A light storage integrated three-port DC-DC converter

Abstract

This invention discloses an integrated three-port DC-DC converter combining photovoltaic (PV) and energy storage, comprising a photovoltaic (PV) power generation port unit, an energy storage port unit, and an output port unit. The PV power generation port is connected in parallel with a DC bus capacitor via a first four-transistor Buck-Boost converter for unidirectional energy input. The energy storage port is connected in parallel with a DC bus capacitor via a second four-transistor Buck-Boost converter for bidirectional energy flow. The output port unit includes a full-bridge LLC resonant converter for converting the DC bus voltage into the required output voltage and outputting it. The output bridge arm switches of the two Buck-Boost converters are multiplexed with the primary-side switches of the full-bridge LLC resonant converter, and a phase-shift modulation strategy is used to achieve soft switching of all switches. This invention can effectively reduce the number of components and achieve high power density, high conversion efficiency, and high reliability in the integrated PV and energy storage system.

Description

Technical Field

[0001] This invention belongs to the field of power electronic converter technology, specifically relating to an integrated three-port DC-DC converter that combines photovoltaic and energy storage. Background Technology

[0002] With the continuous development of photovoltaic power generation and energy storage technologies, integrated photovoltaic-energy storage systems are gradually becoming an important interface between the new energy generation side and the energy consumption side. These systems typically integrate photovoltaic power generation units and energy storage batteries, using power electronic conversion devices to achieve coordinated energy dispatch and stable output, addressing issues such as large fluctuations in photovoltaic output and rapid changes in load power. In integrated photovoltaic-energy storage systems, photovoltaic power generation units generally act as unidirectional DC power sources, while energy storage batteries act as bidirectional energy units with charge and discharge capabilities. Both need to work together to provide stable and continuous DC power to the load side under electrically isolated conditions. Therefore, this application scenario places comprehensive requirements on power conversion devices, requiring them to simultaneously possess multi-port access capabilities for both photovoltaic and energy storage, high-efficiency isolated output capabilities, and high-power-density integration capabilities.

[0003] In existing integrated photovoltaic (PV) and energy storage systems, photovoltaic (PV) power generation units and energy storage batteries are typically configured with independent power converters connected to the load side or DC bus. For example, a unidirectional DC / DC converter is used on the PV side to achieve maximum power point tracking, while a bidirectional DC / DC converter is used on the energy storage side to achieve battery charge and discharge control. Although this approach can meet basic energy management requirements, it requires multiple power conversion units to work together, resulting in a large number of power devices and energy conversion stages, which increases system size and cost, and limits overall energy conversion efficiency. To improve system integration and reduce the number of power conversion stages, existing research has proposed integrating the PV port, energy storage port, and load port into a single isolated power conversion structure, forming a three-port PV-energy storage DC / DC converter.

[0004] However, existing three-port topologies often achieve energy interaction by configuring independent bridge arm power units for each port or by expanding the number of ports using multi-winding high-frequency transformers. This leads to a significant increase in the number of power switching devices as the number of ports increases, which not only complicates the drive circuit and control logic but also increases switching and conduction losses, limiting further improvements in system efficiency and power density. Furthermore, the energy regulation relationship between multiple ports is complex. Under conditions of frequent changes in photovoltaic output and energy storage power, power coupling can easily occur between ports, making control strategy design more difficult. Moreover, in integrated photovoltaic and energy storage applications, three-port converters typically need electrical isolation capabilities to meet safety and system compatibility requirements. However, existing isolated multi-port DC / DC converters often struggle to ensure that each power switching device remains in a soft-switching state under wide load ranges or large variations in multi-port power distribution, leading to hard switching phenomena, resulting in significant switching losses and electromagnetic interference, affecting system efficiency and reliability. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the existing technology by providing an integrated three-port DC-DC converter for photovoltaic-storage integration. This integrated three-port DC / DC converter, designed for photovoltaic-storage integration applications, achieves high efficiency and high power density operation over a wide operating range by reducing the number of power switching devices, simplifying the power channel structure, implementing reasonable modulation control, and introducing soft switching, while meeting the requirements of unidirectional photovoltaic power supply, bidirectional energy flow from energy storage, and isolated output. The converter should ensure that energy from the photovoltaic power generation port is transferred only to the output side, avoiding backfeeding; simultaneously, it should enable flexible switching between charging and discharging at the energy storage battery port; and ensure sufficient electrical decoupling between the two front-end ports, simplifying and stabilizing the control strategy. Furthermore, bridge arm multiplexing reduces the number of devices, further increasing the converter's power density; appropriate modulation strategies enable soft switching of all switching transistors, improving efficiency; and it should maintain high efficiency and high power density at the isolated output.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A photovoltaic-storage integrated three-port DC-DC converter, wherein the photovoltaic-storage integrated three-port DC-DC converter comprises, in sequence, a photovoltaic power generation port unit, an energy storage port unit, and an output port unit;

[0008] The photovoltaic power generation port unit includes a photovoltaic power generation port and a first four-transistor Buck-Boost converter. The photovoltaic power generation port is connected to the DC bus capacitor C through the first four-transistor Buck-Boost converter. bus Parallel connection is used to achieve unidirectional energy input;

[0009] The energy storage port unit includes an energy storage port and a second four-transistor Buck-Boost converter. The energy storage port is connected to the DC bus capacitor C through the second four-transistor Buck-Boost converter. bus Parallel connection is used to achieve bidirectional energy flow;

[0010] The output port unit includes a full-bridge LLC resonant converter, which is used to convert the DC bus voltage into the required output voltage and output energy to the load.

[0011] The output bridge arm switches of the first four-transistor Buck-Boost converter and the second four-transistor Buck-Boost converter are multiplexed with the primary-side switches of the full-bridge LLC resonant converter. A phase-shift modulation strategy is used to control the inductor current of the first four-transistor Buck-Boost converter and the second four-transistor Buck-Boost converter to achieve soft switching of all switches.

