback control of the DC voltage Vdc2 to the target voltage.

  Thus, the bidirectional power converter A1 has a bidirectional DC / AC conversion function, the DC / DC converter 1 performs open loop control, and the DC / AC converter 2 performs feedback control. .

  Therefore, even when the bidirectional power converter A1 functions as a DC / AC inverter, even if the DC voltage Vdc2 output from the DC / DC converter 1 fluctuates, the AC voltage output from the DC / AC converter 2 Vac1 can be matched to the target voltage. Further, when the bidirectional power converter A1 functions as an AC / DC converter, the DC voltage Vdc2 output from the DC / AC converter 2 is feedback controlled, so that the DC / DC converter that is open-controlled. The DC voltage Vdc1 output by 1 can also be controlled to be substantially constant.

  That is, in the bidirectional power conversion device A1 including the DC / DC converter 1 and the DC / AC converter 2 that perform bidirectional voltage conversion, the accuracy of the bidirectional output voltage can be ensured. Further, the feedback control means of the DC / DC conversion unit 1 is not required, and it is possible to improve power efficiency by reducing power consumption, reduce the number of parts, and reduce the size.

  Further, by providing the series resonant circuit K2, the rectifying switching circuit 11 and the bidirectional power converter A1 function as an AC / DC converter when the bidirectional power converter A1 functions as a DC / AC inverter. When the rectifying switching circuit 12 operates as an LLC resonant converter. Therefore, each switching loss of switching elements Q11-Q14 and switching elements Q21-Q24 can be reduced, and further increase in efficiency can be achieved.

  Next, when the rectification switching circuit 12 is operating as a switching circuit, the relationship between the switching period of the switching elements Q21 to Q24 and the resonance current by the series resonance circuit K2 will be described.

  FIG. 4 shows the voltage between the cathode and the anode in the diodes D11 to D14 (hereinafter referred to as the diode DA when the diodes D11 to D14 are not distinguished) when the bidirectional power converter A1 functions as an AC / DC converter. A voltage waveform Y1 of Vk and a current waveform Y2 of the forward current If are shown. Note that the resonance current of the series resonance circuit K2 flows through the switching elements Q21 to Q24 (hereinafter referred to as switching element QA when the switching elements Q21 to Q24 are not distinguished), and the waveform of this resonance current is the forward current If. Is substantially the same as the current waveform Y2.

  After the switching element QA is turned on, the resonance current of the series resonance circuit K2 flows (see current waveform Y2 in FIG. 4). When the switching element QA is turned off while the resonance current is flowing, the current flowing through the diode DA also decreases rapidly, and the reverse recovery current Ir flows through the diode DA (see FIG. 4). In the diode DA, the reverse recovery current Ir causes power loss.

  Therefore, in this embodiment, the relationship between each switching period of the switching element QA and the resonance current is set as shown in FIG. FIG. 5 shows a voltage waveform Y3 of the cathode-anode voltage Vk and a current waveform Y4 of the forward current If in the diode DA. When the switching element QA is turned on, the resonance current flowing through the switching element QA increases. descend. When the period from when the switching element QA is turned on until the resonance current falls below a predetermined current near “0” is defined as the resonance period To, the resonance period To is set to be equal to or less than the on period Ts of the switching element QA. The That is, by adjusting the constants of the inductor Ls and the capacitor Cs of the series resonance circuit K2, the relationship between the resonance period To of the resonance current and the ON period Ts of the switching element QA is set to [To ≦ Ts] in advance. .

  Therefore, when the switching element QA is turned off, the current flowing through the diode DA becomes substantially zero, and the reverse recovery current Ir generated in the diode DA is suppressed, so that the power loss in the diode DA is reduced and the power efficiency is further increased. Improvements can be made.

  FIG. 6 shows current waveforms Y5 and Y6 of the resonance current. The current waveform Y5 is a current waveform when the resonance frequency of the resonance current is increased and set to a short resonance period To1, and the current waveform Y6. These are current waveforms when the resonance frequency of the resonance current is lowered and set to the long resonance period To2. The peak value of the current waveform Y5 corresponding to the short resonance period To1 is higher than the peak value of the current waveform Y6 corresponding to the long resonance period To2, and the power due to the on-resistance of the switching element QA becomes shorter as the resonance period To becomes shorter. Loss increases.

  Therefore, the relationship between the resonance period To and the ON period Ts of the switching element QA is set to [0.7 · Ts ≦ To ≦ Ts]. In this case, the power loss due to the on-resistance of the switching element QA can be suppressed, and the power efficiency can be further improved.

  Even when the rectifying switching circuit 11 operates as a switching circuit, the same effect can be obtained by setting the relationship between the switching period of the switching elements Q11 to Q14 and the resonance current by the series resonance circuit K2 in the same manner as described above. Can do.

(Embodiment 2)
FIG. 7 shows a block configuration of the bidirectional power conversion device A2 of the present embodiment. The same reference numerals are given to the same configurations as those of the first embodiment, and description thereof will be omitted.

