Sanjeevikumar Padmanaban

Optimized carrier based multilevel generated modified dual three-phase open-winding inverter for medium power application

This paper presents a novel carrier based multilevel modulation for modified dual three-phase open-winding inverter applicable for low-voltage/high-current applications. A standard three-phase voltage source inverter (VSI) is connected across the open-winding of both ends of the motor. Each VSI incorporates an additional bi-directional switching device (MOSFET/IGBT) per phase and all three legs link to the neutral of two capacitors in the power circuit. An original optimal double carrier zero-shifted five-level modulation (DCZ SFM) algorithm is also presented and is used to modulate each VSI in a similar way to a 5-level multilevel inverter. The complete model based system is simulated in Matlab/PLECS softwares and set of results are presented which shows good conformity with the theoretical analysis.

Novel Wavelet-Fuzzy Based Indirect Field Oriented Control of Induction Motor Drives

This paper presents a wavelet-fuzzy based controller for indirect field oriented control of three-phase induction motor drives. The discrete wavelet transform is used to decompose the error between the actual speed and the command speed of the induction motor drive into different frequency components. The transformed error coefficients along with the scaling gains are used for generating the control component of the motor. Self-tuning fuzzy logic is used for online tuning of the scaling gains of the controller. The proposed controller has the ability to meet the speed tracking requirements in the closed loop system. The complete indirect field oriented control scheme incorporating the proposed wavelet-fuzzy based controller is investigated theoretically and simulated under various dynamic operating conditions. The simulation results are compared with a conventional proportional integral controller and a fuzzy based controller. The speed control scheme incorporating the proposed controller is implemented in real time using a digital processor control board. Simulation and experimental results validate the effectiveness of the proposed controller.

A Comprehensive Analysis and Hardware Implementation of Control Strategies for High Output Voltage DC-DC Boost Power Converter

Classical DC-DC converters used in high voltage direct current (HVDC) power transmission systems, lack in terms of efficiency, reduced transfer gain and increased cost with sensor (voltage/current) numbers. Besides, the internal self-parasitic behavior of the power components reduces the output voltage and efficiency of classical HV converters. This paper deals with extra high-voltage (EHV) dc-dc boost converter by the application of voltage-lift technique to overcome the aforementioned deficiencies. The control strategy is based on classical proportional-integral (P-I) and fuzzy logic closed-loop controller to get high and stable output voltage. Complete hardware prototype of EHV is implemented and experimental tasks are carried out with digital signal processor (DSP) TMS320F2812. The control algorithms P-I, fuzzy logic and the pulse-width modulation (PWM) signals for N-channel MOSFET device are performed by the DSP. The experimental results provided show good conformity with developed hypothetical predictions. Additionally, the presented study confirms that the fuzzy logic controller provides better performance than classical P-I controller under different perturbation conditions.

Five-phase five-level open-winding/star-winding inverter drive for low-voltage/high-current applications

This paper work proposed a five-phase five-level open-/star-winding multilevel AC converter suitable for low-voltage/high-current applications. Modular converter consists of classical two-level five-phase voltage source inverter (VSI) with slight reconfiguration to serve as a multilevel converter for open-/star-winding loads. Elaborately, per phase of the VSI is built with one additional bi-directional switch (MOSFET/IGBT) and all five legs links to the neutral through two capacitors. The structure allows multilevel generation to five-level output with greater potential for fault tolerability under drive failure (open-winding) and per phase fault (open-/star-winding). Further, original optimal single carrier zero-shifted modulation (SCZSFM) algorithm is proposed and capable to modulate each VSI, which is equivalent to standard 5-level multilevel inverters. Set of results are provided based on numerical modeling with MATLAB/PLECS simulation softwares and observed behavior shown good agreement with theoretical expectations.

High-Voltage DC-DC Converter Topology for PV Energy Utilization - Investigation and Implementation

Abstract This paper exploited the utilization of photovoltaic (PV) energy system with high-voltage (HV) output DC-DC converter. Classical boost converters are used for both renewable energy integration and HV applications, but limited by reducing output/efficiency in performance. Moreover, as parasitic elements suppress the power transfer ratio, converter needs to maximize the PV energy utilization. This investigation study focused to include additional parasitic elements (voltage-lift technique) to a standard DC-DC buck converter and to overcome all the above drawbacks to maximize the PV power generation. The proposed power circuitry substantially improves the output power gain transfer ratio and a prototype hardware module is implemented using industrial standard DSP TMS 320F2812. Numerical simulation development followed by an experimental prototype implementation is carried out in this investigation. A set of numerical and experimental results is provided in this paper, which show close conformity with the theoretical background.

