Srirama Srinivas

Multi-level inversion can be obtained from a dual two-level inverter fed open-end winding induction motor (OEWIM) powered from a single dc power supply and a floating capacitor. In this paper, two new model predictive control (MPC) variants are proposed for this drive by simple use of a voltage-based control approach in place of current-based control to reduce the number of computations in the digital controller. With both the proposed MPC variants, the floating capacitor voltage is initialized and is tightly regulated. Improved computational efficiencies are accomplished with both the proposed MPC variants, and superior performance of the drive is obtained with reduced sampling time achievable by exploiting the reduced computational burden. Performance of the entire drive system is demonstrated over a wide motor speed range by extending into field weakening operation also. Besides tight capacitor voltage regulation, the rugged performance of the proposed MPC variants under speed and load changes is demonstrated through simulations and are experimentally validated. Faster execution times owing to a dramatic reduction in computations, compared to some of the existing control methods, superior current and motor torque characteristics of OEWIM are also showcased in support of the proposed MPC variants.

Interior permanent magnet synchronous machines (IPM) employing rare earth magnets are currently used for electric vehicle (EV) application because of their inherent high torque and power density. But high volatility in price and supply of rare earth magnets have forced the automotive in-dustry to search for the alternative electric machine design such as Synchronous Reluctance Motor. This paper compares the performance of Synchronous Reluctance Motor (SynRM) and Ferrite assisted Synchronous Reluctance Motor (Ferrite-SynRM) with Prius2004 IPM for EV application, in terms of electromagnetic performance, weight and material cost. To begin, the sensitivity of some key stator and rotor design variables are performed. Then, with the aid of multi-objective genetic algorithm, optimal geometries of SynRM and Ferrite-SynRM are developed. The predicted results show that the proposed Ferrite-SynRM is suitable for EV application because of its high torque capability, minimum torque ripple, and lower cost.

In this paper, a simplified model predictive current control (MPCC) for a three-level open-end winding induction motor drive mitigating the dead time effects on common-mode voltage (CMV) in the low speed operation of the motor is proposed. The traditional current based objective function is replaced with an equivalent voltage based objective function and an additional term indicating the non zero CMV during dead time is added to achieve complete CMV elimination. Further, a sector-based selection of candidate switching states is employed to reduce the computational burden. It is also shown that the constraint on eliminating the dead time effect on CMV heavily deteriorates the performance of the drive at higher speeds and a smooth transition with and without the constraint is also demonstrated. The envisaged MPCC is simulated in MATLAB and is experimentally verified using TMS320F28377S launchpad. The proposed MPCC gives a massive reduction in the computational burden compared to the conventional MPCC without sacrificing the motor drive performance.

High-gain DC-DC converters are used as impedance matching networks in Photovoltaic (PV) systems to implement Maximum Power Point Tracking (MPPT). The ripple current drawn by the DC-DC converter creates oscillation of the operating point around the Maximum Power Point (MPP) at switching frequency. This deteriorates the power extracted from the PV modules and affects the performance of MPPT algorithms. In a PV system employing a high gain DC-DC converter, the system efficiency and hence power delivered to the load can be increased by tracking the output power instead of tracking the power extracted from the PV module/s. Here, shifting the placement of the current sense resistor from input to the output does the trick. This paper proposes a high-gain energy-efficient DC-DC converter (HGDC) to minimize the ripple current drawn from the PV module/s. The performance of HGDC is studied for different irradiance levels and is compared with similar high-gain converters reported in the literature. The results demonstrate the superior performance of HGDC in terms of reduction in ripple current drawn, reduced power oscillations, and hence operation close to true MPP. Besides, the HGDC has higher energy efficiency, operates close to true MPP with different types of MPPT algorithms, shares common ground between input and outputs minimizing the EMI and safety risks.

This article presents two new energy-saving control methodologies for induction motor (IM)-based electric vehicles (EVs) that exploit advantages from both direct torque control (DTC) and maximum torque per ampere (MTPA) control. While the first variant implements IM control through hysteresis controllers, the second variant employs a modulator to achieve constant switching frequency. For both variants, a flux observer is carefully designed to minimize the effects of IM parameter variations. Detailed torque ripple and power loss characteristics of IM drive controlled with the envisaged MTPA-DTC variants are also presented. The proposed techniques clearly show a reduction in current drawn by the EV system in comparison with the existing techniques. The IM drive is tested for fast acceleration and also the European Union (EU) Urban Drive Cycle to assess the advantages offered by the proposed control techniques. Advantages obtained, such as simple and fast implementation, high dynamic performance, reduced stator current, power loss leading to improved IM efficiency, and reduced steady-state torque ripple followed by energy savings obtained in the EV, are presented in the article, which can greatly benefit EV applications.

