You cannot combine blocks from the Simscape Electrical toolbox with the blocks under 'Specialized Power Systems'. One should reside to the regular Simscape Electrical blocks, or stay within 'Specialized Power Systems'. You could for example use the 'RLC Branch' and enter a C-value only to implement a capacitor in 'Specialized Power Systems'.
I personally avoid using 'Specialized Power Systems' altogether since the Simscape Electrical library integrates well with other Simscape components and domains. Reasons why anyone would still use 'Specialized Power Systems' in my opinion are:
- you are simulating only in this domain
- you need a very specific block in this library
- you have a legacy simulation model still using this domain
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