Multi-mode multi-port converter of optical energy storage system

Abstract

The invention relates to the technical field of electric energy conversion, in particular to a multi-mode multi-port converter of an optical storage energy system, which comprises a plurality of external ports and an electric energy conversion circuit, and the external ports are electrically connected with the electric energy conversion circuit; the external port comprises a photovoltaic cell port Uin, a storage battery port Ubat, a direct current load port R and a grid-connected port Ug; the electric energy conversion circuit comprises switch tubes S1 to S8, a diode VD1, a diode VD4, a first capacitor C1, a second capacitor C2, a first inductor L1 and a single-pole double-throw switch SPDT. Energy transfer from a photovoltaic cell to a storage battery and a load in an isolated island operation mode and from the storage battery to the load under the condition that the photovoltaic cell is not available can be realized; meanwhile, in a grid-connected operation mode, an LCL type filter circuit is adopted to improve the electric energy quality, electric energy conversion is carried out through a full-bridge inverter circuit, and the grid-connected function can be achieved by ensuring that the voltage of the grid-connected side is stable under the condition that the photovoltaic array is independent or cooperates with the storage battery.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to a multi-mode multi-port converter of a photovoltaic energy storage system. Background Art

[0002] Since photovoltaic power generation systems have the disadvantages of intermittency and volatility, it is difficult to meet the requirements of actual power grid transmission. Therefore, it is necessary to convert electric energy through converters to improve the utilization rate of photovoltaic energy storage power generation.

[0003] However, traditional converters can often only achieve simple power conversion, such as direct current-to-direct current (DC-DC) or direct current-to-alternating current (DC-AC) conversion, and the number of ports is limited. If multiple photovoltaic energy storage devices and multiple loads are to be connected, a corresponding number of converters need to be configured.

[0004] Although multi-port converters can integrate multiple ports in one converter and simultaneously connect photovoltaic panels, energy storage devices (such as battery packs, supercapacitors, etc.) and different electrical units of the load or power grid; traditional multi-port converters still use basic converter electronic circuits for combination. When converting electric energy, they can only realize one-way electric energy conversion from the photovoltaic energy storage end to the load end, and their functions are relatively simple. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a multi-mode multi-port converter for a photovoltaic energy storage system, comprising a plurality of external ports and an electric energy conversion circuit, wherein the external ports are electrically connected to the electric energy conversion circuit; the external ports include a photovoltaic cell port U in 、Battery port U bat , DC load port R and grid-connected port U g ;

[0006] The electric energy conversion circuit includes switch tubes S1-S8, diodes VD1, VD4, a first capacitor C1, a second capacitor C2, a first inductor L1 and a single-pole double-throw switch SPDT;

[0007] The photovoltaic cell port U in The positive electrode is connected to the anode of the diode VD1 and one end of the first capacitor C1 respectively, and the other end of the first capacitor C1 is connected to the photovoltaic cell port U in Negative connection;

[0008] The cathode of the diode VD1 is connected to one end of the first inductor L1 and the drain of the switch tube S3 respectively, and the source of the switch tube S3 is connected to the battery port U bat Positive connection, the battery terminal U bat The positive and negative electrodes are connected in parallel with a second capacitor C2;

[0009] The other end of the first inductor L1 is connected to the source of the switch tube S1, the drain of the switch tube S4, and the anode of the diode VD4 respectively. The cathode of the diode VD4 is connected to the source of the switch tube S2. The drain of the switch tube S2 is connected to the battery port U bat The positive electrode is connected; the drain of the switch tube S1 is connected to the battery port U bat The negative electrode is connected; the source of the switch tube S4 is connected to one end of the single-pole double-throw switch SPDT;

[0010] The other end contact 1 of the single-pole double-throw switch SPDT is electrically connected to the DC load port R, and the other end contact 2 is electrically connected to the grid-connected port U via the full-bridge inverter circuit composed of switch tubes S5-S8. g Electrical connection.

[0011] The full-bridge inverter circuit is composed of a series circuit of switch tubes S5 and S7, which is connected in parallel with a series circuit of switch tubes S6 and S8. The series node of the two series circuits is connected to the grid-connected port U g Electrical connection.

