CN-121984094-A - Off-grid charging micro-grid system based on dual-mode photovoltaic

Abstract

The invention belongs to the technical field of power electronics and new energy micro-grids, in particular relates to an off-grid charging micro-grid system based on a dual-mode photovoltaic, and aims to solve the problems of unstable voltage frequency caused by photovoltaic fluctuation in an off-grid scene and system breakdown caused by high transient charging load of an electric vehicle. The system comprises a dual-mode photovoltaic power generation unit, a hybrid energy storage buffer unit, an intelligent charging load management unit and an off-grid central control system, and realizes high-stability, long-service life and high-efficiency dispatching by dynamically switching photovoltaic working modes, power frequency division and energy storage, flexible power distribution and virtual synchronous machine control.

Inventors

• ZHANG DEAN
• ZHAO MING

Assignees

• 破晓新能源科技(上海)有限公司

Dates

Publication Date

20260505

Application Date

20260212

Claims (10)

1. 1. Off-grid charging micro-grid system based on dual-mode photovoltaic, which is characterized by comprising: The dual-mode photovoltaic power generation unit is used for dynamically switching between a maximum power tracking mode and a voltage supporting mode so as to adjust output power according to the system power surplus and shortage state; the hybrid energy storage buffer unit is connected to the direct current bus and is used for stabilizing the transient process and steady energy of the system through the power frequency division cooperation of the lithium battery pack and the super capacitor; The intelligent charging load management unit is connected to the output end of the system and used for sensing the access state of the charging pile in real time and executing flexible power distribution logic based on priority; The off-grid central control system is respectively connected with the dual-mode photovoltaic power generation unit, the hybrid energy storage buffer unit and the intelligent charging load management unit through a communication network and is used for executing global energy scheduling instructions and controlling the conversion of the system among black start, steady-state operation and fault recovery modes.
2. 2. The off-grid charging microgrid system based on dual-mode photovoltaic according to claim 1, wherein said dual-mode photovoltaic power generation unit comprises a photovoltaic array, a multi-channel interleaved parallel dc converter, and a dual-mode inverter; The multichannel staggered parallel direct current converter acquires output voltage and current signals of the photovoltaic array through a sampling loop, and feeds back real-time power data to an off-grid central control system; the dual mode inverter includes a voltage frequency control module and a maximum power tracking control module for switching modes of operation under different system conditions.
3. 3. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein the hybrid energy storage buffer unit comprises a high-rate lithium battery pack, a super capacitor pack, a bidirectional direct current converter array and an energy storage monitoring module; The bidirectional direct current converter array adopts a double closed-loop control architecture, wherein the outer ring is a bus voltage control ring, and the inner ring is a current tracking ring; The energy storage monitoring module is used for acquiring the fluctuation frequency of the direct current bus voltage in real time and distributing the lithium battery pack or the super capacitor pack to respond to corresponding power requirements according to the frequency characteristic.
4. 4. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein the intelligent charging load management unit comprises a plurality of groups of direct current charging piles, a vehicle identification module, a power adjustment controller and a load prediction module; The load prediction module calculates estimated charging load requirements in a future preset time based on the historical charging behavior data and the residual electric quantity of the current access vehicle; And the power regulation controller performs quota distribution on the output current of each direct-current charging pile according to the available power quota issued by the off-grid central control system.
5. 5. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein a virtual synchronous machine algorithm module is arranged in the off-grid central control system; The virtual synchronous machine algorithm module is used for providing inertial support and damping characteristics for the off-grid system by collecting voltage and current signals of the alternating current bus and simulating a rotor motion equation and excitation regulation characteristic of the synchronous generator in a control algorithm.
6. 6. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein the switching logic of the dual-mode photovoltaic power generation unit is used for judging based on the voltage change rate of the direct-current bus and the state of charge of the energy storage system; when the voltage change rate is lower than a preset threshold value and the stored energy charge state is in an intermediate interval, maintaining a maximum power tracking mode; when the voltage change rate continuously exceeds the threshold value and the discharge multiplying power of the energy storage system reaches a set level, the voltage source control mode is forcibly switched.
7. 7. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein the off-grid central control system has a black start management function; After the power failure of the system total station, when the effective illumination intensity is detected to meet the starting condition, the super capacitor bank is instructed to establish the initial direct current bus voltage; and then starting the dual-mode inverter to establish a reference voltage alternating current field, gradually inputting a key load after stabilizing, and guiding the lithium battery pack to be integrated into a bus.
8. 8. The off-grid charging microgrid system based on dual-mode photovoltaic according to claim 1, wherein the flexible power distribution logic of said intelligent charging load management unit performs a step-down strategy based on a current charge sequencing of the vehicle; when the total power of the system is insufficient, the charging requirement of the low-power vehicle is preferentially ensured, and trickle charging or power reduction strategy is implemented on the high-power vehicle.
9. 9. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 2, wherein the dual-mode inverter adopts an LCL type filter structure, and inductance parameters of the dual-mode inverter are matched with system switching frequency to inhibit high-frequency interference; the inverter bridge arm adopts a wide bandgap semiconductor device to reduce switching loss; in the voltage supporting mode, the internal resistance characteristic of the inverter is simulated into the sensitivity through a software algorithm so as to optimize the power sharing effect under the multi-source parallel connection.
10. 10. The off-grid charging micro-grid system based on the dual-mode photovoltaic according to claim 1, wherein the bidirectional direct current converter in the hybrid energy storage buffer unit has an autonomous current sharing function; When the energy storage modules are operated in parallel, each converter automatically fine-adjusts the output voltage reference by detecting the direct current component of the output current so as to ensure that the current deviation of each branch is within the allowable range.