[0012] To optimize the above technical solution, the specific measures also include:

[0013] The aforementioned first four-transistor Buck-Boost converter includes inductor L a Switching transistor Q A1 Q A2 Q A3 Q A4 and its anti-parallel diode D A1 D A2 D A3 D A4 junction capacitance C A1 C A2 C A3 C A4 The positive terminal of the photovoltaic power generation port and Q A1 The drains are connected, Q A1 source and Q A2 The drain and L a One end is connected, L a The other end and Q A3 source and Q A4 The drains are connected, Q A3 The drain and C bus One end is connected, C bus The other end and Q A4 source and Q A2 The source electrode is connected to the negative terminal of the photovoltaic power generation port.

[0014] The aforementioned second four-transistor Buck-Boost converter includes inductor L b Switching transistor Q B1 Q B2 Q B3Q B4 and its anti-parallel diode D B1 D B2 D B3 D B4 junction capacitance C B1 C B2 C B3 C B4 The positive terminal of the energy storage port is connected to Q. B1 The drains are connected, Q B1 source and Q B2 The drain and L b One end is connected, L b The other end and Q B3 source and Q B4 The drains are connected, Q B3 The drain and C bus One end is connected, C bus The other end and Q B4 source and Q B2 The source electrode is connected to the negative terminal of the energy storage port.

[0015] The aforementioned full-bridge LLC resonant converter includes a resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r Output filter capacitor C o 1 Rectifier diode D R1 D R2 D R3 D R4 and load R Ld Its original side bridge arm reuses Q A3 and Q A4 Q B3 and Q B4 R Ld Both ends are output ports; among them, the switching transistor Q A1 and Q A2 Q B1 and Q B2 For non-reusable bridge arms, Q A3 and Q A4 Q B3 and Q B4 For reused bridge arm; reused bridge arm Q A3 Q A4 Q B3 Q B4 The duty cycle is fixed at 50%, and Q A3 and Q B4 Simultaneous on / off, Q A4 and Q B3 Simultaneous on / off; the Q A3The source and Q A4 The drain and L r One end is connected, L r The other end and L m one end and T r Connect one end of the original edge, T r The other end of the original side is connected to L m The other end and C r One end is connected, C r The other end and Q B3 The source and Q B4 The drains are connected; T r One end of the secondary side is connected to D R1 anode and D R3 The cathode is connected, D R1 cathode and D R2 Cathode and C o one end and R Ld One end is connected, T r The other end of the secondary side is connected to D R2 anode and D R4 The cathode is connected, D R3 anode and D R4 anode and C o The other end and R Ld The other end is connected.

[0016] The aforementioned integrated photovoltaic-storage three-port DC-DC converter has four power transmission modes: Mode 1, where the photovoltaic power generation port and the energy storage port supply energy to the output port; Mode 2, where the photovoltaic power generation port supplies energy to both the energy storage port and the output port; Mode 3, where the photovoltaic power generation port supplies energy to the output port alone; and Mode 4, where the energy storage port supplies energy to the output port alone. In Mode 1, both the first and second four-transistor Buck-Boost converters operate in forward power transmission mode. In Mode 2, the first four-transistor Buck-Boost converter operates in forward power transmission mode, and the second four-transistor Buck-Boost converter operates in reverse power transmission mode. In Mode 3, the second four-transistor Buck-Boost converter does not operate, and the first four-transistor Buck-Boost converter operates in forward power transmission mode. In Mode 4, the first four-transistor Buck-Boost converter does not operate, and the second four-transistor Buck-Boost converter operates in forward power transmission mode. In all four modes, the full-bridge LLC resonant converter operates in forward power transmission mode.

[0017] The aforementioned Mode 1 includes 14 switching modes, namely:

[0018] Switching mode 1, corresponding to time [t0, t1]: at time t0, Q is turned off. A1L a Inductor current i La Give Q A1 C A1 Charging, while simultaneously supplying Q A2 C A2 Discharge; at time t1, C A1 The voltage is charged to V PV Meanwhile, C A2 The voltage is set to zero, Q A2 anti-parallel diode D A2 Natural conduction, at which point Q can be turned on with zero voltage. A2 Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is the energy storage port voltage V. bat i Lb Linear increase; L r and C r Resonant operation, D R1 and D R4 Turn on, and turn on transformer T r Primary voltage clamped to NV o Transformer T r Energy is transferred from the primary edge to the secondary edge, L m excitation current i Lm The linear increase, where N is the transformer T r The turn edge of the primary and secondary sides, V o The output voltage of the output port;

[0019] Switching mode 2, corresponding to time [t1, t2]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is V bus C bus Voltage applied, i La Linear decrease; Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Continue resonant operation;

[0020] Switching mode 3, corresponding to time [t2, t3]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is -V bus i La Linear decrease; Q B1 and Q B4Conduction, applied to L b The voltage across the terminals is V bat i Lb The resonant current i increases linearly; at time t2, the resonant current i Lr Resonance with excitation current i Lm Equal, T r The primary side no longer transfers energy to the secondary side, and the current in the secondary rectifier diode naturally decreases to zero, achieving zero-current turn-off; thereafter, L m L r and C r The three elements resonate and work together, R Ld By C o powered by;

[0021] Switching mode 4, corresponding to times [t3, t4]: at time t3, Q is turned off. A3 i Lr Give Q A3 C A3 Charging, while simultaneously supplying Q A4 C A4 Discharge; at time t4, C A3 The voltage is charged to V bus Meanwhile, C A4 The voltage is set to zero, Q A4 anti-parallel diode D A4 Natural conduction, at which point Q can be turned on with zero voltage. A4 Similarly, at time t3, Q is turned off. B4 It can turn on Q with zero voltage. B3 L m L r and C r The three continue to resonate, R Ld By C o powered by;

