Charger, control method and control program product thereof

Abstract

A charger includes a rectifier, a DC / DC converter, and a power pulsation absorption circuit in which a first diode is connected between an inductor and the rectifier of the power pulsation absorption circuit, and a second diode is connected between the inductor and the rectifier. A capacitor and a first switch are connected in series between the first line and the second line, a third diode is connected between the inductor and the line connecting the capacitor and the first switch, and a second switch is connected between the second line and the line connecting the inductor and the third diode. And wherein the sum of the power output from the AC power supply and the power output from the capacitor is controlled to be constant, and the first switch remains on in a discharge period in which the instantaneous power is lower than the average power.

Description

Technical Field

[0001] The present disclosure relates to a charger, a control method and a control program product thereof. Background Art

[0002] As chargers for electric vehicles, various insulated single-phase AC / DC converters are being studied. Typically, chargers for electric vehicles use 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 insulated DC / DC converter. The large-capacity capacitor in the DC link needs to have sufficient capacity to absorb the power pulsation from the single-phase AC power supply, and miniaturization is difficult to achieve with this circuit configuration.

[0003] As a small charger capable of absorbing power ripple, Patent Document 1 and Non-Patent Document 1 describe a charger in which an active buffer for absorbing power ripple is added to a dual active bridge (DAB) converter and 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 switches of the DAB converter are disconnected. Therefore, the number of switching times is large, and the switching loss increases. In addition, during this zero current period, all switches are disconnected, so the current flowing through the inductor L of the DAB converter should be zero, but in fact there is a hysteresis in the moment when the switch is disconnected, and due to the hysteresis, the current remains, resulting in resonance between the inductor L of the DC / DC converter 120 and the parasitic capacitance of the switches S21 to S28. Therefore, the switching after the zero current period becomes hard switching, and switching loss occurs.

[0005] Patent Document 2 and Non-Patent Documents 2 to 4 disclose control without a zero current period (continuous current mode). In the continuous current mode, during one cycle of the AC voltage input from the AC power source, the switching frequency f of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power ripple absorption circuit 130 is set to 1. SW The change makes the zero current period become zero and eliminates the oscillation of the current and voltage of the inductor L, thereby avoiding hard switching after the zero current period, so that the charger can be controlled efficiently.

[0006] Prior Art

[0007] Patent Literature

[0008] [Patent Document 1] JP2022034820(A)

[0009] [Patent Document 2] JP2023025795(A)

[0010] Non-patent literature

[0011] Non-Patent Literature 1: Shohei Komeda, Yoshiya Ohnuma, "Dual Active Bridge AC-DC Converter with Active Energy Buffer", Semiconductor Power Converter Technology Conference Materials, 2021, SPC-21-003, pp. 13-18

[0012] Non-patent document 2: Shohei Komeda, Shunsuke Takuma, Yoshiya Ohnuma, "Frequency conversion control method for dual active bridge AC-DC converter with active energy buffer", 2021 IEE Japan Industrial Applications Society Conference Bulletin, 2021, Vol. 1, No. 30, pp. 13-18

[0013] Non-Patent Document 3: S. Komeda, S. Takuma, and Y. Ohnuma, "A Variable Switching Frequency Control Method for Dual Active Bridge Single-Phase AC-DC Converter with Active Energy Buffer", 2022 International Conference on Power Electronics (IPECHimeji 2022-ECCE Asia), 2022, pp. 1185-1190

[0014] Non-Patent Document 4: S. Komeda, S. Takuma, and Y. Ohnuma, "Variable Switching Frequency Control for Dual Active Bridge Single-Phase AC-DC Converter with Active Energy Buffer", IEEJ Industrial Applications, Vol. 12, No. 3, pp. 418-426 (2023) Summary of the invention

[0015] Problems to be solved by the present invention

[0016] In all the above controls, the operating waveform of the inductor L of the DC / DC converter 120 is asymmetric between positive and negative, and the asymmetric operating waveform is approximately a square waveform, so that it is easy to derive the control law. In order to make the operating waveform of the inductor L asymmetric between positive and negative, the above control requires that the discharge switch of the active buffer be switched more than twice within the switching cycle in either the discharge period in which the buffer capacitor of the active buffer is discharged or 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 the active buffer affects the efficiency of the charger.

[0017] Therefore, an object of the present invention is to provide a small and efficient charger capable of absorbing power pulsation.

