A New Proposal for Power Quality and Custom Power Improvement: OPEN UPQC

Currently, the quality of supplied power is important to several customers. Power quality (PQ) is a service and many customers are ready to pay for it. In the future, distribution system operators could decide, or could be obliged by authorities, to supply their customers with different PQ levels and at different prices. A new device that can fulfill this role is the OPEN unified power-quality conditioner (UPQC), composed of a power-electronic series main unit installed in the medium-voltage/low-voltage (LV) substation, along with several power-electronic shunt units connected close to the end users. The series and parallel units do not have a common dc link, so their control strategies are different than traditional UPQC control techniques. This device can achieve general improvement in PQ, reducing the most common disturbances for all customers that are supplied by the mains (PQ) by using only the series unit. Additional increments in PQ (i.e., mains power interruptions), can be provided to the customers who need it (custom power) by the shunt units. Therefore, this new solution combines an improvement in PQ for all end users, with a cost reduction for those that need high quality power. The proposed solution has been analyzed and described, and a model of a 400-kVA LV grid is considered a test network to evaluate the steady-state performance and functioning limits. The results obtained under steady-state conditions justify the configuration chosen and good device performance.