A Combined Series Active Filter and Passive Filters for Harmonics, Unbalances and Flicker Compensation

Abstract

This paper describes a combined operation involving a series active filter and shunt passive filters for three-phase three-wire systems. The series active filter is able to minimize Power Quality problems like unbalances, harmonics and flicker observed at the system voltages. Another task for the series active filter is to damp possible resonances involving the passive filters and the system impedance. The shunt passive filters are designed to drain harmonic current-components generated by the load. The control strategy of the series active conditioner is based on the instantaneous power theory on α-β-0 reference frame, together with a robust synchronizing circuit PLL (Phase-Locked-Loop). A dc-link voltage controller, applied to the series conditioner, is also introduced due to the fact that there is only a single capacitor at the inverter dc-side. Simulation results on PSCAD®/EMTDC™ are presented in order to verify the performance involving a combined operation of passive and active filters.

Active Power Conditioners to Mitigate Power Quality Problems in Industrial Facilities

“…On the other hand, the Series Active Power Filter works as a voltage-source connected in series with the electrical power grid, compensating voltage harmonics, sags (sudden reduction of the voltage followed by its recovery after a brief interval), swells (sudden increase of the voltage followed by its recovery after a brief interval) and flicker (cyclic variation of light intensity of lamps caused by fluctuation of the supply voltage). Three-phase Series Active Power Filters can also compensate unbalances in the phase voltages [12]. If the DC link of the Series Active Power Filter inverter is connected to a power supply, its compensation capabilities increases, allowing also the compensation of long term undervoltages and overvoltages [10,11].…”

“…The three-phase Series Active Filter can also balance the load voltages [20]. Figure 5 shows the electrical scheme of a Series Active Power Filter for a three-phase power system.…”

“…Passive filters have been used as a solution to solve harmonic current problems, but they present several disadvantages, namely: they only filter the frequencies they were previously tuned for; their operation cannot be limited to a certain load; the interaction between the passive filters and other loads may result in resonances with unpredictable results [6]. To cope with these disadvantages, in the last years, research engineers have presented various solutions based in power electronics to compensate power quality problems [6][7][8][9][10][11][12]. These equipments are usually designated as Active Power Conditioners.…”

Comparison of current-source and voltage-source Shunt Active Power Filters for harmonic compensation and reactive power control

“…The p-q Theory power components are calculated using the expressions (3) and 4, where p is the instantaneous real power, and q is the instantaneous imaginary power (by definition).…”

“…Therefore the use of this type of loads imposes the development of solutions for the mitigation and reduction of the Power Quality problems. Some adopted solutions for these problems, such as passive filters for harmonic mitigation, or capacitor banks for reactive power compensation, can cause other problems such as resonances, voltage transients and others [3]. Shunt Active Power Filters (SAPFs) are a good solution, and have been developed over the years [4][5] [6].…”