[0018] Solutions to the problem

[0019] In order to solve the above purpose, a charger according to aspects of the present disclosure includes:

[0020] a rectifier including two input terminals connected to an AC power source, a cathode terminal, and an anode terminal;

[0021] a DC / DC converter, the DC / DC converter comprising a first terminal, a second terminal, a third terminal and a fourth terminal, the first terminal being connected to a cathode terminal of the rectifier via a first line, the second terminal being connected to an anode terminal of the rectifier via a second line, the third terminal being connected to a positive electrode of a battery, and the fourth terminal being connected to a negative electrode of the battery;

[0022] A power pulsation absorption circuit, the power pulsation absorption circuit comprising a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch; and

[0023] a control unit configured to control switching of a switch of the DC / DC converter, the first switch, and the second switch,

[0024] The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier.

[0025] The second diode is connected between the inductor and the other input terminal of the two input terminals of the rectifier,

[0026] In a state where the capacitor is arranged on the second line side, the capacitor and the first switch are connected in series between the first line and the second line,

[0027] The third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorption circuit.

[0028] The second switch is connected between a line connecting the inductor and the third diode of the power pulsation absorption circuit and the second line, and

[0029] wherein 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 source and the power output from the capacitor becomes constant, and

[0030] The control unit maintains the first switch in an on state in a discharge period, which is a period in which instantaneous power output from the AC power source is lower than an average power of power output from the AC power source.

[0031] The control method according to an aspect of the present disclosure is a control method executed by a computer to control a charger,

[0032] Wherein, the charger comprises:

[0033] a rectifier including two input terminals connected to an AC power source, a cathode terminal, and an anode terminal;

[0034] a DC / DC converter including 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 connected to a positive electrode of a battery, and a fourth terminal connected to a negative electrode of the battery; and

[0035] A power pulsation absorption circuit, the power pulsation absorption circuit comprising a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch; and

[0036] The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier.

[0037] The second diode is connected between the inductor and the other input terminal of the two input terminals of the rectifier,

[0038] In a state where the capacitor is arranged on the second line side, the capacitor and the first switch are connected in series between the first line and the second line,

[0039] The third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorption circuit.

[0040] The second switch is connected between a line connecting the inductor and the third diode of the power pulsation absorption circuit and the second line, and

[0041] Wherein, the control method comprises:

[0042] controlling the DC / DC converter, the first switch, and the second switch so that a sum of the power output from the AC power source and the power output from the capacitor becomes constant; and

[0043] The first switch is maintained in an on state in a discharge period which is a period in which instantaneous power output from the AC power source is lower than an average power of power output from the AC power source.

[0044] A control program product according to an aspect of the present disclosure causes a computer to execute the above control method.

[0045] Beneficial Effects of the Invention

[0046] According to aspects of the present disclosure, a small-sized and efficient charger capable of absorbing power pulsation can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a diagram of a charger 100 according to an embodiment of the present invention.

[0048] Figure 2 It is the instantaneous power p output from the AC power supply. s and from the buffer capacitor C buf Output instantaneous power p C A diagram showing the relationship between .

[0049] Figure 3 is a diagram showing the state of each switch in each mode.

[0050] Figure 4 is the operating waveform of the inductor L of the DC / DC converter 120 in the discontinuous current mode L and its equivalent square wave i L '(asymmetric waveform control method).

[0051] Figure 5 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 ripple absorption circuit 130 in the discontinuous current mode (asymmetrical waveform control method).

[0052] Figure 6 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the continuous current mode L and its equivalent square wave i L '(asymmetric waveform control method).

[0053] Figure 7 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 absorption circuit 130 in the continuous current mode (asymmetrical waveform control method).

[0054] Figure 8 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the discharge period. L Schematic diagram of (symmetrical waveform control method).

[0055] Fig. 9 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 absorption circuit 130 in the discharge period (symmetrical waveform control method).

[0056] Fig.10 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the charging period L Schematic diagram of (symmetrical waveform control method).

[0057] 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 absorption circuit 130 in the charging period (symmetrical waveform control method).

[0058] Fig.12 is a diagram showing an example of the efficiency of the charger 100 when operating using a symmetrical waveform control method and the efficiency of the charger 100 when operating using an asymmetrical waveform control method.

[0059] Reference Mark List

[0060] 100 Charger

[0061] 110 Rectifier

[0062] 120DC / DC Converter

[0063] S21 to S28 DC / DC converter switches

[0064] 130 Power pulsation absorption circuit

[0065] D31 First diode

[0066] D32 Second diode

[0067] D33 The third diode

[0068] Lb Inductor

[0069] C buf Snubber capacitor

[0070] S31 First switch

[0071] S32 Second switch

[0072] 200 AC power supply

[0073] 300 Batteries DETAILED DESCRIPTION

[0074] <Charger 100>

[0075] Figure 11 is a diagram of 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 absorption circuit 130, and a control unit 140. The charger 100 converts the single-phase AC voltage V input from the single-phase AC power source 200 into a single-phase AC voltage V S Converted to DC voltage V dc , and the DC voltage V dc Output to battery 300 .

