Photovoltaic energy storage energy mutual use router based on multi-port magnetic integrated converter

Abstract

The invention provides a photovoltaic energy storage energy mutual use router based on a multi-port magnetic integrated converter, the photovoltaic energy storage energy mutual use router comprises a plurality of independent voltage source converter (VSC) ports, the ports are connected through a common direct current bus, each port is an independent VSC, and the VSC ports are connected through a common direct current bus. The grid-connected inverters can be connected with a photovoltaic power generation system, a photovoltaic energy storage system and the DC / AC; each port of the multi-port transformer comprises a group of parasitic inductors, a group of energy storage inductors and a group of full-bridge converters. The photovoltaic energy storage system is connected with the DC / AC grid-connected inverter, the photovoltaic power generation system and the photovoltaic energy storage system are the input side of the converter, and the output side of the converter is connected with a power grid through the grid-connected inverter, so that energy generated by the photovoltaic power generation module is stored in the photovoltaic energy storage system or sent to the power grid. And the energy of the power grid can be stored in the photovoltaic energy storage system by reducing the energy level through the converter, so that bidirectional energy transmission among a plurality of ports is realized, and source-storage-grid-load energy conversion is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of the operation of an energy router for photovoltaic energy storage and energy inter - utilization, and particularly relates to a photovoltaic energy storage and energy inter - utilization router based on a multi - port magnetic integrated converter. Background Technique

[0002] Distributed Generation (DG) refers to a system composed of small - scale power generation equipment that is relatively close to the load end and has a small power generation capacity. Typical power generation forms include solar photovoltaic panels, wind turbines, biomass power generation stations, etc., to achieve local energy production and consumption. Since distributed generation does not require long - distance power transmission, it can significantly reduce transmission losses, thereby improving energy utilization efficiency. And it can balance the supply - demand relationship by peak shaving and valley filling, relieve the grid dispatching pressure, and enhance the stability and economy of the grid.

[0003] The traditional power grid adopts a mode of centralized power generation and centralized load. When applied to distributed generation, there is a problem of high line loss. Therefore, in view of the characteristics of distributed generation, the concept of a micro - grid has been proposed in the industry. A micro - grid is an autonomous system that can achieve self - control, protection, and management. It can operate in parallel with the main system or operate independently. In the grid - connected operation mode, the micro - grid inverter system acts as a transfer station, connecting the new - energy power generation unit and the grid; in the island operation mode, the output end of the micro - grid inverter system is simulated as the grid to connect the load. However, relying solely on new - energy power generation is difficult to ensure the power supply reliability of the micro - grid. The main reason is that the micro - grid itself has a small capacity, is less robust to power generation and load fluctuations, and it is difficult to maintain the balance of energy supply and demand in the grid under extreme conditions. Moreover, wind power generation has factors such as intermittency and instability, and the photovoltaic power generation is also highly affected by environmental factors such as temperature and light intensity. Therefore, a certain proportion of energy storage capacity is usually required in the micro - grid to form a new - energy power generation - energy storage system, so as to achieve the consumption of the over - generated new - energy power and compensate the load.

[0004] With the increasing global demand for sustainable energy, the residential photovoltaic energy storage system with single-family houses as the basic unit has become an important part of home energy management. The residential photovoltaic energy storage system stores the excess electric energy during the peak period of solar power generation during the day and releases it at night or on cloudy days when the light is insufficient, effectively reducing the family's dependence on grid power. This not only reduces the electricity bill expenditure but also provides users with a stable electricity price guarantee, avoiding the economic burden caused by electricity price fluctuations. According to multiple studies, households with installed residential photovoltaic energy storage systems can save an average of 15%-30% of their electricity bills annually. The residential photovoltaic energy storage system significantly reduces the consumption of fossil fuels by increasing the proportion of renewable energy used, thereby reducing greenhouse gas emissions. Each kilowatt-hour of solar power generation can reduce approximately 0.5 kilograms of carbon dioxide emissions, which is of great significance for mitigating climate change and improving air quality. In addition, the energy storage system can smooth out the fluctuations in solar power generation, improve the stability and reliability of the power grid, and reduce environmental pollution caused by power fluctuations. The residential photovoltaic energy storage system gives households a higher degree of energy autonomy, enabling them to maintain power supply even in emergencies (such as natural disasters or grid failures). This not only improves the quality of life and safety of households but also provides support for the community's emergency preparedness. Especially in remote areas or areas with insufficient grid coverage, the residential photovoltaic energy storage system is an indispensable energy solution. The residential photovoltaic energy storage system is of great significance in terms of economic benefits, environmental benefits, energy autonomy, technological innovation, and social awareness. With the continuous progress of technology and policy support, the residential photovoltaic energy storage system will become an important trend in future home energy management and contribute to the realization of sustainable development goals. The government, enterprises, and consumers should work together to promote the popularization and application of the residential photovoltaic energy storage system and jointly build a green, low-carbon, and safe energy future.

[0005] The bottleneck problem in the promotion of residential photovoltaic energy storage converters lies in economic viability, and the core issues are cost, volume, and control. Among them, the cost mainly comes from hardware costs, including the converter itself and the energy storage battery pack; in terms of volume, since residential space is relatively precious, reducing the hardware size helps to reduce the encroachment on residential space; in terms of control, how to achieve the maximum economic benefit through new energy generation and battery charge-discharge cycles based on the peak-valley electricity price difference. To solve these three problems, the industry has conducted in-depth technical explorations.

