Zhao Yanlei

Research on a Novel Digital Photovoltaic Array Simulator

In order to make the design and optimization of solar energy systems convenient, it is very essential to choose the suitable engineering mathematic model of solar cells. A convenient and practicable engineering mathematic model of silicon solar cell is offered in this paper, which is based on photovoltaic array output I-U characteristic curve. Piecewise curve fitting method is also presented to simulate the photovoltaic array characteristic curves. A new digital photovoltaic array simulator with Buck converter is designed in detail. The designed simulator uses dual-loop control with PI regulator, which greatly enhances the systems dynamic performance and steady-state accuracy. The feasibility and rationality of the design are verified by the results of simulation and experiment. It can be used in replacement of actual photovoltaic arrays to provide a controllable environment for research and design of photovoltaic inverters and control systems.

Research on maximum power point tracker based on solar cells simulator

The output power of solar cells varies with variable temperature, light intensity and loads. In order to solve the shortcomings such as long time and high cost of using solar cells to experiment, this paper successfully uses a DC power supply and a variable resistor to simulate the solar cells output characteristic curve, its feasibility is analyzed theoretically. The basic principle of the maximum power point tracking (MPPT) is described in detail. An improved disturbance method with variable voltage step is introduced, it inherits the advantages of traditional disturbance voltage method, overcomes the shortcoming of slow response of traditional method, reduces the power loss caused by maximum power point due to continuous disturbance, and realizes the maximum power point tracking for solar cells. The proposed method improves the systems speed and efficiency. The experimental results show that the system can track the maximum power point accurately and quickly.

A new robust algorithm to improve the dynamic performance on the position control of magnet synchronous motor drive

This paper puts forward a novel position controller based on active-disturbance rejection controller (ADRC) theory to ensure high dynamic performance of magnet synchronous motor (PMSM) servo system. By using the extended state observer (ESO), the position controller can accurately estimate the derivative signals and precise decoupling of PMSM is achieved. In addition, the proposed strategy realizes the disturbance compensation without accurate knowledge of PMSM parameters. By means of the tracking differentiator (TD) and nonlinear state error feedback control law (NLSEF), the PMSM servo system realizes nonlinear control, that is, if the error is smaller, then the gain is bigger, or vice versa. The simulation results show that the proposed controller ensures good robustness and adaptability under modeling uncertainty and external disturbance. It is concluded that the proposed topology produces better dynamic performance, such as small overshoot and fast transient time, than the conventional proportional/integral/derivative (PID) controller in its overall operating conditions.

Design of three-phase intermediate frequency aviation power based on single chip microcomputer

A three-phase intermediate frequency aviation inverter power with single chip microcomputer and SA8282 as its main controller is designed in this paper. The overall structure of the proposed system is given. The working principle and design method of the main circuit are presented in detail. Among the control circuit design process, the generation of SPWM waveforms, the main parameters design of SA8282, the digital PI regulation and the software design process are analyzed. The proposed control strategy has been implemented on a 9KVA, 400Hz three-phase power supply. Experimental results show that the three-phase output voltage waveforms are quite good, the performance of the supply meets the demand.

A speed observer for speed sensorless control of induction motor

This paper proposes a novel speed sensorless control strategy for induction motor drives based on active-disturbance rejection controller. Based on the field-oriented control technique, the dynamic model of q-axis current is a first order nonlinear state equation including synchronous speed and rotor speed. The synchronous speed and rotor speed is regarded as the internal disturbance of q-axis current. According to the active-disturbance rejection controller theory(ADRC), the system uncertainties and disturbance could be estimated and compensated instantaneously. Once the disturbance including rotor speed is estimated in real-time, rotor speed is also observed from it. With the help of the extended state observer(ESO) and state error feedback control law (NLSEF), the speed observer proposed in this paper realizes the disturbance compensation accurately without the knowledge of the exact system parameters. Simulation results show that the rotor speed can be accurately estimated from 0r/min to rated speed with load or not. A good dynamic and static performance of the sensorless vector control system is achieved by this method.

Single phase photovoltaic grid-connected inverse power system based on DSP

As the energy crisis and the pollution are serious, the exploitation of solar has received more and more attentions. The configuration and principle of photovoltaic grid-connected power system are analyzed in detail. The method of maximum power point tracking is designed and the control principle of voltage and current double closed-loop is analyzed in this paper. At the same time an improved phase locked tracking method combined with software and hardware is presented. The experimental results show that the current waveform of grid-connected inverter has the same frequency and phase angle with the grid voltage, the power factor of grid-connected inverter is 0.999, which meets the design requirement entirely.

Research and design of Power Conditioning System for Alkali Metal Thermo-Electric Converter

A PCS (Power Conditioning System) for AMTEC (Alkali Metal Thermo-Electric Converter), which is composed of DC/DC converter and DC/AC converter adapting to volt-ampere characteristic of AMTEC, is researched and designed. Two parts of the PCS are separated by a high frequency transformer, so the disadvantage of low frequency one is eliminated. Using phase-shift ZVS (Zero Voltage Switching) full bridge and voltage closed loop control, DC/DC converter converts output voltage of AMTEC which fluctuates in a wide range to a steady voltage. DC/AC converter is controlled by optimal SHEPWM (Selective Harmonic Elimination PWM) technique, which makes THD (Total Harmonic Distortion) of the inverter being filtered as objective function and uses penalty function algorithm for optimized calculation, so the optimal switching angle of the inverter can be obtained. The experimental result shows that the PCS has the advantages of wide voltage input, high converting efficiency and low THD in output voltage. The PCS proposed in this paper will be useful for the development of AMTEC with high power and high efficiency.