Research On Mechanism And Method Of Energy Storage System To Improve Power System Inertia Damping Characteristics

In recent years,with the increasing penetration rate of new energy,the installed proportion of conventional Rotational Synchronous Generator(RSG)has been declining.As a result,the rotary reserve capacity and inertia of the grid are relatively reduced.On the other hand,the existing inverter control technology must rely on the phase-locked loop algorithm.In the unbalanced grid environment,the phase-locked loop not only has a long response time,but also weakens the stability of the weak grid system.Therefore,scholars have proposed the use of Energy Storage Systems(ESS)to enhance the frequency stability of the grid,to equivalently improve the inertia level and damping capacity of the power system.Static Synchronous Generator(SSG)model introduces the inertia,damping and synchronization characteristics that are easy to understand in power system analysis into the dynamic characteristics analysis and stability law of ESS.In this paper,the physical mechanism of the improved droop control strategy in terms of simulated inertia,damping and synchronization characteristics is analyzed using the SSG model and the DC voltage time scale concept.At the same time,the ability and law of ESS simulated inertia/damping characteristics of classical droop control and improved droop control are compared in detail.In this paper,through the stability of the DC-side capacitor voltage of the energy storage system,the influencing factors and physical mechanisms of the stability of the ESS power angle are revealed.In this paper,the electrical torque method and multi-time scale dynamic characteristics are used to analyze the physical mechanism of the ESS to achieve the stability of the auxiliary grid when the power oscillation occurs in the grid under the two classic control strategies(The stability of the grid-connected inverter).At the same time,the mechanism of the influence of different control strategies on the inertia level,synchronization capability and damping effect of the grid is explained.In order to give full play to the stabilizing effect of ESS,this paper analyzes the key factors affecting the control performance and the law of action: structural parameters,control parameters and steady-state operating points.In this paper,the order component of ESS is extracted under the unbalanced voltage environment,and a fast detection method for the voltage sequence component of the three-phase power grid is proposed.The method first obtains the order component of the unbalanced voltage by using the virtual orthogonal signal construction method,the single-phase phaselocked operation,and the symmetrical component method.This method only needs the grid voltage and its virtual quadrature signal,and can directly calculate the time domain expression of the three-phase unbalanced voltage sequence component.When the grid frequency fluctuates within the limits allowed by the national standard,the method can quickly obtain the order component of the unbalanced grid voltage without updating the grid frequency in real time,and the calculation accuracy can meet the engineering requirements.The conclusions of this paper are helpful to understand the physical mechanism of ESS,and help to design effective ESS control strategies and analyze the dynamic characteristics of ESS.At the same time,this paper can assist to improve the inertia effect,damping level and synchronization capability of the power system,and enhance the stable operation capability of the ESS.