Xiao Liye

Investigation on the spatiotemporal complementarity of wind energy resources in China

Wind power resources are abundant in China, especially in northern China and eastern coastal areas of China. Nevertheless, wind energy has intermittent and unstable characteristics, which leads to random power output and limits the large-scale utilization of wind energy resources. It has been shown that geographically dispersed wind plants have obvious spatiotemporal offsetting effect. Power output from each individual site exhibits the power ups and downs. However, when we simulate power lines connecting sites over a certain region, the output from them changes slowly and rarely reaches either very low or full power. Hence using the spatiotemporal complementarity of wind resources effectively is highly beneficial to the smoothing of power supply. This paper investigates the spatiotemporal complementarity of wind resources in China based on the relevant data of wind energy resources, which are offered by China Meteorological Administration (CMA).

The frequency dependence of AC transport losses in stacked Bi-2223/Ag superconducting tapes

AC transport losses in a single superconducting tape, double- and triple-stacked Bi-2223/Ag superconducting tapes were measured by use of electrical method. The measurements were carried out at 77K with the frequency of AC transport currents ranging from 50 to 1000Hz. The dependence of AC losses on frequency and the number of tapes in the stack were presented and analysed.

Numerical Simulation of Flow and Heat Transfer Process of Solid Media Thermal Energy Storage Unit

A sensible heat storage unit with a hollow cylinder of solid media was studied semi-analytically. The heat transfer process in the heat storage medium was solved by using an integral approximate method. The forced convective heat transfer inside the tube was coupled with the heat conduction in the heat storage media. This method enables evaluation of the performance of the storage device in transient conditions. For the operation considerations, only fully developed turbulent flow is calculated. Different heat transfer fluids such as water and air with variable thermal properties dependent of temperature are used in calculations. Concrete and cast iron are selected as heat storage materials. From the simulation results presented in this paper, the thermal conductivity, the distance between the tubes, heat transfer fluid, tube size and flow velocity are the key parameters for such heat storage unit design.

Simulation Research of Smes With Fuzzy Logic Controller for Improving the Transient Stability in Wind Farm

The mathematic models for wind power generator and superconducting magnetic energy storage (SMES) are introduced, and the function of SMES in improving the operation performance of wind farms is studied. The simulation results show that the proposed fuzzy logic-controlled SMES is a very effective device for improving the transient stability of wind power system after short circuit of the grid.

Research of fuzzy logic-controlled smes for power system transient voltage stability

Superconducting Magnetic Energy Storage (SMES) is a power electronic based device with a superconducting coil that has the potential to bring essential functional characteristics to the utility transmission and distribution systems. This paper presents a new approach and corresponding experiments for fuzzy logic-controlled SMES to improve the transient voltage stability of electric power system. The SMES coil built for power utility applications has the following unique design characteristics: 0.2 H, 20 kW/100 kJ, 1 kA dc current. Based on the result of SMES prototype experience, a mathematic model of power system and SMES are adopted. A fuzzy controller is assigned. Bus voltage is taken as the input signal to fuzzy controller. The fuzzy rule-bases are designed and explained. The validity of the suggested control strategies are confirmed by simulation and experimental tests. From the results they are demonstrated that transient voltage stabilizing effect by mean of SMES was very significant.

Improving performance of superconducting fault current limiter with mutual-inductor

The novel method to improve the limiting capability of DC reactor type superconducting fault current limiter (SFCL) by using mutual inductor is presented in this paper. The configurations of the SFCL are described in detail, in which both a superconducting and a mutual inductor play roles of the limiting elements. The working principle of the SFCL is analyzed theoretically and the mathematical model of the SFCL is built. Simulation has been carried out by using EMTDC in a 10 kV/1 kA three-phase power system. The simulation show good results. The performance of the SFCL with mutual inductor is validated, and the feasibility of the SFCL with mutual inductor is also demonstrated

Design and primary experiment for a single phase 220V/100A/6kW bridge Fault Current Limiter-SMES

Publisher Summary This chapter explores a single phase 220V/100A/6kW bridge fault current limiter-SMES (FCL-SMES) demonstrator. The system consists of a series linking transformer, a 6 kW IGBT voltage converter with 20 kHz PWM control method, a 6 kW IGBT current regulator with 20 kHz phase-shifted control method, a 26 mH/25A Bi-2223 coil, a rectifying diode bridge, and a DSP-based controller. A brief description of its various subsystems, including the converter, current regulator, Bi-2223 coil, rectifying diode bridge and the DSPs-controller, is given. Its principle of the function to limit the current is verified. The components of FCL-SMES, such as converter, current regulator, and the HTS coil are preliminarily tested. The further experiment is underway and the stage phase II will proceed with the construction and test of a three phase prototype. The current regulator can not only charge the HTS coil, but also absorb the energy from the system and the coil to compensate the voltage sags through the converter. In the controller of the system two very fast DSPs are used to implement the control algorithms for FCL-SMES.

Evaluation on power system transient stability with resistor type SFCL and parameter design

Publisher Summary In this chapter a theoretical analysis of power system transient stability with resistor type superconducting fault current limiter (SFCL) using Lyapnov energy function is presented. SFCLs as the devices for limiting fault currents have been progressing thanks to the development of superconducting technology. Power system transient stability with resistor type SFCL is already studied, but it still needs deep investigation. This chapter proposes a simple single-machine infinite-bus power system with SFCL, a generator, and transformers being mathematically modeled, to investigate the effects of SFCLs on the power system. Through theoretical analysis and digital simulation, it is found that the resistor type superconducting fault current limiters not only limit fault current but also protect synchronization of generators. The SFCL can decrease the initial transient energy Vc injected into the power system and increase the critical transient energy Vcr, which enhances the transient stability. Both theoretical analysis and simulation results demonstrate that resistor type SFCL could improve the transient stability of power system.