| The excessive exploitation and unscientific use of fossil fuels have made energy shortage and environmental pollution increasingly prominent.At the same time,wind power generation and photovoltaic power generation have strong randomness and intermittence,and their consumption problems are also increasingly prominent.Combined cooling,heating and power micro-grid combines cogeneration technology with micro-grid technology integrating wind and solar and battery energy storage(BES).It has the advantages of clean and pollution-free,high energy utilization efficiency and reliable energy supply.It is an effective means to solve the above problems.At the same time,considering that industrial energy consumption accounts for the largest part of energy consumption,the planning and construction of the micro-grid of combined cooling,heating and power supply in the industrial park can better promote energy conservation and emission reduction,and help achieve the goal of "double carbon" in an orderly manner.Under this background,this paper takes the combined cooling,heat and power micro-grid for energy supply in industrial parks as the research object,and focuses on four aspects of the on-grid optimal scheduling,off-grid optimal scheduling,parallel / off grid switching control and off grid operation frequency control of source-load-energy storage(ES)in the micro-grid,.The work of the paper are as follows:1.This paper studies how to optimize the scheduling of BES accident standby and manage the battery grading process in on-grid operation.Firstly,taking the battery production industrial park as the research object,the grading energy storage model and the scheduling model of energy supply equipment in the park are constructed;Then,a calculation method of unplanned off-grid probability considering weather conditions,load rate level and off-grid type is proposed,and the off-grid risk is quantified combined with the calculation method of important load loss;On this basis,taking into account the benefits of BES reserve participating in on-grid scheduling and the risks brought by off-grid operation,the optimal scheduling method of BES accident standby considering the off-grid risk and the optimal scheduling method of BES accident standby considering the off-grid risk and the energy management of the grading battery are proposed successively.The simulation analysis shows that the proposed method can realize the effective utilization of the battery energy storage accident standby under different conditions and the reasonable arrangement of the battery grading process,and can effectively reduce the system operation cost with less risk.2.This paper studies how to reasonably switch the secondary load in the off-grid state,so as to effectively improve the source load matching degree and energy utilization efficiency.Firstly,the secondary load importance evaluation index and source-load complementarity evaluation index are defined.Then,considering the importance of load and the complementarity of source-load,and calculating their weights by entropy weight method,the comprehensive evaluation index of secondary load is constructed.On this basis,load switching strategies based on single time scale energy supply and comprehensive indicators and load switching strategies based on multi-time scale energy supply and comprehensive indicators are proposed successively.The simulation analysis shows that the proposed method can not only make full use of the limited energy of the off-grid system to improve the load supply,but also significantly reduce the frequency of load switching and ensure the continuous and stable energy supply of as many loads as possible.3.The problem of frequency control under off-grid operation is studied.Taking the photovoltaic/ BES / gas turbine micro-grid under master-slave control mode as the research object,taking BES as the main control unit,a coordinated control strategy of gas turbine/BES based on model predictive control and low-pass filter algorithm is proposed.Taking the gas turbine as the main control unit,a layered coordinated frequency control strategy based on model predictive control and low-pass filter algorithm is proposed.In the hierarchical coordination control,the upper layer continuously adjusts the power output plan through model predictive control to reduce the source load power deviation.At the same time,the low-pass filter algorithm is used to make the gas engine bear the low-frequency disturbance component,which avoids the frequency fluctuation caused by the slow response speed of the gas engine;The bottom layer dynamically adjusts the BES output through virtual droop/inertia control and state of charge(SOC)self recovery control,and cooperates with the gas engine to participate in frequency modulation.The simulation analysis shows that the proposed method can not only effectively reduce the frequency fluctuation of the system,but also follow the SOC plan curve or the best curve of the BES,so as to ensure that the off-grid system can operate continuously and stably according to the energy supply plan.4.The problem of smooth switching control in the process of switching from on-grid to off-grid is studied.Firstly,a step-by-step load shedding method considering the constraints of BES ratio characteristics is proposed.In the off-grid step-by-step load shedding process,the high rate discharge of BES is used to support the remaining uncut load for a short time.Then,a dynamic PQ control method of BES based on virtual droop / inertia control is proposed.which assists the main control unit to adjust the voltage by dynamically adjusting the BES output.On this basis,an unplanned off-grid smooth switching control strategy considering the BES ratio characteristic constraint and dynamic PQ control is proposed.Simulation analysis shows that the proposed method can not only ensure that the voltage is always maintained at a high level during the switching process,but also significantly reduce the voltage fluctuation,which is conducive to the smooth transition of the switching process and improve the power supply reliability.5.The auxiliary decision analysis software of multi-scenario optimization regulation is developed.The functions of the software are as follows: Optimal scheduling scheme formulate considering off-grid risk and grading battery energy management under on-grid scenario;Load optimization switching scheme formulate considering load importance and source load complementarity in off-grid scenario;Energy(rolling)optimal scheduling and load optimal switching scheme formulate under unplanned off-grid scenario;Switching control simulation considering BES rate characteristics and dynamic PQ control in on / off grid switching scenario;Gas turbine/ BES layered coordinated control simulation based on model predictive control and low-pass filter algorithm under off-grid operation scenario;Data analysis covering off-grid operation loss,on-grid operation income and BES reserve utilization depth.The software is easy to operate and has strong expansibility.It can provide a good basic platform for scientific and technological workers to study the optimal control of multi-scenarios of combined supply micro-grid. |
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