[0076] The rectifier 110 has a cathode terminal 111 and an anode terminal 112 connected to the DC / DC converter 120, and has two input terminals 113 for connecting to the AC power source 200. The rectifier 110 is, for example, a bridge diode rectifier composed of four diodes, such as Figure 1 As shown, the rectifier 110 is configured to convert AC power input from two input terminals 113 connected to the AC power source into DC power and output it from the cathode terminal 111. The rectifier 110 can be connected to the AC power source 200 via a filter F having an inductor Lac and a capacitor Cac, as shown in FIG. Figure 1 shown.

[0077] The DC / DC converter 120 is, for example, a DAB (Dual Active Bridge) converter. The DC / DC converter 120 includes: 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 includes: a transformer Tr; a full-bridge circuit including four switches on the input side (primary side), namely, a first switch S21, a second switch S22, a third switch S23, and a fourth switch S24; and a full-bridge circuit including four switches on the output side (secondary side), namely, a fifth switch S25, a sixth switch S26, a seventh switch S27, and an eighth switch S28, and the transformer Tr is inserted between two full-bridge circuits. Each of the eight switches S21 to S28 is, for example, an N-channel power MOSFET (metal oxide semiconductor field effect transistor) having a reverse polarity diode (body diode). In this case, the N-channel power MOSFET may have a snubber capacitor.

[0078] The full-bridge circuit on the primary side of the DC / DC converter 120 includes two branches connected between the first terminal 121 and the second terminal 122 (a branch including a first switch S21 arranged on the first terminal 121a side and a second switch S22 arranged on the second terminal 122b side; and a branch 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 includes two branches connected between the third terminal 123 and the fourth terminal 124 (a branch 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 branch including a seventh switch S27 arranged on the third terminal 123 side and an eighth switch S28 arranged on the fourth terminal 124 side).

[0079] The DC / DC converter 120 includes an inductor L on the primary side of the transformer Tr. The inductor L is, for example, a leakage inductor of the transformer Tr.

[0080] In addition, the DC capacitor Cdc is connected between the third terminal 123 and the fourth terminal 124 of the DC / DC converter 120. The inductor Ldc may be connected between the third terminal 123 of the DC / DC converter 120 and the positive electrode of the battery 300.

[0081] 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 C buf , a first switch S31 and a second switch S32.

[0082] 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 resistor Lb of the power pulsation absorption circuit 130 and the other of the two input terminals 113 of the rectifier 110. In this case, each of the first diode D31 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 input terminal 113 of the rectifier 110 so that the direction from the output terminal 113 of the rectifier 110 to the inductor Lb is the forward direction. Thus, even when 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 absorption circuit 130.

[0083] The buffer capacitor C of the power pulsation absorption circuit 130 bufThe first switch S31 is connected in series between a first line LH and a second line LL, which will be described later. The first line LH is connected between the cathode terminal 111 of the rectifier 110 and the first terminal 121 of the DC / DC converter 120, and the second line LL is connected between the anode terminal 112 of the rectifier 110 and the second terminal 122 of the DC / DC converter 120. The buffer capacitor C buf The first switch S31 is arranged on the second line LL side, and the first switch S31 is arranged on the first line LH side. The first switch S31 is, for example, an N-channel power MOSFET (metal oxide semiconductor field effect transistor) having a reverse polarity diode (body diode). In this case, the source of the N-channel power MOSFET can be connected to the first line LH, and the drain of the N-channel power MOSFET can be connected to the buffer capacitor.

[0084] In this case, the third diode D33 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and a line described later, wherein the line is connected to the buffer capacitor C of the power pulsation absorption circuit 130. buf The line with the first switch S31 is connected so that the direction from the inductor Lb to the line is the forward direction.

[0085] The second switch S32 of the power pulsation absorption circuit 130 is connected between the second line LL and the line connecting the inductor Lb and the third diode D33 of the power pulsation absorption circuit 130. The second switch S32 is, for example, an N-channel power MOSFET (metal oxide semiconductor field effect transistor) having a reverse polarity diode (body diode). In this case, the drain of the N-channel power MOSFET can be 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 can be connected to the second line LL.

[0086] The control unit 140 controls switching of the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and S32 of the power pulsation absorption circuit 130. The control unit 140 is constituted by, for example, a computer.

