Disaster-resistant intelligent micro-grid system and control method of light storage coordination

Abstract

The application provides an anti-disaster intelligent micro-grid system with light storage synergy, which comprises a photovoltaic power generation unit, an energy storage power station unit, a detection module unit, a power grid unit and a load unit; a Boost converter and MPPT control are used on the photovoltaic side; a Buck-Boost bidirectional converter and voltage-current double closed loop control are used on the energy storage side; a virtual synchronous generator control and voltage-current double closed loop output SVPWM modulation wave are used on the power grid and load side. The system supports three operation modes of normal grid connection, planned / fault off-grid and disaster supply guarantee, and intelligently switches according to the feedback of the detection module. In the disaster supply guarantee mode, important loads are preferentially guaranteed. The VSG control realizes network support, and the phase-locked loop pre-synchronization technology is combined to realize seamless switching between on-grid and off-grid. The application improves the disaster resistance, off-grid autonomy and operation reliability of the micro-grid in remote areas.

Description

Technical Field

[0001] This invention belongs to the field of smart microgrid technology, and particularly relates to a disaster-resistant smart microgrid system and control method that integrates photovoltaic and energy storage. Background Technology

[0002] In recent years, power distribution networks have faced multiple challenges related to power supply security, energy transition, and digital development. Against this backdrop, distribution networks need to ensure power supply reliability while supporting a high proportion of distributed renewable energy integration and enhancing their resilience to extreme disasters. However, power grids in remote rural areas and high-altitude mountainous regions face particularly severe challenges:

[0003] First, the terrain is complex and the climate is harsh, with frequent natural disasters such as ice and snow and freezing rain. The power distribution network has insufficient protection standards and weak disaster prevention and mitigation capabilities, which can easily lead to large-scale power outages.

[0004] Secondly, the dispersed nature of users, low load density, and long power supply distances result in large investments in power grid construction, difficulties in operation and maintenance, and low equipment utilization.

[0005] The invention patent with publication number CN119787390A provides an off-grid microgrid system and its secondary frequency regulation control method. It determines whether the system is in a frequency dead zone by acquiring the grid frequency. Within the dead zone, it adjusts the active power of all equipment units; outside the dead zone, it adjusts the active power of some equipment units, achieving stable operation of the off-grid microgrid. It focuses on frequency stability control in off-grid scenarios and introduces grid-type energy storage units to adapt to new energy access. However, it does not address the collaborative integration of multi-energy complementary resources or emergency response optimization in disaster relief scenarios.

[0006] The invention patent with publication number CN120109775A provides a method and device for coordinated configuration of photovoltaic and energy storage in rural microgrids based on a cooperative alliance. It determines the supply-demand ratio by acquiring photovoltaic and energy storage information from each microgrid, constructs upper and lower layer configuration and scheduling models, and obtains an alliance-based coordinated photovoltaic and energy storage configuration scheme. It focuses on the alliance-based optimized configuration of photovoltaic and energy storage resources in rural microgrids to improve configuration matching, but does not consider off-grid autonomous operation mechanisms under extreme disasters.

[0007] Existing technologies lack adaptability to various scenarios. Most technologies have not designed specific disaster relief mechanisms for the complex terrain and frequent snow and ice disasters in remote rural areas and plateau mountainous regions, making it difficult to meet the power supply guarantee needs under extreme disaster scenarios. Furthermore, existing technologies have not formed a complementary system covering distributed new energy sources, energy storage, and local loads, which cannot fully adapt to the characteristics of dispersed loads and long power supply distances in remote areas.

[0008] Therefore, there is an urgent need for a disaster-resistant smart microgrid system and its control method that can achieve off-grid autonomy. Summary of the Invention

[0009] The present invention aims to provide a disaster-resistant smart microgrid system and control method that integrates photovoltaic and energy storage, in order to solve the problems of weak disaster resistance, insufficient off-grid autonomy, and unstable on-grid / off-grid switching in existing technologies for microgrids in remote areas.

[0010] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0011] A disaster-resistant smart microgrid system with photovoltaic and energy storage synergy, the system comprising:

[0012] The photovoltaic power generation unit is connected to the DC bus via a Boost converter and controlled by maximum power point tracking.

[0013] The energy storage power station unit is connected to the DC bus through a Buck-Boost bidirectional converter and controlled by a voltage and current dual closed-loop control output PWM modulation wave.

