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In this article a brief description of a direct conversion receiver is given, sources of affected channels in such a receiver are examined. Practical methods for eliminating of affected channels of a real radio system are proposed.
Most of the large scale photovoltaic power plants (LS-PVPP) count on power converters with a central configuration. Advantages such as robustness, low maintenance and installation cost makes this configuration the preferred specially suitable in large scale systems. However, important drawbacks like the low efficiency level make necessary to develop new solutions for future power plants. In this paper...
With the increasing penetration of renewable energy generations such as solar and wind power, negative impacts of the large-scale integration of renewable energy on the bulk grid cannot be ignored. Thus, grid integration testing of inverter-coupled renewable energy is essential. For this reason, a high power gird simulator capable of emulating various types of realistic grid conditions is needed for...
This paper presents test results of the control of a pole-modulated permanent magnet synchronous generator (PM-PMSG) using a dedicated power conversion system to deliver power from an oscillating, low speed wave energy converter (WEC). Due to the low speed of the WEC, the size of the generator is increased and the machine is designed with large number of poles and concentrated winding. The electromotive...
In an Organic Rankine Cycle (ORC) systems, the Permanent Magnet (PM) generator is directly coupled to high-speed turbine shaft, in order to increase system efficiency avoiding introduction of gear-box. On the other hand, current time harmonics induce high frequency currents in rotor parts, which cause a temperature increase. PMs are strongly affected by the operating temperature, since both remanence...
Power quality of ac bus voltage is a key issue for microgrids. A model-predictive-control (MPC)-based distributed bus voltage compensation methods using inverter-interfaced distributed generators (DGs) connected to the concerned bus is proposed. The presented method can compensate bus voltage unbalance and harmonics and share the compensated current between inverters autonomously, with neither communication...
The paper deals with a high efficiency boost rectifier for high rotational speed Gen-Set applications. It is tailored around a permanent magnet synchronous generator (PMSG) featuring an open end winding configuration. According to such a configuration the generator stator windings are connected on one side to a three level T-type unidirectional rectifier, and on the other side, to an auxiliary two-level...
Synchronous machines exhibit, under normal operating conditions, torque oscillation problems. This work presents a study that proposes a methodology for the reduction of these oscillations. It was tested in a synchronous generator powered environment with DC voltage supplying power to a common bus in permanent regime, this bus has the presence of a nonlinear load. There are oscillating components...
This paper investigates spatial and time harmonics of flux density and radial force distributions in the airgap of a hydrogenerator with fractional-slot windings. Hydrogenerator is connected to a neutral-point-clamped (NPC) converter, representing a converter-fed synchronous machine (CFSM) in pumped-storage hydropower plant. Magnetic field in the hydrogenerator is computed using time-stepping finite...
The paper has as first objective the overview of the active distribution networks for the future, their viability with existing equipment and components. The presented applications are intended for industrial-type networks with local power generation in view of their efficient integration into an intelligent distribution network. The main scientific goal of the paper is to test the stability issues...
Offshore wind farms are growing as a renewable generation system. For long distance power transmission from offshore to mainland, a high voltage direct current (HVDC) system is cost-effective. This paper shows a new modulation technique for the voltage source converter (VSC) of a HVDC output offshore wind farm. It is called a modified trapezoidal modulation (MTM). This technique can greatly reduce...
A novel control strategy for solving unbalanced three-phase load in low voltage power grid is proposed in this paper. The compensating current determined by a new method based on instantaneous voltage vector orientation, which overcomes the shortcomings of phase-locked loops (PLL) in the traditional detection methods. A static var generator (SVG) is employed to compensate the unbalanced current obtained...
This paper examines resonant characteristics of the transmission line compensated with the Static Synchronous Series Compensator. Frequency-domain characteristics of the line impedance are studied to evaluate whether the SSSC can cause electrical resonance in the line, hence the potential to excite subsynchronous resonance (SSR) in neighboring turbine-generator plants. Detailed studies are performed...
The problems associated with the harmonics needs more attention as more number of distributed generators like PV and wind are integrated into a distribution system. Although the integration presents a lot of benefits, satisfying the needs of local load requirements by reducing the line losses and facilitating congestion management, the problems of power quality that impact the distribution system...
Rotor winding interturn short circuit is the main fault of synchronous electric machines, it is of great significance to the safe and stable operation of the machine to discover and handle the fault timely. In view of this, the fault positioning method of rotor turn-to-turn short circuit of synchronous machines was studied. The mathematic expression of exciting magnetomotive force (e-m.m.f.), electromotiveforce...
Aircraft Generator is the core part in aircraft power supply system, and its internal fault can lead to the stator winding asymmetry. Even worse, the asymmetry output power created by the asymmetry winding can damage the aircraft electrical equipment, so it is significant to study the internal electrical fault of aircraft generator. And the study can provide reference for maintenance decision. In...
One of the most critical situations in the operation of medium and low speed synchronous generators appears when they are subjected to torque imbalances. This could be the case of internal combustion engines driven generators. In these engines, torque has a periodic oscillation due to variations in the combustion process and pressure development between cylinders. Consequently, a fuel excess or a...
This paper investigates the flux density and radial force spatial harmonics in large salient pole synchronous hydro-generators. Vibration due to magnetic forces are mainly caused by low order harmonics in the airgap flux density distribution. The influence of winding layout and airgap length on the lowest order radial force component are analysed. Airgap flux density and radial force density distributions...
The eddy current loss (ECL) impacts the stability of high speed permanent magnet synchronous motor (HSPMSM), the high efficiency and temperature of it. This paper analyzes the ECL in rotor by calculation method and separates it by experiment. In all kinds of losses, core loss and coil loss can be separated by traditional calculation method with related parameters being tested actually. Besides, Windage...
The paper addresses the possibilities of application of discrete Short-time Fourier transform (STFT) and Fast Fourier transform (FFT) for detection of voltage dips in the distribution grid with high level of distributed generation in the concept of the future smart grids. Modelling and testing are carried out in the MATLAB/SimPowerSystems environment. Modified IEEE13 bus system with high level of...
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