[0022] Switching mode 5, corresponding to time [t4, t5]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bat -V bus V bat >V bus i Lb Linear increase; L r and C r Resonant operation, T r secondary side D R2 and D R3 Conducting, will Tr Primary voltage v p Clamping to -NV o T r Energy is transferred from the primary side to the secondary side, and the excitation current i Lm Linear decrease;

[0023] Switching mode 6, corresponding to time [t5, t6]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keep it unchanged; at time t5, turn off Q. B2 i Lb Give Q B2 C B2 Charging, while simultaneously supplying Q B1 C B1 Discharge; at time t6, C B2 The voltage is charged to V bat Meanwhile, C B1 The voltage is set to zero, Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage. B1 L r and C r Continue resonant operation;

[0024] Switching mode 7, corresponding to time [t6, t7]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0025] Switching mode 8, corresponding to time [t7, t8]: at time t7, Q is turned off. A2 i La Give Q A2 C A2 Charging, while simultaneously supplying Q A1 C A1 Discharge; at time t8, C A2 The voltage is charged to V PV Meanwhile, C A1 The voltage is set to zero, Q A1 anti-parallel diode D A1 Natural conduction, at which point Q can be turned on with zero voltage.A1 Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0026] Switching mode 9, corresponding to time [t8, t9]: Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0027] Switching mode 10, corresponding to time [t9, t 10 Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; at time t9, i Lr Resonance with i Lm Equal, T r The current in the secondary-side rectifier diode naturally decreases to zero, achieving zero-current turn-off; thereafter, L m L r and C r The three elements resonate and work together, R Ld By C o powered by;

[0028] Switching mode 11, corresponding to time [t] 10 ,t 11 ]: In t 10 At any time, turn off Q. A4 i La Give Q A4 C A4 Charging, while simultaneously supplying Q A3 C A3 Discharge; at t 11 At that moment, CA4 The voltage is charged to V bus Meanwhile, C A3 If the voltage is set to zero, then Q A3 anti-parallel diode D A3 Natural conduction, at which point Q can be turned on with zero voltage. A3 Similarly, in t 10 At any time, turn off Q. B3 It can turn on Q with zero voltage. B4 L m L r and C r The three continue to resonate, R Ld By C o powered by;

[0029] Switching mode 12, corresponding to time [t] 11 ,t 12 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus V PV >V bus i La linearly increasing; Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i Lb Remain unchanged; L r and C r Resonant operation, T r secondary side D R1 and D R4 Conducting, will T r Primary voltage v p Clamping to NV o T r Energy is transferred from the primary edge to the secondary edge, i Lm Linear increase;

[0030] Switching mode 13, corresponding to time [t] 12 ,t 13 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La Linear increase; at t 12 At any time, turn off Q. B2 i Lb Give Q B2 C B2 Charging, while simultaneously supplying Q B1 CB1 Discharge; at t 13 At that moment, C B2 The voltage is charged to V bat Meanwhile, C B1 If the voltage is set to zero, then Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage. B1 L r and C r Continue resonant operation;

[0031] Switching mode 14, corresponding to time [t] 13 ,t 14 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La linearly increasing; Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Continue resonant operation.

[0032] The aforementioned phase-shifting modulation strategy includes: for the first four-transistor Buck-Boost converter, Q... A1 Before Q A3 Off, Q A3 Before Q A2 Off, Q A2 Before Q A4 Off, Q A4 Before Q A1 Off; Q A1 Q A2 Complementary conduction, Q A3 Q A4 The duty cycle is fixed at 50%, controlling Q. A1 Duty cycle D ya and Q A1 With Q A4 Phase shift angle D at the activation time θa , making L a The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching of all switching transistors.

[0033] The aforementioned phase-shifting modulation strategy includes: for the second four-transistor Buck-Boost converter, in the forward power transfer mode, Q... B1 Before Q B3 Off, Q B3 Before QB2 Off, Q B2 Before Q B4 Off, Q B4 Before Q B1 Off; in reverse energy transfer mode, Q B3 Before Q B1 Off, Q B1 Before Q B4 Off, Q B4 Before Q B2 Off, Q B2 Before Q B3 Off; Q B1 Q B2 Complementary conduction, Q B3 Q B4 The duty cycle is fixed at 50%, controlling Q. B1 Duty cycle D yb and Q B1 With Q B4 Phase shift angle D at the activation time θb , making L b The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching of all switching transistors.

[0034] The present invention has the following beneficial effects:

[0035] This invention innovates the circuit topology based on two four-transistor Buck-Boost converters and a full-bridge LLC resonant converter. It multiplexes the primary-side switches of the full-bridge LLC resonant converter and the output bridge arm switches of the two four-transistor Buck-Boost converters. Compared to traditional three-port DC-DC converters, this invention's three-port DC-DC converter enables flexible multi-source management, soft switching of all switches, and effectively reduces the number of components through bridge arm multiplexing. This invention also provides electrical isolation between the input and output voltages, better protecting downstream equipment, and allows for wide-range voltage regulation, high power density, high conversion efficiency, and high reliability.

[0036] In this invention, the photovoltaic power generation port and the energy storage port are each connected to an independent four-transistor Buck-Boost converter. The four-transistor Buck-Boost converter corresponding to the photovoltaic power generation port has only unidirectional buck-boost capability, while the four-transistor Buck-Boost converter corresponding to the energy storage port has bidirectional buck-boost capability. The output bridge arm switches of each four-transistor Buck-Boost converter are multiplexed with the primary-side switches of the full-bridge LLC resonant converter, and then power is supplied to the load through an isolated LLC resonant converter. This structure satisfies the different energy flow requirements of unidirectional and bidirectional sources while avoiding energy interference between different ports. Bridge arm multiplexing reduces the number of switches and increases power density. The modulation strategy used achieves soft switching of all switches. The soft-switching characteristics of the LLC resonant converter enable soft switching of the secondary-side diodes, further improving efficiency and power density. The integrated three-port DC-DC converter of the present invention, which integrates photovoltaic and energy storage, effectively reduces the number of devices and control complexity by reusing bridge arms while ensuring functional integrity. It can achieve full-domain soft switching, high power density, electrical isolation and flexible management of multiple sources, making it suitable for DC power supply scenarios of photovoltaic and energy storage integration. Attached Figure Description

