Multi-channel direct-current coupling optical storage converter system

Abstract

The invention provides a multi-channel direct-current coupling optical storage converter system, and relates to the technical field of optical storage systems. Under the condition that an existing photovoltaic product DC / DC and DC / AC two-stage grid-connected framework is not changed, a photovoltaic array interface is directly connected with the direct-current coupling energy storage converter, 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, the size of the system is reduced, and the power density is improved. Meanwhile, a three-port power control algorithm is adopted, a power distribution network is deeply fused to develop a new-generation adaptive multi-channel direct-current coupling optical storage converter system of the power distribution network, three-phase voltage follow-up energy injection and extraction and flexible networking are achieved, photovoltaic power generation is fully guaranteed, optical storage direct-current networking is flexibly achieved, and the power distribution network performance is improved. The problem that distributed photovoltaic power generation and power utilization space-time dislocation of a power grid cannot be fully reflected through value to form sticking points is solved, and a novel differentiated optical storage device capable of deeply fusing power distribution requirements is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic storage systems, and in particular to a multi-channel direct current coupled photovoltaic storage converter system. 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. Figure 1 As shown in the figure, it is mainly composed of photovoltaic array PV, maximum power point tracking system (MPPT, Maximum power point tracking), DC / AC inverter and power frequency isolation transformer, which is a typical string photovoltaic grid-connected. Figure 2 As shown, the absence of an industrial frequency isolation transformer simplifies the system structure, reduces costs and improves efficiency.

[0003] The existing solar storage system adopts Figure 3 The architecture shown in the figure connects a bidirectional AC / DC energy storage module to the output of a complete set of photovoltaic grid-connected inverters. The system assumes that the grid is in a relatively balanced state by default and operates in a balanced power output mode. When photovoltaic power generation is sufficient and the grid-connected electricity price is low, the system will store the electricity in the energy storage unit; and during peak hours and when the grid-connected electricity price is high, the energy in the energy storage unit will be released to supply power to the grid load.

[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 of the prior art, the present invention provides a multi-channel DC-coupled photovoltaic storage converter system, which solves the technical problem of low efficiency of the prior 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 multi-channel DC-coupled photovoltaic storage converter system, comprising a photovoltaic array, a DC-coupled energy storage converter directly connected to the photovoltaic array interface, and a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface; The photovoltaic array emits direct current, and a three-port power control algorithm is used at the photovoltaic array interface to control a multi-channel direct current coupled photovoltaic storage inverter system for energy conversion.

[0007] Preferably, the DC-coupled energy storage inverter includes a DC / DC coupling unit and an energy storage unit, wherein the DC / DC coupling unit includes a plurality of bidirectional DC / DC converters directly connected to the photovoltaic array interface respectively; the connection ports on the first side of the plurality of bidirectional DC / DC converters are respectively connected to a plurality of photovoltaic interfaces, and the connection ports on the second side are all connected to the DC bus on the energy storage side, and the energy storage unit is connected to the DC bus on the energy storage side.

[0008] Preferably, the three-port power control algorithm is used at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic storage converter system to perform energy conversion, including: When power generation is sufficient and the on-grid electricity price is low, the primary DC power is converted to the energy storage unit through the DC / DC coupling unit. When power consumption is at peak and the on-grid electricity price is high, the DC power of the energy storage unit is released to the photovoltaic interface through the DC / DC coupling unit. The DC power enters the photovoltaic grid-connected inverter to obtain AC power 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; Among them, 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 DC bus bars on the energy storage side; the first end of the filter inductor is connected to the common end of the first switch tube and the first switch tube, and the second end is connected to the positive pole of the photovoltaic interface, and the second end of the first switch tube is connected to the negative pole of the photovoltaic interface.

[0010] Preferably, when the bidirectional DC / DC converter works in the forward direction, the current flows from the photovoltaic interface side to the energy storage side, 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 primary photovoltaic power generation voltage U generated by the photovoltaic array to 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 array generates a primary photovoltaic power generation voltage U 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 side to the photovoltaic interface side, 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 photovoltaic interface.

[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 DC bus bars on the energy storage side; the second end of the third switch tube is connected to the common end of the fourth switch tube and the second inductor, the first end is connected to the positive pole of the photovoltaic interface, and the second end of the fourth switch tube is connected to the negative pole of the photovoltaic interface.

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

[0014] Preferably, the photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system.

[0015] Preferably, the output of the photovoltaic grid-connected inverter supplies power to the grid or load via an industrial frequency isolation transformer, or the output of the photovoltaic grid-connected inverter supplies power to the grid or load directly.

