Charger, its control method, and control program

Abstract

To provide a small-sized and highly efficient charger capable of absorbing pulsation of power.SOLUTION: A DC / DC converter 120 and a first switch S31 and a second switch S32 of a power pulsation absorption circuit 130 are controlled so as to fix a sum of power ps outputted from an AC power source 200 and power pC outputted from a capacitor Cbuf of the power pulsation absorption circuit 130. During a discharge period which is a period in which instantaneous power ps outputted from the AC power source 200 is lower than average power P of power outputted from the AC power source 200, the first switch 31 of the power pulsation absorption circuit 130 is kept in a turned-on state.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This invention relates to a charger, a control method therefor, and a control program. [Background technology]

[0002] Various isolated single-phase AC / DC converters are being considered for use as chargers for electric vehicles. Generally, electric vehicle chargers use a circuit configuration consisting of a diode rectifier with a power factor correction (PFC) circuit, a large-capacity capacitor in the DC link section, and a high-frequency isolated DC / DC converter. The large-capacity capacitor in the DC link section needs to have enough capacity to absorb the power pulsation from the single-phase AC power supply, and miniaturization has been difficult with such a circuit configuration.

[0003] As a compact charger capable of absorbing power pulsations, Patent Document 1 and Non-Patent Document 1 disclose a charger in which an active buffer for absorbing power pulsations is added to a Dual-Active-Bridge (DAB) converter, and its control.

[0004] In the control methods disclosed in Patent Document 1 and Non-Patent Document 1 (discontinuous current mode), there is a period (zero current period) during which all switches of the DAB converter are turned off. As a result, the number of switching cycles is high, and switching losses are large. Furthermore, although all switches are turned off during this zero current period, and the current flowing through the inductor L of the DAB converter should be zero, in reality, there is a timing difference in when the switches turn off. This difference causes a residual current, resulting in resonance between the inductor L of the DC / DC converter 120 and the parasitic capacitances of switches S21 to S28. As a result, the switching after the zero current period becomes hard switching, and switching losses occur.

[0005] Therefore, Patent Document 2 and Non-Patent Documents 2-4 disclose a control method in which there is no zero-current period (continuous current mode). In continuous current mode, the switching frequency f of switches S21-S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 is set during one cycle of the AC voltage input from the AC power supply so that there is no zero-current period. SW By changing this, oscillations in the current and voltage of the inductor L are eliminated, hard switching after the zero-current period is avoided, and the charger can be controlled with high efficiency. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-34820 [Patent Document 2] Japanese Patent Publication No. 2023-25795 [Non-patent literature]

[0007] [Non-Patent Document 1] Shohei Yoneda, Yoshiya Onuma, "Study of a Dual Active Bridge AC-DC Converter with an Active Buffer," Semiconductor Power Conversion Research Group Proceedings, 2021, SPC-21-003, pp. 13-18. [Non-Patent Document 2] Shohei Yoneda, Shunsuke Takuma, and Yoshiya Onuma, "Study on Variable Frequency Control of a Dual Active Bridge AC-DC Converter with Active Buffer," Proceedings of the 2021 Institute of Electrical Engineers of Japan, Industrial Applications Division Conference, 2021, Vol. 1, No. 30, pp. 13-18. [Non-Patent Document 3] S. Komeda, S. Takuma and Y. Ohnuma, "A Variable Switching Frequency Control Method for a Dual-Active-Bridge Single-Phase AC-DC Converter with an Active Energy Buffer," 2022 International Power Electronics Conference (IPEC-Himeji 2022- ECCE Asia), 2022, pp. 1185-1190 [Non-Patent Document 4] S. Komeda, S. Takuma and Y. Ohnuma, “Variable Switching Frequency Control for a Dual-Active-Bridge Single-Phase AC-DC Converter with Active Energy Buffer,” IEEJ Journal of Ind. Appl., vol. 12, no. 3, pp. 418-426(2023) [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] All of the above control methods facilitate the derivation of the control law by making the operating waveform of the inductor L of the DC / DC converter 120 asymmetric in terms of positive and negative values, and approximating this asymmetrical operating waveform with a square waveform. In order to make the operating waveform of the inductor L asymmetric in terms of positive and negative values, the above control methods require that the active buffer's discharge switch be switched at least twice within the switching cycle, both during the discharge period when the active buffer's buffer capacitor discharges and during the charging period when the active buffer's buffer capacitor is charged. As a result, in the above control methods, the switching loss in this active buffer's discharge switch affects the efficiency of the charger.

