Field tests in the Ílhavo Municipal Swimming-Pool on transfer between grid connected and islanding modes Introduction Study case description 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. 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 EDP’s 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 Ílhavo Municipal Swimming-Pool 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 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 microturbine’s frequency protections. Operation in islanding mode requires control of microsources and loads. Based on these concepts, EDP, with some partners like INESC Porto, has been developing a global project named InovGrid. Impact of the microturbine on the LV grid Microturbine starting and parallel with a Diesel gen-set 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. 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. Microturbine output power and grid voltage Microturbine in/output current during attempts to parallel with Diesel gen-set 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. Frequency variations during attempts to parallel with Diesel gen-set Parameters identification of the mathematical model used to represent the microturbine dynamic behaviour Active power during connection of MSP loads • 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. Voltage variations due to load connections • Results: Frequency variations due to load connections Nuno Melo [email protected] António Cardoso [email protected] Flávio Cação [email protected] EDP Distribuição Rua do Túnel, Alto de S. João 3030-006 Coimbra Portugal www.edpdistribuicao.pt Fernanda Resende [email protected] André Madureira [email protected] INESC Porto FEUP campus Rua Dr. Roberto Frias, 378 4200-465 Porto Portugal www.inescporto.pt 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.