[0006] In terms of hardware, since it is necessary to connect the photovoltaic power generation port, energy storage port, and grid connection port simultaneously, a multi-port converter needs to be adopted. To reduce the size and cost of the multi-port converter, the methods of port multiplexing and magnetic integration have been proposed in the industry to improve the density of the converter and magnetic components. The traditional multi-port converter is based on a DC bus, and multiple port converters are simply connected to the DC bus. This method is relatively simple in concept, but it requires a large number of devices and has low efficiency. Therefore, adopting a magnetically integrated multi-port converter can reduce the usage of magnetic components and thus improve the power density.

[0007] A commonly used multi-port converter is the Triple Active Bridge (TAB) converter. Its basic structure is a DC-DC converter topology based on a multi-winding transformer, which is suitable for high-density multi-port energy conversion applications. Compared with traditional boost converters, the TAB converter achieves a higher voltage gain by introducing a transformer, while maintaining low input current ripple and output voltage ripple. The basic principle of the TAB converter is to utilize the turns ratio of the transformer and the magnetic core characteristics to achieve high-gain boost. Specifically, it stores energy in the primary winding of the transformer and then releases the energy in the secondary winding, thereby achieving voltage elevation. This converter has the following advantages: 1. High gain: A relatively high voltage gain can be achieved through the turns ratio of the transformer, which is suitable for applications with a high boost ratio. 2. Low ripple: The input current ripple and output voltage ripple are small, improving the stability and efficiency of the converter. 3. Wide input range: It can maintain a stable output voltage within a wide input voltage range. 4. High efficiency: High conversion efficiency can be achieved by optimizing the switching control and magnetic core design. 5. Compact design: It is smaller in volume compared to traditional boost converters and is suitable for applications with limited space. However, the disadvantage is that the cost of the transformer is relatively high, especially in high-frequency applications where high-performance magnetic core materials are required. The introduction of the transformer increases the complexity of the circuit, making the design and debugging more difficult. In addition, precise control strategies are required to ensure the coordinated operation of the main switch and auxiliary switch, avoiding excessive voltage stress and current spikes. Due to its characteristics of high gain, low ripple, and high efficiency, the TAB converter is widely used in renewable energy systems, electric vehicles, industrial power supplies, and other fields.

[0008] As a high-gain boost converter, the control method of the TAB converter is crucial for ensuring the stability and efficient operation of the system. Phase-shift control is its main control method. By adjusting the conduction and turn-off time difference (i.e., phase difference) of the three active bridge switching devices, the direction and magnitude of energy transfer are controlled. The change in the phase-shift angle directly affects the exciting current of the transformer and the output voltage. Its control is flexible and suitable for bidirectional energy transfer. It can achieve zero-voltage switching (ZVS) and zero-current switching (ZCS), improving efficiency and reducing switching losses, meeting the requirements of various application scenarios.

[0009] The household photovoltaic energy storage converter is a solution that combines a solar photovoltaic system with an energy storage system, aiming to improve energy utilization efficiency, reduce dependence on the power grid, and provide a stable power supply. However, there are still some problems in the research and application of household photovoltaic energy storage converters: 1. How to effectively integrate the photovoltaic system and the energy storage system to achieve efficient energy management and optimal scheduling. 2. How to reduce costs, especially the cost of the energy storage system. 3. How to improve the energy conversion efficiency of the photovoltaic energy storage converter. 4. How to enhance the environmental adaptability of the household photovoltaic energy storage system, study the system performance under different environmental conditions, and optimize the system design to adapt to various environments.

[0010] In response to the above requirements, the present invention proposes a photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter. This invention integrates a photovoltaic power generation system and a photovoltaic energy storage system, which can reduce hardware costs, improve economic efficiency, and achieve a higher energy density. Summary of the Invention

[0011] To solve the above problems, the present invention provides a photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter, which can provide a device and solution that reduces carbon emissions, improves power supply reliability, is low - cost and easy to install, and can achieve power flow control and intelligent information interconnection on the basis of having a photovoltaic energy storage system and a power generation function, and realizes a high redundancy of power generation and power supply.

[0012] Specifically, the present invention is a photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter. The photovoltaic energy storage energy inter - use router includes multiple independent voltage - source converter (VSC) ports, which are connected through a common DC bus. Each port is an independent VSC and can be connected to a photovoltaic power generation system, a photovoltaic energy storage system, and a DC / AC grid - connected inverter.

[0013] Furthermore, the photovoltaic energy storage energy inter - use router includes a magnetically integrated multi - port transformer. Each port of it includes a set of parasitic inductors and energy storage inductors, as well as a set of full - bridge converters. The parasitic inductors and the energy storage inductors are located between the full - bridge converter and the transformer port. The parasitic inductors are connected in parallel across the transformer port, and the energy storage inductors are connected in series between the full - bridge converter and the parasitic inductors. Thus, the photovoltaic energy storage energy inter - use router is formed, which connects the photovoltaic power generation system, the photovoltaic energy storage system, and the DC / AC grid - connected inverter. The photovoltaic power generation system and the photovoltaic energy storage are on the input side of the converter, and the output side of the converter is connected to the power grid through the grid - connected inverter, realizing that the energy generated by the photovoltaic power generation module is stored in the photovoltaic energy storage system or fed into the power grid. It can also reduce the energy level of the power grid energy through the converter and store it in the photovoltaic energy storage system, thereby realizing bidirectional energy transfer between multiple ports and achieving energy conversion among the source - storage - grid - load.

[0014] Further, the full-bridge converter is a multi-port magnetically integrated power electronic converter, i.e., a Triple Active Bridge (TAB) converter; the full-bridge converter is a DC / DC converter adopting magnetically integrated technology, with multiple transformer windings wound around the same set of iron cores, multiple transformers integrated on the same device, multiple ports sharing the same iron core, sharing magnetic components or equivalent components, reducing magnetic components, and each port being isolated from each other. The transformer achieves electrical isolation between the primary and secondary windings.

