Partial power transmission type three-port DC / DC converter suitable for optical-storage-load system

Abstract

The invention provides a partial power transmission type three-port DC / DC converter suitable for a light-storage-load system, and belongs to the technical field of power electronics. The converter integrates a photovoltaic port, an energy storage port and a load port and is composed of a half-bridge unit, an inductor, a capacitor and a voltage balancing unit, and the voltage balancing unit can adopt an isolated voltage balancer or a non-isolated voltage balancer. According to the invention, efficient collaborative management of multi-source energy can be realized; on the basis of the partial power transmission principle, the voltage stress and the transmission power of the half-bridge unit HB1 and the half-bridge unit HB2 are reduced, the operation efficiency and the power density of the system can be improved by adopting a low-voltage power device with better performance, and a key technical support is provided for efficient utilization of renewable energy sources in a novel power system.

Description

Technical Field

[0001] This invention relates to a partial power transfer type three-port DC / DC converter suitable for photovoltaic-storage-load systems, belonging to the field of power electronics technology. Background Technology

[0002] To support the global green energy transition and development goals, alleviate grid stability pressures, and improve the synergistic utilization efficiency of photovoltaic (PV) power generation and energy storage systems, new energy power generation systems centered on "PV + energy storage" are gradually evolving from supplementary power sources to a crucial supporting force in the power system. In recent years, with the continuous expansion of PV installations and rapid breakthroughs in energy storage technology, PV + energy storage systems are accelerating their development towards large-scale and integrated applications. Integration schemes using three-port power conversion circuits can significantly reduce system losses and improve dynamic response performance, and will become the mainstream technical path for scenarios with high proportions of new energy integration.

[0003] For the application scenario of "photovoltaic-storage-load" systems, the invention patent with patent application number CN201910699497.3 discloses a three-port Boost integrated converter and control method for photovoltaic energy storage systems. It innovatively proposes a single-switch integrated scheme, which reduces the system size by 30% and improves efficiency by 5-8% by having inductor L1 operate in DCM mode and L2 operate in CCM mode, combined with a PWM+PFM hybrid modulation strategy. However, this scheme has significant current ripple due to inductor L1 operating in DCM mode, and the single-switch scheme has serious control coupling problems, which cannot meet the multi-power flow requirements of "photovoltaic-storage-load" systems.

[0004] The invention patent with patent application number CN201910868828.1 discloses a three-port DC-DC converter with high-efficiency energy transmission and its control method. It proposes a phase-shifted full-bridge dynamic compensation architecture, which, through a photovoltaic-bus series design, enables the phase-shifted full-bridge to bear only about 20% of the compensation power, significantly improving the system operating efficiency. However, this scheme introduces additional power devices, inductors, and high-frequency transformers, which is not conducive to improving the system power density. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and to provide a partial power transmission type three-port DC / DC converter suitable for optical-storage-load systems.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A partial power transfer type three-port DC / DC converter suitable for photovoltaic-storage-load systems includes: photovoltaic and energy storage units, a load port, and a capacitor. ,capacitance And a voltage balancing unit; the voltage balancing unit includes port 1 and port 2, each of which includes a positive terminal and a negative terminal;

[0008] The first terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal, the negative terminal of port 2 of the voltage balancing unit, and the negative terminal of the load port; the second terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal and the negative terminal of port 1 of the voltage balancing unit; the third terminal of the photovoltaic and energy storage units are respectively connected to capacitors. Positive terminal, positive terminal of port 1 of the voltage balancing unit, positive terminal of port 2 of the voltage balancing unit, capacitor The positive terminal and the positive terminal of the load port.

[0009] Preferably, the voltage balancing unit employs an isolated DC / DC converter, which is a dual active bridge converter, a single active bridge converter, a series resonant converter, an LLC resonant converter, or a CLLC resonant converter.

