Interleaving parallel isolation type bidirectional DC-DC converter

Abstract

The invention discloses an interleaving parallel isolation type bidirectional DC-DC (Direct Current-Direct Current) converter. Comprising a first direct-current power supply, a second direct-current power supply, a first inductor, a second inductor, a third inductor, a fourth inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor and a transformer. The circuit has the advantages of full-range current zero ripple, wide power range and high efficiency. The technical problems that an existing bidirectional DC-DC converter for the energy storage type dynamic voltage restorer is difficult to adapt to voltage matching, large in current ripple and prone to being affected by high voltage stress generated by direct current bus voltage are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage type dynamic voltage restorers, and in particular to an interleaved parallel isolated bidirectional DC-DC converter. Background Art

[0002] Energy storage type dynamic voltage restorer is a widely used power quality control device used to improve transient voltage problems such as voltage sag and voltage swell in power systems. In energy conversion and distributed power systems, dynamic voltage restorer converts DC power of energy storage equipment into AC power, thereby compensating for voltage fluctuations caused by faults or interference, ensuring voltage stability of critical loads. The structure of energy storage type dynamic voltage restorer is as follows: Figure 1 As shown, Figure 1 In this architecture, both the front-stage DC-DC link and the back-stage DC-AC link enable bidirectional energy flow. When the energy storage device is low on power and grid conditions permit, the device draws power from the grid to charge the energy storage device, ensuring sufficient energy to compensate for voltage sags. During voltage sags or other power quality issues, the device draws power from the energy storage device, converts DC power into AC power, and injects it into the grid for voltage compensation. This requirement for bidirectional energy flow has led to the introduction of efficient bidirectional DC-DC converters in energy storage-based dynamic voltage restorers. Typically, the voltage level in energy storage devices is around 50V, while the back-stage DC-AC inverter requires a DC voltage of at least 400V. This places high demands on the step-up and step-down voltage of the front-stage DC-DC converter. The traditional dual active bridge converter is one of the most widely used converters, but when the voltages at both ends are mismatched, the converter experiences significant commutation current, resulting in low transmission efficiency. Furthermore, the high voltage stress generated by the DC bus voltage limits its efficiency and reliability. At the same time, since energy storage systems use supercapacitors or batteries, large current ripple can reduce the energy conversion efficiency of the entire system, increase thermal stress and loss, induce mechanical stress and vibration, accelerate the aging of components and battery materials, and shorten their service life. Therefore, research on bidirectional DC-DC converters with dynamic voltage matching, full-range zero current ripple, and a wide power range to improve the performance of energy storage dynamic voltage restorers is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0003] The present invention provides an interleaved parallel isolated bidirectional DC-DC converter, which is used to solve the technical problems of existing bidirectional DC-DC converters used in energy storage dynamic voltage restorers, such as difficulty in adapting to voltage matching, large current ripple, and susceptibility to high voltage stress generated by DC bus voltage.

[0004] In view of this, the present invention provides an interleaved parallel isolated bidirectional DC-DC converter, comprising a first DC power supply, a second DC power supply, a first inductor, a second inductor, a third inductor, a fourth inductor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, and a transformer;

[0005] The positive electrode of the first DC power supply is respectively connected to one end of the first inductor and one end of the second inductor, and the negative electrode of the first DC power supply is respectively connected to the source electrode of the first switching tube, the source electrode of the second switching tube, the negative electrode of the first capacitor, the negative electrode of the second capacitor, the negative electrode of the third capacitor, and the negative electrode of the fourth capacitor;

[0006] The positive electrode of the second DC power supply is respectively connected to the drain of the fifth switching tube and the positive electrode of the fifth capacitor, the negative electrode of the second DC power supply is respectively connected to the source of the sixth switching tube and the negative electrode of the sixth capacitor, the other end of the first inductor is respectively connected to one end of the third inductor and the positive electrode of the first capacitor, the drain of the first switching tube is respectively connected to the other end of the third inductor, the source of the third switching tube and the same-name terminal of the primary side of the transformer, the positive electrode of the third capacitor is connected to the drain of the third switching tube, the other end of the second inductor is respectively connected to one end of the fourth inductor and the positive electrode of the second capacitor, the drain of the second switching tube is respectively connected to the other end of the fourth inductor, the source of the fourth switching tube and the non-same-name terminal of the primary side of the transformer, the positive electrode of the fourth capacitor is connected to the drain of the fourth switching tube, the same-name terminal of the secondary side of the transformer is respectively connected to the source of the fifth switching tube and the drain of the sixth switching tube, and the non-same-name terminal of the secondary side of the transformer is respectively connected to the negative electrode of the fifth capacitor and the positive electrode of the sixth capacitor.

[0007] Optionally, the first switch tube and the second switch tube are turned on 180° apart, the first switch tube and the third switch tube are turned on complementarily, the second switch tube and the fourth switch tube are turned on complementarily, and the fifth switch tube and the sixth switch tube are turned on complementarily.

[0008] Optionally, a duty cycle of the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube is 0.5.

[0009] Optionally, the duty cycle of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube is 0.8, and the duty cycle of the fifth switch tube and the sixth switch tube is 0.5.

[0010] Optionally, a ratio of the phase shift angle between the first DC power supply side and the second DC power supply side relative to the entire switching period is [0, 1].

[0011] Optionally, the turns ratio of the transformer is 1:2.

[0012] Optionally, the output voltage of the first DC power supply is 50V.

[0013] Optionally, the output voltage of the second DC power supply is 400V.