[0015] Further, the multi-port magnetically integrated DC / DC converter included in the photovoltaic energy storage energy interconversion router adopts single-phase-shift control. The energy transfer direction between two ports is adjusted by regulating the phase of the square-wave voltage on one side relative to the other side. The energy flow between each VCS port is achieved by controlling the phase difference of the square-wave voltages between the two full-bridge converters and the transformer. When the phase difference is positive, electrical energy is transferred from the phase-lagging side to the phase-leading side. When the phase difference is negative, similarly, electrical energy is transferred from the phase-lagging side to the phase-leading side, realizing the transfer of energy between each port.

[0016] Further, the photovoltaic energy storage energy interconversion router includes two equivalent topologies, corresponding to different operating states, namely the TAB operating mode and the DAB operating mode, i.e., the three-port operating mode and the two-port operating mode respectively. The three-port operating mode is divided into single-input double-output and double-input single-output modes. In the single-input double-output mode, the photovoltaic power generation system transfers energy to the power grid and the photovoltaic energy storage system; in the double-input single-output mode, the photovoltaic power generation system and the photovoltaic energy storage system transfer energy to the power grid; the two-port operating mode is a single-input single-output mode, only connecting the photovoltaic energy storage system and the grid side and realizing bidirectional energy transfer.

[0017] Further, the photovoltaic energy storage energy interconversion router connects each discrete device through multiple transformers. The transformer is a magnetically coupled isolation device, which can electrically isolate each discrete device from each other without direct electrical contact. The electrical or mechanical damage of any port will not directly affect the operation of the devices of other ports.

[0018] Further, the photovoltaic power generation system adopts maximum power tracking based on the perturbation observation method, which can adjust the output voltage according to the output power and the voltage change rate, enabling the photovoltaic power generation system to operate in the state of the highest output power and maximizing the utilization of solar energy.

[0019] Further, for the microgrid energy mutual assistance solution supported by the photovoltaic energy storage energy interconversion router, the entire microgrid consists of household users installed with the photovoltaic energy storage energy interconversion router.

[0020] Furthermore, when the distribution network is powered off, the microgrid energy mutual assistance solution provides continuous power supply to each household through the distributed photovoltaic and energy storage system. The photovoltaic energy storage energy mutual use router needs to ensure power conservation within the system, and the operation modes are mainly divided into two types: grid-connected mode and island mode.

[0021] Furthermore, when the user chooses not to connect to the community power grid, the photovoltaic energy storage energy mutual use router will independently supply power to this user, and at this time, a single household microgrid forms a nano-grid; if the user chooses to connect to the community microgrid, the photovoltaic energy storage energy mutual use router will be connected to other "nano-grids" through the community power grid to form an energy complementary network.

[0022] Compared with the prior art, the beneficial effects are as follows:

[0023] (1) The system adopts a photovoltaic power generation system based on the Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) algorithm, which has the following advantages: simple and easy to implement, the structure of the perturb and observe method is simple and easy to implement, without complex calculations or multiple sensors; fast response speed, when the external environment or load changes suddenly, the perturb and observe method can respond quickly and adjust the operating point of the photovoltaic array to approach the maximum power point; high power generation efficiency, by adjusting the operating point of the photovoltaic system in real time to adapt to the changing environmental conditions, the perturb and observe method can maximize the energy output of the photovoltaic power generation system and improve the power generation efficiency of the photovoltaic array; strong adaptability, the perturb and observe method can adapt to changes in external environments such as light intensity and temperature. By periodically changing the operating point of the photovoltaic system, it can track the maximum power point of the photovoltaic cell in real time. Reduce system oscillation: Introduce a variable step size strategy. The improved perturb and observe method uses a large step size to quickly approach the MP when far from the maximum power point, and uses a small step size when approaching the maximum power point to reduce oscillation; improve system stability and reliability: The perturb and observe method can overcome the shortcoming of not being able to operate at the maximum power point when the external environment changes, and improve the stability and reliability of the photovoltaic power generation system;

[0024] (2) The system adopts a multi-port magnetically integrated isolated bidirectional power electronic DC-DC converter. Multi-port magnetic integration can reduce the number of inductive components, has a compact structure, improves the steady-state operating efficiency, and improves the transient response speed. The volume and weight of the converter are reduced, and at the same time, the power density is increased; the isolated bidirectional DC-DC converter realizes the bidirectional flow of electrical isolation power at the same time, increases the safety and reliability of the system, can adapt to different working conditions and environments, and has strong adaptability;

[0025] (3) It is proposed to achieve energy mutual assistance among household energy routers, effectively increasing the proportion of new energy generation in the distribution network, reducing carbon emissions, and enhancing the local consumption capacity of photovoltaic power generation. On this basis, the charge and discharge cycle of the battery is optimized based on real-time ladder electricity prices, bringing economic benefits to users while assisting the power grid to achieve peak-valley power rebalancing, and ultimately improving the economic operation of rural distribution networks. In addition to the above, the energy router cluster constructs a community microgrid, providing active support for the rural power grid in the event of sudden disaster power outages, ensuring the reliability of power supply in the distribution network, and effectively reducing the economic losses brought by power outages to the national economy. Description of the Drawings

[0026] Figure 1 It is a structural schematic diagram of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0027] Figure 2 It is a topology diagram of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0028] Figure 3 It is a topology diagram of the converter in the single-input single-output mode of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0029] Figure 4 It is an energy flow block diagram of the photovoltaic-to-grid energy flow in the single-input single-output mode of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0030] Figure 5 It is an energy flow block diagram of the grid-to-photovoltaic energy storage energy flow in the single-input single-output mode of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0031] Figure 6 It is an energy flow block diagram of the single-input double-output mode of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0032] Figure 7 It is a circuit topology diagram in the single-input double-output mode of the TAB converter of a photovoltaic energy storage energy-interchange router based on a multi-port magnetic integration converter disclosed by the present invention;

