International Journal of Industrial Electronics, Control and Optimization
Volume:5 Issue: 2, Spring 2022

With an increasing penetration rate of electric vehicles in distribution networks, it is becoming vital to schedule their battery charging/discharging to maintain the network balance and increase the vehicle owners’ profit. Electric vehicles are now considered one of the most important and accessible sources of revenue for their owners since they can be connected to the grid (V2G) as a power source during peak hours. As such, while flattening the power profile, they can improve the voltage drop across the grid buses. If charging/discharging of the vehicles is scheduled irregularly, the power drawn from the phases will become unbalanced, which can cause global outages and impair system stability in addition to increasing the harmonic volume and decreasing power quality. The present paper uses dynamic programming to reduce operating costs and enhance the profits of vehicle owners who participate in the V2G program. This optimization algorithm eliminates the undesirable paths leading to unconventional responses in the search space, which will greatly increase the speed and accuracy by which the optimal response is achieved. This model, along with multi-part tariffs on electricity prices, can lead to the more active participation of vehicle owners and help improve the power quality indices of the electrical parameters of the grid. The proposed method is simulated on a sample distribution network, and the case studies conducted prove the validity of the proposed algorithm.

This paper applies a new state feedback control to a distributed secondary voltage and frequency control in an islanded microgrid. The problem is focused on the output consensus of the multi-agent systems, which is converted to a first-order dynamic system. The inverter-based distributed generations play as agents in the proposed control strategy. It is assumed that the distributed generators communicate through a communication network modeled by a directed graph (digraph). The distributed output consensus is used to design the secondary controllers. Such innovative controllers synchronize distributed generators' output voltages and frequencies to their reference values by a novel state feedback approach. Compared to the existing consensus protocols, the proposed method provides a different innovative solution to the secondary voltage and frequency control of microgrids, which has a better response in case of communication failures. Finally, extensive and comparative simulations have been presented to verify the validity of the proposed control strategy and the system performance.

The robust adaptive leader-follower formation control of uncertain unmanned surface vehicles (USVs) subject to stochastic environmental loads is investigated in this paper. The stochastic additive noises are included in the kinematics which stands for the un-modeled dynamics and uncertainty. The disturbances induced by waves, wind and ocean currents in the kinetics are also separated into deterministic and stochastic components. A comprehensive model including kinematics and kinetics of each USV agent is then derived as stochastic differential equations including standard Wiener processes. Thus, the problem formulation is much more challenging and practical since both the exogenous disturbances and kinematics states are defined by stochastic differential equations. In order to guarantee that all the tracking errors converge to a ball centered at the origin in probability, quartic Lyapunov functions synthesis, dynamic surface control (DSC) technique, the projection algorithm, and neural networks (NNs) are employed. Finally, the simulation experiments quantify the effectiveness of proposed approach.

Providing purified water in marine and domestic applications, especially in remote areas regarding fossil fuels environmental pollutants, makes it hard to use conventional energy sources. Therefore, the present research seeks to construct a water purification system by using reverse osmosis technology supplied by a novel wind turbine driven by a permanent magnet synchronous generator. To reach this goal, an efficient high torque wind turbine was designed with new butterfly blades, determining the lift and drag forces along with creating twisting angles in blades. The blades were initially designed in SolidWorks software. Then, the computational fluid dynamics principles were simulated in the COMSOL5.2a environment by utilizing the k-ω pattern and multi-reference coordinate axis method. A laboratory prototype was implemented to verify the theoretical calculations, simulation analysis, and validity of the wind turbine. To ensure the sufficient capability of the system in worse situations, the performance of the turbine system at a low wind speed of 4 m/s was evaluated. The results showed that a maximum power factor of 0.29 was obtained, making the micro-turbine appropriate for both marine and domestic sweetener systems.