[0087] 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 C buf and the second switch S32, so that it can be used as a power factor correction circuit (PFC). Therefore, in this embodiment, it is possible to control so that the sinusoidal voltage V described below is input from the AC power source 200 to the charger 100 S and the sinusoidal current i S .

[0088] [Mathematical formula 1]

[0089]

[0090] V S Indicates the effective value of the power supply voltage, I S Indicates the effective value of the power supply current.

[0091] In this case, as described below, the instantaneous power p output from the AC power source 200 is S is the average power P(=V S I S ) and the pulsating part prip(t)(=-V S I S cos2ω S t), and if Figure 2 As shown by the solid line in the figure, the instantaneous power p S Relative to the average power P( Figure 2 The dotted line in the figure) is the angular frequency of the alternating current ω S Pulsating at twice the angular frequency.

[0092] [Mathematical formula 2]

[0093] p s (t) = v s i s =V s I s (1-cos2ω s t)=P+p rip (t)

[0094] Thus, 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, so that the power pulsation absorption circuit 130 absorbs the pulsation of the power generated by the AC power supply 200, so that the power input to the DC / DC converter 120 is constant.

[0095] In this case, the charger 100 according to the present embodiment outputs the instantaneous power p from the AC power source 200. S Higher than the average power P(p S >P) and the instantaneous power p output from the AC power source 100 S When the average power is lower than P (p S <P) to change control.

[0096] When the instantaneous power p output from the AC power source 200 S Higher than the average power P(p S>P), 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 are controlled to reduce the instantaneous power p output from the AC power source 200 to S The pulsating part p rip The power ripple absorption circuit 130 transmits the power to the snubber capacitor C via the inductor Lb. buf supply, thus the buffer capacitor C buf The DC / DC converter 120 is charged so that only the average power P of the power output from the AC power source is supplied to the DC / DC converter 120. In other words, in this embodiment, the instantaneous power p output from the AC power source 200 is S The period above the average power P is the buffer capacitor C buf The charging period (charging period), and the buffer capacitor C buf Output instantaneous power p C like Figure 2 The long dashed line shows that it becomes negative.

[0097] On the contrary, when the instantaneous power p output from the AC power source 200 is S Lower than the average power P(p S <P), 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 are controlled to switch so that the buffer capacitor C buf Active discharge to compensate for the pulsating part p rip , the pulsating part p rip is the instantaneous power p output from the AC power source 200 S The difference between the instantaneous power P and the average power P is obtained, thereby supplying the average power P to the DC / DC converter 120. Specifically, in this embodiment, the instantaneous power P output from the AC power source 200 is S The period below the average power P is the buffer capacitor C buf The discharge period (discharge period), and the buffer capacitor C buf Output instantaneous power p C like Figure 2 The long dot-dash line shows that it becomes positive.

[0098] As described above, in this embodiment, the control unit 140 controls the switching of the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and 32 of the power pulsation absorption circuit 130 so that the instantaneous power p output from the AC power source 200 is S and from the buffer capacitor C buf Output instantaneous power p C The sum of becomes constant.

[0099] As described above, in this embodiment, during the discharge period, the buffer capacitor C buf Active discharge. Therefore, in this embodiment, it is possible to reduce the accumulation of buffer capacitor C buf The charge in the buffer capacitor C buf capacity), and can make the buffer capacitor C buf Miniaturization.

[0100] Furthermore, in the present embodiment, there is no pulsation in the electric power input to the DC / DC converter 120. Therefore, in the present embodiment, the transformer Tr and the DC capacitor Cdc of the DC / DC converter 120 can be miniaturized.

[0101] As described above, in this embodiment, passive components such as capacitors, inductors, and transformers can be miniaturized. Therefore, in this embodiment, a small charger capable of absorbing power pulsation can be provided.

[0102] <Asymmetric waveform control method>

[0103] The control unit 140 controls the switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 according to the seven modes or the six modes, so that, for example, the operating waveform i of the inductor L of the DC / DC converter 120 is L It becomes asymmetric between positive and negative (asymmetric waveform control method). Figure 3 1 is a diagram showing the state of each switch in seven modes. The seven modes include a mode (mode 5) in which the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130 are all in the OFF state.

[0104] Figure 4 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the discontinuous current mode L The discontinuous current mode includes the current i flowing through the inductor L. L The zero current period T 0 (Asymmetric waveform control method). This discontinuous current mode working waveform i L Able to switch 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 Figure 3 The seven modes shown are obtained, such as Figure 5 In this case, the current i in each of the seven modes is L As follows (Patent Document 1, Non-Patent Document 1).

