Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Analysis of Direct Torque Control using Space Vector Modulation for Three Phase Induction Motor

This paper presents the results of an investigation into the suitability of a Direct Torque Control of three phase Induction motor. It is considered as an alternative to the field oriented control (FOC) or vector control technique. They aim to control effectively the torque and flux. Direct Torque Control (DTC) uses an induction motor model to predict the voltage required to achieve a desired output torque. By using only current and voltage measurements, it is possible to estimate the instantaneous stator flux and output torque. An induction motor model is then used to predict the voltage required to drive the flux and torque to the demanded values within a fixed time period. This calculated voltage is then synthesized using Space Vector Modulation (SVM). Torque control of an induction machine based on DTC strategy has been developed and a comprehensive study is described. The performance of this control method has been demonstrated by simulations performed using a versatile simulation package, Matlab

Magnetic noise reduction of in-wheel permanent magnet synchronous motors for light-duty electric vehicles

This paper presents study of a multi-slice subdomain model (MS-SDM) for persistent low-frequency sound, in a wheel hub-mounted permanent magnet synchronous motor (WHM-PMSM) with a fractional-slot non-overlapping concentrated winding for a light-duty, fully electric vehicle applications. While this type of winding provides numerous potential benefits, it has also the largest magnetomotive force (MMF) distortion factor, which leads to the electro-vibro-acoustics production, unless additional machine design considerations are carried out. To minimize the magnetic noise level radiated by the PMSM, a skewing technique is targeted with consideration of the natural frequencies under a variable-speed-range analysis. To ensure the impact of the minimization technique used, magnetic force harmonics, along with acoustic sonograms, is computed by MS-SDM and verified by 3D finite element analysis. On the basis of the studied models, we derived and experimentally verified the optimized model with 5 dBA reduction in A-weighted sound power level by due to the choice of skew angle. In addition, we investigated whether or not the skewing slice number can be of importance on the vibro-acoustic objectives in the studied WHM-PMSM.Postprint (published version

Hysteresis band current controller based field-oriented control for an induction motor driven by a direct matrix converter

© 2017 IEEE. This paper presents work on the hysteresis band control for output current regulation in a direct matrix converter in order to drive an induction motor. The hysteresis band controller offers excellent dynamic performance. It has been extensively researched for the voltage source inverter and inverter based drive systems, but it has not been investigated within the context of a matrix converter or a matrix converter based motor drive. Firstly, this paper proposes a fixed-band hysteresis current controller for a matrix converter to track the prescribed current references, and then a sinusoidal-band hysteresis current controller is proposed. Both methods have fast dynamic performance and they inherently integrate the line modulation technique of the virtual rectifier stage into the overall modulation. The extra modulation stage is not required and the surge current is inherently prevented. The sinusoidal-band hysteresis controller demonstrates that it generates lower harmonic content at the expense of the higher average switching frequency. Following this, both methods are tested as a drive for an induction motor with field-oriented control. With the matrix-converter-based drive system, one significant benefit is that the braking chopper is removed due to the bidirectional feature. The methods are simple and have light computation burden. The obtained results demonstrate the effectiveness and feasibility of the proposed scheme. The experimental work is being carried out to support the proposed scheme

Nonlinear Compensation Empyoing Matrix Converter with DTC Controller

This paper describes a nonlinear harmful speed and torque controller for fourth order induction motor model. The investigation of optimality and cost function for that base on estimation of Hammerstein-Wiener model with the compensated mathematical model. The matrix converter with direct torque control combination is efficient way to get better performance specifications in the industry.The MC and the DTC advantages are combined together.The reduction of complexity and cost of DC link in the DTC since it has no capacitors in the circuit. However, the controlling torque is a big problem it in DTC because of high ripple torque production which results in vibrations response in the operation of the IM as it has no PID to control the torque directly. The combination of MC with DTC is applied to reduce the fluctuation in the output torque and minimize the steady state error. This paper presents the simulation analysis of induction machine drives using Maltlab/Simulink toolbox R2012a. Design of constant switching frequency MCDTC drive,stability investigation and fault protection as well as controllability and observability with minimum steady state error has been carried out which  proved the effectiveness of the proposed technique

An enhanced control strategy based imaginary swapping instant for induction motor drives

The main aim of this paper is to present a novel control approach of an induction machine (IM) using an improved space vector modulation based direct torque control (SVM-DTC) on the basis of imaginary swapping instant technique. The improved control strategy is presented to surmount the drawbacks of the classical direct torque control (DTC) and to enhance the dynamic performance of the induction motor. This method requires neither angle identification nor sector determination; the imaginary swapping instant vector is used to fix the effective period in which the power is transferred to the IM. Both the classical DTC method and the suggested adaptive DTC techniques have been carried out in MATLAB/SimulinkTM. Simulation results shows the effectiveness of the enhanced control strategy and demonstrate that torque and flux ripples are massively diminished compared to the conventional DTC (CDTC) which gives a better performance. Finally, the system will also be tested for its robustness against variations in the IM parameters

Performance Analysis of Induction Motor Using PI And FUZZY Controller

This paper represents the better speed regulation of induction motor by the help of indirect vector control technique and also by using other controlling techniques. Here speed of induction motor is regulated or controlled by using PI controller and fuzzy logic controller, by using PI controller it provides good regulation of speed but due to some drawback in it like high overshoot, oscillation of speed and torque at variation or change in load or due to external disturbances occur during running performance of induction motor drive that controller is replaced by fuzzy logic controller which provides more better running performance to the induction motor by regulating its speed in better way and tracking the actual running speed response easily and fast as compare to PI controller. The benefits of squirrel-cage induction motors are high robustness and low maintenance which make it widely used through various industrial modem processes, with growing economical and demands. In conventional FOC, PI controller is used to control the speed response of the induction motor drive. The use of PI controller induces many problems due to sudden changes in load and external disturbances. This behavior of the controller causes disturbance in drive running performance. To overcome this disadvantages an intelligent controller based on fuzzy logic is employed in the place of the conventional PI controller. DOI: 10.17762/ijritcc2321-8169.15061

Enhanced Performance of DTC-DSC of Induction Machine utilizing 3-Level Cascade H-Bridge Multilevel Inverter

The paper presents a new 3L DTC-DSC scheme for induction motor driver by selecting proper voltage vector for medium and high application. In conventional 3L DTC two different voltage vectors are assigned to vary flux for low speed, medium speed and high speed applications. This paper purposes a scheme for low speed operation of induction machines by using the same technique as conventional 3L DTC. However for a high speed operation, only a single voltage vector is applied thus resulting dodecagon flux locus.The new scheme also improves the torque capabalities and the dynamic of torque performances