Multi-channel direct current coupled optical storage inverter system

Abstract

The application provides a multi-channel direct-current coupling light storage converter system and relates to the technical field of light storage systems.The application directly connects a direct-current coupling energy storage converter to a photovoltaic array interface without changing the existing photovoltaic product DC / DC and DC / AC two-stage grid-connected architecture, simplifies the structure of the light storage system, effectively reduces the overall cost of the system, improves the system efficiency, reduces the system volume and improves the power density.Meanwhile, a three-port power control algorithm is adopted to deeply integrate a power distribution network to develop a new generation of multi-channel direct-current coupling light storage converter system with power distribution network adaptability, realize energy injection and extraction with three-phase voltage follow-up and flexible networking, fully guarantee photovoltaic power generation, flexibly realize light storage direct-current networking and solve the problem of the card point formed by the time and space misalignment of distributed photovoltaic power generation and power grid power consumption which cannot be fully reflected through value, so a new differentiated light storage which can deeply integrate power distribution demand is obtained.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic energy storage system technology, and specifically to a multi-channel DC-coupled photovoltaic energy storage converter system. Background Technology

[0002] The photovoltaic-storage system is designed based on a distributed photovoltaic grid-connected system. Existing distributed photovoltaic grid-connected systems can be divided into isolated and non-isolated types based on whether they have a power frequency isolation transformer. An isolated type architecture diagram is shown below. Figure 1 As shown, it mainly consists of a photovoltaic array (PV), a maximum power point tracking (MPPT) system, a DC / AC inverter, and a power frequency isolation transformer, belonging to a typical string photovoltaic grid-connected system. A non-isolated architecture diagram is shown below. Figure 2 As shown, the absence of a power frequency isolation transformer simplifies the system structure, reduces costs, and improves efficiency.

[0003] Existing photovoltaic energy storage systems use, for example, Figure 3 The architecture shown connects a bidirectional AC / DC energy storage module to the output of a complete photovoltaic grid-connected inverter. The system assumes the grid is in a relatively balanced state and operates in a balanced power output mode. When photovoltaic power generation is sufficient and the grid-connected electricity price is low, the system stores electrical energy in the energy storage unit; during peak electricity consumption periods and when the grid-connected electricity price is high, the system releases the electrical energy from the storage unit to supply power to the grid load.

[0004] However, this type of photovoltaic-storage system, which connects a bidirectional AC / DC energy storage module to the output of a complete photovoltaic grid-connected inverter, is inefficient. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a multi-channel DC-coupled photovoltaic-storage converter system, which solves the technical problem of low efficiency in existing photovoltaic-storage systems.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a multi-channel DC-coupled photovoltaic-storage converter system, including 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;

[0010] The photovoltaic array generates direct current, and a three-port power control algorithm is used at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic-storage converter system for energy conversion.

[0011] Preferably, the DC-coupled energy storage converter includes a DC / DC coupling unit and an energy storage unit. The DC / DC coupling unit includes several bidirectional DC / DC converters that are directly connected to the photovoltaic array interface. The first-side connection ports of the several bidirectional DC / DC converters are respectively connected to several photovoltaic interfaces, and the second-side connection ports are all connected to the DC bus on the energy storage side. The energy storage unit is connected to the DC bus on the energy storage side.

[0012] Preferably, the step of using a three-port power control algorithm at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic-storage converter system for energy conversion includes:

[0013] When power generation is abundant and the grid-connected electricity price is low, the primary DC power is converted to the energy storage unit via the DC / DC coupling unit. When electricity consumption is at its peak and the grid-connected electricity price is high, the DC power of the energy storage unit is released to the photovoltaic interface via the DC / DC coupling unit. The DC power then enters the photovoltaic grid-connected inverter to obtain AC power to supply the grid or load.

[0014] Preferably, the bidirectional DC / DC converter includes a first filter inductor, a first switching transistor, and a second switching transistor;

[0015] The second terminal of the second switch is connected to the first terminal of the first switch, and the first terminal of the second switch and the second terminal of the first switch are respectively connected to two DC buses on the energy storage side; the first terminal of the filter inductor is connected to the common terminal of the first switch and the first switch, the second terminal is connected to the positive terminal of the photovoltaic interface, and the second terminal of the first switch is connected to the negative terminal of the photovoltaic interface.

