Tuning of digital control system for 350 MW coal-fired unit for improved controllability and pick-up performance

Unit 7 nominally rated at 350 MW is one of the coal-fired generating units installed in the Lamma power station of The Hong Kong Electric Company Ltd. (HEC). This is the first unit in HEC to adopt boiler turbine coordinated control mode (CC) whereas all previous units employed boiler following turbine mode (BF). However, Unit 7 is required to meet severe step and ramp pick-up performance and with stringent environmental emission limits. During commissioning, the unit operating under the CC mode encountered many control problems such as excessive pressure and temperature fluctuations and failed to meet the guaranteed load pickup requirements. This paper describes how HEC tackled the control problems to achieve fine controllability with the aid of a digital control system