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A cluster with multiple AC or DC microgrids (MGs) based on flexible DC interlinking and distributed energy storage systems is studied in this paper, which has been identified to have the following issues in terms of its primary control scheme: coordinated power control among slack terminals in the MG cluster, seamless operation mode transition for the interlinking converters and the common DC bus voltage control. A novel flexible control scheme that unifies the control of all the MGs only using local measured signals without further communications is proposed in this paper, which aims to improve control stability, and operation reliability and flexibility. Theoretical introduction and analysis are presented to explain the proposed control. The detailed average value model and small‐signal model of an MG cluster with two AC MGs and two DC MGs are simulated, respectively, with the proposed control in power systems computer‐aided design/electro‐magnetic transient design and control to verify the effectiveness in control stability and flexibility enhancement, and the impact of control parameters on the small‐signal stability of the considered cluster is analysed through root locus. [ABSTRACT FROM AUTHOR]

Uncertainities and variations of power generation through photovoltaic (PV) sources are major challenges for their integration with the distribution grid. Voltage rise and voltage drop issues limit the increase in PV penetration and loading levels, respectively. Moreover, it is important to maintain voltage levels as per grid code while ensuring that the PV power generation is not curtailed. In this paper, a voltage control method using smart transformer (ST) via dynamic optimal setpoints and limit tolerance is proposed in a residential distribution network. Performance indicators are developed to understand the impact of the proposed method on the system voltage profile. A method to determine the optimal inputs for voltage control methods depending on the day-ahead predictions of load demand and PV power profiles is developed. Further, a voltage control method of switching among three setpoints based on the voltage that determines the load side ac reference voltages for ST is proposed. The proposed method is compared with the method of switching between two setpoints based on current. The proposed method provides an improved voltage profile in the distribution network, which is tested on a CIGRE low voltage residential distribution network using PSCAD [ABSTRACT FROM AUTHOR]

The variable step size modified least mean square (VSSMLMS) learning algorithm based multifunctional double‐stage grid interactive photovoltaic (PV) system is implemented in this paper which feeds power to the grid and the load, ensures unity power factor operation and compensates reactive power. Along with this, it mitigates high grid neutral current during unbalanced loading condition. This algorithm uses variable step sizes to have a smooth dynamic and steady state performances. The boost converter (booster) is used in the first stage to extract peak power from a PV array using perturb and observe peak power point tracking technique. Next to this, a four leg voltage source converter (VSC) is placed to interlink the solar PV system to the grid and the loads. VSSMLMS‐based control technique is used to filter the fundamental component of load current and hence gate pulses are generated for the four‐leg VSC. This system is simulated in SIMULINK/MATLAB software under several working conditions and the obtained simulation results are validated on a developed laboratory prototype. The performance of the VSSMLMS‐based control technique is compared with that of the traditional LMS‐based technique. All results validate the IEEE‐519 standard. [ABSTRACT FROM AUTHOR]

The conventional hierarchical control in an islanded microgrid (MG) does not consider the long time‐span dynamics of distributed storages (DSs). The main challenge in control of battery energy storage systems (BESSs) is different levels of stored energy in terms of state of charge (SoC). In power droop control, the energy of the BESSs with lower initial SoC is drained earlier, and their capacities become unachievable. Moreover, using droop control to balance the SoC of BESSs, deviates the steady state frequency and voltage from the nominal values. However, restoration of the MG frequency employing the conventional distributed secondary controllers disturbs SoC‐balancing, since SoC of BESSs are ignored. In this paper, a new distributed storage secondary controller (DSSC) scheme is designed for restoration of the voltage and frequency of a stand‐alone MG, and to provide power‐sharing and SoC‐balancing, using a distributed cooperative architecture. The cooperative DSs are controllable and exchange the information with neighbor DSs through a communication network. The unknown output power of the uncooperative renewable distributed generation (DG) is considered as external disturbance to the DSSC. The designed DSSC is robust against the variation of the communication configuration, and eliminates the necessity to communicate with uncontrollable DGs and loads. [ABSTRACT FROM AUTHOR]

This paper describes an intelligent sensor fault detection and compensation (FDC) scheme for a hybrid grid involving renewable energy (RE) sources with power electronic interfaces. To evaluate the sensor FDC scheme, a wound rotor induction generator (WRIG)‐based wind energy system connected to the hybrid grid is examined. The system employs a WRIG with excitation from DC RE grid via a single, rotor side converter. To analyse the dynamic performance, a decoupled voltage vector control is employed. The sensors involved in the control algorithm may not be ideal and if fault occurs might lead to system collapse. To overcome electrical sensor failure, a robust, intelligent sensor fault control scheme is proposed with ANFIS. A hardware‐free solution with PLL block is proposed for mechanical sensor fault. The ANFIS‐based FDC scheme involves a bank of observers that computes residuals, detects and isolates faults. When fault occurs, the observer output is utilised for the execution of control algorithm thereby avoiding system collapse. The focused system is simulated in MATLAB and experimentally tested with a dSPACE controller for various fault scenarios. The results show the effectiveness of the FDC scheme. [ABSTRACT FROM AUTHOR]

In this paper, a decentralized control strategy for inverter‐based distributed generation (DG) is proposed to enhance the accuracy of power sharing under unbalanced load conditions in low‐voltage microgrids. The proposed method includes two important saliences: (1) accurate unbalanced current injection from DGs, and (2) reduction of circulating real and reactive powers in an islanded microgrid. The features are complied with the proposed droop strategy utilized in the control system of each phase of DG converters. Based on the proposed triple‐droop control strategy, the real power sharing in an AC low‐voltage microgrid is significantly improved via P–V control strategy and the reactive power sharing accuracy is enhanced via Q–f control strategy. By this method, the amplitude of the output voltage of each phase of the converters is determined based on the amount of load connected to that phase. In addition, the efficiency of the microgrid is increased due to the circulating current reduction between DGs. A virtual impedance concept is also utilized to improve the accuracy of the proposed power sharing method. The feasibility and effectiveness of the proposed strategy are validated using MATLAB/SIMULINK software for International Council for Large Electric Systems (CIGRE) low‐voltage distribution network benchmark. [ABSTRACT FROM AUTHOR]