[0012] In a specific embodiment, an LCL type filter circuit is also connected between the single-pole double-throw switch SPDT and the full-bridge inverter circuit. The LCL type filter circuit includes a second inductor L2, a third inductor L3 and a third capacitor C3. One end of the second inductor L2 is electrically connected to contact 2 of the single-pole double-throw switch SPDT, the other end of the second inductor L2 is connected in series with one end of the third inductor L3, the other end of the third inductor L3 is connected to the full-bridge inverter circuit, and the third capacitor C3 is connected in parallel to the series node of the second inductor L2 and the third inductor L3.

[0013] In order to ensure that the multi-mode multi-port converter performs mode switching, the multi-mode multi-port converter is also electrically connected to a microcontroller, which is used to control the multi-mode multi-port converter to switch operating modes, which are divided into an island operating mode or a grid-connected operating mode.

[0014] The gates of the switch tubes S1-S8 are also used to connect to the microcontroller to obtain switch control signals. The switch tubes S1-S8 receive and turn on or off according to the switch control signals, changing the topology of the multi-mode multi-port converter to make it work in different input and output modes.

[0015] In a specific implementation, the input and output modes specifically include:

[0016] Working mode 1: switch tube S2 remains off, T O -T1 switching cycle, switch tubes S1 and S3 are turned on, and switch tube S4 is turned off; in T1-T2 switching cycle, switch tubes S1 and S3 are turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, photovoltaic cell port Uin With battery port U bat They are respectively used to supply power to the DC load port R;

[0017] Working mode 2: Switches S2 and S3 remain off, T O -T1 switching cycle, switch tube S1 is turned on, switch tube S4 is turned off; T1-T2 switching cycle, switch tube S1 is turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, photovoltaic cell port U in Provide power to DC load port R separately;

[0018] Working mode 3: switch tube S2 remains off, switch tube S3 remains on, T O -T1 switching cycle, switch tube S1 is turned on, switch tube S4 is turned off; T1-T2 switching cycle, switch tube S1 is turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, battery port U bat Provide power to the DC load port R;

[0019] Working mode 4: switch tube S3 remains off, T O -T1 switching cycle, switch tubes S2 and S4 are turned off, and switch tube S1 is turned on; in T1-T2 switching cycle, switch tubes S1 and S4 are turned off, and switch tube S2 is turned on. in For battery port U bat Power supply; During the T2-T3 switching cycle, the switch tubes S1 and S2 are turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the photovoltaic cell port U in Provides power to the DC load port R.

[0020] In addition, the input and output modes also include:

[0021] Working mode 5: switch tube S2 remains off, T O -T1 switching cycle, switch tubes S1 and S3 are turned on, and switch tube S4 is turned off; in T1-T2 switching cycle, switch tubes S1 and S3 are turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 2, photovoltaic cell port U in With battery port U bat The full-bridge inverter circuit converts DC power into AC power, which is the grid-connected port U g powered by;

[0022] Working mode 6: switch tube S2 remains off, switch tube S3 remains on, T O -T1 switching cycle, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 2, switch tube S1 is turned off, and grid-connected port U gThe first inductor L1 is reversely connected through the full-bridge inverter circuit; during the T1-T2 switching cycle, the switch tube S4 is turned off, the switch tube S1 is turned on, and the grid-connected port U g Reverse is the battery terminal U bat powered by.

[0023] The photovoltaic cell port U in Connected to the photovoltaic power generation system; the battery port U bat Connected to the energy storage system; the DC load port R is connected to the local load device; the grid-connected port U g Connect to the grid.

[0024] The multi-mode multi-port converter also includes input-output mode switching according to the output power of the photovoltaic power generation system, the remaining battery power of the energy storage system, and the operation mode, which is specifically:

[0025] When the operation mode is the island operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 1, and the photovoltaic battery port U in With battery port U bat They are respectively used to supply power to the DC load port R;

[0026] If the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power is less than the high threshold power and greater than the low threshold power, it switches to working mode 2, and the photovoltaic battery port U in Provide power to DC load port R separately;

[0027] If the output power of the photovoltaic power generation system does not reach the preset power threshold, and the remaining battery power is greater than the high threshold power, it switches to working mode 3, and the battery port U bat Provide power to the DC load port R;

[0028] If the output power of the photovoltaic power generation system reaches the preset power threshold and the remaining battery power is less than the low threshold power, it switches to working mode 4, and the photovoltaic battery port U in The battery port U bat And the DC load port R supplies power;

[0029] When the operation mode is the grid-connected operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 5, and the photovoltaic battery port U in With battery port U bat Connected to the grid, the grid-connected port U g powered by;

[0030] If the remaining battery power of the energy storage system is less than the low threshold power, it switches to working mode 6 and the grid-connected port U g Reverse is the battery terminal U bat powered by.

