Recent Advances in Electrical & Electronic Engineering - Volume 13, Issue 4, 2020

Background: This paper reviews the requirements imposed by Transmission System Operators (TSOs) in their grid codes to address intolerable implications of integrating large Wind Power Plants (WPPs) to the grid. Besides the common objectives, terminologies used by different TSOs were distinct. Therefore, developing a harmonized grid code is imperative. Introduction: On the recommendation of the European Commission, European Network of Transmission System Operators for Electricity (ENTSO-E) has made concerted efforts in the direction of developing a harmonized grid code, and published its document in March 2013. Method: Several TSOs have updated their grid codes in accordance with the increasing wind energy penetration. We have made an effort to present a comparison between different integration requirements specified by different grid codes. The outcomes presented will certainly be beneficial to the countries, which are in the process of enacting their own grid code. Results: We have reviewed different grid codes in terms of Low Voltage Ride-Through (LVRT) requirement, operating voltage and frequency range, active power control (frequency regulation) and reactive power support (voltage regulation). Conclusion: The present study envisages helping wind turbine manufacturers and WPP developers, as it would provide them a clear insight into the regulations imposed on WPPs as included/ updated in different grid codes.

Background: Wind energy generation has emerged as the fastest growing renewable energy technology in recent years. Among different wind turbine configurations, Permanent Magnet Synchronous Generator (PMSG) based wind turbines are becoming popular due to several advantageous features associated with this. Introduction: In the events of grid fault, active power delivery to the grid is required to be stopped or reduced as per the grid code specification and due to this mismatch between power generation and power delivery results in a rise in DC link voltage and high stress on converter switches. Modern grid codes suggest Wind Power Plants (WPPs) to remain in operation and such requirements are termed as Fault Ride-Through (FRT) or Low Voltage Ride-Through (LVRT). Method: Several LVRT enhance method have been proposed in the literature in the past having distinct pros and cons. Some of them employ external means and some suggest modification of existing control in order to meet LVRT requirement specified by the grid code. Methods based on external devices may be simple and effective but in some cases, they are not cost effective. Literature suggests the use of a modified controller based method for meeting LVRT requirement economically. Results: This paper presents a review of different LVRT enhancement methods for PMSG based Wind Energy Conversion Systems (WECSs). In order to compare the performance outcomes of LVRT enhancement methods, several simulations are performed for an example WECS based on 2MW PMSG on MATLAB/Simulink platform. Conclusion: Based on the analysis of simulation results, Modified controller based methods and FACT devices are found cost-effective solutions for LVRT enhancement.

Objective: A new method based on stochastic modeling of simultaneous optimal reconfiguration of distribution networks and allocation of multiple Distribution STATic COMpensator and renewable energy resources as new developed technologies is suggested in this paper. Background: This problem involves vital uncertain parameters such as: intermittent nature of renewable energy sources, load forecasting and market price errors. Krill Herd Algorithm as a powerful optimization solution is applied to solve suggested problem. Methods: Several effective cost based consequences can be achieved by proposed technique like: DG units installation and operation costs, D-Statcom installation cost, capacitor costs, cost of purchased energy from the transmission network, active and reactive power losses cost, line upgrade cost and distribution system reconfiguration cost. Results: In addition, energy not supplied as a vital reliability index incorporated in the cost function aims to improve network’s reliability efficiently. Conclusion: IEEE 33 bus radial distribution system is used here to check the practicability of the proposed scheme.

Background: The conventional method using one-degree-of-freedom (1DOF) controller for Permanent Magnet Synchronous Motor (PMSM) servo system has the trade-off problem between the dynamic performance and the robustness. Methods: In this paper, by using H∞ control theory, a novel robust two-degree-of-freedom (2DOF) controller has been proposed to improve the position control performance of PMSM servo system. Using robust control theory and 2DOF control theory, a H∞ robust position controller has been designed and discussed in detail. Results: The trade-off problem between the dynamic performance and robustness which exists in one-degree-of-freedom (1DOF) control can be dealt with by the application of 2DOF control theory. Then, through H∞ control theory, the design of robust position controller can be translated to H∞ robust standard design problem. Moreover, the control system with robust controller has been proved to be stable. Conclusion: Further simulation results demonstrate that compared with the conventional PID control, the designed control system has better robustness and attenuation to the disturbance of load impact.

