Analysis of HVDC light control using conventional decoupled vector control technology

With the advance of power electronic technology, HVDC light transmission based on voltage-source IGBT power converters have been increased rapidly in renewable and electric power system applications. This paper focuses on the analysis of traditional decoupled d-q vector control approaches for control of power transmission in a HVDC light system. The paper presents steady-state and transient models of a HVDC light system in a d-q reference frame. The steady-state model is used to study the steady-state characteristics of the HVDC light under the decoupled d-q vector control strategy. The transient model is used to develop close-loop control mechanisms for control of the HVDC light system. A weakness of traditional control mechanism is analyzed through theoretical study and computer simulation. Close-loop control evaluation illustrates that the conventional HVDC light vector control technique could result in over voltage and oscillations of a HVDC system especially when the controller operates beyond the converter linear modulation limit.