The DC / AC conversion unit 2 of the present embodiment includes a detection unit 26 (second output detection unit) that detects the DC voltage Vdc1. The control circuit 24 then switches the switching circuit 21 so that the detected value of the DC voltage Vdc1 matches the target voltage when the bidirectional power converter A2 functions as an AC / DC converter (second mode). Switching control. That is, the control circuit 24 feedback-controls the DC voltage Vdc1 to the target voltage. When the bidirectional power converter A2 having such a configuration functions as an AC / DC converter, the DC / AC converter 2 performs feedback control of the DC voltage Vdc1 which is the final output, so that the DC voltage Vdc1 is stabilized and the output accuracy of the DC voltage Vdc1 is improved.

(Embodiment 3)
FIG. 8 shows a block configuration of the bidirectional power conversion device A3 of the present embodiment. The same reference numerals are given to the same configurations as those of the first embodiment, and description thereof will be omitted.

  The DC / AC conversion unit 2 of the present embodiment includes a detection unit 25 (second output detection unit) that detects the DC voltage Vdc2 and a detection unit 26 (second output detection unit) that detects the DC voltage Vdc1. Both are provided.

  Then, when the bidirectional power converter A3 functions as an AC / DC converter (second mode), the control circuit 24 performs two feedback controls on the switching circuit 21.

  The first feedback control by the control circuit 24 is performed by the switching circuit so that the detected value of the DC voltage Vdc2 coincides with the first target voltage when the bidirectional power converter A3 functions as an AC / DC converter. 21 is subjected to switching control. That is, the control circuit 24 performs feedback control on the DC voltage Vdc2 so that the DC voltage Vdc2 matches the first target voltage.

  The second feedback control by the control circuit 24 is performed by the switching circuit so that the detected value of the DC voltage Vdc1 matches the second target voltage when the bidirectional power converter A3 functions as an AC / DC converter. 21 is subjected to switching control. That is, the control circuit 24 performs feedback control of the DC voltage Vdc2 so that the DC voltage Vdc1 matches the second target voltage.

  Here, since the DC voltage Vdc1 is generated by DC / DC conversion of the DC voltage Vdc2 output from the DC / AC conversion unit 2 by the DC / DC conversion unit 1, the second feedback control by the control circuit 24 is performed. The response is slower than in the first feedback control.

  Thus, the control circuit 24 causes the DC voltage Vdc2 to coincide with the first target voltage (or the vicinity thereof) by the first feedback control, and then the DC voltage Vdc1 is set to the second voltage by the second feedback control. Match the target voltage.

  The bidirectional power converter A3 having such a configuration can stabilize the transition operation of the feedback control process in the control circuit 24 of the DC / AC converter 2 when functioning as an AC / DC converter. . That is, it leads to further stabilization of the DC voltage Vdc1 and improvement of output accuracy of the DC voltage Vdc1.

A1 Bidirectional power converter 1 DC / DC converter 11 Rectifier switching circuit 12 Rectifier switching circuit Tr1 High frequency transformer 2 DC / AC converter 21 Switching circuit 22 Filter circuit 23 Detector (first output detector)
24 control circuit 25 detector (second output detector)
W1, W2 DC circuit W3 AC circuit

Claims (2)

Provided between the first DC circuit and the second DC circuit, and outputs a DC voltage obtained by DC / DC conversion of the DC voltage of the first DC circuit by open loop control to the second DC circuit. A bidirectional voltage is switched between a first operation and a second operation in which a DC voltage obtained by DC / DC conversion of the DC voltage of the second DC circuit by open loop control is output to the first DC circuit. A DC / DC converter for performing the conversion;
A third operation that is provided between the second DC circuit and the AC circuit and outputs an AC voltage obtained by performing DC / AC conversion of the DC voltage of the second DC circuit by feedback control to the AC circuit; A DC / AC converter that performs bidirectional voltage conversion by switching to a fourth operation of outputting a DC voltage obtained by AC / DC conversion of the AC voltage of the AC circuit to the second DC circuit by feedback control. ,
A first mode in which the DC / DC converter performs the first operation and the DC / AC converter performs the third operation; and the DC / DC converter performs the second operation. And the DC / AC converter is configured to be switchable between a second mode in which the fourth operation is performed ,
The DC / AC conversion unit detects a first output detection unit that detects an AC voltage of the AC circuit, and a DC voltage of the first DC circuit and a DC voltage of the second DC circuit. Feedback control of the second output detection unit and the AC voltage output to the AC circuit during the third operation in a direction in which the detection value of the first output detection unit matches a predetermined target value; And a control circuit that feedback-controls the DC voltage output to the second DC circuit during the operation in a direction in which the detection value of the second output detection unit coincides with a predetermined target value. Bidirectional power converter. The control circuit feedback-controls the DC voltage output to the second DC circuit during the fourth operation in a direction in which the DC voltage of the second DC circuit matches a first target value, 2. The bidirectional power converter according to claim 1, wherein feedback control is performed in a direction in which the DC voltage of the first DC circuit matches the second target value.

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