Jian Chen

Bio: Jian Chen is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topics: Voltage source & AC power. The author has an hindex of 14, co-authored 68 publications receiving 1043 citations.

Direct repetitive control of SPWM inverter for UPS purpose

Abstract: A novel repetitive controller directly combined with an open loop SPWM inverter is presented in this paper. To cope with the high-resonant peak of the open loop inverter that may cause instability, a zero-phase-shift notch filter other than the inverse transfer function of the inverter or a conventional second-order filter is incorporated in the controller. The proposed method has good harmonic rejection and large tolerance to parameter variations. To further reduce the steady-state error, a low-pass-filter Q(z) algorithm is applied. The DC bias problem is also taken into consideration and solved with the repetitive controller itself. The method is implemented with a digital signal processor and achieves low THD% (1.4%-1.7%) with nonlinear loads and fast error convergence (3-5 fundamental periods). It proves to be a cost-effective solution for common UPS products where high-quality output voltage is more stressed than fast dynamic response.

Power-Flow Control Performance Analysis of a Unified Power-Flow Controller in a Novel Control Scheme

Abstract: In this paper, real, reactive power, and voltage balance of the unified power-flow control (UPFC) system is analyzed. Two important results related to UPFC control are shown in this paper. First, the shunt converter provides all of the required reactive power during the power-flow changes if the UPFC bus voltage is constant. Second, the UPFC bus voltage can be controlled both from the sending side and from the receiving side. Based on the analysis, a novel coordination controller is proposed for the UPFC. The basic control strategy is such that the shunt converter controls the transmission-line reactive power flow and the dc-link voltage. The series converter controls the transmission-line real power flow and the UPFC bus voltage. The real/reactive power coordination controllers in the UPFC control system can obtain good performance both during transient and stable conditions. Experimental works have been conducted to verify the effectiveness of the proposed control strategy.

A Novel PWM Technique in Digital Control

Abstract: One problem with microprocessor-based high-frequency pulsewidth-modulation (PWM) converters is the modulating resolution limitation caused by limited-time resolution of hardware timers. In this paper, a novel PWM technique, the double PWM (DPWM), is proposed. DPWM combines the advantages of low-frequency modulation and high-frequency switching in power conversion and resolves the contradiction between high frequency and accuracy in a digital control scheme. DPWM effectively increases the resolution in digital control, while the harmonics introduced by this method is found to be negligible. Theoretical analysis, characteristics, and design considerations are given, and they are verified by experiments on a 5.5-kW 20-kHz insulated-gate-bipolar-transistor boost-buck converter

A novel solid state fault current limiter for DC power distribution network

Abstract: DC power distribution network is specifically used in industrial manufactures and aircraft/ship power distribution since it can provide flexible interface to various power converters with high efficiency and less conversion stage. The protection for DC power distribution system is more difficult compared with those AC systems since there's no natural zero crossing point for the current. Low shortcut impedance will cause high current rising rate, which can bring heat, arc and electrical force damage to the DC power distribution grid in a quite short time that the DC breakers hardly act. This paper proposed a solid state fault current limiter (FCL) using a combined power switch. Solid state FCL can achieve fast response to the fault current in the DC power grid, without special requirement of the cooling system. Using a combined power switch instead of single fully controlled power electronics component can reduce the steady power loss while normal working states. When fault states occurs, the power electronics control technique can strictly limits the fault current beneath a certain desired range. In that way, the fault damage can be limited. Experiment results are taken to prove this design.

Analytical estimation of common mode conducted EMI in PWM inverter

Abstract: In PWM inverter system, the high dv/dt and di/dt due to the fast switching of IGBT could bring serious EMI issues. How conducted emission measurement should be made are specified. Based on the study of mechanisms on common mode conducted electromagnetic interference (CM EMI) associated with a single phase PWM inverter, the origin and propagation path of CM EMI noise are highlighted. Compared with buck converter, a simple equivalent circuit is proposed to study the CM EMI. Time and frequency domain analysis is conducted to obtain CM current waveforms and noise spectra in 10 KHz-30 MHz frequencies. The simulated CM EMI waveforms are compared with the actual experiments to verify the validity of the proposed model. The modeling method described can be readily extended to a three-phase PWM inverter.

DC Microgrids—Part II: A Review of Power Architectures, Applications, and Standardization Issues

Abstract: DC microgrids (MGs) have been gaining a continually increasing interest over the past couple of years both in academia and industry. The advantages of dc distribution when compared to its ac counterpart are well known. The most important ones include higher reliability and efficiency, simpler control and natural interface with renewable energy sources, and electronic loads and energy storage systems. With rapid emergence of these components in modern power systems, the importance of dc in today's society is gradually being brought to a whole new level. A broad class of traditional dc distribution applications, such as traction, telecom, vehicular, and distributed power systems can be classified under dc MG framework and ongoing development, and expansion of the field is largely influenced by concepts used over there. This paper aims first to shed light on the practical design aspects of dc MG technology concerning typical power hardware topologies and their suitability for different emerging smart grid applications. Then, an overview of the state of the art in dc MG protection and grounding is provided. Owing to the fact that there is no zero-current crossing, an arc that appears upon breaking dc current cannot be extinguished naturally, making the protection of dc MGs a challenging problem. In relation with this, a comprehensive overview of protection schemes, which discusses both design of practical protective devices and their integration into overall protection systems, is provided. Closely coupled with protection, conflicting grounding objectives, e.g., minimization of stray current and common-mode voltage, are explained and several practical solutions are presented. Also, standardization efforts for dc systems are addressed. Finally, concluding remarks and important future research directions are pointed out.

Quantization resolution and limit cycling in digitally controlled PWM converters

Abstract: This paper discusses the presence of steady-state limit cycles in digitally controlled pulse-width modulation (PWM) converters, and suggests conditions on the control law and the quantization resolution for their elimination. It then introduces single-phase and multi-phase controlled digital dither as a means of increasing the effective resolution of digital PWM (DPWM) modules, allowing for the use of low resolution DPWM units in high regulation accuracy applications. Bounds on the number of bits of dither that can be used in a particular converter are derived. Finally, experimental results confirming the theoretical analysis are presented.

High-frequency digital PWM controller IC for DC-DC converters

Abstract: This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm/sup 2/ of silicon area in a standard 0.5 /spl mu/ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.

Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview

Abstract: This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA. More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.

Digital control in power electronics

Abstract: This book presents the reader, whether an electrical engineering student in power electronics or a design engineer, a selection of power converter control problems and their basic digital solutions, based on the most widespread digital control techniques. The presentation is primarily focused on different applications of the same power converter topology, the half-bridge voltage source inverter, considered both in its single- and three-phase implementation. This is chosen as the test case because, besides being simple and well known, it allows the discussion of a significant spectrum of the most frequently encountered digital control applications in power electronics, from digital pulse width modulation (DPWM) and space vector modulation (SVM), to inverter output current and voltage control, ending with the relatively more complex VSI applications related to the so called smart-grid scenario. This book aims to serve two purposes: (1) to give a basic, introductory knowledge of the digital control techniques applied to power converters; and (2) to raise the interest for discrete time control theory, stimulating new developments in its application to switching power converters.