Research On Hierarchical Frequency Control Strategy Of Web Of Cell Architecture Based On Multi-agent Technology

The advantages of distributed energy in solving the energy crisis and environmental pollution make it have good development prospects.However,due to intermittent,random and other characteristics,the large scale integration of distributed energy will cause many problems in safe and stable operation of power grid.In order to cope with future high proportion of distributed energy,the web of cell(Wo C)architecture was proposed in CIRED 2015,which divides the power system into many cells.The cells can achieve regional autonomy and coordinate with neighboring cells to achieve power global optimization.In this thesis,to realize the ideas of "independent autonomy" and "divide and rule",the multi-agent technology is used to design the system structure and communication architecture of WoC,and four-layer frequency control strategies are researched to improve the capabilities of frequency regulation and power flow optimization and to reduce the costs.Meanwhile,problems such as system inertia decline,lines congestion and topology reconstruction,caused by large scale integration of distributed energy in power system are also studied.According to current research progress,the features and the advantages of Wo C architecture are analyzed firstly.Then the WoC architecture and the centralized control architecture,cells and microgrids,cells and active distributed networks(ADN),and the four-layer frequency control structure and the traditional three-layer frequency control structure are compared respectively.Based on these comparisons,the whole structure and each agent structure for the Wo C architecture are constructed by the multi-agent technology.Furthermore,the relationships among agents are analyzed,and the multi-agent communication frameworks for the four-layer frequency modulation are designed.Based on the multi-agent system,specific strategy for each layer in the fourlayer frequency modulation is proposed to solve the problems such as line congestion caused by high proportion distributed energy grid connection under the Wo C architecture.To improve the system inertia response and achieve frequency stability quickly,for the local frequency modulation constituted by the first layer-inertial frequency control(IFC)and the second layer-frequency containment control(FCC),the fuzzy control strategy is applied after analyzing the effects of parameters on the comprehensive inertial control.Considering the frequency control results under different universe and different disturbances,an adaptive fuzzy controller with variable universe is designed.The coupling between speed and frequency is established and the overdependence on parameter setting and universe setting is solved.To limit the frequency deviation of the local control in the safety range and eliminate the potential risk,the ratio consistent algorithm is selected for the frequency modulation inside the cell.Since the algorithm can only solve the single balanced target,the improved strategy is proposed and applied to the line congestion management in cells.Thus the line power flow can satisfy the Kirchhoff law without exceeding the maximum value of the line allowable flow.At the same time,the Lagrange dual method is adopted to achieve the power flow optimization.Through the autonomously switching between the frequency control and the configuration optimization,the goal of the third layer-the balance restoration control(BRC)in cells is archived.For the fourth layer-the balance steering control(BSC),on account of the distributed structure among cells and high proportion distributed energies,the graph theory algorithm is adopted to adapt the complex topology in Wo C architecture.The objective function of the power flow optimization among cells is formulated,and the graph theory model of multi-cell system is constructed.By analyzing the shortcomings of the Busacker-Gowan algorithm in terms of complexity,a distributed minimum cost flow algorithm is proposed.Then the optimal scheduling of the active power among cells is realized,and the problems of lines congestion and topology reconstruction are effectively solved.