[0037] Figure 1 The circuit structure of an integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0038] Figure 2 The waveform diagram shows the working state of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0039] Figure 3a The equivalent circuit diagram of the switching mode 1 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0040] Figure 3b The equivalent circuit diagram of the switching mode 2 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0041] Figure 3c The equivalent circuit diagram of the switching mode 3 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0042] Figure 3d The equivalent circuit diagram of the switching mode 4 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0043] Figure 3e The equivalent circuit diagram of the switching mode 5 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0044] Figure 3f The equivalent circuit diagram of the switching mode 6 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0045] Figure 3gThe equivalent circuit diagram of the switching mode 7 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0046] Figure 3h The equivalent circuit diagram of the switching mode 8 for the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0047] Figure 3i The equivalent circuit diagram of the switching mode 9 for the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0048] Figure 3j The equivalent circuit diagram of the switching mode 10 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0049] Figure 3k The equivalent circuit diagram of the switching mode 11 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0050] Figure 3l The equivalent circuit diagram of the switching mode 12 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0051] Figure 3m The equivalent circuit diagram of the switching mode 13 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0052] Figure 3n The equivalent circuit diagram of the switching mode 14 of the integrated three-port DC-DC converter for photovoltaic and energy storage integration.

[0053] Figure 4 Simulation waveform diagram of an integrated three-port DC-DC converter for photovoltaic and energy storage integration. Detailed Implementation

[0054] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0055] This invention relates to an integrated three-port DC-DC converter combining photovoltaic and energy storage. The integrated three-port DC-DC converter includes a photovoltaic power generation port, an energy storage port, and an output port. The photovoltaic power generation port is connected to the intermediate bus via a four-transistor Buck-Boost circuit for unidirectional energy input. The energy storage port is connected to the intermediate bus via another four-transistor Buck-Boost circuit for bidirectional energy flow. A full-bridge LLC resonant converter converts the intermediate bus voltage into the required output voltage and outputs energy to the load. By multiplexing the output arm switches of the two four-transistor Buck-Boost converters and the primary-side switches of the full-bridge LLC resonant converter, and using phase-shift modulation, the inductor current of the four-transistor Buck-Boost circuit is controlled into a quadrilateral inductor current, thereby reducing the number of components and achieving soft switching of all switches. The topology of this invention is applicable to integrated photovoltaic and energy storage DC power supply scenarios. It can achieve soft switching, electrical isolation, and wide-range voltage regulation of switching devices, and effectively reduce the number of devices, thereby achieving high power density, high conversion efficiency, and high reliability of the integrated photovoltaic and energy storage system. Specifically, the circuit structure of the integrated three-port DC-DC converter of this invention is as follows: Figure 1 As shown:

[0056] The three-port DC-DC converter topology includes: a photovoltaic power generation port unit, an energy storage port unit, and an output port unit.

[0057] Among them, photovoltaic power generation port V PV Through the corresponding four-transistor Buck-Boost converter (the first four-transistor Buck-Boost converter) and the DC bus capacitor C bus Parallel connection, including inductor L a Switching transistor Q A1 Q A2 Q A3 Q A4 and its anti-parallel diode D A1 D A2 D A3 D A4 junction capacitance C A1 C A2 C A3 C A4 Energy storage port V bat Through another corresponding four-transistor Buck-Boost converter (the second four-transistor Buck-Boost converter) and the DC bus capacitor C bus Parallel connection, including inductor L b Switching transistor Q B1 Q B2 Q B3 Q B4 and its anti-parallel diode D B1D B2 D B3 D B4 junction capacitance C B1 C B2 C B3 C B4 The output port unit consists of a full-bridge LLC resonant converter, including a resonant inductor L. r Magnetizing inductance L m Resonant capacitor C r Transformer T r Output filter capacitor C o 1 Rectifier diode D R1 D R2 D R3 D R4 and load R Ld (output port v) o ), whose original side bridge arms respectively reuse Q A3 and Q A4 Q B3 and Q B4 .

[0058] Define the switching transistor Q A1 and Q A2 Q B1 and Q B2 For non-reusable bridge arms, Q A3 and Q A4 Q B3 and Q B4 For reusing bridge arms. Reused bridge arm Q A3 Q A4 Q B3 Q B4 The duty cycle is fixed at 50%, and Q A3 and Q B4 Simultaneous on / off, Q A4 and Q B3 Simultaneous on / off switching.

[0059] like Figure 1 As shown, the positive terminal of the photovoltaic panel and Q A1 The drains are connected, Q A1 source and Q A2 The drain and L a One end is connected, L a The other end and Q A3 source and Q A4 The drains are connected, Q A3 The drain and C bus One end is connected, C bus The other end and Q A4 source and Q A2 The source electrode is connected to the negative terminal of the photovoltaic panel; the positive terminal of the energy storage battery is connected to Q.B1 The drains are connected, Q B1 source and Q B2 The drain and L b One end is connected, L b The other end and Q B3 source and Q B4 The drains are connected, Q B3 The drain and C bus One end is connected, C bus The other end and Q B4 source and Q B2 The source electrode is connected to the negative terminal of the energy storage battery; the multiplexed bridge arm Q A3 The source and Q A4 Drain and L r One end is connected, L r The other end and L m one end and T r Connect one end of the original edge, T r The other end of the original side is connected to L m The other end and C r One end is connected, C r The other end is connected to the reused bridge arm Q B3 The source and Q B4 The drains are connected; T r One end of the secondary side and D R1 anode and D R3 The cathode is connected, D R1 cathode and D R2 cathode and C o One end and load R Ld One end is connected, T r The other end of the secondary side and D R2 anode and D R4 The cathode is connected, D R3 anode and D R4 anode and C o The other end and R Ld The other end is connected.

