HVDC Devices Research Articles

Computation of the controllable swing mode spectrum of FACTS and HVDC in large power systems

This paper presents computation of swing modes of a large power system that could be significantly affected by power swing damping controllers in FACTS or HVDC devices at a given location. Modal controllability is a suitable measure to isolate these modes for analysis. Computation of the controllable swing mode spectrum is useful, especially in situations where the controller structure and feedback signals are not frozen (e.g., at the planning stage). This paper proposes two important steps that allow us to map the problem of finding highly controllable swing modes to the problem of finding the swing modes that have high transfer function residues (for which efficient algorithms are available). The steps are: (a) normalization of the eigenvectors corresponding to different modes and (b) identification of specific feedback signals for each type of FACTS/HVDC device such that the modal observability and modal controllability are tightly coupled. Once the mapping is done, a computationally efficient method like the Subspace Accelerated Dominant Pole Algorithm [16] (SADPA) can be adapted to find the highly controllable swing modes. The effectiveness of this approach is demonstrated by case studies of FACTS and HVDC devices in a 16-machine system and the Indian power grid.

Analysis of Sub-Synchronous Oscillation (SSO) Caused by HVDC Transmission System

Sub-synchronous oscillation (SSO) caused by highly non-linear HVDC devices can lead to shaft failure and electrical instability of a turbo-generator at oscillation frequency lower than power grid frequency. With increasing HVDC installed in power systems, analysis of SSO becomes a great concern of electrical engineers. In this paper, the reason and process of the SSO are presented by analyzing equations of the mass-springs model. Research methods of SSO are reviewed in HVDC system. And advantages of digital time-domain simulation are demonstrated through combining with algorithm of Prony.

State Estimation of Electric Power Systems with FACTS and HVDC Devices

In this study, the state estimation of electric power systems which contain FACTS and HVDC devices is investigated. A detailed steady-state model for the Unified Power Flow Controller (UPFC), the most general power flow controller, is formulated and implemented. The model is specified by the steady-state model parameters, such as voltage magnitudes and phase angles for the parallel and the series branches, and reactances associated with the parallel and the series transformers. The DC side HVDC bus net injections are assumed to be measured and error-free for the state estimation of HVDC. In order to include the new devices in the system, formulations of the state estimation algorithm are modified. Simulations of the test system are presented to demonstrate the use of the developed program. Test results show that the developed solution algorithms and formulations for the FACTS and HVDC devices are valid and effective.