Research On Control Strategy Of The Smooth Switching And Islanding Detection In Micro-grid

Micro-grid is the direction of using new energy sources, research on its operational control technology has important significance to improve the utilization of new energy and increase the flexibility and stability of micro-grid. Micro-grid smooth switching and islanding detection technology are important part of micro-grid control technology, so this paper based on hybrid micro-grid composed of photovoltaic generation and energy storage system as the research object, mainly studied micro-grid smooth switching and islanding detection control technology.Firstly, The control theory and mathematical models of photovoltaic power supply and battery were analyzed, this paper constructs the dynamic simulation model of photovoltaic power control model and storage battery charging and discharging control circuit by MATLAB/Simulink, achieves photovoltaic power maximum power tracking and battery constant voltage charging or discharging control.Secondly, This paper introduces the micro-grid operation mode and control strategy, analyzes the inverter control circuit and mathematical models. Import the proportional resonance into current inner loop control, makes control block diagram simpler, enhance the grid voltage interference resistance, and eliminates the coordinate transformation and power decoupling control.Then, This paper studies on smooth switch of hybrid micro-grid composed of PV and energy storage system, imports state follower reduced the oscillation in the process of switching. This paper studies on the order of switching controller and load shedding by simulation, and introduces3area smooth switching control strategy into hybrid micro-grid, the simulation result fully proves that this strategy can reduce the frequency oscillation of load shedding effectively.Finally, Based on study on the principle of islanding detection, this paper improve active power-voltage feedback disturbance detection algorithm, sets the output active power of inverter as the positive feedback function of difference between voltage of PCC and rated voltage. This paper carries on comparative study with reactive power-frequency feedback disturbance detection algorithm, analyzes detection principle and designs control parameter, the simulation result is presented lastly.Through theoretical analysis and simulation, proportional resonant current inner loop controller of photovoltaic power has strong ability against power grid voltage interference; state follower and3area load shedding control strategy can effectively reduce the switching transient oscillation in the switching process of micro-grid; the active positive feedback disturbance voltage island detection algorithm has small influence on grid power quality, no detection blind area. The research result of this paper has certain reference value for micro-grid operation control.