K. Uma Rao

Modeling and control of unified power flow controller for transient stability

FACTS controllers are emerging as viable and economic solutions to the problems of large interconnected ne networks, which can endanger the system security. These devices are characterized by their fast response, absence of inertia, and minimum maintenance requirements. Thyristor controlled equipment like Thyristor Controlled Series Capacitor (TCSC), Static Var Compensator (SVC), Thyristor Controlled Phase angle Regulator (TCPR) etc. which involve passive elements result in devices of large sizes with substantial cost and significant labour for installation. An all solid-state device using GTOs leads to reduction in equipment size and has improved performance. The Unified Power Flow Controller (UPFC) is a versatile controller which can be used to control the active and reactive power in the Line independently. The concept of UPFC makes it possible to handle practically all power flow control and transmission line compensation problems, using solid-state controllers, which provide functional flexibility, generally not attainable by conventional thyristor controlled systems. In this paper, we present the development of a control scheme for the series injected voltage of the UPFC to damp the power oscillations and improve transient stability in a power system

Discrete control of series compensation for stability improvement in power systems

Changes in the network such as connecting a shunt resistor, inserting a series capaciitor, reducing of generation, load etc., when accomplished under a suitable control scheme can improve transient stability. Switching of series capacitors in a transmission line can also help to damp oscillatory power transients. In this paper a detailed analysis and study of a discrete control strategy for the Thyristor Controlled Series Capacitor (TCSC) to improve stability is presented. A single machine infinite bus system is considered to illustrate the development of the control strategy. The energy function is used in determining the switching instants. The control philosophy is later extended to the multimachine system where the energy of the transmission line is used in determining the control strategy.

Discrete control of TCSC for stability improvement in power systems

Changes in the network such as connecting a shunt resistor, inserting a series capacitor, reduction of generation, load etc., when accomplished under a suitable control scheme can improve transient stability for FACTS. Switching of series capacitors in a transmission line can also help to damp oscillatory power transients. This paper presents a detailed analysis and study of a discrete control strategy for the thyristor controlled series capacitor (TCSC) to improve stability.

Implementation of MPPT control using fuzzy logic in solar-wind hybrid power system

The renewable energy sources such as Solar energy and Wind energy are complementary by nature. Utilizing these natural resources to produce power will reduce the power demand on the conventional power generation sector. One of the applications of Solar-Wind hybrid power system (SWHPS) is to reduce the amount of power consumed from the conventional power generation to charge the storage reserves present in the system. The SWHPS comprises of Photovoltaic array, wind turbine, Permanent Magnet Synchronous generator (PMSG), controller and converter. The efficiency of the SWHPS depends on the MPPT controller, which makes the Photovoltaic (PV) and wind power generation system to operate at its maximum power. In PV system Perturb & Observe (P&O) algorithm is used as control logic for the Maximum Power Point Tracking (MPPT) controller and Hill Climb Search (HCS) algorithm is used as MPPT control logic for the Wind power system in order to maximizing the power generated. This paper presents a comparative analysis of MPPT controller built using P&O for PV system and HCS for Wind power system, with MPPT controller implemented using Fuzzy Logic control (FLC) in the both the renewable sources in the hybrid system. The performance of the different implementation of MPPT controllers in the hybrid system are investigated in this paper in MATLAB, Simulink. The SWHPS with the FLC based MPPT has shown to have a better, faster control as compared with the other controllers.

Performance Analysis of a Two-Diode model of PV cell for PV based generation in MATLAB

The increase in concern for carbon emission and reduction in natural resources for conventional power generation, the renewable energy based generation such as Wind, Photovoltaic (PV), and Fuel cell has gained importance. Out of which the PV based generation has gained significance due to availability of abundant sunlight. As the Solar power conversion is a low efficient conversion process, accurate and reliable, modeling of solar cell is important. Due to the non-linear nature of diode based PV model, the accurate design of PV cell is a difficult task. A built-in model of PV cell is available in Simscape, Simelectronics library, Matlab. The equivalent circuit parameters have to be computed from data sheet and incorporated into the model. However it acts as a stiff source when implemented with a MPPT controller. Henceforth, to overcome this drawback, in this paper a two-diode model of PV cell is implemented in Matlab Simulink with reduced four required parameters along with similar configuration of the built-in model. This model allows incorporation of MPPT controller. The I-V and P-V characteristics of these two models are investigated under different insolation levels. A PV based generation system feeding a DC load is designed and investigated using these two models and further implemented with MPPT based on P&O technique.

