Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids
Abstract
This paper deals with the deployment of a local three-phase four-wire (3P4W) electrical power distributionsystem (EPDS), using a single- to three-phase unified powerquality conditioner (UPQC) topology, called UPQC-1Ph-to-3Ph.The topology is indicated for applications in rural or remoteareas in which, for economic reasons, only EPDS with single wireearth return are accessible to the consumer. Since the use ofthree-phase loads is increasing in these areas, access to a threephasedistribution system becomes preponderant. By adopting adual compensation strategy, the proposed UPQC-1Ph-to-3Ph isable of draining from the single-phase electrical grid a sinusoidalcurrent and in phase with the voltage, resulting high powerfactor. Furthermore, the system is also able to suppress gridvoltage harmonics, as well as to compensate for otherdisturbances, such as voltage sags. Thus, a 3P4W system withregulated, balanced and sinusoidal voltages with low harmoniccontents is provided for single- and three-phase loads. Ananalysis of the power flow through the series and parallelconverters is performed in order to aid the designing of thepower converters. Experimental results are presented forvalidating the proposal, as well as evaluating the static anddynamic performances of the proposed topology.
EXISTING SYSTEM:
The demand for electrical energy in single-phase ruraldistribution grids has considerably increased in the lastdecades, both in agriculture and in livestock, mainly due to theincreasing evolution and modernization of the technologiesused, as well as the increase in the mechanization ofproduction processes. It is possible to mention, for example,the automation of irrigation, as well as the post-harvestagricultural processing involving seed selection and milling,ventilation and refrigeration, washing and packaging lines,a others. Within this context, there is an imminent trend of increasingenergy demand in rural properties, as well as the need toimprove power quality enhancement due to the change in thecharacteristics of the loads. The voltage regulation is characterized as one of the mainproblems of power quality (PQ) found in the rural singlephasegrids, because when subjected to large loads,these grids have significant voltage drops, whereas at times oflow consumption the voltage tends to rise. Nevertheless, asolution not so efficient due to constant load variations can beadopted by adjusting the taps of the transformer of the SWERnetwork. Another solution, more efficient in this case, is theuse of single-phase voltage regulators. Some ways to bypass large capital investments to meet thegrowing demand of rural properties have been adopted the impacts caused between distributed generationsystems implemented through photovoltaic systems and theSWER distribution systems are presented. On the other hand,in, the use of energy storage systems by means of batteriesand their use at peak demand is discussed.
PROPOSED SYSTEM:
The main contribution presented in this paper is to validateexperimentally the UPQC-1Ph-to-3Ph destined to feed single-and three-phase loads from the SWER power distributionsystems, commonly found in rural and/or remote areas andsuffer with PQ problems. By adopting the dual compensationstrategy, the proposed UPQC-1Ph-to-3Ph makes possible todrain from the single-phase electrical grid a sinusoidal currentin phase with the grid voltage. Furthermore, the system canalso suppress harmonics from the grid voltage, as well ascompensate for voltage disturbances, such as voltagesags/swell. In other words, the UPQC-1Ph-to-3Ph canconceive a local 3P4W system with regulated, balanced andsinusoidal load voltages with low harmonic contentsimproving the PQ indicators. Therefore, the proposedsystem can achieve two important functions simultaneously,as described: i. convert the single-phase grid into a three-phasegrid, generating a 3P4W distribution system with earthedneutral wire to the final consumer, allowing to connect single-and there-phase loads; ii. perform the series and parallel activepower filtering improving PQ indicators, such as power factor,harmonic distortion. Furthermore, in order to assist in theproper dimensioning of the UPQC-1Ph-to-3Ph powerconverters, an analysis involving the power flow through theserial and parallel converters is also presented
CONCLUSION
This paper presented the study and the experimental validation of a local three-phase four-wire power distributionsystem. The system, indicated for applications in rural orremote areas where three-phase distribution grids are notaccessible, was conceived based on unified power qualityconditioner functionalities. With serial and parallel filtering capability, two invertertopologies were used to compose the UPQC-1Ph-to-3Ph.Thereby, the single-phase series converter was deployed usinga half-bridge inverter, while the three-phase parallel converterwas implemented using a 3-Leg split capacitor inverter. Using the dual compensation strategy, the proposed systemwas able of feeding linear and non-linear three-phase loadsacting with universal active filtering capability, i.e., acting asSAPF and PAPF. In addition, a procedure was presented that allows thedimensioning the power structures of the series and parallelconverters, under various operating conditions of the utilitygrid and the load. The good static and dynamic behavior of theUPQC-1Ph-to-3Ph has been proven through extensiveexperimental results.
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