Basanta K. Panigrahi

Islanding detection in distributed generation

In the present times, distributed generation has acquired lots of importance in the power industry. The consequences on the power system develop further significance with the increase in the contribution of distribution energy resources to the electric power production. Nowadays islanding has become a major issue with increase in use of Distributed Generators (DG) in power system. When a part of distributed system becomes electrically separated from the rest of the system and the DG(s) in the isolated portion continues to power the local loads, then this condition is termed as Islanding condition. In this paper, for the detection of islanding in distributed generation, we have used the wavelet transform which is due to the negative sequence component of current and voltage. The islanding condition is further detected when the detailed coefficient at the level-1 (d1) evidently isolates the event.

An analytical approach for optimal size of distributed generation unit

This paper proposes an analytical method to calculate the optimal size for DG for minimizing the total power losses in distribution systems. This analytical expression is based on calculation of coefficient that linearly relates active and reactive power to voltage and angle. A Technique to get the optimal size is presented for DG capable of delivering real power. Besides, grid search algorithm method is also introduced. The DG unit is sized to achieve the highest loss reduction in distribution networks. This method is executed on a typical 22-bus and 58-bus test systems at three different load levels and yields efficiency in improvement of voltage profile and reduction of power losses. Results obtained from the proposed methodology are compared with that of the classical grid search algorithm. The results obtained are encouraging.

A direct torque controlled cage induction generator using back to back PWM converters for grid connected variable speed wind energy system

A wind energy conversion system (WECS) differs from a conventional power system in a lot of ways. In a conventional power plant, the power generation can be controlled easily, as the fluctuations in active and reactive power are not so frequent. But, the power output of a WECS fluctuates with the wind velocity, which makes it difficult to analyze and control. Various approaches have been developed to enhance the performance of a WECS. A variable-speed wind turbine has two back-to-back PWM converters which consists of a machine-side converter for generator control and a grid-side converter for grid-side power control. In this paper Direct Torque Control scheme has been adopted for generator- side convertor control and Grid voltage oriented Vector control scheme is adopted for controlling the grid- side convertor. In both the schemes PI controllers are used. The whole scheme is simulated in Matlab and the results are interpreted.

Detection and classification of faults in a microgrid using wavelet neural network

Abstract It is necessary to detect the fault disturbances as quick as possible to improve performance of microgrid. Keeping an eye to the above issue this paper introduces a novel technique for the detection and classification of different faults in microgrid consisting of as Wind Turbine (WT), diesel generator, Solid Oxide Fuel Cell (SOFC) and micro-turbine. Wavelet transform (WT) and Wavelet Packet Transform (WPT) are used for detection and feature extraction to characterize the various faulted signals by using multi-resolution technique. Further, taking the input feature information of all fault disturbances, artificial neural network (ANN), neuro-fuzzy (NF) and Wavelet Neural Network (WNN) are implemented to accurately classify various faults. Two practically relevant 3-bus system and 14-bus microgrid system comprised with various types of distribution generations are considered for the protection analysis which is simulated using MATLAB/SIMULINK environment. Validation of the proposed technique has been done and compared with other two well proven and extensively used methods like ANN and NF under different operating scenarios.

Detection of Islanding and Fault Disturbances in Microgrid using Wavelet Packet Transform

ABSTRACT Fast detection of islanding is very important for effective operation and control in distributed generation (DG) penetrated distribution networks. The islanding detection techniques such as passive, active, communication, and hybrid have their own merits and demerits. This paper proposed wavelet transform (WT) and wavelet packet transform (WPT) based techniques for detection of islanding and fault disturbances in a microgrid consisting of resources like wind turbine generator, fuel cell (FC), and microturbine. Voltage signal is extracted at the point of common coupling (PCC) and is passed through these detection techniques to obtain the time-frequency multi-resolution analysis. Further, to validate the graphical study, performance indices (PIs) like standard deviation and entropy are calculated for the disturbance detection using suitable selection of threshold. A comparative analysis using WT and WPT is presented in the form of graphical simulation as well as in terms of PIs to analyse their effectiveness and robustness under different operating conditions. It is observed that WPT shows better detection capability in comparison to WT even under 20-dB noisy scenarios.

