Possible Operation Modes of Moldovan, Ukrainian and Romanian Electrical Power Systems Joint Work

Types of intersystem controlled tie-lines, that may allow the joint work of power systems of Moldova, Ukraine and Romania, are proposed in this paper. The use of intersystem controlled ac transmission lines based on compact one-circuit overhead transmission lines (OHTL) and two-circuit controlled self-compensated OHTL (CSCTL) with phase-shifting transformers on the other hand is also stated. Two types of phase-shifting transformers are considered: the first one – with bounded range of phase angle control between the voltage vectors’ system at the output with respect to the other at the input; the second one – with circular rotation of one voltage vectors’ system with respect to the other. The first type of devices is aimed to control the power flows within the system or through the intersystem tie-lines of synchronously operating systems. The second type of phase-shifting transformers is aimed to interconnect power systems that operate non-synchronously and to control the power flows between them through connecting OHTL. The first type of devices was introduced in calculation model in 330 kV Moldavskaya GRES – Chisinau OHTL and the second one – in the OHTL that are connecting the power systems of Moldova and Romania. The dependences of power flows through power system’s and intersystems’ OHTL are established on base of performed calculations, research and analysis.