A modified simple algorithm for detection of voltage sags and swells in practical loads

This paper presents the implementation of a modified sliding window algorithm for the detection of sag and swell, by measuring RMS voltage updated every sample. The trigger obtained can be used in conjunction with the main control system of a Dynamic Voltage Restorer (DVR), or as a triggering function to a digital recorder or to a power line conditioner to detect the occurrence of sag and swell. The modeling of the algorithm and test of its functioning to variations in some of the parameters were carried out in a Matlab - Simulink environment. Reliability of the algorithm under conditions of noise and distortion in the input and to three different types of sags was tested on real data captured during events such as starting of induction motor, intermittent loading of welding transformer, and dynamic loading of a captive diesel generator.

Investigation of small PMSG based wind turbine for variable wind speed

In order to investigate small wind turbines, a comprehensive knowledge of mechanical and electrical parameters is required. Permanent Magnet Synchronous Generator (PMSG) is one of the kinds which are widely used for variable speed and direct driven wind power generating. In order to predict the amount of power that can be extracted by the wind turbine in a concerned area the knowledge of wind speed pattern for that particular location is required. In this paper a case study is selected to study the wind pattern and investigate the performance of the PMSG based wind power generation system for fixed speed and variable speed conditions. Wind power generation system simulated using MATLAB / Simulink consisting of wind turbine, PMSG, diode rectifier, Maximum Power Point tracking (MPPT) controlled boost converter, and DC load is considered. The Hill Climbing Search (HCS) algorithm is implemented using Fuzzy Logic Controller (FLC) for MPPT. The effectiveness of PMSG based wind power generation in the case study is investigated with the environmental conditions recorded at BITS-Pilani, Hyderabad campus, Telangana, India.

Comparing the performance of IDVR for mitigating voltage sag and harmonics with VSI and CSI as its building blocks

Power system is broadly divided into three stages, generation, transmission and distribution. There are several challenges in each stage which are needed to be addressed. This paper concentrates on the challenges in distributed systems called power quality. Power quality improvement is a major concern in the distributed system. There are several power quality problems like voltage sag, harmonics, flickering, distortions etc. Two major problems considered in this paper are the voltage sag and harmonics. To handle with these power quality problems Flexible AC Transmission Systems (FACTS) devices are utilized. Interline Dynamic Voltage Restorer (IDVR) is proposed to eliminate the voltage sag and harmonics. The major aspect of IDVR is being able to replenish energy to the DC link while injecting required voltage in more than one power line unlike the Dynamic Voltage Restorer (DVR). The building blocks of IDVR used for injecting the voltage can either be voltage source inverter (VSI) or current source inverter (CSI). An IEEE 8 bus system is considered, consisting of generation, transmission and distribution levels. The sensitive loads are assumed to be connected at the distribution side The IDVR is installed near the distribution side. The performance of the IDVR in reducing voltage sag and harmonics as its building block either VSI or CSI is investigated and compared in this paper in MATLAB environment.

Real-time detection and analysis of PQ disturbances with DSP using matlab embedded link to code composer studio

This paper presents, the hardware test set-up using a DSP for generation of a trigger signal for real - time detection and analysis of PQ waveforms. The trigger obtained can be used to initiate control of a Dynamic Voltage Restorer (DVR), power line conditioner, or recording of the disturbance by a recorder. The test bed has been successfully tested real time for signals such as starting current in a single phase induction motor, voltage of a welding transformer during intermittent load conditions, voltage of a captive diesel generator under dynamic variations in load. TMS320F6713 Digital Signal Processor has been used and the effectiveness of the algorithm used tested in comparison with the simulation results obtained from Matlab/Simulink.

Identification of PQ disturbances and degree of loading in induction motor using neuro-wavelets

This paper presents a methodology for the simultaneous detection of the load and percentage of PQ disturbance if any in the supply to the induction motor. Stator current signature analysis is used for monitoring the variations in the supply as well as in the load. Wavelet transform is applied to the stator current for the extraction of the signature indicating the variations in the load and in the supply. A feedforward neural network is trained and tested using these wavelet coefficients as input. The output of the neural network classifies the health of the supply, percentage of PQ disturbance if any and the percentage of load at which the machine is running. The entire simulation is carried out using MATLAB. The proposed network has performance efficiency of 95.2%.