Battery Energy Storage Station Active Support Control Scheme And Its Regulating Frequency Performance For Grid

A high proportion of new energy connected to the grid is the key to improving the energy structure and accelerating the transformation of the grid.However,a large number of power electronic devices in wind power and photovoltaic farms rarely have inertial characteristics and damping characteristics,resulting in serious support for the frequency and voltage stability of the new energy system.In recent years,the flexibility of large-scale energy storage systems to handle energy has become a new frequency modulation and voltage regulation method for power systems,especially the development and utilization on grid-connected control technology and frequency regulation capabilities of large-capacity electrochemical energy storage with short response time and stable energy supply highly concerned.This topic has conducted in-depth research on the grid-connected control strategy of the battery energy storage power station and its participation in the frequency modulation process of the power grid at multiple time scales.First,the overall modeling process of the battery energy storage station is described,including the battery pack model,the active support control model and the charge and discharge management model.This paper proposes an active support control strategy for battery energy storage station based on the third-order model of the synchronous machine.This strategy can be equivalent to an energy storage converter as an approximate synchronous voltage source with an excitation system and a speed regulation system.The weakly damped new energy power system provides the necessary inertia characteristics and damping characteristics.Through the DigSILENT/PowerFactory simulation software to build a four-machine and two-zone simulation system,a comparative analysis of the frequency modulation and voltage regulation capabilities of the active support control using the third-order model of the synchronous machine and the traditional virtual synchronous generator control.Secondly,it analyzes the frequency modulation process of the power system on multiple time scales,including the inertial response stage,the primary frequency modulation process,the secondary frequency modulation process,and the rescheduling and allocation of power generation units.The flexibility index of battery energy storage station to participate in frequency regulation of power grid at multiple time scales is proposed,namely energy throughput capacity,climbing rate and rated power.Considering the extreme working conditions of battery energy storage station,define the adjustment coefficients of the energy storage power plants' charge state in different working intervals.To suppress the excessive deviation of the system steady-state frequency caused by the excessive release of rotor kinetic energy of the rotating unit.Setting the adjustment coefficients reasonably can control the depth of energy storage power station participating in the frequency control of the grid and create a productive frequency stable environment.Finally,the forward static frequency characteristics of battery energy storage station that meet the needs of the power grid are described,and the inertial response characteristics,primary frequency modulation characteristics,and secondary frequency modulation characteristics of energy storage power stations participating in power grid frequency regulation are analyzed.At the same time,the ratio of the frequency modulation output of the battery energy storage station to the frequency modulation output of the rotating unit is defined as the frequency modulation contribution factor,which is used to characterize the energy storage station assisting the traditional unit to participate in the primary frequency modulation of the power grid to reduce the steady-state frequency deviation.In the DigSILENT/PowerFactory simulation software,the two-end power supply system and the ring power supply system are built to verify the grid-connected stability of the battery storage station with active support and the effectiveness of participating frequency regulation.The simulation results show that this subject of far-reaching significance to the stability of large-scale battery energy storage station.