Field tests in the Ílhavo Municipal Swimming-Pool on transfer between grid connected and islanding modes Results: Field tests demonstrated the feasibility of transitions between grid connected and islanding modes. Regarding to this study case, considering the good level of short-circuit power and the reduced length between the distribution transformer and the microturbine, the impact of the microturbine on the grid power quality was not significant. The operation of the microturbine in islanding mode was possible without significant voltage and frequency variation for moderate load variations. Parallel of the microturbine with the Diesel gen-set and a stable operation, for several load and generation regimens, were achieved with slacken of the microturbines frequency protections. Operation in islanding mode requires control of micro- sources and loads. Based on these concepts, EDP, with some partners like INESC Porto, has been developing a global project named InovGrid. Introduction The increasing penetration of microgeneration on Low Voltage (LV) distribution grids and the implementation of microgrids require a detailed analysis of the behaviour of micro-sources and loads in grid connected and islanding modes, as well as during transitions between both modes. On the portuguese field tests, EDP Distribuição (EDP) analysed the behaviour of a microturbine installed in the Ílhavo Municipal Swimming-Pool (MSP), supplying the local load in islanding mode and exporting power in grid connected mode. The interaction between this microturbine and a Diesel gen-set was also analysed in islanding mode. Ílhavo Municipal Swimming-Pool Study case description The field tests were developed in the first portuguese application of a microturbine in a MSP. It is characterized by a micro-CHP system for water heating and electric power generation, with connection to the EDPs LV grid. The microturbine has capacity to generate 60kW electrical power and 120kW thermal power. The main loads of the MSP are characterized by: Air treatment units, which include basically 2 fans (induction motors) each one; Air conditioning systems; Water pumps, that support the swimming-pool hydraulic circuits; Indoor and outdoor lighting. Main objective To demonstrate the feasibility of transferring microturbine and MSP loads from grid connected to islanding mode under various operating conditions. This includes transferring in several load and generation regimens and the necessary load control. Single-line diagram of connections between LV grid, MSP load, microturbine and Diesel gen-set during field tests

Nuno Melo António Cardoso Flávio Cação EDP Distribuição Rua do Túnel, Alto de S. João Coimbra Portugal Fernanda Resende André Madureira INESC Porto FEUP campus Rua Dr. Roberto Frias, Porto Portugal Acknowledgments The authors would like to express their thanks to the Ílhavo Town Council (Fernando Caçoilo and Augusto Nunes) and to António Pintor for their support and contributions to these field tests. Impact of the microturbine on the LV grid Starting of the microturbine and power decreasing/increasing (5kW steps) in grid connected mode. This test was performed in order to analyse the impact of the microturbine on the grid voltage and to identify its simulation parameters. Operation of the microturbine in islanding mode Connection of several MSP loads, fans and water pumps with rated power of 4kW, 5kW and 7.5kW, to analyse the voltage and frequency stability of the system in islanding mode. Microturbine starting and parallel with a Diesel gen-set The first two attempts to parallel the microturbine with the Diesel gen-set failed by over frequency tripping. The settings of the frequency protections of the microturbine were changed, from 50.5Hz to 51.5Hz, in order to allow the parallel. Parameters identification of the mathematical model used to represent the microturbine dynamic behaviour Parameters estimation based on experimental data: - Parameterization of the microturbine mathematical model and its control systems; - Parameters identification: - Evolutionary particle swarm optimization; - Mean square error criterion. Results: Microturbine output power and grid voltage Active power during connection of MSP loads Voltage variations due to load connections Frequency variations due to load connections Microturbine in/output current during attempts to parallel with Diesel gen-set Frequency variations during attempts to parallel with Diesel gen-set