Zhang Buhan

Optimal capacity of flow battery and economic dispatch used in peak load shifting

With the rapid development of social economic and the growing power demand, it brings the phenomenon that the capacity of power network is expanding gradually and the load feature has changed very much. The peak-valley difference is becoming larger and larger with an annual increasing trend and the problem of peak load shifting has been increasingly apparent. It can solve the problem by charging during valley period and discharging during peak period using of the storage technology of flow battery (FB). It helps to make the peak load shift to the valley, so that it can improve the load feature. Based the application of peak load shifting, this paper presents a methodology to optimal the capacity of flow battery, it builds the optimization model to determine the sizing capacity of flow battery while the objective function of this model is to maximize the benefits the power system. Its based on the example networks load feature and the security of the system network and charge-discharge characteristics of flow battery as its constraints. While the capacity of flow battery has been determined, an operating strategy of flow battery to dispatch power has been presented. The result is significant to demonstrate that the application of FB to implement the peak load shifting has great advantages.

A real-time dynamic equivalent solution for large interconnected power systems

Dynamic equivalent has been a basic approach for analysis and computation of large scale-increasing interconnected power systems in China. Security defense of power systems and real-time monitoring of system states require more rapid and effective computation of large power grids. This paper introduces a solution for real-time dynamic equivalent of large multi-area power systems. It is based on real-time measurement data from Wide Area Measurement System and parameter identification. A parallel dynamic equivalent model composed of an equivalent generator and an equivalent synthesis load was put forward, in which the equivalent generator uses a 3rd order electromechanical transient model with damping while the equivalent synthesis load uses a static characteristic model considering both voltage and frequency. Identifiability analysis was carried out for this nonlinear dynamic equivalent model. In order to apply Laplace transformation-transfer function method, the model was firstly linearized. Particle Swarm Optimization algorithm was utilized for parameter identification of the dynamic equivalent model. For AC power systems, this model is verified on CEPRI 8-machine 36-bus example system. Load model and the style of disturbance are two remarkable factors that relate to the stability of the whole power system, which are fully considered in this paper. The simulation results show that the dynamic equivalent model can reflect the dynamic responses and the transient stability of the original system, no matter which is transient stable or unstable, angle unstable or voltage stable. When we change the load model in the original system, the static characteristic model with both voltage and frequency factors can throughout represents the dynamic behavior of the original system, which confirms its robustness of this dynamic equivalent model. All the simulation work was performed on PSASP.

Studies on security capacity of wind farms containing VRB energy storage system

This paper proposes into determining the security capacity of wind farms containing VRB energy storage system. To achieve these we firstly build the model of the doubly fed induction generator and VRB model. After studying their characteristic, a study case of local grid integrated with a wind farm is simulated in Matlab/PSAT. Finally security capacity of the wind farm under several situations is studied. It concluded that the energy storage devices have significant influence on the security capacity of the wind farm.