Shaping the Current Waveform of an Active Filter for Optimized System Level Harmonic Conditioning

Abstract

Abstract:Harmonic voltages and currents in electrical systems, when present to a certain degree, represent not only a power quality problem but they are also strongly associated with the electrical system overall losses and they are arguably a source of instability and a safety concern. Mitigating harmonics distortion across the entire system by actively reducing harmonic currents propagation is an effective way of coping with these issues and can be dealt with the injection of a compensating current waveform with an active filter installed at a given bus. This paper shows how, by shaping the compensating current waveform in an optimal way, the overall electrical system harmonic distortion can be optimally reduced in a cost effective manner with a minimum size of the compensating device. The process of shaping this optimal compensating current is shown by how its components are defined by the optimization algorithm using the phase and amplitude of each harmonic as degrees of freedom in the process of finding the optimal waveform. A marine vessel distribution grid is used as representative example to prove the concept.

System-Wide Harmonic Mitigation in a Diesel-Electric Ship by Model Predictive Control

“…The MPC formulation described in this section is based on the models and approaches from [10], [11] and [12]. However, the implementation and the formulation of the objective function are further improved to benefit from the MPC's flexibility in the search for the optimal filter current injection.…”

“…The last part in (8) is added to punish utilization of large filter currents (amplitudes), which will make it easier for the MPC to use phase shifting in the search of the optimal harmonic mitigation [11]. The third part is added to avoid solutions that relies on zero-sequence filter currents.…”

A Distributed Compensation Method for Active Power Filters Based on Model Predictive Control and Kalman Filter Algorithm

“…However, it will be more economical to cut the number of APFs and employ the distributed compensation approach when dealing with distributed nonlinear loads. Fewer APFs are responsible for alleviating the global harmonics caused by more distributed nonlinear loads based on the updated current reference at each optimization instant [9][10][11]. Therefore, the key issue of the distributed compensation method for APFs is the online optimization of the compensation current reference as the instruction signals of APFs from a system-wide perspective.…”

Management of harmonic propagation in a marine vessel by use of optimization

“…However, only test cases with symmetrical loads were presented in this study. When asymmetrical loads are present, and especially if load 1 is more distorted than load 2, the NMPC is expected to provide even better harmonic conditioning than local filtering due to the consideration of both loads [16,17].…”