[0060] The integrated photovoltaic-storage three-port DC-DC converter of this invention has four power transmission modes. Mode 1 provides energy to the output port from both the photovoltaic power generation port and the energy storage port; Mode 2 provides energy to both the energy storage port and the output port from the photovoltaic power generation port; Mode 3 provides energy to the output port solely from the photovoltaic power generation port; and Mode 4 provides energy to the output port solely from the energy storage port. In Mode 1, both four-transistor Buck-Boost converters operate in forward power transmission mode; in Mode 2, the four-transistor Buck-Boost converter corresponding to the photovoltaic power generation port operates in forward power transmission mode, and the four-transistor Buck-Boost converter corresponding to the energy storage port operates in reverse power transmission mode; in Mode 3, the four-transistor Buck-Boost converter corresponding to the energy storage port does not operate, and the four-transistor Buck-Boost converter corresponding to the photovoltaic power generation port operates in forward power transmission mode; in Mode 4, the four-transistor Buck-Boost converter corresponding to the photovoltaic power generation port does not operate, and the four-transistor Buck-Boost converter corresponding to the energy storage port operates in forward power transmission mode; in all four modes, the full-bridge LLC resonant converter operates in forward power transmission mode.

[0061] The modulation strategy of the integrated three-port DC-DC converter for photovoltaic and energy storage in this invention is phase-shift modulation. For the four-transistor Buck-Boost converter corresponding to the photovoltaic power generation port, Q A1 It should precede Q. A3 Off, Q A3 It should precede Q. A2 Off, Q A2 It should precede Q. A4 Off, Q A4 It should precede Q. A1 Turn off; switching transistor Q A1 Q A2 Complementary conduction, switching transistor Q A3 Q A4 The duty cycle is fixed at 50%, controlling the switching transistor Q. A1 Duty cycle D ya and switching transistor Q A1 With the switching transistor Q A4 Phase shift angle D at the activation time θa Make inductor L a The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching for all switching transistors. For the four-transistor Buck-Boost converter corresponding to the energy storage port, in the forward energy transfer mode, Q... B1 It should precede Q. B3 Off, Q B3 It should precede Q. B2 Off, Q B2 It should precede Q. B4 Off, Q B4 It should precede Q.B1 Off; in reverse energy transfer mode, Q B3 It should precede Q. B1 Off, Q B1 It should precede Q. B4 Off, Q B4 It should precede Q. B2 Off, Q B2 It should precede Q. B3 Turn off; switching transistor Q B1 Q B2 Complementary conduction, switching transistor Q B3 Q B4 The duty cycle is fixed at 50%, controlling the switching transistor Q. B1 Duty cycle D yb and switching transistor Q B1 With the switching transistor Q B4 Phase shift angle D at the activation time θb Make inductor L b The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching of all switching transistors.

[0062] The integrated three-port DC-DC converter for photovoltaic and energy storage described in this invention includes 14 switching modes. Figure 2 Figure 3 shows the operating waveforms of the integrated three-port DC-DC converter for photovoltaic and energy storage. The equivalent circuit diagrams of the integrated three-port DC-DC converter under different switching modes are shown in Figure 3. The 14 switching modes are as follows:

[0063] like Figure 3a As shown, switching mode 1 [t0, t1]: at time t0, Q is turned off. A1 L a Inductor current i La Give Q A1 C A1 Charging, while simultaneously supplying Q A2 C A2 Discharge; at time t1, C A1 The voltage is charged to V PV Meanwhile, C A2 If the voltage is set to zero, then Q A2 anti-parallel diode D A2 Natural conduction, at which point Q can be turned on with zero voltage. A2 Q B1 and Q B4 When the circuit is turned on, the current applied to inductor L is... b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Resonant operation, secondary rectifier diode D R1 and D R4Turning on clamps the primary voltage of the transformer to NV. o Energy is transferred from the primary side to the secondary side, L m excitation current i Lm The voltage increases linearly, where N is the number of turns on the primary and secondary sides of the transformer, and V... o This refers to the output voltage.

[0064] like Figure 3b As shown, switching mode 2 [t1,t2]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is -V bus V bus C bus Voltage applied, i La Linear decrease; Q B1 and Q B4 When the circuit is turned on, the current applied to inductor L is... b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Continue resonant operation;

[0065] like Figure 3c As shown, switching mode 3 [t2,t3]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is -V bus i La Linear decrease; Q B1 and Q B4 When the circuit is turned on, the current applied to inductor L is... b The voltage across the terminals is V bat i Lb The resonant current i increases linearly; at time t2, the resonant current i Lr Resonance with excitation current i Lm When the primary side is equal to the secondary side, energy is no longer transferred to the secondary side, and the current of the secondary rectifier diode naturally decreases to zero, achieving zero-current turn-off and eliminating the reverse recovery problem; thereafter, L m L r and C r The three components resonate, and the load is C. o powered by;

[0066] like Figure 3d As shown, switching mode 4 [t3,t4]: at time t3, Q is turned off. A3 i Lr Give Q A3 C A3 Charging, while simultaneously supplying Q A4 C A4 Discharge; at time t4, C A3The voltage is charged to V bus Meanwhile, C A4 If the voltage is set to zero, then Q A4 anti-parallel diode D A4 Natural conduction, at which point Q can be turned on with zero voltage. A4 Similarly, at time t3, Q is turned off. B4 It can turn on Q with zero voltage. B3 L m L r and C r The three components continue to resonate, with the load being C. o powered by;

[0067] like Figure 3e As shown, switching mode 5 [t4,t5]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bat -V bus (Assume V) bat >V bus ), i Lb Linear increase; L r and C r Resonant operation, secondary side D R2 and D R3 Turning on the transformer will convert the primary voltage V to voltage V. p Clamping to -NV o Energy is transferred from the primary side to the secondary side, and the excitation current i Lm Linear decrease;