[0009] Therefore, the present invention aims to provide a small, highly efficient charger capable of absorbing power pulsations. [Means for solving the problem]

[0010] To solve the above problems, a charger according to an embodiment of the present invention includes: a rectifier having two input terminals, a cathode terminal and an anode terminal for connecting to an AC power source; a DC / DC converter having a first terminal connected to the cathode terminal of the rectifier via a first line, a second terminal connected to the anode terminal of the rectifier via a second line, a third terminal for connecting to the positive terminal of a battery and a fourth terminal for connecting to the negative terminal of a battery; a power pulsation absorption circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch and a second switch; and a control unit that controls the switching of the switch of the DC / DC converter and the first and second switches, wherein the first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier, and the second diode is The control unit controls the DC / DC converter, the first switch and the second switch so that the sum of the power output from the AC power supply and the power output from the capacitor remains constant, and keeps the first switch ON during the discharge period, which is the period during which the instantaneous power output from the AC power supply is lower than the average power output from the AC power supply.

[0011] A control method according to one embodiment of the present invention is a control method for controlling a charger, which is performed by a computer, wherein the charger comprises: a rectifier having two input terminals, a cathode terminal and an anode terminal for connecting to an AC power source; a DC / DC converter having a first terminal connected to the cathode terminal of the rectifier via a first line, a second terminal connected to the anode terminal of the rectifier via a second line, a third terminal for connecting to the positive terminal of a battery and a fourth terminal for connecting to the negative terminal of a battery; and a power pulsation absorption circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch and a second switch, wherein the first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier, and the second diode is connected between the inductor and the The capacitor and the first switch are connected in series between the first line and the second line, the capacitor is located on the second line side, the third diode is connected between the line connecting the capacitor and the first switch and the inductor of the power pulsation absorption circuit, the second switch is connected between the line connecting the inductor of the power pulsation absorption circuit and the third diode and the second line, the control method controls the DC / DC converter, the first switch and the second switch so that the sum of the power output from the AC power supply and the power output from the capacitor is constant, and keeps the first switch ON during the discharge period, which is the period during which the instantaneous power output from the AC power supply is lower than the average power output from the AC power supply.

[0012] A control program according to one embodiment of the present invention causes a computer to execute the above control method. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a small, highly efficient charger capable of absorbing power pulsations. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows a charger 100 according to one embodiment of the present invention. [Figure 2] This diagram shows the relationship between the instantaneous power ps output from the AC power supply and the instantaneous power pC output from the buffer capacitor Cbuf. [Figure 3] This diagram shows the state of each switch in each mode. [Figure 4] This figure shows the operating waveform iL of the inductor L of the DC / DC converter 120 in discontinuous current mode and its equivalent square wave iL′ (asymmetric waveform control method). [Figure 5] This figure shows the switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 in discontinuous current mode (asymmetric waveform control method). [Figure 6] This figure shows the operating waveform iL of the inductor L of the DC / DC converter 120 in continuous current mode and its equivalent square wave iL′ (asymmetric waveform control method). [Figure 7] This figure shows the switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 in continuous current mode (asymmetric waveform control method). [Figure 8] This figure shows the operating waveform iL of the inductor L of the DC / DC converter 120 during the discharge period (symmetrical waveform control method). [Figure 9] This figure shows the switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 during the discharge period (symmetrical waveform control method). [Figure 10] This figure shows the operating waveform iL of the inductor L of the DC / DC converter 120 during the charging period (symmetrical waveform control method). [Figure 11] This figure shows the switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 during the charging period (symmetrical waveform control method). [Figure 12] This figure shows an example of the efficiency of the charger 100 when operated using a symmetrical waveform control method and when operated using an asymmetrical waveform control method. [Modes for carrying out the invention]

[0015] <Charger 100> Figure 1 shows a charger 100 according to one embodiment of the present invention. The charger 100 includes a rectifier 110, a DC / DC converter 120, a power pulsation absorption circuit 130, and a control unit 140. The charger 100 receives a single-phase AC voltage v from a single-phase AC power supply 200. S DC voltage V dc It converts the signal and outputs it to the 300mAh battery.

[0016] The rectifier 110 has a cathode terminal 111 and an anode terminal 112 connected to the DC / DC converter 120, and two input terminals 113 for connection to the AC power supply 200. The rectifier 110 is, for example, a bridge diode rectifier consisting of four diodes, as shown in Figure 1, and converts the AC current input from between the two input terminals 113 connected to the AC power supply into a DC current, which is output from the cathode terminal 111. The rectifier 110 may also be connected to the AC power supply 200 via a filter F having an inductor Lac and a capacitor Cac, as shown in Figure 1.

