Control algorithms for series static voltage regulators in faulted distribution systems

Power quality and availability are becoming important issues for critical and sensitive loads. This paper presents a viable alternative to the use of uninterruptible power supplies solutions for three-phase load voltage support. This support is provided by a series compensator structure with a rating equal to a fraction of the load. The paper discusses control issues and proposes a control algorithm that results in a fast dynamic response and is insensitive to the type of fault and to disturbances and harmonics present on the power network. The technique is applied to a faulted distribution system to compensate for voltage sags. The steady state compensation capability of the scheme is derived. The dynamic performance is analyzed and verified through experimental tests on a 2 kVA prototype power conditioner. Practical issues, such as power and control circuit design and converter ratings are considered.