This paper proposes a sliding-mode controller for a single-stage, three-phase current source inverter supplying an isolated load. The control architecture, derived from the $d q$ model of the converter, features two cascaded loops: an inner slidingmode control loop that regulates the $q$-axis voltage component together with the DC current, and an outer proportional-integral control loop for the $d$-axis. In contrast to traditional linear methods, the proposed sliding-mode control enhances system robustness and transient performance, while the cascaded scheme overcomes the inherent non-minimum phase behaviour of boosttype converters. The effectiveness of the proposed control strategy is verified through numerical simulations, and its practical feasibility is demonstrated experimentally using a Hardware-in-the-Loop (HIL) platform.

The integration of renewable energy sources into modern distribution grids is accelerating the development and deployment of advanced power electronics solutions. Multiport converters (MPCs) offer a promising approach by integrating multiple ac and dc ports into a single device, improving efficiency, cost-effectiveness, and grid resiliency. This article presents a nonisolated medium-voltage (MV) MPC with a modular multilevel converter (MMC) architecture in the ac-dc ports. Two control approaches, classical strategy and crossed strategy, are compared to evaluate their performance under normal and abnormal conditions, respectively. The study presents modifications to enhance ac and dc fault-ride-through. The control strategies are validated through time-domain simulations using TyphoonSim and a Typhoon control hardware-in-the-loop (CHIL) setup.

Power electronics components are becoming essential for smart grids, especially integrating systems such as renewable energies, storage or electric vehicles. Multiport converters are presented as a solution to reduce the cost of installing individual power electronic devices and integrating multiple AC and DC systems. This paper proposes a centralized DC voltage control for non-isolated Multiport converters with a common DC bus. Such control is designed for a proper dynamic response in normal operation and AC fault-ride through capability. The centralized DC voltage control is validated in three- and four-port converters, where AC ports are connected to two feeders of the same distribution AC grid. DC ports are connected to a battery or DC load. Time-domain simulations in Matlab Simulink are used to test the presented control strategy in several case studies.

We carry out a detailed analysis of direct voltage control of a Boost converter feeding a simple resistive load. First, we prove that using a classical PI control to stabilize a desired equilibrium leads to a very complicated dynamic behavior consisting of two equilibrium points, one of them can be stabilized for PI gains within certain negative ranges, while the second equilibrium point may also be rendered stable-but for sufficiently large positive tuning gains. Moreover, if we neglect the resistive effect of the inductor, there is only one equilibrium and it is stable for a certain range of negative PI gains. From a practical point of view, it is important to note that the only useful equilibrium point is that of minimum current and that, in addition, there is always a resistive component in the inductor either by its parasitic resistance or by the resistive component of the output impedance of the previous stage. In opposition to this scenario, we recall three nonlinear voltage-feedback controllers that ensure asymptotic stability of the desired equilibrium with simple gain tuning rules, an easily defined domain of attraction, and smooth transient behavior. Two of them are very simple, nonlinear, static voltage feedback rules, while the third one is a variation of the PID scheme called PID-Passivity-based Control (PBC). In its original formulation, PID-PBC requires full state measurement, but we present a modified version that incorporates a current observer. All three nonlinear controllers are designed following the principles of PBC, which has had enormous success in many engineering applications.

The integration of power electronic converters in power distribution systems is introducing new dynamic interactions that could lead to instabilities. This paper analyzes the impact of Multiport Converters (MPCs) on grid stability based on small-signal analysis, in particular, modal analysis methods. Four scenarios are tested on the IEEE 33-bus system, including radial topology, meshed topology, grid-following MPCs, and islanded grid-forming operation. Results show that converter interactions, particularly reactive power control and converters operating points, significantly influence system dynamics. Small-signal linear models and results are validated using non-linear simulations.

The Synchronous Reference Frame Phase-Locked Loop is a central component of grid-following Voltage Source Converters. Previous research has shown that the differential equation introduced by this loop is a swing equation, similar to that of the synchronous machine. This paper analyzes the large-signal stability of a single converter connected to an infinite-bus system. The outcome is a boundary in the plane of the parameters separating a region of insufficient damping and a region of sufficient damping. Moreover, the boundaries of stability from the small-signal analysis are also included for completeness. The findings are validated via time-domain simulation in EMT models.

Synchronous machines and grid-following converters exhibit nonlinear second-order differential equations that rule their synchronization dynamics. Furthermore, the attraction exerted by the stable equilibrium points is limited to a certain region of attraction. In small networks, where a single generator is connected to an infinite bus, the region of attraction is bounded by curves, and can be plotted in a plane. Hence, this paper presents a simplified version of the reverse trajectory method for identifying the region of attraction of an equilibrium point. The selection of the initial conditions is backed with physical arguments, and the performance of the method is tested with different parameters. A three-phase short circuit is also tested to verify the consistency of the boundaries obtained with this technique.

Impedance-based stability analysis techniques are increasingly used to assess the stability of power converter-dominated power systems. Among these techniques, the Generalized Bode Criterion (GBC) has emerged as a robust method, combining the strengths of the Nyquist Stability Criterion (NSC) with the ease of application of the Bode criterion. However, the GBC requires knowledge of the phase derivative at 0 Hz, which can be challenging to obtain when the system transfer function is analytically unknown. This paper proposes and proves a mathematical relation to eliminate the need for the phase derivative in the GBC. Consequently, all necessary information required for the GBC can be directly obtained from the system Bode plot, enabling the application of the GBC to power systems represented by black-box models with no detailed internal information. The proposed approach is validated by analyzing the stability of a DC-DC converter connected to a DC grid and comparing the results with time-domain simulations.