[0017] The DC / DC converter 120 is, for example, a DAB (Dual Active Bridge) converter. The DC / DC converter 120 has a first terminal 121 connected to the cathode terminal 111 of the rectifier 110, a second terminal 122 connected to the anode terminal 112 of the rectifier 110, a third terminal 123 for connecting to the positive terminal of the battery 300, and a fourth terminal 124 for connecting to the negative terminal of the battery 300. The DC / DC converter 120 has a transformer Tr and a full bridge circuit on the input side (primary side) with four switches, a first switch S21, a second switch S22, a third switch S23, and a fourth switch S24, and on the output side (secondary side) with four switches, a fifth switch S25, a sixth switch S26, a seventh switch S27, and an eighth switch S28. Each of the eight switches S21 to S28 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse polarity diode (body diode). In this case, the N-channel power MOSFET may also have a snubber capacitor.

[0018] The primary side full-bridge circuit of the DC / DC converter 120 has two legs connected between the first terminal 121 and the second terminal 122 (one leg including a first switch S21 located on the first terminal 121 side and a second switch 22 located on the second terminal 122 side, and the other leg including a third switch S23 located on the first terminal 121 side and a fourth switch S24 located on the second terminal 122 side), and the secondary side full-bridge circuit of the DC / DC converter 120 has two legs connected between the third terminal 123 and the fourth terminal 124 (one leg including a fifth switch S25 located on the third terminal 123 side and a sixth switch 26 located on the fourth terminal 124 side, and the other leg including a seventh switch S27 located on the third terminal 123 side and an eighth switch S28 located on the fourth terminal 124 side).

[0019] The DC / DC converter 120 has an inductor L on the primary side of the transformer Tr. This inductor L is, for example, the leakage inductor of the transformer Tr.

[0020] Furthermore, a DC capacitor Cdc is connected between the third terminal 123 and the fourth terminal 124 of the DC / DC converter 120. Alternatively, an inductor Ldc may be connected between the third terminal 123 of the DC / DC converter 120 and the positive terminal of the battery 300.

[0021] The power pulsation absorption circuit 130 includes a first diode D31, a second diode D32, a third diode D33, an inductor Lb, a buffer capacitor Cbuf, a first switch S31, and a second switch S32.

[0022] The first diode D31 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and one of the two input terminals 113 of the rectifier 110, and the second diode D32 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and the other of the two input terminals 113 of the rectifier 110. At this time, the first diode D31 and the second diode D32 of the power pulsation absorption circuit 130 are connected between the inductor Lb of the power pulsation absorption circuit 130 and the input terminal 113 of the rectifier 110 such that the direction from the input terminal 113 of the rectifier 110 to the inductor Lb is the forward direction. Therefore, even if an AC power supply 200 is connected to the input terminal 113 of the rectifier 110, a DC current is input to the inductor Lb of the power pulsation absorption circuit 130.

[0023] The buffer capacitor Cbuf and the first switch S31 of the power pulsation absorption circuit 130 are connected in series between the first line LH, which connects the cathode terminal 111 of the rectifier 110 to the first terminal 121 of the DC / DC converter 120, and the second line LL, which connects the anode terminal 112 of the rectifier 110 to the second terminal 122 of the DC / DC converter 120. The buffer capacitor Cbuf is located on the second line LL side, and the first switch 31 is located on the first line LH side. The first switch S31 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse polarity diode (body diode). In this case, it is preferable that the source of the N-channel power MOSFET is connected to the first line LH, and the drain of the N-channel power MOSFET is connected to the buffer capacitor.

[0024] The third diode D33 of the power pulsation absorption circuit 130 is connected between the line connecting the buffer capacitor Cbuf of the power pulsation absorption circuit 130 and the first switch S31, and the inductor Lb of the power pulsation absorption circuit 130, such that the direction from the inductor Lb to this line is the forward direction.

[0025] The second switch S32 of the power pulsation absorption circuit 130 is connected between the line connecting the inductor Lb of the power pulsation absorption circuit 130 and the third diode D33, and the second line LL. The second switch S32 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse polarity diode (body diode). In this case, it is preferable that the drain of the N-channel power MOSFET is connected to the line connecting the inductor Lb of the power pulsation absorption circuit 130 and the third diode D33, and the source of the N-channel power MOSFET is connected to the second line LL.

[0026] The control unit 140 controls the switching of switches S21 to S28 of the DC / DC converter 120 and switches S31 and S32 of the power pulsation absorption circuit 130. The control unit 140 is configured by, for example, a computer.

[0027] Since the power pulsation absorption circuit 130 includes a first diode D31, a second diode D32, a third diode D33, an inductor Lb, a buffer capacitor Cbuf, and a second switch S32, it can function as a power factor correction (PFC) circuit. Therefore, in this embodiment, a sine wave voltage v S , sine wave current i S can be controlled to be input from the AC power supply 200 to the charger 100.