Load sharing, as an important challenge in microgrids (MGs), is realized commonly via a droop control method. Conventional droop control methods are not applicable in unpredictable renewable energy sources (RESs) like photovoltaic (PV) and wind turbines (WT) because their output power depends on the weather conditions and can be extracted only if these free sources are available. This paper, considers two operating modes for these types of sources as Maximum Power Point Tracking (MPPT) and DC-link Voltage Control (DCLVC). These power sources usually operate in the MPPT mode unless the load of the MG drops to a lower level compared to the maximum power generation by RESs, in which case the sources switch to the DCLVC operating mode. This study proposed a method based on enhanced droop control, which helps RESs to choose its control mode locally without communication and share the demand of the AC MG with other dispatchable sources besides supplying its maximum power. The proposed method focused on supplying MG load from RESs as much as possible and simplicity in implementation. MG frequency helps the proposed controller to select its operation mode. Enhanced control for DC link voltage control is offered for inverter based RESs. The validity of the proposed method is approved by simulations in the MATLAB/SIMULINK environment.

Electrical energy regeneration and storage in a tall structure with the installed passive pendulum tuned mass and damper (PPTMD) is investigated. While the passive vibration absorbing system works as an energy harvesting device, an electrical system including an electric motor, power electronic converters, a battery charger and storage subsystem are designed in order to store the energy taken from the structure vibrations which may be resulted from various external disturbances such as wind or earthquakes. The whole 76-story structure and the relevant electrical energy regeneration system are modeled and simulated and the design scheme is implemented on a two-story reduced order lab structure equipped with PPTMD, the electronic circuit and the battery. A boost AC rectifier is designed and controlled to rectify the AC output voltage and is followed by a boost DC-DC converter as a battery charger for the Li-ion battery. A passivity-based controller (PC) and a sliding mode controller are designed for the rectifier and the battery charger, respectively. The simulation and the real test results demonstrate the efficient harvesting and storage of the energy extracted from the building.

Phase locked loop (PLL) circuits are widely used in fractional frequency synthesizers. In these synthesizers, fractional multiples of the reference frequency can be synthesized, so the reference frequency and the bandwidth of the loop can be increased. This frequency synthesizer is commonly used due to its flexibility and convenient frequency adjustment. In this paper, a PLL circuit of the transistor level is designed in which a hybrid digital sigma-delta modulator with reduced hardware is used. This Digital Delta-Sigma Modulator (DDSM) has four stages that have a lower noise level and power consumption than the conventional type. This PLL circuit has a third-order loop filter and a voltage-controlled oscillator of the NMOS type. In the PLL circuit, two counters are used in its feedback path. In the proposed divider, there is a dual divider P / P + 1 (in this case 5, 6) which divides its input signal by 5, 6 according to the control input. A design example for the PLL is provided. A third stage digital Delta-Sigma modulator with reduced hardware is also used to control these counters. This modulator has less power consumption than the conventional method and has less number of transistors by 85%.

Recent technical advances in Wide-Area Measurement Systems (WAMS) have made it possible to use a combination of measured signals from remote locations to design centralized control. However, the transmission delay of remote signals and changes in the power system operating point are significant issues in the operation of the Wide-Area Damping Controller (WADC). Regarding issues and uncertainties in the power system, mixed H_2/H_∞ synthesis has been proposed for wide-area robust controller design. In this paper, an adaptive wide-area robust controller for Thyristor Controlled Series Capacitors (TCSC) is presented to improve the inter-area oscillation damping in multi-machine power systems in which the time-varying delays in feedback signal time are taken into account. So, an Adaptive Delay Compensator (ADC) is used to compensate for the delay of receiving remote signals. Despite the nonlinearity of the power system, the changes in the operating point, and the presence of time-varying delays, the proposed scheme shows robust performance in damping the low-frequency oscillations. The efficiency of the proposed control system in the presence of TCSC is shown through simulation results that show its superiority over the conventional control system. The simulation of the paper is carried out on the Four-Machine Two-Area test system and 10-machine, 39-bus New England power system.