[0031] In order to extend the service life of each switch tube of the multi-mode multi-port converter, the power conversion circuit further includes a plurality of diodes, and the switch tubes S1-S8 are respectively connected in parallel with a single diode for protection.

[0032] Beneficial effects: The present invention is a multi-mode multi-port converter for a photovoltaic energy storage system. Based on the device multiplexing principle, the photovoltaic energy storage system can operate in two operating modes: an island operation mode and a grid-connected operation mode. In the island operation mode, an inductor is used to complete the energy buffering function of the converter. Four switch tubes realize energy scheduling of each port through a specific topological structure. The degree of integration is high, and the energy transfer from photovoltaic cells to batteries and loads in the island operation mode, and from batteries to loads when photovoltaic cells are unavailable, can be realized. At the same time, in the grid-connected operation mode, an LCL filter circuit is used to improve the power quality, and power conversion is performed through a full-bridge inverter circuit. The photovoltaic array can achieve grid-connected function by ensuring the stability of the grid-connected side voltage alone or in coordination with the battery, which can effectively improve the energy scheduling efficiency of the photovoltaic energy storage system and realize coordinated management and efficient utilization of multiple energy sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A topological structure diagram of a multi-mode multi-port converter of the present invention;

[0034] Figure 2 It is an equivalent circuit diagram of the switch states in different time periods within a cycle of the working mode of the present invention;

[0035] Figure 3 It is an equivalent circuit diagram of the switch states in different time periods within a cycle of the second working mode of the present invention;

[0036] Figure 4 It is an equivalent circuit diagram of the switch states in different time periods within a cycle of the working mode 3 of the present invention;

[0037] Figure 5 It is an equivalent circuit diagram of the switch states in different time periods within a cycle of the fourth working mode of the present invention;

[0038] Figure 6 The equivalent circuit diagram of the switch state in different time periods within a cycle of the working mode 5 of the present invention;

[0039] Figure 7 This is an equivalent circuit diagram of the switch states in different time periods within a cycle of working mode six of the present invention. DETAILED DESCRIPTION

[0040] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0041] See also Figure 1 This embodiment provides a multi-mode multi-port converter for a photovoltaic energy storage system, including a plurality of external ports and an electric energy conversion circuit, wherein the external ports include a photovoltaic cell port U in 、Battery port U bat , DC load port R and grid-connected port U g The external ports are respectively connected to the photovoltaic power generation system, the energy storage system, and the load end, and the photovoltaic cell port U in External photovoltaic power generation system battery, the battery port U bat The external energy storage system energy storage battery, the DC load port R is connected to the local load device, and the grid-connected port U g Connect to the power grid.

[0042] In order to realize the energy scheduling of each port of the multi-mode multi-port converter, the power conversion circuit includes switch tubes S1-S8, diodes VD1-VD 10 , a first capacitor C1, a second capacitor C2, a first inductor L1 and a single-pole double-throw switch SPDT.

[0043] Wherein, the photovoltaic cell port U in The positive electrode is connected to the anode of the diode VD1 and one end of the first capacitor C1 respectively, and the other end of the first capacitor C1 is connected to the photovoltaic cell port U in The negative pole is connected to the first capacitor C1, which is the photovoltaic cell port U in The filter capacitor.

[0044] The cathode of the diode VD1 is connected to one end of the first inductor L1 and the drain of the switch tube S3 respectively, and the source of the switch tube S3 is connected to the battery port U bat Positive connection, the battery terminal U bat The positive and negative electrodes are connected in parallel with a second capacitor C2, and the second capacitor C2 is connected to the battery port U bat The other end of the first inductor L1 is connected to the source of the switch tube S1, the drain of the switch tube S4, and the anode of the diode VD4 respectively. The cathode of the diode VD4 is connected to the source of the switch tube S2. The drain of the switch tube S2 is connected to the battery port U bat The positive electrode is connected; the drain of the switch tube S1 is connected to the battery port U bat Negative connection.