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[0028] At this time, the instantaneous power p S output from the AC power supply 200 is the sum of the average power P (= V S I S ) and the pulsating part p rip (t) (=-V S I S cos 2ω S t), and pulsates at a double angular frequency of the AC angular frequency ω S with the average power P (the dashed line in FIG. 2) in between, as shown by the solid line in FIG. 2.

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[0029] Therefore, the control unit 140 controls the switching of switches S21 to S28 of the DC / DC converter 120 and switches S31 and S32 of the power pulsation absorption circuit 130 to absorb the power pulsation by the AC power supply 200 in the power pulsation absorption circuit 130 and make the power input to the DC / DC converter 120 constant.

[0030] At this time, in the charger 100 according to the present embodiment, the instantaneous power p output from the AC power supply 200 S is higher than the average power P (p s > P), and when the instantaneous power p output from the AC power supply 200 S is lower than the average power P (p s < P), the control is changed.

[0031] When the instantaneous power p output from the AC power supply s is higher than the average power P (p s > P), by controlling the switching of the eight switches S21 to S28 of the DC / DC converter 120 and the two switches S31 and S32 of the power pulsation absorption circuit 130, the pulsation part p S of the instantaneous power p rip is charged to the buffer capacitor Cbuf via the inductor Lb of the power pulsation absorption circuit 130, so that only the average power P of the power output from the AC power supply is input to the DC / DC converter 120. That is, in the present embodiment, during the period when the instantaneous power p output from the AC power supply S is higher than the average power P, it is the period (charging period) during which the buffer capacitor Cbuf is charged, and the instantaneous power p C output from the buffer capacitor Cbuf becomes negative as shown by the dashed line in FIG. 2.

[0032] On the other hand, when the instantaneous power p output from the AC power supply 200 s is lower than the average power P (p s < P), by controlling the switching of the eight switches S21 to S28 of the DC / DC converter 120 and the first switches S31 and S32 of the power pulsation absorption circuit 130, the buffer capacitor Cbuf is actively discharged via the first switch S31, and the pulsation part p S which is the difference between the instantaneous power p output from the AC power supply and the average power P ripBy compensating for this, the average power P is input to the DC / DC converter 120. In other words, in this embodiment, the instantaneous power p output from the AC power supply is compensated for. S The period during which the power is lower than the average power P is the period during which the buffer capacitor Cbuf discharges (discharge period), and the instantaneous power p output from the buffer capacitor Cbuf is lower during this period. C As shown by the dashed line in Figure 2, this value is positive.

[0033] As described above, in this embodiment, the control unit 140 controls the instantaneous power p output from the AC power supply 200. S and the instantaneous power p output from the buffer capacitor Cbuf C The switching of switches S21 to S28 of the DC / DC converter 120 and switches S31 and S32 of the power pulsation absorption circuit 130 is controlled so that the sum of these values ​​remains constant.

[0034] Thus, in this embodiment, the buffer capacitor Cbuf is actively discharged during the discharge period. Therefore, in this embodiment, it is possible to suppress the amount of power stored in the buffer capacitor Cbuf (i.e., the capacitance of the buffer capacitor Cbuf), and the buffer capacitor C buf It can be miniaturized.

[0035] Furthermore, in this embodiment, there is no pulsation in the power input to the DC / DC converter 120. Therefore, in this embodiment, it is possible to miniaturize the transformer Tr and DC capacitor Cdc of the DC / DC converter 120.

[0036] As described above, in this embodiment, it is possible to miniaturize passive elements such as capacitors, inductors, and transformers. Therefore, in this embodiment, it is possible to provide a compact charger that can absorb power pulsations.

[0037] <Asymmetrical waveform control method> The control unit 140, for example, controls the operating waveform i of the inductor L of the DC / DC converter 120. LThe switching of switches S21-S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 is controlled by seven or six modes so that the waveform is asymmetrical in terms of positive and negative (asymmetric waveform control method). Figure 3 shows the state of each switch in each of the seven modes. The seven modes include a mode (mode 5) in which all switches S21-S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 are turned off.

[0038] Figure 4 shows the current i flowing through the reactor L. L Operating waveform i of inductor L of DC / DC converter 120 in discontinuous current mode including zero current period T0 where i is zero L This figure shows the operating waveform i in this discontinuous current mode. L This is obtained by switching the seven modes shown in Figure 3 in the order of Mode 1, Mode 2, Mode 3, Mode 4, Mode 5, Mode 4, Mode 6, Mode 7, Mode 1, Mode 5, as shown in Figure 5. At this time, the current i in each of the seven modes L This is as follows (Patent Document 1, Non-Patent Document 1).