[0016] Preferably, when the bidirectional DC / DC converter is operating 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:

[0017] Mode 1: The first switch is on, the second switch is off, and the bidirectional DC / DC converter converts the primary photovoltaic power generation voltage U generated by the photovoltaic array into voltage U. in When applied to the first filter inductor, the current in the first filter inductor increases linearly, and the first filter inductor stores energy.

[0018] Mode 2: The first switch is off, the second switch is on, and the photovoltaic array generates a primary photovoltaic power generation voltage U. in Together with the first filter inductor, it charges and stores energy in the energy storage unit.

[0019] Preferably, when the bidirectional DC / DC converter operates 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:

[0020] Mode 1: The first switch is off, the second switch is on, and the current of the first filter inductor increases linearly.

[0021] Mode 2: The first switch is turned on, the second switch is turned off, the current of the first filter inductor cannot change abruptly, and the energy in the first filter inductor is released to the photovoltaic interface.

[0022] Preferably, the bidirectional DC / DC converter includes a second filter inductor, a third switch, and a fourth switch. The second end of the second filter inductor is connected to the first end of the fourth switch, and the second end of the fourth switch and the first end of the second filter inductor are respectively connected to two DC buses on the energy storage side. The second end of the third switch is connected to the common terminal of the fourth switch and the second inductor, and the first end is connected to the positive terminal of the photovoltaic interface. The second end of the fourth switch is connected to the negative terminal of the photovoltaic interface.

[0023] Preferably, the energy storage unit includes a battery or a supercapacitor.

[0024] Preferably, the photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system.

[0025] Preferably, the output of the photovoltaic grid-connected inverter supplies power to the grid or load via a power frequency isolation transformer; alternatively, the output of the photovoltaic grid-connected inverter supplies power directly to the grid or load.

[0026] (III) Beneficial Effects

[0027] This invention provides a multi-channel DC-coupled photovoltaic-storage converter system. Compared with the prior art, it has the following advantages:

[0028] This invention, without altering the existing two-stage DC / DC and DC / AC grid-connected architecture of photovoltaic products, enables direct connection of the photovoltaic array interface to a DC-coupled energy storage converter. This simplifies the structure of the photovoltaic-energy storage system, effectively reduces overall system cost, improves system efficiency, reduces system size, and increases power density. Simultaneously, by employing a three-port power control algorithm, it deeply integrates with the distribution network to develop a new generation of multi-channel DC-coupled photovoltaic-energy storage converter system with distribution network adaptability. This achieves three-phase voltage-responsive energy injection and extraction, enabling flexible grid connection and fully guaranteeing photovoltaic power generation. It flexibly realizes DC grid connection between photovoltaic and energy storage, resolving the bottleneck problem caused by the temporal and spatial misalignment between distributed photovoltaic power generation and grid power consumption, thus resulting in a novel differentiated photovoltaic-energy storage system that can deeply integrate with distribution needs. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a diagram of the architecture of an existing isolated distributed photovoltaic grid-connected system;

[0031] Figure 2 This is a diagram of the architecture of an existing non-isolated distributed photovoltaic grid-connected system;

[0032] Figure 3 A diagram of the existing photovoltaic-storage system architecture;

[0033] Figure 4 This is a schematic diagram of the multi-channel DC-coupled photovoltaic-storage converter system according to an embodiment of the present invention;

[0034] Figure 5 for Figure 4 The first example of the architecture diagram shown;

[0035] Figure 6 for Figure 4 The second example of the architecture diagram shown. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that, for ease of description, the IGBT is used to represent the controllable (on and off) switching transistor in the embodiments of this invention, but the switching transistor in this invention is not limited to IGBT. An IGBT is used as an example for explanation. The first terminal of the IGBT refers to the collector, the second terminal to the emitter, and the control terminal to the gate. A drive control signal is applied to the control terminal of each switching transistor in the embodiments of this invention. For simplicity, this will not be elaborated further. The power switching transistor in the embodiments of this invention can also be implemented using other controllable switching transistor devices besides IGBT, such as MOSFET. Meanwhile, to ensure the normal operation of each switching device in the embodiments of this invention, a freewheeling diode needs to be connected in parallel with each switching device. The parallel direction of the freewheeling diode is related to the type of switching device, and those skilled in the art can set it according to the type of switching device; it is not limited here. Unless otherwise specified, the switching device implicitly includes a freewheeling diode, which will be indicated in this embodiment in special cases.