[0045] The source of the switch tube S4 is connected to one end of the single-pole double-throw switch SPDT; the contact 1 at the other end of the single-pole double-throw switch SPDT is electrically connected to the DC load port R, and the contact 2 at the other end is connected to the grid-connected port U via the full-bridge inverter circuit composed of the switch tubes S5-S8. g The full-bridge inverter circuit is composed of a series circuit of switch tubes S5 and S7, which is connected in parallel with a series circuit of switch tubes S6 and S8. The series node of the two series circuits is connected to the grid-connected port U g Electrical connection.

[0046] At the same time, in order to improve the power quality in the grid-connected state, an LCL-type filter circuit is also connected between the single-pole double-throw switch SPDT and the full-bridge inverter circuit. The LCL-type filter circuit includes a second inductor L2, a third inductor L3 and a third capacitor C3. One end of the second inductor L2 is electrically connected to contact 2 of the single-pole double-throw switch SPDT, the other end of the second inductor L2 is connected in series with one end of the third inductor L3, the other end of the third inductor L3 is connected to the full-bridge inverter circuit, and the third capacitor C3 is connected in parallel to the series node of the second inductor L2 and the third inductor L3.

[0047] In order to protect the switch tube, a diode is connected in parallel to the switch tubes S1-S8 respectively, and the diodes VD2, VD3, VD5, VD6, VD7, VD8, VD9, VD 10 Protect each switch tube.

[0048] The multi-mode multi-port converter is also electrically connected to a microcontroller, which controls the multi-mode multi-port converter to switch operating modes based on the power demand of the external port. The operating mode is divided into an island operating mode or a grid-connected operating mode.

[0049] The gates of the switch tubes S1-S8 are also used to connect to the microcontroller to obtain the switch control signal. The switch tubes S1-S8 receive and turn on or off according to the switch control signal, and change the topology of the multi-mode multi-port converter to make it work in different input and output modes, specifically including:

[0050] Working mode 1: Photovoltaic cell port U in With battery port U bat They are respectively used to supply power to the DC load port R;

[0051] like Figure 2 As shown, in this mode, the switch tube S2 remains off. Figure 2 In the figure above, T O - During the T1 switching cycle, the switch tubes S1 and S3 are turned on, the switch tube S4 is turned off, and the battery port U bat Charging the first inductor L1 for energy storage; Figure 2In the following figure, during the T1-T2 switching cycle, the switch tubes S1 and S3 are turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the photovoltaic cell port U in The electric energy of the first inductor L1 supplies power to the DC load port R simultaneously;

[0052] In working mode 1, the duty cycles of the switches S1, S2, and S3 are d1, d2, and d3 respectively. s Representing one switching cycle, using the volt-second balance law for the first inductor L1, we can obtain:

[0053] U bat d3T S +U in (d1-d3)T S =(U in -U o )(1-d1)T S ,

[0054] The above formula can be used to derive the relationship between the DC load port voltage, the photovoltaic cell port voltage, the battery port voltage and the duty cycle:

[0055]

[0056] Among them, U o Represents the DC load port voltage, T s represents a switching cycle, d1 represents the duty cycle of the switch tube S1, and d3 represents the duty cycle of the switch tube S3.

[0057] Working mode 2: Photovoltaic cell port U in Provide power to DC load port R separately;

[0058] like Figure 3 As shown, in this mode, the switch tubes S2 and S3 remain off. Figure 3 In the figure above, T O - During the T1 switching cycle, the switch tube S1 is turned on, the switch tube S4 is turned off, and the photovoltaic cell port U in Charging the first inductor L1 for energy storage; Figure 3 In the following figure, during the T1-T2 switching cycle, the switch tube S1 is turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the photovoltaic cell port U in Provide power to the DC load port R;

[0059] Similarly, by applying the volt-second balance law to the first inductor L1 in working mode 2, the relationship between the DC load port voltage and the photovoltaic cell port voltage can be obtained:

[0060]

[0061] Among them, Uo represents the DC load port voltage, and d1 represents the duty cycle of the switch tube S1.