[0033] Figure 8 It is an energy flow block diagram of the double-input single-output mode of the TAB converter of an energy router for photovoltaic energy storage energy-interchange based on a multi-port magnetic integration converter disclosed by the present invention;

[0034] Figure 9A circuit topology diagram of the energy flow in the dual-input single-output mode of the TAB converter of a photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter disclosed by the present invention;

[0035] Figure 10 A control block diagram of the output port voltage between two ports of the TAB converter of a photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter disclosed by the present invention;

[0036] Figure 11 I-U and P-U curve graphs of a photovoltaic power generation system of a photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter disclosed by the present invention;

[0037] Figure 12 An implementation block diagram of the MPPT control of a photovoltaic power generation system of a photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter disclosed by the present invention;

[0038] Figure 13 A diagram of constructing a community-level microgrid based on the interconnection cluster of multiple household energy routers when the photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter is off-grid. Specific embodiments

[0039] The following will elaborate in detail on the specific embodiments of a photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter of the present invention with reference to the accompanying drawings.

[0040] 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 will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The present invention realizes the above functions through the following technical means: A photovoltaic energy storage energy inter-using router based on a multi-port magnetic integrated converter and a microgrid solution based on this are proposed in terms of the hardware circuit and system operation mode. The overall block diagram of the system is as Figure 1 shown.

[0042] The photovoltaic energy storage energy inter-using router includes multiple independent voltage source converter (VSC) ports, which are connected through a common DC bus. Each port can be an independent VSC, and each can be connected to a photovoltaic power generation system, a photovoltaic energy storage system, and a grid-connected inverter of DC / AC.

[0043] The photovoltaic energy storage and mutual utilization router includes a magnetically integrated multi-port transformer. Each port of the transformer includes a group of parasitic inductors, energy storage inductors, and a group of full-bridge converters. The parasitic inductors and energy storage inductors are located between the full-bridge converters and the transformer ports. The parasitic inductors are connected in parallel across the two ends of the transformer port (on the transformer side), and the energy storage inductors are connected in series between the full-bridge converter and the parasitic inductors (on the full-bridge converter side). Thus, the above-mentioned energy router is formed, connecting the photovoltaic power generation system, the photovoltaic energy storage system, and the DC / AC grid-connected inverter. The photovoltaic power generation system and the photovoltaic energy storage system are on the input side of the converter, and the output side of the converter is connected to the grid through the grid-connected inverter, realizing that the energy generated by the photovoltaic power generation module is stored in the photovoltaic energy storage system or fed into the grid. It is also possible to store the energy from the grid in the photovoltaic energy storage system after reducing the energy level through the converter, thereby realizing the bidirectional energy transfer between multiple ports and achieving the energy conversion among the source, storage, grid, and load.

[0044] Furthermore, the photovoltaic energy storage and mutual utilization router is a multi-port magnetically integrated power electronic converter, namely a Triple Active Bridge (TAB) converter. The photovoltaic energy storage and mutual utilization router has the advantages of high power density, flexible power flow direction, electrical isolation, etc., can meet the requirements of high voltage and high power of DC grids, and is also suitable for the access of distributed energy sources such as photovoltaic and energy storage. This converter uses a DC / DC converter with magnetic integration technology, where multiple transformers are wound around the same set of iron cores, integrating multiple transformers in the same device. Multiple ports share the same iron core, share magnetic components or equivalent components, reducing magnetic components (coupled integration). Each port is isolated from each other, and the transformer achieves electrical isolation between the primary and secondary windings. This isolation effect is based on its working principle, i.e., Faraday's law of electromagnetic induction. When the transformer operates, alternating current is fed into the primary winding, which generates a changing magnetic flux in the iron core. These changing magnetic fluxes then induce electromotive forces in both the primary and secondary windings. Once the secondary winding induces an electromotive force, it can provide an alternating voltage for the secondary-side circuit. When the secondary winding is connected to a load and current flows through it, this affects the magnetic flux in the magnetic circuit, which in turn causes a change in the current in the primary winding. Although there is no direct electrical connection between the primary and secondary windings, they achieve energy transfer through the change in magnetic flux in the magnetic circuit. This is how the transformer operates and is the basis for achieving electrical isolation between the primary and secondary windings. Electrical isolation reduces the mutual interference between two different circuits. After adopting electrical isolation, when a circuit is grounded, it will not affect the operation of the entire power grid. At the same time, the insulation condition of the circuit to the ground can be detected through an insulation monitoring device. Once the circuit is grounded, an alarm can be issued in a timely manner to remind the management staff to repair or handle it in a timely manner, avoiding the phenomenon of the protection device tripping and power outage. Further avoiding the influence of the neutral point grounding on the grid side on other side devices. Compared with traditional multi-stage energy conversion, this converter only needs to perform one energy conversion, greatly improving the efficiency of the DC / DC converter, further improving the efficiency of the system energy conversion, and can achieve power transfer between ports, making power flow control simpler. The voltage transformation ratio can be changed through a high-frequency transformer, reducing the volume of the transformer, increasing the power density, and further reducing costs. The improvement of the characteristics of the hardware circuit is mainly achieved through the optimization of the circuit topology and magnetic components. The topology mainly needs to meet the voltage change and power requirements, and on this premise, improve the energy conversion efficiency as much as possible and provide power control functions. The multi-port converter with magnetic integration can reduce the number of power semiconductor devices and magnetic components used. The resonant DC converter or dual active bridge converter can be used on the DC side to achieve soft-switching control and maintain a high operating efficiency under different working conditions.