[0014] Optionally, the inductance values of the first inductor, the second inductor, the third inductor, and the fourth inductor are all 100 µH.

[0015] Optionally, the capacitance values of the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, and the sixth capacitor are all 110 µF.

[0016] From the above technical solutions, it can be seen that the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention has the following advantages:

[0017] The interleaved parallel isolated bidirectional DC-DC converter provided by the present invention can, on the one hand, achieve dynamic voltage matching by adjusting the transformer's step-up ratio in real time when the DC side voltage fluctuates, thereby ensuring low loss and high efficiency of the converter under various operating conditions. On the other hand, it can achieve zero current ripple under any conduction duty cycle, any DC voltage, and any transformer turns ratio. Furthermore, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention has a wide power operating range. Therefore, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention solves the technical problems of existing bidirectional DC-DC converters used in energy storage dynamic voltage restorers, such as difficulty in adapting to voltage matching, large current ripple, and susceptibility to high voltage stress generated by the DC bus voltage.

[0018] At the same time, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention avoids the use of large electrolytic capacitors in the access side of the energy storage system and the DC-DC circuit, which can extend the service life of the energy storage battery and the interleaved parallel isolated bidirectional DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A circuit structure diagram of an energy storage type dynamic voltage restorer;

[0021] Figure 2 A circuit diagram of an interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention;

[0022] Figure 3This is a waveform diagram of the main components of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0≤d≤0.5;

[0023] Figure 4a This is one of the working modal diagrams of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0≤d≤0.5;

[0024] Figure 4b This is the second working modal diagram of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0≤d≤0.5;

[0025] Figure 4c This is the third working modal diagram of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0≤d≤0.5;

[0026] Figure 5 This is a waveform diagram of the main components of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0.5≤d≤1;

[0027] Figure 6 This is a working modal diagram of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift control when 0.5≤d≤1;

[0028] Figure 7 A diagram showing the power regulation range of an interleaved parallel isolated bidirectional DC-DC converter under single phase-shift control provided in an embodiment of the present invention;

[0029] Figure 8a This is a transformer waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention to achieve voltage matching under single phase shift control;

[0030] Figure 8b This is a transformer waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention when voltage matching is not achieved under single phase-shift control;

[0031] Figure 9 Graphs showing power and efficiency of an interleaved parallel isolated bidirectional DC-DC converter under single-shift control at different voltage differences provided in an embodiment of the present invention;

[0032] Figure 10 A ripple comparison diagram of an interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention and other structural forms;

[0033] Figure 11This is a waveform diagram of the main components of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single-phase shift plus interleaved parallel control when 0≤d≤D-0.5;

[0034] Figure 12a This is one of the working modal diagrams of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single-phase shift plus interleaved parallel control when 0≤d≤D-0.5;

[0035] Figure 12b This is the second working modal diagram of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single-phase shift plus interleaved parallel control when 0≤d≤D-0.5;

[0036] Figure 12c This is the third working modal diagram of the first half cycle of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single-phase shift plus interleaved parallel control when 0≤d≤D-0.5;

[0037] Figure 13 A diagram showing the power regulation range of an interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention under single phase shift plus interleaved parallel control;

[0038] Figure 14a This is a transformer waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention achieving voltage matching under single-phase shift plus interleaved parallel control;

[0039] Figure 14b This is a transformer waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention when voltage matching is not achieved under single-phase shift plus interleaved parallel control;

[0040] Figure 15 The power and efficiency diagrams of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention at different boost ratios under single-phase-shift plus interleaved parallel control;

[0041] Figure 16 This is one of the experimental waveform diagrams of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase-shift control working mode;

[0042] Figure 17 This is the second experimental waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase-shift control mode;

[0043] Figure 18 This is the third experimental waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase-shift control mode;

[0044] Figure 19 This is one of the experimental waveform diagrams of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase shift plus interleaved parallel control mode;

[0045] Figure 20 This is the second experimental waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase shift plus interleaved parallel control mode;

[0046] Figure 21 This is the third experimental waveform diagram of the interleaved parallel isolated bidirectional DC-DC converter provided in an embodiment of the present invention in a single phase shift plus interleaved parallel control mode;

[0047] Figure 22 The figure shows the overall efficiency curves of the interleaved parallel isolated bidirectional DC-DC converter provided in the embodiment of the present invention before and after constant voltage matching is adopted. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0049] For easier understanding, see Figure 2 The present invention provides an embodiment of an interleaved parallel isolated bidirectional DC-DC converter, including a first DC power supply V1, a second DC power supply V2, a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a fifth switch tube Q1, a sixth switch tube Q2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, and a transformer T.

[0050] The positive electrode of the first DC power supply V1 is respectively connected to one end of the first inductor L1 and one end of the second inductor L2, and the negative electrode of the first DC power supply V1 is respectively connected to the source of the first switching tube S1, the source of the second switching tube S2, the negative electrode of the first capacitor C1, the negative electrode of the second capacitor C2, the negative electrode of the third capacitor C3, and the negative electrode of the fourth capacitor C4.

