Series-parallel active filter/uninterruptible power supply systems: Configuration, modeling, and digital control

In recent years, with the increase of non-linear loads drawing non-sinusoidal currents, power quality distortion has become a serious problem in electrical power systems. Active filters have been known as an effective tool for harmonic mitigation as well as reactive power compensation, load balancing, voltage regulation, and voltage flicker compensation. In this thesis harmonics are defined and harmonic producing loads and devices in electrical systems are introduced and categorized. Effects of harmonics on electrical systems including disturbances, extra losses, and malfunction of sensitive devices are addressed. Mitigation of harmonics using passive and active filters is explained. Different topologies and configuration of active filter systems including voltage source and current source topologies, shunt, series, hybrid, and unified power quality conditioner configurations are described in details. Topologies of active filters for output ripple reduction of DC/DC converters are explained. Different modeling methods of active filter system are briefly described. Control methods of active filter systems including instantaneous reactive power, synchronous reference frame method, unity power factor method, sliding mode of control, and other methods are explained. The new topology of series/parallel active filter/uninterruptible power supplies is introduced and its control method, different operating modes, and power management are described. Reduced-parts topologies for single-phase and three-phase series-parallel unified power quality conditioners and uninterruptible power supplies are introduced and their operating modes and control methods are discussed. Modeling of single-phase, three-phase, and series parallel active filters using generalized state space averaging method is discussed and the results are compared with the results of simulation software such as PSIM, PSPICE, and MATLAB. In the last chapter, digital deadbeat control method is applied to single-phase shunt active filter, single-phase and three-phase series-parallel systems. The digital control is discussed for different operating modes. It is implemented using Digital Signal Processor and the simulation and experimental results are presented.