Design and Real-Time Simulation of an AC Voltage Regulator Based Battery Charger for Large-Scale PV-Grid Energy Storage Systems

In a conventional energy storage system in a grid-connected solar power stations, solar power is transferred to the grid through a PV-Inverter, and the battery is charged and discharged through a bi-directional converter. In this paper, a novel grid energy storage system for large-scale PV systems is discussed. With the proposed configuration, the battery charging and discharging are carried out through an AC voltage regulator which is connected in series to the line. For this system, cascaded H-bridge (CHB)-based PV-Inverter which is suitable for a high power application is selected. In case of failure in one H-Bridge of a CHB inverter, it is difficult to integrate solar inverter with the grid as the voltages of inverter and grid are not matched. Fault tolerant operation of the CHB-based PV-Inverter can also be achieved through the proposed configuration. In this paper, basic operation and control of a voltage regulator, application of the voltage regulator in grid energy storage systems, fault tolerant operation of a CHB inverter through the voltage regulator are presented. To validate the performance of the controls proposed, Real-time simulations are carried out by interfacing the simulated power circuit with the real controller card with the help of an Opal-RT make real-time simulator. Performance of the proposed system is analyzed through presented results.

Single-phase seven-level stack multicell converter using level shifting SPWM technique

This paper presents a single-phase seven-level stack multicell converter (SMC) which provides a viable solution for multilevel converter. Conventional cascaded multilevel inverter (MLI) removes the drawbacks of clamping diodes and clamping capacitors topologies. However, in a cascaded MLI number of voltage source and power switches increases as the number of level increases. The main advantage of single-phase SMC converter is only two DC sources are needed for any number of levels. Level shifting SPWM technique has been incorporated to achieve gate pulses, in which carrier wave of 20kHz is compared with 50Hz sinusoidal reference wave at a modulation index of 1 and 0.9. Total harmonic distortion (THD) for SMC converter is achieved at 1.55% and 5.26% with and without filter respectively. The seven-level SMC topology is simulated in MATLAB/SIMULINK and simulation results are provided to verify the performance.

Improved Fault Ride Through Capability in DFIG Based Wind Turbines Using Dynamic Voltage Restorer With Combined Feed-Forward and Feed-Back Control

This paper investigates the fault ride through (FRT) capability improvement of a doubly fed induction generator (DFIG)-based wind turbine using a dynamic voltage restorer (DVR). Series compensation of terminal voltage during fault conditions using DVR is carried out by injecting voltage at the point of common coupling to the grid voltage to maintain constant DFIG stator voltage. However, the control of the DVR is crucial in order to improve the FRT capability in the DFIG-based wind turbines. The combined feed-forward and feedback (CFFFB)-based voltage control of the DVR verifies good transient and steady-state responses. The improvement in performance of the DVR using CFFFB control compared with the conventional feed-forward control is observed in terms of voltage sag mitigation capability, active and reactive power support without tripping, dc-link voltage balancing, and fault current control. The advantage of utilizing this combined control is verified through MATLAB/Simulink-based simulation results using a 1.5-MW grid connected DFIG-based wind turbine. The results show good transient and steady-state response and good reactive power support during both balanced and unbalanced fault conditions.

Coordinated DTC and VOC control for PMSG based grid connected wind energy conversion system

This paper presents an output power smoothing method by a coordinate control of machine side converter and grid side converter for permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS). The WECS adopts medium voltage source converter with AC-DC-AC configuration. The output power fluctuations are compensated using direct torque control based maximum power point controller and voltage oriented control. The DC link voltage is controlled using grid side controller and the maximum power is extracted using the machine side controller of the wind turbine. The proposed controller provides effective solution for grid integration and constant power flow from the generator system to grid system. Simulation results are presented and analysed the performance of the control strategies implemented in the system.

Disturbance-observer based control of voltage-source-converter under unbalanced voltage conditions

Purpose This paper aims to propose a novel grid current control strategy for grid-connected voltage source converters (VSCs) under unbalanced grid voltage conditions. Design/methodology/approach A grid voltage dynamic model is represented in symmetrical positive and negative sequence reference frames. A proportional controller structure with a first-order low-pass filter disturbance observer (DOB) is designed for power control in unbalanced voltage conditions. This controller is capable of meeting the positive sequence power requirements, and it also eliminates negative sequence power components which cause double-frequency oscillations on power. The symmetrical components are calculated by using the second-order generalized integrator-based observer, which accurately estimates the symmetrical components. Findings Proportional current controllers are sufficient in this study in a wide range of operating conditions, as DOB accurately estimates and feed-forwards nonlinear terms which may be deteriorated by physical and operating conditions. This is the first reported scheme which estimates the VSC disturbances in terms of symmetrical component decomposition and the DOB concept. Originality/value The proposed method does not require any grid parameter to be known, as it estimates nonlinear terms with a first-order low-pass filter DOB. The proposed control system is implemented on a dSPACE ds1103 digital controller by using a three-phase, three-wire VSC.