[0010] Preferably, the photovoltaic and energy storage unit includes: a photovoltaic port, an energy storage port, and a half-bridge unit. , and inductors , ;

[0011] The output terminal of the half-bridge unit HB1 is connected to the inductor The negative terminal of the inductor is connected; The positive terminal of the inductor is connected to the positive terminal of the photovoltaic port; the output terminal of the half-bridge unit HB2 is connected to the inductor. The negative terminal of the inductor is connected; The positive terminal is connected to the positive terminal of the energy storage port;

[0012] The negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port, and the connection point serves as the first end of the photovoltaic and energy storage unit; the half-bridge unit Negative extreme and half-bridge unit The negative terminal is connected, and the connection point serves as the second end of the photovoltaic and energy storage unit; the half-bridge unit Positive end and half-bridge unit The positive end is connected, and the connection point serves as the third end of the photovoltaic and energy storage unit.

[0013] Preferably, the half-bridge unit , The switching devices are one or two of the following: field-effect transistors (MOSFETs), SiC MOSFETs, insulated-gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

[0014] A partial power transfer type three-port DC / DC converter suitable for photovoltaic-storage-load systems includes: photovoltaic and energy storage units, a load port, and a capacitor. ,capacitance And a voltage balancing unit; the voltage balancing unit includes a positive terminal, a negative terminal and an output terminal;

[0015] The first terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal, the negative terminal of the load port, and the negative terminal of the voltage balancing unit; the second terminals of the photovoltaic and energy storage units are respectively connected to capacitors. Negative terminal, capacitor The positive terminal and the output terminal of the voltage balancing unit; the third terminal of the photovoltaic and energy storage units are respectively connected to capacitors. Positive terminal, positive terminal of voltage balancing unit, and positive terminal of load port.

[0016] Preferably, the voltage balancing unit adopts a non-isolated voltage balancer, which is a Buck-Boost converter, a dual Buck converter, a Cuk converter, a Sepic converter, or a Zeta converter.

[0017] Preferably, the photovoltaic and energy storage unit includes: a photovoltaic port, an energy storage port, and a half-bridge unit. , and inductors , ;

[0018] The half-bridge unit Output terminal and inductor The negative terminal of the inductor is connected; The positive terminal of the half-bridge unit is connected to the positive terminal of the photovoltaic port. Output terminal and inductor The negative terminal of the inductor is connected; The positive terminal is connected to the positive terminal of the energy storage port;

[0019] The negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port, and the connection point serves as the first end of the photovoltaic and energy storage unit; the half-bridge unit Negative extreme and half-bridge unit The negative terminal is connected, and the connection point serves as the second end of the photovoltaic and energy storage unit; the half-bridge unit Positive end and half-bridge unit The positive end is connected, and the connection point serves as the third end of the photovoltaic and energy storage unit.

[0020] Preferably, the half-bridge unit , The switching devices are one or two of the following: field-effect transistors (MOSFETs), SiC MOSFETs, insulated-gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention combines a half-bridge unit with a voltage balancing unit, and based on the principle of partial power transfer, reduces the cost of the half-bridge unit. and half-bridge unit By employing high-performance low-voltage power devices, the voltage stress and transmission power of the system can be reduced, thereby improving system operating efficiency and power density, providing key technical support for the efficient utilization of renewable energy in new power systems.

[0023] The partial power transfer type three-port DC / DC converter of the present invention, applicable to photovoltaic-storage-load systems, can provide energy to the load simultaneously through photovoltaic and energy storage ports, provide energy to the energy storage port through the photovoltaic port, or provide energy to the load port through only the energy storage port. It can flexibly operate in different modes with lower overall voltage capability and meet the multi-power flow requirements of photovoltaic-storage-load systems.

[0024] The present invention relates to a partial power transmission type three-port DC / DC converter applicable to a photovoltaic-storage-load system. The voltage balancing unit can be an isolated voltage balancer or a non-isolated voltage balancer. Its advantage is that it can reduce current stress. Using an isolated voltage balancer can further improve efficiency through the design of soft-switching operation. Attached Figure Description

[0025] Figure 1 This is a topology diagram of a partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to Embodiment 1 of the present invention.

[0026] Figure 2 This is a topology diagram of a partial power transfer type three-port DC / DC converter suitable for a light-storage-charge system according to Embodiment 2 of the present invention.

