A. Gargoom

Automatic Classification and Characterization of Power Quality Events

This paper presents a new technique for automatic monitoring of power quality events, which is based on the multiresolution S-transform and Parsevals theorem. In the proposed technique, the S-transform is used to produce instantaneous frequency vectors of the signals, and then the energies of these vectors, based on the Parsevals theorem, are utilized for automatically monitoring and classification of power quality events. The advantage of the proposed algorithm is its ability to distinguish different power quality classes easily. In addition, the magnitude, duration, and frequency content of the disturbances can be accurately identified in order to characterize the disturbances. The paper provides the theoretical background of the technique and presents a wide range of analyses to demonstrate its effectiveness.

A Novel Operation and Control Strategy for a Standalone Hybrid Renewable Power System

This paper proposes a novel operation and control strategy for a renewable hybrid power system for a standalone operation. The proposed hybrid system consists of a wind turbine, a fuel cell, an electrolyzer, a battery storage unit, and a set of loads. The overall control strategy is based on a two-level structure. The top level is the energy management and power regulation system. Depending on wind and load conditions, this system generates reference dynamic operating points to low level individual subsystems. The energy management and power regulation system also controls the load scheduling operation during unfavorable wind conditions under inadequate energy storage in order to avoid a system blackout. Based on the reference dynamic operating points of the individual subsystems, the local controllers control the wind turbine, fuel cell, electrolyzer, and battery storage units. The proposed control system is implemented in MATLAB Simpower software and tested for various wind and load conditions. Results are presented and discussed.

Investigation of Effective Automatic Recognition Systems of Power-Quality Events

There is a need to analyze power-quality (PQ) signals and to extract their distinctive features to take preventative actions in power systems. This paper offers an effective solution to automatically classify PQ signals using Hilbert and Clarke Transforms as new feature extraction techniques. Both techniques accommodate Nearest Neighbor Technique for automatic recognition of PQ events. The Hilbert transform is introduced as single-phase monitoring technique, while with the Clarke Transformation all the three-phases can be monitored simultaneously. The performance of each technique is compared with the most recent techniques (S-Transform and Wavelet Transform) using an extensive number of simulated PQ events that are divided into nine classes. In addition, the paper investigates the optimum selection of number of neighbors to minimize the classification errors in Nearest Neighbor Technique.

Review of Maximum Power Point Tracking approaches suitable for PV systems under Partial Shading Conditions

Maximum Power Point Tracking (MPPT) is an important consideration in Photovoltaic (PV) Systems, particularly as these systems increase in size and are exposed to non-uniform environmental conditions. Conventional MPPT techniques are designed to track the Maximum Power Point under uniform conditions where there is a single maximum power. Under non-uniform environmental conditions, with bypass diodes integrated into the circuit, the Power-Voltage characteristics become more complex resulting in multiple local maxima. Under such conditions, conventional MPPT techniques cannot track the global maxima and may result in considerable energy losses. This review paper explores the approaches designed to mitigate the complexities arising from non-uniform environmental conditions in PV system operation.

A comparative study on effective signal processing tools for power quality monitoring

Due to the growing number of sources of disturbances in AC power systems; there is an ever increasing need for power quality monitoring systems. However, for an accurate analysis, a large amount of data is required in such systems, and there is a need for improvements to analyse the captured data automatically. Therefore, the signals obtained from such monitoring systems require further processing to be able to distinguish the type of disturbances. This paper investigates the efficiency of various signal-processing techniques in detecting and extracting the features of power quality signals. The paper utilizes real time signals in a power system and offers a new technique to monitor all three-phase signals simultaneously, which eliminates the limitations of the existing single-phase based analysis techniques

Control of a direct drive IPM synchronous generator based variable speed wind turbine with energy storage

This paper presents a novel control strategy for a direct drive interior permanent magnet (IPM) synchronous generator based variable speed wind turbine with controlled energy storage. The overall control system consists of a machine side converter controller, a bi-directional dc-dc converter controller for battery energy storage management and load side inverter controller for voltage and frequency regulation. The machine side controller controls the generator speed in order to extract optimum power from the fluctuating wind. The machine side controller is also responsible to achieve maximum efficiency operation of the generator by regulating the d- and q- axis components of stator current. A bi-directional dc to dc battery controller is utilized to balance power generation from the wind and load requirements during wind fluctuations. The load side inverter controller regulates the output voltage and frequency under varying wind and load conditions. The extensive simulation results confirm the effectiveness of the proposed controllers for the wind-battery energy storage based standalone power generation system.

Modeling, simulation and hardware implementation of a PV power plant in a distributed energy generation system

Effective interconnection of stochastically variable renewable energy resources like solar PV (photovoltaic) systems to the grid requires meticulous attention to ensure system compatibility, stability and reliability. The operating characteristics of such PV power plants need to become familiar to power systems engineers and operators. Such familiarity can effectively be achieved only via system modeling, simulation and experimental studies. This paper develops models for an integrated PV power plant which comprises PV array, SEPIC (single ended primary inductance converter) converter, bi-directional de-de converter, dc-ac converter, and battery energy storage system using Matlab/Simulink. The models are used for simulation studies to investigate: 1) the response of the system to the ever-changing environmental variables, 2) the ability to track the maximum power point, 3) the role of the battery energy storage in the mitigation of voltage and power oscillations and 4) the role of the inverter in ensuring compliance to the grid requirements. Experimentally, a DSP (digital signal processing) based control system for maximum power point tracking, dc bus voltage regulation, battery charge/discharge control, dc-ac converter control, system synchronization and protection is implemented and used for the validation of the simulation studies. The simulation and experimental results are presented and discussed.

A comparative study on effective signal processing tools for optimum feature selection in automatic power quality events clustering

The paper presents a comparative study to investigate the optimum feature selection using three signal processing techniques for automatic clustering of power quality events. The techniques include the wavelet transform, the S transform, and the newly introduced forward Clarke transform. The last method has the advantage for monitoring all three phases of a three-phase signal simultaneously. The paper provides unique features for each transformation, and then offers a comparative study that is based on the abilities of selected pairs of features to distinguish power quality events. In the paper, the performance of each signal processing technique is studied and an optimum combination of the most useful features is identified.

Control strategy of a stand-alone variable speed wind turbine with integrated energy storage system using NPC converter

This paper presents a control strategy for a standalone power system comprising of a wind turbine and battery storage systems. The proposed control system consists of a back-to-back NPC converter controller and a bi-directional battery storage converter controller. The back-to-back three-level converter consisting of a machine-side converter and a load side inverter is used to fulfill several objectives. Firstly, the machine-side converter controller is used to extract the maximum power from the variable wind. Secondly, the machine-side converter controller ensures the maximum efficient operation of the interior type permanent magnet synchronous generator. Thirdly, the load-side inverter controller regulates the output voltage and frequency under wind and load variations. A bi-directional dc-to-dc converter is used to control the power flow of the battery storage system under different wind and load conditions. The proposed control system is implemented in MATLAB environment and simulation studies have been conducted for various wind and load conditions.

Performance improvement of a grid connected direct drive wind turbine using super-capacitor energy storage

This paper investigates control and operation strategy of grid connected permanent magnet synchronous generator (PMSG) based direct drive variable speed wind turbine with a static synchronous compensator (STATCOM). The application of STATCOM enhances the system performance by improving the fault ride through capability of the wind turbine. Control strategies for generator side converter with maximum power extraction, grid side inverter and STATCOM controller are implemented in Matlab/Simpower. Extensive simulations have been conducted using supercapacitor energy storage system with STATCOM to enhance the steady state and dynamic performances of the wind energy system under grid faults or disturbances.