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With its new SineFormertrade EPCOS is introducing a fully new output filter technology for frequency converters. In contrast to conventional filter topologies the new SineFormertrade simultaneously converts the phase-to-phase voltage into a sinusoidal signal, damps the common mode currents and also forms the conductor-to-ground voltage to sine shaped voltage. This offers users a number of key benefits...
An alternative method is presented in this paper to identify the harmonic components of non-linear loads in single phase power systems based on artificial neural networks. The components are identified by analyzing the single phase current waveform in time domain in half-cycle of the ac voltage source. The proposed method is compared to the fast Fourier transform. Simulation and experimental results...
Distribution grids are increasingly populated by a variety of renewable energy sources, which create new opportunities in terms of efficient use of energy and can also help to improve power quality. In fact, they are connected to the grid by means of power switching interfaces (PSI) which are capable to control power flow and waveform of absorbed currents as well. They can therefore contribute to...
This paper is focused on active and reactive power consumption and power losses in the consumer power system depending upon supply voltage quality. Supply voltage level deviations from rated voltage affect directly power consumption and power losses in the consumer power system. Active and reactive power relation to supply voltage is characterized by load factors. In the paper a practical method for...
A control algorithm is proposed for a three-phase hybrid power filter constituted by a series active filter and a shunt passive filter. The control strategy is based on the dual formulation of the vectorial theory of electrical power, so that the voltage waveform injected by the active filter is able to compensate the reactive power, to eliminate harmonics of the load current and to balance asymmetrical...
This paper presents a control system based on a repetitive controller to compensate key power-quality disturbances, namely voltage sags, harmonic voltages and voltage imbalances, using a dynamic voltage restorer (DVR). The control scheme deals with all three disturbances simultaneously within a specified bandwidth. The control structure contains a feed-forward term to improve the transient response...
This paper presents a comparison study between the operation of a back-to-back and a matrix converter induction motor drive under the presence of faults in the power switches of these converters. These two topologies are functionally equivalent in terms of input power quality and energy regeneration capabilities but need to be compared in terms of performance under faulty conditions as well due to...
Controlled/uncontrolled rectifiers draw harmonic reach currents from the grid. Harmonic components of the line current affect the grid and other equipment around the point of common coupling. Therefore, so the grid current harmonic distortion levels must be kept at desired level. Multi-pulse rectifiers are commonly used in high power rectifier systems to reduce grid current harmonics and improve power...
Power converters operated in unsymmetrical three-phase electrical systems will generally work asymmetrically. This introduces disadvantages for the operation of the electrical power system, such as non-characteristic harmonics in voltage and current. In this paper, a method is presented to control the behavior of electrical equipment based on line-commutated current converters using unsymmetrical...
The drive system of a variable speed pump-storage power station consisting of a doubly-fed induction machine with a 3-level voltage source inverter feeding the rotor is presented. The advantages of variable speed pump-storage power stations are outlined. After a short comparison with the classical cyclo-converter solution the voltage source inverter solution is described in detail covering various...
Distributed power generation is expected to deliver power into the grid without interruption during voltage dips. To improve system ride-through capabilities, a generalized active power control strategy is proposed for grid-interfacing inverters. Specifically, a current reference generation strategy based on symmetric-sequence components of unbalanced three-phase three-wire or four-wire systems is...
The present paper addresses the control of doubly fed induction generators under unbalanced voltage sags considering the converter limits. A control strategy is proposed by choosing certain current reference values in the positive and negative sequences so that the torque and the DC voltage are kept stable during such unbalanced sags considering the converter limits.
This paper investigates the interactions which arise between grid connected photovoltaic inverter systems and the electrical grid. In particular, it considers the effect of grid voltage harmonics and grid impedance on the current control performance of grid connected inverter systems. In these photovoltaic inverter systems it is usual to control unity power factor, sinusoidal, current into the grid...
This paper deals with shunt active power filtering for power quality improvement under unfavourable non-linear load and source conditions. A simple hybrid control strategy is used, based on a numerical integrator proportional (IP) DC bus controller combined with a phase-locked loop (P.L.L.) output to generate reference currents. A second analogue current controller is developed to insure- three phase...
This paper focuses on the effects of voltage sags, both symmetrical and unsymmetrical, on the three-phase synchronous machine (SM). Voltage sags on SM cause speed variations, current and torque peaks and hence may cause tripping and equipment damage. The consequences of voltage sags on the machine behaviour depend on different factors such as sag's magnitude (or depth), duration, initial point-on-wave...
This paper describes harmonic detection methods used in industrial shunt active filters, designed for adjustable speed drive applications. The methods are based on overall - broadband and selective harmonic detection technique. All methods are described and analyzed in the paper together with several practical design steps. The methods are compared in the case of voltage unbalance and pre distortion,...
This paper presents the design and performance of a test bench to generate grid faults and disturbed grid voltage conditions to test grid connected devices. The test bench is applied to generate different reproducible types of disturbed grid voltages like symmetrical and unbalanced voltage dips, overvoltage, frequency variations and harmonic disturbances. By means of this grid emulator the behavior...
The continuous monitoring of voltage characteristics in electric power systems, such as in grid-connected power converters, is required for power quality assessment and control purposes. This paper presents a fast method to estimate the fundamental frequency of the grid voltage in balanced three-phase systems containing harmonic distortion. The proposed solution is based on a fast algebraic method,...
Cascaded multi-level converters have some noticeable advantages such as high reliability, efficient fault management capability, simple structure, and adaptability with different power levels. Furthermore, these converters could be connected to medium-voltage networks without an isolating transformer. However, the voltage balancing of the DC capacitors is a highly challenging task particularly in...
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