The most common electric source of electrical energy is in the USA the public three-phase, 60 Hz [1–4] utility system. Within the continental US there are three distinct separate AC power pools: the Eastern, Western, and Texan system representing a total of 1,000 GW installed capacity. These separate systems are interconnected by relatively low power (100 MW) DC transmission lines in order to permit some exchange of electric power between the Eastern Interconnection (System), Western Interconnection (System), and Texan ERCOT System – where ERCOT stands for Electric Reliability Council of Texas – as depicted in Fig. 3.1 [5, 6]. The DC transmission line in California has a rating of about 1,000 MW.