Background: Network security is used to secure data transmission over the wireless network. Encryption of information plays a vital role in communication since it protects the sender and receiver from the hackers trying to access the information. Objectives: In recent years, protecting the information data has become a challenging task for the researchers. Hence, there is a need to improve the existing methods of secure data transmission. Method: In this paper, a new approach is proposed to implement a better security chip for secured data transmission. It is based on the combination of encryption and description as well as the compression techniques. The proposed design focuses on the reduction of delay in the circuit using the compression approach. Results: The various simulations are carried out using the Xilinx, and MATLAB software. The timing signals are observed on Xilinx and the proposed algorithm has been simulated and tested on MATLAB. Conclusion: The presented approach performed better and achieved a good compression ratio and hence the loss of information was less at the receiving end.

Background & Introduction: With the advent of technology, though the literature highlights many designs of Phase Frequency Detector (PFD), there remains some challenges like area overhead, switching noise near frequency lock point and fast, accurate response to mitigate dead zone and output errors. Methods: In this article, we have unearthed a low power, high speed and dead zone free PFD, which eliminates the switching noise near that lock-in node. This simple design uses lesser number of transistors to obtain smaller estimated layout area of 0.748mm² and low power of 496.12μW, when operated at 10 GHz frequency at a power supply of 1.8V in 90nm CMOS technology. Results: The simulation reads a phase noise and output noise of -113.142dBc/Hz and -180.712dB at 1MHz offset. The circuit not only runs at a frequency as high as 40GHz, but also compatible to be operated at a power supply of as small as 0.9V. Conclusion: Process Variation analysis performed proves the robustness of the proposed circuit at all process corners. Also, the design gets validated at lower process nodes like 28nm UMC.

Background: In Multilevel Inverters (MLI) as the number of level increases, there is a proportionate increase in the count of the semiconductor devices that are employed. Methods: This paper deals with an asymmetrical cascaded H-bridge inverter topology with half bridge cells to produce seven level output voltage waveform. Nearest Level Control (NLM) technique is used to produce the switching pulses. The operating principle of the proposed MLI and its performance abilities is verified through MATLAB/Simulink and a prototype is developed to provide the experimental results. Results: Total Harmonic Distortion (THD) is computed for proposed MLI for different types of loads in simulation environment as well as in the developed hardware prototype. Comparison between the proposed MLI and recent topologies demonstrates the advantageous features. Conclusion: The simulation and hardware results confirm the suitability of the proposed seven level MLI as the total component count, and the requirement of DC sources reduces considerably.

Background: Technical feasibility of Ultra High Voltage (UHV) Transmission system is proven through many UHV projects worldwide and research is going on to make it commercially viable. The rapid development of Power Electronics in the field of UHV AC power system has resulted in the economic and efficient transmission of bulk power over long distances. Methods: In order to improve the voltage profile of the transmission system, power transfer capability, transient and dynamic stability; Flexible AC Transmission System (FACTS) devices have been introduced at UHV level. The present paper focuses on the design and evaluation of TCSC system for the Indian UHVAC system for its Wardha Aurangabad Line, which is at present operating at 400 kV but will be upgraded soon to 1200 kV. A flow chart is prepared for the determination of the values of TCSC inductor and capacitor. Results: PSCAD/ EMTDC Software-Simulation based study is carried out to analyze the behavior of the UHV transmission line with TCSC. The effect of improvement in power transfer capability, with and without the use of TCSC scheme; through Constant- Current mode, closed-loop control has been investigated for a healthy line and a faulty line. Conclusion: With the use of TCSC, an increase of 52% is observed in the power transfer capability of the line, which is raised from about 5000 MW to 7777 MW. The paper will prove a milestone for academicians, researchers, and design engineers in the field of Power Electronics and Power Systems.

Background: The security assessment plays a crucial role in the operation of the modern interconnected power system network. Methods: Hence, this paper addresses the application of k-means clustering algorithm equipped with Principal Component Analysis (PCA) and silhouette analysis for the classification of system security states. The proposed technique works on three principal axes; the first stage involves contingency quantification based on developed insecurity indices, the second stage includes dataset preparation to enhance the overall performance of the proposed method using PCA and silhouette analysis, and finally the application of the clustering algorithm over data. Results: The proposed composite insecurity index uses available synchronized measurements from Phasor Measurement Units (PMUs) to assess the development of cascading outages. Considering different operational scenarios and multiple levels of contingencies (up to N-3), Fast Decoupled Power Flow (FDPF) have been used for contingency replications. The developed technique applied to IEEE 14-bus and 57-bus standard test system for steady-state security evaluation. Conclusion: The obtained results ensure the robustness and effectiveness of the established procedure in the assessment of the system security irrespective of the network size or operating conditions.

