Design Procedure of Constant Voltage Regulating System with Differential Cross-current Compensator

Abstract

Recently, continuous parallel running of several generators becomes more popular with expanding development of marine power plants. The cross-current compensator (CCC) is generally applied to suppress wattless cross-current component flows between generators on parallel running. Since the CCC reduces the bus voltage on load, large compensating factor can not be applied to the system. Therefore, in some cases under small compensating factor, parallel running system works showing unstable condition or hunting caused by increasing load.
This paper presents that absolutely stable power system with very small voltage drop can be obtained by using Differential Cross-current Compensator (DCC) by combining Differential Current Transformer (DCT) with large value of Cross-current Compensating Resistance (CCCR) . In other words, this paper makes it clear that the dynamic stability is not affected by DCT and that minimum value of the cross-current compensating ratio can be evaluated from steady state stability, based on the analysis of dynamic and steady state stabilities when DCT is applied in the compensator. The design plans of DCC and the examples of power plant design which show voltage regulation within±1% in both isolated and parallel operations are also described. These power plants are already equipped on many merchant ships and their superiorities are proved well.