This article proposes a space vector modulated model predictive control (SVM $^{2}$ PC) for voltage source converters. It overcomes limitations of standard finite control set model predictive controller, ensuring fast dynamic response, fixed switching frequency, and low computational burden. It combines control and modulation in a convex optimization problem with affine inequality constraints to minimize the tracking errors of the output variables. First, the sector of the space vector diagram where the unconstrained solution lies is identified. Then, using the Karush–Kuhn–Tucker conditions, feasible duty cycles are computed for both linear and overmodulation regions. The proposed SVM $^{2}$ PC is extended to multilevel converters. Hardware in the loop results are presented for three different case studies: 1) Grid-forming inverter with LC filter; 2) two-level grid-following inverter with LCL filter; and 3) grid-following neutral point clamped inverter with LCL filter. Experimental results demonstrate that the proposed SVM $^{2}$ PC provides good performance, fast response, and low computational burden when compared with previously reported alternatives.

This paper provides as contribution a systematic design procedure for robust current control of grid-tied inverters with LCL filters affected by inductor magnetic soft-saturation and also by uncertain grid impedances. The proposed design is based on: i) a polytopic time-varying model to describe the effect of the inductances variations; ii) a set of linear matrix inequalities to design fixed (robust) state feedback gains, ensuring bounded settling times for the closed-loop transient responses. A less conservative set of linear matrix inequalities is used to certify the procedure. Experimental results from real-time simulations and from a real prototype with commercial powder core inductors show that the proposed procedure can provide superior results than conventional controllers designed not taking into account the soft-saturation. The results with the proposed controller comply with the IEEE 1547 Standard, leading to grid currents with low harmonic content, respecting limits prescribed by this standard even under distorted grid voltages.

Despite the several studies and approaches, the design of current controllers for grid-connected converters via LCL filters is still a challenging task. This is mainly due to the parametric uncertainties and the grid background voltage distortions to which the system is submitted. In order to overcome these inherent system challenges, this paper proposes a multiloop control framework that simplifies the system dynamics of the overall circuit by splitting it in two equivalent sub-circuits. An inner loop is implemented as a fast Sliding Mode Controller (SMC) that controls the filter capacitor voltage in a fast and robust way. As result, the plant viewed by the outer loop yields in a voltage-controlled voltage source connected to the grid through an L filter. Thus, multiple resonant controllers are included in the state-space representation of this simplified system, allowing the design of a state-feedback controller in the outer loop for asymptotic tracking of the grid current with disturbance rejection of the grid background voltage. Here, a Discrete Linear Quadratic Regulator (DLQR) algorithm is used for designing the state-feedback gains. A simple design procedure is presented, as well as simulations and experimental results, to show the good performance of the proposed control scheme even under significant uncertainties and disturbances of the system.

This paper proposes a modulated model predictive strategy suitable for current control of grid-connected converters with LCL filters, allowing fast dynamic responses with a fixed switching frequency, for both strong and weak grid conditions. The duty cycles are optimized within each switching period based on the minimization of a quadratic cost function with linear constraints from the space vector modulation. Full and reduced-order models are considered for the control design, and closed-form analytical solutions for the optimization problem are derived based on the Karush-Kuhn-Tucker conditions. The closed-form expressions for the optimal solution make it possible to implement the algorithm in real time using off-the-shelf microcontrollers. Extensive evaluation illustrates good transient and steady state performances for different grid conditions. In addition, the proposed MPC takes into account the voltage synthesis capability of the inverter and copes with overmodulation in an orderly fashion even in large transients.

This paper proposes a new carrier-based modulation strategy for symmetrical cascaded multilevel converters denominated Phase Disposition with Sorting (PDS). It deals with the issue of irregular distribution of PWM signals and power for each converter cell, that occurs when using the conventional Phase Disposition (PD) modulation. Although some alternatives have been proposed in the literature for overcoming these problems, most of them do not consider operation of the converter under fault conditions on the power cells. Therefore, one of the contributions of the proposed PDS modulation strategy is the ability to evenly distribute the pulse signals for the converter semiconductor switches, resulting in the same power being processed by all cells, maintaining the good quality of the synthesized output voltages, even with faults in one or more power cells. In addition, it allows implementation in commercial DSPs (Digital Signal Processor), not requiring additional hardware. The good performance of the proposed modulation strategy is validated through experimental results for a three-phase symmetrical cascaded multilevel converter with 3 cells per phase, considering normal and faulty conditions on the power cells.

This paper proposes a combined synchronization method for full scale converter of wind turbine (WT) aiming to ride trough balanced and unbalanced voltage dips due grid faults. A Kalman filter synchronization (KFS), capable extract the positive and negative sequence grid voltages, is designed to have a fast response to voltage disturbances. Then, a synchronous reference frame phase locked loop (SRF-PLL) is used as a inertia on the synchronization signals. As a result, the converter is able to provide faster response to voltage disturbances as voltage grid support even in the cases where the voltage falls to zero on the PCC. Also, and anti-windup strategy is introduced on the current control loop to avoid undesirable behavior during fault transitions. Simulation results demonstrate that the proposed combined synchronization method and the anti-windup control enhances the performance of grid connected converters during voltage dips situations and improves the low voltage ride trough capability of grid connected converters.