[0068] like Figure 3f As shown, switching mode 6 [t5,t6]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keep it unchanged; at time t5, turn off Q. B2 i Lb Give Q B2 C B2 Charging, while simultaneously supplying Q B1 C B1 Discharge; at time t6, C B2 The voltage is charged to V bat Meanwhile, C B1 If the voltage is set to zero, then Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage.B1 L r and C r Continue resonant operation;

[0069] like Figure 3g As shown, switching mode 7 [t6,t7]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B2 and Q B3 When the circuit is turned on, the current applied to inductor L is... a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0070] like Figure 3h As shown, switching mode 8 [t7, t8]: at time t7, Q is turned off. A2 i La Give Q A2 C A2 Charging, while simultaneously supplying Q A1 C A1 Discharge; at time t8, C A2 The voltage is charged to V PV Meanwhile, C A1 If the voltage is set to zero, then Q A1 anti-parallel diode D A1 Natural conduction, at which point Q can be turned on with zero voltage. A1 Q B2 and Q B3 When the circuit is turned on, the current applied to inductor L is... a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0071] like Figure 3i As shown, switching mode 9 [t8,t9]: Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 When the circuit is turned on, the current applied to inductor L is... a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation;

[0072] like Figure 3j As shown, the switching mode 10[t9,t 10 Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 When the circuit is turned on, the current applied to inductor L is... a The voltage across the terminals is -V bus i Lb The linear decrease occurs; at time t9, the resonant current i Lr When the resonant current equals the excitation current, the current in the secondary rectifier diode naturally decreases to zero, achieving zero-current turn-off; thereafter, L m L r and C r The three components resonate, and the load is C. o powered by;

[0073] like Figure 3k As shown, switching mode 11[t 10 ,t 11 ]: In t 10 At any time, turn off Q. A4 i La Give Q A4 C A4 Charging, while simultaneously supplying Q A3 C A3 Discharge; at t 11 At that moment, C A4 The voltage is charged to V bus Meanwhile, C A3 If the voltage is set to zero, then Q A3 anti-parallel diode D A3 Natural conduction, at which point Q can be turned on with zero voltage. A3 Similarly, in t 10 At any time, turn off Q. B3 It can turn on Q with zero voltage. B4 L m L r and C r The three components continue to resonate, with the load being C. o powered by;

[0074] like Figure 3l As shown, switching mode 12[t] 11 ,t 12 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus(Assume V) PV >V bus ), i La linearly increasing; Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i Lb Remain unchanged; L r and C r Resonant operation, secondary rectifier diode D R1 and D R4 Turning on the transformer will convert the primary voltage V to voltage V. p Clamping to NV o Energy is transferred from the primary side to the secondary side, and the excitation current i Lm Linear increase;

[0075] like Figure 3m As shown, switching mode 13[t] 12 ,t 13 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La Linear increase; at t 12 At any time, turn off Q. B2 i Lb Give Q B2 junction capacitance C B2 Charging, while simultaneously supplying Q B1 C B1 Discharge; at t 13 At that moment, C B2 The voltage is charged to V bat Meanwhile, C B1 If the voltage is set to zero, then Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage. B1 L r and C r Continue resonant operation;

[0076] like Figure 3n As shown, switching mode 14[t 13 ,t 14 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La linearly increasing; Q B1 and Q B4 When the circuit is turned on, the current applied to inductor L is... b The voltage across the terminals is Vbat i Lb Linear increase; L r and C r Continue resonant operation.

[0077] The working principle and switching mode of the integrated three-port DC-DC converter of the photovoltaic-storage system of the present invention in modes two, three and four are similar to those in mode one, and will not be repeated here.

[0078] This invention connects an independent four-transistor Buck-Boost converter to both the photovoltaic power generation port and the energy storage port. The four-transistor Buck-Boost converter at the photovoltaic power generation port has only unidirectional buck-boost capability, while the four-transistor Buck-Boost converter at the energy storage port has bidirectional buck-boost capability. The output arm switches of each four-transistor Buck-Boost converter are multiplexed with the primary-side switches of the full-bridge LLC resonant converter, and power is then supplied to the load through an isolated LLC resonant converter. This structure satisfies the different energy flow requirements of unidirectional and bidirectional sources while avoiding energy interference between different ports. Arm multiplexing reduces the number of switches, increasing power density. A suitable modulation strategy enables soft switching of all switches. The soft-switching characteristics of the LLC resonant converter further enhance efficiency and power density by enabling soft switching of the secondary-side diodes. This converter effectively reduces the number of components and control complexity by reusing bridge arms while ensuring functional integrity. It can achieve full-range soft switching, high power density, high conversion efficiency, high reliability, electrical isolation, wide-range voltage regulation, and flexible multi-source management, making it suitable for DC power supply scenarios that integrate photovoltaic and energy storage.

[0079] To further illustrate the superiority of the circuit topology of this invention, a simulation example of this invention is given below.

[0080] Based on the main parameters of the 5000W integrated three-port DC-DC converter with photovoltaic and energy storage given in Table 1, a simulation circuit was built using Saber simulation software.

[0081] Table 1. Main parameters of the integrated three-port DC-DC converter for photovoltaic and energy storage:

[0082] Figure 4 Simulation waveforms of a 500W integrated three-port DC-DC converter combining photovoltaic and energy storage are presented. Figure 4 It can be seen that during the switching cycle, L a Inductor current i La Modulated into a quadrilateral shape, it enables ZVS (zero-voltage turn-on) of the switching transistor; L b Inductor current i LbModulated into a quadrilateral shape, it enables the switch to achieve ZVS (zero voltage turn-on); the secondary rectifier diode also achieves ZCS (zero current turn-off).

