Zou Yunping

Novel Hybrid Cascade Asymmetric Inverter Based on 5-level Asymmetric inverter

A novel hybrid cascade asymmetric inverter is developed in this paper. The novel inverter is based on connection of multiple single-phase asymmetric 5-level inverter modules. With the dc bus voltage ratio V1:V2=1:2, the phase voltage of the novel inverter with two modules per phase will output 13 voltage levels. A new hybrid asymmetric control technique for the inverter is proposed. Spectral analysis of the phase output voltage is carried out. According to the spectral analysis, there is no real power exchange between modules in a phase leg. A two-module three-phase inverter was constructed in the laboratory, experimental results are presented as well as comparison with hybrid diode-clamp cascade inverter is given

Research on AC chopper power module with module parallel control

Based on the single-phase AC chopper circuit, a novel AC chopper topology with the corresponding PWM method is proposed. To improve high voltage performance, dual- loop control including both mean voltage and instantaneous voltage is used in this paper, with duty-cycle feed-forward. At last, parallel operation control method is used to realize the current sharing. The experimental results verify the correctness and feasibility of the proposed topology and control scheme.

Design and research of three-phase power electronic load

Based on back-to-back structure of two pulse-width modulated (PWM) voltage-source converters (VSC) combined by capacitor of DC side, three-phase power electronic load is presented. These two voltage-source converters are respectively simulation converter which links tested power source as simulated load through direct current control of ac side, and grid connection converter which combines grid to transform power from tested power source back to grid in regenerated model. In this case, besides the capability of simulating majority of practical loads, such as resistive loads, inductive loads, capacitive loads, function of three phase power electronic load has obvious effect of saving energy, moreover, advantages like swift dynamic response, practical utility and convenient management supply wide applicable prospect towards this device. From this paper, the basic topology of three phase power electronic load is described in detail; then control strategies of back-to-back voltage-source converters are presented; eventually simulation waves of both simulation converter and grid connection converter are given to show excellent characteristics of this system.

The Vector Control Strategies for Multiphase Synchronous Motor Drive Systems

This paper studies the multiphase synchronous motor with symmetrical windings and multi-Y-windings displaced in turn by ¿o separately, the mathematical descriptions about which can be concluded as two models: single-windings and multi-windings models in M,T frame. Based on these models, the multiphase vector control strategy and multiphase multi-ply vector control strategy are proposed, so as to achieve the gas-flux-oriented control for multiphase synchronous motor in two models of mathematic descriptions. The corresponding control frames are established for the multiphase synchronous motor drive systems. Taking the 12-phase synchronous motor with four Y-connected 3-phase symmetrical windings displaced in turn by 15° as an example, the 4-ply control principle is deduced. The experiment results show the system has perfect control and operation performance under such a control strategy.

A Study of Dual-loop Control Scheme and Corresponding Neutral-point Voltage Balance Control Method for Three-level PWM Rectifiers

The mathematical model of the three-level PWM rectifiers is set up in this paper. By comparing it with the model of DC motors, some similarities are established. Based on the state feedback decoupling, the dual-loop close control scheme of DC motors is implemented to three-level PWM rectifiers. As a result, the three-level rectifier has favorable dynamic and steady state performance, sinusoidal input current and unity power factor. Besides, a method is proposed to control the neutral-point voltage charge unbalance, which is an inherent problem of three-level inverter. The redundant positive switching states or negative switching states of small vectors are selected according to the direction information of input current of each phase as well as the ripple of neutral-point voltage. Finally, experimental results verify the feasibility and validity of dual-loop control scheme and neutral-point (NP) voltage balancing control method.

Research on cascaded multilevel inverter and its application in STATCOM

Because of the broad application of multilevel converters in the high-power area, a cascaded multilevel voltage-source inverter with phase-shifted SPWM (PS-SPWM) switching scheme is proposed as a static synchronous compensator (STATCOM). This can eliminate the bulky and weighty transformers and reduce power loss. In addition, the equivalent carrier frequency can be doubled and the output harmonics will be reduced compared with the STATCOM being put into operation. The operating principle and control methods are analyzed in detail and the feasibility is validated by simulation with MATLAB.

A performance improvement technique for single-phase PWM rectifier

This paper calculated and analyzed the main reasons for distortion of supply current. Then a novel control method which added an output current sampling was present. According to use the value of output current the 100Hz ripple voltage in the output voltage was mostly eliminated, and the waveform of supply current was improved; Meanwhile the output current was feed-forward to the reference value of supply current control loop, so the dynamic performance was also improved. The theoretical analysis is verified by simulations and experiments.

A DTC Algorithm for Three-level Induction Motor Drives System Based on Discrete Space Vector Modulation

In this paper, an uniform mathematic model of three-level inverters feed induction motor drives system has been constructed. Based on the application of the discrete space vector modulation (DSVM), a DTC strategy of three-level inverters induction motor drives system is proposed. With DSVM-DTC algorithm, the neutral-point (NP) voltage balancing problem and high dv/dt of output voltage is restrained. The proposed algorithm does not deteriorate dynamic performance of traditional DTC schemes, and does not increase switching loss at the same time. The experimental results verify the correctness and feasibility of the proposed control scheme.

Research on three-phase inverter control method with full-decoupling

The scheme of full-decoupling in circuit and magnetic circuit is proposed, in terms of the conventional inverter not matching any unbalanced loads. Voltage independence control and closed-loop control can be done by PLL, respectively in each phase, to let the output phase track the references, which ensures the inverter phase to symmetry. This paper discuss the method of phase feedback control mainly. Experiment results of 12 kW three phase inverter show that the circuit design is feasible. It is suit of high power inverter.

A feed-forward compensation strategy of SPWM Matrix Converter under abnormal input voltage conditions

The feed-forward control scheme based on SPWM matrix converter is proposed. As a device without DC line, the AC line side abnormal inputs can deteriorate its output characteristics. Tri-carrier is prior modulated by measured envelop of line voltages, to let the pulse width of SPWM get different compensation in each pulse. This paper analyzes compensation principle, introduces realization method, and compares output behaviors of without compensation with compensation by Matlab/Simulink. Analyses and simulations show that the scheme modifies effectively output characteristics of MC (Matrix Converter) under abnormal input conditions. It is simple not only easy to realize through hardware but also to digital, and simple algorithm.