[0062] Working mode 3: Battery port U bat Provide power to the DC load port R;

[0063] like Figure 4 As shown, in this mode, the switch tube S2 remains off and the switch tube S3 remains on. Figure 4 In the figure above, T O - During the T1 switching cycle, the switch tube S1 is turned on, the switch tube S4 is turned off, and the battery port U bat Charging the first inductor L1 for energy storage; Figure 4 In the following figure, during the T1-T2 switching cycle, the switch tube S1 is turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the battery port U bat Provide power to the DC load port R;

[0064] Working mode 3 is similar to the photovoltaic cell port supplying power to the DC load alone. By applying the volt-second balance law to the first inductor L1, the relationship between the DC load port voltage and the photovoltaic array port voltage can be obtained:

[0065]

[0066] Among them, U o represents the DC load port voltage, and d3 represents the duty cycle of the switch tube S3.

[0067] Working mode 4: Photovoltaic cell port U in The battery port U bat And the DC load port R supplies power;

[0068] like Figure 5 As shown, in this mode, the switch tube S3 remains off, T O - During the T1 switching cycle, the switch tubes S2 and S4 are turned off, the switch tube S1 is turned on, and the photovoltaic cell port U in The first inductor L1 is charged for energy storage; during the T1-T2 switching cycle, the switch tubes S1 and S4 are turned off, the switch tube S2 is turned on, and the photovoltaic cell port U in For battery port U bat Power supply; During the T2-T3 switching cycle, the switch tubes S1 and S2 are turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the photovoltaic cell port U in Provide power to the DC load port R;

[0069] In working mode 4, the photovoltaic power generation system provides energy for both the DC load equipment and the energy storage system battery. O -T1 stage, photovoltaic cell port Uin Provide energy for the first inductor L1, the first inductor L1 stores energy, at this time U L =U in ; In the T1-T2 stage, the photovoltaic cell port is used for battery energy storage. At this time, U L =U in -U bat ; In the T2-T3 stage, the photovoltaic cell port outputs power to the DC load end. At this time, U L =U in -U o .

[0070] Applying the volt-second balance law to the first inductor L1, the relationship between each port and the duty cycle in one switching cycle is:

[0071]

[0072] Among them, U bat Represents the battery terminal voltage, U in Represents the photovoltaic cell terminal voltage, U o represents the DC load port voltage, d1 represents the duty cycle of the switch tube S1, and d2 represents the duty cycle of the switch tube S2.

[0073] Working mode 5: Photovoltaic battery port U in With battery port U bat Connected to the grid, the grid-connected port U g powered by;

[0074] like Figure 6 As shown, in this mode, the switch tube S2 remains off. Figure 6 In the figure above, T O - During the T1 switching cycle, the switch tubes S1 and S3 are turned on, the switch tube S4 is turned off, and the battery port U bat Charging the first inductor L1 for energy storage; Figure 6 In the following figure, during the T1-T2 switching cycle, the switch tubes S1 and S3 are turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 2, and the photovoltaic cell port U in The electric energy of the first inductor L1 is converted into AC power through the full-bridge inverter circuit, which is the grid-connected port U g powered by;

[0075] Working mode 5: In the grid-connected state, the relationship between the grid-connected port and each port and the duty cycle is:

[0076]

[0077] Among them, U bat Represents the battery terminal voltage, U in Represents the photovoltaic cell terminal voltage, U grepresents the load voltage of the grid-connected port, d1 represents the duty cycle of the switch tube S1, and d3 represents the duty cycle of the switch tube S3.

[0078] Working mode 6: Grid-connected port U g Reverse is the battery terminal U bat powered by;

[0079] like Figure 7 As shown, in this mode, the switch tube S2 remains off, the switch tube S3 remains on, and T O -T1 switching cycle, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 2, switch tube S1 is turned off, and grid-connected port U g The first inductor L1 is reversely connected via the full-bridge inverter circuit, and the first inductor L1 and the switch tube S3 form a buck circuit for step-down charging; in the T1-T2 switching cycle, the switch tube S4 is turned off and the switch tube S1 is turned on.

[0080] In working mode 6, the multi-mode multi-port converter is in the buck working circuit. At this time, the battery of the grid-connected energy storage system is charged, and the voltage relationship between the two ports is:

[0081] U bat =U g d4,

[0082] Among them, U bat Represents the battery terminal voltage, U g represents the load voltage of the grid-connected port, and d4 represents the duty cycle of the switch tube S4.

