Research On The Active Power Fliter Base On Three-level Inverter

Due to the rapid development of power electronics technology, non-linear load which is configured to electronic device use more and more.This cause power quality decline and harmonic pollution. In this case, it is necessary to compensate for the harmonic. With the increasing harmonic pollution, large capacity for active power filter technology will become mainstream practical applications. So, this paper studies a kind of APF based on diode-clamped three-level inverter.Firstly, the topology of the diode-clamped three-level active power filter is analyzed,including the working principle of the structure and the derivation of a mathematical model of the structure. And studies the harmonic detection of active power filter, especially based on the instantaneous activeand reactive power theory and reactive current detection theory.Through theoretical derivation and derivation clarifies the principle of the three-level SVPWM modulation.Then discuss the two main drawbacks diode clamp three-level inverter: DC side of the neutral point potential drift and the individual switch thermal overload.Methods for the DC side of the neutral point potential balancing is using optimization algorithm to control the midpoint potential of the DC side for suppressing the neutral point potential drift. For problem of uneven distribution losses of the inner and outer tube, Strategy adopted is to use redundant small vector inverter overheat switch reassign load, strategy adopted is to use redundant small vector to reassign the load of the overheat switch. Thence, the overload switch in the inverteron will decrease load. In this way heat is transferred from the affected switch to other switches without adding additional hardware.Then this paper introduces a kind of switching power supply which is applied to Three-level inverter. The power supply adopts mains supply when the DC-link voltage is quite low. When the DC-link voltage works regularly, we can get the electricity from electric capacity of DC-link voltage. The maximum input voltage is only 50% of the three level inverter DC-link voltage.After suddenly losing the power of the main system of inverter,switching power supply can still work for some time to guarantee that the protective action can still carry out reliably and to improve the safety of the main system of Inverter. Afer losing the power of inverter DC, switching power supply can provide energy-storage capacitor with capacity and release circuit. The design has been applied to a Three-level Inverter and the experiment proves that both the Three-level Inverter and the switching powersupply can work regularly and the switching power supply complys with the design requirement.Then summarize the harmonic detection of active power filter, especially based on the instantaneous activeand reactive power theory and reactive current detection theory. And simulation studies SVPWM modulation algorithm.In the end, a diode clamp APF experimental platform is designed in this paper. Various parameters of the main circuit in the experiment platform are being designed. Select the parameters of the LCL filter and design process of the inverter is introduced. Dashboard sampling circuit and driver circuit are designed. In terms of programming, experimental platform system main software flow chart and DC voltage control program flow chart and "A" phase harmonic current detection program flowchart and AD program flowchart are designed. Finally, grid zero-crossing detection circuit and DC voltage control and "A" phase harmonic current detection are tested.