Optical storage integrated converter system with flexible distribution and storage

Abstract

The invention provides an optical storage integrated converter system with flexible distribution and storage, and relates to the technical field of optical storage systems. The optical storage integrated converter system comprises a photovoltaic array, a photovoltaic grid-connected inverter directly connected with a photovoltaic array interface, and a direct current coupling energy storage converter connected in series with a direct current bus in the middle of the photovoltaic grid-connected inverter. Wherein the photovoltaic array emits direct current, and a three-port power control algorithm is adopted at a direct current bus to control the flexible distribution and storage light storage integrated converter system to carry out energy conversion. Under the condition that an existing DC / DC and DC / AC two-stage grid-connected framework of a photovoltaic product is not changed, a BUS interface of DC / DC and DC / AC two-stage conversion in a photovoltaic grid-connected inverter is extracted, the stability of a control algorithm can be effectively improved, meanwhile, the structure of an optical storage system is simplified, the overall cost of the system is effectively reduced, the efficiency of the system is improved, and the application range of the system is widened. The system size is reduced and the power density is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic storage systems, and in particular to a photovoltaic storage integrated converter system with flexible storage configuration. Background Art

[0002] The photovoltaic storage system is designed based on the distributed photovoltaic grid-connected system. The existing distributed photovoltaic grid-connected system can be divided into isolated type and non-isolated type according to whether there is an industrial frequency isolation transformer. The isolated distributed photovoltaic grid-connected system adopts a typical string-type grid-connected architecture. Figure 1 As shown in the figure, the system consists of a photovoltaic array (PV), which is the core power generation component that converts solar energy into direct current; a maximum power point tracking system (MPPT, Maximum Power Point Tracking system) that continuously detects the current and voltage changes of the photovoltaic array, and adjusts the PWM drive signal duty cycle of the DC / DC converter according to the changes, which can dynamically adjust the working state of the photovoltaic array to ensure that the maximum power is always output; a DC / AC inverter, which is responsible for converting direct current into alternating current; and an industrial frequency isolation transformer, which provides electrical isolation for the system, which not only complies with power safety regulations, but also effectively reduces common mode current and improves system stability and reliability. The non-isolated architecture diagram is shown in the figure below. Figure 2 As shown, the absence of an industrial frequency isolation transformer simplifies the system structure, reduces costs and improves efficiency.

[0003] Existing solar storage systems use Figure 3 The architecture shown in the figure connects a bidirectional AC / DC energy storage module to the output side of the complete photovoltaic grid-connected inverter. The system assumes that the grid operation state is relatively balanced by default and adopts a balanced power output mode. When the photovoltaic power generation is sufficient and the grid-connected electricity price is at a low point, the system automatically stores the excess electricity in the energy storage unit to achieve effective storage of electricity; during peak power consumption periods and when the grid-connected electricity price is high, the energy storage unit releases the stored electricity to supply power to the grid load. Through the "peak shaving and valley filling" strategy, the configuration of power resources in time and space is optimized, and the stability and economy of the power system are improved.

[0004] However, this photovoltaic storage system, which connects a bidirectional AC / DC energy storage module to the output of a complete photovoltaic grid-connected inverter, has low efficiency. Summary of the invention

[0005] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a photovoltaic-storage integrated converter system with flexible storage configuration, which solves the technical problem of low efficiency of the existing photovoltaic-storage system.

[0006] (II) Technical solution To achieve the above objectives, the present invention is implemented through the following technical solutions: The present invention provides a photovoltaic-storage integrated converter system with flexible storage, comprising a photovoltaic array, a photovoltaic grid-connected inverter directly connected to an interface of the photovoltaic array, and a DC-coupled energy storage converter connected in series with a DC busbar in the middle of the photovoltaic grid-connected inverter; The photovoltaic grid-connected inverter includes a DC / AC inverter and a plurality of DC / DC converters regulated by a maximum power point tracking system, wherein the connection ends of the first sides of the plurality of DC / DC converters are directly connected to the photovoltaic array interface respectively, and the connection ends of the second sides are all connected to the DC bus in the middle of the photovoltaic grid-connected inverter, the connection end of the first side of the DC / AC inverter is connected to the DC bus, and the second side is connected to the grid or the load; The photovoltaic array generates direct current, and a three-port power control algorithm is used at the direct current bus to control a flexible photovoltaic and storage integrated converter system for energy conversion.

