Interleaved Buck Converter Based Shunt Active Power Filter with Shoot-through Elimination for Power Quality Improvement

Abstract

The “shoot-through” phenomenon defined as the rush of current that occurs while both the devices are ON at the same time of a particular limb is one of the most perilous failure modes encountered in conventional inverter circuits of active power filter (APF). Shoot-through phenomenon has few distinct disadvantages like; it introduces typical ringing, increases temperature rise in power switches, causes higher Electromagnetic Interference (EMI) and reduces the efficiency of the circuit. To avert the “shoot-through”, dead time control could be added, but it deteriorates the harmonic compensation level. This dissertation presents active power filters (APFs) based on interleaved buck (IB) converter. Compared to traditional shunt active power filters, the presented IB APFs have enhanced reliability with no shoot-through phenomenon.
The instantaneous active and reactive power (p-q) scheme and instantaneous active and reactive current component (id-iq) control scheme has been implemented to mitigate the source current harmonics. Type-1 and Type-2 fuzzy logic controller with different membership functions (MFs) viz. Triangular, Trapezoidal and Gaussian have been implemented for the optimal harmonic compensation by controlling the dc-link voltage and minimizing the undesirable losses occurred inside the APF. Additionally, the adaptive hysteresis band current controller (AHBCC) is being implemented to get the nearly constant switching frequency. The performance of the control strategies and controllers for the presented IB APF topologies has been evaluated in terms of harmonic mitigation and dc-link voltage regulation under sinusoidal, unbalanced sinusoidal and non-sinusoidal voltage source condition.
This dissertation is concerned with the different topologies of 3-phase 4-wire IB APFs viz. split capacitor (2C) topology, 4-leg (4L) topology, transformer based full-bridge IB APF or single capacitor based FB IB APF (1C 3 FB IB APF) and full-bridge IB APF (FB IB APF) for low to medium power application. Moreover, APF topology is now being expanded to multilevel VSIs for high power application. Thanks to flexible modular design, transformerless connection, extended voltage and power output, less maintenance and higher fault tolerance, the cascade inverters are good candidates for active power filters with the utility of high power application. The cascaded FB IB APF is modelled with no shoot-through phenomenon by using multicarrier phase shifted PWM scheme. Extensive simulations have been carried out in the MATLAB / Simulink environment and also verified in the OPAL-RT LAB using OP5142-Spartan 3 FPGA to support the feasibility of presented IB APF topologies, control strategies and controllers during steady and dynamic condition. The performance shows that IB-APF topologies bring the THD of the source current well below 5% adhering to IEEE-519 standard. A comparison has also been made, based on SDP (switch device power) between the IB-APF topologies.