Volume 25, Issue 2

Existence of nonlinear loads makes load power sharing more challenging in the islanded microgrids. Conventional droop control may cause the poor harmonic power sharing among the distributed generations (DGs) due to the mismatched line impedance. This paper proposes an adaptive regulation method of the virtual harmonic impedance for the accurate harmonic power sharing. Consensus algorithm is used to regulate adaptively the virtual harmonic impedance according to the harmonic power sharing error among the DGs with considering of the mismatched line impedance. This method does not require the prior knowledge of the line impedance. The feasibility of the proposed method is demonstrated by simulation result for achieving the accurate harmonic power sharing to reduce the voltage distortion at the point of common coupling (PCC).

In this paper, a novel switched capacitor converter has been proposed to generate 7-levels using seven semiconductor switches (7S7L) to get triple gain in the output voltage which is supplied by a single dc source. A PWM technique, phase disposition pulse width modulation (PD-PWM) has been designed to achieve a suitable switching operation for the 7S7L inverter. In addition, the capacitor voltage is balanced and the suggested inverter uses a charging inductor to decrease the capacitor inrush current, which is a shortcoming in the switched-capacitor multilevel inverters. Moreover, the 7S7L inverter is used to interface the solar panels with the utility grid using a synchronous reference frame-based controller. To check the efficiency, taking actual data, power loss calculation has been discussed for the 7S7L inverter. To illustrate the better performance of the proposed 7S7L inverter than the existing seven-level SC-MLI presented in the literature, a comparative study is also undertaken. To verify the feasibility and effectiveness of the proposed topology, a converter is simulated using Matlab/Simulink. To validate the simulation results, a real-time study is completed using the OPAL-RT 4510 real-time platform.

Thermal analysis of Gas Insulated Switchgear (GIS) modules is of utmost important to optimize their dimensions for higher current ratings. Temperature rise test simulation has to be carried out on GIS modules to ensure that the temperature rise of modules shall not exceed the allowable temperature limits. The analyses also help to estimate the time duration required for GIS modules to reach steady state temperature as per IEC 62271-102 and IEC 61869-2. In the present study, to conduct transient thermal analysis, a novel Thermal Network Model (TNM) has been proposed for gas insulated switchgear equipment of two important modules i.e., disconnector switch (DS) and current transformer (CT). GISmodules.m program is developed in the study to analyze effect of various parameters like type of material being used for HT conductor and enclosure, rated voltage, rated current and enclosure current on time varying behavior of temperature rise of conductor and enclosure. Finally, the temperature rise test has also been carried out on 245 kV and 420 kV GIS modules at rated current ranging from 3150 A to 4000 A. When the transient temperature measurements conducted on 420 kV DS and compared with the results obtained through proposed TNM based analyses, it is clear that temperatures are within difference of 3.3 °C for conductor and 1.2 °C for enclosure. Further, it is evident that the time taken for conductor and enclosure to reach steady state temperature is about 8–10 h depending on enclosure current magnitude and GIS configuration.

In order to expand the detection range and ensure the operation stability, the substation multi-source perception blind compensation detection method based on equipment visual blind area recognition and significance detection is studied. Acoustic sensors are used to collect acoustic signals from visual blind areas of equipment. The characteristics of noise signal are identified by wavelet analysis and noise reduction. The supercomplex Fourier transform model was used to extract the important region in the device image, and the texture features of the region were detected by Gabor filter. The blind compensation detection feature vector is formed by integrating two multi-source sensing features. The detection model of support vector machine is input to complete the blind compensation detection of the substation. The experimental results show that the proposed method is effective for the sound signal feature recognition in the visual blind area and the texture feature detection in the significant area of the device image. The different operating states of each equipment detected by the multi-source sensing feature vector are more accurate, which can realize the purpose of the multi-source sensing blind compensation check of the substation and ensure the safe and stable operation of the substation.

In recent years, environmental issues have gradually become one of the most concerning issues in the world. New energy vehicles have attracted wide attention by their good environmental and social benefits such as zero exhaust emissions and low noise pollution. This paper proposes a regional charging demand forecasting method for electric vehicles (EVs) based on hierarchical charging decision model to solve the problem of charging pile capacity planning, which affects the charging decision behavior of EVs users. The Monte Carlo sampling model is adopted to obtain the time distribution of electric vehicle arriving at each functional area, the distribution of battery state of charge when arriving, and the distribution of average daily mileage. The negative exponential distribution model is used to obtain the average mileage distribution. The fuzzy system theory is proposed to calculate the charging probability, and the fuzzy rule base is adjusted according to the actual data to ensure that the fuzzy rule base is real and effective. Finally, the charging demand distribution curve of electric vehicles in each functional area is obtained by sampling simulation. Through experimental analysis, optimizing the capacity configuration of charging facilities in the station can well describe how electric vehicle users make charging decisions in the actual situation. The research on electric vehicle charging stations can slow down the waiting time of electric vehicle charging, and then affect the process of replacing fuel vehicles with electric vehicles to achieve the development goal of popularizing electric vehicles. It is of great significance for the promotion of new energy vehicles to rationally plan the location and capacity of electric vehicle charging stations.

