Recent Advances in Electrical & Electronic Engineering - Volume 13, Issue 1, 2020

Background: A Standalone Photovoltaic (PV) based system has practical constraints like the need for Energy Storage Devices (ESD) in order to ensure 24 hours availability of electricity and optimized usage of available PV power. Implementation of hybrid renewable energy based system depends upon geographical location and thus availability of a specific energy resource. Also, ESDs are costly to maintain and thus limited optimized usage of ESD is suggested in the literature. Methods: In this paper, a new concept of a PV system integrated with pumped storage is presented for electrification/implementation in rural areas. Proposed system operates at Maximum Power Point Tracking (MPPT) without de-rating the PV capacity or any need of ESD. The control philosophy is simple, robust and ensures two modes of operation for pumped storage i.e. motoring mode and generating mode; depending upon the PV power being generated, load demand and available water level in lower and upper reservoir. Results: The effectiveness of the proposed system and control architecture is verified through MATLAB/Simulink simulation. For various modes of operation, the proposed system is able to maintain DC bus voltage, AC 3-phase voltage, the frequency at approximately constant desired values. Conclusion: However, to operate the PV system at night with heavy loads, additional ESD may be required for better response and stability.

Objective: The estimation accuracy of wind power is an important subject of concern for reliable grid operations and taking part in open access. So, with an objective to improve the wind power forecasting accuracy. Methods: This article presents Wavelet Transform (WT) based General Regression Neural Network (GRNN) with statistical time series input selection technique. Results: The results of the proposed model are compared with four different models namely naïve benchmark model, feed forward neural networks, recurrent neural networks and GRNN on the basis of Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) performance metric. Conclusion: The historical data used by the presented models has been collected from the Ontario Electricity Market for the year 2011 to 2015 and tested for a long time period of more than two years (28 months) from November 2012 to February 2015 with one month estimation moving window.

Background: This paper presents a decoupled control technique for balancing the power and voltage through grid side converter using a solid state transformer. Methods: Decoupling control is essentially a voltage oriented control technique with the objective of eliminating cross-coupling elements. Use of this decouple technique, allows bi-directional power flow control for both active and reactive power, thereby maintaining steady state DC interference voltage. Results: The performance of this scheme is analyzed & the results are obtained from the Matlab/Simulink model. Conclusion: From the above analysis, it can be concluded that the decoupled control strategy can easily eliminate the cross- coupled element of a solid state transformer for the grid side converter.

Background: In modern electrical power distribution systems, Power Quality has become an important concern due to the escalating use of automatic, microprocessor and microcontroller based end user applications. Methods: In this paper, power quality improvement has done using Photovoltaic based Distribution Static Compensator (PV-DSTATCOM). Complete simulation modelling and control of Photovoltaic based Distribution Static Compensator have been provided in the presented paper. In this configuration, DSTATCOM is fed by solar photovoltaic array and PV module is also helpful to maintain the DC link voltage. The switching of PV-STATCOM is controlled by Unit template based control theory. Results: The performance of PV-DSTATCOM has been evaluated for Unity Power Factor (UPF) and AC Voltage Control (ACVC) modes. Here, for studying the power quality issues three-phase distribution system is considered and results have been verified through simulation based on MATLAB software. Conclusion: Different power quality issues and their improvement are studied and presented here for harmonic reduction, DC voltage regulation and power factor correction.

Background: For controlling a back-to-back three-level (3L) Neutral-Point-Clamped (NPC) converter of a Permanent-Magnet Synchronous Generator (PMSG) based Wind Energy Conversion System (WECS), a Refined Model Predictive Control (RMPC) strategy is presented in this paper. Methods: The RMPC strategies of PMSG-side and network-side converters aim at prevention of the high jumps in line and pole voltages of both the converters. A suitable subset of Switching States (SSs), which can prevent these high jumps, is predetermined for each SS. In each control cycle, the RMPC algorithm determines an optimal switching state from an appropriate candidate set of SSs. Results: The functioning of the RMPC algorithms is checked with simulation tests. The effect of parameter uncertainty on the functioning of the RMPC algorithm is also studied. Conclusion: The test results indicate that the RMPC scheme can block high jumps in pole and line voltages while extracting maximal power from wind, controlling network side reactive power, and balancing the capacitor’s voltage.

