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Improved droop method for grid connection control in micro grid system
As an emerging power system architecture, Microgrid aims to improve the flexibility and reliability of the power system. It is characterized by the integration of multiple distributed energy sources (such as solar, wind, and storage devices) and the ability to switch between grid-connected and island modes. In order to effectively Control the distributed generating units in the micro grid and ensure the stability and power sharing of the grid, Droop Control has become an important control strategy for grid connection. This paper will discuss the application and advantages of improved droop method in micro-grid system.
micro grid and its control requirements
Microgrids have the ability to operate autonomously and manage themselves, and usually consist of a variety of distributed generation devices, energy storage systems, and loads. Compared with traditional power grids, micro grids have greater flexibility and complexity in control and management, and mainly face the following challenges:
Power coordination: Multiple power generation devices share the system load and need to achieve reasonable power distribution.
Frequency and voltage control: Ensure that the frequency and voltage of the power grid are within the rated range to ensure the stability of the system.
The instability of renewable energy: the output power of renewable energy such as photovoltaic and wind energy fluctuates greatly, and its impact on the grid needs to be effectively controlled.
the basic principle of droop method
Droop method is a kind of strategy widely used in grid-connected control, mainly used in reactive power and frequency control. This method realizes the cooperative control among distributed generation units (DERs) by setting the relation between generator output power, system frequency and port voltage.
Power and frequency relation
In the droop method, the output power of the generator will be adjusted with the change of the frequency of the micro-grid. When the system frequency decreases (load increases), the output power of the generator will increase; On the contrary, when the frequency rises (the load decreases), the output power of the generator will decrease. This adjustment is similar to the droop characteristic of a traditional generator.
Voltage and reactive power relationship
In addition, the droop method can also be used to control voltage. In the output of reactive power, the droop characteristic can also be used to adjust the voltage, such as when the power grid is low, the generator automatically increases the reactive power output to increase the voltage, and vice versa to reduce the reactive power output. This method enables the individual power generation units in the microgrid to automatically adjust to meet the overall power balance and voltage requirements of the system.
improve the characteristics and advantages of droop method
Enhanced dynamic response capability
By introducing intelligent control algorithms (such as fuzzy control, PID control, etc.), the improved droop method significantly enhances the response ability of the system to transient load changes, can adapt to load fluctuations and changes of renewable energy more quickly, and improves the dynamic performance of the micro-grid.
Improved power sharing accuracy
The traditional droop method may lead to unbalanced load distribution among generating units in power sharing. The improved sag method introduces online measurement and prediction technology, which can monitor the status of each power generation unit in real time, and achieve more balanced power sharing through optimization algorithms (such as optimal control strategies).
Coordinated control of frequency and voltage
The improved droop method can combine the frequency response and voltage control strategy to form a joint coordinated control system. When the system is disturbed, the power and reactive power output of the generator can be adjusted at the same time to ensure that the frequency and voltage are within the safe range and effectively improve the stability of the system.
Easy to expand and integrate
Because the improved droop method has strong adaptability, it can quickly integrate new distributed power generation units and energy storage systems, support the flexible expansion of micro-grid, and reduce the complexity of system design.
typical examples
Urban micro grid
The micro grid of a city integrates photovoltaic power generation, wind energy and energy storage devices, and adopts the improved droop method to control, achieving a power utilization rate of more than 95%, and effectively reducing power fluctuations during peak consumption.
Rural electrification projects
In remote rural electrification projects, micro-grids have significantly improved the reliability of power supply by improving the sag method to control access to renewable energy, solving the problem of local power shortage.
Medical facility micro-grid
A medical institution relies on micro-grid to ensure the power supply of important clinical equipment, and improves the application of sag method in power flow and frequency control, so that the entire system remains stable when the load changes.
conclusion
As an effective control scheme for micro-grid connection, improved sag method has become one of the key technologies in the design and implementation of micro-grid because of its good dynamic response ability, power sharing accuracy and structural flexibility. With the continued development of renewable energy, future microgrids will be supported by improved ptosis to achieve more efficient and smarter power management, contributing to the achievement of sustainable development goals. Through further research and technological innovation, the improved droop method is expected to promote the development of micro-grids in a wider range of application scenarios.
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