Finite Control Set Model Predictive Current Control of a Five-Phase PMSM with Virtual Voltage Vectors and Adaptive Control Set

This paper presents an improved finite control set model predictive current control(FCS-MPCC)of a five-phase permanent magnet synchronous motor(PMSM).First,to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set,virtual voltage vectors are adopted.As the third current harmonics can be much reduced by virtual voltage vectors automatically,the harmonic items in the cost function of conventional FCS-MPCC are not considered.Furthermore,an adaptive control set is proposed based on voltage prediction.Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method.Consequently,current ripples can be largely reduced and the system performs much better.At last,simulations are established to verify the steady and transient performance of the proposed FCS-MPCC,and experiments based on a 2 kW five-phase motor are carried out.The results have validated the performance improvement of the proposed control strategy.

Effect of Center Voltage Vectors(CVVs)of Three-level Space Plane on the Performance of Dual Inverter Fed Open End Winding Induction Motor Drive

Dual inverter fed open end winding induction motor(IM)drive offers many advantages over other multilevel inverter fed IM drives.Pulse width modulation(PWM)techniques are employed for the control of output voltage and frequency.Space vector base PWM techniques are popular among all the PWM techniques.A simplified space vector PWM method with simple and small look-up table approach is presented for dual inverter configuration.Moreover the proposed space vector based PWM technique provides freedom in selecting the center voltage vector(CVV)by which different PWM techniques will be derived.The implementation of all these PWM techniques is generalized by using a constant ao.The derived PWM techniques show superior performance in reducing the zero sequence voltage(ZSV)by maintaining the same quality of output voltage.The performance of all these PWM techniques are evaluated theoretically and verified in real time through dSPACE 1104 control board.

A Novel Fuzzy Direct Torque Control System for Three-level Inverter-fed Induction Machine

Diode clamped multi-level inverter （DCMLI） has a wide application prospect in high-voltage and adjustable speed drive systems due to its low stress on switching devices, low harmonic output, and simple structure. However, the problem of complexity of selecting vectors and capacitor voltage unbalance needs to be solved when the algorithm of direct torque control （DTC） is implemented on DCMLI. In this paper, a fuzzy DTC system of an induction machine fed by a three-level neutral-point-clamped （NPC） inverter is proposed. After introducing fuzzy logic, optimal selecting switching state is realized by applying various strategies which can distinguish the grade of the errors of stator flux linkage, torque, the neutral-point potential, and the position of stator flux linkage. Consequently, the neutral-point potential unbalance, the dr/dr of output voltage and the switching loss are restrained effectively, and desirable dynamic and steady-state performances of induction machines can be obtained for the DTC scheme. A design method of the fuzzy controller is introduced in detail, and the relevant simulation and experimental results have verified the feasibility of the proposed control algorithm.

Robust Dichotomy Solution-Based Model Predictive Control for the Grid-Connected Inverters with Disturbance Observer

This paper proposes a robust dichotomy-based model predictive control(DS-MPC)with a fixed switching frequency for the grid-connected inverter(GCI).The proposed fast dichotomy algorithm can select and deduce the optimal voltage vector dynamically through the space vector plane.Therefore,the proposed DS-MPC strategy could ensure dynamic performance and steady-state performance as well.Also,the current control robustness can be improved through DS-MPC with disturbance observer(DO)based on the extended Kalman filter(EKF).The novelty of this control is that the current control with fast dynamic response can be realized in the weak grid,even if the grid voltages are greatly distorted.Simulation and hardware experiments on the weak grid validate the effectiveness of the proposed DS-MPC with the EKF observer approach.

Locus of Flux Linkage for Three-Phase ZVS Inverter

ZVS（zero voltage switching） PWM（pulse width modulation） inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every carrier period so that each power device can commutate when voltage of the main circuit＇s DC bus line is zero. To ensure the resonant circuit to operate properly, sawtooth with alternate slope （positive or negative） is used as carrier. But the time of zero voltage vectors with such PWM pattern is greatly different from traditional hard-switching PWM pattern. This paper discusses the locus of flux linkage under soft-switching PWM pattern by using space voltage vector. It is pointed out that, under the hard-switching PWM pattern, speed of flux linkage is adjusted by zero space voltage vector. When soft-switching PWM pattern is used, however, effective time of space voltage vector varies considerably, sometimes even without zero space voltage vector. Therefore non-zero space voltage vector has been used to make the speed of flux linkage locus equal to that of hard-switching PWM pattern. The cause of current distortion in soft-switching PWM inverters is also discussed. Based on the flux linkage locus circle, corresponding compensation methods are proposed. Experimental results show that the described method can effectively improve output current waveform of inverter.

