Smart Grid: Shunt Compensation in Non-Sinusoidal Regimes
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- Institutt for elkraftteknikk 
The electric power theory is of fundamental importance in most aspects of electric power engineering, enabling to analyze and control the grid based on an unambiguous physical interpretation of the power and current flow. The futuristic SmartGrid concept will include scenarios of potentially very challenging network conditions, due to large impact of non-linear loads, combined with unsymmetric and non-sinusoidal voltage regimes. New and more advanced power theories are needed, in order to maintain correct physical understanding of the power grid, independently of voltage conditions. Moreover sophisticated power theories can help identify and eliminate detrimental effects induced by loads; i.e. unsymmetry, reactive power consumption and harmonic pollution. This project has reviewed the recent and promising conservative power theory (CPT). Major part of the project was dedicated to experimental research, evaluating the CPT purely from a power theory perspective. Central part of these experiments was a real-time rapid prototyping system (RPS) and three-phase voltage source converter. Control system for the programmable voltage source, data acquisition and CPT-algorithm were implemented by the RPS. Based on extensive tests it was found that the CPT offers enhanced and physical correct interpretation of current and power flow. Obtained results from the virtual instrumentation are principally consistent with and support previous research presented in the literature. Second part evaluated the CPT in context of shunt active power filter (SAPF). Experimental implementation of SAPF failed, mainly as the RPS did not provide sufficient sampling rate. Selected cases of reactive and harmonic compensation were demonstrated, utilizing computer modeling tools (MATLAB/Simulink). The results conclude that the CPT performs excellent selective compensation, only when grid voltages are balanced sinusoidal. In scenarios of unsymmetric or distorted voltages, the compensation strategies provided by the CPT are apparently less versatile and effective, compared to the popular pq-theory. Overall this study demonstrated that optimal network operation can only be achieved, through the joint action of series and parallel compensators. Future work will amongst others include further in-depth study of the rapid prototyping system, and experimental implementation of SAPF.