Among the different groups of stability issues that railway systems have to face are the electrical resonance instability phenomena. Within this group, one of the possible instability problems that appear is due to the constant power load (CPL) behavior of the traction and the auxiliary power system (APS) converters. This behavior interacts negatively with the variable impedance of the catenary and can cause catenary voltage fluctuations and compromise the stability of the railway line. To solve this problem, this article proposes the use of a structured H infinity synthesis to design an ac voltage controller for the APS converter. The algorithm models the dc input admittance of the converter addressing three objectives: catenary stability, tracking of the ac output voltage reference, and robustness against unmodeled uncertainties. Experimental results with different types of loads (resistive and/or induction machine loads) demonstrate its compliance with railway standards and the modeling of the specified admittance.

This letter derives and discusses the superiority of a simple dc-link capacitor voltage control configuration for multilevel neutral-point-clamped converters with any number of levels. The control involves n−2 control loops regulating the difference between the voltage of neighbor capacitors. These control loops are inherently decoupled; i.e., they are independent and the control action of one loop does not affect the others. The good performance of such control is confirmed through simulations and experiments.

This paper presents the design of a Proportional-Integral Passivity-based Controller (PI-PBC) for a current source inverter feeding a resistive load. Thanks to the definition of a new passive output, the closed-loop system is shown to be globally asymptotically stable. This result solves the internal stability problem reported for these power converters. To robustify the control algorithm, the paper also includes the design of a parameter estimation scheme for the parasitic resistances and the load conductance. Numerical simulations are carried out to validate the control algorithm. The simulation stage compares the behaviour using the averaged model of the power converter and a more realistic switching model, including the three-phase implementation.

This paper presents a design methodology for the output voltage control loop of a dual active bridge (DAB). It is based on fixed-order H ∞ non-smooth synthesis combined with passivity restrictions over closed-loop impedance transfer function, known to have a critical impact on system voltage stability. The proposal inherits the advantages of modern techniques, making use of simple frequential weighting-based design and plant dynamical complexity black-boxing, while keeping controller complexity low.

The averaged model of a current source inverter (CSI) as a voltage source inverter (VSI) dual is presented in this paper. The differential equations defining the CSI are in-troduced in matrix representation for phase-to-phase and phase-to-neutral voltages and expressed using the Clarke and Park transformations. This multiple-input, multiple-output system is studied through the transfer function matrix of the linearized model, and the results are related to original CSI dynamics. Finally, open-loop simulations using Matlab/Simulink and realtime Typhoon-HIL have been carried out to validate the models.

This paper analyzes the zero dynamics of three-phase current source inverters fed from a voltage source and connected to a local resistive load or the electrical power grid. The zero dynamics is the remaining dynamics of a system when it exactly meets the control objectives. It is important for understanding the system behaviour, and its limitations, and designing efficacious controllers. The analysis concludes that, when the power source is modelled from its Thévenin equivalent circuit, some stability problems occur in the dc link if the control scheme only tracks the output voltage. The paper includes an alternative nested-loop controller that overcomes the internal dc-current instability.

This paper compares four sliding-mode control strategies for a dual active bridge. The proposed control algorithms define different switching functions resulting in first- and second-order controllers, and using both discontinuous and continuous sliding-mode algorithms. The paper details the design stage and includes simulation and experimental tests to better compare the performance for each control scheme.

En este trabajo se describen un conjunto de materiales pedagógicos que han sido desarrollados para dar soporte a la docencia del control digital. En particular, se presentan un conjunto de herramientas interactivas y el proyecto Duino-Based Learning (DBL) pensado para desarrollar prácticas experimentales de control digital utilizando Arduino. Además, se describe el contenido de un curso de control digital, que se imparte en el marco de una titulación de ingeniería industrial, y como se utilizan las diferentes herramientas desarrolladas en su docencia.

This work describes a set of teaching materials that have been developed to support the learning of digital control. In particular, it presents a set of interactive tools and the project Duino-Based Learning (DBL) that has been designed to develop experimental practices of digital control using Arduino. In addition, the paper depicts the contents of a digital control course, taught in the framework of an industrial engineering degree, and how the developed tools are used in its teaching.

This paper presents a sliding mode control strategy for a dc-dc dual active bridge converter. The controller is based on a truncated model obtained using the generalized state space averaging method that transforms the mixed dc-ac dynamics of the converter into a regulation problem. The proposed controller, that uses a dynamic extension to overcome the structural problem of the non-affine control input, provides good results in terms of performance and robustness. Numerical simulations are included to validate the proposed modelling methodology and the control design.

Constant power loads (CPLs) in power systems have a destabilizing effect that gives rise to significant oscillations or to network collapse, motivating the development of new methods to analyse their effect in AC and DC power systems. A sine qua non condition for this analysis is the availability of a suitable mathematical model for the CPL. In the case of DC systems power is simply the product of voltage and current, hence a CPL corresponds to a first–third quadrant hyperbola in the loads voltage–current plane. The same approach is applicable for balanced three-phase systems that, after a rotation of the coordinates to the synchronous frame, can be treated as a DC system. Modelling CPLs for single-phase (or unbalanced poly-phase) AC systems, on the other hand, is a largely unexplored area because in AC systems (active and reactive) power involves the integration in a finite window of the product of the voltage and current signals. In this paper we propose a simple dynamic model of a CPL that is suitable for the analysis of single-phase AC systems. We give conditions on the tuning gains of the model that guarantee the CPL behaviour is effectively captured.