I. Introduction
Due to the proliferation and development of power electronics equipments (nonlinear loads) in utility power system, the power quality problems such as reactive power, current harmonics and neutral current in power system are deteriorated [1]–[2]. These power quality problems may affect the safety operation and increase the loss of the power grid and electrical equipments. In order to solve the power quality problems, power filters are widely used. Passive filter (PF) has been widely applied to suppress current harmonics and improve power factor due to its low cost and simplicity. However, it has some drawbacks such as resonance problems, low dynamic response, dependent filtering characteristics, etc. [3]–[4]. Active power filter (APF) can overcome the above mentioned drawbacks inherent in PF, but the initial and running costs of the APF are much higher than the PF [5]–[6], Therefore, it comes up with a hybrid active power filter (HAPF), which combines the advantages of PF and APF, and it is characterized by low cost and good performance [7]–[8].