Research On Energy Storage Under Emergency Control To Improve The Transient Stability Of Power Systems

With the surge in primary energy consumption,the world is facing a shortage of fossil energy,environmental degradation and other challenges.Load demand is increasing,more and more electronic equipment and complex power system structure will bring a hidden danger to the grid’s transient stability.In this severe development context,low-carbon sustainable development has become the programmatic guideline for the development of China’s power grid.A large amount of installed capacity of new energy generation connected to the grid brings more challenges to the safety of the grid,and in order to reduce the economic losses caused by transient instability to the grid,how to reasonably carry out emergency braking becomes the key to solving the problem.Firstly,it is proposed to calculate the transient power angle and voltage stability based on the rotor motion and dynamic load of the generator,and to collect in real-time the busbar voltage at each node of the system,the voltage and busbar slip at the end of the induction motor,the basic parameters of the generator: such as power angle,angular velocity,mechanical power,and electromagnetic power,and to calculate the transient potential energy,and to construct a database of transient power angle and voltage stability criteria.The stability criterion of the phase plane trajectory of the single-machine infinity system is proposed,and the destabilization criterion of the multi-machine system is extended to identify the destabilization trend of the motion trajectory;the influence of the dynamic load on the transient stability of the system is considered on the basis of the work angle stability.Considering that the energy storage system can alleviate the peak-to-valley difference of the grid,improve the power quality of the grid,and smooth out the randomness and volatility of renewable energy,this paper makes full use of the ontology and converter resources of the energy storage system to build an energy storage system model that can reflect the charging and discharging rates and storage capacity limits of different energy storage systems under the PSASP UD mode and conducts simulations to verify the accuracy of the model for the change of load and power SOC and energy storage output capacity.Energy storage power supply can be used as an important link in transient emergency control.In order to reduce the amount of emergency control,improve the system frequency and voltage after cutting the machine,and smooth out the generator power angle swing curve,this paper proposes an emergency control strategy with cutting the machine and cutting the load as the main components and energy storage device as a supplement.According to the equation of motion of the generator rotor,the system destabilization is carried out on the power multi-machine system with energy storage power participating in the regulation of double machine equivalence,accounting for the amount of control required to restore stability of the system with energy storage power participating in the single machine system.Separate capacity quantification of energy storage involved in transient voltage safety emergency load cutting control strategy,energy storage involved in transient power angle stability emergency cut machine control strategy,the introduction of energy storage power output and cut machine volume between and energy storage involved in regulating the system cut load control of energy storage output volume,cut machine control volume,cut load control volume.Simulation experiments are carried out in the EPRI-7 system and EPRI-36 system.Through the comparison of different emergency control schemes,the simulation results show that the emergency control strategy of transient stability with the participation of energy storage power supply in regulation can effectively improve transient stability,reduce the amount of emergency control cut,and suppress frequency and voltage reduction;the emergency control measures with the participation of energy storage in load shedding effectively reduce the amount of load shedding,the voltage recovery degree is optimal,and the voltage amplitude and frequency are quickly restored to the initial state,relieving the pressure on the grid.