New Modeling and Improved Current Control Strategy to Eliminate the Impact of Synchronization Method and Parks Transformation for Grid-connected Four-leg PWM Inverter

Abstract

The synchronization method’s ability is one of the fundamental guarantees for the stability and accuracy of injected current control for grid-connected converter-based distribution resources. These synchronization methods, such as phase locked loop (PLL), are generally based on Park transformation and grid voltage regulation, which may affect an unstable phenomenon under distortion and unbalanced grid voltage conditions and result in more computational complexity. In this present paper, analogous to the traditional voltage-oriented control strategy (VOC) in the synchronous rotating frame (dq0-frame) based on PLL and Parks transformation, an improved voltage-oriented control strategy (IVOC) without synchronization methods and Parks transformation is proposed for grid-connected four-leg inverters (GC-FLVSI) to achieve accurate current control with high-quality performance in the dq0-frame. This proposed strategy is not only used for controlling the GC-FLVSI but also to provide the module of GC-FLVSI in the dq0-frame based on the instantaneous active and reactive powers theory (DPC). The proposed IVOC strategy has the same properties and identical performance as the traditional VOC when the grid phase angle is correctly detected by any synchronization method, with the advantages of both traditional DPC and VOC at the same time. In order to validate the superiority and excellent dynamic and steady-state performances of the proposed IVOC strategy in comparison with the traditional VOC strategy, some simulation scenarios using MATLAB/Simulink under different operations and grid conditions have been performed and presented.

Transformation of Type I Fuzzy Logic into Interval Type II Fuzzy Logic-based Unit Voltage Template with Controlled Load

“…The surface is simply identified as three-dimensional mapping of the two inputs' values and the output's values. In the mentioned case above, the MTLAB program applies the inputs' values from the specific range E [−5,5] CE [−0.5,0.5] in the nine rules mentioned above, and then extract the output values from its specific range [11][12][13][14][15][16][17]. Then, the MATLAB program plot the extracted output values as a surface of three-dimensional mapping in the respect of the inputs' values.…”

“…For the improvement process, inverter-based power quality conditioners are used in these days, because of their small size and fast response in comparison with conventional ways [12][13][14]. The utilizing of Distribution Static Synchronous Compensator (DSTATCOM) device in the distribution grid compensates the reactive power, returns the electrical current waves to sinusoidal form, leading to the enhancement the power quality [15][16][17].…”

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