Showing papers by "Matias Diaz published in 2014"

Analysis of synchronous and stationary reference frame control strategies to fulfill LVRT requirements in Wind Energy Conversion Systems

Abstract: In order to avoid stability problems, LVRT requirements (Low Voltage Ride Through) demand Wind Energy Conversion Systems (WECS) to remain connected to the grid in the presence of grid voltages dips. Because 88% of the grid failures are asymmetrical, positive and negative sequence components have to be controlled to fulfill LVRT requirements. This paper present a comparison between synchronous and stationary reference frame control strategies for an active front-end converter of a grid connected WECS working under grid fault conditions. The mathematical analysis and design procedure of both control system are presented in this work. Experimental results obtained from a 3kW prototype are fully discussed in this paper. The experimental implementation is realized using a novel implementation of a voltage sag generator which is based on a 3×4 Matrix Converter.

3-Phase 4-wire matrix converter-based voltage sag/swell generator to test low-voltage ride through in wind energy conversion systems

Abstract: The high penetration of energy from wind energy conversion systems (WECSs) can have a significant influence on the stability, power quality and reliability of power systems. Therefore several countries have developed stringent grid codes in recent years in order to enhance the overall stability of power systems. In these grid codes, the capacity to fulfil low-voltage ride through (LVRT) requirements is considered an important issue for the control of WECSs. Therefore in this study, a novel voltage sag/ swell generator (VSG) based on a 4-leg matrix converter is presented. This VSG can be used to generate the symmetrical and asymmetrical faults required to test LVRT algorithms in a laboratory environment. The performance of the VSG is experimentally demonstrated and compared with the operation of other VSGs conventionally used for LVRT studies.

Dual current control strategy to fulfill LVRT requirements in WECS

Abstract: Purpose – The purpose of this paper is to investigate a control strategy to fulfill low-voltage ride through (LVRT) requirements in wind energy conversion system (WECS). Design/methodology/approach – This paper considers an active front-end converter of a grid connected WECS working under grid fault conditions. Two strategies based on symmetrical components are studied and proposed: the first one considers control only for positive sequence control (PSC); the second one considered a dual controller for positive and negative sequence controller (PNSC). The performance of each strategy is studied on LVRT requirements fulfillment. Findings – This paper shows presents a control strategy based on symmetrical component to keep the operation of grid-connected WECS under unsymmetrical grid fault conditions. Research limitations/implications – This work is being applied to a 2 kVA laboratory prototype. The lab prototype emulates a grid connected WECS. Originality/value – This paper validate the PNSC strategy to LV...

4-wire Matrix Converter based voltage sag/swell generator to test LVRT in renewable energy systems

Abstract: The incorporation of high power rate Wind Energy Conversion Systems (WECS) have significant influence in the stability, power quality and reliability of the electrical grid. Therefore, strict grid codes have been developed during the last years in order to enhance overall stability of the systems. Thereby Low Voltage Ride Through (LVRT) requirements is a key issue for WECS. In order to test the response of WECS under grid-voltage sag conditions, a Voltage Sag Generator (VSG) is needed. This paper presents a novel Matrix Converter based VSG Prototype in order to study the fulfilment of LVRT requirements. Voltage sags/swell of variable magnitude, duration and type can be generated for the proposed VSG without using complex modulation schemes.