[0051] The positive electrode of the second DC power supply V2 is connected to the drain of the fifth switch tube Q1 and the positive electrode of the fifth capacitor C5 respectively. The negative electrode of the second DC power supply V2 is connected to the source of the sixth switch tube Q2 and the negative electrode of the sixth capacitor C6 respectively. The other end of the first inductor L1 is connected to one end of the third inductor L3 and the positive electrode of the first capacitor C1 respectively. The drain of the first switch tube S1 is connected to the other end of the third inductor L3, the source of the third switch tube S3 and the same-name terminal of the primary side of the transformer T respectively. The positive electrode of the third capacitor C3 is connected to the drain of the third switch tube S3. The other end of the second inductor L2 is respectively connected to one end of the fourth inductor L4 and the positive electrode of the second capacitor C2. The drain of the second switching tube S2 is respectively connected to the other end of the fourth inductor L4, the source of the fourth switching tube S4, and the non-doping terminal of the primary side of the transformer T. The positive electrode of the fourth capacitor C4 is connected to the drain of the fourth switching tube S4. The doping terminal of the secondary side of the transformer T is respectively connected to the source of the fifth switching tube Q1 and the drain of the sixth switching tube Q2. The non-doping terminal of the secondary side of the transformer T is respectively connected to the negative electrode of the fifth capacitor C5 and the positive electrode of the sixth capacitor C6.

[0052] To simplify the analysis of the working phases of the interleaved parallel isolated bidirectional DC-DC converter provided in the embodiments of the present invention, the following definitions and assumptions are made:

[0053] The duty cycle of the switch is ,in, is the circuit's duty cycle, is the on-time of the switch tube (i.e. the time when the drive signal is high).

[0054] The phase shift angle is d , used to represent the lag or lead time of the switch drive signal on the first DC power supply V1 side and the second DC power supply V2 side. Wherein, d is the phase shift angle relative to the entire switching cycle ratio.

[0055] All components of the interleaved parallel isolated bidirectional DC-DC converter are ideal devices.

[0056] The capacitance values of the first capacitor C1 , the second capacitor C2 , the third capacitor C3 , the fourth capacitor C4 , the fifth capacitor C5 , and the sixth capacitor C6 are large enough, and the voltage across the capacitors remains constant during the switching cycle.

[0057] Transformer T turns ratio .

[0058] The steady-state analysis process of the interleaved parallel isolated bidirectional DC-DC converter provided in the embodiment of the present invention operating under single-phase shift control is as follows:

[0059] Under single-phase-shift control, the duty cycle of the drive signal for each switch is always D = 0.5. The first switch S1 and the second switch S2 in the staggered parallel structure on the first DC power supply V1 are turned on 180° out of phase. The first switch S1 and the third switch S3 are turned on in a complementary manner, the second switch S2 and the fourth switch S4 are turned on in a complementary manner, and the fifth switch Q1 and the sixth switch Q2 on the second DC power supply V2 are turned on in a complementary manner. d represents the phase shift angle between the DC source V1 and the second DC power supply V2 relative to the entire switching cycle. The value range of d is 0≤d≤1.

[0060] Working stage analysis when 0≤d≤0.5:

[0061] When 0≤d≤0.5, the power transmission situation is from the first DC power supply V1 side to the second DC power supply V2 side, that is, forward transmission. Figure 3 Draw the waveforms of the main components of the circuit under the condition of 0≤d≤0.5 and stable operation. Among them, S1 represents the drive signal of the first switch S1; S2 represents the drive signal of the second switch S2; S3 represents the drive signal of the third switch S3; S4 represents the drive signal of the fourth switch S4; Q1 represents the drive signal of the fifth switch Q1; Q2 represents the drive signal of the sixth switch Q2; Represents the potential difference between points a and b; Indicates the primary side voltage of the transformer; 、 They represent the leakage inductance of transformer T and L respectively. k voltage and current on the .

[0062] Combine Figure 3 Detailed analysis of the circuit's working status:

[0063] Stage t0~t1 Figure 4a In the staggered parallel structure, S2 and S3 are turned on, S1 and S4 are turned off, and the switch Q1 on the second DC power supply V2 is turned off, while Q2 is turned on. The first DC power supply V1 and inductors L1 and L3 charge the third capacitor C3, and the first DC power supply V1 charges the inductors L2 and L4. At this time, the following equation holds:

[0064]

[0065]

[0066]

[0067]

[0068] Transformer T leakage inductance L k The current and voltage are:

[0069]

[0070]

[0071] Stage t1~t2 Figure 4b At t1, leakage inductance L k Current Zero, then The reverse direction increases, S2 and S3 in the staggered parallel structure are turned on, S1 and S4 are turned off, the switch tube Q1 on the second DC power supply V2 is turned off, and Q2 is turned on. The first DC power supply V1, inductor L1, L3 charge the capacitor C3, and the current flows through the leakage inductor L k The relationship between current and voltage is the same as above:

[0072]

[0073]

[0074] Stage t2~t3 Figure 4c In the staggered parallel structure, S2 and S3 are turned on, S1 and S4 are turned off, the switch tube Q2 on the second DC power supply V1 is turned off, and Q1 is turned on. The capacitor C3 of the first DC power supply V1 is connected to the transformer T through the voltage s The lateral capacitor C5 is charged. At this time, the following equation is established:

[0075]

[0076]

[0077]

[0078] Flowing through the leakage inductance L k The relationship between current and voltage is:

[0079]

[0080]

[0081] The remaining three stages are symmetrical with the first half cycle, and the analysis is similar to the above. At this time, we can get the first half cycle flowing through the leakage inductance L k The current expression is:

[0082]

[0083] Working stage analysis when 0.5≤d≤1:

[0084] Figure 5 Draw the waveforms of the main components of the circuit when D-0.5≤d≤0.5 and it is working stably. Figure 6The working modal diagrams of the circuit in the first half cycle are given in the three stages t0~t1, t1~t2, and t2~t3 under the condition of D-0.5≤d≤0.5 and stable operation. The remaining three stages are symmetrical with the first half cycle, and the analysis method is similar to that when 0≤d≤0.5. At this time, it can be obtained that the leakage inductance L k The current expression is:

[0085]

[0086] Power characteristics analysis:

[0087] Based on the analysis of the working phase, the power characteristics of the converter under single phase shift control are calculated and analyzed:

[0088] When 0≤d≤0.5, Figure 3 It can be seen that the time for each work stage is:

[0089]

[0090]

[0091]

[0092]

[0093] is the switching frequency.

