Advanced Materials Research Vols. 732-733

Abstract: The eddy current retarder generator / starter integrated system is a vehicle intelligent system which can be used as vehicle starter, power generation. The system can reduce the energy consumption of the car, extends battery life, and improves the stability of the brake system.

Abstract: Permanent magnet synchronous motors(PMSM) as a representative of high efficiency motor was being used widely in the area of medium and small-sized power, high-accuracy,high reliability and wide-scope speed governing servo system.Otherwise,because traditional PI controller can not satisfy the high-performance of PMSM servo system,Fuzzy self-tuning PI(Fuzzy-PI) control method was used in this system, and proportion and integral parameter of PI controller is optimized by fuzzy logic.By simulation experiment, it was proved that Fuzzy-PI method had more steady and less q-axis current pulse to PI control in the transition procedure of PMSM governing.

Abstract: Dramatic wind speed variations result in the fluctuations of output power in DFIG. This paper presents a pitch control to suppress DFIG Rotor-side active power fluctuations. Though pitch angle changes too quickly could result in generator power fluctuations, the pitch control adopts PID controller and an angle rate limiter to prevent rapid pitch angle changes. The pitch control strategy is simulated by Matlab simulation platform, and the results have shown the correctness and validity of the pitch control.

Abstract: The switch reluctance motor (SRM) speed control system is often difficult to control due to its nonlinearities and parameter variations. In this paper, a fuzzy logic control (FLC) system has been presented to speed control of the SRM. The control system is composed of speed controller and current controller. The main task of the speed controller is to provide the appropriate control signal to the current controller based on the difference between the desired speed and the actual speed of the motor. In the speed control part, the fuzzy controller is used to reject the unknown and uncertain parameters in the SRM and in the load torque. The current controller evaluates the difference between the actual and the desired phase current and implements hysteresis current control. Simulation results demonstrate the effectiveness of the proposed control strategy under different operating conditions of the SRM.

Abstract: A simple frequency response model is generally used in UFLS (under-frequency load shedding) design, without considering the impact of voltage on the frequency. In fact, in the case of large active and reactive shortage power, the system will suffer from the low voltage problem by the emergence of low frequency, which easily leads a large number of motors tripping due to low voltage protection trip in the UFLS process. The influence on UFLS is compared and problems needed to solve are put forward.

Abstract: In order to improve the torque control performance of permanent magnet synchronous motor, variable frequency variable speed control technology, vector control technology, direct torque control technology and sensorless control technology were analyzed. The fuzzy + PID control technology used in permanent magnetic synchronous motor was introduced in detail. The conventional sliding mode observer based on the counter electromotive force estimate control technology and the structure of improved sliding mode observer was given separately. The fuzzy + PID control technology and improved sliding mode observer control technology proposed could improve the dynamic performance and static performance of the permanent magnet synchronous motor.

Abstract: A novel power limiter based on Newton-Raphson method is proposed in this paper for the Doubly-fed Induction Generator (DFIG) under the conditions of unbalanced grid voltage drop. Unlike the existing power limiters, which provide an approximate estimation of the maximal reactive power at the cost of introducing a large error in achieving its control target, ours formulates the design of power limiter into an optimization problem which tries to maximize the DFIG’s reactive power towards its two decisive factors: limited rotor current and rotor side converter’s output voltage. Finally the Newton-Raphson method is exploited to find the global maximum of the proposed optimization problem. Consequently, the proposed power limiter could more accurately determine the DFIG’s maximal reactive power without any loss of the accuracy in achieving its control target. Simulation results on a 1.5MW DFIG shows the efficacy of the proposed power limiter for DFIG under the conditions of unbalanced voltage drop.

Abstract: The load characteristic analysis of permanent magnet synchronous generator is presented. An internal impedance mathematic model of the generator was built with phasor analysis method for analyzing the relationship between exterior voltage characteristic or voltage regulation rate, active power and armature reactance. The research results demonstrated that the internal impedance of generator has both current and power factor angle negative feedback characteristic, which makes the voltage regulation rate be improved to a certain extent and the improved effect lying on both the direct-axis armature reactance under condition of an inductive load and the quadrature-axis armature reactance under resistive load. Additionally, an optimal range of the armature reactance being of less voltage regulation rate was determined according to numerical calculation and analysis. An experimental result based on the experimental measurement and data analysis of exterior voltage characteristic corresponds to the theoretical calculation demonstrated the correctness of the research model based upon the armature reaction analysis. Those can provide the theoretically guidance to the electromagnetic design of permanent magnet generator.

Abstract: In the field-oriented vector control system of permanent magnet synchronous motor (PMSM), the performance is directly dependent on the accuracy of motor parameters. Because of nonlinear factors of the inverter, the difficulty in accurate compensation of voltage error and low accuracy of measurement are problems which exist in stator resistance identification approach based on traditional DC voltmeter-ammeter method. In this paper, the ordinary least squares method based on simple linear regression model is used to finish the automatic measurement of stator resistance. It is verified that the method has higher measurement accuracy according to the experimental result. Furthermore, nonlinear factors of the inverter are not needed to be taken into account using the method, which has comparatively strong practicality in engineering.

Abstract: A prototype thermocompressor driven by linear motor was setup and experimental tudied. Peak-peak pressure in the system was influenced by the regenerator, the heating temperature and the gap clearance between piston and cylinder. The optimal frequency of the system was determined by spring constant and total mass of piston, shaft and moving iron. The peak-peak pressure was found to change little with filling pressure when the heating temperature was lower than 250°C, employing with N2 or He4 as the working substance. But when the heating temperature was higher than 250°C, peak-peak pressure increased with filling pressure. Besides, Helium4 was found to perform better than Nitrogen as the working substance. For heating temperature of 650°C and cooling temperature of 40°C, the peak-peak pressure could reach 0.412MPa with pressure ratio of 1.13 when the filling pressure was 2.2MPa, which could be used to drive the pulse tube crycooler (PTC).