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This paper deals with Wind Energy Conversion System (WECS) control equipped by Doubly-Fed Induction Generator (DFIG). Based on variable speed wind turbine and aerodynamic torque estimation, high order sliding mode controller is developed to improve the dynamic performances of WECS by producing the required electromagnetic torque generator. The desired DFIG torque is directly tracked using the proposed...
An average power sharing control strategy for parallel operation of voltage source inverter (VSI) based modular Uninterruptible Power Systems (UPSs) is proposed in this paper. The presented method is based on a modified droop control. The proposed method conquers the drawback of conventional droop plus virtual impedance control, and at the same time some challenges in the real applications have been...
Droop control is widely used in distributed generators for relating their terminal parameters to power generation. These generators are usually assumed to have enough capacities for supplying the required power. This is however not always true, especially with renewable sources with no or insufficient storage. To deal with this issue, an improved droop-based control is proposed for single-phase two-stage...
In order to correct the power factor and limit the flow of harmonics in the source, the effectiveness of active power filters associated to control law is no longer to be demonstrated. Almost all of these methods are designed for a perfect sinusoidal source and do not produce sinusoidal current when the voltages are disturbed. The work developed here concerns active filtering on a perturbed network,...
This paper proposes a multiperiod optimal dispatch model for hybrid voltage source converter based multi-terminal DC (VSC-MTDC) system and AC grids with consideration of optimal coordination of offshore wind farm (OWF) and battery energy storage (BES). The OWF is connected to onshore AC grid by VSC-MTDC. The VSC capacity limits and Grid Code for OWF connection to AC grid are taken into consideration...
Due to the inverter used, DG can not only integrate the active power into power grid but also support the grid with reactive power. This paper proposes an optimal configuration methodology of renewable DG so as to maximize the penetration level of DG considering the temporal characteristics of active-reactive power (P-Q). Further, the uncertainty output of the wind generator, photovoltaic and small...
This paper proposes a full-order terminal sliding-mode based energy saving control for the grid-connected converter of induction motor systems. DC-link voltage and currents controllers of the converter are designed respectively using the full-order terminal sliding manifold and the related control strategies. The chattering in the sliding-mode control is attenuated, and continuous control signals...
This paper presents a two-stage optimization approach to mitigate the rapid voltage fluctuations and minimize the power losses of distribution systems due to the high penetration of photovoltaic (PV) generation. The first stage is a day-ahead optimal strategy which aims to minimize the total voltage deviations and power losses within the constraints of the daily maximum allowable number of operations...
This paper discusses the active and reactive power control method for a modular multilevel converter (MMC) based grid-connected PV system. The voltage vector space analysis is performed by using average value models for the feasibility analysis of reactive power compensation (RPC). The proposed double-loop control strategy enables the PV system to handle unidirectional active power flow and bidirectional...
A multi-time scale coordinated voltage control strategy in an islanded microgrid (MG) is proposed in this paper. The strategy is comprised of local voltage control of distributed generators (DGs), secondary voltage control (SVC) based on PI regulators and a proposed tertiary voltage control (TVC) strategy. A multi-objective function of the TVC is designed to achieve a compromise among three objectives:...
In cascaded-type microgrid, the synchronization and power sharing of distributed generators (DGs) become two new issues that needs to be addressed urgently. In this paper, a unified droop control is proposed and its stability is analyzed in the islanded mode. The proposed scheme can ensure the system stability and accurate power sharing without communication in four-quadrant operations. Finally, simulation...
Nonlinear and unbalanced loads produce power quality pollution to interfaced power systems. Also, photovoltaic systems implementation could worst the situation without proper functioning of active power filters. Now, available active power filters are suffering from to fully suppress interfaced power grid harmonics and distortions under highly unbalanced and nonlinear loads. In this paper, a new approach...
Anew control strategy to achieve high performance from solar photovoltaic system using single stage inverter interfacing grid without maximum power point tracking (MPPT) techniques is investigated in this paper. Sinusoid-tracking algorithm and adaptive filter is proposed to improve the power quality and to regulate constant AC voltage at the point of common coupling (PCC). Proportional integral controllers...
Energy storage technology is an important measure for power output of new energy generation system. T-type three-level structure is adopt as the topology of energy storage inverter. Mathematical model of grid-connected operation in ABC coordinate system and dq coordinate system is built. A double closed loop control strategy of which inner loop current and outer loop power control is proposed. The...
The emulation of synchronous machines is an attractive solution to improve the integration of distributed energy resources in weak grids. In this sense, synchronverters have been widely analysed in the literature, but their digital implementation has been seldom studied. This paper presents the discrete-time implementation of the control algorithms for a battery-supported synchronverter in a weak...
Voltage deviations of dc-link capacitors are the main problem of multilevel diode-clamped converters (DCC). In this paper, a novel carrier-based voltage balance method is proposed to balance the dc-link capacitors of five-level DCCs. The proposed method is characterized by injecting proper zero-sequence voltages in the modulation signals of carrier-based modulators. The effects of the injected zero-sequence...
In recent years, the voltage quality in rural areas has aroused strong concern from the Stat Grid Corporation of China. This paper firstly analyze the over-voltage issues in the rural distribution networks from HUNAN province, and then proposes an output voltage control scheme of the Electric Spring (ES) to alleviate severe over-voltage problem in rural areas. The control objective of the ES is to...
For a unified power flow controller (UPFC) operated in constant power-flow control mode, a novel control scheme of bus voltage regulation is presented. The voltage magnitudes of the ac buses are monitored in real-time operation and are controlled within their limits by the adjustment of the reactive power setting of the series converter. Firstly, the sensitivity of the voltage magnitudes of ac buses...
This paper proposes a parameter design method to optimize the single-phase synchronverter (SPSV) dynamic stability considering the influence of low-pass filter, which in the torque measurement loop and reactive power measurement loop is essential for SPSV to filter out twice the line-frequency power oscillation. The oscillation is inherent from the character of single-phase power calculation. However,...
This paper investigates the effects of unintended island operation mode on parallel inverters' performance for microgrid applications. In the grid-connected mode, each inverter has a different power set point. The power flows between the inverters and the grid. In the islanding mode, the power flows inherently from the inverter that has higher set point power to the inverter has lower one leading...
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