[0094] The leakage inductance L can be obtained k The upper current expression is:

[0095]

[0096] in, .

[0097] At this time, the transmission power P of the interleaved parallel isolated bidirectional DC-DC converter is:

[0098]

[0099] At this time, the leakage inductance L k Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0100]

[0101] For the convenience of analysis, the transmission power P is normalized to per unit value, and the power reference value is set to , and then we get:

[0102]

[0103] in, is the per-unit value of the transmission power P.

[0104] Similar to the above analysis and calculation, when 0.5≤d≤1, the time of each working stage is:

[0105]

[0106]

[0107]

[0108]

[0109] From the above analysis, we can get the leakage inductance L k The upper current expression is:

[0110]

[0111] Then we get:

[0112]

[0113] in, .

[0114] At this time, the transmission power P of the interleaved parallel isolated bidirectional DC-DC converter is:

[0115]

[0116] At this time, the leakage inductance L k Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0117]

[0118] Convert the transmission power P to per unit value and set the power reference value to , and then we get:

[0119]

[0120] Figure 7The power range of the converter under single-phase-shift control is demonstrated. Compared with an isolated full-bridge bidirectional DC-DC converter at the same reference power value, the interleaved parallel isolated bidirectional DC-DC converter has a wider power adjustment range under single-phase-shift control. Power regulation is achieved by adjusting the phase-shift angle parameter d. When the power is positive, energy is transferred from the first DC power supply V1 to the second DC power supply V2, indicating forward operation. When the power is negative, energy is transferred from the second DC power supply V2 to the DC source V1, indicating reverse operation.

[0121] Voltage matching and efficiency analysis:

[0122] The aforementioned analysis of the operating characteristics of a single-phase-shifted, interleaved, parallel, isolated bidirectional DC-DC converter at different phase-shift angles reveals that, when the boost stage has a fixed duty cycle of D = 0.5, the left side of transformer T essentially connects the output ports of two boost converters, each boosting the DC voltage to twice the value, to the primary winding of transformer T. Energy transfer from transformer T is achieved by alternating the outputs of the two boost converters, which combine positive and negative square waves with constant-amplitude DC currents. A precise 50% duty cycle also prevents DC magnetization of the transformer. On the secondary side of transformer T, polarity is reversed by connecting two equal-value capacitors in parallel to the load, then using switching devices Q1 and Q2 to alter the capacitor connected to the secondary side.

[0123] Under single-phase-shift control, the primary and secondary sides of transformer T both produce alternating positive and negative square waves with a duty cycle of 50%. Based on the aforementioned power analysis, the interleaved parallel isolated bidirectional DC-DC converter has four power transmission sub-states. The parameters in each state are shown in Table 1.

[0124] Table 1 Operating modes of the converter under single phase shift control

[0125]

[0126] Table 1 shows that of the four operating modes of the interleaved parallel isolated bidirectional DC-DC converter, two are for power output and two for power input. The two operating modes with opposite polarities of the primary and secondary voltages on the transformer T can generate a larger voltage difference across the transformer T and thus become the primary modes of power flow.

[0127] In practical converters, transformers are not completely ideal power devices. While the majority of power is transmitted via the main magnetic flux, leakage inductance also generates power losses. Given a given voltage level, transformer losses primarily depend on the currents flowing through the primary and secondary windings. Therefore, to maximize converter efficiency, it is necessary to minimize leakage inductance losses by controlling the current flowing through the transformer windings while ensuring power transmission.

[0128] Considering that DC-DC converters typically operate in power output modes with a small phase-shift angle and power input modes with a large phase-shift angle, the transformer spends a significant portion of its time in these two operating modes, where the primary and secondary voltages have the same polarity. To reduce transformer leakage losses in these two operating modes, it's necessary to reduce the voltage difference between the primary and secondary sides to limit the leakage current. Under ideal hardware design and control conditions, the primary and secondary voltages should be exactly equal, resulting in a constant leakage current and minimal losses. This is the ideal converter voltage matching solution for efficiency optimization.

[0129] Under single-phase shift control with a constant step-up ratio, voltage matching is primarily achieved by fine-tuning the transformer ratio. Figure 8 shows the transformer primary-secondary voltage difference and leakage inductance current for two different ratios. It can be seen that with voltage matching, the primary-secondary voltage difference is nearly zero, and the leakage inductance current is well maintained at a constant plateau value. Figure 9 The input and output power and conversion efficiency of the converter under different transformation ratios are displayed. It can be seen that although the power transfer value will be slightly reduced under the voltage matching transformation ratio, the efficiency is significantly improved, which can alleviate the heat dissipation pressure of the converter and extend its working life.

[0130] Zero current ripple analysis:

[0131] The voltage across the inductor L is known. The expression is:

[0132]

[0133] For the upper half of the circuit on the first DC power supply V1 side, in one switching cycle T s When S1 is turned on and S3 is turned off, Kirchhoff's voltage law (KVL) can be used to obtain:

[0134]

[0135]

[0136]

[0137] in, is the voltage across the inductor L1 when the switch tube S1 is turned on and S3 is turned off. It is the voltage across the inductor L3 when the switch tube S1 is turned on and S3 is turned off.

