Controllably Inductive Power Filtering Method for Medium and High Voltage Distribution Networks Based on Feedforward-feedback Composite Control

When background harmonic voltage and load-side harmonic current coexist at the point of common coupling(PCC) of medium and high voltage distribution networks, it is easy to cause the PCC harmonic current to exceed the limit. It is proposed to use the controllably inductive power filtering(CIPF) system based on feedforward-feedback composite control to manage harmonics at the PCC of medium and high voltage distribution networks. After combining the grid-side(PCC) harmonic current feedback control with the load-side harmonic current feedforward control, it can provide resonance damping and realize two-way active suppression of grid-side/load-side harmonics while improving system stability. Firstly, the topological structure and characteristics of the CIPF system are introduced; the harmonic domain mathematical model and single-phase equivalent circuit of the system under feedforward-feedback composite control are established, and on this basis, the transfer characteristics of the grid-side harmonic current relative to the load-side harmonic current and the grid-side background harmonic voltage are studied, respectively; a control scheme based on the harmonic frequency division detection method is designed and the system transfer function is derived, based on which, the relationship between the control coefficient value and the system filtering performance and stability is further discussed; finally, the superiority of CIPF system filtering performance under the proposed control method is verified through simulation model.