Bumpless transfer with and without controller uncertainty: Resolution of key implementation issues

Bumpless transfer between controllers is an important part of controller benchmarking as well as operation of robust controllers covering the entire operating range of boiler/turbine systems in power plants. In this work, a complete design and implementation methodology for the steady state bumpless controller transfer is presented. Transfer under controller uncertainty as well as without it is considered. For the case without uncertainty, a complete explicit algebraic Linear Quadratic solution is obtained in the form of reinitialization of the offline controller prior to transfer. This eliminates the need for the iterative computation of the offline controller output prior to transfer, solving a key implementation issue. For the transfer under controller uncertainty, it is shown that obtaining the explicit reinitialization is not possible. In this case, the off-line transfer speed-up is formalized to yield an implementation technique that completely eliminates the need for any performance/robustness trade-off in the transfer operator design and provides arbitrarily fast convergence of the off-line controller output to that of the online one, but at the expense of fast iterative calculation. Thus, the paper removes key obstacles in the use of bumpless transfer by practitioners. The performance of a bumpless-transfer-based robust hybrid controller of a boiler/turbine unit using real-time simulator of Unit 9 at TVA is demonstrated. Controller testing on the actual unit is planned for the spring of 2007.