Feifei Bu

Wide-Speed-Range-Operation Dual Stator-Winding Induction Generator DC Generating System for Wind Power Applications

This paper presents a wide-speed-range-operation dual stator-winding induction generator (DWIG) dc generating system for wind power applications. In this system, the dc bus on the control-winding side and the dc bus on the power-winding side are connected in parallel to further widen the speed range of the constant dc voltage output, especially at low speeds. Based on the control mechanism of the DWIG and the instantaneous power theory, a control-winding-flux-orientation control strategy is employed. In order to improve the wind energy conversion efficiency at low wind speeds, the generator efficiency optimization method is investigated. The experimental results from a 20 kW/600 V prototype show that the proposed generating system can output the constant dc voltage in a speed range of 1:4, and the generator efficiency in the low speed range is improved, which both bring the advantages for wind power applications, such as expanding the scope of the wind energy utilization and capturing much more wind energy.

Study and implementation of a control algorithm for wind turbine yaw control system

In order to capture the maximum wind energy and improve the efficiency of wind generation system, the yaw control system is researched. This system takes the initiative to windward. According to the control algorithm proposed in this paper, yaw angle is calculated by the DSP, and the drive signals of stepping motor are generated. The stepping motor is controlled by the micro-stepping control to drive the yaw mechanical device to make the wind turbine windward. Through this way, the yaw control system can track the wind direction automatically. Experimental results show that based on the proposed control algorithm and DSP control, the performance of yaw system is great and the operation precision of stepping motor is high. Therefore, the yaw system has the ability to track the wind direction quickly and exactly.

An indirect-field-oriented dual stator-winding induction generator for the wind power system applications

This paper presents a novel dual stator-winding induction generator (DWIG) system used in wind power generation. Based on the control winding field orientation, an indirect field-oriented control strategy is proposed for a simple realization to control the DWIG system. The voltage control mechanism of the DWIG system over variable-speed operation of the power system is analyzed in detail. The component of the control winding current which are produced on the control winding terminal voltage vector and its normal component determine the instantaneous reactive power and active power, and further influence the DC voltage of the load connecting across the power windings and that of the static excitation controller (SEC) on the control windings. Simulation and experimental results on a 20kW/750rpm DWIG are provided to demonstrate the effectiveness and accuracy of the proposed control strategy.

Analysis, Comparison, and Discussion of Control Strategies for Dual Stator-Winding Induction Generator DC Generating System

This paper presents four types of control strategies for a dual stator-winding induction generator DC generating system as well as their analysis, comparison, and discussion. These four types of control strategies include control-winding flux orientation control, control-winding voltage orientation control, control-winding direct power control, and instantaneous slip frequency control (ISFC). The ISFC strategy is described in detail for first employed in dc generating application, and the other strategies are briefly introduced and their performances are also summarized for comparison. The characteristics of control strategies are compared from four aspects: 1) system performance; 2) key components; 3) control principles; and 4) applications. From the comparison results, it can be inferred that all these four types of control strategies have some advantages, especially the ISFC. They can find suitable applications.

The magneto motive force of a novel dual stator-winding induction generator

The magneto motive force (MMF) of a novel dual stator-winding induction generator (DWIG) for wind power application is analyzed in this paper. There are two sets of windings embedded in the stator slots. One is 3-phase control winding, and the other is 6-phase power winding. A static excitation converter (SEC) is connected to the control winding to provide the variable excitation power to the generator. The 6-phase power winding, feeding a 6-phase rectifier, is designed as two 3-phase star windings spatially shifted by 30° electrical to decrease the harmonic MMF. Based on the analysis on the harmonic current components of the two sets of stator windings, the harmonic MMF in this generator is investigated, and the relationship between the harmonic current and harmonic MMF is consequently disclosed. The harmonic MMF in a 18 kW DWIG prototype is calculated, and the correctness of harmonic MMF analysis is verified.

