Speed Regulation Method Using Genetic Algorithm for Dual Three-phase Permanent Magnet Synchronous Motors

Dual three-phase Permanent Magnet Synchronous Motor(DTP-PMSM)is a nonlinear,strongly coupled,high-order multivariable system.In today’s application scenarios,it is difficult for traditional PI controllers to meet the requirements of fast response,high accuracy and good robustness.In order to improve the performance of DTP-PMSM speed regulation system,a control strategy of PI controller based on genetic algorithm is proposed.Firstly,the basic mathematical model of DTP-PMSM is established,and the PI parameters of DTP-PMSM speed regulation system are optimized by genetic algorithm,and the modeling and simulation experiments of DTP-PMSM control system are carried out by MATLAB/SIMULINK.The simulation results show that,compared with the traditional PI control,the proposed algorithm significantly improves the performance of the control system,and the speed output overshoot of the GA-PI speed control system is smaller.The anti-interference ability is stronger,and the torque and double three-phase current output fluctuations are smaller.

Zero-sequence Current Suppressing Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Connected with Single Neutral Point

Dual three-phase permanent-magnet synchronous machines(DTP-PMSM)connected with a single neutral point provide a loop for zero-sequence current(ZSC).This paper proposes a novel space vector pulse width modulation(SVPWM)strategy to suppress the ZSC.Five vectors are selected as basic voltage vectors in one switching period.The fundamental and harmonic planes and the zero-sequence plane are taken into consideration to synthesis the reference voltage vector.To suppress the ZSC,a non-zero zero-sequence voltage(ZSV)is generated to compensate the third harmonic back-EMF.Rather than triangular carrier modulation,the sawtooth carrier modulation strategy is used to generate asymmetric PWM signals.The modulation range is investigated to explore the variation of modulation range caused by considering the zero-sequence plane.With the proposed method,the ZSC can be considerably reduced.The simulated and experimental results are presented to validate the effectiveness of the proposed modulation strategy.

Electromagnetic Performance Prediction for the Symmetrical Dual Three-phase Surface-mounted PMSM under Open-phase Faults Based on Accurate Subdomain Model

The paper presents an accurate analytical subdomain model for predicting the electromagnetic performance in the symmetrical dual three-phase surface-mounted permanent magnet synchronous machine(PMSM)under open-phase faulty conditions.The model derivations are extended from previous accurate subdomain models accounting for slotting effects.Compared with most conventional subdomain models for traditional three-phase machines with nonoverlapping winding arrangement,the subdomain model proposed in this paper applied for the 24-slot/4-pole dual three-phase machine with symmetrical overlapping winding arrangement.In order to investigate the postfault electromagnetic performance,the reconfigured phase currents and then current density distribution in stator slots under different open-circuit conditions are discussed.According to the developed model and postfault current density distribution,the steady-state electromagnetic performance,such as the electromagnetic torque and unbalanced magnetic force,under open-circuit faulty conditions are obtained.For validation purposes,finite element analysis(FEA)is employed to validate the analytical results.The result indicate that the postfault electromagnet performance can be accurately predicted by the proposed subdomain model,which is in good agreement with FEA results.

On the modeling of synchronized flow in cellular automaton models

In this paper, we further analyze our cellular automaton （CA） traffic flow model. By changing some parameters, the characteristics of our model can be significantly varied, ranging from the features of phase transitions to the number of traffic phases. We also review the other CA models based on Kerner＇s three-phase traffic theory. By comparisons, we find that the core concepts for modeling the synchronized flow in these models are similar. Our model can be a good candidate for modeling the synchronized flow, since there is enough flexibility in our framework.

Research on Open-circuit Fault Tolerant Control of Six-phase Permanent Magnet Synchronous Machine Based on Fifth Harmonic Current Injection

This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.

Three-phase AC-DC Converter for Direct-drive PMSG-based Wind Energy Conversion System

In this paper,a wind energy conversion system(WECS)is presented for the electrification of rural areas with wind energy availability.A three-phase AC-DC converter based on a bridgeless Cuk converter is used for power extraction from the permanent magnet synchronous generator(PMSG).The bridgeless topology enables the elimination of the front-end diode bridge rectifier(DBR).Moreover,the converter has fewer components,simple control,and high efficiency,making it suitable for a small-scale WECS.A squirrel cage induction motor(SCIM)is used to emulate a MOD-2 wind turbine to implement the PMSG-based WECS.A direct-drive eight-pole PMSG is used in this study;thus,a low-input-voltage system is designed.The converter is designed to operate in the discontinuous inductor current mode(DICM)for inherent power factor correction(PFC)and the maximum power point tracking(MPPT)is achieved through the tip-speed ratio(TSR)following.The performance of the developed system is analyzed through simulation,and a 500 W hardware prototype is developed and tested in different wind speed conditions.