[0027] Figure 3 This is a schematic diagram of the main simulation results of a partial power transfer type three-port DC / DC converter applicable to an optical-storage-charge system according to Embodiment 2 of the present invention; wherein:

[0028] Figure 3 (a) is the output voltage of the photovoltaic port. Simulation results diagram;

[0029] Figure 3 (b) is the output current of the photovoltaic port. Simulation results diagram;

[0030] Figure 3 (c) is the output voltage of the energy storage port. Simulation results diagram;

[0031] Figure 3 (d) is the output current of the energy storage port. Simulation results diagram;

[0032] Figure 3 (e) is the capacitor on the voltage balancing unit. voltage Simulation results diagram;

[0033] Figure 3 (f) is the capacitor under the voltage balancing unit. voltage Simulation results diagram;

[0034] Figure 3 (g) represents the total voltage of the voltage balancing unit, i.e., the voltage at the load port. Simulation results diagram;

[0035] Figure 3 (h) represents the output current at the load port. A schematic diagram of the simulation results. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented based on the technical solution of the present invention and provides detailed implementation methods, but the protection scope of the present invention is not limited to the following embodiments.

[0037] Example 1:

[0038] like Figure 1 As shown, the first type of partial power transfer three-port DC / DC converter suitable for photovoltaic-storage-load systems of the present invention comprises a photovoltaic port, an energy storage port, a load port, half-bridge units HB1 and HB2, and an inductor. , ,capacitance , It consists of a voltage balancing unit.

[0039] The photovoltaic port, energy storage port, and load port each include a positive terminal and a negative terminal; the half-bridge units HB1 and HB2 each include a positive terminal, a negative terminal, and an output terminal; the inductor , Each capacitor contains one positive terminal and one negative terminal; , Each includes a positive terminal and a negative terminal; the voltage balancing unit includes port 1 and port 2, each of which includes a positive terminal and a negative terminal.

[0040] The switching devices of the half-bridge units HB1 and HB2 can be field-effect transistors (MOSFETs), SiC MOSFETs, insulated gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

[0041] The voltage balancing unit can employ isolated DC / DC converters, including dual active bridge (DAB) converters, single active bridge (SAB) converters, series resonant (SRC) converters, LLC resonant converters, CLLC resonant converters, etc.

[0042] The output terminal of the half-bridge unit HB1 is connected to the inductor The negative terminal of the inductor is connected; The positive terminal of the inductor is connected to the positive terminal of the photovoltaic port; the output terminal of the half-bridge unit HB2 is connected to the inductor. The negative terminal of the inductor is connected; The positive terminal of the photovoltaic port is connected to the positive terminal of the energy storage port; the negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port and to the capacitor. The negative terminal of the capacitor is connected to the negative terminal of the voltage balancing unit, the negative terminal of port 2, and the negative terminal of the load port; the negative terminal of the half-bridge unit HB1 is connected to the negative terminal of the half-bridge unit HB2, and is connected to the capacitor. The negative terminal of the capacitor is connected to the negative terminal of port 1 of the voltage balancing unit; the positive terminal of the half-bridge unit HB1 is connected to the positive terminal of the half-bridge unit HB2, and is connected to the capacitor. The positive terminal of the voltage balancing unit, the positive terminal of port 1 of the voltage balancing unit, the positive terminal of port 2 of the voltage balancing unit, and the capacitor. The positive terminal of the load port is connected to the positive terminal of the load port.

[0043] The circuit is maintained by a voltage balancing unit. and The voltage ratio across the two ends remains essentially constant; the duty cycle of the half-bridge unit HB1 is adjusted through closed-loop control to allow the inductor to pass through. The current remains stable; the duty cycle of the half-bridge unit HB2 is adjusted through closed-loop control to make the current stable. The voltage across the terminals remains stable. Based on the ampere-second balance formula, the following formula is derived:

[0044]

[0045] in, This is the voltage at the energy storage terminal. For capacitor Voltage at both ends, For capacitor The voltage across the terminals, where D is the duty cycle.

[0046] Example 2:

[0047] like Figure 2 As shown, the second type of partial power transfer three-port DC / DC converter suitable for photovoltaic-storage-load systems described in this invention comprises a photovoltaic port, an energy storage port, a load port, half-bridge units HB1 and HB2, and an inductor. , ,capacitance , It consists of a voltage balancing unit.

