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Inverters (dc/ac converters) are commonly used to connect distributed energy resources (DERs) to the grid. Hence, the penetration rate of inverters is growing in distribution systems along with DERs. Depending on their development and penetration level, grid requirement standards for DERs are revised. New grid codes allow DERs to control their output reactive power to provide reactive power ancillary service. In this paper, the main contribution is reactive power management of inverter-based DERs (IBDER) through a practical procedure, which controls the available volt-ampere (headroom) of inverters to improve voltage profile and distribution system operation when confronting with short-term voltage magnitude variations. In this regard, a two-level control strategy (namely, central and local control levels) is proposed. In the central controller, reactive power management of IBDERs is optimized in short time intervals for mitigating voltage variations. The optimized data is sent to the local controllers of IBDERs to increase the speed of reaction to voltage variations in each time interval. The improvement of distribution systems operation with a high penetration rate of IBDERs is illustrated by performing the simulation of the proposed control strategy on a smart distribution test system. [ABSTRACT FROM AUTHOR]

Modern distribution grids and smart buildings comprise unbalanced single-phase, three-phase, DC, and constant power loads and battery energy storage systems (BESSs). This paper presents a hybrid single/three-phase multiobjective automated/autonomous intelligent load (MAIL1) control for smart buildings. The main focus is to autonomously and automatically respond to grid disturbances and power imbalances and unbalances by adaptive demand adjustment of various loads. Also, it can realize regulation objectives of a supervisory operator to enable fast building demand control to participate in performance-based frequency regulation markets. Moreover, it is a unified load control strategy for both grid-connected and islanded hybrid single/three-phase AC/DC grids with smooth transition between them without a need for the strategy reconfiguration. The MAIL1 renders an adaptive and continuous demand for single-phase AC and DC loads. The MAIL1 is based on a fundamentally new controller for single-phase voltage source converters (VSCs) by introducing single-phase DC-source synchronous current converter technology, with extra functionalities such as auto-synchronization with single-phase grids and virtual inertia. Extensive real-time hardware-in-loop results are presented to demonstrate the MAIL1 performance. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid rectifier consisting of a 12-pulse rectifier in parallel with a Vienna rectifier. In the proposed structure, the 12-pulse rectifier supplies the bulk power to the load, whereas the Vienna rectifier shapes the input current to reduce its harmonic distortion. The unidirectional power flow of the Vienna rectifier results in undesirable distortion around the current zero crossing, which deteriorates current shaping in this region. To overcome this problem, besides current shaping, the Vienna rectifier is forced to participate in the active power. In this regard, the share of output power in each rectifier module must be calculated. To shape the input current, the reference current for the Vienna rectifier is generated using instantaneous power theory, and current tracking is carried out using the finite control set model predictive control. A detailed analysis of how to select the output power sharing ratio based on system losses and input current distortion is presented. The theoretical analysis is verified by using simulation and experimental results obtained from a 1 kW laboratory setup. [ABSTRACT FROM AUTHOR]

This paper presents a new multicell topology based on flying capacitor (FC) structure suitable for multilevel converters. The proposed topology employs the concept of phase-shifted carrier pulse width modulation (PWM) with modified modulating signals to generate appropriate PWM signals. The modulation strategy along with all possible switching states are explained. The implementation of the proposed PWM technique is shown by the help of illustrating waveforms. To show the advantages of the proposed structure, different performance criteria are compared with other FC multicell (FCM) structures. Simulation results are used to further evaluate the potential merits of the proposed topology. It is shown that the proposed structure is superior to other FCM-based structures from different standpoints. Specifically, it reduces the number of high-frequency switches, the number of FCs, and at the same time improves the quality of output voltage. A laboratory-type experimental setup is used to validate the modulation strategy and other theoretical findings. [ABSTRACT FROM AUTHOR]