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The low-voltage ride-through (LVRT) capability of a MW-Level variable speed wind turbine with a direct-driven permanent magnet synchronous generator (PMSG) is a hot topic these days. To prevent over-rated dc-link dynamic voltage, a novel dc-link voltage control scheme is proposed. In this paper comparing with traditional control method, the generator-side converter uses a doubly closed loop namely...
This paper proposes an LVRT (low-voltage ride-through) of multi-pole permanent-magnet synchronous generator (PMSG) for wind turbine systems under the grid fault condition and varying wind speed using the energy storage system (ESS) and braking chopper (BC). The proposed topology can reduce the ESS power rating and improve the output performance. A detailed design procedure and control strategy for...
A transformer based voltage sag generator to test renewable energy systems is presented. Design considerations concerning overvoltages and overcurrents during switching action are addressed. Measurement results of a 30 kW laboratory prototype testing a line side PWM converter and a DFIG are presented. Both measurement results for investigations on the transformer based sag generator at the line side...
This paper explores the performance of alternative voltage control strategy applied to direct drive synchronous wind generators, more specifically with permanent magnetic (PMSG). The reactive power control of the grid-side converter is investigated for voltage control purposes. In Brazil, the Grid National Operator (ONS) requires that wind turbines stay connected to the grid during voltage dips, but...
Notwithstanding the positive environmental impact, the increasing penetration of Distributed Generation (DG) units connected to the distribution network raises new topics concerning the expected response of these during outages. Grid disturbances especially at the transmission level can cause the unwanted disconnection of large amounts of DG, leading to undesired power imbalances causing line overloadings...
Wind energy conversion systems using the doubly-fed induction generator (DFIG) are the most commercialized topology worldwide, because this technology uses converters dimensioned for ±30% of the system rated power, thus reducing the equipment cost. The direct connection of the DFIG stator to the electrical system increases its sensitivity to grid disturbances. In this context, this paper analyzes...
This paper has an objective to combine and disseminate information on sea wave energy converters. The potential of sea wave energy is very high and over one thousands patents exists, however, only selected projects supported by EC are presented. At the beginning a basic terms and methods of sea wave energy capture are discussed. Further several most important sea wave energy conversion prototypes...
Low Voltage Ride Through (LVRT) technology of Doubly Fed Wind-Power Induction Generator (DFIG) is a very important issue for grid-connection of wind power system. The paper analyzed and simulated dynamic response of DFIG under gird voltage dip. Aiming at this problem, the paper proposed a whole set of LVRT control strategies for DFIG and designed a control logic diagram for the above strategies. In...
The low-voltage ride-through (LVRT) capability of a MW-Level variable speed wind turbine with a permanent magnet synchronous generator (PMSG) is investigated. A new control scheme for the wind turbine that allows it to be connected to the grid during transient gird faults is designed and simulated. This control scheme emphasizes the regulation of the DC-link voltage. The simulation study of the wind...
Nowadays, there is a tendency to increase the power of wind turbines. Multilevel converter is a realistic alternative in such high power applications. As the most widely used variably speed wind turbine, doubly fed induction generators (DFIG) are very sensitive to grid disturbances. Moreover, grid codes have been revised to require wind turbines to provide Low Voltage Ride-Through (LVRT) ability....
Doubly-fed induction generator (DFIG), as a wind generator, is economically justified, but control of the machine is difficult. In addition, it is significantly difficult to assure continuous operation of the DFIG during and after line-voltage distortions, as required by grid code. Nowadays, there is no single used method; the problem is not entirely solved. In the paper, not only features of the...
In this paper, two three-phase three-level neutral point clamped (NPC) converters connected back-to-back are used for a direct drive wind power generator. A permanent magnet synchronous generator (PMSG) is used as the generator, which is driven by the wind turbine. Main problem of voltage unbalance in each electrolyte capacitor is controlled by using a simple chopper control circuit. A simple hardware...
A simple type A three-phase voltage sag generator with programmable is proposed for testing equipment, small or medium-power application, such as adjustable-speed drives (ASDs), contactors, relays, programmable logic-controller (PLC), and personal computers (PCs), etc. The generating system consists of a 1-kVA synchronous generator, a phase-control ac-dc converter, a mechanical prime-mover. Additional...
The control strategy for directly driven wind turbine with permanent magnet synchronous generator (D-PMSG) was investigated to enhance its capability of low voltage ride through (LVRT). The positive and negative sequence components were detected by instantaneous symmetrical components method on grid voltage. Based on analyzing the impact of grid asymmetrical voltage dip on D-PMSG, the grid positive...
A model of the directly driven wind turbine with permanent magnet synchronous generator (D-PMSG) was described in this paper. The D-PMSG was connected to a host AC power grid by a full scale power converter system which comprised two back-to-back PWM voltage source converters (VSCs) and a common DC-link. Active and reactive power of the two VSCs were controlled independently by employing PI current...
In order to reduce the current of each IGBT and reduce the harmonic current into the grid, a multiple AC-DC-AC full-scale converter which is suitable for high power direct drive wind power generation systems is adopted. The reasons of DC-link voltage fluctuation of the grid connected converter are analyzed. An improved DC-link voltage control method for multiple grid connected converter in direct...
In this paper, the low voltage ride-through (LVRT) capabilities of an hybrid wind plant is studied. The hybrid wind plant considered combines fixed speed wind turbines (FSWTs) based on classical induction generator and full power converter variable speed wind turbines (VSWTs) with permanent magnet generator. However, it must be able to respect grid code requirements. A specific control of the variable...
The paper presents a small Wind Turbine System (WTS) improved with voltage compensation functionality. In the WTS the Permanent Magnet Generator (PMG) control is designed to maximize the power output and achieve a smooth torque and power profile. The grid-side converter is controlled in order to maintain constant the voltage for local loads also in presence of grid voltage variations. The proposed...
The paper presents detailed simulation based analysis and investigation on grid code compliance of a new configuration of a 2 MW doubly fed induction generator. The converters of DFIG are connected and controlled to function like a unified power quality conditioner (UPQC). One of the converters is connected in series with the stator terminals and acts to maintain the stator voltage at a predetermined...
The increasing penetration level of wind farms in power system network requires better understanding of short-term voltage stability and ride through capability before their interconnection to grid. The future wind turbines must stay connected irrespective of any type of disturbance in grid. To achieve reliable operation and control, the wind turbines must be actively controlled in order to meet the...
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