[0138] When S1 is off and S3 is on, Kirchhoff's voltage law (KVL) shows that:

[0139]

[0140]

[0141]

[0142] in, is the voltage across the inductor L1 when the switch tube S1 is turned off and S3 is turned on. It is the voltage across the inductor L3 when the switch tube S1 is turned off and S3 is turned on.

[0143] Under steady-state conditions, using the volt-second balance condition for inductor L1, we can obtain:

[0144]

[0145] Under steady-state conditions, using the volt-second balance condition for inductor L3 yields:

[0146]

[0147] In summary, we can get:

[0148]

[0149]

[0150]

[0151] exist Figure 2 In the topological circuit of , the working principles of the upper and lower parts of the circuit on the first DC power supply V1 side are the same, and similarly, we can obtain:

[0152]

[0153]

[0154]

[0155] Whether the switch is on or off, the voltage across the inductors L1 and L2 is 0. , the current flowing through the inductor is always constant. Therefore, under any duty cycle D, the inductors L1 and L2 have zero current ripple, and the total current is also zero ripple current.

[0156] Compared with the traditional single-phase Boost, two-phase interleaved parallel circuit, and three-phase parallel circuit, the converter proposed in this invention can achieve zero current ripple under any duty cycle D condition. Figure 10 A ripple rate comparison chart is given, where the zero ripple rate of the two-phase staggered parallel circuit is only achieved when D=0.5, and the zero ripple rate of the three-phase parallel circuit is only achieved when D=1 / 3 or D=2 / 3.

[0157] The steady-state analysis of the interleaved parallel isolated bidirectional DC-DC converter provided in the present invention operating under single-phase shift plus interleaved parallel control is as follows:

[0158] Single-phase-shift plus interleaved parallel control adds the duty cycle D of the switch tubes in the interleaved parallel structure to the single-phase-shift control. That is, the duty cycle D of the drive signal of each switch tube on the first DC power supply V1 side is variable, but the duty cycle of the drive signal of each switch tube on the second DC power supply V2 side is still 0.5. The present invention uses 0.5≤D≤1 as an example for detailed analysis. The switch tubes S1 and S2 of the interleaved parallel structure on the first DC power supply V1 side are turned on with a 180° phase difference, S1 and S3 are turned on complementarily, S2 and S4 are turned on complementarily, and the switch tubes Q1 and Q2 of the switched capacitor structure on the second DC power supply V2 side are turned on complementarily. At the same time, d represents the phase shift angle of the drive signal on the first DC power supply V1 side and the second DC power supply V2 side relative to the entire switching period T s The ratio of d is in the range of 0≤d≤1.

[0159] Figure 11 Draw the waveforms of the main components of the circuit under the condition of 0≤d≤D-0.5 and stable operation. Among them, S1 represents the drive signal of the first switch tube S1; S2 represents the drive signal of the second switch tube S2; S3 represents the drive signal of the third switch tube S3; S4 represents the drive signal of the fourth switch tube S4; Q1 represents the drive signal of the fifth switch tube Q1; Q2 represents the drive signal of the sixth switch tube Q2; u ab represents the potential difference between points a and b; u p Indicates the primary side voltage of the transformer; u Lk 、i Lk They represent the leakage inductance of transformer T and L respectively. k voltage and current on the .

[0160] Combine Figure 11 Detailed analysis of the circuit's working status:

[0161] Stage t0~t1 Figure 12a In the staggered parallel structure, S1 and S2 are turned on, S3 and S4 are turned off, the switch Q1 on the second DC power supply V2 is turned off, and Q2 is turned on. The first DC power supply V1 charges the inductors L1 and L3, and the inductors L2 and L4, and at the same time, the transformer v s The second DC power supply V2 is discharged from the side. At this time, the following equation is established:

[0162]

[0163]

[0164]

[0165]

[0166] Leakage inductance L k The voltage and current on are:

[0167]

[0168]

[0169] Stage t1~t2 Figure 12b In the staggered parallel structure, S1 and S2 are turned on, S3 and S4 are turned off, the switch Q2 on the second DC power supply V2 is turned off, and Q1 is turned on. The first DC power supply V1 charges the inductors L1 and L3, and the inductors L2 and L4. At the same time, the capacitor C5 is connected to the capacitor C5 through the transformer V1. p The first DC power supply V1 is discharged from the side. At this time, the following equation is established:

[0170]

[0171]

[0172]

[0173]

[0174] Stage t2~t3 Figure 12c In the staggered parallel structure, S2 and S3 are turned on, S1 and S4 are turned off, the switch Q2 on the second DC power supply V2 is turned off, Q1 turns on the first DC power supply V1, inductor L1 and L3 to charge capacitor C3, and capacitor C3 is charged through transformer v s The second DC power supply V2 is discharged from the side. At this time, the following equation is established:

[0175]

[0176]

[0177]

[0178]

[0179] Leakage inductance L k The voltage and current on are:

[0180]

[0181]

[0182] The remaining three phases are symmetrical with the first half cycle, and the analysis is similar to the above. At this time, the current expression flowing through the leakage inductance in the first half cycle can be obtained as:

[0183]

[0184] in, 、 、 、 、 .

[0185] Power characteristics analysis:

[0186] Based on the analysis of the working conditions, the power characteristics of the converter under single-phase shift plus interleaved parallel control are calculated and analyzed:

[0187] When 0≤d≤D-0.5, the current magnitude at each moment can be calculated from the aforementioned leakage inductance current expression, which is:

[0188]

[0189] in, .

