Wide-area monitoring and control of future smart grids

Application of wide-area monitoring and control for future smart grids with substantial wind penetration and advanced network control options through FACTS and HVDC (both point-to-point and multi-terminal) is the subject matter of this thesis. For wide-area monitoring, a novel technique is proposed to characterize the system dynamic response in near real-time in terms of not only damping and frequency but also mode-shape, the latter being critical for corrective control action. Real-time simulation in Opal-RT is carried out to illustrate the effectiveness and practical feasibility of the proposed approach. Potential problem with wide-area closed-loop continuous control using FACTS devices due to continuously time-varying latency is addressed through the proposed modification of the traditional phasor POD concept introduced by ABB. Adverse impact of limited bandwidth availability due to networked communication is established and a solution using an observer at the PMU location has been demonstrated. Impact of wind penetration on the system dynamic performance has been analyzed along with effectiveness of damping control through proper coordination of wind farms and HVDC links. For multi-terminal HVDC (MTDC) grids the critical issue of autonomous power sharing among the converter stations following a contingency (e.g. converter outage) is addressed. Use of a power-voltage droop in the DC link voltage control loops using remote voltage feedback is shown to yield proper distribution of power mismatch according to the converter ratings while use of local voltages turns out to be unsatisfactory. A novel scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is also studied. The effectiveness of the proposed approaches is illustrated through detailed frequency domain analysis and extensive time-domain simulation results on different test systems

Wide-Area Power Oscillation Damping Control (POD) in Nordic Equivalent System

Abstract A study is presented on power oscillation damping control (POD) using wide area measurements applied to a single static var compensator (SVC). An equivalent power system model representing key characteristics of the Nordic power system is used. Feedback signals from remote phasor measurment units (PMUs) in Norway and Finland are used to damp the critical inter-area modes through a large SVC unit located in south-east Norway. A comparison between two control design approaches -(i) model based POD (MBPOD) -dependant on accurate system model and (ii) indirect adaptive POD (IAPOD) -which relies only on measurements -is made. For MBPOD an optimization approach is used to obtain the parameters of the controller while the IAPOD is based on online Kalman filter estimation and adaptive pole-shifting control. It is shown that the IAPOD yields almost similar performance as the MBPOD with very little prior information about the system. The performance comparison is verified for several tie-line outages

Stability Analysis of VSC MTDC Grids Connected to Multi-machine AC Systems

Abstract-Interaction between multi-machine AC systems and a multi-terminal DC (MTDC) grid and the impact on the overall stability of the combined AC-MTDC system is studied in this paper. A generic modeling framework for VSC-based MTDC grids which is compatible with standard multi-machine AC system models is developed to carry out modal analysis and transient simulation

An Interleaved Soft Switched High Step-Up Boost Converter With High Power Density for Renewable Energy Applications

In this article, a novel soft switched interleaved boost structure with a simple auxiliary circuit is proposed which is suitable for stand-alone loads or ac grid applications. In this topology, coupled inductors and switched capacitor cells of parallel modules are merged to obtain high voltage conversion ratio. The converter also has the capability of adding extra switched capacitor cells to attain very high voltage gain. To provide soft-switching condition in the wide range of output power, a new zero-voltage transition auxiliary circuit is employed which is responsible for soft switching of both phases and benefits from low conduction losses, the minimum number of semiconductor elements, and only one auxiliary gate-driver. These merits provide very high efficiency at both full-load and light loads. More importantly, no auxiliary magnetic components are utilized by taking advantage of the leakage inductance of coupled inductors for the resonant network. All semiconductor components operate under soft switching alleviating the reverse recovery problem and switching losses. Besides, the converter benefits from common ground between input and output which simplify voltage feedback. The experimental results of the interleaved converter prototype with 400-V output voltage at 400 W and 100 kHz switching frequency are provided. The full load efficiency of 98% was achieved and the power density was observed 1.9 W/Cm3