Search

SUMMARY The cascaded H-bridge (CHB) multilevel inverter is being recognized as the most suitable topology for high-power medium-voltage power quality conditioning applications. This paper presents mathematical modeling and effective controller design methodology for the CHB-based active power filters (APFs), which achieves dynamic reactive power and harmonic compensation. The most crucial problems in CHB-APF control are the simultaneous requirements of both accurate harmonic current compensation and the dc-link voltage stabilization among the H-bridges, which is the prerequisite for the stable operation of CHB-APF. To achieve dc-link stabilization, a novel voltage balancing algorithm is proposed by splitting the dc-link voltage control task into two parts, namely, the average voltage control and the voltage balancing control, where the sine and cosine functions of the phase angle of the fundamental component of the grid voltage are used, respectively. To ensure accurate phase tracking, a novel phase-locked loop (PLL) is proposed by using the adaptive linear neural network (ADALINE), where the grid voltage background distortion is also taken into account. The superior performance of the ADALINE-PLL is validated by comparison with the existing PLLs in literatures. Furthermore, the proportional-resonant (PR) controller is used for the reference current tracking. A separate ADALINE algorithm is applied for reference current generation (RCG) for the CHB-APF. The excellent performance of the ADALINE-based RCG scheme is verified by comparison with the existing RCG schemes, namely, the low-pass filter approach and the single-phase p − qmethod. The experimental results on the three modules CHB-APF are presented, which verifies the effectiveness of the proposed control algorithms. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A novel multilevel inverter topology that improves the basic step inverter topology was presented. The methods for harmonic elimination and magnitude control of the output waveform of the inverter were discussed. The inverter has n DC separated power sources, 2n+4 switches to create 2n+1 levels. The inverter has low switch frequency and high efficiency as usual multilevel inverter. It uses less semiconductor switches and eliminates the shortcomings of the basic step inverter such as voltage distortion under inductor load, unbalanced power source output. It is expected to be used in renewable energy system. The simulation results of the basic step inverter and the proposed step inverter under different loads show the feasibility of the topology. [ABSTRACT FROM AUTHOR]

A new technique for grid connected photovoltaic (PV) system that can realize the reactive power compensation (RPC) was presented. The active current and reactive current of the inverter are regulated with changing the amplitude and the phase of the output voltage of the inverter. The active power output and the RPC of the system are realized synchronously at daylight. When the insolation is weak or the PV modules are left unused at night, however, the RPC can still be used, which improves the efficiency of the system. The simulation results validate the feasibility of the technique. [ABSTRACT FROM AUTHOR]

Aiming at the seam tracking and weld penetration based on welding temperature field, seam position and penetration parameters were extracted by image processing which is captured by a compact real-time measurement system. An intelligent controller was designed for welding process charactering as multivariable and non linear to realize dynamic control for seam tracking and weld penetration control. Finally, the developed system was applied in the seam tracking and penetration control of inner welding of spiral steel pipe with submerged arc welding. [ABSTRACT FROM AUTHOR]