[0190] At this time, the transmission power P of the interleaved parallel isolated bidirectional DC-DC converter is:

[0191]

[0192] At this time, the leakage inductance L k Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0193]

[0194] Similarly, for the convenience of analysis, the transmission power P is normalized to per unit value, and the power reference value is set to Then we get:

[0195]

[0196] When D-0.5≤d≤0.5, the current at each moment can be calculated using the aforementioned leakage inductance current expression, which is:

[0197]

[0198] in, .

[0199] At this time, the transmission power P of the interleaved parallel isolated bidirectional DC-DC converter is:

[0200]

[0201] At this time, the leakage inductance Lk Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0202]

[0203] Similarly, for the convenience of analysis, the transmission power P is normalized to per unit value, and the power reference value is set to Then we get:

[0204]

[0205] When 0.5≤d≤D, the current at each moment can be calculated using the aforementioned leakage inductance current expression, which is:

[0206]

[0207] in, .

[0208] At this time, the transmission power of the converter is:

[0209]

[0210] At this time, the leakage inductance L k Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0211]

[0212] Similarly, for the convenience of analysis, the transmission power P is normalized to per unit value, and the power reference value is set to Then we get:

[0213]

[0214] When D≤d≤1, the current at each moment can be calculated using the aforementioned leakage inductance current expression, which is:

[0215]

[0216] in, .

[0217] At this time, the transmission power of the converter is:

[0218]

[0219] At this time, the leakage inductance L k Maximum current , which is equivalent to the current stress of the switch tube on the first DC power supply V1 side of the interleaved parallel isolated bidirectional DC-DC converter:

[0220]

[0221] Similarly, for the convenience of analysis, the transmission power P is normalized to per unit value, and the power reference value is set to Then we get:

[0222]

[0223] Figure 13 The power range of the converter under single-phase-shifted and interleaved parallel control is demonstrated. Compared with an isolated full-bridge bidirectional DC-DC converter and a single-phase-shifted control scheme, under the same baseline power value, the interleaved parallel isolated bidirectional DC-DC converter has a wider power regulation range under single-phase-shifted and interleaved parallel control. Furthermore, by increasing the duty cycle D, the converter's transmission power is determined by both the phase-shift angle parameter d and the duty cycle D. Multiple sets of corresponding parameter pairs (d, D) can be used for the same transmission power, providing greater flexibility in power regulation. When the power is positive, energy is transferred from the first DC power supply V1 to the second DC power supply V2, indicating forward operation. When the power is negative, energy is transferred from the second DC power supply V2 to the first DC power supply V1, indicating reverse operation.

[0224] Voltage matching and efficiency analysis:

[0225] From the aforementioned voltage matching analysis of the DC-DC converter for single-phase-shift control, it can be seen that minimizing the calculated voltage difference when the primary and secondary sides of the transformer have the same polarity helps control the leakage current during converter operation, thereby improving power transmission efficiency.

[0226] However, in actual DC-DC converters, once the isolation transformer ratio is determined, it is difficult to change. Therefore, fine-tuning the transformer ratio to achieve dynamic voltage matching during converter operation is technically difficult. Due to limited capacity on the energy storage side, the voltage slowly drops during continuous power output and slowly rises again during continuous power input, indicating a positive correlation between the energy storage voltage and the remaining energy. To address this voltage variation, voltage matching can be achieved by adjusting the boost duty cycle of the interleaved boost cells.

[0227] For the interleaved parallel boost structure, the single-phase shift control analyzed previously fixed the duty cycle D at 0.5, resulting in an alternating positive and negative square wave output. However, if single-phase shift plus interleaved parallel control is used, varying the duty cycle D can cause the voltages across the transformer's primary winding to reach their peak values or to reach zero, resulting in a zero primary voltage. These three primary voltage values and the two secondary voltage values together constitute the six operating modes under single-phase shift plus interleaved parallel control, as shown in Table 2.

[0228] Table 2 Working modes under single-shift phase addition interleaved parallel control

[0229]

[0230] It can be seen from Table 2 that the converter's operating modes include one more for power input and one for output on the basis of the four modes of single-phase shift control. Among them, the two operating modes with opposite polarities of primary and secondary voltages can produce a larger voltage difference on the transformer and thus become the main modes of power flow.

[0231] In practical converters, transformers are not completely ideal power devices. While the majority of power is transmitted via the main magnetic flux, leakage inductance also generates power losses. Given a given voltage level, transformer losses primarily depend on the currents flowing through the primary and secondary windings. Therefore, to maximize converter efficiency, it is necessary to minimize leakage inductance losses by controlling the current flowing through the transformer windings while ensuring power transmission.

[0232] Considering that DC-DC converters generally operate in power output modes with a small phase-shift angle and power input modes with a large phase-shift angle, the two operating modes with the same polarity of the primary and secondary voltages of the transformer account for a significant portion of the time. Furthermore, the two newly added operating modes under single-phase-shifted interleaved parallel control have an irreconcilable voltage difference, which also increases leakage current. To reduce transformer leakage losses during normal converter operation, it is necessary to reduce the transformer primary-secondary voltage difference to limit leakage current. Under ideal hardware design and control conditions, the primary and secondary voltages should be completely equal, resulting in a constant leakage current and minimal losses. This is the converter voltage matching solution for efficiency optimization.