[0007] Preferably, the DC-coupled energy storage converter comprises a bidirectional DC / DC converter and an energy storage unit, wherein a connection end on a first side of the bidirectional DC / DC converter is connected to a DC bus, and a connection end on a second side is connected to two connection ends of the energy storage unit.

[0008] Preferably, the three-port power control algorithm is used at the DC bus to control the flexible storage photovoltaic integrated converter system to perform energy conversion, including: When power generation is sufficient and the grid-connected electricity price is low, the DC power on the primary DC bus is converted to the energy storage unit through a bidirectional DC / DC converter. When power consumption is at peak and the grid-connected electricity price is high, the DC power in the energy storage unit is released to the DC bus through a bidirectional DC / DC converter, and then inverted into AC power by a DC / AC inverter to supply the grid or load.

[0009] Preferably, the bidirectional DC / DC converter includes a first filter inductor, a first switch tube, and a second switch tube, wherein the second end of the second switch tube is connected to the first end of the first switch tube, and the first end of the second switch tube and the second end of the first switch tube are respectively connected to the two ends of the energy storage unit; the first end of the first filter inductor is connected to the common end of the first switch tube and the first switch tube, the second end of the filter inductor is connected to the positive power line of the DC bus, and the second end of the first switch tube is connected to the negative power line of the DC bus.

[0010] Preferably, when the bidirectional DC / DC converter works in the forward direction, the current flows from the DC bus to the energy storage unit, and the bidirectional DC / DC converter includes two switching modes: Mode 1: The first switch is turned on, the second switch is turned off, and the bidirectional DC / DC converter converts the photovoltaic power generation voltage U on the photovoltaic array and the DC bus inWhen added to the first filter inductor, the current of the first filter inductor increases linearly, and the first filter inductor stores energy; Mode 2: The first switch is turned off, the second switch is turned on, and the photovoltaic power generation voltage U on the photovoltaic array and DC bus is in Together with the first filter inductor, the energy storage unit is charged and stored.

[0011] Preferably, when the bidirectional DC / DC converter works in reverse, the current flows from the energy storage unit to the DC bus, and the bidirectional DC / DC converter includes two switching modes: Mode 1: The first switch tube is turned off, the second switch tube is turned on, and the current of the first filter inductor increases linearly; Mode 2: The first switch tube is turned on, the second switch tube is turned off, the current of the first filter inductor cannot change suddenly, and the energy in the first filter inductor is released to the DC bus.

[0012] Preferably, the bidirectional DC / DC converter includes a second filter inductor, a third switch tube and a fourth switch tube, wherein the second end of the second filter inductor is connected to the first end of the fourth switch tube, and the second end of the fourth switch tube and the first end of the second filter inductor are respectively connected to the two ends of the energy storage unit; the second end of the third switch tube is connected to the common end of the fourth switch tube and the second filter inductor, the first end of the third switch tube is connected to the positive power line of the DC bus, and the second end of the fourth switch tube is connected to the negative power line of the DC bus.

[0013] Preferably, the energy storage unit includes a battery or a supercapacitor.

[0014] Preferably, the output of the photovoltaic grid-connected inverter supplies power to the grid or load via an industrial frequency isolation transformer.

[0015] Preferably, the output of the photovoltaic grid-connected inverter directly supplies power to the grid or load.