[0038] This application provides a multi-channel DC-coupled photovoltaic-storage converter system, which solves the technical problem of low efficiency in existing photovoltaic-storage systems. It enables direct connection of the photovoltaic array interface to the DC-coupled energy storage converter, simplifies the structure of the photovoltaic-storage system, effectively reduces the overall system cost, improves system efficiency, reduces system size, and increases power density.

[0039] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0040] Faced with the explosive growth in installed capacity, the development of distributed photovoltaic power faces two prominent contradictions: grid carrying capacity and power market reform. The distribution network is increasingly becoming the "main battlefield" for building a new power system, and is undergoing a transformation from its basic function of receiving and distributing electrical energy to a smart power carrier that deeply integrates multiple elements such as power sources, grids, loads, and storage, and achieves efficient interaction and coupling with the transmission network.

[0041] Existing distributed photovoltaic grid-connected systems can be divided into isolated and non-isolated types based on whether they have a power frequency isolation transformer. An isolated type architecture diagram is shown below. Figure 1 As shown, it mainly consists of a photovoltaic array (PV), a maximum power point tracking (MPPT) system (the MPPT system continuously monitors the current and voltage changes of the PV array and adjusts the duty cycle of the PWM drive signal of the DC / DC converter accordingly), a DC / AC inverter, and a power frequency isolation transformer. It is a typical string-type grid-connected photovoltaic system. A non-isolated architecture diagram is shown below. Figure 2 As shown, the absence of a power frequency isolation transformer simplifies the system structure, reduces costs, and improves efficiency.

[0042] Existing photovoltaic energy storage systems use, for example, Figure 3The architecture shown is a complete photovoltaic grid-connected inverter whose output is connected to a bidirectional AC / DC energy storage module. It assumes that the grid is relatively balanced and operates in a balanced power output mode. When photovoltaic power generation is abundant and the grid-connected electricity price is low, the energy is stored in the energy storage unit; when the electricity consumption is high and the grid-connected electricity price is high, the energy is released to supply the grid load. However, this photovoltaic-energy storage system has low efficiency, large size, and high cost.

[0043] To address the aforementioned issues, this invention proposes a multi-channel DC-coupled photovoltaic-storage converter system. This system simplifies the structure of the photovoltaic-storage system, effectively reducing overall system cost, improving device efficiency, reducing system size, and increasing power density. Simultaneously, this system resolves the bottleneck issue caused by the temporal and spatial mismatch between distributed photovoltaic power generation and grid power consumption, preventing the full realization of its value. This results in a novel, differentiated photovoltaic-storage system that can deeply integrate with power distribution needs.

[0044] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0045] This 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;

[0046] The photovoltaic array generates direct current, and a three-port power control algorithm is used at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic-storage converter system for energy conversion.

[0047] It should be noted that, Figure 4 The system architecture shown is non-isolated, but this does not mean that the present invention is only applicable to non-isolated systems. The embodiments of the present invention are also applicable to isolated distributed photovoltaic grid-connected systems, ensuring that the system's absorption capacity is not limited by the capacity of the power frequency isolation transformer. In specific implementation, the AC current output by the photovoltaic grid-connected inverter is directed to single / three-phase loads, small industrial / commercial / residential three-phase photovoltaic systems, and the power grid.

[0048] The following is combined with Figure 4 , Figure 5 and Figure 6 A detailed description of the multi-channel DC-coupled photovoltaic-storage converter system is provided:

[0049] In practical implementation, the DC-coupled energy storage converter includes a DC / DC coupling unit and an energy storage unit. The DC / DC coupling unit comprises several bidirectional DC / DC converters directly connected to the photovoltaic array interface. The photovoltaic interface terminals of these bidirectional DC / DC converters are connected to several photovoltaic interfaces, and the energy storage interface terminals of these converters are connected to the DC bus on the energy storage side. The energy storage unit is connected to the DC bus on the energy storage side. The DC-coupled energy storage converter can achieve bidirectional energy flow in different operating modes, thereby enabling the energy storage unit to charge or discharge. The DC / DC coupling unit in the DC-coupled energy storage converter can be either a BUCK circuit or a BOOST circuit.