[0105] [Mathematical formula 3]

[0106]

[0107] In this case, t cn (n=1 to 7) is the time when the mode is switched to mode n.

[0108] In this embodiment, in order to make the buffer capacitor C buf Active discharge, the control unit 140 controls the buffer capacitor C buf The voltage v C , so that the buffer capacitor C buf The voltage v C is always higher than the instantaneous voltage v output from the rectifier 110 rec Therefore, in this embodiment, the voltage applied to the buffer capacitor C buf The voltage v C has a different instantaneous voltage v than the rectifier 110 rec The value of the working waveform i L The slope of is different between Mode 2 and Mode 3. Similarly, the operating waveform i L The inclination of is different between Mode 6 and Mode 7. Therefore, in this embodiment, Figure 4 As shown, it is possible to generate positive and negative waveforms relative to i L =0 asymmetric working waveform.

[0109] Among them, in Figure 4 The working waveform shown is L In, t 0 to 10 is set to hold |t 0 -t 1 |=|t 5 -t 6 |、|t 1 -t 2 |=|t 7 -t 8 |、|t 2 -t 3 |=|t 6 -t 7 |、|t 3 -t 4 |=|t 8 -t 9 |, and t S1 is set at t 3 and t 4 Between and t S2 Set at t 8 and t 9 between, so as to maintain |t0 -t 1 |=|t S1 -t 4 |=|t S2 -t 9 |, working waveform i L Can be approximated by an equivalent square waveform i L '.

[0110] [Formula 4]

[0111]

[0112] Among them, in the equivalent square waveform i L 'In, t 0 ≤t<t 1 ,t S1 ≤t<t 4 ,t 5 ≤t<t 6 and t S2 ≤t<t 9 The period is defined as the inactive current period T q , t 1 ≤t<t 2 and t 7 ≤t<t 8 The period is defined as the buffer capacitor discharge current period T C , t 2 ≤t<t 3 and t 6 The period of ≤t<7 is defined as the power supply current period T rec , t 3 ≤t<t S1 and t 8 ≤t<t S2 The period is defined as the current balance period T b , and t 4 ≤t<5 and t 9 ≤t<t 10 is defined as the zero current period T 0 , switching period T SW The duty ratio for each time period is as follows.

[0113] [Formula 5]

[0114]

[0115] By giving i rec 、i C 、v C 、V dc and I L 'As the command value, the duty ratio of each period can be obtained. By using the duty ratio of each period thus obtained, it is possible to derive Figure 4 Medium working waveform L Among these command values, the one used for i rec and i C The command value i rec *、i C * The discharge period and the charge period are switched as follows, so that the power pulsation absorption circuit 130 functions as a PFC circuit, and functions as a circuit that absorbs pulsating power.

[0116] [Mathematical formula 6]

[0117]

[0118] Discontinuous current mode operating waveform L It is possible to achieve this without changing the switching frequency f of the DC / DC converter. SW By switching at a constant frequency f SW The switching frequency f is obtained by switching the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130. SW , it is possible to carry out the absence of zero current period T 0 Operation in the continuous current mode (Non-patent Documents 2 to 4). By solving D 0 =0, the switching frequency f in the continuous current mode can be found as follows SW .

[0119] [Formula 7]

[0120]

[0121] Figure 6 1 is an operation waveform i showing the inductor L of the DC / DC converter 120 in the continuous current mode. L and its equivalent square wave i L In continuous current mode, there is no operation in Mode 5, and therefore, as Figure 7 As shown, 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 and mode 1.

[0122] By optimizing the equivalent square wave i L 'The wave height I L ', the charger 100 can be operated at a higher efficiency (Non-Patent Documents 2 to 4). For example, when the equivalent square waveform i L 'The wave height I L ' command value, so that the AC power supply voltage V S The phase ωS Switching frequency f when t is 45 degrees SW (The above expression (3)) becomes a predetermined value (first frequency value) f 1 When the charger 100 is operated more efficiently, the equivalent square waveform i L 'The wave height I L 'Instruction value I L '*as follows.

[0123] [Mathematical formula 8]

[0124]

[0125] In this case, V Cmin Indicates the value applied to the buffer capacitor C buf The minimum value of the voltage.

[0126] <Symmetrical waveform control method>

[0127] In the asymmetric waveform control method, in order to make the working waveform i L Asymmetric between positive and negative, even during the discharge period, it is necessary to Figure 5 and Figure 7 The first switch S31 of the power pulsation absorbing circuit 130 is switched as shown. Thus, in the asymmetrical waveform control method, switching loss of the first switch S31 occurs even in the discharge period.