[0016] (III) Beneficial effects The present invention provides a photovoltaic-storage integrated converter system with flexible storage configuration. Compared with the prior art, it has the following beneficial effects: A flexible photovoltaic storage integrated converter system of the present invention comprises a photovoltaic array, a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface, and a DC-coupled energy storage converter connected in series with the DC bus in the middle of the photovoltaic grid-connected inverter; wherein the photovoltaic array emits direct current, and a three-port power control algorithm is used at the DC bus in the middle of the photovoltaic grid-connected inverter to control the flexible photovoltaic storage integrated converter system for energy conversion. The present invention extracts the intermediate DC bus (BUS) interface of the DC / DC and DC / AC two-stage conversion in the photovoltaic grid-connected inverter without changing the existing DC / DC and DC / AC two-stage grid-connected architecture of photovoltaic products, which can effectively improve the stability of the control algorithm. At the same time, it simplifies the structure of the photovoltaic storage system, effectively reduces the overall system cost, improves system efficiency, reduces system volume, and increases power density. In addition, the present invention adopts a three-port power control algorithm and deeply integrates the distribution network to develop a new generation of adaptive and flexible photovoltaic and storage integrated converter system for the distribution network, realizing energy injection and extraction with three-phase voltage tracking and flexible networking, fully guaranteeing photovoltaic power generation, and flexibly realizing photovoltaic and storage DC networking, solving the problem of time and space misalignment between distributed photovoltaic power generation and grid power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is the architecture diagram of the existing isolated distributed photovoltaic grid-connected system; Figure 2 This is the architecture diagram of the existing non-isolated distributed photovoltaic grid-connected system; Figure 3 This is the architecture diagram of the existing solar storage system; Figure 4 This is a schematic diagram of a flexible photovoltaic and storage integrated converter system according to an embodiment of the present invention; Figure 5 for Figure 4 A first example of a framework diagram is shown; Figure 6 for Figure 4 A second example of an architecture diagram is shown. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that, for the convenience of description, the switch IGBT is used to represent the controllable (on and off) switch tube in the embodiment of the present invention, but the switch tube in the present invention is not limited to IGBT. Take IGBT as an example for explanation. The first end of the IGBT refers to the collector, the second end refers to the emitter, and the control end refers to the gate. A driving control signal is applied to the control end of each switch tube in the embodiment of the present invention. For the sake of brevity, it will not be repeated later. The power switch tube in the embodiment of the present invention can also be implemented by other controllable switch tube devices other than IGBT, such as MOSFET. At the same time, in order to ensure the normal operation of each switch device in the embodiment of the present invention, a freewheeling diode needs to be connected in parallel to each switch device. The parallel connection direction of the freewheeling diode is related to the type of the switch device. The technician can set it according to the type of the switch device, which is not limited here. If not specified, the switch device defaults to including a freewheeling diode, which will be pointed out in this embodiment in special cases.

[0021] The embodiments of the present application solve the technical problem of low efficiency of existing photovoltaic storage systems by providing a photovoltaic storage integrated converter system with flexible storage configuration, and realize the extraction of the intermediate DC bus (BUS) interface of the DC / DC and DC / AC two-stage conversion in the photovoltaic grid-connected inverter, which can effectively improve the stability of the control algorithm. At the same time, it simplifies the structure of the photovoltaic storage system, effectively reduces the overall system cost, improves system efficiency, reduces system volume, and increases power density.

[0022] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows: Existing distributed photovoltaic grid-connected systems can be divided into isolated and non-isolated types according to whether there is an industrial frequency isolation transformer. Figure 1 As shown in the figure, it is mainly composed of photovoltaic array PV, maximum power point tracking system MPPT (the maximum power tracking system continuously detects the current and voltage changes of the photovoltaic array, and adjusts the PWM drive signal duty cycle of the DC / DC converter according to the changes), DC / AC inverter and power frequency isolation transformer. It is a typical string photovoltaic grid-connected. The non-isolated architecture is shown in the figure Figure 2 As shown, the absence of an industrial frequency isolation transformer simplifies the system structure, reduces costs and improves efficiency.

[0023] From the above two existing photovoltaic grid-connected design architectures, it can be seen that the existing complete set of converters cannot extract the intermediate DC bus BUS interface of the DC / DC and DC / AC two-stage conversion, and the control algorithm cannot work stably. Figure 3 The architecture shown is that the output after a complete set of photovoltaic grid-connected inverters is connected to a bidirectional AC / DC energy storage module. When photovoltaic power generation is sufficient and the grid-connected electricity price is low, the electricity is stored in the energy storage module; when the electricity consumption is at peak and the grid-connected electricity price is high, the electricity is released to supply the grid load. However, the bidirectional AC / DC energy storage module connected in this solution will result in low efficiency, large size and high cost of the photovoltaic storage system.