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[0039] In this embodiment, in order to more actively discharge the buffer capacitor Cbuf when the first switch S31 of the power pulsation absorption circuit 130 is ON, the control unit 140 controls the voltage v across the buffer capacitor Cbuf. C The instantaneous voltage v output from the rectifier 110 rec It is controlled to always be higher than [a certain value]. Therefore, in this embodiment, the voltage v across the buffer capacitor Cbuf is controlled to be higher than [a certain value]. C The instantaneous voltage v of the rectifier 110 rec The operating waveform i has different values ​​in Mode 2 and Mode 3. L The slopes are different. Similarly, the operating waveform i in mode 6 and mode 7L Their slopes are different. Therefore, in this embodiment, as shown in FIG. 4, an operating waveform in which the positive waveform and the negative waveform are asymmetric with respect to i = 0 can be generated. L

[0040] For the operating waveform shown in FIG. 4 L let t0 to t be set such that |t0 - t1| = |t5 - t6|, |t1 - t2| = |t7 - t8|, |t2 - t3| = |t6 - t7|, |t3 - t4| = |t8 - t9|, and 10 |t0 - t1| = |t S1 - t4| = |t S2 - t9|. Then, let t be set between t3 and t4 and S1 let t be set between t8 and t9. Then, the operating waveform i S2 can be approximated by an equivalent rectangular waveform i L '. [[ID=2r]] L

Equation

[0041] For the equivalent rectangular waveform i L ', define the period of t0 ≤ t < t1, t S1 ≤ t < t4, t5 ≤ t < t6, t S2 ≤ t < t9 as the non-current period T q , define the period of t1 ≤ t < t2, t7 ≤ t < t8 as the buffer capacitor discharge current period T C , define the period of t2 ≤ t < t3, t6 ≤ t < t7 as the power supply current period T rec , define the period of t3 ≤ t < t S1 , t8 ≤ t < t S2 as the current balance period T b , and define the period of t4 ≤ t < t5, t9 ≤ t < t 10 as the zero-current period T0. Then, the duty ratios of each period in the switching period T SW are as follows.

Equation

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[0042] Discontinuous current mode operation waveform i L The switching frequency f of the DC / DC converter 120 SW Without changing the switching frequency f SW This is obtained by switching switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130. On the other hand, the switching frequency f SW By changing this, it is possible to operate in a continuous current mode where the zero current period T0 is zero (Non-patent documents 2-4). Solving equation (2) above with D0=0 gives the switching frequency f in continuous current mode. SW It can be found as follows:

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[0043] Figure 6 shows the operating waveform i of the inductor L of the DC / DC converter 120 in continuous current mode. L and its equivalent square wave i LIt is a diagram showing '. In continuous current mode, since the operation in mode 5 disappears, as shown in FIG. 7, the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 are switched in the order of mode 1, mode 2, mode 3, mode 4, mode 6, mode 7, mode 1.

[0044] Equivalent square wave i L Peak value I of' L By optimizing the command value of ', it is possible to operate the charger 100 with higher efficiency (Non-Patent Documents 2 to 4). For example, the AC power supply voltage v S Phase ω of S Switching frequency f when t is 45 degrees SW (The above formula (3)) is such that the equivalent square wave form i becomes a predetermined value (first frequency value) f1 L Peak value I of' L By controlling the command value of ', it is possible to operate the charger 100 with higher efficiency. At this time, the equivalent square wave form i L Peak value I of' L Command value I of' L ' * Is as follows.

Equation

[0045] <Symmetrical waveform control method> In the asymmetrical waveform control method, in order to make the operation waveform i L Asymmetric between positive and negative, even during the discharge period, as shown in FIGS. 5 and 7, the first switch S31 of the power pulsation absorption circuit 130 had to be switched. Therefore, in the asymmetrical waveform control method, even during the discharge period, switching loss of the first switch S31 occurs.

[0046] Therefore, the control unit 140 is the operation waveform i of the inductor L of the DC / DC converter 120 LThe switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 may be controlled so that the waveform is symmetrical in terms of positive and negative (symmetric waveform control method).