[0050] A photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system.

[0051] The multi-channel DC-coupled photovoltaic energy storage converter system of this invention and Figure 3 The existing photovoltaic-storage system architectures shown both involve four energy conversions, but there is a significant difference in energy loss between the two:

[0052] The existing scheme involves distributed photovoltaic power generating DC power, which is then converted into AC power by a DC / DC converter. For the AC-coupled energy storage conversion process, when power generation is sufficient and the grid electricity price is low, the AC power is converted into AC power and stored in the energy storage unit. When the electricity consumption is high and the grid electricity price is high, the DC power is converted into DC power and released to supply the grid load. This is the four-stage conversion in the existing scheme.

[0053] The solution of this invention is as follows: First, distributed photovoltaic (PV) power generates DC power. At the PV array interface, a three-port power control algorithm is used to determine the operation. For the DC-coupled energy storage conversion process, when power generation is sufficient and the grid-connected electricity price is low, the primary DC power is converted to the energy storage unit via a DC / DC coupling unit. When electricity consumption is at its peak and the grid-connected electricity price is high, the DC power is released to the PV interface via the DC / DC coupling unit. Finally, the DC power enters the PV grid-connected inverter composed of an MPPT and a DC / AC inverter for one DC / DC energy conversion and one DC / AC energy conversion to obtain AC power to supply the grid load. This constitutes the four energy conversions in this invention. Under the same external environment for distributed PV power generation, both DC-coupled energy storage conversion processes in this invention are DC / DC energy conversions, and without changing the existing PV grid-connected architecture, the PV array interface is directly connected to the energy storage unit, flexibly realizing PV-storage DC grid connection. Compared with the existing photovoltaic-storage system architecture which involves two DC / AC energy conversion processes, the embodiments of the present invention significantly improve the photovoltaic-storage power generation efficiency, reduce the AC / DC power conversion losses in the intermediate energy storage conversion process, and complete the energy conversion directly at the photovoltaic array interface, simplifying the structure of the photovoltaic-storage system, reducing the system volume, and increasing the power density.

[0054] In addition, it should be noted that if the multi-channel DC-coupled photovoltaic-storage converter system proposed in this embodiment of the invention is used in an isolated operating condition containing a power 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 power frequency isolation transformer. When distributed photovoltaic power generation is sufficient and the grid-connected electricity price is low, the energy of the new energy can be stored in the energy storage unit through a three-port power control algorithm. When the electricity consumption is at its peak and the grid-connected electricity price is high, the stored energy can be fed into the grid to supply users, thus achieving high cost performance.

[0055] In practical implementation, the energy storage unit in the DC-coupled energy storage converter can be various batteries or supercapacitors, etc. Meanwhile, the bidirectional DC / DC converter in the DC / DC coupling unit can take many forms, as long as it can achieve bidirectional energy flow in different operating modes and can select either a BUCK circuit or a BOOST circuit. This invention provides two specific bidirectional DC / DC converters, such as... Figure 5 and Figure 6 As shown, where, Figure 5 The bidirectional DC / DC converter in the circuit includes a first filter inductor L1 and two switching transistors T1 and T2 forming a chopper circuit topology. The second terminal of the second switching transistor T2 is connected to the first terminal of the first switching transistor T1. The first terminals of the second switching transistor T2 and the first switching transistor T1 are respectively connected to two DC buses on the energy storage side (in...). Figure 5In this diagram, for ease of understanding, the first terminal of the second switch T2 and the second terminal of the first switch T1 are respectively connected to the two ends of the energy storage unit. In reality, this means that the two connection terminals of multiple 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 terminal of the first switching transistors T1 and T2, and the second end is connected to the positive terminal of the photovoltaic interface. The second end of the first switching transistor T1 is connected to the negative terminal of the photovoltaic interface. The positive 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.

