Acceleration Grid Power Supply Conversion System of the MITICA Neutral Beam Injector: On Site Integration Activities and Tests

The Acceleration Grid Power Supply (AGPS) is a system devoted to supply the acceleration grids of the MITICA experiment, the full scale prototype of the ITER Neutral Beam Injector (NBI). The AGPS is a special switching power supply with demanding requirements: high rated power (about 55 MW), extremely high output voltage (-1MV dc), long duration pulses. The procurement of the AGPS is split in two parts: the low voltage conversion system, namely the AGPS-Conversion System (AGPS-CS) and the high voltage DC Generators (AGPS-DCG). The AGPS-CS has been installed and commissioned in between late 2017 and early 2018. The design of the installation engineering has been particularly challenging. Some critical issues concerning the integration with the existing buildings and auxiliary systems were assessed during the installation period. Examples of such issues are the definition of the medium voltage cable layout and interfaces, the design of high current busbars penetrating in the building for compatibility with the prescriptions about fire propagation, the adaptation of the infrastructures to enhance the maintainability of the system. Another important matter has been the assessment of the passive filters needed to damp the voltage oscillation at the end of the cables connecting the AGPS-CS to AGPS-DCG, which were demonstrated to be necessary after the analysis of the cabling layout. Concerning the commissioning and acceptance tests on site, they were performed on a dummy load at reduced power and duty, testing one section of the system at a time, being very difficult to design and realize a test at full rated power. This paper is focused on the installation and commissioning activities, highlighting the peculiar integration aspect of this unique system, above described. Moreover, the results of the site tests are presented, showing the ability of the system to provide the required performance.