[0045] Furthermore, multiple ports are connected to the same converter, and there is a full-bridge converter at each port. By changing the phase difference of the square-wave voltages between every two full-bridges and the transformer, bidirectional energy transfer between two ports can be achieved. The multi-port magnetically integrated DC / DC converter included in the photovoltaic energy storage and mutual utilization router adopts single-phase-shift control. The energy transfer direction between two ports is adjusted by regulating the phase of the square-wave voltage on one side relative to the other side. The energy flow between each VCS port is realized by controlling the phase difference of the square-wave voltages between every two full-bridge converters and the transformer. When the phase difference is positive, electric energy is transferred from the phase-lagging side to the phase-leading side. When the phase difference is negative, similarly, electric energy is transferred from the phase-lagging side to the phase-leading side, and energy transfer between ports can be achieved.

[0046] Multiple ports are connected to the same converter, and there is a full-bridge converter at each port. By changing the phase difference of the square-wave voltages between every two full-bridges and the transformer, bidirectional energy transfer between two ports can be achieved. The DC / DC converter included in the router adopts single-phase-shift control. The energy transfer direction between two ports is adjusted by regulating the phase of the square-wave voltage on one side relative to the other side. When the phase difference is positive, electric energy is transferred from the phase-lagging side to the phase-leading side. When the phase difference is negative, similarly, electric energy is transferred from the phase-lagging side to the phase-leading side, and energy transfer between ports can be achieved.

[0047] The photovoltaic energy storage and mutual utilization router includes two equivalent topologies, corresponding to different working states, namely TAB (three active bridges) and DAB (dual active bridges).

[0048] Further, Figure 2 is the topological structure of the TAB converter, where 1 high-frequency three-winding transformer is connected to 3 voltage-source H-bridge modules. The turns ratio of the transformer is N1∶N2∶N3. The AC output voltages of each H-bridge are v1, v2, and v3 respectively. The leakage inductances of each winding are L1, L2, and L3 respectively. The leakage inductance includes the sum of the self-leakage inductance of the transformer and the externally connected inductance. Each switch is represented by Si (i = 1, 2,..., 11, 12). v1 is the voltage of the photovoltaic power generation port on the DC side, v2 represents the voltage of the photovoltaic energy storage on the DC side, and v3 represents the DC voltage on the grid side. The three ports of the TAB converter are all bidirectional ports. According to the number of input and output ports, the working modes of the TAB converter can be divided into single input single output, single input dual output mode, and dual input single output mode.

[0049] Furthermore, the single-input single-output mode operates when the photovoltaic power supply is insufficient during off-grid operation, enabling the energy of the photovoltaic energy storage system to supply power to grid-side users; the dual-input single-output mode operates when photovoltaic power generation and photovoltaic energy storage are on the input side, supplying power to the grid side; the single-input dual-output mode operates when the router is off-grid, inputting the energy generated by photovoltaic power generation into the photovoltaic energy storage and the grid side, and the grid side is used to supply power to users.

[0050] Furthermore, when the router operates in the single-input single-output mode, this converter is converted into a DAB converter, that is, a dual-port network converter, and the converter topology of the single-input single-output mode is Figure 3 . At this time, there are two cases of energy flow. The first is that the photovoltaic energy storage system is the input and the grid side is the output, and the stored electric energy is output to the grid user side to release energy, Figure 4 which is the photovoltaic energy storage -> grid block diagram; the second is that the grid side is the input and the photovoltaic energy storage system is the output, and the energy of the grid is stored in the photovoltaic energy storage system to store energy, Figure 5 which is the grid -> photovoltaic energy storage block diagram.

[0051] Further, the DAB converter adopts phase-shift control, that is, by changing a lead-lag relationship between the primary side and the secondary side, bidirectional energy flow is achieved. The DAB converter controls the external phase shift angle by fixing the internal phase shift angle. If the output phase angle lags behind the input phase angle, it is forward transmission; if the input phase angle lags behind the output phase angle, it is reverse transmission. To control the direction and magnitude of power transmission, by controlling the switch tubes S1 - S4, S5 - S8 and applying corresponding pulses, the switches can be alternately turned on and off to achieve bidirectional energy transmission. By controlling the phase difference between the two AC square-wave voltages vp and vs, the transmitted power and the output voltage are controlled.

[0052] Further, when the photovoltaic energy storage energy-interchange router operates in the single-input dual-output mode, the photovoltaic power generation side is the input, and the grid side and the photovoltaic energy storage side are the outputs, Figure 6It is a block diagram of an energy flow system in a single-input double-output mode. The present invention adopts a single-phase shift (SPS) modulation method, fixes the duty cycle of the full-bridge single transistor on the vp and vs sides to 0.5, and adjusts the output of the converter only by changing the phase difference between vp and vs. The drive signals of S1 and S3 are the same, the drive signals of S2 and S4 are the same, and the drive signals of S1 and S2 are opposite. On the inverter side, the drive signals of S5 and S7 are the same, and the drive signals of S5 and S6 are opposite. According to the different transmitted powers, the phase shift angle is the phase angle difference between S1 and S5. By changing this difference, the power transmission at both ends is controlled. When the phase angle difference is positive, that is, the power is transmitted from the photovoltaic side to the grid side. Therefore, the forward flow of energy (photovoltaic -> grid) can be achieved by adjusting the phase angle difference. The SPS modulation has fewer control variables and is simple and easy to implement.

