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The increasing penetration of renewable energy sources in power systems has increased the amount of generating units employing power electronics as their grid interface, instead of synchronous generators. Their different dynamics have brought new challenges for power system operators; in particular, the reduction of the total inertia of power systems, which leads to larger frequency disturbances....
This paper proposes seamless frequency synchronization scheme for fast mode switching of parallel grid-connected inverters operated by droop control in stand-alone mode to grid-connected mode. The proposed scheme analyzes the phase difference between the grid and the inverter for fast frequency synchronization and predicts the synchronization time for frequency increase and decrease. By selecting...
This paper presents the role of Distribution Static Synchronous Compensator (DSTATCOM) in the domain of reactive power sharing and harmonics mitigation in distribution systems under distorted grid condition. Extraction of reference current is done using Synchronous Reference Frame (SRF) based strategy which greatly influences the performance of the DSTATCOM. A modified SRF PLL is used for unit vector...
This paper proposes optimal switching period phase-shifted method for slave inverter to reduce grid current ripples in synchronized two parallel three-phase grid-connected voltage-source inverters (VSI). In parallel operation, a 180 degree phase shifted method generally takes of advantage of reducing grid current ripples in same DC-link voltage for each grid-connected VSI. However, in case of unequal...
This paper presents three three-phase AC-DC configurations in which two are unidirectional and have reduced switch count. The investigated topologies have one DC-link and are composed by two converters in series connection through transformers, that process part of the total power, while the conventional converters have two DC-links and a transformer processing all the power. The replacement of switches...
Frequency and voltage regulation are required to support the grid under different scenarios. In order to handle these scenarios, classical control strategies demand complex systems to fulfill these requirements. However, synchronous controllers are trending strategies to contribute with frequency and voltage regulation functionalities without the requirement of external elements. Among these strategies,...
To avoid the stability problem of grid connected inverter caused by the conventional phase locked loop (PLL), the direct power control of voltage source inverter in virtual synchronous reference frame without PLL is investigated considering grid voltage disturbance in the paper. Based on the small signal analysis methods, comparison between conventional PLL and no PLL is made. It can be found that...
This paper proposes a novel universal control for multi-bus AC microgrid with the capability to operate in both grid-connected (GC) and islanded (IS) modes. The control scheme is based on distributed manner, and the leader-follower consensus protocol is designed. Only few leader distributed generators (DGs) receive the correction signals from the unified mode controller, which is installed at the...
Following the recent trend in the development of the renewable energy market, complemented with the future and emerging technologies, the leading role of the grid connected converter is well established. In the future energy market, as an interconnecting element, it will serve to secure reliable power supply with extraordinary power quality characteristics. This paper will aim at presenting the basic...
The paper proposes a novel voltage event-triggered P-U control strategy for improving related active power sharing accuracy in low-voltage microgrid (MG). Active power sharing inaccuracy is associated with voltages difference of distributed generation units (DGs) that is basically attributed to mismatched lines impedance. So the inaccuracy is inevitable. The proposed voltage control strategy contains...
As power level grows, the power converter of wind turbines tends to use parallel-connected smaller converters. The main reason for parallel is that modular design of those smaller converters is relatively mature and cost-effective. However, the parallel of GSCs (Grid-Side Converters) is notorious for its difficulty in control. Bulky and costly filtering capacitor bank is common and LCL resonance problem...
Since the photovoltaic power generation, wind power and other distributed power supply are volatile and random, they will affect the stability of the grid frequency. In order to improve the voltage and frequency in micro-grid, the virtual synchronous generator control strategy is proposed for inverter control, which can emulate the behavior of synchronous generator, decrease rate of change of frequency...
Formation of microgrids have been proposed as a solution to improve grid reliability, and enable smoother integration of renewables into the grid. Microgrids are sections of the grid that can operate in isolation from the main power system. Maintaining power balance within an islanded microgrid is a challenging task, due to the low system inertia, which requires complex control to maintain stable...
The accurate control of the line current, robust and dynamic behaviour even under distorted grids and the behaviour on other faults are important requirements for grid connected inverter systems. This paper presents a sensorless grid voltage determination system in combination with an direct current control method optimized for multilevel inverters.
In this paper, a new control method of single phase phase-locked loop (PLL) function which can be useful in the electric railway PWM converter system is presented. New PLL system does not use conventional all pass filter (APF) algorithm. Instead, modified moving average filter (mMAF) which has a simple calculation is newly proposed. The feasibility of proposed mMAF method was investigated through...
Nowadays, one of the most challenging design issues of battery-driven real-time embedded systems is how to reduce energy consumption such that the battery life can be prolonged. Based on dynamic voltage scaling technology, many energy-efficient real-time task scheduling algorithms have been proposed, however, relatively little work is done in the presence of task synchronization. In this paper, energy-efficient...
Renew able energy sources have gained momentum in the current trends of effective power generation to overcome global warming due to the pollution caused by existing power generating system. The renewable power will also meet the future demand when existing fuel will be exhausted. Solar power is considerably preferred on account of its easy availability all year round. In this paper, a very efficient...
In this work, a new grid synchronization control strategy is developed for a single stage three phase grid coupled Photovoltaic system that employs Kalman Filter Algorithm (KF) to estimate the fundamental sinusoidal components of the Point of common connection (PCC) voltage and load current respectively. The DC-link bus capacitor voltage is regulated employing a Proportional-Integral (PI) controller...
This paper presents a control scheme for a standalone microgrid having a variable-speed wind-generator (W G) and a diesel-generator (DSG) both directly interfaced at a point of common coupling (PCC), and a battery energy storage (BES) interfaced at the PCC via a bidirectional DC-AC converter. The BES not only regulates the PCC voltage and frequency during wind and/or load power variations, but also...
Phase-locked loops (PLLs) are commonly used for the synchronization of grid connected power converters. However, the standard PLL structures are not able to reject grid disturbances such as voltage harmonics, unbalances or DC components in the measured voltage. Since the response of the power converters depends on the grid phase tracking, it is necessary to ensure an accurate synchronization even...
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