[0083] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An integrated three-port DC-DC converter combining photovoltaic and energy storage, characterized in that, The integrated photovoltaic and energy storage three-port DC-DC converter includes, in sequence, a photovoltaic power generation port unit, an energy storage port unit, and an output port unit; The photovoltaic power generation port unit includes a photovoltaic power generation port and a first four-transistor Buck-Boost converter. The photovoltaic power generation port is connected to the DC bus capacitor C through the first four-transistor Buck-Boost converter. bus Parallel connection is used to achieve unidirectional energy input; The energy storage port unit includes an energy storage port and a second four-transistor Buck-Boost converter. The energy storage port is connected to the DC bus capacitor C through the second four-transistor Buck-Boost converter. bus Parallel connection is used to achieve bidirectional energy flow; The output port unit includes a full-bridge LLC resonant converter, which is used to convert the DC bus voltage into the required output voltage and output energy to the load. The output bridge arm switches of the first four-transistor Buck-Boost converter and the second four-transistor Buck-Boost converter are multiplexed with the primary-side switches of the full-bridge LLC resonant converter. A phase-shift modulation strategy is used to control the inductor current of the first four-transistor Buck-Boost converter and the second four-transistor Buck-Boost converter to achieve soft switching of all switches.

2. The integrated three-port DC-DC converter combining photovoltaic and energy storage according to claim 1, characterized in that, The first four-transistor Buck-Boost converter includes an inductor L a Switching transistor Q A1 Q A2 Q A3 Q A4 and its anti-parallel diode D A1 D A2 D A3 D A4 junction capacitance C A1 C A2 C A3 C A4 The positive terminal of the photovoltaic power generation port and Q A1 The drains are connected, Q A1 source and Q A2 The drain and L a One end is connected, L a The other end and Q A3 source and Q A4 The drains are connected, Q A3 The drain and C bus One end is connected, C bus The other end and Q A4 source and Q A2 The source electrode is connected to the negative terminal of the photovoltaic power generation port.

3. The integrated three-port DC-DC converter combining optical and energy storage according to claim 2, characterized in that, The second four-transistor Buck-Boost converter includes an inductor L b Switching transistor Q B1 Q B2 Q B3 Q B4 and its anti-parallel diode D B1 D B2 D B3 D B4 junction capacitance C B1 C B2 C B3 C B4 The positive terminal of the energy storage port is connected to Q. B1 The drains are connected, Q B1 source and Q B2 The drain and L b One end is connected, L b The other end and Q B3 source and Q B4 The drains are connected, Q B3 The drain and C bus One end is connected, C bus The other end and Q B4 source and Q B2 The source electrode is connected to the negative terminal of the energy storage port.

4. The integrated three-port DC-DC converter combining optical and energy storage according to claim 3, characterized in that, The full-bridge LLC resonant converter includes a resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r Output filter capacitor C o 1 Rectifier diode D R1 D R2 D R3 D R4 and load R Ld Its original side bridge arm reuses Q A3 and Q A4 Q B3 and Q B4 R Ld Both ends are output ports; among them, the switching transistor Q A1 and Q A2 Q B1 and Q B2 For non-reusable bridge arms, Q A3 and Q A4 Q B3 and Q B4 For reused bridge arm; reused bridge arm Q A3 Q A4 Q B3 Q B4 The duty cycle is fixed at 50%, and Q A3 and Q B4 Simultaneous on / off, Q A4 and Q B3 Simultaneous on / off; the Q A3 The source and Q A4 The drain and L r One end is connected, L r The other end and L m one end and T r Connect one end of the original edge, T r The other end of the original side is connected to L m The other end and C r One end is connected, C r The other end and Q B3 The source and Q B4 The drains are connected; T r One end of the secondary side is connected to D R1 anode and D R3 The cathode is connected, D R1 cathode and D R2 Cathode and C o one end and R Ld One end is connected, T r The other end of the secondary side is connected to D R2 anode and D R4 The cathodes are connected, D R3 anode and D R4 anode and C o The other end and R Ld The other end is connected.

5. An integrated three-port DC-DC converter combining optical and energy storage according to any one of claims 1-4, characterized in that, The integrated photovoltaic-storage three-port DC-DC converter has four power transmission modes: Mode 1, where the photovoltaic power generation port and the energy storage port supply energy to the output port; Mode 2, where the photovoltaic power generation port supplies energy to both the energy storage port and the output port; Mode 3, where the photovoltaic power generation port supplies energy to the output port alone; and Mode 4, where the energy storage port supplies energy to the output port alone. In Mode 1, both the first and second four-transistor Buck-Boost converters operate in forward power transmission mode. In Mode 2, the first four-transistor Buck-Boost converter operates in forward power transmission mode, and the second four-transistor Buck-Boost converter operates in reverse power transmission mode. In Mode 3, the second four-transistor Buck-Boost converter does not operate, and the first four-transistor Buck-Boost converter operates in forward power transmission mode. In Mode 4, the first four-transistor Buck-Boost converter does not operate, and the second four-transistor Buck-Boost converter operates in forward power transmission mode. In all four modes, the full-bridge LLC resonant converter operates in forward power transmission mode.

