Advantages and challenges of dynamic link library applications in root-mean-square simulations

Dynamic Link Library (DLL) applications are a powerful approach for modelling of the vendor-specific functionality of equipment and control systems to be shared with clients without divulging of privileged information, intellectual property or know-how of the vendor. A clear advantage of the DLL applications is that the vendor can convert complete and sufficient models of the equipment and control systems from a preferred by the vendor simulation software, such as C++, into the DLL applications to be used for co-simulation with the client’s software, such as the DIgSILENT PowerFactory®, for dynamic stability assessment of large, multi-vendor, electric power systems. Among pronounced challenges can be: (i) - performing fully variable time-step simulations, i.e., automatic adaption of the time-step within a required range of 1 to 10 ms, and (ii) - appearance of numerical discontinuities at the simulation events, i.e., so-called numerical spikes in voltage and reactive power due to abrupt voltage changes following application or clearance of short circuits. Excessive numerical spikes are not present in the measurements conducted for the model validation. This paper demonstrates a method developed by Siemens Gamesa Renewable Energy for overcoming challenges of the DLL applications and delivering network-code compliant simulation models to the clients for dynamic stability assessment of large power systems.