C. D. Xu

A Novel Detection Method for Voltage Sags

Determining the start and end of the voltage sag event is very important for sag analysis and mitigation. There are several detection methods for voltage sags in which sag voltages are usually expressed in the terms of RMS. The RMS method represents one cycle historical average value, not instantaneous value which may lead to long detection time when voltage sag has occurred. This paper will proposed a novel voltage sag detection method based on miss voltage technique. Proper dead-band and hysteresis are used in the method. The actual instantaneous voltage is compared with certain percentage of desired grid voltage and certain percentage of the amplitude of the grid voltage. Through instantaneous value comparison, low instantaneous value of the grid is shielded which overcome the mishandling turnover of voltage sags. The approach is fully described, and the results are compared with other methods for marking the beginning and end of sag, such as RMS value evaluation method and Peak-value method and simulation result provides that the method is efficient and fast and can be used to determine the initiation and recovery of voltage sags accompanied by missing voltage technique.

A survey of distributed power system — AC versus DC distributed power system

The history of the centralized and distributed power system is introduced far away from the power system being first built by Edison, which started the first confrontation between ac and dc power system. Although ac power system has dominated for a long century because of easy transmission and some other benefits, dc power system has still gave some good performances and attracted more attention during the past three decades. This paper will discuss the current developing stage of dc distributed power system by the following contents: the basic structure and characteristics; the benefits of the dc distribution system; the development of current techniques adopted in DPS and its analysis of protection and system interaction. In additional, the comparisons between dc and ac distributed power system are presented in detail, and finally, the challenge in future is also summarized.

A Family of Dual-Phase-Combined Zero-Current Switching Switched-Capacitor Converters

A family of dual-phase-combined resonant switched-capacitor (SC) converters with a similar structure is presented in this paper. Comparing with their conventional single-phase version, each of the proposed dual-phase converters is more than just a switched capacitor but also provides the service of two phases operated in the fully complementary manner. This design provides a more stable output voltage with low ripple and significantly reduces the quantity of switches. These converters therefore have the common features of smaller size, lower cost, and higher power density than the conventional multiphase SC converters. With the zero-current switching technique, the proposed converters also possess high-power conversion efficiency. The detailed analysis of the circuit operation and voltage ripples is presented. Experimental results are also provided to confirm the performance of the new family of converters.

Study of Intermittent Bifurcations and Chaos in Buck-Boost Converters with Input regulators

This paper presents two series of models in the buck-boost converters with input regulators under peak current mode control. Stroboscopic maps are derived to describe the dynamical behaviors of buck-boost converters with input filter capacitor. In terms of the developed discrete maps, fast scale instabilities in buck-boost converters are studied. Numerical results reveal the circuit system exhibits distinguishing nonlinear phenomena, i.e., intermittent bifurcations and chaos. In addition, the periodicity of the intermittent behaviors is also analyzed in detail.

Characterization and modeling of copper foil conductor for high frequency power distribution

This paper investigates characteristics of copper foil conductor for 50 kHz high frequency AC power distribution. Characterization includes parameter estimation, power loss analysis and electro-magnetic field simulation using FEM software. Experiments have been conducted to obtain parameters for the double layer copper foil transmission line. Further, a model for the high frequency AC transmission line is proposed based on the obtained experimental results.

Bidirectional tapped-inductor-based buck-boost convertor and its circuit application

A novel Buck-Boost convertor based on tapped-inductor is presented in this paper. It can be provide wider voltage conversion ratio than conventional Buck-Boost convertor. When it running as boost-mode, recommended winding ratio setting (KD=1, KT<;1) helps to achieve larger conversion ratio; when it running as buck-mode, the smaller voltage conversion ratio can be realized by opposed winding ratio setting (KT=1, KD<;1). The detail analysis of this convertor is included in the paper. To meet the requirement of energy transfer bi-directionally in some special occasions, a bi-directional double-tapped inductor Buck-Boost conversion circuit based on former convertor is discussed in this paper. Running in alternating between motoring and regenerative braking manner is analyzed in detail. Finally, experimental results verify the correctness of theoretical analysis and the proposed convertor can provide wider conversion ratio with high efficiency.

Electromagnetic scattering of high power traction transformer in high speed railway based on FEM

The paper presents the investigation of the electromagnetic interference for the traction system in a high speed railway (HSR). Tt is important to study the characteristic of the transformer, converter and power cable for HSR. Traction transformer as the one of the first equipment on board traction system for connection to pantograph, and plays a key role in the electromagnetic investigation. In this paper, the characteristic of the transformer is studied to further provide information for investigation of electromagnetic interference.

Some considerations of arc protection and breaker design for high frequency AC power distribution systems

High frequency power distribution already has a numerous applications in electric vehicle, renewable energy microgird, and telecommunication system. In order to propel high frequency power distribution into larger power grade, an effective ac arc protection scheme is significant for safety and reliability. However, almost all of the studies of arc fault are focused on dc or low frequency ac (LFAC). This paper presents protection scheme and examines electrical characteristics for high frequency arc fault. Meanwhile, high frequency breaker is examined with ZCS feature, and residual current devices (RCD) design is explored for high frequency power distribution as well. First, the location of arc fault detector (AFD) and interrupting devices (ID) is studied from system level; and the single phase arc grounding fault is analyzed for high frequency sinusoidal waveforms. Second, zero-current-switching (ZCS) feature of high frequency breaker is discussed from monitor circuit and breaker circuit. Third, trigger deficiency of high frequency RCD is demonstrated and corresponding solution is examined. Lastly, the simulation results further testify the effectiveness of theoretical analysis.

A Topology of Step-Down Resonant Switched-Capacitor-Based AC–DC Converter for High-Frequency AC Distribution

This paper proposes a switched-capacitor (SC)-based step-down AC–DC power converter with high-frequency feed without rectifier or transformer. The operational principle of the circuits and the design considerations are described. The main advantage of the circuit is that step-down voltage can be achieved in the circuit by simply configuring with cascaded stages, which will be much more convenient to be modular development and easy for replacement and maintenance; the voltage and current stresses of most components are smaller than the conventional converter. Using buffer capacitor to reserve energy, there are no magnetic energy storage elements in the circuits. Weight and size can be further reduced due to high-frequency-power line operation. Zero current switching (ZCS) is achieved by introducing small resonant inductors. Therefore, higher efficiency and power density can be achieved. The performance of the converter has been demonstrated by an experiment with 50 kHz 50 V power feed which is emulated by a signal generator and high-frequency amplifier to prove the concept.

Development of an Automotive HID Electronic Ballast Based Microprocessor

An automotive high intensity discharge (HID) electronic ballast based microprocessor is presented along with hardware design, software design and experimental results. The paper discusses some of the vital practical issues on hardware circuit design. According to the start-up characteristics of HID lamp, a timing control is presented. A new control method is proposed on the power mode control by controlling HID lamp current. Experimental results demonstrate the design of hardware and software is successful.