A neutral point potential drift control method for NPC three-level inverter

The output current harmonic distortion of a three-level inverter is less than the traditional twolevel inverter.The voltage stress of the semiconductor switch is low.A neutral point potential drift control method is proposed to solve the problem of the neutral point potential drift of the three-level inverter.The interaction mechanism between the neutral point potential and the space voltage vector is presented.The small vector output by the inverter is found to be the root cause of the midpoint potential drift.It is found that the fluctuation of the midpoint potential could be suppressed by increasing the capacitance value of the inverter bus voltage stabilizing capacitor.Furthermore,it inhibits the fluctuation of the midpoint potential.The experimental results verify the efficiency and precision of the proposed method.

Costless-Function Model Predictive Current Control of Seven-Phase PMSM to Improve Dynamic Performance and Suppress Harmonics of Marine Electric Propulsion System

In order to improve the dynamic performance and suppress current harmonic for seven-phase PMSM(permanent magnet synchronous motor),this paper proposed an MPCC(mode predict current control)scheme based on SVPWM(space vector pulse width modulation)technique.By this scheme,the 14 virtual voltage vectors are first calculated based on the principle:the voltage vector synthesized in the 3rd harmonic subspace and the 5th harmonic subspace should be zero,in each sampling period,the optimal voltage vector is directly selected from the 14 virtual voltage vectors to achieve the best output current performance of seven-phase PMSM.In addition,no cost function related calculations are required in the MPCC scheme,reducing the calculation time and improving the dynamic response of the system.The simulation model of the seven-phase PMSM vector control system is established by using the Simulink tool of MATLAB,and the effectiveness of the scheme will be presented.

Research and Design of DTC System Based on Six-phase Asymmetrical BLDCM

In this paper,the torque ripple problem of six-phase asymmetrical brushless DC motor(BLDCM)is studied.First,the basic structure of BLDCM is introduced,and the operation principle of six-phase asymmetrical BLDCM that is studied in the thesis is expounded.Then,the principle of direct torque control(DTC)system of BLDCM is also discussed,and the improved system is proposed,including using the torque hysteresis loop and opening current hysteresis loop,and choosing the improved voltage vector to make the PWM-ON-PWM modulation.Finally,the DTC system simulation model is built,and the system is also tested by the experiment.According to the results of experiment and simulation,the DTC system designed in this thesis can control the six-phase asymmetrical BLDCM stably and reliably,and the problem of high frequency and torque ripple is solved well.

A weighted voltage model predictive control method for a virtual synchronous generator with enhanced parameter robustness

To address the problem of insufficient system inertia and improve the power quality of grid-connected inverters,and to enhance the stability of the power system,a method to control a virtual synchronous generator(VSG)output voltage based on model predictive control(MPC)is proposed.Parameters of the inductors,capacitors and other components of the VSG can vary as the temperature and current changes.Consequently the VSG output voltage and power control accuracy using the conventional MPC method may be reduced.In this paper,to improve the parameter robustness of the MPC method,a new weighted predictive capacitor voltage control method is proposed.Through detailed theoretical analysis,the principle of the proposed method to reduce the influence of parameter errors on voltage tracking accuracy is analyzed.Finally,the effectiveness and feasibility of the proposed method are verified by experimental tests using the Typhoon control hardware-in-the-loop experimental platform.

Improved Optimal Duty Model Predictive Current Control Strategy for PMSM

To further improve the steady-state performance of the conventional dual vector model predictive current control(MPCC),an improved optimal duty MPCC strategy for permanent magnet synchronous motor(PMSM)is proposed.This strategy is realized by selecting an optimal voltage vector combination and its duration from the five basic voltage vector combinations,followed by acting on the inverter.The five combinations are:the combination of the optimal voltage vector at the previous moment and basic voltage vector with an angle difference of 60°;the combination of the optimal voltage vector at the previous moment and basic voltage vector with an angle difference of-60°;the combination of the aforementioned three basic voltage vectors with the zero vector.Experimental results indicate that the method effectively reduces the stator current ripple without increasing the calculational burden.Furthermore,it improves the steady-state performance of the system without altering the dynamic performance of the system.