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Switched capacitors at wind farms employing fixed speed induction generators are intended to provide reactive power support to control and maintain the voltage at the point of common coupling (PCC) within acceptable operational values. Malfunction of the capacitor switching control may lead to voltage depression and, subsequently, to tripping of turbines which could create additional transient power...
This paper presents a study about the impact of different inverter interface controls on the steady-state stability of inverter-based distributed generators (DG) in the presence of positive feedback anti-islanding schemes. The impact of the constant power controller and the constant current controller on the DG system steady-state stability is compared. The Sandia frequency shift (SFS) anti-islanding...
This paper provides an assessment of wind power effects on technical and economic performance of today's electric power systems. While a small penetration of wind power is unlikely to cause any qualitative changes, significant deployment of wind-generated power will require a major rethinking of generation dispatch and automatic generation control, in particular. We summarize technical risks, as well...
This paper presents a two prong approach to the validation of the cell controller being developed for advanced grid management in the presence of significant renewable and distributed generation embedded within distribution networks. A laboratory with configurable distributed generation sources, utility load simulators, wind turbine simulators, and high speed frequency and voltage compensators is...
In the paper multiterminal voltage source converter based HVDC (VSC-HVDC) is proposed to interconnect wind farms to AC grids. The method highlights the control at the level of wind generator cluster that comprises several permanent magnet synchronous generators without the primary converters on themselves. For the cluster control, active and reactive power decoupling scheme is applied to adjust the...
An improved nonlinear control strategy is proposed in this paper. The main improvement made by the authors to the traditional nonlinear control which is based on the differential geometric theory is that an appropriate output function is selected to introduce a nonlinear transformation. Although, such transformation can only partially linearize the nonlinear system, it does provide a way to realize...
Distributed generation, or DG, involves utilization of small generators that are distributed in a power network, to supply the electric power demands of utility customers. This paper presents the analysis of droop based generation control schemes for DG inverters comprising of active power-frequency and reactive power-voltage controllers. This enables decentralized operation with load sharing in a...
This paper presents a voltage control methodology that provides a doubly-fed induction generator (DFIG)-based wind farm with the capability to provide voltage regulation. The controller manipulates dynamically the reactive power from the voltage source converter (VSC) to control the voltage at a specified location. Since a proportional-plus-integral (PI) controller is popularly used in power systems,...
The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbine model and a drive train model. The drive train model uses one-mass model to represent the mechanical characteristics of the generator set. The generator model is established in the...
This paper introduces concept of decoupled power controller for tracking load demand of an inverter-interfaced distributed generation (DG) system. The approach suggested in the paper uses reference frame theory to decouple quadrature axis and direct axis currents. As compared to the power-frequency droop based controller, the proposed controller design involves exact mathematical formulation in terms...
In recent years, many kinds of dispersed generations (DGs) have been introduced to distribution networks. The number of these DGs is expected to increase in the near future. In the present distribution network situation, the magnitude of voltage drops can be predicted to some extent because the directions of power flows are always one way from generators to loads. However, when DGs are connected in...
Grid interface of renewable energy based distributed generation requires satisfying the interconnection requirements stipulated by the local distribution utility. Detailed testing of protection and control systems is required to ensure conformity to wide ranging interconnection requirements such as fault ride through capability, protection against islanding, harmonics and voltage flicker limits. Electromagnetic...
In the deregulated power system environment, to maintain system security and power quality, ancillary services are obtained by the system operator in the ancillary service markets. Automatic generation control (AGC) is procured as an ancillary service in the electricity markets. On the other hand, with the development of new generation technologies, distributed generations (DGs) have been widely used...
This paper introduces the power quality issues of wind power installations in a historic perspective, as the development from a few small wind turbines connected directly to the low voltage grid, to the present system with high penetration on the medium voltage distribution grids and two large offshore wind farms connected at transmission level. In this perspective, the power quality issues are divided...
As the penetration level of the distributed generations on distribution network will increase, they must take their share of responsibility in the system security and provide flexibility and controllability necessary to support secure system operation. However, following the occurrence of large disturbances on the network (short-circuits, line outage, voltage dips...) the protective disconnection...
In recent years, distributed generation, as clean natural energy generation and cogeneration system of high thermal efficiency, has increased due to the problems of global warming and exhaustion of fossil fuels. Many of the distributed generations are set up in the vicinity of the customer, and there is the advantage that this decreases transmission losses. However, output of natural energy power...
The changing paradigm of electricity supply industry brings the power industry not only the benefits of economy and efficiency, but the challenges to the operation of the traditional power system control centers (called SCADA/EMS), which were built to automate control functions in electric utilities. The requirement needs the support of the new generation control centers, which should be more decentralized,...
Within more than 20 years of intensive research and development the wind industry has recently superseded the 3 MW size of machines successfully that have been in operation in the early 80th already. Interestingly the industry has realized that the basic electrical concept of these early day machines was very reasonable. Based now on a very solid background of operational experience with wind turbine...
In this paper a digital load relief scheme is presented which, when combined with a variable-gain fuzzy logic control strategy, gives significant improvement in diesel generating set load acceptance performance. Test results are presented demonstrating that a commercially available analogue load adjustment implementation can yield improvement in minimization of engine speed deviation for large real...
In this paper, a dynamic model of the solid-oxide fuel cell (SOFC) power unit is developed for the purpose of designing a controller to regulate fuel flow rate, fuel temperature, air flow rate, and air temperature to maintain the SOFC stack temperature, fuel utilization rate, and voltage within operation limits. A lumped model is used to consider the thermal dynamics and the electro-chemical dynamics...
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