[0053] Furthermore, when the photovoltaic energy storage energy inter-use router operates in a single-input double-output mode, it is a three-port power electronic converter, which is a TAB (three-active-bridge converter). Figure 7 It is a circuit topology in a single-input double-output mode, evolved from the dual-active-bridge DAB. It can realize the mutual transmission of DC electrical energy between three ports, and its working principle is similar to that of the dual-active-bridge DAB. At this time, there are two output ports, namely the photovoltaic energy storage side and the grid side. vs is the alternating square wave voltage input on the photovoltaic side, and vs1 and vs2 are the alternating square wave voltages output on the grid side and the energy storage side respectively. By fixing the internal phase shift angle and controlling the external phase shift angle, there is only a situation of forward energy transmission (vp -> vs1 / vs2) in the present invention. The reverse transmission situation belongs to an abnormal state, so it is not described. In order to control the forward power transmission and the magnitudes of vs1 and vs2, by controlling the switching transistors S1 - S4, S5 - S8, S9 - S12 and applying appropriate pulses to alternately turn on and off the switches, the energy can be transmitted from one port to two ports.

[0054] Furthermore, for the three-active-bridge converter, the single-phase shift (SPS) modulation method is also adopted for its working mode. The duty cycles of the full-bridge single transistors on the sides where vp, vs1, and vs2 are located are fixed at 0.5, and the output of the converter is adjusted only by changing the phase difference between vp and vs1, vs2. The driving signals of S1 and S3 are the same, the driving signals of S2 and S4 are the same, and the signals of S1 and S2 are opposite. On the inverter side, the driving signals of S5 and S7 are the same, the driving signals of S6 and S8 are the same, and the driving signals of S5 and S6 are opposite. On the energy storage side, the driving signals of S9 and S11 are the same, the driving signals of S10 and S12 are the same, and the driving signals of S9 and S10 are opposite. According to the different transmitted powers, the phase shift angle is the phase angle difference between S1 and S5 and between S1 and S9. By changing these two differences, the power transmission from one end to both ends is controlled. The larger the difference, the smaller the output-side power. As long as it is ensured that the phase difference between vs1, vs2 and vp is positive, the forward transmission of energy can be realized, that is, the power is transmitted from the photovoltaic side to the energy storage side and the grid side. Therefore, the flow of energy can be realized through the adjustment of the phase angle difference. Similar to the DAB in the single-input single-output case, the present invention adopts single-phase shift control.

[0055] Further, when the photovoltaic energy storage energy inter-use router operates in the dual-input single-output mode, it is still a three-port power electronic converter, which is a three-active-bridge converter. At this time, there are two output ports, namely energy storage and the grid. Its energy flow and topology are respectively as Figure 8 and Figure 9 shown. vp1 and vp2 are the alternating square-wave voltages input on the photovoltaic side and the energy storage side respectively, and vs is the alternating square-wave voltage output on the grid side. By keeping the duty cycle of the single transistor on the grid-connection side at 0.5 and the phase of vs unchanged, the phase differences between the input sides vp1, vp2 and vs are adjusted to control the grid-connection side voltage.

[0056] Further, in the single-input single-output mode, the single-input dual-output mode, and the dual-input single-output mode, the present invention adopts the following control strategy. The full bridges for which the phase differences are controlled are different. Figure 10 is the control block diagram of the TAB. Where Vref is the reference voltage, that is, the voltage desired on the output side of the converter. ΔV is the error between the actual voltage on the output side and the reference voltage. Through calculation by the controller, the phase difference Δβ between the rectifier bridge on the output side and the inverter bridge on the input side is obtained, so as to achieve the purpose of adjusting the output-side voltage to be equal to the input-side voltage.

[0057] Further, the present invention adopts the magnetic integration technology. By means of improving the magnetic core structure, winding configuration, and increasing the air gap, etc., the equivalent excitation inductance and resonance inductance required by the transformer are integrated inside the transformer, thereby reducing the use of external independent inductors. This technology helps to reduce the system cost and volume and improve the power density.

[0058] Furthermore, for the photovoltaic power generation system, the present invention adopts a control algorithm of maximum power point tracking to maximize the power output of the photovoltaic system and the power generation efficiency of the photovoltaic power generation. The output voltage and current of the photovoltaic module follow the I-U curve and P-U curve, Figure 11 which are the I-U and P-U curves of the photovoltaic cell. If it is desired to maximize the power output of the inverter, the DC voltage needs to operate at the Figure 11 black dot on it, and this point is the maximum power point.

[0059] Furthermore, for the control algorithm of maximum power point tracking, since the curve changes with different light intensities, temperatures and light shading, the maximum power point also changes accordingly. Therefore, the converter needs to continuously search for this maximum power point to ensure the maximum output of the panel energy throughout the day, thereby not wasting photovoltaic resources. The present invention adopts the maximum power tracking method (Maximum Power Point Tracking, MPPT) to achieve maximum power output. There is a one-to-one correspondence between the power output of the photovoltaic and its output voltage. To make it operate at the maximum power point and ensure that the operating voltage of the solar cell array is at the voltage corresponding to the peak power point, MPPT continuously adjusts the operating voltage of the photovoltaic array to make it always operate near the maximum power point, thereby maximizing the energy conversion efficiency, reducing energy waste and improving the performance of the system. To achieve maximum power tracking, the present invention adopts the Perturb and Observe (P&O) method. The power calculation formula of the photovoltaic output is: P=(U + ΔU)(I + ΔI), which is simplified to P = ΔI×U+ΔU×I,

[0060] When the system operates at the maximum power point, ΔP = dP / dU≈0. Therefore, at the maximum power point, there is: ΔU / ΔI = U / I. In the Perturb and Observe (P&O) method, the monitoring of the power change rate (dP / dU) of the photovoltaic module, that is, the derivative of power with respect to voltage. If the detected power change rate dP / dU is positive, increasing the voltage can obtain a greater power output, and the system will correspondingly increase the operating voltage. On the contrary, if dP / dU is detected to be negative, it indicates that reducing the voltage can obtain a greater power, and the system will reduce the operating voltage. In the preset dead zone where dP / dU is close to zero and the power change rate is very small and almost negligible, the system will keep the voltage unchanged to avoid unnecessary oscillations near the maximum power point. Through this mechanism, the P&O algorithm can effectively adjust the operating voltage of the photovoltaic system to ensure that the system always operates at the maximum power point. The implementation block diagram of MPPT is as Figure 12 shown, and it can be combined with Figure 10 to achieve the energy conversion of the router.