[0128] Therefore, the control unit 140 can control the switching of the 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 working waveform i of the inductor L of the DC / DC converter 120 is L It becomes symmetrical between positive and negative (symmetrical waveform control method).

[0129] For example, in the discharge period, the control unit 140 controls the switching of the switches S21 to S28 of the DC / DC converter 120 so that the operating waveform i of the inductor L of the DC / DC converter 120 is maintained while the on state of the first switch S31 of the power pulsation absorption circuit 130 is maintained. L Become symmetrical between positive and negative. Figure 8 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the discharge period. L The working waveform i L Can be pressed Fig. 9 The sequence of modes 1, 2, 4 and 7 shown is as follows Figure 3 The four modes (modes 1, 2, 4 and 7) of the seven modes shown are obtained. Specifically, Figure 8 The working waveform of the discharge period is shown in Fig.L The on / off control of the switches S21 to S24 on the primary side of the DC / DC converter 120 and the on / off control of the switches S25 to S28 on the secondary side can be offset by a phase shift angle To obtain, similar to the generally available control method of the DAB converter (e.g., Katsuya Hiraki, "Fundamentals and Applications of DC / DC Converters", 1st edition, The Institute of Electrical Engineers of Japan, January 2018, pp. 178-193).

[0130] Therefore, similar to a generally available control method of a DAB converter, the transmission power P of the DC / DC converter 120 during the discharge period can be controlled by a phase shift angle to control.

[0131] [Mathematical formula 9]

[0132]

[0133] By making the output current I dc (=P / V dc ) is constant, the phase shift angle in the discharge period can be calculated as follows The command value

[0134] [Formula 10]

[0135]

[0136] In the symmetrical waveform control method, in the discharge period, the first switch S31 of the power pulsation absorption circuit 130 is kept in the on state, and therefore, the current i flowing from the rectifier 110 to the DC / DC converter 120 is rec Therefore, in the symmetrical waveform control method, in the discharge period, in order to make the output current from the AC power source 200 a sine wave current, the control unit 140 controls the second switch of the power pulsation absorption circuit 130 so that the current i flowing from the AC power source 200 to the inductor Lb of the power pulsation absorption circuit 130 via the second diode D32 and the third diode D33 is bi The value of becomes as follows.

[0137] [Mathematical formula 11]

[0138]

[0139] In order to make the switching of the switches S21 to S28 of the DC / DC converter 120 soft switching during the discharge period, Figure 8 Working waveform L When switching from mode 1 to mode 2 (t = t1 ) when the current i L The value of needs to be equal to or greater than zero.

[0140] [Mathematical formula 12]

[0141]

[0142] Thus, during the discharge period, the switching frequency f of the DC / DC converter 120 is SW can be set to satisfy the following expression.

[0143] [Mathematical formula 13]

[0144]

[0145] In this manner, in the discharge period, switching of the switches S21 to S28 of the DC / DC converter 120 becomes soft switching, which improves the efficiency of the charger 100 .

[0146] In addition, in the symmetrical waveform control method, during the charging period, the control unit 140 may control the switching of the 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 operating waveform i of the inductor L of the DC / DC converter 120 is L Become symmetrical between positive and negative. Fig.10 is an operating waveform i showing the inductor L of the DC / DC converter 120 in the charging period L Working waveform i L You can press Fig.11 The sequence of modes 1, 3, 4 and 6 shown is as follows Figure 3 Four of the seven modes (modes 1, 3, 4 and 6) are obtained. Fig.11 In the switching shown, the on / off control of the switches S21 to S24 on the primary side of the DC / DC converter 120 and the on / off control of the switches S25 to S28 on the secondary side are offset by a phase shift angle , similar to the generally available control method of a DAB converter.