[0048] The photovoltaic port, energy storage port, and load port each include a positive terminal and a negative terminal; the half-bridge units HB1 and HB2 each include a positive terminal, a negative terminal, and an output terminal; the inductor , Each capacitor contains one positive terminal and one negative terminal; , Each includes a positive terminal and a negative terminal; the voltage balancing unit includes a positive terminal, a negative terminal and an output terminal.

[0049] The switching devices of the half-bridge units HB1 and HB2 can be field-effect transistors (MOSFETs), SiC MOSFETs, insulated gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

[0050] The voltage balancing unit can be a non-isolated voltage balancer, including Buck-Boost converters, dual Buck converters, Cuk converters, Sepic converters, Zeta converters, etc.

[0051] The output terminal of the half-bridge unit HB1 is connected to the inductor The negative terminal of the inductor is connected; The positive terminal of the inductor is connected to the positive terminal of the photovoltaic port; the output terminal of the half-bridge unit HB2 is connected to the inductor. The negative terminal of the inductor is connected; The positive terminal of the photovoltaic port is connected to the positive terminal of the energy storage port; the negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port and to the capacitor. The negative terminal of the capacitor is connected to the negative terminal of the voltage balancing unit and the negative terminal of the load port; the negative terminal of the half-bridge unit HB1 is connected to the negative terminal of the half-bridge unit HB2, and is connected to the capacitor. negative terminal, capacitor The positive terminal of the capacitor is connected to the output terminal of the voltage balancing unit; the positive terminal of the half-bridge unit HB1 is connected to the positive terminal of the half-bridge unit HB2, and is connected to the capacitor. The positive terminal of the voltage balancing unit is connected to the positive terminal of the load port.

[0052] The circuit is maintained by a voltage balancing unit. and The voltage ratio across the two ends remains essentially constant; the duty cycle of the half-bridge unit HB1 is adjusted through closed-loop control to allow the inductor to pass through. The current remains stable; the duty cycle of the half-bridge unit HB2 is adjusted through closed-loop control to make the current stable. The voltage across the terminals remains essentially stable. Based on the ampere-second balance formula, the following formula is derived:

[0053]

[0054] in, This is the voltage at the energy storage terminal. For capacitor Voltage at both ends, For capacitor The voltage across the terminals, where D is the duty cycle.

[0055] The operation of the two partial power transfer type three-port DC / DC converters of Embodiment 1 and Embodiment 2 of the present invention, applicable to optical-storage-load systems, in discharge mode, charging mode, and overload mode is as follows:

[0056] In discharge mode, when the DC voltage at the photovoltaic port and the DC voltage at the energy storage port change within a certain range, the duty cycle of the half-bridge unit HB1, the half-bridge unit HB2 and the voltage balance unit are adjusted through closed-loop control to keep the load port voltage constant and realize power distribution between the photovoltaic port and the energy storage port.

[0057] In charging mode, when the DC voltage of the photovoltaic port and the DC voltage of the energy storage port change within a certain range, the duty cycle of half-bridge unit HB1 and half-bridge unit HB2 is adjusted through closed-loop control, so that the energy storage port absorbs power to charge the photovoltaic port.

[0058] In overload mode, when the DC voltage of the energy storage port changes within a certain range, closed-loop control is used to make the photovoltaic port power 0 and the energy storage port output all overload power.

[0059] Example 3:

[0060] The partial power transfer three-port DC / DC converter for photovoltaic-storage-load systems described in Example 2 was used, operating in three modes: discharge, charge, and overload. The photovoltaic DC voltage varied between 300V and 600V, with a rated input power of 1kW; the energy storage DC voltage varied between 400V and 600V, with a rated input power of 500W; and the load port had a rated voltage of 620V and a rated output power of 1.5kW. The main simulation results of the partial power transfer three-port DC / DC converter for photovoltaic-storage-load systems described in this invention are as follows: Figure 3 As shown; where the time before 0.04s is working mode one, 0.04s-0.08s is working mode two, and after 0.08s it switches to working mode three. For Figure 3 (a) indicates that the output voltage of the photovoltaic port is always 450V; for Figure 3 (b) indicates that the photovoltaic port can output a controllable current of 2.22A in mode one, 1.11A in mode two, and 0A in mode three; for Figure 3 (c) indicates that the output voltage of the energy storage port is always 500V; for Figure 3 (d) indicates that the output current of the energy storage port is controllable at 1A in operating mode one, 1A in input in operating mode two, and 3A in output in operating mode three; for Figure 3 (e) indicates the capacitor on the voltage balancer in the three modes. The voltage can be controlled at 340V; for Figure 3 (f) represents the capacitance on the voltage balancer in the three modes. The voltage can be controlled at 280V; for Figure 3 (g) indicates that the total voltage of the voltage balancer can be controlled at 620V in all three modes; for Figure 3 (h) indicates that the output current can be controlled at a constant 2.5A in operating mode 1 and operating mode 3, and can be controlled at 0A in operating mode 2.

