Charger, control method and control program therefor

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] The present invention relates to a charger, a control method thereof, and a control program thereof. [Background technology]

[0002] Various isolated single-phase AC / DC converters are being considered as chargers for electric vehicles. Generally, a circuit configuration consisting of a diode rectifier with a power factor correction (PFC) circuit, a large-capacity capacitor in the DC link, and a high-frequency isolated DC / DC converter is used for chargers for electric vehicles. The large-capacity capacitor in the DC link needs to have a capacity sufficient to absorb the power pulsation caused by the single-phase AC power supply, and this type of circuit configuration makes it difficult to miniaturize.

[0003] As an example of 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 the control thereof.

[0004] In the control (discontinuous current mode) disclosed in Patent Document 1 and Non-Patent Document 1, there is a period (zero current period) in which all the switches of the DAB converter are turned off. This results in a large number of switching times, resulting in large switching losses. In addition, in this zero current period, all the switches are turned off, so the current flowing through the inductor L of the DAB converter should be zero. However, in reality, there is a lag in the timing at which the switches are turned off, and this lag causes current to remain, resulting in resonance between the inductor L of the DC / DC converter 120 and the parasitic capacitances of the switches S21 to S28. This results in hard switching after the zero current period, resulting in switching losses.

[0005] Therefore, Patent Document 2 and Non-Patent Documents 2 to 4 disclose a control (continuous current mode) in which there is no zero current period. In the continuous current mode, the switching frequency f of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 is adjusted to 0.05 V during one period of the AC voltage input from the AC power source so that the zero current period becomes zero. SW By varying the input current and voltage, the oscillations 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] Patent Publication No. 2022-34820 [Patent Document 2] JP 2023-25795 A [Non-patent literature]

[0007] [Non-Patent Document 1] Shohei Yoneda, Yoshiya Onuma, "Study on Dual Active Bridge AC-DC Converter with Active Buffer", Semiconductor Power Conversion Study Group Materials, 2021, SPC-21-003, pp. 13-18 [Non-Patent Document 2] Shohei Yoneda, Shunsuke Takuma, and Yoshiya Onuma, "Study on Variable Frequency Control of Dual Active Bridge AC-DC Converter with Active Buffer," Proceedings of the 2021 Industrial Applications Division Conference of the Institute of Electrical Engineers of Japan, 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) Summary of the Invention [Problem to be solved by the invention]

[0008] In both of the above controls, the operating waveform of the inductor L of the DC / DC converter 120 is made asymmetric in terms of positive and negative, and this asymmetric operating waveform is approximated by a square waveform, making it easier to derive the control law. In order to make the operating waveform of the inductor L asymmetric in terms of positive and negative, in the above control, it is necessary to perform switching of the discharge switch of the active buffer at least twice within a switching period in both the discharging period in which the buffer capacitor of the active buffer is discharged and the charging period in which the buffer capacitor of the active buffer is charged. As a result, in the above control, the switching loss in the discharge switch of this active buffer affects the efficiency of the charger.

[0009] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a small, highly efficient charger capable of absorbing power pulsation. [Means for solving the problem]

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

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

[0012] A control program according to an embodiment of the present invention causes a computer to execute the above-described control method. Effect of the Invention

