Paulson Samuel

Grid Interface of Wind Power With Large Split-Winding Alternator Using Cascaded Multilevel Inverter

In this paper, a wind energy conversion system based on a cascaded H-bridge multilevel inverter (CHBMLI) topology has been proposed to be used for the grid interface of large split-winding alternators (SWAs). A new method has been suggested for the generation of reference currents for the voltage source inverter (VSI) depending upon the available wind power. The CHBMLI has been used as a VSI and operated in a current control mode in order to achieve the objectives of real power injection and load compensation (power factor correction, load balancing, and harmonic compensation) based on the proposed reference-generation scheme. The field excitation control of SWA provides a single means to vary the dc-link voltages of all the CHBs simultaneously and proportionately. The equal distribution of switching stress and power losses among H-bridge cells, reduction in their power ratings, and high quality of inverter output makes the proposed arrangement more efficient. The closed-loop performance of the VSI has been shown to be adequate and fully achieves the control objectives, i.e., grid interface of distributed energy resource (wind) in addition to load compensation. The simulation studies on the proposed scheme have been obtained through the PSCAD/EMTDC software.

Load Frequency Control with Communication Topology Changes in Smart Grid

In this paper, the quality of service of communication infrastructure implemented in multiarea power system for load frequency control application is assessed in smart grid environment. In this study, network induced effects time delay, packet loss, bandwidth, quantization, and change in communication topology (CT) has been addressed to examine the system performance in closed loop. Uncertainty in time delay is approximated using deterministic and stochastic models. The network is modeled considering different network configurations, i.e., change in CT. The modeled communication network guarantees control relevant properties, i.e., stability. The decentralized controller and linear matrix inequality-based linear quadratic regulator is implemented to reduce the dynamic performance (mean square error of states variables) of power system as CT changes. Simulation results suggest that the proposed scheme of networked control is superior with respect to other design methods available in the literature, and thus robust to communication imperfections.

Wind energy conversion based on seven-level cascaded H-bridge inverter using LabVIEW FPGA

In this paper, an isolated wind energy conversion system (WECS) based on the cascaded H-bridge multilevel inverter (CHBMLI) topology employing a permanent magnet synchronous generator (PMSG) driven by a variable speed wind turbine and feeding high power single-phase local loads has been proposed. A seven-level cascaded H-bridge inverter employing phase-shifted multi-carrier pulse width modulation is implemented using LabVIEW FPGA. The output of the synchronous generator with fixed excitation, emulating a PMSG is connected to a three phase diode bridge rectifier. The DC output of the rectifier is then connected to the proposed topology of three H-bridges using IGBT based intelligent power modules (IPM) thus forming a single phase CHBMLI in the laboratory to obtain the experimental results. The switching pulses for the IPM are generated with phase shifted multi carrier PWM using NI LABVIEW with the help of PCI 7831R FPGA data acquisition board that in turn generates a seven-level output voltage across a single-phase load.

Solar array system simulation using FPGA with hardware co-simulation

In this paper an attempt has been made to realize the solar photovoltaic (PV) characteristics and its control through solar array simulation system designed using field programmable gate array (FPGA) with hardware co-simulation. This facilitates the virtual test bench to test the I-V and P-V characteristics of the solar PV module and performance of the maximum power point tracking (MPPT) algorithm. The test system consists of boost DC-DC power converter, which is controlled by Xilinx/FPGA based control unit to demonstrate the perturb and observe (P&O) MPPT algorithm employed for the solar PV module. The results of the simulated solar PV module are verified with the practical solar PV module characteristics. The results of the MPPT verify the performance of the proposed solar array simulation system. The real time simulation study is carried with Xilinx System Generator (XSG) and Matlab/Simulink simulation environment.

Communication time delay estimation for load frequency control in two-area power system

Due to increased size and complexity of power system network, the stability and load frequency control (LFC) is of serious concern in a wide area monitoring system (WAMS) having obtained signals from phasor measurement unit (PMU). The quality of services (QoS) for communication infrastructure in terms of signal delay, packet loss probability, queue length, throughput is very important and must be considered carefully in the WAMS based thermal power system. However, very few studies have been presented that includes QoS for communication infrastructure in load frequency control (LFC) of power system. So this paper presents LFC for two area thermal power system based on estimated time delay and packet loss probability using the Markovian approach. The delay and packet loss probability are modeled by different math functions. Normally, frequency deviation signal is transmitted from remote terminal unit (RTU) to control center and from control center to individual control unit of plants. The delay incurred is located in the forward loop of PSO based PI/PID controller in the form of transport delay. To verify the efficacy of controller performance, the estimated constant delay and time varying delay are applied to the controller in the two area thermal-thermal power system with and without governor dead band (GDB) and generation rate constraints (GRC) for various loads conditions. The study is further demonstrated for time delay, being compensated by 2nd order Pade approximation. The results show that frequency deviation is minimum in terms of stability and transient response.

