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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]