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Methods for detecting island in an electric power system are classified as active, passive or hybrid. For certain applications, passive methods are sometimes favored over other detection methods because they are cheap, simple and do not affect the power quality of the electric power system. This paper introduces an islanding detection approach based on wavelet packet transform using only local measurements...
A grid-connected power converter for a distributed power generation system is proposed in this paper. The functions of islanding detection and active power filter are incorporated into the control of the grid-connected power converter. The operation theory of the proposed islanding detection method is that a small perturbation is added into the amplitude of utility current only when the amplitude...
A united system of thyristor switched capacitor (TSC) and static var generator (SVG) was proposed to improve voltage regulation, stability, and power factor in ac transmission and distribution systems. The TSC is consisted of multi-groups binary-coded capacitors, which is mainly used for large capacity var compensation step by step. SVG compensates small capacity reactive power continuously, and filters...
Microgrid is an effective way to integrate the distributed energy resources into the utility networks. Conventionally, the voltage-source inverters in microgrid with sinusoidal current regulation are used in grid-connected mode. In this paper, a two-degree-of-freedom nonsinusoidal current regulation (NCR) is proposed for both the distributed power generation and power quality enhancement. The equivalent...
DC voltage control is critical for grid-connected inverters, as it contributes to reduce the DC capacitance and improve system reliability as well as MPPT performance. A predictive control scheme of DC voltage for single-stage three-phase grid-connected PV inverters is proposed based on the analysis of the energy balance relationship in one control period, while AC current is also regulated by predictive...
Stability issue of DC bus in power system with multi-sources such as renewable and distributed energy sources is investigated. A simple design with cascade control for individual Buck converter, Boost converter and ICFFB converter to operate stably under constant power load is presented. Integration of these converters into the DC power system and solution for subsystem dynamic interactions are analyzed...
A high voltage power vertical double-diffused MOSFET with reduced JFET area by using an overall implantation was discussed. The reduced JFET area realizes a low gate charge and a high switching speed, due to the reduction of the gate-drain overlapped area. The measured gate-drain charge and gate charge can be improved by 61.1% and 71.8 %, respectively. The F.O.M of the proposed device and the conventional...
Termination region plays an important role in high voltage power VDMOSFETs. Termination structure such as floating-field-limiting-rings and field plates are the common structures used in a termination region because they can be fabricated without additional masks. However, sometimes we use both of them, sometimes only the floating-field-limiting-ring. The difference between these structures must be...
A new kind of UPS converter applied with one set of batteries is proposed. The converter has two operation modes: Buck operation mode and Buck-Boost operation mode, and these two modes run individually and have no common current path. This eliminates circulation current between different UPS as they are running with one common set of batteries in battery mode. In addition, two control methods are...
In this paper, a high efficiency LLC resonant converter is presented. The burst mode control method is applied to reduce the losses and thus the efficiency of light load condition is improved. Especially, the effectiveness of burst mode frequency and switching frequency at light load condition are discussed and verified via experimental results. The experimental results show that the efficiency can...
A decentralized control strategy is proposed to coordinate multiple shunt active power filters (APFs) to improve power quality at the point of common coupling (PCC) in terms of power factor correction and harmonic elimination. Under the proposed control strategy, each APF uses locally measured current signals to decide the amount of power quality improvement task, which is limited to its power rating...
This paper introduced a soft starter of asynchronous electromotor which is based on magnetically controllable reactor, designing three new soft-start methods on the basis of traditional current limit starting and voltage step ramping starting, among which the mode of torque close-loop can start or stop pump load without impact. It can also reduce the water hammer and the vibration of pipeline. We...
An n-level flying capacitor (FC) based active neutral point clamped (ANPC) converter is discussed in this paper. The converter is based on an arrangement of a three-level ANPC converter and a number of two-level cells creating an n-level line-to-neutral waveform. The converter is operated under a phase-shifted carrier pulse-width modulation (PWM). The mathematical model for the DC-link capacitors...
A kind of RPC (Railway Static Power Conditioner) was discussed to govern power quality in V/V electric traction system of the high-speed railway at 350Km/h, which is used to carry out the comprehensive compensation of negative sequence, reactive power and harmonic currents in the traction substation. The paper analyzed the negative sequence compensation principle, and a dual-loop control strategy...
Multilevel power converters make it possible to use mature but voltage-limited power semiconductors in high voltage, high power industry and utility applications. Different from high frequency approach, the concept of direct output synthesizing provides efficient power conversion with the advantages of better harmonic cancellation and compact ac filtering. Conventional multilevel inverters, including...
Multi-module cascaded multi-level inverters are more and more widely used in high voltage and large power industrial applications. Its unique topological structure requires multi-channel drive pulse. Therefore, generating multi-channel drive pulse becomes one of the key issues. This paper presents a digital implementation method, which combines double and multicarrier horizontal phase shift PWM modulation...
This paper proposes a universal approach to analyze and determine the stability of multi-module distributed power electronic systems. The modeling of cascaded, paralleled and inter-connected systems was carried out to analyze the affecting factors of the stability. The method was proposed that the stability of systems can be determined by impedance measurement. The most recent results from simulations...
With increased wind power penetration level, new grid codes generally require the wind power system be able to stay connect during a grid voltage sag. Voltage sag generator (VSG) is a kind of device used to simulate the fault condition so as to verify the reliability and stability of wind power system during low voltage ride-through (LVRT). Firstly, two existing VSG topologies which are based on the...
A research on differences of latest Grid Code requirements for wind farm integration between China and selected EU countries are conducted. The similarities and differences of these Grid Codes in the aspects of low voltage ride-through ability, transient fault ride-through requirements, negative phase sequence requirements and reactive power control requirements are compared. The main causes of these...
In order to research the actual state of the wind power generation in the laboratory, a 22KW wind power generation experimental platform using SCIG was developed. The platform includes: wind simulator, L-speed gear box, back-to-back converter, filter inductor and a 10-ton platform base. The wind simulator is composed by ABB's ACS550 inverter, three-phase squirrel-cage induction motor and reduction...
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