ACER's NC RfG DC Recommendation: considerations related to the HP controller

It is anticipated that in the coming years, the increase in energy produced from renewable sources may result in the electrical power generated in the grid being insufficient to meet demand.

One requirement that exists today and is not being changed is ‘low frequency demand disconnection’, which involves disconnecting loads to avoid blackouts when the grid frequency drops too low. To maximise service continuity, system providers aim to introduce a new operating mode, called ‘limited frequency sensitive mode - underfrequency consumption (LFSM-UC)’. This assumes that when the mains frequency changes within the specified limits and according to certain profiles, the connected devices, including residential heat pumps with power outputs greater than 800 W, must adapt their power consumption. Upon analysing the document, it becomes clear that the issue is both hardware and application related. To meet the required specifications on the hardware side, it will be necessary to assess whether the controller has a suitable on-board frequency meter with the required performance. If these requirements are not met, consideration must be given to including a device in the control or in the unit itself, which would further increase costs. On the software side, an action time in the order of milliseconds is required from when the frequency reduction signal is received to the execution of the consumption reduction command. Several aspects need to be considered, such as the method of action—whether it is sufficient to simply reduce the power consumption or flow temperature of all connected units by a certain percentage, or if the algorithm needs to be more sophisticated. Additionally, there is the question of whether the components of the refrigeration circuit can implement and withstand such rapid changes without failure.

In the presentation, these points will be analysed in an attempt to provide as objective an assessment as possible, highlighting the feasibility and criticality of the new proposal’s applicability.