Hui Zhu

To reduce CO2 emissions requires greater reliance on renewable sources of energy for generating electricity, especially adoption of large-scale wind generation. This study investigates possible approaches and/or policies that increase efficient use of renewable energy and reduce greenhouse gas emissions in a cost effective manner. We develop a constrained optimization model of two electricity systems to identify the impact of increasing wind generating capacity and examine how carbon prices (taxes, allowances) impact the penetration of wind power into the electricity grids. Rather than employ engineering cost functions, marginal cost functions are estimated using hourly offer data from the Alberta Electric System Operator. We determine optimal removal of coal generating facilities as greater levels of wind capacity are installed in an integrated Alberta-BC electricity system; and examine the economic costs and institutional incentives that affect the ability to store intermittent wind-generated power in BC’s hydro reservoirs during low demand. The marginal shadow price of storage is zero, whichindicates that there is more than enough water behind the dams given Alberta’s relatively small demand for storage and limited intertie transmission capacity.

Aiming at the oscillation suppression of spacecraft with large flexible appendages, we propose a control strategy using H∞ control. The weighting functions are designed for the specific flexible modes of the spacecraft and the frequency of harmonic interference in its operating environment. Taking into account the structural uncertainty of systematic modeling and the comprehensive performance requirements of system bandwidth constraint and attitude stability, the H∞ comprehensive performance matrix is constructed. A space telescope with a large flexible solar array is presented as an illustrative example, and a control design that meets the requirement for pointing accuracy is proposed. The simulation results show that the designed controller satisfies the requirements of attitude stability and high pointing accuracy and has effectively suppressed the disturbance of endemic frequency. The design scheme and selection method of the weight function shown in this paper can be a reference for the controller design for oscillation suppression of this type of spacecraft with flexible structures.