Simscape Electrical provides two simulation technologies: Libraries Compatible with Simscape Technology and Specialized Power Systems Library. See Simscape Electrical Block Libraries for more details.
The recommended approach is to build your entire model in one of the technologies. Unfortunately, it's not possible to directly connect blocks from multiple technologies although converter blocks are provided should it be necessary.
For low-detail semiconductor models you can use either technology. For multidomain models, and models with options to add higher levels of detail, use the blocks which are compatible with Simscape Technology.