[0083] Based on the above six working modes, the multi-mode multi-port converter switches the working mode according to the output power of the photovoltaic power generation system, the remaining battery power of the energy storage system, and the operating mode, which are specifically:

[0084] When the operation mode is the island operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 1, and the photovoltaic battery port U in With battery port U bat They are respectively used to supply power to the DC load port R;

[0085] If the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power is less than the high threshold power and greater than the low threshold power, it switches to working mode 2, and the photovoltaic battery port U in Provide power to DC load port R separately;

[0086] If the output power of the photovoltaic power generation system does not reach the preset power threshold, and the remaining battery power is greater than the high threshold power, it switches to working mode 3, and the battery port U batProvide power to the DC load port R;

[0087] If the output power of the photovoltaic power generation system reaches the preset power threshold and the remaining battery power is less than the low threshold power, it switches to working mode 4, and the photovoltaic battery port U in The battery port U bat And the DC load port R supplies power;

[0088] When the operation mode is the grid-connected operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 5, and the photovoltaic battery port U in With battery port U bat Connected to the grid, the grid-connected port U g powered by;

[0089] If the remaining battery power of the energy storage system is less than the low threshold power, it switches to working mode 6 and the grid-connected port U g Reverse is the battery terminal U bat powered by.

Claims

1. A multi-mode multi-port converter for a photovoltaic energy storage system, characterized in that: It includes several external ports and an electric energy conversion circuit, wherein the external ports are electrically connected to the electric energy conversion circuit; the external ports include a photovoltaic cell port U in 、Battery port U bat , DC load port R and grid-connected port U g ; The electric energy conversion circuit includes switch tubes S1-S8, diodes VD1, VD4, a first capacitor C1, a second capacitor C2, a first inductor L1 and a single-pole double-throw switch SPDT; The photovoltaic cell port U in The positive electrode is connected to the anode of the diode VD1 and one end of the first capacitor C1 respectively, and the other end of the first capacitor C1 is connected to the photovoltaic cell port U in Negative connection; The cathode of the diode VD1 is connected to one end of the first inductor L1 and the drain of the switch tube S3 respectively, and the source of the switch tube S3 is connected to the battery port U bat Positive connection, the battery terminal U bat The positive and negative electrodes are connected in parallel with a second capacitor C2; The other end of the first inductor L1 is connected to the source of the switch tube S1, the drain of the switch tube S4, and the anode of the diode VD4 respectively. The cathode of the diode VD4 is connected to the source of the switch tube S2. The drain of the switch tube S2 is connected to the battery port U bat The positive electrode is connected; the drain of the switch tube S1 is connected to the battery port U bat The source of the switch tube S4 is connected to one end of the single-pole double-throw switch SPDT; the contact one at the other end of the single-pole double-throw switch SPDT is electrically connected to the DC load port R, and the contact two at the other end is connected to the grid-connected port U via the full-bridge inverter circuit composed of the switch tubes S5-S8. g Electrical connection.

2. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 1, characterized in that: The full-bridge inverter circuit is composed of a series circuit of switch tubes S5 and S7, which is connected in parallel with a series circuit of switch tubes S6 and S8. The series node of the two series circuits is connected to the grid-connected port U g Electrical connection.

3. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 2, characterized in that: An LCL type filter circuit is also connected between the single-pole double-throw switch SPDT and the full-bridge inverter circuit. The LCL type filter circuit includes a second inductor L2, a third inductor L3 and a third capacitor C3. One end of the second inductor L2 is electrically connected to contact 2 of the single-pole double-throw switch SPDT, the other end of the second inductor L2 is connected in series with one end of the third inductor L3, the other end of the third inductor L3 is connected to the full-bridge inverter circuit, and the third capacitor C3 is connected in parallel to the series node of the second inductor L2 and the third inductor L3.

4. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 1, characterized in that: The multi-mode multi-port converter is also electrically connected to a microcontroller, and the microcontroller is used to control the multi-mode multi-port converter to switch operating modes, and the operating mode is divided into an island operating mode or a grid-connected operating mode.

5. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 4, characterized in that: The gates of the switch tubes S1-S8 are also used to connect to the microcontroller to obtain switch control signals. The switch tubes S1-S8 receive and turn on or off according to the switch control signals, changing the topology of the multi-mode multi-port converter to make it work in different input and output modes.

6. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 5, characterized in that: The input and output modes specifically include: Working mode 1: switch tube S2 remains off, T O -T1 switching cycle, switch tubes S1 and S3 are turned on, and switch tube S4 is turned off; in T1-T2 switching cycle, switch tubes S1 and S3 are turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, photovoltaic cell port U in With battery port U bat They are respectively used to supply power to the DC load port R; Working mode 2: Switches S2 and S3 remain off, T O -T1 switching cycle, switch tube S1 is turned on, switch tube S4 is turned off; T1-T2 switching cycle, switch tube S1 is turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, photovoltaic cell port U in Provide power to DC load port R separately; Working mode 3: switch tube S2 remains off, switch tube S3 remains on, T O -T1 switching cycle, switch tube S1 is turned on, switch tube S4 is turned off; T1-T2 switching cycle, switch tube S1 is turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 1, battery port U bat Provide power to the DC load port R; Working mode 4: switch tube S3 remains off, T O -T1 switching cycle, switch tubes S2 and S4 are turned off, and switch tube S1 is turned on; in T1-T2 switching cycle, switch tubes S1 and S4 are turned off, and switch tube S2 is turned on. in For battery port U bat Power supply; During the T2-T3 switching cycle, the switch tubes S1 and S2 are turned off, the switch tube S4 is turned on, the single-pole double-throw switch SPDT closes contact 1, and the photovoltaic cell port U in Provides power to the DC load port R.

7. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 5, characterized in that: The input and output modes also include: Working mode 5: switch tube S2 remains off, T O -T1 switching cycle, switch tubes S1 and S3 are turned on, and switch tube S4 is turned off; in T1-T2 switching cycle, switch tubes S1 and S3 are turned off, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 2, photovoltaic cell port U in With battery port U bat The full-bridge inverter circuit converts DC power into AC power, which is the grid-connected port U g powered by; Working mode 6: switch tube S2 remains off, switch tube S3 remains on, T O -T1 switching cycle, switch tube S4 is turned on, single-pole double-throw switch SPDT closes contact 2, switch tube S1 is turned off, and grid-connected port U g The first inductor L1 is reversely connected through the full-bridge inverter circuit; during the T1-T2 switching cycle, the switch tube S4 is turned off, the switch tube S1 is turned on, and the grid-connected port U g Reverse is the battery terminal U bat powered by.

8. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 6 or 7, characterized in that: The photovoltaic cell port U in Connected to the photovoltaic power generation system; the battery port U bat Connected to the energy storage system; the DC load port R is connected to the local load device; the grid-connected port U g Connect to the grid.

9. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 8, characterized in that: It also includes switching the input and output modes according to the output power of the photovoltaic power generation system, the remaining battery power of the energy storage system, and the operation mode, which are specifically: When the operation mode is the island operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 1, and the photovoltaic battery port U in With battery port U bat They are respectively used to supply power to the DC load port R; If the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power is less than the high threshold power and greater than the low threshold power, it switches to working mode 2, and the photovoltaic battery port U in Power the DC load port R separately; If the output power of the photovoltaic power generation system does not reach the preset power threshold, and the remaining battery power is greater than the high threshold power, it switches to working mode 3, and the battery port U bat Provide power to the DC load port R; If the output power of the photovoltaic power generation system reaches the preset power threshold and the remaining battery power is less than the low threshold power, it switches to working mode 4, and the photovoltaic battery port U in The battery port U bat And the DC load port R supplies power; When the operation mode is the grid-connected operation mode, if the output power of the photovoltaic power generation system reaches the preset power threshold, and the remaining battery power of the energy storage system is greater than the high threshold power, it switches to operation mode 5, and the photovoltaic battery port U in With battery port U bat Connected to the grid, the grid-connected port U g powered by; If the remaining battery power of the energy storage system is less than the low threshold power, it switches to working mode 6 and the grid-connected port U g Reverse is the battery terminal U bat powered by.

10. The multi-mode multi-port converter of the photovoltaic energy storage system according to claim 1, characterized in that: The electric energy conversion circuit also includes a plurality of diodes, and the switch tubes S1-S8 are respectively connected in parallel with a single diode for protection.

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