The ability of an algorithm to extract power quality parameters on a low-end digital controller with constrained resources and computational capacity can promote comprehensive adoption of power quality control and monitoring infrastructure because of reduced cost and thus improve operational ability in a microgrid or distribution grid and support more in-depth integration of renewable energy. Since conventional harmonic extraction for single-phase grid mostly operate on Fourier transform, lock-in amplifier and their derivative algorithms, they demand large memory and computational power which are available with high-end application-specific processors, digital signal processors (DSPs) and field programmable gate arrays (FPGAs). In this paper, a computationally efficient harmonic extraction algorithm is proposed, which can be implemented on commercially available microcontrollers with ease, without compromising accuracy. A detailed theoretical analysis of the proposed method, along with various simulation and the experimental results are presented. Workarounds for minor implementation issues on digital controllers are discussed as well.

A dual-inverter can synthesize four-level space vector using a single dc power supply and a floating capacitor by utilizing an open-end winding induction motor (OEWIM). In this paper, a cascaded predictive current control (CPCC) method is proposed for this drive that completely avoids weighting factors. Sequential control of multi-objectives by identifying the order of evaluation of individual objectives is introduced. In this paper, motor torque and flux are controlled first followed by voltage balancing of floating capacitor in order to determine the optimal switching combination of the dual-inverter. To improve computational efficiency of the proposed CPCC, a reference voltage vector is used in this paper, in place of current prediction for identifying the candidate switching combination. Ruggedness of the envisaged CPCC is demonstrated through simulations and experimental studies covering speeds below and above motor base speeds of operation. Performance of the proposed CPCC is also compared with the existing MPC methods to showcase torque ripple reduction, improved current THD, reduced inverter switching frequency, improved inverter efficiency etc. Above all, owing to the simplicity of the proposed CPCC, a drastic reduction in the execution times is achieved when compared to the existing MPC methods.

In this paper, three new pulse width modulation (PWM) methods are proposed for a dual-inverter fed Open-End Winding Induction Motor (OEWIM) drive aimed at reducing voltage harmonic distortions in the inverter output. The proposed PWM variants are devised using appropriate voltage injection to the modulating signals. The proffered PWM variants for the dual inverter are analyzed through rigorous harmonic analysis to arrive at complete harmonic description using Double Fourier Integral Approach (DFIA) to obtain their characteristics. For all the PWM variants, optimal values of voltage injection are also obtained that yield lower voltage harmonics at the output of the dual inverter. The analytical solutions thus obtained are verified through simulations and experimental results and the improved harmonic performance compared to the existing PWM techniques are also presented. Identifying the shortcoming of reduced limits of linear modulation of the proposed PWM techniques, a solution to smoothly slide-over to the Phase Disposed-PWM techniques is also demonstrated. Besides, the impact of the proposed PWM variants on improved motor current ripple and torque ripple performance when used with field-oriented control is presented and compared with some existing PWM methods to showcase their superior performance characteristics and also the usefulness of the envisaged PWM methods.

In this paper, two Constant Switching Frequency Direct Torque Control (CSF-DTC) techniques are proposed for H-Bridge Three-Level inverter (HB-TLI) fed Induction Motor (IM) for reducing torque ripple at low speed operation. Both the methods use modulators and characteristics of the Pulse Width Modulation (PWM) mainly determine the motor drive performance. The first method uses two level-shifted carriers signals whereas, the second method uses carrier signals with appropriate offset-voltages. Detailed analytical expressions describing complete harmonic characteristics of HB-TLI are also presented using double Fourier integral approach. Superior harmonic performance is obtained with the proposed PWM methods compared to the existing ones. Drawback of one of the envisaged CSF-DTC techniques entering into over-modulation is rectified at higher motor speeds and a smooth slide-over using zero offset voltage to carrier signals is recommended to overcome the issue. The proposed CSF-DTC techniques are simulated and experimentally validated. The dynamic and steady-state torque performance obtained with the proposed CSF-DTC techniques for IM are compared with the existing DTC methods which show a significant reduction in the steady-state torque and current ripple whereas the torque dynamic performance is almost preserved thus, demonstrating its usefulness especially at lower motor speeds.