For environmental reasons, a great effort was focused on the improvement of the steady-state performance and dynamic performance of electric vehicles (EV). The EV is one of the cleanest and most ecological transport solutions. Accurate knowledge of EV load torque signals is important information for controlling and improving EV active safety. The estimation of load torque in EV drive contributes to cost reduction and solves many of the implementation problems encountered: lack of space, and severe environment. On this basis, in this research, our contribution contains two parts. The first part is the conception of a new scheme of control based on synergetic control (SC) for the speed of an EV propelled by a Six-Phase Permanent Magnet Synchronous Motor (PMSMs) is developed. This control technique offers a fast response, decreases the size of modeled system, and asymptotic stability of the closed-loop system in a vast domain. The second part deals with the synthesis of the sliding mode observer (SMO) to estimate load torque, compensate for strong disturbances and achieve high servo precisions. Moreover, reducing the chattering is inherent in the conventional SMO, we have proposed to replace the switching observer term Ksign with a smooth function and super twisting algorithm. The obtained simulation results proved the high performance assured by the synergetic control such as robustness and dynamic performance, and good estimation accuracy with free chattering even in strong noises.

A techno-economic model is provided in this research to assess the viability of using building-integrated battery energy storage systems (BI-BESS) in industries. The factor of β as the ratio of energy to power is introduced in both economic and technical calculations to quantify the economic feasibility of the project with the help of a simple iterative algorithm for battery sizing. The load profile from an industrial building in Malaysia is considered for checking the effectiveness of the results. In addition, the optimum size of the battery achieved by comparing the optimum β from the benefit-cost ratio against β graph, and the ∆ E against β graph. The results show that the optimum battery sizing achieved 84.05 kWh at β  = 1.6. Furthermore, the battery parameters that affect the feasibility of using BI-BESS are evaluated. Finally, the results show that the proposed method is independent of the building load profile, and the same graph will apply to all buildings using the industrial tariff and current BESS technology for checking the feasibility of projects.

Phase-based Alpha ( α ) Plane Relaying (APR) scheme has numerous advantages over the Current Differential Relay (CDR) for transmission line protection. Since the large Restraining Region (RR) in the APR makes high security against CT saturation, channel delay, line charging current and synchronization error. However, the APR loses its sensitivity for high resistance ground faults, especially single line to ground faults under outfeed conditions. Also, losing its dependability under close-in low resistance three-phase faults. Thereby, the sequence-based APR provides enhanced sensitivity with the cost of computational burden and complexity. Hence, in this paper, the concept of the average value ( I Avg ) of both end instantaneous currents is used as an auxiliary logic. In which, the polarity of I Avg is incorporated as an add-on logic to the conventional APR to confirm high resistance internal faults. Thereby, the requirement of sequence components can be avoided (negative and zero). To validate the proposed auxiliary logic, it is tested for the WSCC (Western System Coordinating Council) 9-bus, 110 kV, 50 Hz. System. The simulated results under various fault cases found authenticated results. In addition, the comparative assessment and validation with real-world data reveal the enhanced sensitivity of the proposed logic under high-resistance ground faults.

Adaptive protection is an efficient way to tackle the changing topologies in distribution grids caused by the penetration of renewable energy sources. Effective operation of an adaptive protection scheme requires a fast and reliable communication network. However, inherent time delays can adversely impact the effectiveness of Adaptive Protection Schemes (APSs). This manuscript classifies delays into two types and proposes a method or each type to overcome the effects caused by the corresponding type of delay with an improved APS algorithm. The algorithm uses a combination of centralized and decentralized signaling to counter different types of delays. The improved algorithm is tested on a Canadian 9 bus urban benchmark distribution network. MATLAB Simulink environment is used to simulate the 9 bus benchmark distribution network. The results obtained are demonstrated with the improved scheme on stated test system.

This paper presents a low voltage ride through (LVRT) control strategy using an active power oscillations based reference current generation approach for grid tied solar photo voltaic (SPV) system under line-to-ground (LG) and double line-to-ground (LLG) faults. Proposed control strategy minimizes the harmonics injected into the grid, as well as oscillations in injected reactive power and DC-link voltage. Further this control strategy provides a dynamic control of active and reactive powers, the flow of sinusoidal currents into the grid, and avoids the disconnection between the utility grid and SPV system during faults. A proportional resonant (PR) current controller is developed in a stationary reference frame to achieve the power quality by fulfilling the grid codes. Simulation and experimental results are presented to highlight the merits of the proposed control scheme.

The bearingless motor with dual-winding embedded in the stator can not only produce electromagnetic torque and can also produce suspension force to support the rotor suspension, and the design of the dual-winding will directly affect the torque and suspension performance of the motor. It is a complex problem of multi-objective optimization, multi-performance coupling, and multi-parameter collaborative optimization, which is great significance to improve the comprehensive performance of the motor. Firstly, in order to solve the problem of slot space ratio and turns design of dual-winding under the restriction of stator slot space and thermal loading, the calculation formulas of the electromagnetic torque and the suspension force are derived. The influence of dual-winding design on electromagnetic loading, thermal loading, torque and suspension performance are analyzed. The linear variation of electromagnetic torque with the slot space ratio of torque winding is obtained, and the influence of the dual-winding magnetic motive force on suspension force is clarified. Secondly, in order to obtain the dual-winding design scheme with the optimal torque and suspension performance, the performance parameters of the motor are calculated by finite element method and the influence of the slot space ratios of the torque winding on the torque and suspension performance is analyzed. Based on the coupling analysis of the electromagnetic torque and the suspension force in the case of different thermal loading distributions of dual-winding, the dual-winding optimal design of the bearingless motors is given. Finally, the suspension force of a prototype is tested by experiment.