[0147] Contrary to the discharge period, in the charge period, when control is performed to keep the first switch S31 of the power pulsation absorption circuit 130 in the off state, in the period in which the switches S21, S24, S26 and S27 are in the on state and the switches S22, S23, S25 and S28 are in the off state, the operation waveform i L The inclination of i L <0 and i L >0 becomes different, that is, the working waveform i LIt is a waveform different from the operating waveform of the generally available control method of the DAB converter. When the switches S21, S24, S26 and S27 are in the on state, the switches S22, S23, S25 and S28 are in the off state, and the first switch S31 of the power pulsation absorption circuit 130 is in the off state, in i L When the current flows from the inductor L of the DC / DC converter 120 to the primary side of the DC / DC converter 120, and even if the first switch S31 of the power pulsation absorption circuit 130 is in the off state, the current flows into the buffer capacitor C of the power pulsation absorption circuit 130 through the switch S21 of the DC / DC converter 120 and the body diode of the first switch S31 of the power pulsation absorption circuit 130. buf , so that the buffer capacitor C buf The voltage v C is applied to the first terminal 121 and the second terminal 122 of the DC / DC converter 120. In contrast, in this case, L >0, the buffer capacitor C of the power pulsation absorption circuit 130 buf Separated from the circuit, the current output from the rectifier 110 flows from the primary side of the DC / DC converter 120 to the inductor L, not the buffer capacitor C. buf The voltage v C Instead, the voltage v output from the rectifier 110 rec Applied to the first terminal 121 and the second terminal 122 of the DC / DC converter 120, and the operating waveform i L The inclination of i L Working waveform i when <0 L Similarly, when the first switch S31 of the power pulsation absorption circuit 130 is kept in the off state during the period when the switches S21, S24, S26 and S27 are in the off state and the switches S22, S23, S25 and S28 are in the on state, the operating waveform i L The inclination of i L <0 and i L >0 becomes different.

[0148] Therefore, in Fig.11 Among the switches shown, the first switch S31 of the power pulsation absorbing circuit 130 is controlled to be in the on state during the period when the switches S21, S24, S26 and S27 are in the on state and the switches S22, S23, S25 and S28 are in the off state and during the period when the switches S21, S24, S26 and S27 are in the off state and the switches S22, S23, S25 and S28 are in the on state, and the first switch S31 of the power pulsation absorbing circuit 130 is controlled to be in the off state during the period other than the above. Therefore, as Fig.10 As shown, in the period when the switches S21, S24, S26 and S27 are in the on state and the switches S22, S23, S25 and S28 are in the off state, and in the period when the switches S21, S24, S26 and S27 are in the off state and the switches S22, S23, S25 and S28 are in the on state, the working waveform i L The inclination becomes constant.

[0149] Therefore, by conducting Fig.11 The switching and charging waveforms shown in the figure are L The shape of the DAB converter is similar to that of the operating waveform of the generally available control method. Therefore, the transmission power P of the DC / DC converter 120 during charging can also be controlled by the phase shift angle to control it, similar to the generally available control methods of a DAB converter.

[0150] [Formula 14]

[0151]

[0152] By making the output current I dc (=P / V dc ) is constant, the phase shift angle during the charging period can be calculated as follows The command value

[0153] [Mathematical formula 15]

[0154]

[0155] In the symmetrical waveform control method, during the charging period, the current i flowing from the rectifier 110 to the DC / DC converter 120 in a single switching cycle of the DC / DC converter 120 is rec The average values ​​are as follows.

[0156] [Formula 16]

[0157]

[0158] Thus, in the symmetrical waveform control method, in the charging period, in order to make the output current from the AC power source 200 a sine wave current, the control unit 140 controls the second switch of the power pulsation absorption circuit 130 so that the current i flowing from the AC power source 200 to the inductor Lb of the power pulsation absorption circuit 130 via the second diode D32 and the third diode D33 is bi Becomes as follows.

[0159] [Mathematical formula 17]

[0160]

[0161] Furthermore, during charging, in order to make the switching of the switches S21 to S28 of the DC / DC converter 120 soft switching, Fig.10 Working waveform L When switching from mode 1 to mode 3 (t = t 1 ) when the current i L The value must be equal to or greater than zero (i L (t 1 )≥0). Thus, during the charging period, the switching frequency f of the DC / DC converter 120 is SW can be set to satisfy the following expression.

[0162] [Mathematical formula 18]

[0163]

[0164] In this manner, in the charging period, switching of the switches S21 to S28 of the DC / DC converter 120 becomes soft switching, which improves the efficiency of the charger 100 .

[0165] As described above, in the symmetrical waveform control method, during the discharge period, the first switch S31 of the power pulsation absorption circuit 130 is kept in the on state. Thus, in the symmetrical waveform control method, the number of times the first switch S31 is controlled to be on / off is reduced, and the switching loss in the first switch S31 is reduced compared to the asymmetrical waveform control method, which improves the efficiency of the charger 100.

[0166] Fig.12 is a diagram showing an example of the efficiency of the charger 100 when operating using a symmetrical waveform control method and the efficiency of the charger 100 when operating using an asymmetrical waveform control method. Fig.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, the circles represent the efficiency when the charger 100 is operated in a symmetrical waveform control method, and the triangles represent the efficiency when the charger 100 is operated in an asymmetrical waveform control method. Fig.12 As shown, in the symmetrical waveform control method, the efficiency of the charger 100 is improved compared with the asymmetrical waveform control method.

