Fang Zheng Peng

Bio: Fang Zheng Peng is an academic researcher from Florida State University. The author has contributed to research in topics: Inverter & Z-source inverter. The author has an hindex of 87, co-authored 380 publications receiving 43073 citations. Previous affiliations of Fang Zheng Peng include Oak Ridge National Laboratory & Nagaoka University of Technology.

Speed-Sensorless Control of Induction Motors for Electric Vehicles

Abstract: An electric bus system has been operating in the downtown area of Chattanooga, Tennessee for more than four years. The buses use traditional hard-switched IGBT inverters driving special induction motors with a speed sensor (tachometer) and two embedded fluxsensing windings to provide rotor speed and flux information to the motor controller for implementation of high performance field oriented control (vector control). The induction motor is oil-cooled and equipped with an internal planar gear reduction. The current system has experienced failures in both speed sensors and flux sensors because they are unreliable, susceptible to EMI and must operate in a hostile environment created by oil leaks. A speedand flux-sensorless induction motor drive system with a new 100 kW soft-switching inverter has been implemented to replace the existing system. The new soft-switching inverter is able to provide 300 A (rms) and 230 V (rms) continuous power to the motor with no voltage surges and reduced dv/dt (<300V/us) at switching. The new inverter also draws ripple-less DC current from the battery. As a result, the new inverter is friendly to the motor and battery. Extended lifetime is expected for both the motor and battery. The new inverter with the speedand flux-sensorless control has been road-tested and has achieved satisfactory performance. The project was supported under the Department of Energy (DOE) funding and local industry partnership. INTRODUCTION

Three-Phase DC Capacitor-Less Solid-State Variable Capacitor

Abstract: Grid-connected full bridge inverters typically have a bulky electrolytic dc capacitor to absorb the unbalanced power from the ac side. The electrolytic capacitors are vulnerable and normally have shorter lifetime than other components in the converter. In most full-bridge inverter applications, the dc voltage is required to be relatively constant. However, in reactive power compensation applications, such as solid-state variable capacitor (SSVC), the constant dc-bus voltage is unnecessary since the dc bus is floating. This paper proposes a three-phase dc capacitor-less SSVC, which removes the electrolytic dc capacitor from the circuit by releasing the constraints on dc bus voltage fluctuation. The dc voltage is supported by ac side voltage directly. The remaining dc capacitance has a value of only 3% compared to that of the conventional three-phase SSVC. The proposed three-phase dc capacitor-less SSVC is validated by simulation.

Analysis of Line Rush Current in Short Commutation for SHAPF

Abstract: The current-source nonlinear load is normally composed of the thyristor or diode rectifier, but the process of the short commutation will cause the line rush current for the SHAPF. In order to solve this problem, a rush current inductor and rectifier, and a series-in SHAPF are proposed to suppress the line rush current in the paper. The simulation and experiment results verify their validity.

Bidirectional Universal Converter Transformer Design for Electric Vehicle Onboard Charging

Abstract: This paper highlights the design aspects of the universal converter transformer as part of an effort done to use the universal converter for onboard charging applications for electric vehicles. Today's requirements of onboard charging ask for bidirectional follow capabilities and an ability to interface with various power grid types (single-phase, three-phase three- wires, and three-phase four-wire, etc.). Such requirements increase the difficulty of designing the transformer due to the high input to output voltage gain range of the DC-DC converter. The universal converter uses a dual active bridge that maintains consistent performance across all the operating regions. This paper provides the necessary steps of building the transformer and shows the experimental results to assess the proposed design method.

A carrier magnitude varying modulation for distributed static series compensator to achieve a maximum reactive power generating capability

Abstract: Conventional single-phase H-bridge applications have second-order harmonic ripple power on the dc bus. However, in applications like a voltage source inverter (VSI) module of a Distributed Static Series Compensator (DSSC), a larger dc bus voltage fluctuation is acceptable since the dc bus connects to no load. This paper releases the constraints on dc bus voltage ripples so that the dc-bus capacitor can be fully utilized. Based on this idea, a carrier magnitude varying modulation is proposed, in which the VSI can generate ten times the reactive power of a conventional SPWM based VSI. The system reactive power generating capability is assessed to compare with the conventional SPWM based VSI and the constant duty cycle control based VSI. A PI controller is applied to the system to regulate the ac current. The analysis and design are validated by simulation and experiments.

Multilevel inverters: a survey of topologies, controls, and applications

Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

Abstract: The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

Multilevel converters-a new breed of power converters

Abstract: Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of DC capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate DC sources. The operating principle, features, constraints, and potential applications of these converters are discussed.

An innovative modular multilevel converter topology suitable for a wide power range

Abstract: This paper presents a new multilevel converter topology suitable for very high voltage applications, especially network interties in power generation and transmission. The fundamental concept and the applied control scheme is introduced. Simulation results of a 36 MW-network intertie illustrate the efficient operating characteristics. A suitable structure of the converter-control is proposed.