Emulation of static and dynamic characteristics of a Wind turbine using Matlab/Simulink

In this study a separately excited direct current (DC) motor is used to emulate the static as well as the dynamic characteristics of a Horizontal axis Wind turbine (HAWT) which is further driving a Permanent magnet synchronous generator for power generation. This work considers and implements:- Dynamics of the inertia of turbine-generator set; 3 pulse oscillations caused due to tower shadow effect (for a 3 blade HAWT); Mathematical modeling of turbine rotor characteristics. Wind speed reference is given either from recorded wind speed data via a 2-D look-up table or a random sequence generator available in Simulink. The PMSG connected to emulator is maintained at a DC-Link voltage of 1 kV through a closed loop generator control to provide a constant electrical load for prime mover i.e. emulator itself. This whole work is developed and implemented on software environment of Matlab/Simulink 2009a.

Grid interface of photovoltaic-micro turbine hybrid based power for voltage support and control using VSI in rural applications

In this paper a description of a solar photovoltaic (PV)-micro turbine grid interface using voltage source inverter (VSI) has been given for voltage support and control in rural applications. It is assumed that the availability of power in these areas is poor and unpredictable. In such cases a solar PV-micro turbine hybrid system can be used to complement the existing grid supply to improve its service and provide power when the grid supply is not present. A sliding mode control based operation strategy has been proposed for voltage support and control of the supply system. A PWM based VSI has been used to maintain constant and sinusoidal voltage at the point of common coupling (PCC). It has been shown that in the presence of a weak grid or intermittent presence of grid, the solar PV integrated with micro turbine system can be used for providing essential loads during times of power failure and for voltage support during the times when a weak grid supply is available. The results are validated through PSCAD/EMTDC simulation studies.

Performance analysis of converter based variable speed wind energy conversion system

In this paper performance study of converter based wind energy conversion system (WECS) has been obtained. The generator used in WECS for this study is a Permanent Magnet Alternator (PMA) coupled to a wind turbine. It is assumed that the wind speed varies widely at the chosen site of WECS. The wide fluctuation of the wind speed produces variable dc voltage across the ac/dc converter stage. A dc-dc buck converter stage has been proposed to be used in such a situation to robustly hold the output dc voltage to the desired constant value needed for the dc link of the PWM inverter. It is shown through the small-signal modeling of the buck converter that the system has sufficient stability margins to control the output voltage and provide insensitivity against variations in the input voltage due to wind speed variations. Both dc output voltage of the buck converter and ac output voltage of the inverter are controlled through a common control strategy. The proposed wind energy scheme has been simulated and analyzed in the MATLAB/SIMULINK platform for different wind speed variations. The experimental verification of the performance of the buck converter to be used for the WECS has been obtained on the laboratory model using a dc motor-synchronous generator set.

Analysis and implementation of multicarrier modulation techniques for Marx multilevel inverter

Several control strategies have been proposed for diode clamped and flying capacitor multilevel inverters topologies which have their advantages. The observation for multicarrier modulation is quite similar for the above mentioned topologies, where as phase disposition technique has a superior line-to-line harmonic performance over alternative phase opposition disposition and phase opposition disposition techniques. Marx multilevel inverter derived from the Marx generator topology with the features of voltage balancing and boosting capability may find various applications in the field of renewable applications. This paper analyzes and propose the most suitable control strategy for the aforementioned topology. The detailed mathematical analysis and simulation results for various control algorithms for Marx inverter are presented in the paper.

Design and analysis of ripple current reduction in fuel cell generating systems

Fuel cells are being increasingly used in wide range of applications for stand-alone and grid connected systems due to their high efficiency and low emissions. A power conditioning unit, consisting of DC-DC converter and an inverter, is invariably used as an interface between the fuel cell and the load in a typical fuel cell system for ac applications because of unregulated nature of fuel cell voltage. In this research, a comparative analysis of different input ripple reduction methods, input current ripples, the output voltage ripples, and the size of passive components with high efficiency compared with the other topologies is done. The different dc/dc converter topologies is compared such as conventional Boost Converter (BC), Multi Device Boost Converter (MDBC), and Two-Phase Interleaved Boost Converter (IBC), Multi Device Interleaved Boost Converter(MDIBC) to verify its dynamic performance. The DC-DC converter topologies are designed and investigated by using MATLAB/Simulink. The simulation and experimental results have signified that interleaved converter topology is more efficient than other dc-dc converter topologies in achieving high performance and reliability for high-power dc-dc converters.