| With the constant development and utilization of clean energy,Micro-grid technology has become a hot issue of current concern.Micro-grid is the use of micro-power,power electronic devices and a variety of control equipment and energy storage devices combined,micro-grid can be independent of the large power grid to run alone.Due to the small size of the micro grid,the inertia of the system itself is also relatively small,vulnerable to the impact of load fluctuations,so in this case,in the face of a variety of greater volatility of the trend,the corresponding relay protection As well as the trend control more difficult.With the rapid development of various energy storage technologies,it provides a set of effective measures and means to solve the current control problems in the micro grid.Among the various forms of energy storage,the storage battery has been widely used as a form of energy storage.The fundamental reason why the battery is widely used is due to its low cost.In the current Micro-grid development process,the power balance has a decisive factor.In this paper,the battery as the main research object,focusing on micro-grid in the independent operation of the mode,the constant power control mode of the entire micro-grid control,the focus of this paper is to propose an effective constant-power charging control program to establish A set of effective constant power control strategy.In order to study the constant power control model of the battery in the microgrid,this paper first establishes a mathematical model based on the three-phase voltage-mode PWM transformer.The mathematical model of the three-phase stationary system and the dq rotating system,respectively,under different coordinate systems The constant power control model is deduced.Based on this,the model is controlled according to the feedforward decoupling control method,and SVPWM space vector method is introduced to optimize the control performance.In order to study Fractional PID control algorithm for battery charging and discharging system of constant power control effect,we study the theory and method of controlling Fractional PID control,and design of fractional PID controller.The results showed that fractional PID control method works better compared to integer order control method.In order to verify the supporting role of the battery energy storage system in micro-grid power,Micro-grid model designed to wind turbines,diesel power systems and battery energy storage system for the body.And its grid-independent operation switch and circumstances were simulated results show that the storage system can be effective in maintaining the balance of power within the system.Multi-pulse AC-DC converter technique is one of the most effective method of harmonic elimination in high power rectification system,and because of higher efficiency for harmonic elimination,better electromagnetism compatibility and reliability,its has been drawn more and more attention.With the increase in requirement of power quality and application of a large amount of nonlinear load,seeking a harmonic elimination method with lower cost and higher efficiency to combine the multi-pulse AC-DC converter technique has become a necessity.In order to improve efficiency of harmonic elimination and depress the system cost,this paper will analyze the harmonic elimination of multi-pulse AC-DC converter at dc side according to the current relation between ac and dc side,including optimal design of delta-connected autotransformer,mechanism of harmonic elimination of dc-side,passive harmonic elimination and active harmonic elimination along with the comparison between them. |
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