In this paper, a generic complex repetitive controller (nk + m RC, k$\times$Z), based on the inverse transfer function of the generalized delayed signal cancelation transformation is proposed. The presented complex controller can be designed for regulating different positive- and negative-sequence harmonic components through a space-vector error signal, with improved response time as compared to traditional repetitive controllers. An evaluation of the proposed control scheme stability, based on phase margin, Nyquist diagram and sensitivity function is presented. The effects of the controller parameters on the system's stability and also on its dynamic response are shown and allow the definition of some control design guidelines. Experimental results are presented to validate the theoretical assumptions through applying the proposed controller for regulating the currents in a three-phase active power filter.

Repetitive controllers (RC) represent a good solution for systems having periodic reference or disturbance signals containing several harmonic components. Although some practical solutions to make RCs stability conditions more flexible, methodologies for tuning these cannot be easily found. This paper presents a design method to tuning RCs, based on the use of sensitivity function together with phase margin as design tools. After presenting the design procedures, they were validated through experimental results.

Voltage profile is one of many aspects that affect power quality in low-voltage distribution feeders. Weak grids have a typically high line impedance which results in remarkable voltage drops. Distribution grids generally have a high R/X ratio, which makes voltage regulation with reactive power compensation less effective than in high-voltage grids. Moreover, these networks are more susceptible to unbalance and harmonic voltage disturbances. This paper proposes an enhanced coordinated control of active and reactive power injected in a distribution grid for voltage regulation. Voltage drop mitigation was evaluated with power injection based on local features, such loads and disturbances of each connection. In order to ensure disturbances rejection like harmonic components in the grid voltages, a repetitive vector-control scheme was used. The injection of coordinated active and reactive power with the proposed control algorithm was verified through simulations and experiments, demonstrating that it is a promising alternative for voltage regulation in weak and low-voltage networks subject to inherent harmonic distortion.

This paper addresses the voltage-drop problem in a low-voltage network with distributed loads. A radial distribution feeder is used to show how voltage drop occurs in such systems. Theoretical analysis shows why traditional reactivepower approaches are not fully effective in resistive grids. Power management is used to coordinate between active and reactive power for proper voltage regulation. The control strategy ensures voltage regulation with reactive and active power under a high R/X ratio and load change conditions. The control method is evaluated in a low-voltage distribution network, and the simulation results validate such method’s effectiveness.

The project of controllers for an AC Active Electronic Power Load capable of emulating non-linear currents brings some challenges, like the necessity of high performance controllers and damping of the resonant coupling filter with the Equipment Under Test. On the other hand, high dynamic controllers require high switching frequencies in a Pulse Width Modulation, but power semiconductors with high currents and high frequency capabilities are difficult to obtain. In this paper, it is proposed a control strategy for the T-Type Neutral Point Clamped Interleaved Converter in a single-phase active electronic load application. State observer and state feedback in addition with classic controller are used for high current harmonics tracking. The control oriented modeling and the control system design are presented. Simulation and experimental results obtained from a 10 kW single-phase three-level converter prototype illustrate and demonstrate the feasibility of the proposed control strategy.