Small Signal Stability of Three-phase and Six-phase Synchronous Motors:A Comparative Analysis

Small signal stability analysis is conducted for an asymmetrical six-phase synchronous motor in comparison with its equivalent three-phase counterpart.For this purpose,a linearized model of the six-phase synchronous motor is developed using the dq0 approach,which is used in eigenvalue criteria to determine absolute stability in comparison with its equivalent three-phase counterpart.The analysis includes a comparison of the variation in evaluated eigenvalues associated with the stator and rotor sides according to changes in both the three and six-phase machine parameters and working conditions.Key analytical results are experimentally investigated and validated on a test rig.

Global synchronous discontinuous pulse width modulation method with fast calculation capability for distributed three-phase inverters

When multiple distributed converters are integrated, the high frequency harmonics will randomly accumulate at the point of common coupling(PCC). This paper proposes a new fast global synchronous discontinuous pulse width modulation(GSDPWM) method of threephase inverters to effectively attenuate the high frequency current harmonics at PCC. Firstly, the basic principle and the realization method of GSDPWM for three-phase inverters are explained, which can be employed for different modulation types. Then a fast calculation method,which can equally derive the minimized total harmonic distortion(THD) of total current, is proposed to release the calculation burden. Finally, MATLAB simulations and experimental results are presented to verify the performance of GSDPWM.

Current Loop Disturbance Suppression for Dual Three Phase Permanent Magnet Synchronous Generators Based on Modified Linear Active Disturbance Rejection Control

A modified four-dimensional linear active disturbance rejection control(LADRC)strategy is proposed for a dual three-phase permanent magnet synchronous generator(DTP-PMSG)system to reduce cross-coupling between the d and q axis currents in the d-q subspace and harmonic currents in the x-y subspace.In the d-q subspace,the proposed strategy uses a model-based LADRC to enhance the decoupling effect between the d and q axes and the disturbance rejection ability against parameter variation.In the x-y subspace,the 5th and 7th harmonic current suppression abilities are improved by using quasi-resonant units parallel to the extended state observer of the traditional LADRC.The proposed modified LADRC strategy improved both the steady-state performance and dynamic response of the DTP-PMSG system.The experimental results demonstrate that the proposed strategy is both feasible and effective.

Analysis on Circulating Current and Split Capacitor Voltage Balance for Modular Multilevel Converter Based Three-phase Four-wire Split Capacitor DSTATCOM

We propose a modular multilevel converter(MMC)based three-phase four-wire(3P4W)split capacitor distribution static synchronous compensator(DSTATCOM),aiming at compensating unbalanced and reactive load currents.Due to the zero-sequence current compensation,the circulating current char-acteristics of 3P4W MMC-DSTATCOM are different from conventional MMCs.Moreover,the distinct working principle of IMMC would affect the features of split capacitor voltage.The decoupled positive-,negative-and zero-sequence second-order and DC components of the circulating current are deduced explicitly.Two proportional-integral controllers with dual dq transformation are employed to suppress the positive-and negative-sequence components of second-order circulating current,while quasi proportional-resonance controller is designed to eliminate the zero-sequence component.Besides,the phenomenon of the unbalanced split capacitor voltages is revealed,and fast-tracking balancing method by controlling zero-sequence current flowing through the split capacitors is provided.Digital simulation results verify the accuracy of the analysis and the feasibility of the suppression methods.

Model Predictive Torque Control for a Dual Three-phase PMSM Using Modified Dual Virtual Vector Modulation Method

Single voltage vectors applied in the conventional model predictive torque control(MPTC)for multiphase motors do not only suffer from serious torque and stator flux ripples but also cause the large harmonic current.To address the aforementioned challenges,an MPTC using a modified dual virtual vector modulation method is proposed to improve the operational performance of a dual three-phase permanent magnet synchronous motor.Virtual voltage vectors are synthesized as the candidate control set to restrain the harmonic current.A transformation method is introduced to consider both the stator flux and torque in the duty cycle modulation.The torque and stator flux ripples are simultaneously reduced by addressing the limitations of nonuniform units.Furthermore,the null voltage vector is then inserted to expand the modulation range and improve the steady-state performance.Moreover,the sawtooth carrier is adopted to address the challenge of the asymmetric switch sequence caused by the modified modulation.Finally,the experimental results are presented to verify the effectiveness and superiority of the proposed MPTC method.

二级供应链系统的三阶段协同订货模型

生产商-销售商联合生产库存系统是供应链的一个重要组成部分。但是目前协同条件下的相关订货策略具有明显的局限性,容易丢失真正的最优策略。本文利用边际分析法,通过改变销售商相邻两次订货量的大小来分析生产商和销售商库存费用的变化,发现销售商的订货量与系统库存费用变化量的确存在一定的规律。并且,进一步可以推导出该类系统的最优订货策略的订货量必须符合"三阶段"规律。根据该特点,只需设置各个阶段的初始订货量和订货次数等6个决策变量就可以构建订货策略的数学模型。该模型与直接求解的数学模型相比,不仅变量减少,而且其求解也相对简单。最后,利用各个文献中常用的两个实例仿真进行对比分析,验证了该策略确实能够找出其他策略丢失的最优解。