[0061] Operating Mode 1: Discharge Mode. In this mode, the rated voltage at the photovoltaic port is 450V, the rated voltage at the energy storage port is 500V, the rated output power at the load port is 1.5kW, and the voltage remains stable at 620V. During this stage, the capacitor... and capacitor The sum of the voltages across the terminals remains stable at 620V. At this time, the duty cycle of HB2 is 64.706%, and the current... The current flows out from the positive terminal of the energy storage port and remains stable at 1.0A; the duty cycle of the voltage balancing unit is 54.839%, and under the control of the voltage balancing unit, the voltage and capacitance at the load port are balanced. The voltage ratio across the capacitor remains constant. The voltage across the capacitor remains stable at 340V. The voltage across the terminals remains stable at 280V; the current... The current flows out from the positive terminal of the photovoltaic port and is maintained at a stable 2.22A under the control of the half-bridge unit HB1. The duty cycle of HB1 is 50%, and the circuit can maintain stable operation.

[0062] Operating Mode 2: Charging Mode. In this mode, the photovoltaic port input power is 500W, the voltage across it is 450V, the energy storage port output power is 500W, and the load port output power is 0W. During this stage, the capacitor... and capacitor The sum of the voltages across the terminals remains stable at 620V. At this time, the duty cycle of HB2 is 64.706%, and the current... The current flows in from the positive terminal of the energy storage port and remains stable at 1.0A; the duty cycle of the voltage balancing unit is 54.839%, and under the control of the voltage balancing unit, the voltage and capacitance at the load port are balanced. The voltage ratio across the capacitor remains constant. The voltage across the capacitor remains stable at 340V. The voltage across the terminals remains stable at 280V; the current... The current flows out from the positive terminal of the photovoltaic port and is maintained at a stable 1.11A by the control of the half-bridge unit HB1. HB1 has a duty cycle of 50% to charge the energy storage battery.

[0063] Operating Mode 3: Overload Mode. In this mode, the photovoltaic port power will be 0, the energy storage port input overload power will be 1.5kW, the voltage across it will be 500V, and the load port output will be 1.5kW. During this stage, the capacitor... and capacitor The sum of the voltages across the terminals remains stable at 620V. At this time, the duty cycle of HB2 is 64.706%, and the current... The current flows out from the positive terminal of the energy storage port and remains stable at 3.0A; the duty cycle of the voltage balancing unit is 54.839%, and under the control of the voltage balancing unit, the voltage and capacitance at the load port are balanced. The voltage ratio across the capacitor remains constant. The voltage across the capacitor remains stable at 340V. The voltage across the terminals remains stable at 280V; the current... Controlled by the half-bridge unit HB1, the circuit maintains a stable current of 0A. With a duty cycle of 50%, the circuit can operate stably.

[0064] The embodiment describes three operating modes of a partial power transfer type three-port DC / DC converter applicable to a "photovoltaic-storage-load" system. In discharge mode, when the DC voltage of the photovoltaic port and the DC voltage of the energy storage port vary within a certain range, closed-loop control is used to adjust the duty cycles of half-bridge units HB1, HB2, and the voltage balancing unit to keep the load port voltage constant and achieve power distribution between the photovoltaic port and the energy storage port. In charging mode, when the DC voltage of the photovoltaic port and the DC voltage of the energy storage port vary within a certain range, closed-loop control is used to adjust the duty cycles of half-bridge units HB1 and HB2 to allow the energy storage port to absorb power and charge the photovoltaic port. In overload mode, when the DC voltage of the energy storage port varies within a certain range, closed-loop control is used to make the photovoltaic port power 0 and the energy storage port output all overload power.