[0013] According to the present invention, it is possible to provide a small-sized and highly efficient charger capable of absorbing power pulsation. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 illustrates a charger 100 according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing the relationship between the instantaneous power ps output from an AC power supply and the instantaneous power pC output from a buffer capacitor Cbuf. [Diagram 3] FIG. 4 is a diagram showing the states of each switch in each mode. [Figure 4] FIG. 13 is a diagram showing an operating waveform iL of an inductor L of a DC / DC converter 120 in a discontinuous current mode and its equivalent square wave iL′ (asymmetric waveform control method). [Diagram 5] 11 is a diagram showing switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 in the discontinuous current mode (asymmetric waveform control method). [Figure 6] FIG. 13 is a diagram showing an operating waveform iL of an inductor L of a DC / DC converter 120 in a continuous current mode and its equivalent square wave iL′ (asymmetric waveform control method). [Figure 7] FIG. 11 is a diagram illustrating switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 in a continuous current mode (asymmetric waveform control method). [Figure 8] FIG. 11 is a diagram showing an operating waveform iL of an inductor L of a DC / DC converter 120 during a discharge period (symmetric waveform control method). [Figure 9] FIG. 11 is a diagram showing switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 during the discharge period (symmetric waveform control method). [Figure 10] FIG. 11 is a diagram showing an operating waveform iL of an inductor L of a DC / DC converter 120 during a charging period (symmetric waveform control method). [Figure 11] FIG. 11 is a diagram showing switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 during a charging period (symmetric waveform control method). [Figure 12] FIG. 11 is a diagram showing an example of the efficiency of the charger 100 when operated according to the symmetric waveform control method and the efficiency of the charger 100 when operated according to the asymmetric waveform control method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Charger 100> FIG 1 is a diagram showing a charger 100 according to an embodiment of the present invention. The charger 100 includes a rectifier 110, a DC / DC converter 120, a power pulsation absorbing circuit 130, and a control unit 140. The charger 100 converts a single-phase AC voltage v input from a single-phase AC power source 200 into a single-phase AC voltage v S DC voltage V dc and output it to the battery 300.

[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 an AC power supply 200. The rectifier 110 is, for example, a bridge diode rectifier consisting of four diodes as shown in Fig. 1, and converts an AC current input between two input terminals 113 connected to the AC power supply into a DC current and outputs it from the cathode terminal 111. The rectifier 110 may be connected to the AC power supply 200 via a filter F having an inductor Lac and a capacitor Cac as shown in Fig. 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 a cathode terminal 111 of the rectifier 110, a second terminal 122 connected to an anode terminal 112 of the rectifier 110, a third terminal 123 for connecting to a positive electrode of the battery 300, and a fourth terminal 124 for connecting to a negative electrode of the battery 300. The DC / DC converter 120 has a transformer Tr and a full bridge circuit including four switches, a first switch S21, a second switch S22, a third switch S23, and a fourth switch S24, on the input end side (primary side) with the transformer Tr in between, and a full bridge circuit including four switches, a fifth switch S25, a sixth switch S26, a seventh switch S27, and an eighth switch S28, on the output end side (secondary side). 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 have a snubber capacitor.

[0018] The full bridge circuit on the primary side of the DC / DC converter 120 has two legs connected between the first terminal 121 and the second terminal 122 (a leg including a first switch S21 arranged on the first terminal 121 side and a second switch S22 arranged on the second terminal 122 side, and a leg including a third switch S23 arranged on the first terminal 121 side and a fourth switch S24 arranged on the second terminal 122 side), and the full bridge circuit on the secondary side of the DC / DC converter 120 has two legs connected between the third terminal 123 and the fourth terminal 124 (a leg including a fifth switch S25 arranged on the third terminal 123 side and a sixth switch S26 arranged on the fourth terminal 124 side, and a leg including a seventh switch S27 arranged on the third terminal 123 side and an eighth switch S28 arranged on the fourth terminal 124 side).

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

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

[0021] The power pulsation absorbing 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 absorbing circuit 130 is connected between the inductor Lb of the power pulsation absorbing circuit 130 and one of the two input terminals 113 of the rectifier 110, and the second diode D32 of the power pulsation absorbing circuit 130 is connected between the inductor Lb of the power pulsation absorbing circuit 130 and the other of the two input terminals 113 of the rectifier 110. At this time, each of the first diode D31 and the second diode D32 of the power pulsation absorbing circuit 130 is connected between the inductor Lb of the power pulsation absorbing circuit 130 and the input terminal 113 of the rectifier 110 so that the direction from the input terminal 113 of the rectifier 110 to the inductor Lb is the forward direction. Therefore, even if the AC power source 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 absorbing circuit 130.