[0047] For example, during the discharge period, the control unit 140 keeps the first switch S31 of the power pulsation absorption circuit 130 in the ON state while monitoring the operating waveform i of the inductor L of the DC / DC converter 120. L The switching of switches S21 to S28 of the DC / DC converter 120 is controlled so that the positive and negative sides are symmetrical. Figure 8 shows the operating waveform i of the inductor L of the DC / DC converter 120 during the discharge period. L This is a diagram showing the operation waveform i. L This is obtained by switching four of the seven modes shown in Figure 3 (modes 1, 2, 4, and 7) in the order of mode 1, mode 2, mode 4, and mode 7, as shown in Figure 9. In other words, the operating waveform i during the discharge period shown in Figure 8 L This is achieved by shifting the on / off control of the primary side switches S21~S24 and the secondary side switches 25~28 of the DC / DC converter 120 by a phase shift angle φ, similar to the general control method for DAB converters (for example, Katsuya Hirachi, "Fundamentals and Application of DC / DC Converter," 1st edition, Institute of Electrical Engineers of Japan, January 2018, pp. 178-193).

[0048] Therefore, the transmission power P of the DC / DC converter 120 during the discharge period can be controlled by the phase shift angle φ, similar to the general control method for DAB converters.

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[0049] In the symmetrical waveform control method, the first switch S31 of the power pulsation absorption circuit 130 remains ON during the discharge period, so the current i flowing from the rectifier 110 to the DC / DC converter 120 rec is zero. Therefore, in the symmetric waveform control method, in order to make the output current from the AC power supply 200 a sinusoidal current, the control unit 140 controls the current i that flows from the AC power supply 200 through the second diode D32 and the third diode D33 to the inductor Lb of the power pulsation absorption circuit 130 during the discharge period. bi The second switch of the power pulsation absorption circuit 130 is controlled so that the value of becomes as follows.

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[0050] Furthermore, in order to soft-switch the switching of switches S21-28 of the DC / DC converter 120 during the discharge period, the operating waveform i shown in Figure 8 is used. L In this case, the current i when switching from mode 1 to mode 2 (t=t1) L The value of must be zero or greater.

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[0051] Furthermore, in the symmetric waveform control method, during the charging period, the control unit 140 controls the operating waveform i of the inductor L of the DC / DC converter 120.L It is preferable to control the switching of switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 so that the positive and negative sides are symmetrical. Figure 10 shows the operating waveform i of the inductor L of the DC / DC converter 120 during the charging period. L This is a diagram showing the operation waveform i. L This is achieved by switching four of the seven modes shown in Figure 3 (modes 1, 3, 4, and 6) in the order of mode 1, mode 3, mode 4, and mode 6, as shown in Figure 11. In the switching shown in Figure 11, the on / off control of the primary side switches S21~S24 and the on / off control of the secondary side switches 25~28 of the DC / DC converter 120 are shifted by a phase shift angle φ, similar to the general control method for DAB converters.

[0052] In contrast to the discharge period, when the first switch S31 of the power pulsation absorption circuit 130 is kept off during the charging period, the operating waveform i is observed during the period when switches S21, S24, S26, and S27 are on and switches S22, S23, S25, and S28 are off. L is, i L <0 and i L The slope differs between >0 and 0, resulting in a waveform different from the operating waveform of the general control method for DAB converters. When switches S21, S24, S26, and S27 are ON, switches S22, S23, S25, and S28 are OFF, and the first switch S31 of the power pulsation absorption circuit 130 is OFF, i L While <0, current flows from the inductor L of the DC / DC converter 120 to the primary side of the DC / DC converter 120. This current flows through the switch S21 of the DC / DC converter 120, the body diode of the first switch S31 of the power pulsation absorption circuit 130, and into the buffer capacitor Cbuf of the power pulsation absorption circuit 130, even though the first switch S31 of the power pulsation absorption circuit 130 is off. The voltage v of the buffer capacitor Cbuf is then between the first terminal 121 and the second terminal 122 of the DC / DC converter 120. C This applies. On the other hand, at this time, i LWhile >0, the buffer capacitor Cbuf of the power pulsation absorption circuit 130 is disconnected from the circuit, and the current output from the rectifier 110 flows from the primary side of the DC / DC converter 120 to the inductor L, and the voltage v across the buffer capacitor Cbuf is between the first terminal 121 and the second terminal 122 of the DC / DC converter 120. C Unlike the voltage v output from the rectifier 110, rec The operating waveform i L The slope of i L Operating waveform i between <0 L The slope changes. Similarly, if the first switch S31 of the power pulsation absorption circuit 130 is kept off during the period when switches S21, S24, S26, and S27 are off and switches S22, S23, S25, and S28 are on, the operating waveform i L is, i L <0 and i L The slope will be different for values ​​greater than 0.

