This paper presents a contribution to the solution of the power flow problem with HVDC by using a free access tool to its code. For this purpose, it was proposed to use the wellknown MATPOWER tool to incorporate HVDC. The original program only allows AC networks implementations. To include HVDC, the Newton-Raphson Fast Decoupled (NRFD) method was used to solve the AC network. The calculation methodology consists of alternating iterations between AC network procedures (MATPOWER standard) and DC network iterations. The proposed tool addresses DC links in normal control mode and power or current control operation mode in the rectifier. For its validation, simulations were carried out using an equivalent network of the HVDC system associated with the Itaipu power station (50Hz/60Hz), with 9 AC buses and 4 DC poles. Under the same conditions, similar results were obtained in the simulation with the modification proposed in MATPOWER and the production-grade software ANAREDE