[0056] Figure 6 The bidirectional DC / DC converter in the circuit includes a chopper circuit topology consisting of a second filter inductor L2 and two switching transistors T3 and T4. The second terminal of the second filter inductor L2 is connected to the first terminal of the fourth switching transistor T4. The second terminal of the fourth switching transistor T4 and the first terminal of the second filter inductor L2 are respectively connected to two DC buses on the energy storage side. The second terminal of the third switching transistor T3 is connected to the common terminal of the fourth switching transistor T4 and the second inductor L2, and the first terminal is connected to the positive terminal of the photovoltaic interface. The second terminal of the fourth switching transistor T4 is connected to the negative terminal of the photovoltaic interface.

[0057] The following is based on Figure 5 The multi-channel DC-coupled photovoltaic-storage converter system shown here provides a detailed description of the three-port power control algorithm:

[0058] The three-port power control algorithm determines the energy flow direction of the photovoltaic array interface. When distributed photovoltaic power generation is abundant and the grid-connected electricity price is low, the DC-coupled energy storage converter operates in the forward direction, which is a BOOST converter with two switching modes: Mode 1, where switch T1 is on and switch T2 is off, and the converter converts the primary photovoltaic power generation voltage U generated by the photovoltaic array into a BOOST converter. in When applied to the boost inductor L1, the current in the boost inductor increases linearly, and inductor L1 stores energy; in mode 2, switch T1 is off, switch T2 is on, and the primary photovoltaic power generation voltage U generated by the photovoltaic array... in Together with the boost inductor, it charges and stores energy in the energy storage unit. The two operating modes enable the storage of abundant photovoltaic power generation and electricity at off-peak market prices, thus avoiding the two major contradictions of insufficient grid capacity in photovoltaic "red zones" and abundant distributed photovoltaic power generation but low grid-connected electricity prices at the same time.

[0059] The three-port power control algorithm determines the energy flow direction at the photovoltaic array interface. When grid electricity consumption is at its peak and the grid-connected electricity price is high, the DC-coupled energy storage converter operates in reverse, functioning as a BUCK converter. Switches T1 and T2 form a chopper circuit to modulate the voltage of the energy storage unit, outputting it to the photovoltaic array interface before it enters the MPPT module. Its two operating modes are: Mode 1, switch T1 is off, switch T2 is on, and the current in the filter inductor L1 increases linearly; Mode 2, switch T1 is on, switch T2 is off, the current in the filter inductor L1 cannot change abruptly, and the energy in the inductor is released to the photovoltaic interface. These two operating modes allow the energy stored in the energy storage unit at the "valley price" of the market electricity price to be released during the peak electricity consumption period when the grid-connected electricity price is high, thus achieving a high-profit "peak-valley arbitrage" effect.

[0060] The multi-channel DC-coupled photovoltaic-storage converter system of this invention adopts a DC bus architecture and a multi-port collaborative control mechanism. The system uses a common DC bus as the energy hub. The photovoltaic array is connected via a bidirectional Buck / Boost converter, and the energy storage unit is connected via an LLC resonant converter. A three-level NPC converter is used on the grid-connected side to achieve DC-AC conversion. On the power transmission path, the MPPT control on the photovoltaic side achieves maximum power point tracking by adjusting the duty cycle of the Boost converter, while maintaining stable bus voltage. On the energy storage side, a current-driven bidirectional DC-DC converter enables rapid switching between charging and discharging modes. The grid-connected side employs vector control based on a synchronous rotating coordinate system, achieving active and reactive power decoupling control by adjusting the dq-axis current components. The voltage servo mechanism introduced by the system is essentially a grid synchronization technology based on an improved phase-locked loop. An orthogonal signal generator constructed using a second-order generalized integrator, combined with a software phase-locked loop algorithm, can achieve sub-millisecond phase tracking. During multi-channel parallel operation, current sharing control is achieved by introducing a virtual impedance method, and the output impedance characteristics of each module are precisely matched to ensure circulating current suppression. The three-port power balance algorithm establishes constraint equations that include photovoltaic output, energy storage SOC, and grid demand. This multi-timescale control architecture ensures stable system operation under all operating conditions.

