A hierarchical physical model-based approach to predictive control of a thermal power plant for efficient plant-wide disturbance rejection

Extending the work presented in Prasad et al. (IEEE Proceedings on Control Theory and Applications, 147, 523-37, 2000), this paper reports a hierarchical nonlinear physical model-based control strategy to account for the problems arising due to complex dynamics of drum level and governor valve, and demonstrates its effectiveness in plant-wide disturbance handling. The strategy incorporates a two-level control structure consisting of lower-level conventional PI regulators and a higher-level nonlinear physical model predictive controller (NPMPC) for mainly set-point manoeuvring. The lower-level PI loops help stabilise the unstable drum-boiler dynamics and allow faster governor valve action for power and grid-frequency regulation. The higher-level NPMPC provides an optimal load demand (or set-point) transition by effective handling of plant-wide interactions and system disturbances. The strategy has been tested in a simulation of a 200-MW oil-fired power plant at Ballylumford in Northern Ireland. A novel approach is devized to test the disturbance rejection capability in severe operating conditions. Low frequency disturbances were created by making random changes in radiation heat flow on the boiler-side, while condenser vacuum was fluctuating in a random fashion on the turbine side. In order to simulate high-frequency disturbances, pulse-type load disturbances were made to strike at instants which are not an integral multiple of the NPMPC sampling period. Impressive results have been obtained during both types of system disturbances and extremely high rates of load changes, right across the operating range, These results compared favourably with those from a conventional state-space generalized predictive control (GPC) method designed under similar conditions.

Reflecting the Public Value of Sport: A game of two halves

This article draws on qualitative research that explores the concept of public value in the delivery of sport services by the organization Sport England. The research took place against a backdrop of shifting priorities following the award of the 2012 Olympic Games to London. It highlights the difficulties that exist in measuring the qualitative nature of the public value of sport and suggests there is a need to understand better the idea. Research with organizations involved alongside Sport England in the delivery of sport is described. This explores the potential to create a public value vision, how to measure it and how to focus public value on delivery beyond the aim of ‘sport for sports sake’ and more towards ‘sport for the greater good’. The article argues that this represents a game of ‘two halves’ in which the first half focuses on 2012 with the second half concerned with its legacy.