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Power electronics for variable power control of boilers

With the help of a silicon controlled rectifier, the power of a hot water boiler can be adjusted precisely according to the current excess PV output power.


In the case of self-consumption controls, the excess energy from the own photovoltaic system is used to heat the boiler, for example. Since the heating element draws a constant power, the power consumption often exceeds the value of the excess power produced. Ideally, the boiler should consume exactly the excess power which otherwise would be exported to the grid. The output of the boiler can be flexibly controlled with a silicon controlled rectifier. However, the question arises what perturbations appear by such a power converter and whether the relevant standards can be met.



  • Research and evaluation of such converters available on the market, taking into account the standards and specifications.
  • Experimental setup with the evaluated device in the institute's smart grid laboratory.
  • Proof of function and compliance with the regulations for the planned use by means of measurement series and simulations.
  • Control of the converter via an interface in order to be able to specify the heating power from 0 to 100%.


The stated project goals were successfully completed. With a silicon controlled rectifier and the corresponding control method, where the operating point can be set via an interface, it is possible to feed the excess produced instantaneous output power to a hot water storage tank while complying with the applicable standards.

Project information


FHNW Institute of Electric Power Systems


3 months


Service contract without funding

Project team

Tobias Strittmatter (Projektleiter), Thomas Tarnowski, Felix Jenni