[0061] In summary, compared with existing technologies, it has the following beneficial effects:

[0062] 1. This invention, without altering the existing DC / DC and DC / AC two-level grid-connected architecture of photovoltaic products, enables direct connection of the photovoltaic array interface to a DC-coupled energy storage converter. This simplifies the structure of the photovoltaic-energy storage system. The flexible configuration of multi-channel DC-coupled energy storage effectively reduces overall system cost, improves device efficiency, reduces system size, and increases power density. Simultaneously, by employing a three-port power control algorithm and deeply integrating with the distribution network, a new generation of multi-channel DC-coupled photovoltaic-energy storage converter system with distribution network adaptability is developed. This enables three-phase voltage-responsive energy injection and extraction, and flexible grid connection, fully guaranteeing photovoltaic power generation and flexibly realizing DC grid connection between photovoltaic and energy storage. This solves the problem of temporal and spatial misalignment between distributed photovoltaic power generation and grid power consumption.

[0063] 2. Compared with the existing photovoltaic energy storage scheme architecture with external AC coupled energy storage and two DC / AC energy conversion processes, the embodiment of the present invention reduces the AC / DC power conversion loss in the intermediate energy storage conversion process, and significantly improves the photovoltaic energy storage power generation efficiency.

[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate 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 generates direct current (DC), and a three-port power control algorithm is used at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic-storage converter system for energy conversion, including: When power generation is abundant and the grid-connected electricity price is low, the primary DC power is converted to the energy storage unit through the DC / DC coupling unit. When the electricity consumption is at its peak and the grid-connected 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. The DC / DC coupling unit includes several bidirectional DC / DC converters that are directly connected to the photovoltaic array interface. The first-side connection ports of each bidirectional DC / DC converter are connected to several photovoltaic interfaces, and the second-side connection ports are all connected to the DC bus on the energy storage side. The energy storage unit is connected to the DC bus on the energy storage side. Each bidirectional DC / DC converter includes a first filter inductor, a first switching transistor, and a second switching transistor. The second end of the second switching transistor is connected to the first end of the first switching transistor, and the first and second ends of the second switching transistor are respectively connected to two DC buses on the energy storage side. The first end of the filter inductor is connected to the common terminal of the first and second switching transistors, and the second end is connected to the positive terminal of the photovoltaic interface. The second end of the first switching transistor is connected to the negative terminal of the photovoltaic interface. The photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system. This system enables direct connection of the photovoltaic array interface to the DC-coupled energy storage converter without changing the existing two-stage grid-connected architecture of the photovoltaic products (DC / DC and DC / AC). The multi-channel DC-coupled photovoltaic-storage converter system adopts a DC bus architecture and a multi-port collaborative control mechanism. Using a common DC bus as the energy hub, the photovoltaic array is connected via a bidirectional DC / DC converter, and the energy storage unit is connected via an LLC resonant converter. On the grid-connected side, a three-level NPC converter is used to achieve DC-AC conversion. In the power transmission path, MPPT control on the photovoltaic side achieves maximum power point tracking by adjusting the duty cycle of the DC / DC converter, while maintaining stable bus voltage. On the energy storage side, a current-driven bidirectional DC-DC converter enables rapid switching between charging and discharging modes. The grid-connected side uses a synchronous rotating coordinate system. The system employs vector control to achieve decoupling control of active and reactive power by adjusting the dq-axis current components. The voltage servo mechanism introduced by the system is essentially a grid synchronization technology based on an improved phase-locked loop. It uses an orthogonal signal generator constructed with a second-order generalized integrator, combined with a software phase-locked algorithm, to achieve sub-millisecond phase tracking. When multiple channels are connected in parallel, current sharing control is achieved by introducing a virtual impedance method. The output impedance characteristics of each module are precisely matched to ensure circulating current suppression. The three-port power balance algorithm establishes constraint equations that include photovoltaic output, energy storage SOC, and grid demand, enabling energy injection and extraction with three-phase voltage servoing and flexible grid configuration.

2. The multi-channel DC-coupled photovoltaic-storage converter system as described in claim 1, characterized in that, When the bidirectional DC / DC converter is operating in the forward direction, 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 and the second switch is turned off. The bidirectional DC / DC converter applies the primary photovoltaic power generation voltage Uin generated by the photovoltaic array to the first filter inductor. The current of the first filter inductor increases linearly, and the first filter inductor stores energy. In mode 2, the first switch is off and the second switch is on. The primary photovoltaic power generation voltage Uin generated by the photovoltaic array and the first filter inductor together charge and store the energy storage unit.