[0061] Furthermore, based on the above topological structure and operation mode, the invention proposes a microgrid energy mutual assistance scheme supported by the energy router, and the entire microgrid is composed of household users installed with the above routers.

[0062] Furthermore, in the first case, when the distribution network is powered off, the scheme provides continuous power supply to each household through the distributed photovoltaic and energy storage system. By constructing a community-level microgrid through a multi-household microgrid, electrical energy can still be obtained from the microgrid when the distribution network is not accessible, enhancing the reliability of the system.

[0063] Furthermore, in the second case, when the entire power system is in a normal working state, the photovoltaic system outputs energy to the photovoltaic energy storage system and the power grid, and its energy flow direction is as Figure 5 shown, or the power grid supplies power to the photovoltaic energy storage system and users, and its energy flow direction is as Figure 4 ; when the power system fails and the entire microgrid is in an off-grid state, the photovoltaic energy storage system or / and the photovoltaic power generation system supply power to individual users or supply power to the community microgrid, and its energy flow direction is as Figure 3 or Figure 7 .

[0064] Furthermore, in the first case, the photovoltaic energy storage energy mutual use router needs to ensure power conservation within the system. Its operation modes are mainly divided into two types: grid-connected mode and island mode. In these two modes, according to the power and load conditions inside the port, they can be further subdivided into overloading and underloading states. In a DC microgrid, since there is no voltage frequency problem, the power is usually directly related to the voltage of the DC bus.

[0065] In the formula, P in is the sum of the input powers of each port, P out is the sum of the output powers of each port, and P line is the line loss.

[0066] P in＝ P out+ P line

[0067] Since the line and port contain inductance, the change of current will not occur immediately. Therefore, when the power changes suddenly and the current remains stable, the bus voltage will be affected first. In a DC microgrid, there is a positive correlation between the voltage of the DC bus and the power difference on the bus. When the power generation power exceeds the load power, the voltage will rise; on the contrary, when the power generation power is lower than the load power, the voltage will drop. Therefore, adjusting the bus voltage is actually adjusting the output power of each port.

[0068] Furthermore, in the second case, when the user chooses not to connect to the community power grid, the PV energy storage and mutual utilization router will independently supply power to the user, and at this time, a single-household microgrid forms a nano-grid. If the user chooses to connect to the community microgrid, the PV energy storage and mutual utilization router will be connected to other "nano-grids" through the community power grid to form a network with complementary energy. As Figure 13 shown. The capacity is enhanced through this design to improve the power supply reliability of the community-level microgrid. In this case, the present invention realizes the balanced distribution of power among the nano-grids through droop control.

[0069] The active power output by any of the nano-grids is determined by the P-f (power-frequency) droop curve. Different nano-grids will have different droop coefficients, which are closely related to factors such as the rated capacity of the nano-grid, the state of charge (SoC) of the energy storage system, and the PV power generation. As the AC microgrid gradually reaches a stable state, each nano-grid operates at the same frequency and works at the stable state point. At this working point, each nano-grid will evenly distribute the load power according to its actual situation. This enables the microgrid to respond more flexibly and efficiently to load changes and improves the power supply reliability of the entire system. The droop control equation of the microgrid is as follows.

[0070]

[0071] The subscript n represents the number of the AC subnet, and i represents the i-th nano-grid; d n，j is the droop coefficient of the i-th nano-grid; is the frequency of its reference output voltage, f max and f min are respectively the maximum and minimum operating frequencies allowed for the AC subnet, and is the maximum active power that the i-th nano-grid can output.

[0072] Embodiment 1

[0073] The household multi-port magnetic integrated energy router is small in volume, compact in structure, high in power density, and has a lower price. It is equipped with a photovoltaic power generation and photovoltaic energy storage system and can be installed in household users at a lower cost. Multiple household users in a local area install this system to form a microgrid. When the entire microgrid operates in the grid-connected state, the photovoltaic power generation system provides power to the grid side at this time. The direct current generated by the photovoltaic array passes through a multi-port power electronic converter (three-active-bridge magnetic integrated converter) through phase-shift control and is transformed to the maximum power operating point to maximize the power output of the photovoltaic system, making full use of photovoltaic power. Further, it is inverted and connected to the grid through the grid-side grid connection to supply surplus electric energy to the grid. This invention has photovoltaic energy storage and can output the electric energy in the energy storage system to supply power to the grid when necessary. The photovoltaic and energy storage systems can store the surplus electric energy during the day and release it during peak demand or at night. In the above two forms, except for the installation cost, users installing this system will not bear any other costs, achieving zero-cost power generation, obtaining economic benefits from selling electric energy, and spreading the equipment cost. In the long run, there is a possibility of obtaining additional income.

[0074] Embodiment 2

[0075] When the entire microgrid is disconnected from the grid, that is, the community microgrid is disconnected from the grid and the grid no longer supplies electric energy to the community in the short term. For example, in the case of grid faults or power outages, the households equipped with this router system can enable the electric energy generated by the photovoltaic cells in a short time as a backup power source to supply electric energy for themselves, achieving short-term self-sufficiency in electricity and ensuring the continuous power supply of important loads. At the same time, electric energy can be stored through the energy storage device to cope with the influence of night or cloudy and rainy weather.