[0014] The detection module unit is used to detect the power grid connection status and disaster early warning information;

[0015] The power grid unit and load unit are connected to the AC bus via DC / AC converters. The DC / AC converters are controlled by virtual synchronous generators and are controlled by SVPWM modulation waves output through a dual closed-loop voltage and current circuit. The load unit includes important load units and non-important load units.

[0016] Furthermore, the system includes three operating modes: normal grid connection, planned / fault-based grid disconnection, and disaster relief supply, and can intelligently switch between them based on feedback from the detection module.

[0017] Furthermore, when the system is in normal grid-connected operation mode, under sufficient sunlight, the photovoltaic power generation unit generates electricity to supply power to the energy storage station unit and the load unit through the DC bus; when sunlight is insufficient, the energy storage station is put into operation first, and together with the photovoltaic power generation unit, it supplies power to the load unit; when the energy storage station unit's power reaches the set margin, the grid unit and the photovoltaic power generation unit jointly supply power to the load unit.

[0018] Furthermore, when the system is in the planned / fault-off-grid operation mode, if there is sufficient light and energy storage, it will supply power to both important and non-important load units simultaneously; if there is insufficient light and energy storage, it will prioritize supplying power to important loads and stop supplying power to non-important loads.

[0019] Furthermore, when the system is in disaster relief operation mode, the disaster early warning system issues an early warning, and the system detects a grid disconnection through the grid connection detection module unit, and the system switches to off-grid operation, supplying power only to important loads.

[0020] The present invention also provides a disaster-resistant smart microgrid control method based on the above-mentioned system with photovoltaic-storage synergy. The control method includes: using a virtual synchronous generator to control a DC / AC converter, simulating the inertia and damping characteristics of a synchronous generator, autonomously maintaining voltage and frequency stability during off-grid operation, and tracking the active and reactive power of the grid during grid-connected operation.

[0021] Furthermore, the control method also includes: when switching from off-grid to grid-connected operation, a phase-locked loop is used for pre-synchronization processing, the voltage amplitude, frequency and phase of the grid are detected in real time, and the output parameters of the virtual synchronous generator controller are gradually adjusted to make them consistent with the grid parameters before the grid-connected switching is completed.

[0022] Furthermore, the phase-locked loop adopts a single synchronous coordinate system software phase-locked loop, which extracts voltage phase angle and amplitude information through Clark transformation and Park transformation to achieve synchronous control.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0024] 1. By using a parallel AC bus architecture, photovoltaics, energy storage, loads, and the power grid are organically integrated to build an efficient and flexible energy hub;

[0025] 2. Based on the detection module, determine the power grid status and disaster situation, intelligently switch to and disconnect from the grid operation mode to ensure maximum energy utilization under normal conditions and disaster situations;

[0026] 3. Adopting VSG network control enhances the system's active support capability and reduces dependence on traditional power grids;

[0027] 4. By combining phase-locked loop pre-synchronization method, seamless switching between grid connection and off-grid operation is achieved, improving operational reliability;

[0028] 5. Particularly suitable for scenarios with frequent disasters and long power supply distances, such as remote rural areas and high-altitude mountainous areas. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the equipment layer of a disaster-resistant smart microgrid system with photovoltaic and energy storage synergy according to the present invention.

[0030] Figure 2 This is a control flowchart of a disaster-resistant smart microgrid system with photovoltaic and energy storage synergy according to the present invention.

[0031] Figure 3 This is a topology diagram of the single-synchronous coordinate system software phase-locked loop structure in this invention. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] Example 1:

[0034] This embodiment provides a disaster-resistant smart microgrid system with photovoltaic and energy storage synergy, where the equipment layer is as follows: Figure 1 As shown, the system includes photovoltaic power generation units, energy storage power station units, detection module units, grid units, load units (including critical load units and non-critical load units), and various converter and transformer components. The photovoltaic-side DC / DC converter uses a Boost converter, controlled via MPPT (Maximum Power Point Tracking). The energy storage-side DC / DC converter uses a Buck-Boost bidirectional converter, controlled by a dual-loop voltage and current control output PWM modulation wave. The grid and load-side DC / AC converters use VSG (Virtual Synchronous Generator) to control the output voltage and frequency, and then control the output SVPWM modulation wave via a dual-loop voltage and current control. Critical loads include loads related to personal and public safety (medical emergency services, facility safety systems, etc.), loads that may cause significant economic losses (core production equipment, etc.), and loads important to social order (traffic, broadcasting, municipal command, etc.).

