Rated DC Power Research Articles

Wired/Wireless Hybrid Charging System for Electrical Vehicles With Minimum Rated Power Requirement for DC Module

Due to various advantages, wireless charging as well as wired charging for electrical vehicles (EV) will co-exist for some time to come. A hybrid system that provides either wired or wireless charging mode is proposed in the paper. The hybrid system shares the workplaces and the power devices to save costs significantly. The cost of DC power module accounts for a large proportion of the total cost of the wired or wireless charging system and is directly related to its rated power. To reduce the rated power requirement of the DC module of the hybrid charging system, an optimized parameter design method regarding the coupling inductance of the wireless charging is presented for the hybrid system. Under the optimized coupling inductance, the minimum rated DC power requirement is achieved while meeting the battery charging profile of both the wired and wireless charging application. An EV hybrid charging system prototype is designed, built, and tested. Experiments showed that the proposed hybrid charging system has good adaptability for either charging method. Moreover, the proposed parameter design procedure can minimize the rated power requirement of the DC power module.

Test circuit for MMC‐based VSC valves in HVDC power station

A test circuit for modular multilevel converter (MMC)-based voltage-sourced converter valves in high-voltage direct current (HVDC) system is dealt with. The proposed scheme has an ability to provide a submodule current having DC component as well as AC component to represent real operating condition of HVDC transmission system. There is no need of extra power supply to provide the DC current component because the scheme has inherent circulating DC current between rectifier and inverter valves. Therefore, only one small power rated DC power supply is necessary. Experiments are carried out to show the validity of the proposed test circuit.

An integrated low-voltage rated HTS DC power system with multifunctions to suit smart grids

A low-voltage rated DC power transmission network integrated with superconducting cables (SCs) and superconducting magnetic energy storage (SMES) devices has been studied with analytic results presented. In addition to the properties of loss-less and high current transportation capacity, the effectively integrated system is formed with a self-acting fault current limitation feature of the SC and a buffering effect of the SMES to power fluctuations. The results obtained show that the integrated system can achieve high-quality power transmission under common power fluctuation conditions with an advanced self-protection feature under short circuit conditions, which is identified to suit especially the smart grid applications.

Probabilistic Models of Harmonic Currents Produced by Twelve-Pulse AC/DC Converters

The probabilistic approach is an efficient mean for harmonic prediction since it allows to take into account the randomly varying operating conditions of static converters. Although the six-pulse ac/dc converter has been the subject of probabilistic modeling, little consideration has been given to the 12-pulse ac/dc converter. In high-power applications, such as large rated dc power supplies and large rated dc and ac drives, 12-pulse ac/dc converters are usually preferred since they allow to reduce system disturbances due to harmonic currents. This paper presents an analysis of the random properties of harmonic currents produced by 12-pulse ac/dc converters that operate under random variations of their dc load and voltage unbalance. The probability density functions of the amplitudes and phase angles of the harmonic currents (of orders 12 k/spl plusmn/1 and 12 k-6/spl plusmn/1) are established and validated by results obtained from Monte Carlo simulations.