This technology relates to control of multi-terminal power systems. Renewable energy sources are increasingly connected to the power grid in series. In these situations, central control of these sources can be difficult, but it very important for protection of the equipment attached to the string. This technology controls a multi-terminal power system by implementing local control of each of a group of sending terminals in a power system network to behave as a constant-power source such that both output voltage and output current of the sending terminal may simultaneously vary in response to changing external circuit conditions while maintaining constant a product of the output voltage and the output current of the sending terminal.