[0167] Although the present invention has been described by referring to specific examples, various modifications and changes can be made to these examples without departing from the spirit and scope of the present invention as described in the claims.

Claims

1. A charger, comprising: a rectifier including a cathode terminal, an anode terminal, and two input terminals connected to an AC power source; a DC / DC converter, the DC / DC converter comprising a first terminal, a second terminal, a third terminal and a fourth terminal, the first terminal being connected to a cathode terminal of the rectifier via a first line, the second terminal being connected to an anode terminal of the rectifier via a second line, the third terminal being connected to a positive electrode of a battery, and the fourth terminal being connected to a negative electrode of the battery; A power pulsation absorption circuit, the power pulsation absorption circuit comprising a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch and a second switch; as well as a control unit configured to control switching of the first switch, the second switch, and a switch of the DC / DC converter, The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier. The second diode is connected between the inductor and the other input terminal of the two input terminals of the rectifier, In a state where the capacitor is arranged on the second line side, the capacitor and the first switch are connected in series between the first line and the second line, The third diode is connected between a line connecting the capacitor and the first switch and the inductor of the power pulsation absorption circuit. The second switch is connected between a line connecting the inductor and the third diode of the power pulsation absorption circuit and the second line, and wherein 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 source and the power output from the capacitor becomes constant, and The control unit maintains the first switch in an on state during a discharge period, which is a period during which instantaneous power output from the AC power source is lower than an average power of power output from the AC power source.

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, ie, a current flowing through an inductor on a primary side of a transformer of the DC / DC converter becomes symmetrical between positive and negative.

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

4. The charger according to claim 2, wherein: In the discharge period, the control unit controls the second switch of the power pulsation absorption circuit so that a current flowing from the AC power source to the inductor of the power pulsation absorption circuit becomes a sinusoidal wave current.

5. The charger according to any one of claims 1 to 4, wherein: The switch of the DC / DC converter The primary side includes: a branch including a first switch arranged on the first terminal side and a second switch arranged on the second terminal side, and a branch including a third switch arranged on the first terminal side and a fourth switch arranged on the second terminal side; and The secondary side includes: a branch including a fifth switch arranged on the third terminal side and a sixth switch arranged on the fourth terminal side, and a branch including a seventh switch arranged on the third terminal side and an eighth switch arranged on the fourth terminal side, In which, in the charging period, that is, the period when the instantaneous power output from the AC power supply is higher than the average power output from the AC power supply, the control unit turns on the first switch of the power pulsation absorption circuit in the first period, that is, the period when the first switch, the fourth switch, the sixth switch and the seventh switch of the DC / DC converter are turned on and the second switch, the third switch, the fifth switch and the eighth switch of the DC / DC converter are turned off, and in the second period, that is, the period when the second switch, the third switch, the fifth switch and the eighth switch of the DC / DC converter are turned on and the first switch, the fourth switch, the sixth switch and the seventh switch of the DC / DC converter are turned off, and the control unit turns off the first switch of the power pulsation absorption circuit in the period other than the first period and the second period.

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

7. The charger according to claim 5, wherein: In the charging period, the control unit controls the second switch of the power pulsation absorption circuit so that an output current flowing from the AC power source becomes a sinusoidal wave current.

8. The charger according to claim 1, wherein: The DC / DC converter is a DAB (Dual Active Bridge) converter.

9. A control method for controlling a charger by executing a computer, in, The charger comprises: a rectifier including a cathode terminal, an anode terminal, and two input terminals connected to an AC power source; a DC / DC converter including 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 connected to a positive electrode of a battery, and a fourth terminal connected to a negative electrode of the battery; and A power pulsation absorption circuit, the power pulsation absorption circuit comprising a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch and a second switch; and The first diode is connected between the inductor of the power pulsation absorption circuit and one of the two input terminals of the rectifier. The second diode is connected between the inductor and the other input terminal of the two input terminals of the rectifier, In a state where the capacitor is arranged on the second line side, the capacitor and the first switch are connected in series between the first line and the second line, The third diode is connected between a line connecting the capacitor and the first switch and the inductor of the power pulsation absorption circuit. The second switch is connected between a line connecting the inductor and the third diode of the power pulsation absorption circuit and the second line, and Wherein, the control method comprises: controlling the DC / DC converter, the first switch, and the second switch so that the sum of the power output from the AC power source and the power output from the capacitor becomes constant; and The first switch is maintained in an on state during a discharge period, which is a period during which instantaneous power output from the AC power source is lower than an average power of power output from the AC power source. 10 . A control program product which causes a computer to execute the control method according to claim 9 .

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