Active stabilisation of an HVDC distribution system with multiple constant power loads

The active stabilisation of an HVDC distribution system with multiple constant power loads is presented. Each constant power load comprises a separate motor drive including the torque and speed control functions. By adding a simple admittance compensating controller to the current control loop of the constant power loads, the loads, and therefore the HVDC distribution system, are stabilised. Small-signal analysis techniques are used to form a basis for the design of the active stabilising controllers. Root locus plots are used to examine the system poles as the active and passive damping parameters are adjusted. First, a single motor drive and input filter is examined, then the source output filter is included and finally a second motor drive and input filter is added. The performance of the final design is verified through detailed Saber simulations of the HVDC distribution system.