Research On System Planning And Collaborative Control Of Single-phase Electric Springs

As the environmental problems caused by carbon emissions have received increasing attention,the proportion of new energy power generation based on solar and wind energy is increasing.However,due to its intermittent and unstable characteristics,microgrid have been brought about voltage and frequency fluctuations during operation.The mainstream method is using the energy storage system to stabilize the power imbalance in the microgrid,but if it is completely dependent on the centralized energy storage unit for regulation,it is not only expensive,but also inflexible in control.As an emerging demand-side management device,Electric Springs(ES)can be dispersedly installed in various nodes in the microgrid to support the system,realizing the automatic matching of power consumption and power generation.The research in this paper is to solve the problems faced by ES applied in microgrid,mainly including system planning and collaborative control.The specific research work is as follows:(1)The topic background and research significance of this paper are elaborated,and the research status of ES is analyzed from the topology,planning configuration and control strategy.The research object is determined to be the second-generation ES topology,and the research focus of this paper is drawn.(2)An ES planning model in microgrid considering the access of photovoltaic energy storage is proposed.First,the improvement effect of ES on energy storage after being connected to the microgrid has been theoretically analyzed.Then,from the perspective of the operator,taking the minimum daily operating cost of the system as the objective function,the Distflow power flow model is established according to the adjustment characteristics of the smart load,and the second-order cone technology is used to convex and relax the nonlinear constraints in the model.Finally,the model is solved and verified on the MATLAB simulation platform based on the modified IEEE-33 node system,and the rationality of the proposed ES planning model is analyzed in different scenarios.(3)The power control of single ES is studied,first,the time domain model and the s domain model of the ES are established to analyze the closed-loop control characteristics of the ES,and the inner loop of the filter capacitor voltage is added to ensure that the output voltage tracks the given voltage.Then,from the perspective of ES transfer and control grid-side active power input,the principle of the existing power decoupling control is studied,and the filter capacitor voltage inner loop is combined as the bottom layer control of ES,paving the way for the collaborative control of multiple ESs.Finally,the feasibility of single ES power control strategy is verified based on the MATLAB/Simulink simulation platform.(4)The collaborative control of multiple ESs is studied,and the application scenario is that the microgrid is in island operation,which contains renewable energy power generation.First of all,the voltage given problems encountered by distributed ESs in independent operation are analyzed.To solve this problem,droop control is introduced on the basis of power control,so that multiple ESs can achieve a coordinated operation state in the process of adjusting the voltage.At the same time,a frequency loop is added to suppress the fluctuation of the system frequency.In order to further optimize the reactive power output of ESs,reactive-power consensus control strategy of multiple ESs is proposed,so that ES can share the reactive power demand of the system proportionally according to its own rated power.Finally,the correctness of the two collaborative control strategies was verified on the MATLAB/Simulink simulation platform and the experiment platform of multiple ESs.(5)A hardware experimental platforms of multiple ESs have been built.The system is controlled based on the RTU-BOX development platform and TMS320F28335 DSP processor.The main modules include a microgrid simulator,3 groups of single-phase ES and the single-phase PWM rectifier which is used to be the DC side power supply of ES.Among them,the PWM rectifier adopts the voltage and current double closed-loop control strategy,and the microgrid simulator is used to simulate the frequency deviation caused by the system active power mismatch in practice.Finally,the performance of each module was tested in hardware to ensure the reliability of the experimental platform.