3. The multi-channel DC-coupled photovoltaic-storage converter system as described in claim 1, characterized in that, When the bidirectional DC / DC converter operates in reverse, 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 is off, the second switch is on, and the current of the first filter inductor increases linearly. Mode 2: The first switch is turned on, the second switch is turned off, the current of the first filter inductor cannot change abruptly, and the energy in the first filter inductor is released to the photovoltaic interface.

4. The multi-channel DC-coupled photovoltaic-storage converter system as described in claim 1, characterized in that, The energy storage unit includes a battery or a supercapacitor.

5. The multi-channel DC-coupled photovoltaic-storage converter system as described in any one of claims 1 to 4, characterized in that, The output of the photovoltaic grid-connected inverter supplies power to the grid or load via a power frequency isolation transformer, or the output of the photovoltaic grid-connected inverter supplies power directly to the grid or load.

6. 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 generates direct current (DC), and a three-port power control algorithm is used at the photovoltaic array interface to control the multi-channel DC-coupled photovoltaic-storage converter system for energy conversion, including: When power generation is abundant and the grid-connected electricity price is low, the primary DC power is converted to the energy storage unit through the DC / DC coupling unit. When the electricity consumption is at its peak and the grid-connected 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. The DC / DC coupling unit includes several bidirectional DC / DC converters that are directly connected to the photovoltaic array interface. The first-side connection ports of each bidirectional DC / DC converter are connected to several photovoltaic interfaces, and the second-side connection ports are all connected to the DC bus on the energy storage side. The energy storage unit is connected to the DC bus on the energy storage side. Each bidirectional DC / DC converter includes a second filter inductor, a third switch, and a fourth switch. The second end of the second filter inductor is connected to the first end of the fourth switch, and the second end of the fourth switch and the first end of the second filter inductor are respectively connected to two DC buses on the energy storage side. The second end of the third switch is connected to the common terminal of the fourth switch and the second inductor, and its first end is connected to the positive terminal of the photovoltaic interface. The second end of the fourth switch is connected to the negative terminal of the photovoltaic interface. The photovoltaic grid-connected inverter includes a DC / AC inverter and a DC / DC converter regulated by a maximum power point tracking system. The multi-channel DC-coupled photovoltaic-storage converter system adopts a DC bus architecture and a multi-port collaborative control mechanism. Using a common DC bus as the energy hub, the photovoltaic array is connected via a bidirectional DC / DC converter, and the energy storage unit is connected via an LLC resonant converter. On the grid-connected side, a three-level NPC converter is used to achieve DC-AC conversion. In the power transmission path, MPPT control on the photovoltaic side achieves maximum power point tracking by adjusting the duty cycle of the DC / DC converter, while maintaining stable bus voltage. On the energy storage side, a current-driven bidirectional DC-DC converter enables rapid switching between charging and discharging modes. The system employs vector control based on a synchronous rotating coordinate system, achieving active and reactive power decoupling control by adjusting the dq-axis current components. The voltage servo mechanism introduced by the system is essentially a grid synchronization technology based on an improved phase-locked loop (PLL). An orthogonal signal generator constructed using a second-order generalized integrator, combined with a software PLL algorithm, achieves sub-millisecond phase tracking. During multi-channel parallel operation, current sharing control is achieved by introducing a virtual impedance method. The output impedance characteristics of each module are precisely matched to ensure circulating current suppression. The three-port power balance algorithm establishes constraint equations that include photovoltaic output, energy storage SOC, and grid demand.

7. The multi-channel DC-coupled photovoltaic-storage converter system as described in claim 6, characterized in that, The energy storage unit includes a battery or a supercapacitor.

8. The multi-channel DC-coupled photovoltaic-storage converter system as described in any one of claims 6 to 7, characterized in that, The output of the photovoltaic grid-connected inverter supplies power to the grid or load via a power frequency isolation transformer, or the output of the photovoltaic grid-connected inverter supplies power directly to the grid or load.

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