This paper is focused on problems of power quality in systems with varying frequency, equipped with passive harmonics filter. Main differences between the ship system and land network have been pointed out. Influence of varying frequency on proper work of harmonic passive filters frequency change was presented. Simulation circuit and simulations results of theoretical research have been described. Especially influence of frequency on proper work of 5th and 7th harmonic filters was commented on.
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The paper presents the single phase uninterruptible power supply (UPS) system with galvanic separated DC-AC-DC-AC converters operating in parallel. The CAN physical layer based system of communication between converters has been developed and applied, which allow to utilize a decentralized master-slave control providing high availability factor of the whole UPS system. The control system of particular converters has been developed to ensure a high quality of the output voltage for both linear and nonlinear load.Read full article
In the context of renewable energy, this study treats the case of the conversion of photovoltaic and wind energy, which are parts of non pollutant energy, to electrical one in order to create a local archive. Annual data of delivered power are therefore given. In addition, the efficiency of each conversion system is calculated. Finally, the cost of solar and wind power plants are discussed and compared.
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Dynamic Voltage Restorer (DVR) is a custom power device that is used to compensate voltage sag. The DVR generally consists of voltage source inverter (VSI), injection transformers, passive filters and energy storage (battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching the inverters. The inverters are switched using Space Vector Pulse Width Modulation pulses (SVPWM) to maximize the usage of DC link voltage.Read full article
Driving rural development
Hydroelectric generation in China is not limited only to huge scale projects. In recent years, the country has become one of the most successful adopters of small hydroelectric facilities (plants up to 25 MW) as a means of achieving carbon emission free rural development.
The total installed capacity of small hydroelectric plants in China is estimated at approximately 50,000 MW and growing at about 6,000 MW annually.Read full article
This paper is presented by Chilectra, a subsidiary of the Endesa Group Spain and the biggest electric utility in Chile. It sets out a methodology for estimating and determining control parameters for the voltage quality to be delivered to its end customers.Read full article
Analyses to have a quantitative idea of the real behavior of Switching Power Supply (SPS) units from the point of view of waveform distortion and power absorption are developed. Results of several experimental tests performed by means of a test system built up at Laboratories of the Second University of Naples (Italy) are firstly reported.Read full article
Based on the single-line equivalent system of a radial distribution network, two simple methods to evaluate two efficient voltage collapse proximity indicators are presented and discussed. The two methods differ on the determination of the parameters which define the equivalent system from which the indicators are derived.Read full article
The paper presents capabilities of DSTATCOM systems used to improve power quality (PQ) in low voltage (LV) grids with distributed energy resources (DERs). For the case study a typical rural network has been selected in which, on one hand DER installing is the most probable and on the other hand, integration process may cause the biggest problems. Selected single-phase DERs of varying power are connected into the network which introduce PQ disturbances such as voltage variations, harmonics and asymmetry.Read full article
Analyse of harmonic distortion in power systems consists in the determination of steady state quantities for each harmonic component at a time. The existing theoretical relationships are difficult to be implemented in complex systems containing many elements, in various combinations. In the case of radial power systems operated in sinusoidal conditions, the load flow calculation can be performed using a particular method known as the backward/forward sweep.Read full article