[0024] To solve the above problems, the embodiment of the present invention proposes a flexible photovoltaic storage integrated converter system, which simplifies the structure of the photovoltaic storage system, can effectively reduce the overall system cost, improve device efficiency, reduce system volume, and increase power density. At the same time, the system solves the problem of the blockage caused by the time and space misalignment between distributed photovoltaic power generation and grid power consumption, which cannot be fully reflected in value, and obtains a new type of differentiated photovoltaic storage that can deeply integrate power distribution needs.

[0025] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0026] The embodiment of the present invention provides a photovoltaic storage integrated converter system with flexible storage configuration, such as Figure 4 As shown, it includes a photovoltaic array, a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface, and a DC-coupled energy storage converter connected in series with a DC bus in the middle of the photovoltaic grid-connected inverter; The photovoltaic grid-connected inverter includes a DC / AC inverter and a plurality of DC / DC converters regulated by a maximum power point tracking system, wherein the connection ends of the first sides of the plurality of DC / DC converters are directly connected to the photovoltaic array interface respectively, and the connection ends of the second sides are all connected to the DC bus in the middle of the photovoltaic grid-connected inverter, the connection end of the first side of the DC / AC inverter is connected to the DC bus, and the second side is connected to the grid or the load; The photovoltaic array generates direct current, and a three-port power control algorithm is used at the direct current bus to control a flexible photovoltaic and storage integrated converter system for energy conversion.

[0027] It should be noted that Figure 4 The system architecture shown uses a non-isolated type, but it does not mean that the present invention is only used for non-isolated types. The embodiments of the present invention are also applicable to isolated distributed photovoltaic grid-connected systems, so that the system's carrying and absorbing capacity is not limited by the capacity of the power frequency isolation transformer. In the specific implementation process, the AC current output by the photovoltaic grid-connected inverter is to single / three-phase loads, small industrial and commercial / household photovoltaic three-phase, power grids, etc.

[0028] Combine the following Figure 4 , Figure 5 and Figure 6 A detailed description of the flexible photovoltaic and storage integrated converter system is given below: In the specific implementation process, the DC-coupled energy storage converter includes a bidirectional DC / DC converter and an energy storage unit, wherein the connection ends on both sides of the bidirectional DC / DC converter are respectively connected to the DC bus (including the positive and negative DC bus) and the two interfaces (positive and negative interfaces) of the energy storage unit. The bidirectional DC / DC converter can work in both directions, so that the DC-coupled energy storage converter can realize the bidirectional flow of energy in different working modes and realize the charging or discharging of the energy storage unit. The bidirectional DC / DC converter in the DC-coupled energy storage converter can select the BUCK circuit or the BOOST circuit.

[0029] The photovoltaic grid-connected inverter includes a DC / AC inverter and several DC / DC converters regulated by a maximum power point tracking system. The connection end of the first side of the DC / DC converter is directly connected to the photovoltaic array interface, and the connection end of the second side is connected to the DC bus. The connection end of the first side of the DC / AC inverter is connected to the DC bus, and the second side is connected to the grid or load.

[0030] The flexible storage-equipped photovoltaic-storage integrated converter system according to the embodiment of the present invention and Figure 3 Compared with the existing photovoltaic storage system architecture shown in the figure, the energy conversion is four times, but the loss of the two is quite different: Among them, the existing solution is that the DC power generated by distributed photovoltaics is converted into AC power after DC / DC conversion. For the AC-coupled energy storage conversion process, when the power generation is sufficient and the grid-connected electricity price is low, the AC power is stored in the energy storage unit through AC / DC conversion. When the power consumption is at peak and the grid-connected electricity price is high, the DC power is released through DC / AC conversion and supplied to the grid or load.