[0023] The buffer capacitor Cbuf and the first switch S31 of the power pulsation absorbing circuit 130 are connected in series between a first line LH connecting the cathode terminal 111 of the rectifier 110 and the first terminal 121 of the DC / DC converter 120, and a second line LL connecting the anode terminal 112 of the rectifier 110 and the second terminal 122 of the DC / DC converter 120. The buffer capacitor Cbuf is disposed on the second line LL side, and the first switch S31 is disposed 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 absorbing circuit 130 is connected between the line connecting the buffer capacitor Cbuf of the power pulsation absorbing circuit 130 and the first switch S31 and the inductor Lb of the power pulsation absorbing 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 absorbing circuit 130 is connected between the line connecting the inductor Lb and the third diode D33 of the power pulsation absorbing circuit 130 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 and the third diode D33 of the power pulsation absorbing circuit 130, 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 the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and S32 of the power pulsation absorbing circuit 130. The control unit 140 is constituted by, for example, a computer.

[0027] The power pulsation absorbing 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, and therefore can function as a power factor correction circuit (PFC). S , sinusoidal current i S However, it is possible to control the charger 100 so that the power is input from the AC power supply 200 to the charger 100.

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[0028] At this time, the instantaneous power p output from the AC power supply 200 S The average power P(=V S I S ) and the pulsating part p rip (t)(=-V S I S cos2ω S t), and as shown by the solid line in Figure 2, the average power P (dashed line in Figure 2) is sandwiched between the AC angular frequency ω S It pulsates at twice the angular frequency.

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

[0030] At this time, in the charger 100 according to this 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 accordingly.

[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 output from the AC power supply 200 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 this embodiment, when the instantaneous power p output from the AC power supply rip 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 S output from the buffer capacitor Cbuf becomes negative as shown by the dashed line in FIG. 2. C is 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 200 and the average power P ripBy compensating for the instantaneous power p output from the AC power supply, the average power P is input to the DC / DC converter 120. S The period during which the buffer capacitor Cbuf is discharged (discharge period), and the instantaneous power p C becomes positive, as shown by the dashed line in FIG.

[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 the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and S32 of the power pulsation absorbing circuit 130 is controlled so that the sum of these is constant.

[0034] In this manner, in the present embodiment, the buffer capacitor Cbuf is actively discharged during the discharge period. Therefore, in the present embodiment, it is possible to suppress the amount of power stored in the buffer capacitor Cbuf (i.e., the capacity of the buffer capacitor Cbuf), and the buffer capacitor Cbuf is buf It is possible to reduce the size of the device.

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

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

[0037] <Asymmetric waveform control method> The control unit 140 calculates, for example, the operating waveform i LThe switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 is controlled in seven modes or six modes so that the positive and negative waveforms are asymmetric (asymmetric waveform control method). Fig. 3 is a diagram showing the state of each switch in each of the seven modes. The seven modes include a mode (mode 5) in which all of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 are turned off.

[0038] Figure 4 shows the current i flowing through the reactor L. L The operating waveform of the inductor L of the DC / DC converter 120 in the discontinuous current mode including the zero current period T0 where the L This is a diagram showing the operation waveform of the discontinuous current mode i L The seven modes shown in FIG. 3 are obtained by switching in the order of mode 1, mode 2, mode 3, mode 4, mode 5, mode 4, mode 6, mode 7, mode 1, and mode 5 as shown in FIG. 5. At this time, the current i L 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 absorbing circuit 130 is on, the control unit 140 controls the voltage v applied to the buffer capacitor Cbuf to be C is the instantaneous voltage v output from the rectifier 110. rec Therefore, in this embodiment, the voltage v applied to the buffer capacitor Cbuf is controlled to be always higher than C is the instantaneous voltage v of the rectifier 110. rec and the operating waveforms in modes 2 and 3 are different. L Similarly, the slope of the operating waveforms in modes 6 and 7 is different.L The slopes are different. Therefore, in this embodiment, as shown in FIG. 4, an operation waveform in which the positive waveform and the negative waveform are asymmetric with respect to i L =0 can be generated.