Background: Solar Photovoltaic (PV) power generating system at the distribution end is emerged as the best solutions to meet the peak power demand during the day time. However, the highly intermittent nature of solar PV system demands a robust control, which is capable of serving a constant load demand even during solar intermittency. Objective: This paper presents a three-phase single-stage grid interfaced solar PV system, which includes PV array, perturb and observe based Maximum Power Point Tracking (MPPT) and Synchronous Reference Frame (SRF) based inverter control. Methods: The proposed three-phase voltage source inverter is controlled to match the DC bus voltage drained from the MPPT controller with sensed DC-link voltage amplitude in order to extract maximum power. The sudden change in irradiance and temperature causes oscillations in the DClink voltage amplitude, which further influences the dynamics of the system. Therefore, Feed- Forward Compensation (FFC) based control method is proposed to overcome the aforementioned limitations. Results: The current FFC method improves the speed of reference current estimation and the response of injected currents into the grid. As a consequence, rise time and settling time of the DClink voltage are reduced considerably. The stability of the voltage control loop is also increased by employing FFC based control method. Conclusion: The FFC-SRF based control presented in this paper offers several features including active power injection at the Unity Power Factor (UPF), power quality conditioning and reactive power compensation for local loads. Extensive MATLAB simulation results are presented for different conditions to validate the robustness of the controller under changing environmental conditions.

Background: Three high input impedances voltage-mode first-order filters are presented. Methods: The first proposed circuit uses one multi-output second-generation current conveyor, two resistors and one grounded capacitor. The second proposed circuit uses two second-generation current conveyors, three resistors and one grounded capacitor. The third proposed circuit uses one multi-output second-generation current conveyor, one resistor and two grounded capacitors. Results: First-order lowpass and allpass filters can be simultaneously obtained in the first proposed circuit. First-order lowpass, highpass and allpass filters can be simultaneously obtained in the second proposed circuit. The third proposed circuit can realize first-order allpass filter. Conclusion: All the proposed circuits have the advantages of high input impedances and using only grounded capacitors.

Background: To the problem that the traditional square laminated machine with passive unwinding control strategy makes the tape speed periodical changing in reciprocating motion and not achieve a good tension control, a novel unwinding system and control algorithm are presented to improve the efficiency and quality of such equipment. Methods: Compared with the traditional passive unwinding control system, the novel tension control system adds an active compliance mechanism. After obtaining the motion relationship between the compliance device and the laminated motion platform through building the complex system mathematical model, the laminated machine tension control is equivalent to a spatial trajectory tracking control, and multi-axis synchronous coordinated control algorithm is used to control their relative motions, and a cross-coupling control in multi-axis coordinated motion is presented to decrease the synchronous error of the two linear servo motors, which are the compliance device driving motor and the laminated motion platform driving one. Without tension sensor, however, good tension control is obtained only by position tracking control. Results: Based on the proposed approaches and novel unwinding mechanism, the tension control was examined on an experimental square lithium battery laminated machine and results of the experiments performed with the experimental setup demonstrated the effectiveness of the proposed approach. Conclusion: Without a tension sensor, good tension control is obtained only by position tracking control in the novel unwinding system, and the production quality and efficiency of the lithium battery laminated machine are improved.

Background: Effective 3D-localization in mobile underwater sensor networks is still an active research topic. Due to the sparse characteristic of underwater sensor networks, AUVs (Autonomous Underwater Vehicles) with precise positioning abilities will benefit cooperative localization. It has important significance to study accurate localization methods. Methods: In this paper, a cooperative and distributed 3D-localization algorithm for sparse underwater sensor networks is proposed. The proposed algorithm combines with the advantages of both recursive location estimation of reference nodes and the outstanding self-positioning ability of mobile AUV. Moreover, our design utilizes MMSE (Minimum Mean Squared Error) based recursive location estimation method in 2D horizontal plane projected from 3D region and then revises positions of un-localized sensor nodes through multiple measurements of Time of Arrival (ToA) with mobile AUVs. Results: Simulation results verify that the proposed cooperative 3D-localization scheme can improve performance in terms of localization coverage ratio, average localization error and localization confidence level. Conclusion: The research can improve localization accuracy and coverage ratio for whole underwater sensor networks.

