Improved Boiler-Turbine Coordinated Control of CHP Units with Heat Accumulators by Introducing Heat Source Regulation

Abstract

It is significant for power system stability to improve the operation flexibility of grid-connected units. Such improvement has always been a hot topic, especially for coal-fired units. In recent decades, it has become increasingly urgent and challenging as large-scale fluctuant renewable energy is connected to the power grid. Boiler-turbine coordinated control strategy (CCS), which is employed to perform unit load control according to automatic generation control (AGC), has a slow ramp rate in general on account of large delay and inertia of boiler, so to improve the unit operating flexibility, it is necessary to explore usable heat storage and optimize the control strategy. In combined heat and power (CHP) units with heat accumulators, their heat and power are decoupled. Therefore the extraction steam that goes to the heating station can be regulated flexibly even operating in “heat-led mode”. The change of extraction steam flow has a significant influence on the turbine power output, so we propose to improve the load-following capability of CHP units by regulating the heat source flow. In this paper, the influencing model is set up, and it is about heat source flow variations on the electric power output. The load control strategy is further optimized and designed through combinations of CCS and heat source regulation. Finally simulations and analysis are performed on a 330MW CHP unit, and the results reveal that the power ramp rate with our strategy is two times faster than that with traditional strategy.

Operational Flexibility of Combined Heat and Power Plant with Steam Extraction Regulation

“…To manage variations in DH generation that do not follow the demand profile, a TES (e.g. a hot water accumulation tank) could be installed in the DH network, where surplus heat can be stored for later use [6].…”

“…A TES avoids the thermodynamic losses that would result from condensing the extracted steam with cooling water. However, for combined heat and power (CHP) plants, TES implementation might not be necessary (although possible, as studied in [6]), since the extracted steam can instead be cooled by the district heating (DH) flow, temporarily causing variations in the DH generation, which can be buffered by the DH system.…”

Dynamic modeling for assessment of steam cycle operation in waste-fired combined heat and power plants

“…• Implementation of thermal energy storages for decoupling of heat and power production; internally in a gas-fired plant [3], and in district heating systems [4]. • Heat load control by interaction with CCS to allow decoupling of heat and power production, with focus on control schemes [5] and the effect of variations in available heat on capture plant performance [6]. • Primary frequency response potential of CHP plants [7].…”

Heating modes and design optimization of cogeneration steam turbines of powerful units of combined heat and power plant

“…One of the most important components of the well-being of citizens is the complete, reliable and environmentally safe provision of society's needs with heat, electricity and other energy products. A significant part of the consumption of fuel and energy resources (FER) in the World is accounted for by thermal power stations (TPS) and combined heat and power (CHP) plants, which produce electrical and thermal energy [1,2].…”