[0016] (III) Beneficial effects The present invention provides a multi-channel DC-coupled photovoltaic storage converter system. Compared with the prior art, it has the following beneficial effects: The embodiment of the present invention realizes direct connection of the photovoltaic array interface to the DC-coupled energy storage converter without changing the existing DC / DC and DC / AC two-level grid-connected architecture of photovoltaic products, thus simplifying the structure of the photovoltaic storage system, effectively reducing the overall system cost, improving system efficiency, reducing system volume, and increasing power density. At the same time, a three-port power control algorithm is adopted to deeply integrate the distribution network to develop a new generation of multi-channel DC-coupled photovoltaic storage converter system with adaptive distribution network, realize energy injection and extraction with three-phase voltage tracking and flexible networking, fully guarantee photovoltaic power generation, flexibly realize photovoltaic storage DC networking, solve the problem of the card point formed by the time and space misalignment between distributed photovoltaic power generation and power grid power consumption, and cannot fully reflect the value, and obtain a new type of differentiated photovoltaic storage that can deeply integrate the distribution demand. 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 1This 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 It is a structural diagram of a multi-channel DC-coupled photovoltaic storage 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 multi-channel DC-coupled photovoltaic storage inverter system, realize the direct connection of the photovoltaic array interface to the DC-coupled energy storage inverter, simplify the structure of the photovoltaic storage system, effectively reduce the overall system cost, improve system efficiency, reduce system volume and increase 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: Faced with the explosive growth of installed capacity, the development of distributed photovoltaics faces two prominent contradictions: the grid carrying capacity and the reform of the electricity market. The distribution network has increasingly become the "main battlefield" for building a new power system, and is undergoing a transformation from the basic function of receiving and distributing electric energy to an intelligent power carrier that deeply integrates multiple elements such as source, network, load, and storage and realizes efficient interactive coupling with the transmission network.

[0023] 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.

[0024] The existing solar storage system adopts 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, and the grid is assumed to be relatively balanced. It works in a balanced power output mode. When photovoltaic power generation is sufficient and the grid-connected electricity price is low, the electricity is stored in the energy storage unit; 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 efficiency of this photovoltaic storage system is low, the size is large, and the cost is high.

[0025] To solve the above problems, the embodiment of the present invention proposes a multi-channel DC-coupled photovoltaic storage 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 inability to fully reflect the value of the time and space misalignment between distributed photovoltaic power generation and grid power consumption, and obtains a new type of differentiated photovoltaic storage that can deeply integrate power distribution needs.

[0026] 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.

[0027] The embodiment of the present invention provides a multi-channel DC-coupled photovoltaic storage converter system, such as Figure 4 As shown, it includes a photovoltaic array, a DC-coupled energy storage converter directly connected to the photovoltaic array interface, and a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface; The photovoltaic array emits direct current, and a three-port power control algorithm is used at the photovoltaic array interface to control a multi-channel direct current coupled photovoltaic storage inverter system for energy conversion.

[0028] 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.

[0029] Combine the following Figure 4 , Figure 5 and Figure 6 The multi-channel DC-coupled photovoltaic storage converter system is described in detail: In the specific implementation process, the DC-coupled energy storage converter includes a DC / DC coupling unit and an energy storage unit, wherein the DC / DC coupling unit includes a number of bidirectional DC / DC converters directly connected to the photovoltaic array interface. The photovoltaic interface ends of the bidirectional DC / DC converters are respectively connected to the photovoltaic interfaces, the energy storage interface ends of the bidirectional DC / DC converters are all connected to the DC bus on the energy storage side, and the energy storage unit is connected to the DC bus on the energy storage side. The DC-coupled energy storage converter can realize the bidirectional flow of energy in different working modes, thereby realizing the charging or discharging of the energy storage unit. The DC / DC coupling unit in the DC-coupled energy storage converter can select the BUCK circuit or the BOOST circuit.

[0030] The photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system.

[0031] A multi-channel DC-coupled photovoltaic storage converter system according to an embodiment of the present invention 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 one DC / DC conversion and then enters the DC / AC inverter. For the AC-coupled energy storage conversion process, when the power generation is sufficient and the on-grid electricity price is low, the AC power is stored in the energy storage unit through AC / DC conversion. When the power consumption is peak and the on-grid electricity price is high, the DC power is released through DC / AC conversion to supply the grid load. This is the four conversions of the existing solution.

