Yap Hoon

Enhanced Instantaneous Power Theory with Average Algorithm for Indirect Current Controlled Three-Level Inverter-Based Shunt Active Power Filter under Dynamic State Conditions

An enhanced harmonics extraction algorithm based on Instantaneous Power (PQ) Theory is proposed for indirect current controlled (ICC) three-level neutral point diode clamped (NPC) inverter-based shunt active power filter (SAPF). SAPF is famous in current harmonics mitigation for its flexibility in dealing with dynamic state conditions. As for its controller, PQ Theory has served the major role in harmonics extraction algorithm due to its simple implementation features. However, it suffers from serious time delay due to its dependency on sluggish numerical filters. Furthermore, the algorithm is mostly designed to suit the operation of direct current controlled (DCC) SAPF which requires the knowledge of actual SAPF current (injection current). This leads to inaccurate mitigation as the injection current does not possess the exact information on actual source current which suffers from switching ripples problems. Therefore, two major modifications are introduced involving the development of mathematical average algorithm to replace numerical filter for fundamental real power computation and the formation of mathematical current relationship to change DCC to ICC based operation. The proposed algorithm is developed and evaluated in MATLAB/Simulink. From the simulation results, significant improvement in terms of Total Harmonic Distortion (THD) and response time is presented in comparison to conventional algorithm.

A Simplified Synchronous Reference Frame for Indirect Current Controlled Three-level Inverter-based Shunt Active Power Filters

This paper presents a new simplified harmonics extraction algorithm based on the synchronous reference frame (SRF) for an indirect current controlled (ICC) three-level neutral point diode clamped (NPC) inverter-based shunt active power filter (SAPF). The shunt APF is widely accepted as one of the most effective current harmonics mitigation tools due to its superior adaptability in dynamic state conditions. In its controller, the SRF algorithm which is derived based on the direct-quadrature (DQ) theory has played a significant role as a harmonics extraction algorithm due to its simple implementation features. However, it suffers from significant delays due to its dependency on a numerical filter and unnecessary computation workloads. Moreover, the algorithm is mostly implemented for the direct current controlled (DCC) based SAPF which operates based on a non-sinusoidal reference current. This degrades the mitigation performances since the DCC based operation does not possess exact information on the actual source current which suffers from switching ripples problems. Therefore, three major improvements are introduced which include the development of a mathematical based fundamental component identifier to replace the numerical filter, the removal of redundant features, and the generation of a sinusoidal reference current. The proposed algorithm is developed and evaluated in MATLAB / Simulink. A laboratory prototype utilizing a TMS320F28335 digital signal processor (DSP) is also implemented to validate effectiveness of the proposed algorithm. Both simulation and experimental results are presented. They show significant improvements in terms of total harmonic distortion (THD) and dynamic response when compared to a conventional SRF algorithm.

New technique for decreasing of total harmonic distortion of three-phases bridge rectifier by using the method of harmonic injection

Bridge rectifier of three-phases is has widely applications in power systems. This rectifier consummates a wave form that has been shaped by a non-linear of the input current, though in the power system. The harmonic parts caused by such power electronic devices have critical effects on a number of aspects of power networks, particularly, on distribution. In accumulation, the value of Total Harmonic Distortion (THD) is high; it causes unwanted distortion on the sinusoidal figure of the wave for the input current. The outcomes propose a new circuit for a three-phase rectifier, making use of harmonic current injection method. The MATLAB software has been used to simulate the proposed circuit. A prototype has been developed to prove the actual results and compare them with the simulation results of the proposed circuit. The proposed circuit applies active harmonic current injection method with a capacitor bank, which, compared to conventional circuits, is not sophisticated. The model has been verified with feedback injection harmonic current to demonstrate the strength of the system. The evaluation of the simulation results and experimental outcomes from the prototype represents an unimportant difference. The proposed circuit has minimized the THD drawn from the input current supply down to 5.5%.

Three-phase three-level shunt active power filter with simplified synchronous reference frame

Shunt active power filter (SAPF) is the most effective solution to current harmonics. In its controller, Synchronous Reference Frame (SRF) principle has widely been applied in current harmonics extraction algorithm due to its simple implementation features. However, the conventional SRF algorithm performs with serious time delay due to strong reliance on sluggish numerical filters. Moreover, the algorithm is still considered to possess unnecessary features which impose excessive computational burden to the designed controller. Therefore, this paper presents a simplified SRF algorithm with improved performance for the purpose of current harmonics extraction in three-phase three-level neutral-point diode clamped (NPC) inverter-based SAPF. Two potential modifications are implemented which include replacement of numerical filter with mathematical based average identifier to improve mitigation performance and removal of redundant features to reduce algorithm complexity. The proposed algorithm is developed and evaluated in MATLAB / Simulink. Simulation results have confirmed the improvement achieved by the proposed algorithm in comparison to the conventional algorithm.