[0233] With the transformer ratio already determined, voltage matching is primarily achieved by fine-tuning the boost ratio of the interleaved boost modules. Figure 14 shows the transformer primary-secondary voltage difference and leakage current for two different boost ratios. It can be seen that with voltage matching, the primary-secondary voltage difference is nearly zero, and the leakage current remains constant at a stable plateau. Figure 15The input and output power and conversion efficiency of the converter under different step-up ratios are shown. It can be seen that although the power transfer value will be slightly reduced under the voltage-matched ratio, the efficiency is significantly improved, which can alleviate the heat dissipation pressure of the converter and extend its working life.

[0234] Zero current ripple analysis:

[0235] The voltage across the inductor L is known. The expression is:

[0236]

[0237] For the upper half of the circuit on the first DC power supply V1 side, in one switching cycle T s When S1 is on and S3 is off, Kirchhoff's voltage law (KVL) can be used to obtain:

[0238]

[0239]

[0240]

[0241] in, is the voltage across the inductor L1 when the switch tube S1 is turned on and S3 is turned off. It is the voltage across the inductor L3 when the switch tube S1 is turned on and S3 is turned off.

[0242] When S1 is off and S3 is on, Kirchhoff's voltage law (KVL) shows that:

[0243]

[0244]

[0245]

[0246] in, is the voltage across the inductor L1 when the switch tube S1 is turned off and S3 is turned on. It is the voltage across the inductor L3 when the switch tube S1 is off and S3 is on.

[0247] Under steady-state conditions, using the volt-second balance condition for inductor L1, we can obtain:

[0248]

[0249] Under steady-state conditions, using the volt-second balance condition for inductor L3 yields:

[0250]

[0251] From the above we can get:

[0252]

[0253]

[0254]

[0255] In the topological circuit of the converter of the present invention, the circuit operating principles of the upper and lower parts of the first DC power supply V1 are the same. Similarly, the following can be obtained:

[0256]

[0257]

[0258]

[0259] It can be seen that the voltage across the inductors L1 and L2 is 0 regardless of whether the switches are on or off. , the current flowing through the inductor is always constant. Therefore, under any duty cycle D, the inductors L1 and L2 have zero current ripple, and the total current is also zero ripple current.

[0260] Similarly, compared with the traditional single-phase Boost, two-phase interleaved parallel circuit, and three-phase parallel circuit, the converter proposed in the present invention can achieve zero current ripple under any duty cycle D, further demonstrating the zero ripple advantage of the converter proposed in the present invention. The ripple rate comparison chart is shown in Figure 8.

[0261] The bidirectional DC-DC converter provided in the embodiment of the present invention is simulated and verified, and the parameters of each component are shown in Table 3.

[0262] Table 3 Parameter selection of each component in the converter

[0263]

[0264] The converter operating power is set to 2kW. From the converter parameters, it can be seen that the converter's boost ratio is V2 / V1=400 / 50=8. Through the previous analysis of the converter's single-phase-shifted control and single-phase-shifted plus staggered parallel control, it can be seen that when the latter is running, the voltage on the primary side of the transformer will be zero, causing the transformer leakage inductance current to increase further compared to single-phase-shifted control. Therefore, setting the converter's rated operating state to single-phase-shifted control helps improve the converter's power transmission efficiency. Under single-phase-shifted control, the staggered parallel Boost's boost ratio is 1:2. In order to achieve the required total boost ratio, the transformer's primary-to-secondary turns ratio should be set to 1:2.

[0265] In the single-phase shift control mode, the duty cycle D of all switches is set to 0.5 and d is set to 0.49. At this time, the actual power of the converter is 2.151 kW, which is slightly different from the theoretical value of 1.96 kW. 2.1 kW is the total power of the first DC power supply V1, which includes the part caused by component losses. This is within a reasonable range. The current and voltage waveforms flowing through the first inductor L1 and the second inductor L2 are as follows: Figure 16 、 17 As shown in the figure, it can be seen that the current flowing through the inductor is almost constant, with a variation range of only 0.09A, and the current ripple rate is only 0.38%, completely achieving zero ripple; the voltage across the inductor is approximately 0V, and only fluctuates within the range of ±1V, which is consistent with the theory; increasing the inductance values of inductors L1 and L2 and the capacitance values of capacitors C1 and C2 will further reduce the variation range of the voltage and current of the inductor. The current flowing through the first DC power supply V1 is as follows: Figure 18 As shown in the figure, the total input current is still almost constant, with a variation range of only 0.14A and a current ripple rate of only 0.32%, which completely achieves zero current ripple.

[0266] Similarly, in the single-phase shifted interleaved parallel control mode, the duty cycle D of the first to fourth switches S1-S4 is set to 0.8, the duty cycle D of the fifth to sixth switches Q1-Q2 is set to 0.5, and d is set to 0.64. At this time, the actual power of the converter is 2.172 kW, which is slightly different from the theoretical value of 2kW. 2.172 kW is the total power of the first DC power supply V1, which includes the part caused by component losses, which is within a reasonable range. The current and voltage waveforms flowing through the first inductor L1 and the second inductor L2 are as follows: Figure 19 、 20 As shown in the figure, it can be seen that the current flowing through the inductor is almost constant, with a variation range of only 0.03A, and the current ripple rate is only 0.11%, completely achieving zero ripple; the voltage across the inductor is approximately 0V, fluctuating only within the range of ±1V, which is consistent with the theory; increasing the inductance values of inductors L1 and L2 and the capacitance values of capacitors C1 and C2 will further reduce the variation range of the inductor voltage and current. The current flowing through the DC source V1 is as follows Figure 21 As shown in the figure, the total input current is still almost constant, with a variation range of only 0.07A and a current ripple rate of only 0.13%, which completely achieves zero current ripple.