[0032] The scheme of the embodiment of the present invention is: first, the distributed photovoltaic generates direct current, and the three-port power control algorithm is used at the photovoltaic array interface to start the judgment work. For the DC coupling energy storage conversion process, when the power generation is sufficient and the on-grid electricity price is low, the DC power is converted to the energy storage unit through the DC / DC coupling unit. When the power consumption is at a peak and the on-grid electricity price is high, the DC power is released to the photovoltaic interface through the DC / DC coupling unit. Finally, the DC power enters the photovoltaic grid-connected inverter composed of MPPT and DC / AC inverter to perform a DC / DC energy conversion and a DC / AC energy conversion to obtain AC power to supply the grid load. This is the four energy conversions of the embodiment of the present invention. Under the condition of distributed photovoltaic power generation in the same external environment, the two DC coupling energy storage conversion processes of the embodiment of the present invention are both DC / DC energy conversions, and the photovoltaic array interface is directly connected to the energy storage unit without changing the existing photovoltaic grid-connected architecture, so as to flexibly realize the photovoltaic storage DC networking. Compared with the two DC / AC energy storage energy conversion processes of the existing photovoltaic storage system architecture, the embodiments of the present invention significantly improve the photovoltaic storage power generation efficiency, reduce the AC / DC power conversion loss in the intermediate energy storage conversion process, and complete the energy conversion directly at the photovoltaic array interface, thereby simplifying the structure of the photovoltaic storage system, reducing the system volume and improving the power density.

[0033] In addition, it should be noted that if the multi-channel DC-coupled photovoltaic storage inverter system proposed in the embodiment of the present invention is used in an isolated working condition containing 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 supercapacitors, etc. At the same time, the bidirectional DC / DC converter in the DC / DC coupling unit 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 two DC bus bars on the energy storage side (at Figure 5In order to facilitate understanding, 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. In fact, the two connection ends of the plurality of bidirectional DC / DC converters are connected to the two DC buses on the energy storage side. Figure 6 Similarly); 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, and the second end is connected to the positive pole of the photovoltaic interface. The second end of the first switch tube T1 is connected to the negative pole of the photovoltaic interface. The forward direction of this circuit topology is defined as the flow from the photovoltaic interface to the energy storage unit; it can work in both directions, and the flow from the energy storage unit to the photovoltaic interface is the BUCK circuit.

[0035] Figure 6 The 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 DC bus bars on the energy storage side; the second end of the third switch tube T3 is connected to the common end of the fourth switch tube T4 and the second inductor L2, the first end is connected to the positive pole of the photovoltaic interface, and the second end of the fourth switch tube T4 is connected to the negative pole of the photovoltaic interface.

[0036] Below Figure 5 The multi-channel DC-coupled photovoltaic storage converter system shown in the figure describes the three-port power control algorithm in detail: The three-port power control algorithm determines the energy flow direction of the photovoltaic array interface. When the distributed photovoltaic power generation is sufficient and the grid-connected electricity price is low, the DC-coupled energy storage converter works in the forward direction. At this time, it is a BOOST converter with two switching modes: Mode 1, switch tube T1 is turned on, switch tube T2 is turned off, and the converter converts the primary photovoltaic power generation voltage U generated by the photovoltaic array into in Added to the boost inductor L1, the boost inductor current increases linearly, and the inductor L1 stores energy; Mode 2, the switch tube T1 is turned off, the switch tube T2 is turned on, and the photovoltaic array generates a primary photovoltaic power generation voltage U in Together with the boost inductor, the energy storage unit is charged and stored. The two working modes store the abundant photovoltaic power generation and the electricity with the market 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 direction of the photovoltaic array interface. 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, it 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 photovoltaic array interface that is about to enter the MPPT module. Its two working modes are: Mode 1, switch tube T1 is turned off, switch tube T2 is turned on, and the current of the filter inductor L1 increases linearly; Mode 2, switch tube T1 is turned on, switch tube T2 is turned off, the current of the filter inductor L1 cannot change suddenly, and the energy in the inductor is released to the photovoltaic interface. 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] The multi-channel DC-coupled photovoltaic storage converter system of the embodiment of the present invention adopts a DC bus architecture and a multi-port collaborative control mechanism. The system uses a common DC bus as an energy hub, the photovoltaic array is connected through a bidirectional Buck / Boost converter, the energy storage unit is connected through an LLC resonant converter, and the grid-connected side uses a three-level NPC converter to realize DC-AC conversion. In the power transmission path, the MPPT control on the photovoltaic side realizes maximum power point tracking by adjusting the duty cycle of the Boost converter, while maintaining bus voltage stability. The energy storage side realizes rapid switching of the charging and discharging mode through a current-type bidirectional DC-DC converter, and the grid-connected side adopts vector control based on a synchronous rotating coordinate system to realize active and reactive decoupling control by adjusting the dq axis current component. The voltage following mechanism introduced by the system is essentially a grid synchronization technology based on an improved phase-locked loop. The orthogonal signal generator constructed by a second-order generalized integrator, combined with a software phase-locked algorithm, can realize sub-millisecond phase tracking. When multiple channels are operated in parallel, the virtual impedance method is introduced to realize current sharing control, and the output impedance characteristics of each module are accurately matched to ensure the circulation suppression effect. The three-port power balancing algorithm establishes constraint equations that include photovoltaic output, energy storage SOC and grid demand. This multi-time scale control architecture ensures stable operation of the system under all operating conditions.