[0053] Therefore, in the switching shown in Figure 11, the first switch S31 of the power pulsation absorption circuit 130 is controlled to be ON during the periods when switches S21, S24, S26, and S27 are ON and switches S22, S23, S25, and S28 are OFF, and during the periods when switches S21, S24, S26, and S27 are OFF and switches S22, S23, S25, and S28 are ON. During all other periods, the first switch S31 of the power pulsation absorption circuit 130 is controlled to be OFF. In this way, the operating waveform i L As shown in Figure 10, the operating waveform i is as follows: during the period when switches S21, S24, S26, and S27 are ON and switches S22, S23, S25, and S28 are OFF, and during the period when switches S21, S24, S26, and S27 are OFF and switches S22, S23, S25, and S28 are ON. L The slope becomes constant.

[0054] Therefore, by performing the switching shown in Figure 11, the operating waveform i during the charging period is obtained. LThe waveform shape is similar to that of the operating waveform in a typical DAB converter control method. Therefore, the transmission power P of the DC / DC converter 120 during the charging period can also be controlled by the phase shift angle φ, similar to the typical control method for a DAB converter.

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[0055] In the symmetric waveform control method, the current i flowing from the rectifier 110 to the DC / DC converter 120 during the charging period rec The average switching time of the DC / DC converter 120 over one cycle is as follows:

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[0056] Furthermore, in order to soft-switch the switches S21-28 of the DC / DC converter 120 during the charging period, the operating waveform i in Figure 10 is used. L In this case, the current i when switching from mode 1 to mode 3 (t=t1) L The value of must be zero or greater (iL (t1)≧0). Therefore, during the charging period, the switching frequency f of the DC / DC converter 120 SW It is best to set it so that it satisfies the following equation.

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[0057] As described above, in the symmetric waveform control method, the first switch S31 of the power pulsation absorption circuit 130 is kept in the ON state during the discharge period. Therefore, in the symmetric waveform control method, the number of times the first switch S31 is turned on and off is reduced, and the switching loss in the first switch S31 is reduced compared to the asymmetric waveform control method, improving the efficiency of the charger 100.

[0058] Figure 12 shows an example of the efficiency of the charger 100 when operated using the symmetric waveform control method and when operated using the asymmetric waveform control method. In Figure 12, the vertical axis represents the efficiency of the charger 100, the horizontal axis represents the output power value of the DC / DC converter 120, circles represent the efficiency of the charger 100 when operated using the symmetric waveform control method, and triangles represent the efficiency of the charger 100 when operated using the asymmetric waveform control method. As shown in Figure 12, the efficiency of the charger 100 is improved with the symmetric waveform control method compared to the asymmetric waveform control method.

[0059] The present invention has been described above with reference to preferred embodiments. Although the present invention has been described with reference to specific examples, various modifications and changes can be made to these examples without departing from the spirit and scope of the invention as described in the claims. [Explanation of symbols]

[0060] 100 charger 110 Rectifier 120 DC / DC Converter S21~S28 DC / DC converter switch 130 Power pulsation absorption circuit D31 First diode D32 Second diode D33 Third diode Lb Inductor Cbuf buffer capacitor S31 First switch S32 Second switch 200 AC power supply 300 batteries

Claims

1. A rectifier having two input terminals, a cathode terminal, and an anode terminal for connecting to an AC power supply, A DC / DC converter having a first terminal connected to the cathode terminal of the rectifier via a first line, a second terminal connected to the anode terminal of the rectifier via a second line, a third terminal for connecting to the positive terminal of the battery, and a fourth terminal for connecting to the negative terminal of the battery, A power pulsation absorption circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch, The DC / DC converter has a switch and a control unit that controls the switching of the first switch and the second switch, The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier, and the second diode is connected between the inductor and the other of the two input terminals of the rectifier. The capacitor and the first switch are connected in series between the first line and the second line, and the capacitor is positioned on the second line side. The third diode is connected between the line connecting the capacitor and the first switch and the inductor of the power pulsation absorption circuit. The second switch is connected between the line connecting the inductor of the power pulsation absorption circuit and the third diode and the second line. The control unit, The DC / DC converter, the first switch, and the second switch are controlled so that the sum of the power output from the AC power supply and the power output from the capacitor remains constant. The first switch is kept in the ON state throughout a discharge period in which the instantaneous power output from the AC power source is lower than the average power output from the AC power source. During the discharge period, the switches of the DC / DC converter and the first switch are controlled so that the waveform of the inductor current, which is the current flowing through the primary side inductor of the transformer of the DC / DC converter, is symmetrical in terms of positive and negative values. The aforementioned DC / DC converter is a DAB (Dual Active Bridge) converter, which is a charger.