[0040] The operation waveform shown in FIG. 4 L In, set t0 to t so that |t0 - t1| = |t5 - t6|, |t1 - t2| = |t7 - t8|, |t2 - t3| = |t6 - t7|, |t3 - t4| = |t8 - t9| 10 and set |t0 - t1| = |t S1 - t4| = |t S2 - t9|, and between t3 and t4, set t S1 and between t8 and t9, set t S2 . Then, the operation waveform i L can be approximated by the equivalent rectangular waveform i L '.

Equation

[0041] Define the period of t0 ≦ t < t1, t L ≦ t < t4, t5 ≦ t < t6, t S1 ≦ t < t9 of the equivalent rectangular waveform i S2 ' 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 ratio of each period in the switching period T SW is as follows.

Equation

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[0042] Discontinuous current mode operating waveform i L is the switching frequency f of the DC / DC converter 120 SW Without changing the switching frequency f SW The switching frequency f SW By changing the switching frequency f SW is found as follows:

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[0043] FIG. 6 shows the operating waveform i of the inductor L of the DC / DC converter 120 in the continuous current mode. L and its equivalent square wave i L7 is a diagram showing a continuous current mode in which the operation in mode 5 does not occur. In the continuous current mode, 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 absorbing circuit 130 are switched in the order of mode 1, mode 2, mode 3, mode 4, mode 6, mode 7, and mode 1.

[0044] equivalent square wave i L ′ wave height I L By optimizing the command value of v′, the charger 100 can be operated with higher efficiency (Non-Patent Documents 2 to 4). For example, S Phase ω S The switching frequency f when t is 45 degrees SW (the above formula (3)) is set to a predetermined value (first frequency value) f1. L ′ wave height I L By controlling the command value of i′, the charger 100 can be operated with higher efficiency. L ′ wave height I L ' command value I L ' * becomes:

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[0045] <Symmetrical waveform control method> In the asymmetric waveform control method, the operating waveform i L In order to make the positive and negative asymmetric, the first switch S31 of the power pulsation absorbing circuit 130 needs to be switched even during the discharge period, as shown in Figures 5 and 7. For this reason, in the asymmetric waveform control method, switching loss of the first switch S31 occurs even during the discharge period.

[0046] Therefore, the control unit 140 calculates the operating waveform i LThe switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorbing circuit 130 may be controlled so that the positive and negative voltages are symmetrical (symmetric waveform control method).

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

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

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[0049] In the symmetrical waveform control method, the first switch S31 of the power pulsation absorbing circuit 130 is kept on during the discharge period, so that the current i flowing from the rectifier 110 to the DC / DC converter 120 rec Therefore, in the symmetric waveform control method, in order to make the output current from the AC power supply 200 a sine wave current, the control unit 140 controls the current i bi The second switch of the power pulsation absorbing circuit 130 is controlled so that the value of

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[0050] In addition, in order to soft-switch the switches S21 to S28 of the DC / DC converter 120 during the discharge period, the operating waveform i L When switching from mode 1 to mode 2 (t=t1), the current i L The value must be greater than or equal to zero.

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

[0052] In contrast to the discharging period, when the first switch S31 of the power pulsation absorbing circuit 130 is controlled to be kept off, the operation waveform i L i L <0 and i L >0, the slope is different, and the waveform is different from the operation waveform of the general control method of the DAB converter. When the switches S21, S24, S26, and S27 are on, the switches S22, S23, S25, and S28 are off, and the first switch S31 of the power pulsation absorbing circuit 130 is off, i L <0, a current flows from the inductor L of the DC / DC converter 120 to the primary side of the DC / DC converter 120, and this current passes through the switch S21 of the DC / DC converter 120 and the body diode of the first switch S31 of the power pulsation absorbing circuit 130, and flows into the buffer capacitor Cbuf of the power pulsation absorbing circuit 130, even though the first switch S31 of the power pulsation absorbing circuit 130 is off. As a result, the voltage v of the buffer capacitor Cbuf is applied between the first terminal 121 and the second terminal 122 of the DC / DC converter 120. C On the other hand, at this time, i L0, the buffer capacitor Cbuf of the power pulsation absorbing 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. Between the first terminal 121 and the second terminal 122 of the DC / DC converter 120, the voltage v C Unlike the voltage v output from the rectifier 110, rec is applied, and the operating waveform i L The slope of i L <0 Operational waveform i L Similarly, when the first switch S31 of the power pulsation absorbing circuit 130 is kept off during the period when the switches S21, S24, S26, and S27 are off and the switches S22, S23, S25, and S28 are on, the operating waveform i L i L <0 and i L > 0 will have a different slope.