Background: In this paper, a Proportional-Integral-Differential (PID) controller that facilitates track maneuvering for self-driving cars is proposed. Methods: Three different design approaches are used to find and tune the controller hyperparameters. One of them is “WAF-Tune”, which is an ad hoc trial-and-error based technique that is specifically proposed in this paper for this specific application. The proposed controller uses only the Cross-Track-Error (CTE) as an input to the controller, whereas the output is the steering command. Results: Extensive simulation studies in complex tracks with many sharp turns have been carried out to evaluate the performance of the proposed controller at different speeds. Conclusion: The analysis shows that the proposed technique outperforms the other ones. The usefulness and the shortcomings of the proposed tuning mechanism are also discussed in details.

Background: Power system stability demands minimum variation in frequency, so that loadgeneration balance is maintained throughout the operation period. An Automatic Generation Control (AGC) monitors the frequency and varies the generation to maintain the balance. A system with multiple energy sources and use of a fractional controller for efficient control of stability is presented in the paper. At the outset a 2-area thermal system with governor dead band, generation rate constraint and boiler dynamics have been applied. Methods: A variation of load is deliberated for the study of the considered system with Harmony Search (HS) algorithm, applied for providing optimization of controller parameters. Integral Square Time Square Error (ISTSE) is chosen as objective function for handling the process of tuning controller parameters. A study of similar system with various lately available techniques such as TLBO, hFA-PS and BFOA applied to PID, IDD and PIDD being compared to HS tuned fractional controller is presented under step and dynamic load change. The effort extended to a single area system with reheat thermal plant, hydel plant and a unit of wind plant is tested with the fractional controller scheme. Results: The simulation results provide a clear idea of the superiority of the combination of HS algorithm and FO-PID controller, under dynamically changing load. The variation of load is taken from 1% to 5% of the connected load. Conclusion: Finally, system robustness is shown by modifying essential factors by ± 30%.

Background: In smart grid, a flexible demand response management mechanism is used to achieve the purpose of stabilizing the power grid, optimizing the power market, and rationally allocating resources. There are two types of demand response management in the demand response management mechanism: Price-based Demand Response (PDR) and Incentive-based Demand Response (IDR). Methods: The paper studied the problem of privacy protection in IDR, and proposed a method based on database digital watermark to protect user privacy. Segment the time, and then embed watermarks in the user’s consumption data of each time segment. At the end of each billing period, extract the watermarks from the data of each segment time, and then send the total consumption data of the user of this billing period to the power supply company. The power supply company only knows the total consumption data of the user, the company does not have any information regarding the users consumption data which can prevent them from snooping the user privacy. The proposed digital watermarking algorithm is based on K-Means clustering and wavelet transform, the K-Means algorithm is used to cluster the database tuple data, and then wavelet transform is carried out on the available attribute values within the clusters, and the watermark is embedded in the transformed attribute values. Results: The experimental results show that the proposed method is more robust when the database is under subset deletion attacks, subset substitution attacks and subset addition attacks. Besides, the computational cost is very low. Conclusion: The proposed digital watermark algorithm can embed the watermarks more decently and overcome the burden of watermark embedding caused by statistical feature control. Besides, the proposed method can protect the user privacy better than the other two methods.

Background: This paper deeply studies the influence of the capacity distribution of urban charging and replacing power stations on the distribution network and gives the optimal solution. Objective: The optimal configuration scheme of the charging and replacing station has been given to reduce the impact of the charging and replacing station on the distribution network. Methods: First, the Monte Carlo simulation method is used to extract the influencing factors. The probability load models of the battery replacement station, the slow charging station and the fast charging station are established respectively. The capacity distribution is represented by three different types of charging and switching station configuration ratios. Furthermore, the impact of the charging and replacing power station on the economics and safety of the distribution network is analyzed. Different from other literature, the “peak-filling” model with “minimum peak load”, “maximum valley load” and “minimum peak-to-valley difference” is established, and then PSO is adopted. Results: Finally, the actual configuration is used to compare and analyze the four configuration schemes to prove the superiority of the optimization scheme. Conclusion: Three models have different key influencing factors, so that the electric vehicle load forecasting is more targeted and accurate. The results show that more battery replacement stations can reduce the impact of EV charging on the distribution network, and the construction of the supply replenishment should be based on the construction of the power station.