[0065] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems, characterized in that, include: Photovoltaic and energy storage units, load ports, capacitors ,capacitance And a voltage balancing unit; the voltage balancing unit includes port 1 and port 2, each of which includes a positive terminal and a negative terminal; The first terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal, the negative terminal of port 2 of the voltage balancing unit, and the negative terminal of the load port; the second terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal and the negative terminal of port 1 of the voltage balancing unit; the third terminal of the photovoltaic and energy storage units are respectively connected to capacitors. Positive terminal, positive terminal of port 1 of the voltage balancing unit, positive terminal of port 2 of the voltage balancing unit, capacitor The positive terminal and the positive terminal of the load port.

2. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 1, characterized in that, The voltage balancing unit employs an isolated DC / DC converter, which can be a dual active bridge converter, a single active bridge converter, a series resonant converter, an LLC resonant converter, or a CLLC resonant converter.

3. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 1, characterized in that, The photovoltaic and energy storage unit includes: a photovoltaic port, an energy storage port, and a half-bridge unit. , and inductors , ; The output terminal of the half-bridge unit HB1 is connected to the inductor The negative terminal of the inductor is connected; The positive terminal of the inductor is connected to the positive terminal of the photovoltaic port; the output terminal of the half-bridge unit HB2 is connected to the inductor. The negative terminal of the inductor is connected; The positive terminal is connected to the positive terminal of the energy storage port; The negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port, and the connection point serves as the first end of the photovoltaic and energy storage unit; the half-bridge unit Negative extreme and half-bridge unit The negative terminal is connected, and the connection point serves as the second end of the photovoltaic and energy storage unit; the half-bridge unit Positive end and half-bridge unit The positive end is connected, and the connection point serves as the third end of the photovoltaic and energy storage unit.

4. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 3, characterized in that, The half-bridge unit , The switching devices are one or two of the following: field-effect transistors (MOSFETs), SiC MOSFETs, insulated-gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

5. A partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems, characterized in that, include: Photovoltaic and energy storage units, load ports, capacitors ,capacitance And a voltage balancing unit; the voltage balancing unit includes a positive terminal, a negative terminal and an output terminal; The first terminals of the photovoltaic and energy storage units are respectively connected to capacitors. The negative terminal, the negative terminal of the load port, and the negative terminal of the voltage balancing unit; the second terminals of the photovoltaic and energy storage units are respectively connected to capacitors. Negative terminal, capacitor The positive terminal and the output terminal of the voltage balancing unit; the third terminal of the photovoltaic and energy storage units are respectively connected to capacitors. Positive terminal, positive terminal of voltage balancing unit, and positive terminal of load port.

6. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 5, characterized in that, The voltage balancing unit adopts a non-isolated voltage balancer, which is a Buck-Boost converter, a dual Buck converter, a Cuk converter, a Sepic converter, or a Zeta converter.

7. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 5, characterized in that, The photovoltaic and energy storage unit includes: a photovoltaic port, an energy storage port, and a half-bridge unit. , and inductors , ; The half-bridge unit Output terminal and inductor The negative terminal of the inductor is connected; The positive terminal of the half-bridge unit is connected to the positive terminal of the photovoltaic port. Output terminal and inductor The negative terminal of the inductor is connected; The positive terminal is connected to the positive terminal of the energy storage port; The negative terminal of the photovoltaic port is connected to the negative terminal of the energy storage port, and the connection point serves as the first end of the photovoltaic and energy storage unit; the half-bridge unit Negative extreme and half-bridge unit The negative terminal is connected, and the connection point serves as the second end of the photovoltaic and energy storage unit; the half-bridge unit Positive end and half-bridge unit The positive end is connected, and the connection point serves as the third end of the photovoltaic and energy storage unit.

8. The partial power transfer type three-port DC / DC converter suitable for optical-storage-charge systems according to claim 7, characterized in that, The half-bridge unit , The switching devices are one or two of the following: field-effect transistors (MOSFETs), SiC MOSFETs, insulated-gate bipolar transistors (IGBTs), GaN switching devices, or diodes.

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