Development of a 1500Vdc photovoltaic inverter for utility-scale PV power plants

The increase in size of large-scale photovoltaic plants increases the relative impact of ohmic losses in the dc and ac transmission. On the other hand, the amount of strings also increases, along with the number of combiner boxes and related equipment. This results in increased losses and costs that impose a limit to the competitiveness of PV technology for large power plants. PV plants today are rated at 1000V, which is considered low voltage in IEC and ANSI standards, but in fact, the IEC standard covers up to 1500V in the low voltage category. Going to this maximum voltage will allow for a considerable reduction in current, reducing the system losses on the DC side. On the other hand, a longer string can be achieved, reducing the number of combiner boxes and allowing a rise in the ac voltage. This paper presents the development of a 2.3MW inverter with a maximum DC system voltage of 1500V. A neutral point switch type three-level inverter configuration, so-called T-type three-level inverter, is employed for better conversion efficiency. Simulation results confirm the performance of the 1500V rated inverter.