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With the emission reduction scheme introduced, increasing number of wind farms have been planned and/or installed in many countries. In this paper, issues with wind power connection to the existing power grid are discussed, with particular emphasize on system operations and planning aspects. In addition to power system analysis, implications of wind power impacts on the electricity market operations...
Current grid codes require the fault ride-through capability of modern wind turbines. During grid faults the reactive current control of the wind turbines should be used to support the grid voltage. With modern protection devices the fault durations are normally in a range of some hundred milliseconds or less. However this time window may be decisive for the stability of the conventional generators...
Microgrids can be viewed as a group of Distributed Generation (DG) units with the capability of operating connected or isolated from the main grid. Most of the work conducted in the area of microgrids focused on developing new control schemes that can maintain the voltage and frequency within standard limits during grid connected and islanded mode of operation. An issue of equal importance is the...
This paper addresses the possibilities to exchange primary reserves within a multi-terminal HVDC (MTDC grid) system as well as between asynchronous ac grids connected through the DC grid. We propose a new method for the challenge of frequency control participation in ac grids connected by a multi-terminal HVDC system. Since HVDC transmission is very often used to exchange a contracted amount of bulk...
The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. To decrease this voltage unbalance problem three-phase four-wire inverter-connected distributed generation units may be used. In this paper, the influence of the control strategy of three-phase...
As wind power achieves higher penetration levels and becomes a more and more substantial portion of our electric energy supply, more stringent requirements are being placed on wind plants. As wind plants displace traditional synchronous generators in terms of percentages, the wind plants must also do their part to maintain stability and reliability of the power system. Modern power electronics are...
The penetration level of wind power into the power system over the world have been increasing very fast in the last few years and is still keeping the fast growth rate. It is just a matter of time that the wind power will be comparable to the conventional power generation. Therefore, many transmission system operators (TSOs) over the world have come up the grid codes to request the wind power plants...
This paper presents a voltage-power droop/frequency-reactive power boost (VPD/FQB) control scheme that allows multiple voltage source converters (VSCs) to operate in parallel in a VSC fed microgrid. Each current controlled VSC in such a microgrid has its own VPD/FQB controller that sets its current references to regulate the voltage and frequency of a common microgrid bus. By drooping the voltage...
The Distributed Power Flow Controller (DPFC) is a new device within the FACTS family. It is emerged from the UPFC and has relatively low cost and a high reliability. The DPFC consists of two types of converters that are in shunt and series connected to grids. The common dc link between the shunt and the series converters is eliminated. The active power exchange between the shunt and series converters...
Due to growing competition in the electricity market, the drive for efficient, stable and secure grid operation makes voltage control in the transmission grid relevant. A solution that has potential is to increase the effectiveness of the ancillary service by automatic fast control. The paper describes a Wide Area Voltage Regulation (V-WAR) that fits this framework. V-WAR is based on Secondary and...
Large-scale permanent magnet generators with full power electronic converters are of increasing interest to many wind turbine manufacturers. These systems offer an efficient and reliable solution for offshore and low wind sites. However, the advantages of these generators necessitate a system design approach when selecting a power electronic drive and designing to meet the toughest grid code elements...
This paper deals with the use of large-size Photovoltaic (PV) units as providers of the reactive power compensation ancillary service. To do this, a suitable control scheme has been developed, which is based on an advanced control theory, called FeedBack Linearization (FBL), widely employed in the robotics field but still not so popular in power systems engineering. This allows to regulate both the...
This paper presents a general model of dual infeed HVDC system applying VSC-HVDC, which can be used as an element in large multi infeed HVDC system. The model may have different structure under different grid faults because of the action of breakers. Hence power flow of the system based on this model is analyzed under steady state and different kinds of grid fault transient situations. Two main control...
The dynamic behaviour of a PWM voltage source inverter based voltage generator with an output LC filter is analyzed in this paper. This converter is able to participate to frequency regulation either in connected mode or in an islanded mode with minor modifications in the control algorithm. Thanks to a droop control, it is possible to achieve power sharing between this converter and a classical synchronous...
This paper proposes a grid-tied power conditioning system for the fuel cell, which consists of a three-phase current-fed dc-dc converter and a 3-phase inverter. The three-phase current-fed dc-dc converter boosts the fuel cell voltage of 26-48V up to 400V, using the zero voltage switching and three-phase DC power transfer capability. The operation of proposed power conditioning system was verified...
In order to improve the efficiency of photovoltaic (PV) systems and to extend the application of PV power generation, a new architecture to connect the solar plant to the grid suitable for large PV plant is proposed discussing benefits and drawbacks respect to the other usually adopted architectures. Furthermore an EMTP-ATP model is developed to analyze the transient and steady state behavior of the...
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