[0076] In addition to supplying electric energy for themselves, when the equipment of a certain household fails or the self-supplied energy is insufficient, other households can supply the surplus energy they generate or store to the households in need of this electric energy, achieving "peak shaving and valley filling" between households. There may be interest disputes during this period, and this problem can be solved by counting the electric energy output by each household and the electric energy obtained by each household from the microgrid and unified charging and payment.

[0077] Finally, it should be noted that the technical solutions of the present invention are only illustrated in combination with the above embodiments and are not limited thereto. Those of ordinary skill in the art should understand that those skilled in the art can modify or equivalently replace the specific implementation manners of the present invention, but these modifications or changes are all within the scope of the claims pending for approval.

Claims

1. A photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter, characterized in that, The photovoltaic energy storage and energy inter - use router includes multiple independent voltage source converters (VSCs) ports, which are connected through a common DC bus. Each port is an independent VSC and can be connected to a photovoltaic power generation system, a photovoltaic energy storage system, and a grid - connected inverter for DC / AC. The photovoltaic energy storage and energy inter - use router includes a magnetically integrated multi - port transformer. Each port of the transformer includes a set of parasitic inductors, energy storage inductors, and a set of full - bridge converters. The parasitic inductors and the energy storage inductors are located between the full - bridge converter and the transformer port. The parasitic inductors are connected in parallel across the two ends of the transformer port, and the energy storage inductors are connected in series between the full - bridge converter and the parasitic inductors. Thus, the photovoltaic energy storage and energy inter - use router is formed, which connects the photovoltaic power generation system, the photovoltaic energy storage system, and the DC / AC grid - connected inverter. The photovoltaic power generation system and the photovoltaic energy storage are on the input side of the converter, and the output side of the converter is connected to the grid through the grid - connected inverter, enabling the energy generated by the photovoltaic power generation module to be stored in the photovoltaic energy storage system or fed into the grid. It can also reduce the energy level of the grid energy through the converter and store it in the photovoltaic energy storage system, thereby realizing bidirectional energy transfer between multiple ports and achieving energy conversion among the source, storage, grid, and load.

2. The photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 1, wherein The full - bridge converter is a multi - port magnetically integrated power electronic converter, namely a triple - active - bridge (TAB) converter; the full - bridge converter is a DC / DC converter adopting magnetic integration technology, with multiple transformer windings wound around the same set of iron cores, multiple transformers integrated in the same device, multiple ports sharing the same iron core, sharing magnetic components or equivalent components, reducing magnetic components, and isolating each port from each other. The transformer realizes electrical isolation between the primary and secondary windings.

3. The photovoltaic energy storage energy inter - use router based on a multi - port magnetic integration converter according to claim 2, characterized in that, The multi - port magnetically integrated DC / DC converter included in the photovoltaic energy storage and energy inter - use router adopts single - phase - shift control. The direction of energy transfer between two ports is regulated by adjusting the phase of the square - wave voltage on one side relative to the other side. The energy flow between each VCS port is realized by controlling the phase difference of the square - wave voltages between the two full - bridge converters and the transformer. When the phase difference is positive, the phase - lagging side transfers electrical energy to the phase - leading side. When the phase difference is negative, similarly, the phase - lagging side transfers electrical energy to the phase - leading side, achieving energy transfer between each port.

4. A photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 3, characterized in that, The photovoltaic energy storage and energy inter - use router includes two equivalent topologies, corresponding to different working states, namely the TAB working mode and the DAB working mode, that is, the three - port working mode and the two - port working mode respectively. The three - port working mode is divided into single - input double - output and double - input single - output modes. In the single - input double - output mode, the photovoltaic power generation system transfers energy to the grid and the photovoltaic energy storage system; in the double - input single - output mode, the photovoltaic power generation system and the photovoltaic energy storage system transfer energy to the grid; the two - port working mode is a single - input single - output mode, which only connects the photovoltaic energy storage system and the grid side and realizes bidirectional energy transfer.

5. A photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 4, characterized in that, The photovoltaic energy storage and mutual utilization router connects each discrete device through multiple transformers. The transformers are magnetically coupled isolation devices that can electrically isolate each discrete device from each other without direct electrical contact. Electrical or mechanical damage to any port will not directly affect the operation of the devices at other ports.

6. The photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 5, characterized in that, The photovoltaic power generation system adopts maximum power tracking based on the perturbation observation method, which can adjust the output voltage according to the change rate of the output power with respect to the voltage, enabling the photovoltaic power generation system to operate at the state of the highest output power and maximizing the utilization of light energy.

7. A photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 6, characterized in that, For the microgrid energy mutual assistance scheme supported by the photovoltaic energy storage and mutual utilization router, the entire microgrid consists of household users equipped with the photovoltaic energy storage and mutual utilization router.

8. A photovoltaic energy storage energy inter - use router based on a multi - port magnetic integrated converter according to claim 7, characterized in that, When the distribution network is powered off, the microgrid energy mutual assistance scheme provides continuous power supply to each household through the distributed photovoltaic and energy storage system. The photovoltaic energy storage and mutual utilization router needs to ensure power conservation within the system, and its operation modes are mainly divided into two types: grid-connected mode and island mode.

9. The photovoltaic energy storage energy inter - use router based on a multi - port magnetic integration converter according to claim 7, characterized in that, When the user chooses not to connect to the community power grid, the photovoltaic energy storage and mutual utilization router will independently supply power to this user, and at this time, a single-household microgrid forms a nano-grid; if the user chooses to connect to the community microgrid, the photovoltaic energy storage and mutual utilization router will be connected to other "nano-grids" through the community power grid to form an energy complementary network.

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