[0031] The scheme of the embodiment of the present invention is: first, the DC power generated by the distributed photovoltaic is converted once by DC / DC. At this time, the DC-coupled energy storage converter connected in series with the DC bus adopts a three-port power control algorithm to start the judgment work. For the DC-coupled energy storage conversion process, when the power generation is sufficient and the grid-connected electricity price is low, the DC power on the DC bus is converted to the energy storage unit through a bidirectional DC / DC converter. When the power consumption is at a peak and the grid-connected electricity price is high, the DC power in the energy storage unit is released to the DC bus through a bidirectional DC / DC converter, and then inverted into AC power by a DC / AC inverter to supply the power grid or load.

[0032] Under the condition of distributed photovoltaic power generation in the same external environment, the two DC-coupled energy storage conversion processes of the present invention are both DC / DC energy conversion, and are directly connected in series with the DC bus for internal DC-coupled energy storage. Compared with the two DC / AC energy storage energy conversion processes of the traditional photovoltaic storage solution architecture, the embodiment of the present invention significantly improves the photovoltaic storage power generation efficiency, reduces the AC / DC power conversion loss in the intermediate energy storage conversion process, and completes the energy conversion within the integrated system, which simplifies the structure of the photovoltaic storage system, reduces the system volume, and improves the power density.

[0033] In addition, it should be noted that if the flexible storage photovoltaic integrated converter system proposed in the embodiment of the present invention is used in an isolated working condition with an industrial frequency isolation transformer, distributed photovoltaic power generation does not need to consider the problem of insufficient overall grid absorption capacity caused by the limited capacity of the industrial frequency isolation transformer. When distributed photovoltaic power generation is sufficient and the on-grid electricity price is low, the energy of new energy can be stored in the energy storage unit through the three-port power control algorithm. When the electricity consumption is at peak and the on-grid electricity price is high, the stored energy can be supplied to the grid users to achieve high cost performance.

[0034] In the specific implementation process, the energy storage unit in the DC coupled energy storage converter can be various batteries or super capacitors, etc. At the same time, the bidirectional DC / DC converter in the DC coupled energy storage converter has various forms, as long as the bidirectional DC / DC converter can meet the requirements of realizing bidirectional flow of energy in different working modes, and can select BUCK circuit or BOOST circuit. The embodiment of the present invention provides two specific bidirectional DC / DC converters, such as Figure 5 and Figure 6 As shown, Figure 5 The bidirectional DC / DC converter in the embodiment includes a first filter inductor L1, two switch tubes T1 and T2 to form a chopper circuit topology, wherein the second end of the second switch tube T2 is connected to the first end of the first switch tube T1, and the first end of the second switch tube T2 and the second end of the first switch tube T1 are respectively connected to the two ends of the energy storage unit; the first end of the filter inductor L1 is connected to the common end of the first switch tube T1 and the first switch tube T2, the second end of the filter inductor L1 is connected to the positive power line (positive bus) of the DC bus, and the second end of the first switch tube T1 is connected to the negative power line (negative bus) of the DC bus. The bidirectional DC / DC converter can work in both directions, and its forward direction is defined as the DC bus flowing to the energy storage unit. When working in the forward direction, the bidirectional DC / DC converter is a BOOST circuit; its reverse direction is defined as the flow from the energy storage unit to the DC bus. When working in the reverse direction, the bidirectional DC / DC converter is a BUCK circuit.

[0035] Figure 6The bidirectional DC / DC converter includes a second filter inductor L2, two switch tubes T3 and T4 to form a chopper circuit topology, wherein the second end of the second filter inductor L2 is connected to the first end of the fourth switch tube T4, and the second end of the fourth switch tube T4 and the first end of the second filter inductor L2 are respectively connected to the two ends of the energy storage unit; the second end of the third switch tube T3 is connected to the common end of the fourth switch tube T4 and the second filter inductor L2, the first end of the third switch tube T3 is connected to the positive power line (positive bus) of the DC bus, and the second end of the fourth switch tube T4 is connected to the negative power line (negative bus) of the DC bus.

