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A novel microgrid emulator used to test multiple microgrid configurations and energy management control strategies is presented. The system includes Hardware-In-the-Loop (HIL) emulators for geothermal and biogas energy sources. It also includes actual photovoltaic energy together with a lead acid battery bank for storage and it is controlled by a two level control system. The control system consists of a primary level voltage-reactive power and frequency-active power and a secondary level energy management algorithm based on the balance between the power produced by the renewable energy generators, state of charge of the battery bank and the loads. The energy management control strategy is based on cycle-charging the batteries at a reference value in order to efficiently use the available resources. The primary energy source is considered the geothermal energy, while the most cost effective one is the photovoltaic energy. A buffer zone is kept in the battery bank in order to store as much energy produced by the photovoltaic system as possible. The presented microgrid, used for testing the energy management strategies, employs emulators for the geothermal and biogas generators; however, the results are relevant and can be scaled for a real-life microgrid.Keywords: microgrid, power management, renewable energies, two level control, cycle charge control. Auxiliary equipment and communicationA method to send the commands to the microgrid and to measure the process variables from the microgrid is needed for the control algorithm based on battery cycle charging implementation. A bidirectional three wire RS485 serial communication network is built for this purpose. The communication protocol used in the network uses Modbus compatible data frameworks but is also compatible with the data protocols used by the inverters. Beside the communication modules needed by the inverters, there is a need for other equipment in order to give the geothermal and biomass emulators communication capabilities. The command signals are fed to the emulators through Modbus to analog converters and Modbus output compatible power meters are used for the electrical measurement. The network communication master is the central computing unit. The program that implements the master's communication functions and the cycle charging battery management algorithm is written in ANSI C, thus being highly portable. The physical interface between the network and the master is made by an USB to RS-485 interface. The connections of the equipment are presented in Fig. 22. The set points for the SMA equipment are directly sent through the communication network, but the emulators need Modbus to analog transducers for their commands.

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