[0039] In summary, compared with the prior art, the present invention has the following beneficial effects: 1. The embodiment of the present invention realizes direct connection of the photovoltaic array interface to the DC-coupled energy storage converter without changing the existing DC / DC and DC / AC two-level grid-connected architecture of photovoltaic products, thus simplifying the structure of the photovoltaic storage system. The flexible configuration of multi-channel DC-coupled energy storage can effectively reduce the overall system cost, improve device efficiency, reduce system volume, and increase power density. At the same time, a three-port power control algorithm is adopted to deeply integrate the distribution network to develop a new generation of multi-channel DC-coupled photovoltaic storage converter system with adaptive distribution network, realize energy injection and extraction with three-phase voltage tracking and flexible networking, fully guarantee photovoltaic power generation, flexibly realize photovoltaic storage DC networking, and solve the problem of time and space misalignment between distributed photovoltaic power generation and grid power consumption.

[0040] 2. 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.

[0041] 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.

[0042] 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 multi-channel DC-coupled photovoltaic storage converter system, characterized in that: It includes a photovoltaic array, a DC-coupled energy storage converter directly connected to the photovoltaic array interface, and a photovoltaic grid-connected inverter directly connected to the photovoltaic array interface; the DC-coupled energy storage converter includes a DC / DC coupling unit and an energy storage unit; The photovoltaic array emits direct current, and a three-port power control algorithm is used at the photovoltaic array interface to control a multi-channel direct current coupled photovoltaic storage inverter system for energy conversion, including: When power generation is sufficient and the on-grid electricity price is low, the primary DC power is converted to the energy storage unit through the DC / DC coupling unit. When power consumption is at peak and the on-grid electricity price is high, the DC power of the energy storage unit is released to the photovoltaic interface through the DC / DC coupling unit. The DC power enters the photovoltaic grid-connected inverter to obtain AC power to supply the grid or load.

2. The multi-channel DC-coupled photovoltaic storage converter system according to claim 1, characterized in that: The DC / DC coupling unit includes a plurality of bidirectional DC / DC converters directly connected to the photovoltaic array interface; the connection ports on the first side of the plurality of bidirectional DC / DC converters are respectively connected to the plurality of photovoltaic interfaces, and the connection ports on the second side are all connected to the DC bus on the energy storage side, and the energy storage unit is connected to the DC bus on the energy storage side.

3. The multi-channel DC-coupled photovoltaic storage converter system according to claim 2, characterized in that: The bidirectional DC / DC converter includes a first filter inductor, a first switch tube and a second switch tube; Among them, 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 DC bus bars on the energy storage side; the first end of the filter inductor is connected to the common end of the first switch tube and the first switch tube, and the second end is connected to the positive pole of the photovoltaic interface, and the second end of the first switch tube is connected to the negative pole of the photovoltaic interface.

4. The multi-channel DC-coupled photovoltaic storage converter system according to claim 3, characterized in that: When the bidirectional DC / DC converter works in the forward direction, the current flows from the photovoltaic interface side to the energy storage side. 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 primary photovoltaic power generation voltage U generated by the photovoltaic array to 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 array generates a primary photovoltaic power generation voltage U in Together with the first filter inductor, the energy storage unit is charged and stored.

5. The multi-channel DC-coupled photovoltaic storage converter system according to claim 3, characterized in that: When the bidirectional DC / DC converter works in reverse, the current flows from the energy storage side to the photovoltaic interface side. 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 photovoltaic interface.

6. The multi-channel DC-coupled photovoltaic storage converter system according to 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 two DC bus bars on the energy storage side; the second end of the third switch tube is connected to the common end of the fourth switch tube and the second inductor, the first end is connected to the positive pole of the photovoltaic interface, and the second end of the fourth switch tube is connected to the negative pole of the photovoltaic interface.

7. The multi-channel DC-coupled photovoltaic storage converter system according to claim 2, characterized in that: The energy storage unit includes a battery or a super capacitor.

8. The multi-channel DC-coupled photovoltaic storage converter system according to any one of claims 1 to 7, characterized in that: The photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system.

9. The multi-channel DC-coupled photovoltaic storage converter system according to any one of claims 1 to 7, characterized in that: The output of the photovoltaic grid-connected inverter supplies power to the grid or load via an industrial frequency isolation transformer, or the output of the photovoltaic grid-connected inverter supplies power to the grid or load directly.

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