[0035] The system includes three control scenarios: normal grid connection, planned / faulty grid disconnection, and disaster relief. During normal grid connection and planned / faulty grid disconnection, the grid connection point is automatically switched on and off via the upper-level control switch.

[0036] Under normal circumstances, the system operates in grid-connected mode. When there is sufficient sunlight, the photovoltaic power generation units supply power to the energy storage power station units, load units, and grid units via the DC bus, prioritizing the stable operation of the load units and ensuring sufficient power for the energy storage power station units. When sunlight is insufficient, the photovoltaic power generation units generate insufficient power. In this case, the energy storage power station is prioritized and works in conjunction with the photovoltaic power generation units to supply power to the load units. However, to ensure disaster recovery capabilities, the energy storage power station units need to have a certain margin in their power supply. Therefore, once the energy storage power station units reach their margin limit, the grid unit works in conjunction with the photovoltaic power generation units to supply power to the load units.

[0037] When a planned / faulty off-grid situation occurs, if the disaster early warning system shows no abnormalities, the system will detect the grid disconnection through the grid connection detection module and switch to off-grid operation. Depending on the power supply status of the photovoltaic and energy storage units, there are two scenarios: 1. When there is sufficient sunlight and energy storage, the operation of important loads is guaranteed, while power is supplied to non-important loads; 2. When there is insufficient sunlight and energy storage, priority is given to ensuring the operation of important loads, and power supply to non-important loads is stopped.

[0038] When extreme situations caused by natural disasters occur, the disaster early warning system issues a warning. Simultaneously, the system detects a grid disconnection through its grid connection detection module, and the system switches to off-grid operation. At this time, the control system ensures power supply to critical loads while power to non-critical loads is stopped. The control flowchart is as follows: Figure 2 As shown.

[0039] Traditional grid-following control relies on the characteristics of the grid voltage source, passively following without providing effective support. In contrast, grid-building control actively establishes grid voltage and frequency, freeing itself from dependence on the traditional grid. It can actively maintain voltage / frequency stability, independent of grid voltage source characteristics, possessing autonomous inertia and damping regulation capabilities, stronger disturbance rejection capabilities, and flexible adaptation to both islanded and grid-connected operation modes, significantly improving the grid's capacity to accommodate new energy sources. VSG, as the core solution of grid-building control, can simulate the inertia and damping characteristics of synchronous generators, eliminating the need for additional physical inertia devices. This low-cost improvement enhances system stability margin, enabling inverters to possess inertial response and primary frequency regulation capabilities, thereby significantly improving the stability and disturbance rejection capabilities of grids with high proportions of new energy.

[0040] The equations for controlling a virtual synchronous generator include the following formulas:

[0041] ;

[0042] ;

[0043] ;

[0044] in: , These represent the input active and reactive power, respectively. , These are the reference values ​​for active power and reactive power, respectively. VSG controls the output angular frequency. This is the reference value for the output angular frequency. To control the output angle of the VSG, The virtual electromotive force of the synthesized VSG. For reference electromotive force, For virtual rotational inertia, For virtual damping, This is the reactive power voltage regulation coefficient.

[0045] When a converter using VSG control is operating in grid-connected mode, the grid voltage and frequency are strongly constrained, and the VSG's output voltage amplitude, frequency, and phase are clamped by the grid. In this case, the VSG control tracks the active / reactive power output of the grid. When operating off-grid, there is no grid constraint, and the VSG autonomously maintains voltage and frequency stability, directly supplying power to the load. Due to this characteristic, no additional control is required when switching from grid-connected to off-grid mode. However, with long-term operation in off-grid mode, due to load fluctuations, changes in reactive load, and the VSG's own control strategy, deviations in the VSG's control output frequency, voltage amplitude, and phase from the grid are inevitable. If directly connected to the grid, these deviations will generate huge inrush currents, leading to equipment damage, power outages, and other problems. Therefore, seamless switching technology is required for switching from off-grid to grid-connected mode, involving pre-synchronization processing. This involves using a phase-locked loop (PLL) to detect the grid's voltage amplitude, frequency, and phase in real time, and gradually adjusting the VSG's output parameters to align with the grid parameters. When the grid-connection threshold is met, grid-connection switching is performed, achieving seamless off-grid and grid-connection switching.