[0053] 11, the first switch S31 of the power pulsation absorbing circuit 130 is controlled to be on during a period when the switches S21, S24, S26, and S27 are on and the switches S22, S23, S25, and S28 are off, and during a period when the switches S21, S24, S26, and S27 are off and the switches S22, S23, S25, and S28 are on, and during the other periods, the first switch S31 of the power pulsation absorbing circuit 130 is controlled to be off. L In a period in which the switches S21, S24, S26, and S27 are on and the switches S22, S23, S25, and S28 are off, and in a period in which the switches S21, S24, S26, and S27 are off and the switches S22, S23, S25, and S28 are on, as shown in FIG. 10, the operation waveform i L The slope of becomes constant.

[0054] Therefore, by performing the switching shown in Fig. 11, the operating waveform during the charging period i LThe waveforms of the waveforms in the general control method of the DAB converter are similar to those of the waveforms in the general control method of the DAB converter. Therefore, the transmission power P of the DC / DC converter 120 during the charging period can be controlled by the phase shift angle φ, similar to the general control method of the DAB converter.

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[0055] In the symmetric waveform control method, during the charging period, the current i rec The average of the above in one switching period of the DC / DC converter 120 is given by:

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[0056] In addition, in order to soft-switch the switches S21 to S28 of the DC / DC converter 120 during the charging period, the operating waveform i L When switching from mode 1 to mode 3 (t=t1), the current i L The value of must be greater than or equal to zero (iL (t1)≧0). Therefore, during the charging period, the switching frequency f SW should be set so as to satisfy the following formula:

number

[0057] As described above, in the symmetric waveform control method, the first switch S31 of the power pulsation absorbing 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 controlled to be 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] Fig. 12 is a diagram showing an example of the efficiency of the charger 100 when operated by the symmetric waveform control method and the efficiency of the charger 100 when operated by the asymmetric waveform control method. In Fig. 12, the vertical axis indicates the efficiency of the charger 100, the horizontal axis indicates the output power value of the DC / DC converter 120, the circles indicate the efficiency of the charger 100 when operated by the symmetric waveform control method, and the triangles indicate the efficiency of the charger 100 when operated by the asymmetric waveform control method. As shown in Fig. 12, the efficiency of the charger 100 is improved in the symmetric waveform control method compared to the asymmetric waveform control method.

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

[0060] 100 charger 110 Rectifier 120 DC / DC Converter S21~S28 DC / DC converter switches 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 Battery

Claims

1. a rectifier having two input terminals for connection to an AC power source, a cathode terminal and an anode terminal; a DC / DC converter having a first terminal connected to a cathode terminal of the rectifier via a first line, a second terminal connected to an anode terminal of the rectifier via a second line, a third terminal for connecting to a positive terminal of a battery, and a fourth terminal for connecting to a negative terminal of the battery; a power pulsation absorbing circuit including a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch; a control unit that controls switching of the switch of the DC / DC converter, the first switch, and the second switch; the first diode is connected between an inductor of the power pulsation absorbing 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 disposed on the second line side; the third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorbing circuit; the second switch is connected between a line connecting an inductor of the power pulsation absorbing circuit and the third diode and the second line; The control unit is controlling the DC / DC converter, the first switch, and the second switch so that a sum of a power output from the AC power supply and a power output from the capacitor becomes constant; The charger maintains the first switch in an on state during a discharging period during which instantaneous power output from the AC power supply is lower than an average power of power output from the AC power supply.