Description

Off-grid charging micro-grid system based on dual-mode photovoltaic Technical Field The invention belongs to the technical field of power electronics and new energy micro-grids, and particularly relates to an off-grid charging micro-grid system based on dual-mode photovoltaic. Background Under the background of rapid evolution of energy Internet and distributed energy systems, a micro-grid plays an increasingly critical role in an electric power system as an important technical means for improving the permeability and the power supply reliability of renewable energy sources. The micro-grid realizes on-site balance and flexible scheduling of energy by integrating the distributed power generation, energy storage system and power load, and particularly has great application potential in the aspects of improving the toughness of a power distribution network and promoting green energy consumption. With the popularization of electric automobiles and mobile electric equipment, a micro-grid system with autonomous operation capability has become a core scheme for solving energy supply in special geographic environments or emergency scenes. The off-grid charging micro-grid system based on the dual-mode photovoltaic is used as an independent power unit, and is a key technical direction for guaranteeing energy self-supply in remote areas or areas without power grid coverage. The system utilizes a dual-mode photovoltaic conversion technology and aims to flexibly switch between different energy conversion modes according to the dynamic changes of illumination intensity, environmental working conditions and load demands, so that continuous and stable electric power support is provided for energy storage facilities and charging loads. The prior art still faces multiple challenges in energy flow control and operational stability of off-grid charged micro-grids. Because the off-grid system lacks voltage and frequency support of a large power grid, the extreme intermittence of photovoltaic output and random fluctuation of a load end are extremely easy to cause instantaneous oscillation of the system bus voltage, so that power supply quality is degraded and even system protection shutdown is triggered. The existing multimode switching logic often has control dead zone or response lag, and serious impact current is easy to generate in the mode conversion process, so that the hardware life of the power converter and the energy storage battery is damaged. In addition, the collaborative optimization capability among all units in the system is insufficient, and global optimal scheduling cannot be realized aiming at multidimensional variables of light, storage and charging, so that the photovoltaic power rejection rate is high and the whole energy conversion efficiency of the system is limited. These technical drawbacks are particularly pronounced in extreme environments or under high-intensity charging demands, which become a technical problem that hinders highly reliable operation of off-grid microgrid systems. Disclosure of Invention The invention aims to provide an off-grid charging micro-grid system based on a dual-mode photovoltaic, which is used for solving the problems that the system voltage frequency stability is poor due to the influence of severe fluctuation of ambient light on photovoltaic energy production in an off-grid environment, and the system frequency breakdown and the energy storage life attenuation are easy to cause when the traditional micro-grid is used for dealing with high transient charging load of an electric automobile. The technical scheme of the invention is that the method comprises the following steps: The dual-mode photovoltaic power generation unit is used for dynamically switching between a maximum power tracking mode and a voltage supporting mode so as to adjust output power according to the system power surplus and shortage state; the hybrid energy storage buffer unit is connected to the direct current bus and is used for stabilizing the transient process and steady energy of the system through the power frequency division cooperation of the lithium battery pack and the super capacitor; The intelligent charging load management unit is connected to the output end of the system and used for sensing the access state of the charging pile in real time and executing flexible power distribution logic based on priority; The off-grid central control system is respectively connected with the dual-mode photovoltaic power generation unit, the hybrid energy storage buffer unit and the intelligent charging load management unit through a communication network and is used for executing global energy scheduling instructions and controlling the conversion of the system among black start, steady-state operation and fault recovery modes. The dual-mode photovoltaic power generation unit comprises a photovoltaic array, a multi-channel staggered parallel direct current converter and a dual-mode inverter, wherein the