[0046] During operation, the pre-synchronization stage needs to achieve synchronization, while the phase-locked loop (PLL) has the ability to extract parameters such as the phase angle and amplitude of the voltage under test. Among these, the single-synchronization coordinate system software PLL (SSRF-PLL) has a fast dynamic response and can quickly and accurately obtain information such as voltage phase. Its structural topology is as follows: Figure 3 As shown, the three-phase voltage on the AC side of the DC / AC converter , , After Clark transformation, the two-phase stationary coordinate system is obtained. , shaft voltage , The d-axis and q-axis voltages in a two-phase rotating coordinate system are obtained through the Park transformation. , The voltage and phase angle information can be obtained through PI, summation, and integration. Once the voltage, frequency, and phase angle in the off-grid operation state are consistent with those of the grid, the system is switched to grid-connected operation. The Clark transform and Park transform formulas are shown below, where... This is a phase angle reference value.

[0047] ;

[0048] .

[0049] Example 2:

[0050] This embodiment is based on embodiment 1. The photovoltaic module and inverter can be extended to a combination of new energy sources such as photovoltaic-wind power, photovoltaic-hydro power, and photovoltaic-wind power-hydro power.

[0051] DC / AC converters can use virtual synchronous generators to achieve grid control, and can also use traditional grid control strategies such as droop control.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A disaster-resistant intelligent micro-grid system with light storage synergy, characterized in that, The system includes: The photovoltaic power generation unit is connected to the DC bus via a Boost converter and controlled by maximum power point tracking. The energy storage power station unit is connected to the DC bus through a Buck-Boost bidirectional converter and controlled by a voltage and current dual closed-loop control output PWM modulation wave. The detection module unit is used to detect the power grid connection status and disaster early warning information; The power grid unit and load unit are connected to the AC bus via DC / AC converters. The DC / AC converters are controlled by virtual synchronous generators and are controlled by SVPWM modulation waves output through a dual closed-loop voltage and current circuit. The load unit includes important load units and non-important load units. Furthermore, the system includes three operating modes: normal grid connection, planned / fault-based grid disconnection, and disaster relief supply, and can intelligently switch between them based on feedback from the detection module. 2.The disaster-resistant intelligent micro-grid system of claim 1, wherein, When the system is in normal grid-connected operation mode, under sufficient sunlight, the photovoltaic power generation unit generates electricity to supply power to the energy storage station unit and the load unit through the DC bus; when sunlight is insufficient, the energy storage station is put into operation first, and together with the photovoltaic power generation unit, it supplies power to the load unit; when the energy storage station unit's power reaches the set margin, the grid unit and the photovoltaic power generation unit jointly supply power to the load unit. 3.The disaster-resistant intelligent micro-grid system of claim 1, wherein, When the system is in the planned / fault-off-grid operation mode, if there is sufficient light and energy storage, it will supply power to both important and unimportant load units simultaneously; if there is insufficient light and energy storage, it will prioritize supplying power to important loads and stop supplying power to unimportant loads. 4.The disaster-resistant intelligent micro-grid system of claim 1, wherein, When the system is in disaster relief operation mode, the disaster early warning system issues an early warning, and the system detects a grid disconnection through the grid connection detection module unit. The system then switches to off-grid operation and supplies power only to critical loads.

5. A disaster-resistant smart microgrid control method based on the photovoltaic-storage synergy of the system described in any one of claims 1 to 4, characterized in that, The control methods include: using a virtual synchronous generator to control the DC / AC converter, simulating the inertia and damping characteristics of a synchronous generator, autonomously maintaining voltage and frequency stability during off-grid operation, and tracking the active and reactive power of the grid during grid-connected operation.

6. The disaster-resistant intelligent micro-grid control method of claim 5, wherein, The control method also includes: when switching from off-grid to grid-connected operation, a phase-locked loop is used for pre-synchronization processing, the voltage amplitude, frequency and phase of the grid are detected in real time, and the output parameters of the virtual synchronous generator controller are gradually adjusted to make them consistent with the grid parameters before the grid-connected switching is completed.

7. The disaster-resistant intelligent micro-grid control method of claim 6, wherein, The phase-locked loop adopts a single synchronous coordinate system software phase-locked loop, which extracts voltage phase angle and amplitude information through Clark transformation and Park transformation to achieve synchronous control.

Images