Zhiyu Xu

Controllability of nonisolated DC-DC converters with constant-power-load

This paper addresses the controllability of six types of nonisolated DC-DC converters (i.e. Buck, Boost, Buck-Boost, SEPIC, Cuk and Zeta) feeding the constant power load (CPL). The operation principle of SEPIC is presented so that the drift vectors and control functions are derived, which demonstrate that each switching mode is an affine nonlinear subsystem. Employing the recent findings on the controllability of switched nonlinear systems, we prove that every state on the maximal integral manifold is an interior of the convex cone generated by (G-shifted) drift vectors and control functions, thus the nonisolated DC-DC converters with CPLs are controllable. This technique could be applied to analyze other isolated converters.

Study on charging strategy of electric vehicle parking lot based on improved PSO

Electric vehicle parking lot is a kind of profit service facilities nearby commercial office buildings for electric vehicles to park and charge. A V2P model is built to describe electric vehicles charging in the parking lot based on V2G (vehicle to grid) technology. Under the conditions of real-time pricing, improved particle swarm optimization (PSO) algorithm is applied to study on charging strategies of electric vehicles. Real-time electrovalency data of PJM and the parameters of mainstream electric vehicles are used in simulation. Results of the simulations show that the proposed model is reasonable and the improved PSO algorithm is both efficient and effective.

Switched linear system model and simulation analysis of the electronic ballast

This paper casts systematic insight into the electronic ballasts which are functionally made-up by three cascade stages, i.e., input, PFC and output. Simulation results utilizing the semi-theoretical model indicate that the fluorescent lamp operating at high frequencies is approximately a voltage dependent resistor. Further numeric analysis simplifies the lamp load network as a resistor-inductor series branch. The electrical characteristics of the output stage are revealed and described by a switched RL load. Employing the system equivalent circuit, we derive the model of the electronic ballast. And the state-space descriptions (line current, capacitor voltage, and load current are states variables) illustrate that the electronic ballast driving the fluorescent lamp is a switched linear system of third-order and four-mode.

A dynamic small-signal model of the constant-frequency pulse width modulator of switching converters

This paper proposes a dynamic small signal model of the constant-frequency pulse width modulator of switching converters. The existing model is represented as a simple gain block Fm, which is relatively short in both accuracy and physical meanings. Employing the methods of probability, this dynamic model provides a more accurate prediction of the system behavior in the sense of statistics, compared to its previous counterpart

Mechanism Design of Virtual Power Plant for the Future Smart Grid

Virtual power plant (VPP) can respond to the real-time electricity price and implement management of controllable power plants and the distributed energy resource (DER) coordinately in future Smart Grid. Thus the mechanism of virtual power plant in future Smart Grid is designed in this paper. The model formulations are presented and the MS-VND algorithm is used to optimize the objects of both commercial VPP (CVPP) and technical VPP (TVPP). Simulations are conducted on IEEE-30 standard test system and the performance of the solutions is computationally compared and analyzed.

Demand-side response of smart clients under real-time pricing

Electric power market will transform to the free market based on real-time pricing and the traditional clients will change to smart clients with the development of Smart Grid. A smart client model which includes general loads, energy storage devices, electric vehicles and distributed generations is developed in this paper to study the demand-side response under real-time pricing. MS_VND algorithm is used to search the optimal strategies. Computational tests on the real data show that the proposed model is reasonable and MS_VND algorithm is both efficient and effective.