Output filter design and control system implementation for a three phase AC grid emulator

The spread of hybrid and electric vehicles is leading to the development of increasingly efficient and compact Onboard Chargers (OBCs). These devices are essential for the power transfer from the grid to the battery and vice versa. Testing is a crucial aspect of the development of such components. Grid emulators are conceived to fulfil the need of testing grid connected converters like OBCs under several circumstances. Stability analysis or validation of proper functioning under grid disturbances are examples of tests. The goal of the thesis is to design the hardware and the software components of a grid emulator with the purpose of testing a 22 kW Onboard Charger which can also achieve bidirectional power flow. In the thesis work, the analysis of a performing control system as well as a proper filter design is carried out. A normative documentation regarding harmonic compatibility is reviewed and considered as a guide for the design of the hardware. An existing two-level converter is selected to emulate the grid characteristics and deliver up to the full power required by the Device Under Test (DUT). The hardware design is mostly focused on the output filter of the converter. For this purpose, the equivalent impedance is examined to accurately emulate the grid. Different control methods are assessed to identify the most appropriate one for the application and a specific C-code is created. A research of the components is carried out to develop the filter stage. Those most suitable for the application are chosen. A series of tests is conceived in order to validate the correct functioning of the grid emulator. The device is simulated in a Simulink environment before being realized on a physical testbench. To end with, an experimental setup is performed to test the system. In particular, specific Key Performance Indexes (KPIs) are defined to validate the filter performances and the control. These parameters mainly refer to the capability of the grid emulator to represent a grid poor of harmonic content due to the inverter modulation.