Dinkar Prasad

A Modified Feedback Scheme Suitable for Repetitive Control of Inverter With Nonlinear Load

It is mandatory to keep the total harmonic distortion in the output of most inverters below the limits prescribed by different international standards. The harmonic distortions caused due to nonlinear loads may not get corrected by typical magnitude controller, like PID controller. Repetitive controller is more effective in such situations. Often, repetitive controller is used as add-on block to the conventional magnitude controller. Design of repetitive controller can be easily implemented on digital platform. Rapid change in phase and magnitude of inverter-filters transfer function near corner frequency causes instability problems in repetitive controller. Various techniques have been proposed by researchers to overcome this problem. Most of the reported techniques rely on digital compensation. However, it is hard to find a digital compensator, which simultaneously meets the phase and gain requirements at moderate computational effort. Here, a new output voltage feedback scheme has been proposed, which simplifies the requirement of digital compensation. The proposed scheme requires an extra hardware but at negligible added cost. In spite of this extra hardware, the proposed circuit turns out to be more energy efficient in comparison to few popular schemes, reported in literature, where some resistance is introduced in the inverters filter for better stability of controller. In addition to the proposed modification the paper presents a simplified explanation of the various factors affecting stability of repetitive controller. The paper also discusses a novel experimental method for verifying the efficacy of repetitive controller in suppressing distortion of any particular harmonic order.

Investigations and experimental study on Magnetic Resonant coupling based Wireless Power Transfer system for neighborhood EV's

Advancement in technology enhances the need for quick and efficient ways of charging electric devices. Increased need for portability has motivated us to make use of Wireless Power Transfer technology (WPT). In this paper, Magnetic Resonant Technique (MRT) based WPT system has been used to transfer the power wirelessly over larger airgaps. The conventional electric vehicles uses a battery as the main source and it suffers from large 1charging time and also it requires huge amount of space for the charging station. This paper illustrates various methods to implement WPT-MRT and supercapacitor based two-wheeler type electric vehicle (EV) to diminish the charging issues in the system. In this paper, 3-phase Permanent Magnet Brushless DC Motor (PMBLDC) is also used as a traction motor since it is energy efficient, has high torque per volume and greater ease of control compared to other motors. A TI controller is used as a central control unit to monitor the control variables of the system. This paper presents experimental interpretations of various compensation topologies and proves the supreme topology to achieve highest coupling coefficient to make maximum power transfer possible in the system. In this paper, the investigations and experimental study are further extended to provide a durable solution to facilitate fast / frequent charging for short commuting electric vehicles of the future.

Comprehensive mathematical modelling and experimental analysis of a wireless power transfer system for neighborhood electric vehicles

Research on developing the applications of Wireless Power Transfer System (WPTS) has increased considerably during last few years. Due to functional and environmental benefits, charging of electric vehicles via WPTS has been contemplated in academic and industrial research. The WPTS based on Magnetic Resonant Coupling Technique (MRCT) is considered as an efficient way for contactless power transfer over medium distances (up to about 20 to 30 centimeters). This paper presents a comprehensive MATLAB/SIMULINK based model for such a system. The parameters of the model are derived from mathematical equations presented in the paper. The performance of the model is also verified experimentally. Performance parameters, like power transfer efficiency and loss factor have been shown.

Effect of coil geometry and shielding on wireless power transfer system

Magnetic resonance coupling (MRC) based wireless power transfer (WPT) system is recognized as an efficient and promising technology for safe, convenient and elegant charging solution for various electronic portable devices. MRC technology helps in transferring power wirelessly from transmitter to receiver over larger distances. However in such loosely coupled systems, low power transfer efficiency is the major issue in comparison to conventional wired charging systems. The paper presents detailed analysis of power transfer efficiency between two independent coils separated by distance of 15 cm. The analysis involves an effect of coil geometrical dimensions on power transfer efficiency and mutual inductance between transmitter (TX) and receiver coils (RX). In addition, the investigations are further extended to analyze the role of shielding and effect of shielding geometry on power transfer efficiency and mutual inductance between the two coils.

A comparative analysis on WPT system using various power transfer methodologies and core configurations

Recent days, the demand for wireless power transfer (WPT) system is highly growing since it is more convenient, reliable and safer solution for electric vehicle (EV) consumers. Static and dynamic power transfer systems are the two opted appreciable wireless charging techniques for user friendly EVs. In static and dynamic charging systems, low power transfer efficiency (ηp) between transmitter and receiver coils is the principle challenge in existing issues of wireless charging system. The paper mainly focuses on improvement of power transfer efficiency in the system. The analyses presented in this paper are tested for distinct face to face distances of the coils to observe the effect of reluctance on power transfer efficiency. Here two kinds of coil structures have been adopted and are tested with various core configurations to find the suitable combination for the enhancement of power transfer efficiency. The paper presents a comparative analysis on performance characteristics of WPT system using inductive coupled and magnetic resonance coupled (MRC) power transfer techniques. In MRC system, various compensation topologies are used to find the efficient topology which enhances the better impedance matching in the system. Further, the analysis on effect of aluminum shielding is alsoreported.

Design and implementation of a variable frequency drive for single-phase induction motor

Variable frequency drive of single-phase induction motor can have many potential advantages, like reduced inrush current during starting, high starting torque, possibility of higher efficiency, more tolerant to variation in grid supply voltage etc. Many of the existing electrical gadgets use single-phase induction motor of capacitor start / capacitor-run type. A typical example is the motor used in household refrigerators. In this application the starting torque requirement is high. It will be good if the motor starts with reduced inrush current and if the amount of cooling by refrigerator is controlled by variable speed operation of the motor. This work proposes a power electronic circuit which can be incorporated with some change in the existing wiring circuit of the refrigerator.

Extensive analysis on wireless power transformer for various core configurations

Wireless power transfer (WPT) is one of the safe and convenient way of transmitting power for short range distances. But its efficiency is lower than wired power transfer due to low coupling coefficient and improper coupling between transmitter and receiver. In the field of inductively coupled wireless power transfer, identifying and enabling of appropriate reluctance path between the transmitter and receiver is a significant element. This can be achieved by selecting proper dimensions as well as the suitable category of the core. This paper demonstrates design aspects and the effects of core dimensions on the coupling factor and illustrates the different core combinations. It also provides numerical analysis of various factors such as leakage flux, mutual flux and coupling factor and the similar attributes for various WPT models. In this work, various core combinations have been analyzed to find an efficient combination to achieve highest coupling coefficient to facilitate maximum power transfer in the system. The WPT system is further analyzed under no-load as well as load conditions for various distances between transmitter and receiver.

Application of repetitive control for removal of harmonic distortions from inverter output

It is mandatory to keep total harmonic distortion in output of most inverters below a prescribed limit. The harmonic distortions caused due to non-linear loads may not get corrected by simple PID controllers. Repetitive controllers are more effective in such situations. Often repetitive controllers are used as add-on block to the conventional PID controller. Design of repetitive controller can be easily implemented on digital platform. Some controller parameters may have to be decided on trial and error basis.