Wen Xuhui

Modeling of PM-PM Dual Mechanical Ports Electric Machines

A dual mechanical ports electric machine (DMPM) is presented firstly, which is a special motor with two mechanical ports and two air gaps. The disadvantage of traditional model of DMPM is analyzed without considering the magnet coupling between two air gaps, which will affect the precision greatly. Consequently a new modeling scheme is presented and a model of permanent magnet DMPM is deduced. First, the inductance matrix of the motor is calculated in the natural frame, based on which the model of the special motor is obtained in the synchronous reference frame. Then, the simulations are carried on the new model and traditional model. The results prove that the two models have great difference, so the magnet coupling of two air gaps cannot be neglected

Deep field-weakening control of PMSMs for both motion and generation operation

This paper proposes a new control method for deep field-weakening operation of permanent magnet synchronous machines (PMSMs). With single current regulator (SCR) and voltage angle control (VAC), the new method can achieve much higher field-weakening speed rate than conventional methods. The SCR-VAC method makes full usage of the DC bus voltage so that maximum torque output can be obtained. It is shown by stability analysis that, d-axis current control should be used for motion and q-axis current control for generation. Conclusions are verified by experimental results.

Permanent magnet dual mechanical port machine design for hybrid electric vehicle application

The dual mechanical port (DMP) machine is a new breed machine with two rotors. Because the two rotors can run at different speed, the DMP machine functions as both a pair of motors and an electrical variable transmission system. When it is used in hybrid electric vehicle, it can perform all the functions as Toyota Hybrid System does, but with more compact and integrated structure [1]. In hybrid vehicle application, dasiaratedpsila power and torque have different meanings from those in fans and pumps. In this paper, a new method to define the DMP machine specifications is proposed. The interaction between different flux loops is analyzed by FEA. A DMP machine prototype is developed. Experiments conducted verify the design.

A novel fundamental voltage amplitude linear output control strategy of SVPWM inverter in the overmodulation region

Generally, the overmodulation techniques for space vector pulse width modulation (SVPWM) inverters need store lots of date in the controller beforehand, which makes a huge memory while the control resolution is not perfect. Based on amplitude control of the reference voltage vector and the vertex voltage vectors, this paper presents a novel digital over-modulation control strategy for SVPWM inverters, which can manage the transition from the linear control range to six-step operation smoothly. With avoiding the necessity of the stored data implementation, this strategy is simple and very suitable for practical digital implementation. The mathematic analyses show that the output fundamental voltage amplitude is linear proportional to the modulation index. In addition, this paper analyses the harmonic components, and the total harmonic distortion (THD) of the output voltage is compared with that of other strategy too. Both math analyses and experimental results, obtained by DSP board, verify that this strategy is very useful for the induction motor with the linear fundamental voltage output gain, low THD and simple application.

One-cycle controlled DC-DC converters operating with nonlinear power load

This paper applies the one-cycle control method to a boost converter operating with a kind of nonlinear load, constant power load. The constant power load is modeled theoretically, and model parameters are given in quantity. Transfer functions of the boost converter power stage with a constant power load are deducted, and a small-signal model of the one-cycle controlled current inner loop is presented. To maintain the output voltage following the reference accurately, an outer voltage loop with a compensator is constructed. Step responses of the system with different compensators are compared, and the compensator with one zero and two poles are an appropriate selection. Simulation results confirm that the one-cycle controlled boost converter operating with the constant power load can follow the reference stably and rapidly

Research on field-weakening control of multiphase permanent magnet synchronous motor

Field-weakening control is also an important issue for multiphase motors when used in electric vehicles which require wide speed range. Since the multiphase motor is a multidimensional system, therefore field-weakening control must be operated on both the fundamental subspace and other harmonic subspaces simultaneously. In this paper, firstly the reference voltage vector limit of the five-phase permanent magnet synchronous motors (PMSM) fed by the five-phase voltage source inverter (VSI) is analyzed and determined, then the field-weakening control strategy and the determination method of reference current commands based on the multidimensional-orthogonal-decomposition vector control and the multiphase carrier-based PWM is presented. Finally, Simulation results verify the correctness and feasibility of the proposed field-weakening control strategy.

Comparison of two different structure of permanent magnet dual mechanical port machine

There are two types of permanent magnet dual mechanical port electrical machine (DMPM), namely, non-uniform magnetic-field DMPM and uniform magnetic-field DMPM. In this paper, both the equivalent-magnetic-circuit method and FEM are adopted to compare the characteristics of the uniform field DMPM to the non-uniform field DMPM such as electromagnetic coupling etc. The analysis indicates that both outer and inner air gap flux density of uniform field DMPM are higher even with the same volume of magnets; the electromagnetic coupling between stator and inner rotor is stronger. Because the non-magnetic material is used in the outer rotor of uniform field DMPM, Ld, Lq decrease, the torque coupling between the stator and the inner rotor of uniform field DMPM is not significant. One uniform field and one non-uniform field DMPM prototypes are manufactured. The simulation results are verified by experiments.

Optimal system efficiency operation of dual PMSM motor drive for fuel cell vehicles propulsion

Electric Vehicles (EVs) develop rapidly with the concerns of gas emission and energy crisis. Electric Motors, those are used for EV propulsion must have high efficiency for maximum utilization of the energy from batteries and/or fuel cells. This paper aims to address how to achieve the optimal system efficiency of multi-motor drive system, which has not been addressed previously. Based on the measurement or estimation of the real-time load condition and the efficiency optimization strategy, Digital signal processor (DSP) coordinates the work between the two motors and setts reasonable working mode of the inverter, and then improves the overall efficiency of the propulsion system notably. Fault-tolerant strategy base on the master-slave motor concept is also discussed to ensure the reliability of the system both under health and various faulty conditions. The paper presents the details of the experimental setup and measurement for the improvement of the system efficiency. Data obtained from this study will provide the preliminary understanding on how to achieve the optimal efficiency of multi-motor drive system.

Investigation of parallel connection of IGBTs

IGBT device has the advantages of high current, simple gate drive, high-frequency performance and etc; therefore it gains widely application in the drive system of electrical vehicles. However, the current carrying capacity, cost and reliability limit its further application in the higher power level, such as 160 KW and further. One of the key technologies to overcome such limitation is the parallel connection of IGBT devices. This paper investigated the effects of some issues such as topological structure, gate drive resistance, snubber circuit and so on. The effects are verified by experiments and some important conclusions are presented.

A new fuzzy logic based search control for efficiency optimization of induction motor drives

Operated under the rated conditions, the induction motor is highly efficient. When the rated conditions are not satisfied, the efficiency is greatly reduced, so the efficiency optimization has significance for economic saving and reduction of environmental pollution. This paper summarizes the main efficiency optimization control strategies appearing recently, and proposes a new fuzzy logic based minimum input power search control strategy, which makes full use of the results of loss model control. Unlike the other fuzzy methods that need simulation calculation to get the coefficients of the scaling factors, the gains derivative method of this strategy is simple and effective. The simulation verifies that it is very fast and highly precise, and should be widely used in the efficiency optimization control for IMs