| In today’s society,with the rapid economic development and population growth,the demand for electricity and fresh water is increasing worldwide,especially in remote and isolated islands,which usually rely only on diesel generators to meet the demand for electricity and power desalination systems,but the high fuel consumption and low energy conversion rate of diesel generators make them costly and waste too much energy.With the development of wind/solar power technology,a system using wind/solar power technology combined with diesel generators has become a better choice for obtaining electricity and fresh water in isolated islands today.Facing the problems of excessive input cost,low energy conversion rate and unreasonable utilization of resources,this paper proposes a wind/solar/diesel hydropower co-generation system,and in order to reasonably set the configuration of each distributed energy source,the capacity optimization of the proposed system is based on genetic algorithm.the unstable change of load in the hydropower co-generation system and the inertia reduction of the system caused by the addition of new energy sources such as wind/solar make the therefore,the study of the frequency characteristics of the hydropower co-generation system becomes a necessary research content.Based on this,the main research contents of this paper are as following:Firstly,a wind/solar/diesel hydropower co-generation system is proposed to address the disadvantages of short battery life,frequent replacement and post-treatment difficulties,as well as the waste of diesel generator exhaust energy,and the working principle of each sub-system is analyzed,and the mathematical model of energy conversion of the whole system is established.The multi-objective optimization of the annualized cost and renewable energy share of the system based on genetic algorithm is carried out,and the effects of diesel price,PV panel price and wind turbine price on the optimization objectives of annualized cost and renewable energy share are analyzed.Secondly,to address the problem of unstable system operation caused by sudden changes in system frequency due to load changes in the wind/solar/diesel hydropower co-generation system,the control method of the double-fed induction generator involved in system frequency regulation in the system is improved,so as to improve the system frequency regulation capability.The maximum power point tracking and the over-speed control and the pitch angle control of the load reduction control method of the double-fed induction generator are studied.The wind speed region is divided and the applicability of load shedding control in different wind speed regions is pointed out.The effects of the over-speed control and pitch angle control on the speed,output power and pitch angle of the double-fed induction generator are analyzed.Finally,the principle of primary frequency regulation of the system is analyzed,and based on the traditional research of virtual inertia control and droop control,a multi gain droop control strategy for primary frequency regulation of double-fed induction generator is proposed to determine different droop coefficients according to the offset of frequency to improve the frequency regulation of double-fed induction generator.Based on the MATLAB/Simulink platform,a wind/solar/diesel power generation model is built to compare the frequency regulation effects of the multi-gain droop control strategy,the fixed coefficient control strategy and the no-addition control strategy under different wind speed conditions.The simulation results show that the multi-gain droop control strategy has significantly improved the control effects in terms of frequency,speed,output power and pitch angle. |
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