[0036] Below Figure 5 The three-port power control algorithm is described in detail in the flexible storage-equipped photovoltaic-storage integrated converter system shown in the figure: The three-port power control algorithm determines and controls the energy flow of the DC bus. When the distributed photovoltaic power generation is sufficient and the on-grid electricity price is low, the DC-coupled energy storage converter works in the forward direction. At this time, the bidirectional DC / DC converter is a BOOST converter with two switching modes: Mode 1, the first switch tube T1 is turned on, and the second switch tube T2 is turned off. The converter converts the photovoltaic array and the photovoltaic power generation voltage U after MPPT processing in Added to the first filter inductor L1, the current of the first filter inductor L1 increases linearly, and the first filter inductor L1 stores energy; Mode 2, the first switch tube T1 is turned off, the second switch tube T2 is turned on, and the photovoltaic array and the photovoltaic power generation voltage U after MPPT processing in Together with the first filter inductor L1, the energy storage unit is charged and stored. The two working modes realize the storage of abundant photovoltaic power generation and the electric energy with the market electricity price of "valley price", thus avoiding the two major contradictions of insufficient grid carrying capacity in the photovoltaic "red zone" and sufficient distributed photovoltaic power generation but low on-grid electricity price at the same time.

[0037] The three-port power control algorithm determines and controls the energy flow of the DC bus. When the power grid is at its peak and the on-grid electricity price is high, the DC-coupled energy storage converter works in reverse. At this time, the bidirectional DC / DC converter is a BUCK converter. The switch tubes T1 and T2 form a chopper circuit to modulate the voltage of the energy storage unit and output it to the DC bus in the middle of the photovoltaic grid-connected inverter. Its two working modes are: Mode 1, the first switch tube T1 is turned off, the second switch tube T2 is turned on, and the current of the first filter inductor L1 increases linearly; Mode 2, the first switch tube T1 is turned on, the second switch tube T2 is turned off, the current of the first filter inductor L1 cannot change suddenly, and the energy in the first filter inductor L1 is released to the DC bus. The two working modes realize the release of the electric energy stored in the energy storage unit with a market price of "valley price" to the peak power consumption and high on-grid electricity price "peak price" time period, thereby achieving the high profit effect of "peak-valley arbitrage".

[0038] Figure 6The flexible photovoltaic storage integrated converter system shown in the figure Figure 5 The three-port power control algorithm of the flexible storage-equipped photovoltaic-storage integrated converter system shown is similar and will not be repeated here.

[0039] In summary, compared with the prior art, the present invention has the following beneficial effects: 1. The embodiment of the present invention realizes the extraction of the intermediate DC bus (BUS) interface of the DC / DC and DC / AC two-stage conversion in the photovoltaic grid-connected inverter without changing the existing DC / DC and DC / AC two-stage grid-connected architecture of photovoltaic products, which can effectively improve the stability of the control algorithm. At the same time, it simplifies the structure of the photovoltaic storage system, effectively reduces the overall system cost, improves the system efficiency, reduces the system volume and improves the power density.

[0040] 2. The embodiment of the present invention adopts a three-port power control algorithm, deeply integrates the distribution network to develop a new generation of adaptive and flexible photovoltaic and storage integrated converter system for the distribution network, realizes energy injection and extraction with three-phase voltage tracking and flexible networking, fully guarantees photovoltaic power generation, flexibly realizes photovoltaic and storage DC networking, and solves the problem of time and space misalignment between distributed photovoltaic power generation and grid power consumption.

[0041] 3. Compared with the existing external AC-coupled energy storage photovoltaic storage solution architecture with two DC / AC energy storage energy conversion processes, the embodiments of the present invention reduce the AC / DC power conversion losses in the intermediate energy storage conversion process and significantly improve the photovoltaic power generation efficiency.