6. The integrated three-port DC-DC converter combining optical and energy storage according to claim 5, characterized in that, Mode 1 includes 14 switching modes, namely: Switching mode 1, corresponding to time [t0, t1]: at time t0, Q is turned off. A1 L a Inductor current i La Give Q A1 C A1 Charging, while simultaneously supplying Q A2 C A2 Discharge; at time t1, C A1 The voltage is charged to V PV Meanwhile, C A2 The voltage is set to zero, Q A2 anti-parallel diode D A2 Natural conduction, at which point Q can be turned on with zero voltage. A2 Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is the energy storage port voltage V. bat i Lb Linear increase; L r and C r Resonant operation, D R1 and D R4 Turn on, and turn on transformer T r Primary voltage clamped to NV o Transformer T r Energy is transferred from the primary edge to the secondary edge, L m excitation current i Lm The linear increase, where N is the transformer T r The turn edge of the primary and secondary sides, V o The output voltage of the output port; Switching mode 2, corresponding to time [t1, t2]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is -V bus V bus C bus Voltage applied, i La Linear decrease; Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Continue resonant operation; Switching mode 3, corresponding to time [t2, t3]: Q A2 and Q A3 Simultaneously activated, applied to L a The voltage across the terminals is -V bus i La Linear decrease; Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is V bat i Lb The resonant current i increases linearly; at time t2, the resonant current i Lr Resonance with excitation current i Lm Equal, T r The primary side no longer transfers energy to the secondary side, and the current in the secondary rectifier diode naturally decreases to zero, achieving zero-current turn-off; thereafter, L m L r and C r The three elements resonate and work together, R Ld By C o powered by; Switching mode 4, corresponding to times [t3, t4]: at time t3, Q is turned off. A3 i Lr Give Q A3 C A3 Charging, while simultaneously supplying Q A4 C A4 Discharge; at time t4, C A3 The voltage is charged to V bus Meanwhile, C A4 The voltage is set to zero, Q A4 anti-parallel diode D A4 Natural conduction, at which point Q can be turned on with zero voltage. A4 Similarly, at time t3, Q is turned off. B4 It can turn on Q with zero voltage. B3 L m L r and C r The three continue to resonate, R Ld By C o powered by; Switching mode 5, corresponding to time [t4, t5]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bat -V bus V bat >V bus i Lb Linear increase; L r and C r Resonant operation, T r secondary side D R2 and D R3 Conducting, will T r Primary voltage v p Clamping to -NV o T r Energy is transferred from the primary side to the secondary side, and the excitation current i Lm Linear decrease; Switching mode 6, corresponding to time [t5, t6]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keep it unchanged; at time t5, turn off Q. B2 i Lb Give Q B2 C B2 Charging, while simultaneously supplying Q B1 C B1 Discharge; at time t6, C B2 The voltage is charged to V bat Meanwhile, C B1 The voltage is set to zero, Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage. B1 L r and C r Continue resonant operation; Switching mode 7, corresponding to time [t6, t7]: Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Keeps unchanged; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation; Switching mode 8, corresponding to time [t7, t8]: at time t7, Q is turned off. A2 i La Give Q A2 C A2 Charging, while simultaneously supplying Q A1 C A1 Discharge; at time t8, C A2 The voltage is charged to V PV Meanwhile, C A1 The voltage is set to zero, Q A1 anti-parallel diode D A1 Natural conduction, at which point Q can be turned on with zero voltage. A1 Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation; Switching mode 9, corresponding to time [t8, t9]: Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; L r and C r Continue resonant operation; Switching mode 10, corresponding to time [t9, t 10 Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V PV i La linearly increasing; Q B2 and Q B3 Conduction, applied to L a The voltage across the terminals is -V bus i Lb Linear decrease; at time t9, i Lr Resonance with i Lm Equal, T r The current in the secondary-side rectifier diode naturally decreases to zero, achieving zero-current turn-off; thereafter, L m L r and C r The three elements resonate and work together, R Ld By C o powered by; Switching mode 11, corresponding to time [t] 10 ,t 11 ]: In t 10 At any time, turn off Q. A4 i La Give Q A4 C A4 Charging, while simultaneously supplying Q A3 C A3 Discharge; at t 11 At that moment, C A4 The voltage is charged to V bus Meanwhile, C A3 If the voltage is set to zero, then Q A3 anti-parallel diode D A3 Natural conduction, at which point Q can be turned on with zero voltage. A3 Similarly, in t 10 At any time, turn off Q. B3 It can turn on Q with zero voltage. B4 L m L r and C r The three continue to resonate, R Ld By C o powered by; Switching mode 12, corresponding to time [t] 11 ,t 12 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus V PV >V bus i La linearly increasing; Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i Lb Remain unchanged; L r and C r Resonant operation, T r secondary side D R1 and D R4 Conducting, will T r Primary voltage v p Clamping to NV o T r Energy is transferred from the primary edge to the secondary edge, i Lm Linear increase; Switching mode 13, corresponding to time [t] 12 ,t 13 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La Linear increase; at t 12 At any time, turn off Q. B2 i Lb Give Q B2 C B2 Charging, while simultaneously supplying Q B1 C B1 Discharge; at t 13 At that moment, C B2 The voltage is charged to V bat Meanwhile, C B1 If the voltage is set to zero, then Q B1 anti-parallel diode D B1 Natural conduction, at which point Q can be turned on with zero voltage. B1 L r and C r Continue resonant operation; Switching mode 14, corresponding to time [t] 13 ,t 14 Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V PV -V bus i La linearly increasing; Q B1 and Q B4 Conduction, applied to L b The voltage across the terminals is V bat i Lb Linear increase; L r and C r Continue resonant operation.

7. The integrated three-port DC-DC converter combining optical and energy storage according to claim 4, characterized in that, The phase-shifting modulation strategy includes: for the first four-transistor Buck-Boost converter, Q... A1 Before Q A3 Off, Q A3 Before Q A2 Off, Q A2 Before Q A4 Off, Q A4 Before Q A1 Off; Q A1 Q A2 Complementary conduction, Q A3 Q A4 The duty cycle is fixed at 50%, controlling Q. A1 Duty cycle D ya and Q A1 With Q A4 Phase shift angle D at the activation time θa , making L a The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching of all switching transistors.

8. The integrated three-port DC-DC converter combining optical and energy storage according to claim 4, characterized in that, The phase-shifting modulation strategy includes: for the second four-transistor Buck-Boost converter, in the forward power transfer mode, Q... B1 Before Q B3 Off, Q B3 Before Q B2 Off, Q B2 Before Q B4 Off, Q B4 Before Q B1 Off; in reverse energy transfer mode, Q B3 Before Q B1 Off, Q B1 Before Q B4 Off, Q B4 Before Q B2 Off, Q B2 Before Q B3 Off; Q B1 Q B2 Complementary conduction, Q B3 Q B4 The duty cycle is fixed at 50%, controlling Q. B1 Duty cycle D yb and Q B1 With Q B4 Phase shift angle D at the activation time θb , making L b The inductor current is controlled into a quadrilateral inductor current, thereby achieving soft switching of all switching transistors.

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