2. 2. The charger according to claim 1, wherein the control unit controls a switch of the DC / DC converter and the first switch so that a waveform of an inductor current, which is a current flowing through an inductor on a primary side of a transformer of the DC / DC converter, is symmetrical between positive and negative.

3. The DC / DC converter comprises: a leg including a first switch arranged on the first terminal side and a second switch arranged on the second terminal side, and a leg including a third switch arranged on the first terminal side and a fourth switch arranged on the second terminal side, a leg including a fifth switch arranged on the third terminal side and a sixth switch arranged on the fourth terminal side, and a leg including a seventh switch arranged on the third terminal side and an eighth switch arranged on the fourth terminal side, The control of switching of the DC / DC converter executed by the control unit during the discharge period includes: a first mode in which a first switch, a fourth switch, a sixth switch, and a seventh switch of the DC / DC converter are on, a second switch, a third switch, a fifth switch, and an eighth switch of the DC / DC converter are off, and a first switch of the power pulsation absorbing circuit is on; a second mode in which a first switch, a fourth switch, a fifth switch, and an eighth switch of the DC / DC converter are on, a second switch, a third switch, a sixth switch, and a seventh switch of the DC / DC converter are off, and a first switch of the power pulsation absorbing circuit is on; 3. The charger according to claim 2, wherein the control unit controls a switching frequency of the DC / DC converter so that a value of the inductor current when switching from the first mode to the second mode is equal to or greater than zero.

4. 3. The charger according to claim 2, wherein the control unit controls a second switch of the power pulsation absorbing circuit so that a current flowing from the AC power supply to an inductor of the power pulsation absorbing circuit becomes a sine wave current during the discharging period.

5. The DC / DC converter comprises: a leg including a first switch arranged on the first terminal side and a second switch arranged on the second terminal side, and a leg including a third switch arranged on the first terminal side and a fourth switch arranged on the second terminal side, a leg including a fifth switch arranged on the third terminal side and a sixth switch arranged on the fourth terminal side, and a leg including a seventh switch arranged on the third terminal side and an eighth switch arranged on the fourth terminal side, 5. The charger according to claim 1, wherein, during a charging period in which instantaneous power output from the AC power supply is higher than an average power of power output from the AC power supply, the control unit controls the first switch of the power pulsation absorbing circuit to be on in a first period in which the first switch, the fourth switch, the sixth switch, and the seventh switch of the DC / DC converter are on and the second switch, the third switch, the fifth switch, and the eighth switch of the DC / DC converter are off and in a second period in which the second switch, the third switch, the fifth switch, and the eighth switch of the DC / DC converter are on and the first switch, the fourth switch, the sixth switch, and the seventh switch of the DC / DC converter are off, and controls the first switch of the power pulsation absorbing circuit to be off in periods other than the first period and the second period.

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

7. 6. The charger according to claim 5, wherein the control unit controls the second switch of the power pulsation absorbing circuit so that the output current from the AC power supply becomes a sine wave current during the charging period.

8. 2. The charger according to claim 1, wherein the DC / DC converter is a dual active bridge (DAB) converter.

9. 1. A computer-implemented control method for controlling a charger, comprising: The charger includes: a rectifier having two input terminals for connection to an AC power source, a cathode terminal and an anode terminal; a DC / DC converter having a first terminal connected to a cathode terminal of the rectifier via a first line, a second terminal connected to an anode terminal of the rectifier via a second line, a third terminal for connecting to a positive terminal of a battery, and a fourth terminal for connecting to a negative terminal of the battery; a power pulsation absorbing circuit including 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 an inductor of the power pulsation absorbing 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 disposed on the second line side; the third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorbing circuit; the second switch is connected between a line connecting an inductor of the power pulsation absorbing circuit and the third diode and the second line; The control method includes: controlling the DC / DC converter, the first switch, and the second switch so that a sum of a power output from the AC power supply and a power output from the capacitor becomes constant; The control method comprises: maintaining the first switch in an on state during a discharge period during which an instantaneous power output from the AC power supply is lower than an average power of the power output from the AC power supply.

10. A control program that causes a computer to execute the control method according to claim 9.

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