Modes And Strategies For Flexible Resources On The Demand Side To Participate In Grid Frequency Modulation Control

Frequency is an important indicator of power quality.In recent years,large-scale intermittent renewable energy grid-connected,its randomness and fluctuation have impacted the frequency stability of power system.It is difficult to adjust the frequency only by relying on traditional generators.The application and development of communication and automatic control technology in power system provide an opportunity for demand side flexible resources to participate in power grid frequency modulation.In this paper,the air conditioning load and electric vehicle are taken as the research objects.The FM principle and model of flexible resources,the optimal capacity allocation of primary and secondary FM control are studied.Firstly,the principle of demand-side flexible resources participating in power grid frequency modulation is expounded.The model of air conditioning load and electric vehicle frequency modulation access is introduced,and the initial state of air conditioning and electric vehicle load group is simulated by Monte Carlo method.An aggregator management mechanism is proposed,in which the aggregator is used as a unit to control the flexible resources on demand side hierarchically and regionally.The flexible resources within the aggregator can be tuned through the conversion among Idle,Load and Power modes.Then,a primary frequency modulation control strategy based on frequency droop control is studied.Flexible resources are adjusted by frequency sag to control the frequency deviation of spontaneous response.The control process does not need to consider the allocation of FM capacity of flexible resources within the aggregator.It has high efficiency and rapidity.For electric vehicles,variable droop control coefficient and forced charging area control strategy are introduced to meet the travel needs of the next day while FM is used.An aggregator dynamic frequency modulation evaluation method is used to evaluate the aggregator’s frequency modulation capability at all times.The strategy is simulated with MATLAB/Simulink,and the validity is verified.Finally,an optimal capacity allocation strategy is adopted to optimize the secondary frequency modulation under the time-sharing tariff mechanism.The strategy takes aggregator as unit,determines the range of FM capacity according to the given FM instruction and allowable deviation of power grid,and introduces temperature and SOC weight coefficient to allocate FM capacity to various flexible resources.The objective function covering FM gain,temperature variance and SOC variance is constructed by linear weighting method,and solved by particle swarm optimization combined with optimization strategy.It is verified that the strategy can improve the revenue while taking into account the user’s electricity demand.