Control Method For Application Of PEVs To Frequency Regulation Of Power System

Eiffcient use of wind and solar and other renewable energy is an important means to solveenergy and environmental problems, due to it can save energy and reduce dependence onfossil fuels. However, due to its randomness, a large number of wind power and photovoltaicpower generation connected to the grid will lead to a series of problems of frequencyfluctuations. Due to its good storage characteristic, plug-in electric vehicles (PEVs) can act as abackup when the output of the renewable energy is fluctuations; so it can balance thefrequency fluctuations caused by the randomness of the renewable energy. So, the study of theeffective use of the large number of geographically dispersed PEVs involved in the powersystem frequency regulation through technology of vehicle-to-grid (V2G) has importanttheoretical and practical significance.Obtaining the accurate frequency signal is an important prerequisite and foundation forPEVs participating in the frequency regulation of the power system. For the inadequate ofcentralized and decentralized acquisition methods, a collaborative acquisition method ofdistribution system frequency based on consensus filtering is proposed, where onlyfrequency-measuring devices at distribution substations are utilized. Limited communicationbetween neighboring PEVs/distribution substations can facilitate consistent, robust andaccurate acquisition system frequency signal for all PEVs. Convergence and robustness ofcollaborative acquisition method are proved by the theoretical analysis. Compare with thedecentralized acquisition method, simulation results shows that the collaborative acquisitionmethod can improve system robustness, eliminate noise and reduce device costs.V2G dynamic model based on feedback control is proposed by consideringcharge/discharge characteristics and SOC constraints of the PEV battery. In order to analysisthe frequency regulation of the power system based on V2G, power system frequencyregulation model including PEVs is proposed by incorporating V2G dynamic models of allPEVs into the system dynamic model. Frequency signal acquisition of each V2G is relied onthe proposed method. The SIMULINK results demonstrate that PEVs participating in thesystem frequency regulation based on the collaborative acquisition method can achieve betterresults and be a good response to short-circuit fault.In order to achieve PEVs participating in the system frequency regulation, two aspectsincluding PEVs frequency collaborative acquisition and V2G output adjustment according tothe frequency obtained are need to achieve through hardware circuit. Therefore, PEVscollaborative frequency acquisition circuit and V2G power adaptive frequency adjustmentcircuit are developed. PEVs collaborative frequency acquisition circuit can ultimately obtain a consistent, accurate frequency signal, via communication with the power distributionsubstation or neighboring PEVs through the wireless communication unit. PEV frequencyadaptive power control circuit contains the frequency tracking loop and power control loop.The frequency tracking loop can achieve real-time tracking of grid frequency through theregulator, the correction circuit and a feedback circuit. The power control loop can achieveadaptive V2G power of PEV through the instantaneous power calculating unit, Clarketransformation sector selector, hysteresis comparator, switch tables, the comparator andmultipliers.The two circuits can be able to achieve large-scale, distributed PEVs forparticipating frequency regulation and it can also provide technical support.