Probablistic load flow of a distributed generation connected power system by two point estimate method

The modern power system demands more (DG) distributed generation system connected to the power system because of high demand issues. Taking the environmental concern the DG is chosen to be environmental friendly. The generation capacity of such DG are variable because of the source of the energy is highly variable. To connect such system to the exiting power system a analysis must be done to check the distribution system is working perfectly well as per our desire. The probabilistic load flow(PLF) approach is very useful in this scenario to obtain the possible as well as more accurate results. This work explains the solution of various problems of load flow when PV DGs are connected to the system. For the daily operation and for the planning and design purposes the load flow analysis is required. Without considering the uncertainty in load demand, change in the network configuration and outage of generating units, deterministic load flow carries out the calculations where as the probabilistic load flow approach takes all these uncertainties and the solution is obtained in a range which directly proportional to the probability of occurrence.

Detection and location of fault in a micro grid using wavelet transform

The main objective of utility companies is continuous power supply which motivates them for the quick detection and location of faults occurring in a power system. Fault analysis of different fault condition is a difficult task in a Hybrid power system. The wavelet transform is used for the detection and location of fault taking place in a hybrid power system. For proper fault analysis, exact location of the fault distance from the source and type of fault information is very much essential. The proposed model used in this paper is a hybrid combination of wind energy and photovoltaic generation system. For detecting the fault voltage signals are extracted and passed through wavelet transform. Detailed information about the faulted signal is received. The wavelet transform has the special property of time-frequency resolution, from which we can detect the fault. In this paper wavelet transform (WT) is used for determining the location and detection of fault. For clearing the fault in less time detection and location of fault are two important tasks for a power engineer. All the signals are analyzed using the wavelet transform toolbox after selecting the suitable wavelet level. From the analyzed signal the pre fault and post fault coefficients are derived. The fault detection and location study are simulated in MATLAB/Simulink for a typical power system.

Islanding detection in a hybrid power system using continuous wavelet transform

Now a days, Distributed Generation is taking an important part in power systems. In the present scenario distributed generation has given lot of importance in energy systems. With the contribution of the distribution of energy to power generation, the impact on the power system becomes more apart. Now the island has become a major problem in the use of distributed generators (DGs)in the power systems. The increase in the Distributed Generator(DG) in the power system causing major issue of islanding. This condition is referred to as an isolated condition when a portion of the distributed system is electrically separated from the rest of the systems and the DG in the isolated portion continues to power the local load. When DG(s) continues to supply power to a separated power network and another part of it becomes electrically isolated from the power network, this frequent phenomenon is called as Islanding condition. In this paper, in order to detect the islanding effect in distributed generation, we use the wavelet transform components of current and voltage. In this work, we used continuous wavelet transforms which are caused by negative sequence components of voltage and current for the indication of islanding in distributed generation. When the detailed coefficients at level 1(d1) clearly isolate the event, further detection of the island condition.

Impact of STATCOM on voltage profile in a DG penetrated grid connected system

Because of soaring fuel prices, lack of generation and increasing population and demand of electrical power, micro grids formation has become unavoidable. The Micro-grid (MG) concept begins with a combination of loads and micro sources which is operating as a single controllable system which provides power and heat to the local load. These concepts provide a new paradigm for deriving the operation of Distributed generation (DG). A fluctuation in load bus voltage is mainly due to the variation in load. To mitigate the voltage variations at the load buses a STATCOM is employed. In case of non-linear loads, STATCOM not only improves the voltage profile of the load bus but also reduces the total harmonic distortion in the line current. To maintain the load bus voltage at a reference value the STATCOM compensates reactive power. In this paper, the system is dynamically modeled and results are shown. The simulation works are done in MATLAB/SIMULINK.

Evaluation of nodal reliability and nodal prices for deregulated power system

Nodal reliability and Nodal Prices can be very useful for customers as well as to providers to accomplish optimal trading decisions in market trading and operation. A comprehensive method has been introduced in this paper to evaluate nodal reliability and nodal prices in deregulated electricity market. The problem is formulated using Optimal Power Flow (OPF). Generation rescheduling and proportional load shedding is used to release network from violations caused by each contingency states. A 6 bus Reliability Test System (RBTS) is used to illustrate the proposed technique.