Improving automated load flexibility of nuclear power plants with ALFC

摘要

In several German and Swiss Nuclear Power Plants (NPP) with Pressurised Water Reactor (PWR) the control of the reactor power was and will be improved in order to be able to support the energy transition with increasing volatile renewable energy in the grid by flexible load operation according to the need of the load dispatcher regarding the power system stability. Especially regarding the mentioned German NPPs with a nominal electric power of approximately 1,500 MW, the general objectives are the following automated grid-relevant operation modes (Figure 1): 1. Primary frequency control (1) with load jumps up to -200 MW (asymmetric downwards within 30 seconds and with a duration of max. 15 minutes and back to full load within 30 seconds). In this operation mode the grid frequency is linked directly to the turbine power controller in order to compensate directly the energy misbalance of the grid within 30 seconds. 2. Remote secondary control (2) by the load dispatcher; hereby stochastic load changes with gradients of 30 to 40 MW/min within a power range of ΔPG ≈ 600 MW can be required. In this case the load dispatcher directly governs the target setpoint of the turbine load within the mentioned range (which is limited in the turbine control); whereas the load gradient is set by the reactor operator according to the need of the load dispatcher and the actual possibility of the NPP. The reaction time of the load dispatcher is 15 minutes and typically the NPP gets a new setpoint every 15 minutes according to the needs of the grid and the prices in the electricity stock exchange. 3. "Classic" load following operation (3) via telephone contact with the load dispatcher with gradients up to 40 MW/min within a power range of ΔPG ≈ 1,000 MW. In this case the load dispatcher communicates via telephone with the reactor operator regarding all aspects of the load ramp (gradient, target load) and often including the duration of the part load situation. The reaction time is more than one hour. 4. Generally the primary frequency control can be combined with the other mentioned grid operating modes.