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A high frequency dc link single phase PWM rectifier is proposed in this paper. It has the advantages of high efficiency, high power density, high reliability, and wide range of output voltage etc. A dual loop control scheme for this PWM rectifier is developed, which includes an inner PR (Proportional-Resonant) current controller and an outer PI (Proportional-Integral) controller. Nearly unit power...
3kW Single Phase Soft-switching PFC is designed and produced based on ZVT-PWM soft-switching technology, adopting UC3855A average current-mode control chip. Substantial theoretical studies and prototype trials prove that the input current could properly make tracks for the changes of input voltage, effectively suppress influence of harmonics on power grid, improve the power factor and then help to...
This paper presents the idea of utilizing large voltage ripple with small capacitance for energy storage in LED circuit, instead of large capacitance with small voltage ripple. A typical Single-Stage PFC converter with small capacitor is adopted. The presented converter has high input power factor and low output voltage ripple at the same time. Calculation method of main parameters are derived. In...
A circuit topologies family of single-stage parallel uninterruptible AC/DC converter with high power factor are presented. The topology includes four sections, i.e. full bridge rectifier, parallel converter with power factor correction(PFC), uninterruptible power supply and fast output voltage regulation. The converter has lots of advantages such as: single stage power conversion, uninterruptible...
In this paper, based on the analysis of the equivalent output impedance and parallel model of single phase SPWM inverter, a decoupling control strategy of parallel inverter system is proposed. The output power is decomposed into active power and reactive power to regulate the amplitude and phase of the reference signal. A three-phase balanced current is constructed according to the instantaneous reactive...
The VF (voltage and frequency control) droop control techniques are used to set the VF reference value which allows the operation of multiple VSCs in parallel to share the loads and regulate system voltage and frequency separately. In this paper, the characteristics of four VF control strategies which are: open loop VF control; VF control scheme with voltage feedback in abc reference frame; VF control...
To help the three-level PWM rectifier maintain good performance when the three-phase grid voltage is imbalanced, this paper analyzes the influence of grid voltage imbalance on the input current and the output voltage of PWM rectifier. On the basis of analyzing the instant reactive power and active power of the system, this paper adopts a method of the dual current regulations to control the imbalance;...
The conventional method by power regulation to restrain the circulating current is affected by the parallel impedance and has other disadvantages in the response speed and harmonic component of circulating current, etc. The strategy to restrain circulating current based on tracing transient average current feedback was proposed in the paper by the combination of tracing transient average current feedback...
This paper investigates the detailed model, control and simulation of a multilevel inverter-based STATCOM. Nine-level STATCOM is selected as a demonstration. Basic structure and operation principle of the cascade multilevel inverter are explored, firstly. The cascade multilevel inverter consists of four single-phase full bridges in which each bridge has its own dc source, respectively. The phase-shifted...
Gird-connected photovoltaic (PV) inverters with the function of active power filter (APF) not only inject the active power into the electric network, improve the power quality, but also make full use of their capacity, especially in the cloudy day or the night. An improved implementation of the amplitude limiting control of the three-phase grid-connected PV inverters is presented. To achieve the optimally...
Converters operating in discontinuous-conduction-mode (DCM) and continuous-conduction-mode (CCM) are suitable for light and heavy loads respectively. A novel tri-state boost PFC converter is proposed in this paper, which benefits with reduced line current harmonics, improved power factor and wide load variation range, while preserves cost, size and fast response advantages of conventional DCM boost...
This paper describes an active and reactive power regulating system based on a cascaded converter. The system is intended for power leveling of renewable energy sources, as well as for improving power quality and reliability of a power distribution system. The active/reactive power control and the DC side voltage control concentrated in this paper are indispensable for the system's proper operation...
The active islanding detection methods (IDMs) can effectively mitigate the islanding non-detection zones (NDZs) compared with passive IDMs in the inverter based DG systems but the improvement depends highly on the interface control schemes. In this paper, different reactive power variation based IDMs, including Active Frequency Drift method (AFD), Slip Mode Frequency Shift Method (SMS) and Sandia...
Due to the inherent complexity, traditional ant colony optimization (ACO) algorithm is inadequate and insufficient to the reactive power optimization for distribution network. Therefore, firstly the ACO algorithm is improved in two aspects: pheromone mutation and reinitialization strategy. Then the thought of DE is proposed to be merged into ACO, and by producing new individuals with random deviation...
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...
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...
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...
The choice of Doubly-fed induction generator (DFIG) operation strategy has a significant impact on voltage stability. Now there are two types including constant-power factor and constant-voltage control and their essential differences are different control strategies between the scheduling of reactive power and voltage control. The article presents control strategies of wind generator on two kinds...
Since the penetration of wind power in electric power supply is increasing greatly, it is urgent to study the impact of wind power on the transient stability of electric power system. In this paper, a model for a simple electric power system with a large wind power plant is constructed, in which, a wind power plant which consists of 6 Doubly Fed Induction Generator (DFIG) transmits power to the system...
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