Background: The study of induction motor behavior during abnormal conditions due to the presence of faults and the possibility to diagnose these abnormal conditions has been a challenging topic for many electrical machine researchers. Objective: Direct Torque Control (DTC) is applied to the control of an induction motor in healthy and an open circuit fault in the PWM three phase voltage fed inverter. Neural DTC is developed and used to improve the dynamic behavior of the drive system under faulty switch occurrence. Methods: The validity of the proposed control scheme is tested under normal conditions and switching fail in the Voltage Source Inverter (VSI) caused by an open circuit. Through a simulation testing of an induction motor drive system at different speed references, a comparison between basic DTC and Neural DTC is performed. Results: Simulated results on 1.5-kW induction motor drive show the performance of the proposed control in normal and faulty cases. The stator current, flux, torque, and speed at different references are determined and compared in the above techniques using MATLAB-SIMULINK. Conclusion: A Neural Network (NN) DTC control system under an open switch fault is proposed without the need for classical switching table. The use of hybrid intelligent techniques aims to improve the DTC performances in case of multiple faults occurrence.

Background: Aiming at the power fluctuation of wind/ photovoltaic (PV)/ energy storage (ES) hybrid energy conversion system injected into the grid, this paper builds a mathematical model system of distributed microgrid with PV coupling to the DC side of the doubly fed induction generator (DFIG) and proposes hierarchical and phased power coordination strategy. Methods: The hydrogen storage part and the Supercapacitor (SC) are used as backup power and power adjustment units to ensure power supply reliability and compensate for the shortcomings of wind and solar energy intermittent. The power coordination strategy assigns power reference control and the power controller follows the reference value (i.e., hierarchical control). The electrolysis cell (EL) and the Proton Exchange Membrane Fuel Cell (PEMFC) perform phased power control (i.e., minimum power, rated power, maximum power). The SC is divided into two operating modes, which are the same or opposite to the EL/PEMFC output power direction. Results: To reduce the wait time of the SC, the SC is free to switch between the two modes by setting the recovery voltage. The SC is mainly aimed at wind speed and load abrupt changes, and the hydrogen storage part is designed to solve the short-term energy shortage and surplus. Conclusion: In the 3-machine 9-bus system, the actual wind power, irradiance and temperature data of North China are used for verification. The method can effectively balance the wind wave fluctuation power, prolong the life of the EL, fully utilize the space of the SC, and reduce the cost.

Background: With the increase of Electric Vehicle (EV), their disordered charging behaviour will put great pressure on the stable operation of the distribution network. Methods: In order to study the charging and discharging optimization scheme of EVs, firstly the EV charging and discharging load model is founded based on the Vehicle-to-Grid (V2G) technology. Results: According to the electricity price mechanism of Shanxi Province, the paper proposes a multi-target charging and discharging optimization for EVs based on the evolution of EV State of Charge (SOC) using the Modified Particle Swarm Optimization (MPSO). Conclusion: Compared with the disordered charging mode, the method proposed in this paper can simultaneously reduce the network loss of the distribution network and the cost of EV users.

Background: The elderly are prone to do some abnormal behaviors, such as tumbling or stepping out of the guardians’ monitoring area. These abnormal behaviors bring enormous hidden dangers to the health of the elderly, which need to be monitored effectively in order to be dealt with in time. Objective: Provide an approach based on Wireless Sensor Network (WSN) and Multi-Layer Perceptron (MLP) to establish the behaviors monitoring system for the elderly. Methods: A behavior monitoring system based on wireless sensor network and neural network is proposed in this paper, according to the behavior characteristics of the elderly. The system collects real-time behavior data of the elderly by wearing a bracelet with acceleration sensors wore on their hands. And then a behavior recognition model of the elderly is established through the MLP and the collected behavior data. The established behavior recognition model is used to classify and identify the five typical behavior characteristics of the elderly, such as walking, sitting, lying, standing and tumbling. At the same time, the location information of the elderly is estimated by the centroid localization technology based on Received Signal Strength Indication (RSSI) ranging. Results: The experiment results show that the designed system can timely acquire the behavior characteristic parameters of the elderly, and it can accurately identify the five typical behaviors with a 100% recognition accuracy rate. And also, it can timely give the warning of the abnormal behaviors of the elderly, such as tumbling or walking out of the active area. Conclusion: The proposed system in this paper can accurately identify the abnormal behaviors of elderly and timely inform the guardians. The proposed monitoring method can effectively reduce the hurt injury elderly, and can improve the work efficiency of guardians. And it has its theoretical and practical value.