[0042] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic and energy storage integrated converter system with flexible storage configuration, characterized in that: It includes a photovoltaic array, a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface, and a DC-coupled energy storage converter connected in series with a DC busbar in the middle of the photovoltaic grid-connected inverter; The photovoltaic grid-connected inverter includes a DC / AC inverter and a plurality of DC / DC converters regulated by a maximum power point tracking system, wherein the connection ends of the first sides of the plurality of DC / DC converters are directly connected to the photovoltaic array interface respectively, and the connection ends of the second sides are all connected to the DC bus in the middle of the photovoltaic grid-connected inverter, the connection end of the first side of the DC / AC inverter is connected to the DC bus, and the second side is connected to the grid or the load; The photovoltaic array generates direct current, and a three-port power control algorithm is used at the direct current bus to control a flexible photovoltaic and storage integrated converter system for energy conversion.

2. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 1, characterized in that: The DC coupled energy storage converter comprises a bidirectional DC / DC converter and an energy storage unit, wherein a connection end on a first side of the bidirectional DC / DC converter is connected to a DC bus, and a connection end on a second side is connected to two connection ends of the energy storage unit.

3. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 2 is characterized in that: The method of using a three-port power control algorithm at the DC bus to control the flexible storage photovoltaic integrated converter system to perform energy conversion includes: When power generation is sufficient and the grid-connected electricity price is low, the DC power on the primary DC bus is converted to the energy storage unit through a bidirectional DC / DC converter. When power consumption is at peak and the grid-connected electricity price is high, the DC power in the energy storage unit is released to the DC bus through a bidirectional DC / DC converter, and then inverted into AC power by a DC / AC inverter to supply the grid or load.

4. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 2, characterized in that: The bidirectional DC / DC converter includes a first filter inductor, a first switch tube, and a second switch tube, wherein the second end of the second switch tube is connected to the first end of the first switch tube, and the first end of the second switch tube and the second end of the first switch tube are respectively connected to the two ends of the energy storage unit; the first end of the first filter inductor is connected to the common end of the first switch tube and the first switch tube, the second end of the filter inductor is connected to the positive power line of the DC bus, and the second end of the first switch tube is connected to the negative power line of the DC bus.

5. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 4, characterized in that: When the bidirectional DC / DC converter works in the forward direction, the current flows from the DC bus to the energy storage unit. The bidirectional DC / DC converter includes two switching modes: Mode 1: The first switch is turned on, the second switch is turned off, and the bidirectional DC / DC converter converts the photovoltaic power generation voltage U on the photovoltaic array and the DC bus in When added to the first filter inductor, the current of the first filter inductor increases linearly, and the first filter inductor stores energy; Mode 2: The first switch is turned off, the second switch is turned on, and the photovoltaic power generation voltage U on the photovoltaic array and DC bus is in Together with the first filter inductor, the energy storage unit is charged and stored.

6. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 4, characterized in that: When the bidirectional DC / DC converter works in reverse, the current flows from the energy storage unit to the DC bus. The bidirectional DC / DC converter includes two switching modes: Mode 1: The first switch tube is turned off, the second switch tube is turned on, and the current of the first filter inductor increases linearly; Mode 2: The first switch tube is turned on, the second switch tube is turned off, the current of the first filter inductor cannot change suddenly, and the energy in the first filter inductor is released to the DC bus.

7. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 2, characterized in that: The bidirectional DC / DC converter includes a second filter inductor, a third switch tube and a fourth switch tube, wherein the second end of the second filter inductor is connected to the first end of the fourth switch tube, and the second end of the fourth switch tube and the first end of the second filter inductor are respectively connected to the two ends of the energy storage unit; the second end of the third switch tube is connected to the common end of the fourth switch tube and the second filter inductor, the first end of the third switch tube is connected to the positive power line of the DC bus, and the second end of the fourth switch tube is connected to the negative power line of the DC bus.

8. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in claim 2, characterized in that: The energy storage unit includes a battery or a super capacitor.

9. The photovoltaic-storage integrated converter system with flexible storage configuration as claimed in any one of claims 1 to 8, characterized in that: The output of the photovoltaic grid-connected inverter supplies power to the grid or load via an industrial frequency isolation transformer.

10. The photovoltaic-storage integrated converter system with flexible storage configuration according to any one of claims 1 to 8, characterized in that: The output of the photovoltaic grid-connected inverter directly supplies power to the grid or load.

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