[0267] In order to truly reflect the impact of voltage fluctuations on the power transmission efficiency of the energy storage side during converter operation, the voltage value of the energy storage side is first set to a value that satisfies the voltage matching under single-phase shift control. Then, the voltage value of the energy storage side is increased and decreased to simulate the voltage fluctuations caused by energy flow. The input and output power and efficiency of the voltage matching optimization and non-optimization are compared. Figure 22As shown in the figure, it can be seen that as the voltage deviates from the rated value, the efficiency of the converter without any measures continues to decline. However, the voltage matching optimization can effectively suppress this phenomenon and ensure the high efficiency of the converter under various working conditions.

[0268] In summary, the theoretical analysis and experimental results consistently verify the correctness of the circuit and realize constant voltage matching, zero current ripple, and wide-range power regulation functions. The high efficiency characteristics of the converter proposed in the present invention enable the converter proposed in the present invention to be used in situations where there are high requirements for actual efficiency. Therefore, it can be applied to the front-stage DC-DC link of the energy storage type dynamic voltage restorer.

[0269] The interleaved parallel isolated bidirectional DC-DC converter provided by the present invention can, on the one hand, achieve dynamic voltage matching by adjusting the transformer's step-up ratio in real time when the DC side voltage fluctuates, thereby ensuring low loss and high efficiency of the converter under various operating conditions. On the other hand, it can achieve zero current ripple under any conduction duty cycle, any DC voltage, and any transformer turns ratio. Furthermore, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention has a wide power operating range. Therefore, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention solves the technical problems of existing bidirectional DC-DC converters used in energy storage dynamic voltage restorers, such as difficulty in adapting to voltage matching, large current ripple, and susceptibility to high voltage stress generated by the DC bus voltage.

[0270] At the same time, the interleaved parallel isolated bidirectional DC-DC converter provided by the present invention avoids the use of large electrolytic capacitors in the access side of the energy storage system and the DC-DC circuit, which can extend the service life of the energy storage battery and the interleaved parallel isolated bidirectional DC-DC converter.

[0271] The terms "first," "second," and the like in the present invention are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatus.

[0272] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An interleaved parallel isolated bidirectional DC-DC converter, characterized in that: The device comprises a first DC power supply, a second DC power supply, a first inductor, a second inductor, a third inductor, a fourth inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, and a transformer; The positive electrode of the first DC power supply is respectively connected to one end of the first inductor and one end of the second inductor, and the negative electrode of the first DC power supply is respectively connected to the source electrode of the first switching tube, the source electrode of the second switching tube, the negative electrode of the first capacitor, the negative electrode of the second capacitor, the negative electrode of the third capacitor, and the negative electrode of the fourth capacitor; The positive electrode of the second DC power supply is respectively connected to the drain of the fifth switching tube and the positive electrode of the fifth capacitor, the negative electrode of the second DC power supply is respectively connected to the source of the sixth switching tube and the negative electrode of the sixth capacitor, the other end of the first inductor is respectively connected to one end of the third inductor and the positive electrode of the first capacitor, the drain of the first switching tube is respectively connected to the other end of the third inductor, the source of the third switching tube and the same-name terminal of the primary side of the transformer, the positive electrode of the third capacitor is connected to the drain of the third switching tube, the other end of the second inductor is respectively connected to one end of the fourth inductor and the positive electrode of the second capacitor, the drain of the second switching tube is respectively connected to the other end of the fourth inductor, the source of the fourth switching tube and the non-same-name terminal of the primary side of the transformer, the positive electrode of the fourth capacitor is connected to the drain of the fourth switching tube, the same-name terminal of the secondary side of the transformer is respectively connected to the source of the fifth switching tube and the drain of the sixth switching tube, and the non-same-name terminal of the secondary side of the transformer is respectively connected to the negative electrode of the fifth capacitor and the positive electrode of the sixth capacitor.

2. The interleaved parallel isolated bidirectional DC-DC converter according to claim 1, characterized in that: The first switch tube and the second switch tube are turned on 180 degrees apart, the first switch tube and the third switch tube are turned on complementarily, the second switch tube and the fourth switch tube are turned on complementarily, and the fifth switch tube and the sixth switch tube are turned on complementarily.

3. The interleaved parallel isolated bidirectional DC-DC converter according to claim 2, characterized in that: The duty cycle of the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube is 0.

5.

4. The interleaved parallel isolated bidirectional DC-DC converter according to claim 2, characterized in that: The duty cycle of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube is 0.8, and the duty cycle of the fifth switch tube and the sixth switch tube is 0.

5.

5. The interleaved parallel isolated bidirectional DC-DC converter according to claim 2, characterized in that: The ratio of the phase shift angle between the first DC power supply side and the second DC power supply side relative to the entire switching period is [0, 1].

6. The interleaved parallel isolated bidirectional DC-DC converter according to claim 1, characterized in that: The turns ratio of the transformer is 1:

2.

7. The interleaved parallel isolated bidirectional DC-DC converter according to claim 1, characterized in that: The output voltage of the first DC power supply is 50V.

8. The interleaved parallel isolated bidirectional DC-DC converter according to claim 7, characterized in that: The output voltage of the second DC power supply is 400V.

9. The interleaved parallel isolated bidirectional DC-DC converter according to claim 8, characterized in that: The inductance values of the first inductor, the second inductor, the third inductor, and the fourth inductor are all 100µH.

10. The interleaved parallel isolated bidirectional DC-DC converter according to claim 9, characterized in that: The capacitance values of the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, and the sixth capacitor are all 110 µF.

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