A PMSM rotor position estimation with low-cost Hall-effect sensors using improved PLL

For the detection of rotor position in Permanent Magnet Synchronous Motor (PMSM), this paper presents an improved estimation method with switch-Hall-effect sensors. This algorithm can reduce the position error effectively originating from the process of estimation. In the course of estimation, coordinate transformation and an improved orthogonal PLL (Phase locked loop) which can decrease the oscillation availably of velocity are adopted successively. In order to validate the superiority of the method, simulations based on MATLAB/Simulink with high-precision sensor, typical PLL and improved PLL are built here. Analysis of the results and comparisons between waveforms of above models indicate the feasibility of the proposed strategy.

An Integrated Topology of Charger and Drive for Electric Buses

To improve reliability and realize electric isolation, an integrated topology of the charger and drive for medium/high-power electric buses is presented in this paper. The proposed integrated topology can solve the voltage matching problem between the power grid and the battery voltage and between the battery voltage and the drive system. The integration can be realized by using the common hardware of the charging system and the drive system, which can reduce the cost and weight of the whole system. To improve the power level, a three-phase combined full-bridge converter based on the magnetic-combination transformer is adopted in the charging system, which has a single-stage power-factor-correction function, electric isolation, and no electrolytic capacitor. To better reflect the integration, the motor drive system adopts a single-stage boost dual-inverter that is the reconfiguration of the magnetic-combination transformer and the 3-H bridge converter in the charging system and few extra components. The drive system has a single-stage boost/buck function, high reliability, and strong fault-tolerant ability. The proposed integrated topology, which can realize a charging function and a driving function, has been analyzed in this paper. Finally, the experimental results verify the feasibility of the integrated topology.

Control and Performance of Five-Phase Dual Stator-Winding Induction Generator DC Generating System

In this paper, the five-phase dual stator-winding induction generator dc generating system with the static excitation controller is presented, and two kinds of control strategies for this system are proposed. In this generator, the cage-type rotor is employed, and two sets of five-phase windings are placed in the stator, namely, the power winding and control winding. Using the instantaneous power theory, the control-winding-flux-oriented control (CWFOC) strategy without harmonic injection is obtained. To improve power density, the CWFOC with harmonic injection is proposed as well. For these two strategies, the detailed implementation is studied. The results (simulation and experiment) support the correctness and effectiveness of the proposed control strategies, and the corresponding results show that, using the CWFOC strategy with harmonic injection, the output power of this system can be improved by about 11%.

Three-Phase Single-Stage AC–DC Converter Based on Magnetic-Combination Transformer With Power Factor Correction

To improve the power factor and reliability for medium/high-power supply, a three-phase single-stage ac-dc converter based on magnetic-combination transformer with power factor correction (PFC) function is presented in this paper. According to the three-phase instantaneous power balance principle and the concept of the magnetic-flux superposition, a novel magnetic-combination transformer is proposed, which can make three-phase symmetrically and sinusoidally fluctuant power add to be constant. Therefore, the induced voltage of the secondary winding is constant. To realize sinusoidally fluctuant power in the input stage, dc-link filter capacitance can be reduced to a several-microfarad level. Single-stage PFC function, no electrolytic capacitor, and constant output voltage can be realized in the converter. The principle and the structure of the novel magnetic-combination transformer are analyzed in detail in this paper. Simulation and experimental results are presented to verify the feasibility of the proposed converter.

Control strategy for five-phase dual stator-winding induction generator DC generating system

This paper presents a dc generating system based on the five-phase dual stator-winding induction generator (DWIG) with the static excitation controller (SEC), and also investigates its control strategy. In this five-phase DWIG, the cage-type rotor is employed and it has two sets of five-phase stator windings (power winding and control winding). Based on the instantaneous power theory, a control winding field oriented control (CWFOC) strategy considering third-harmonic injection is proposed. The simulation results support the proposed control strategy, the five-phase DWIG dc generating system can have a good performance.