Research On Multi-objective Optimization Design And Coordinated Control Of Distributed Generation And Microgrid

Energy is an important material basis for human survival and development, concerning the national economy, people’s livelihood and national security, which is also the primary area of scientific and technological innovation service and application. However, the irrationality of energy structure and low efficiency of energy utility in our country has brought a number of environmental and social issues. Distributed generation technologies help to promote the use of clean energy and renewable energy, improve energy efficiency and energy supply structure, ensure the safe and reliable energy supply. However, the access of large-scale distributed generation make power system operation face many new problems and challenges. Microgrid that is an effective way to integrate advantages of various distributed energy resources, weaken the adverse impact of distributed generation on the grid and fully tap the comprehensive benefits of distributed generation, has become a hot topic and an important development direction of distributed generation research field. This article focuses on multi-objective optimization design and coordination control of distributed generation and microgrid, including distributed generation multi-objective planning, microgrid capacity multi-objective allocation, microgrid small-signal modeling and transient simulation, microgrid coordination control and its optimization method as well as the coordination control of microgrid with non-linear and unbalanced loads. The detailed research contents are summarized as follows:For the planning problem of distributed generation integration to the grid with low penetration, three minimization optimization objective functions of investment and running costs, system active power loss in the network and load node voltage offset are built. Multi-objective chaotic quantum genetic algorithm (MCQGA) that integrates real-coded quantum genetic algorithm and multi-objective optimization strategy is proposed and its progressiveness is verified through algorithm performance tests. The multi-objective optimization problem that distributed generations integration to the IEEE30nodes power system is solved based on MCQGA. The effectiveness of the proposed algorithm is confirmed by example analysis and the corresponding software application platform is developed. As efficient energy organization form of distribution generation integration to the grid with high penetration, microgrid capacity allocation is the premise of the microgrid operation control. Based on the analysis of power external characteristic of various distributed generations in microgrid, microgrid capacity is configured considering economic cost, power supply reliability and environmental benefits. Combined with multi-objective genetic algorithm and chaotic optimization techniques, chaotic optimization multi-objective genetic algorithm (CMGA) is proposed and verified its advancements through algorithm performance tests. The example analysis shows that the allocated microgrid based on CMGA ensures the power supply reliability, saving the economic cost and reducing environmental pollution. The software application platform based on related research has been developed.Microgrid stability mechanism and operation mechanism is the basis of the micro-grid operation control. On the basis of the full-order small-signal dynamic model of microgrid including distributed generation model, network model and load model, the effectiveness of control parameters, line impedance and loads on the system steady-state and dynamic performance is analyzed based on eigenvalue and sensitivity. The microgrid hierarchical control structure principle is revealed, which lays the theoretical foundation for optimization design of microgrid topology and control parameters. The microgrid time domain transient simulation model is built based on MATLAB/SIMULINK and the simulation of various operating modes and mode switching is conducted, which reveals microgrid operation mechanism and verifies the accuracy of the small-signal modeling and analysis.Microgrid coordination control problem is one of the core issues. Microgrid coordinated control strategy is designed and the optimization value ranges of microgrid control parameters are analyzed based on small-signal dynamic model of microgrid. The precise optimization objective functions of microgrid control are built through time-domain transient simulation and data acquisition of microgrid in professional software PSCAD/EMTDC. The main parameters of coordination control strategy are optimized based on the niche genetic algorithm, improving the steady state and dynamic performance of microgrid in different operating modes and mode switching.Power quality of microgrid is directly related to the stability and economic operation of microgrid. For the different types of local load in microgrid, the three local control strategies of DG:output voltage harmonic control strategy, the output current harmonics control strategy and load current harmonics control strategy are designed based on the proportional integral resonant controller, in order to achieve different power quality control goals. Under power quality requirements of the different operating modes, the coordination control strategy of microgrid with nonlinear and unbalanced loads is proposed, coordinating local control strategies of DG, not only to ensure the power quality of microgird bus and injected into the grid, but also to achieve the economic operation and smooth switching of microgrid.The main innovations of this thesis highlight:(1) The multi-objective chaotic quantum genetic algorithm and chaos optimization multi-objective genetic algorithm are developed to solve distribution generation multi-objective planning and microgrid capacity multi-objective allocation problems, overcoming low efficiency of the single objective optimization algorithm and the blindness of weighted solving, realizing the multi-objective optimization design of distributed generation and micorgrid in the true sense. Note that the capacity allocation of the combined with cooling, heating and power (CCHP) supply system is taken into account for the first time.(2) the full-order microgrid small signal dynamic model which has universal applicability and can be arbitrarily extended is established and the impacts of the control parameters, line impedance and the load on the steady-state and dynamic performance of microgrid are analyzed. Combined with time domain transient simulation of microgrid in various operating modes as well as switching mode, the stability mechanism and operation mechanism of microgrid are revealed.(3) the coordination control strategy of microgrid is designed and the steady state and dynamic performance of microgrid in various operating modes as well as switching mode has been effectively improved through the integration of the small-signal dynamic model analysis, time domain transient simulation and artificial intelligence algorithms for the first time.(4) The novel coordination control strategy of mcirogrid with non-linear and unbalanced loads is proposed, ensuring DG’s effective output at the base frequency band and harmonics management at high frequency band. Moreover they are coupled between each other. The coordination control strategy not only ensures the power quality of microgird bus and injected into the grid, but also achieves the economic operation and smooth switching of microgrid.