Ruixiang Hao

A new single-phase to three-phase cycloconverter for low cost AC motor drives

This paper presents a new single-phase to three-phase cycloconverter suitable for driving an induction motor. Using discrete variable frequency technique, a single-phase to three-phase modulation strategy is proposed, the output frequency of this cycloconvertor can be up to half of the input frequency. Only six naturally communicated thyristors are employed, so the resulting cycloconverter-motor drive system is cheap and compact. Software in C and assembly language has been written for real-time control. The simulation based on Matlab/Simulink is used to predict the performance for the cycloconverter and induction motor.

Development and Experiment Research of High-Power Arc Heater Power Supply Utilizing Thyristor Converter

Arc heater can generate high temperature through the transformation of electric energy to heat by means of electric arc discharge between a couple of electrodes. It is most appropriate to reproduce exactly flight conditions of space vehicles. The performance of power supply is vital for the properties of arc heater test. In this paper, the stability of arc heater power supply system is analyzed, and the development, control and experiment of an advanced performance high-power arc heater power supply utilizing thyristor converter are presented. The feed forward plus feedback control strategy is used for the control of power supply, which assures the supply have fast dynamic response and high static accuracy. The power supply is fit for various type arc heaters, for example Huels and Long-Segmented from hundreds of kW to decades of MW power-level.

A novel H6 topology and Its modulation strategy for transformerless photovoltaic grid-connected inverters

With the rapid development of advanced power electronics technology and photovoltaic power systems, transformerless photovoltaic (TPV) inverters have been widely used due to the advantages in weight, size, efficiency and so on. However, there exists common-mode leakage current in TPV inverters, which should be satisfied the DIN VDE0126-1-1 standard. A novel H6 topology (H6-N) with dedicated modulation strategy for the TPV inverter is proposed to make the TPV inverter generate smaller common-mode leakage current comparing with the existed TPV inverter topologies and achieve low total harmonic distortion (THD) of output current. The common-mode voltage (CMV), common-mode leakage current and power losses of the single-phase TPV inverters with H6-N, H5 and HERIC topologies are compared respectively via simulation analysis. Finally, a universal prototype of TPV inverter using H6-N topology is built and tested to validate the effectiveness of the presented topology.

Stability analysis of the shunt regulator in PCU with describing function method

The shunt regulator (SR) is a key part of the power conditioning unit, which is a kind of power supply system for spacecrafts. SR is a strong nonlinear system due to the hysteresis control adopted, but the stability analysis for SR is still ground on the approximate linearization. In this paper, a novel stability analysis method for strong nonlinear systems is proposed based on describing function, which is used to model the nonlinear link of SR. Further, two different conclusions about the stability of SR are drawn, obtained by the approximate linearization method and the describing function (DF) method, respectively. Finally, the simulation and experimental results prove the correctness of the stability analysis method proposed in this paper and discover the limitation of the linearization method for analyzing the stabilities of the nonlinear systems.

The Research and Development Platform for Wind Energy System Used Induction Motor Replacing Wind Turbine

A research platform for wind energy system is developed in this paper. An inverter fed induction motor drive the wind generator replacing a real wind turbine. The power-speed characteristics of a wind turbine are physically implemented by an induction motor drive. For a given wind turbine characteristics, the shaft torque of induction motor is calculated by the given wind speed and measured generator speed. With the rotor flux oriented transformation, the q-axis current of induction motor can be used to control the motor torque, and the d-axis current is used to regulate the rotor flux. Using the space vector PWM algorithm, the 1 GBT inverter drives the induction motor to output the required torque as a real wind turbine. The experimental results show that this scheme is viable and accurate.

Modeling of plasma arc for the high power arc heater in MATLAB

To better develop the arc heater power-supply system, this paper presents an improved plasma arc model, which is formulated from the famous Mayr and Cassie models. Considering real working conditions, the disturbance created by the unstable mass flow rate is taken into account in the arc model, to improve the accuracy. An 18-pulse thyristor rectifier, with constant current output, is used as the arc heater power-supply. The proposed arc model is established in MATLAB/Simulink and the whole arc heater power system is test implemented. The considerable degree of agreement between the simulated and experimental results shows that this arc model can describe both static and dynamic characteristics of real plasma arc with high accuracy.

The control strategy of grid-connected converters in microgrids with unbalanced load

A multi-loop controller for gird-connected voltage source converters with LCL filter is proposed in this paper. The controller consists of three segments - inner predictive current controller, outer voltage vector controller, and the command voltage modifier. The whole controller is applied to converters based DRs in microgrids, and regulate the load terminal voltage with zero steady-state error even under unbalanced conditions. Selected results from simulation studies conducted on the performance of the controller under balanced and unbalanced conditions both in island and grid-connected mode are presented.

VSCF doubly-fed induction generator control strategy and simulation research

This paper describes the mathematical model of doubly-fed induction generator in different coordinate systems and its stator flux oriented vector control technology. On this basis, we use Matlab / Simulink to establish a simulation model system, sub-synchronous speed and super-synchronous speed power generation status are run, the simulation results prove the correctness of the theoretical analysis, and give some guiding significance to the experimental study of the system.

Reference Current Detection and Control for STATCOM under Unbalanced and Distorted Supply Voltage

STATCOM is the state-of-the-art reactive power generator of power systems. This paper presents a novel reactive current detection and control strategy for STATCOM, under unbalanced and distorted supply voltages. To obtain accurate control, several compensation methods are proposed, such as phase-lag compensation, dead-time compensation and control-delay compensation. Finally, a 10 kVA STATCOM based on digital signal processor TMS320F2812 is investigated, and experiment results validate the proposed methods in this paper.

Analysis of electrical characteristics of the four-quadrant converter in high speed train considering pantograph-catenary arcing

Pantograph–catenary disconnection occurs quite frequently in high-speed situations. Pantograph arcing has a significant impact on the contact surfaces and power quality. This article focuses on the effect on the electrical characteristics of the four-quadrant converter of pantograph arcing. An arc model which combines Cassie’s arc model with Mayr’s arc model is built. This article mainly researches the influence of the pantograph arcing on the four-quadrant converter in different durations. Pantograph arcing leads to voltage pulse in voltage, as well as the harmonics in the current of the alternating current side. At the same time, the direct current voltage decreases when the arc occurs. Therefore, it can ultimately decrease the output torque and increase the torque pulsation of the motor.