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In this paper, a hierarchical control system based on a novel autonomous current sharing controller for grid-connected microgrids (MGs) is presented. A three-level hierarchical control system is implemented to guarantee the power sharing performance among voltage controlled parallel inverters, while providing the required active and reactive power to the utility grid. A communication link is used...
Micro-grid should be able to operate in both islanding mode and grid-connected mode, but how to transfer smoothly between these two modes is a question. This paper presents a seamless transition strategy for droop-controlled inverters to operate in both islanding and grid-connected modes and transfer smoothly between these two modes. The control principle and pre-synchronization control strategy are...
In this paper, an improvement in power sharing for Autonomous Microgrid is well established. All previous studies were based on voltage and frequency droop control to share power between distributed generators. This paper develops a new robust voltage and angle droop control to share power, where its advantage over the common frequency droop is in less frequency variation. The synchronization of Power...
Grid-tied micro-inverters are reported to ensure higher energy harvest, but the requirement of large unit quantities raises concerns about cost. Low-cost processors as the control platform are therefore desirable but these are hamstrung with low numerical precision, which causes serious errors while numerically executing the control algorithms. In this paper, the crucial aspect of automatic phase...
The dual-mode photovoltaic inverter is capable of operating either in grid-connected mode or island mode, acting as a current source for the ac grid in the former and a voltage source for the load in the latter. Transitioning from one mode to the next is non-trivial and can cause large deviations in voltage, current, and frequency because a mismatch in frequency, phase, and amplitude between the inverter...
This paper proposes a plug-and-play PV system for DC microgrid based on an analog interleaved flyback converter implementation. The scheme's flexibility allows for the operation to be at the maximum power point tracking (MPPT) or at any power curtailment level, as directed by the DC microgrid control or any suitable analog voltage signal. This novel technique is a very low cost one that utilizes a...
In this paper, we propose a new position sensorless drive system for an interior permanent magnet synchronous motor (IPMSM) with maximum torque control. The proposed method is based on extended electromotive force (EEMF) and voltage injection synchronized with a pulse-width modulated (PWM) carrier. In the proposed method, in order to estimate the magnetic pole position using the EEMF, there is no...
This paper presents a controller for three-phase DC/AC converters that is able to operate the converter in grid-connected and stand-alone modes and ensure seamless transition between these modes without reconfiguration of the control structure. The proposed controller provides control over real and reactive powers in grid-connected mode and it performs voltage support in the islanded mode. It integrates...
This paper proposes a novel wave energy converter (WEC) control technique based on an adaptive vector controller for maximum power absorption of the wave energy resource. The proposed controller arises as a suitable solution for a realistic wave energy converter deployment, as it serves from its own wave energy converter velocity to instantaneously determine the required power-take-off force needed...
In recent years, the Modular Multilevel Converter (MMC) has gained a lot of interest in industry due to its modularity and scalability for different power and voltage levels. However, the control of a MMC consisting of several submodules is often implemented in a central control system, so that the whole MMC system cannot be considered as modular. The thought to distribute control tasks to each submodule...
The Microgrid voltage may deviate from the grid voltage when it operates in islanded mode, which will result in unexpected large inrush currents during the re-connection process. This paper proposed a new self-synchronization control strategy for synchronverter with local loads which utilizes the reference phase angle of synchronverter as the reference angle in the rotating frame. A compensation quantity...
The effects of high-frequency modulation applied to Modular Multilevel Cascade Converter (MMCC) with Double-Star Chopper-Cells (DSCC) can produce high-frequency components across the arm inductors, which are reflected in the DC-link when no common DC-link capacitor is used. The switch-count reduction can be a cost-effective solution in processes of power conversion. This work presents two hybrid single-phase...
To address the generation uncertainty problems introduced by renewable energy power plants, STATCOMs are a typical solution to smoothen the point of common coupling (PCC) voltage in order to facilitate the integration of the renewables. A recently proposed control method — virtual synchronous machine (VSM), which controls grid-interfaced inverters to behave like synchronous machines so as to be more...
The capacitor voltage of an LCL-filter can also be used for active damping, if it is fed back for synchronization. By this way, an extra current sensor can be avoided. Compared with the existing active damping techniques designed with capacitor current feedback, the capacitor voltage feedback active damping would however demand a noise-sensitive derivative term. A digital realization of this derivative...
Synchronization with the power system is an essential part of control of grid-connected converters. This paper proposes a grid-voltage sensorless synchronization and control scheme for a grid-connected converter equipped with an LCL filter, measuring only the converter currents and the DC voltage. A discrete-time pole-placement design method is used to formulate an adaptive full-order observer for...
Fast and accurate synchronization of power electronics interfaced distributed generation to the grid or a microgrid is an important step in the management and utilization of the distributed energy resources. Several synchronization algorithms have been proposed to improve the phase tracking of the grid voltage. However, when the grid is weak or distorted, the synchronization process may suffer from...
This paper presents a method to synchronize doubly-fed induction generators (DFIGs) to the grid using a virtual direct power control (DPC) scheme. The nonlinearity of the hysteresis-based controller in DPC approach causes variable switching frequency for rotor side converter, which complicates the filter design. Also, the large ripples in the stator active and reactive power calculations are the major...
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