Supercriticalrankine400mwe

Description

This is an example model of a supercritical coal fired power plant including a control system. It covers a closed steam cycle and a large part of the fluegas line with air pre-heater and coal combustion. The plant is operated in turbine following mode or integrated turbine following mode.

Introduction

The main purpose of this example is to demonstrate load changes and ancillary services and the interactions of different control actions. Offering services to stabilize the electrical grid is one of the major tasks for thermal power plants. In order to guarantee this, it is required to activate or deactivate power production within seconds. The most challenging action for dynamic operation of thermal power plants is provision of primary frequency control. Usually the dynamics of changing fuel flow are much to slow to provide such a fast response. Therefore internal storages in the power plant process need to be utilized to bridge the time from the fuel flow change response to a change of generator output [1]. On the ancillary service market the ability to provide this service is compensated [2]. In order to participate in this market, a power plant needs to be prequalified in a test scenario by the transmission system operator. The test includes simulated mains frequency deviation as an input to which the plant should react by providing a counteracting power output as shown in the graph:

Scenario

The example should demonstrate typical dynamic procedures of a thermal power plant in normal operation. For setting up the scenario inputs use the controlSystem interface.

Constant load

For simulation of a steady state point leave the variableLoadSetpoint on false and the primaryFrequencyControl deactivated. The plant will run on a constant load setpoint.

Load change

For simulation of a load change set the Boolean variableLoadSetpoint on true. The loadChangeTable will be enabled to specify the schedule for the power plant. By default a negative load change is performed.

Qualification test for anciallary services

For a qualification of primary frequency control either a test for positive control power output or negative control power output can be performed by selecting the corresponding option for frequencyInput. In addition, the primaryFrequencyControl needs to be active. This option requires the selection of the advancedControl (set true). Now the desired amount of responsePower can be selected.

Up to 2% of power response is provided by using high pressure turbine valve throttling. The primary frequency controller uses the turbine valve to either store or unstore thermal energy from the high pressure steam part of the boiler.
Over 2% and up to 5% of power response is provided by additionally using throttling of the steam flow through the high pressure preheater. This measure utilizes the thermal storage of the preheater and the economizer.
Over 5% and up to 7% of power response is provided by additionally using condensate retention. By changing the flow of condensate, thermal energy is stored or unstored from the feedwater tank.

Output

The main output for evaluating the amount and quality of the primary frequency control reserve is the generated power, see steamCycle.generator.power. It can be observed that while the primary load controller is activated, the response of power output reaches the desired amount within 30 seconds. Other intersting values to observe are the live steam pressure steamCycle.liveSteam.p, the flow through the high pressure preheater valve steamCycle.valve_hp.feed.m_flow and the level of the condenser steamCycle.condenser.y when the maximum amount of control reserve is activated and all those storage measures are in action.

References

1: Huebel, M., Meinke, S., Nocke, J., Hassel, E.:: "Identification of Energy Storage Capacities within large-scale Power Plants and Development of Control Strategies to increase marketable Grid Services"; ASME Power and Energy Conference, 2015, San Diego, USA