2. The DC / DC converter is The primary side includes a leg comprising a first switch located on the first terminal side and a second switch located on the second terminal side, and a leg comprising a third switch located on the first terminal side and a fourth switch located on the second terminal side. The secondary side includes a leg comprising a fifth switch located on the third terminal side and a sixth switch located on the fourth terminal side, and a leg comprising a seventh switch located on the third terminal side and an eighth switch located on the fourth terminal side. The control of the DC / DC converter's switching performed by the control unit during the discharge period is as follows: A first mode in which the first, fourth, sixth, and seventh switches of the DC / DC converter are on, the second, third, fifth, and eighth switches of the DC / DC converter are off, and the first switch of the power pulsation absorption circuit is on, The system includes a second mode in which the first, fourth, fifth, and eighth switches of the DC / DC converter are on, the second, third, sixth, and seventh switches of the DC / DC converter are off, and the first switch of the power pulsation absorption circuit is on, The charger according to claim 1, wherein the control unit controls the switching frequency of the DC / DC converter such that the value of the inductor current when switching from the first mode to the second mode during the discharge period is zero or greater.

3. The charger according to claim 1, wherein the control unit controls the second switch of the power pulsation absorption circuit so that the current flowing from the AC power supply to the inductor of the power pulsation absorption circuit becomes a sinusoidal current during the discharge period.

4. The charger according to any one of claims 1 to 3, wherein the control unit controls the switch of the DC / DC converter and the first switch so that, during a charging period in which the instantaneous power output from the AC power supply is higher than the average power output from the AC power supply, the waveform of the inductor current, which is the current flowing through the primary side inductor of the transformer of the DC / DC converter, is symmetrical in terms of positive and negative values.

5. The DC / DC converter is The primary side includes a leg comprising a first switch located on the first terminal side and a second switch located on the second terminal side, and a leg comprising a third switch located on the first terminal side and a fourth switch located on the second terminal side. The secondary side includes a leg comprising a fifth switch located on the third terminal side and a sixth switch located on the fourth terminal side, and a leg comprising a seventh switch located on the third terminal side and an eighth switch located on the fourth terminal side. The charger according to claim 4, wherein the control unit controls the first switch of the power pulsation absorption circuit to turn on during a first period in which the first, fourth, sixth, and seventh switches of the DC / DC converter are on and the second, third, fifth, and eighth switches of the DC / DC converter are off, and during a second period in which the second, third, fifth, and eighth switches of the DC / DC converter are on and the first, fourth, sixth, and seventh switches of the DC / DC converter are off, and controls the first switch of the power pulsation absorption circuit to turn off during periods other than the first and second periods.

6. The control of the DC / DC converter switching performed by the control unit during the charging period is as follows: A first mode in which the first, fourth, sixth, and seventh switches of the DC / DC converter are on, the second, third, fifth, and eighth switches of the DC / DC converter are off, and the first switch of the power pulsation absorption circuit is on, A third mode includes a mode in which the first, fourth, fifth, and eighth switches of the DC / DC converter are on, the second, third, sixth, and seventh switches of the DC / DC converter are off, and the first switch of the power pulsation absorption circuit is off. The charger according to claim 5, wherein the control unit controls the switching frequency of the DC / DC converter such that the value of the inductor current when switching from the first mode to the third mode during the charging period is zero or greater.

7. The charger according to claim 4, wherein the control unit controls the second switch of the power pulsation absorption circuit so that the output current from the AC power supply becomes a sinusoidal current during the charging period.

8. A control method for controlling a charger, which is performed by a computer, The aforementioned charger, A rectifier having two input terminals, a cathode terminal, and an anode terminal for connecting to an AC power supply, A DC / DC converter having a first terminal connected to the cathode terminal of the rectifier via a first line, a second terminal connected to the anode terminal of the rectifier via a second line, a third terminal for connecting to the positive terminal of the battery, and a fourth terminal for connecting to the negative terminal of the battery, A power pulsation absorption circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch, The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier, and the second diode is connected between the inductor and the other of the two input terminals of the rectifier. The capacitor and the first switch are connected in series between the first line and the second line, and the capacitor is positioned on the second line side. The third diode is connected between the line connecting the capacitor and the first switch and the inductor of the power pulsation absorption circuit. The second switch is connected between the line connecting the inductor of the power pulsation absorption circuit and the third diode and the second line. The control method described above is The DC / DC converter, the first switch, and the second switch are controlled so that the sum of the power output from the AC power supply and the power output from the capacitor remains constant. The first switch is kept in the ON state throughout a discharge period in which the instantaneous power output from the AC power source is lower than the average power output from the AC power source. During the discharge period, the switches of the DC / DC converter and the first switch are controlled so that the waveform of the inductor current, which is the current flowing through the primary side inductor of the transformer of the DC / DC converter, is symmetrical in terms of positive and negative values. The control method wherein the DC / DC converter is a DAB (Dual Active Bridge) converter.

9. A control program that causes a computer to execute the control method described in claim 8.

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