This paper presents a real-time predictive control strategy aimed at maximizing energy self-sufficiency in an industrial microgrid integrating photovoltaic (PV) generation, lithium-ion battery storage, and bidirectional electric vehicles, using the paradigm of Vehicle to Grid (V2G). The proposed Economic Model Predictive Control (EMPC) framework leverages forecasts of solar production, load demand, and vehicle availability to optimize energy flows over a prediction horizon. The control architecture relies on a real-time implementation using industrial-grade hardware, with a layered structure combining a programmable logic controller (PLC) and a Python-based optimization environment. The system is experimentally validated on a testbench equipped with real power converters and programmable loads. Results demonstrate that the integration of V2G enhances the flexibility and autonomy of the microgrid, enabling reduced dependence on the external grid and improved use of renewable resources. The proposed approach contributes to the development of resilient and intelligent energy systems for industrial applications.

This paper presents an improved generalized super-twisting control (IGSTC) scheme for neutral-point-clamped (NPC) converters subject to the line-inductance parameter uncertainties. By optimizing the algorithm structure, the proposed method accelerates transient response. An online fixed-time inductance estimation algorithm is integrated into the current-tracking loop, significantly enhancing the system’s robustness against inductance variations. Through Lyapunov-based analysis, the practical finite-time stability of the IGSTC and the practical fixed-time convergence of the identification algorithm are rigorously established. Finally, comprehensive simulations under both nominal and varying inductance scenarios validate that the superior performance of the proposed strategy.

Thyristor branch loop (TBL)-based hybrid MMC (HMMC) is one of the promising technical solutions to handle the DC-line short-circuit faults in high voltage direct current (HVDC) systems. However, the submodule (SM) capacitor precharging characteristics of TBL-HMMC is quite different from conventional MMCs, due to the special configuration. During SM precharging and system startup process, the TBL-HMMC may suffer from surge current, SM capacitor under-voltage, unbalanced capacitor voltages between unipolar full-bridge (UFB)-SMs and half-bridge (HB)-SMs, and unbalanced capacitor voltages between upper and lower arms. A SM grouping-based capacitor precharging strategy is proposed in this paper, which could precharge both UFB-SMs and HB-SMs in upper and lower arms to their nominal voltage, and therefore achieving a smooth startup for the TBL-HMMC based HVDC system. Electromagnetic transient simulation studies using PSCAD/EMTDC tool are conducted to confirm the effectiveness of the proposed strategy.

Continuous-control-set model predictive control (CCS-MPC) has been extensively adopted in dual active bridge (DAB) converters to achieve rapid and precise output voltage regulation. However, the voltage control performance of conventional CCS-MPC exhibits significant sensitivity to parameter variations in DAB system modeling. Discrepancies between model and actual parameters may degrade voltage tracking accuracy. To address this limitation, this paper proposes a continuous-control-set model-free predictive control (CCS-MPC), where an ultra-local data-model for the DAB converter is established and the real-time updates of this data-model is implemented through the Runge-Kutta method, thereby eliminating parameter dependency in output voltage regulation and enhancing system parametric robustness. Experimental results validate the effectiveness of the proposed approach through comprehensive verification.

DC microgrids (DCMG) enable efficient integration of renewable energy systems (RES) and energy storage systems (ESS). However, stability under constant power loads and disturbances remains challenging. Existing studies often overlook how control strategies concretely improve stability. This paper focuses on the dc/dc boost converter within the ESS and investigates how the introduction of a disturbance observer can improve overall system performance. A comprehensive model of the DCMG, including the RES, ESS, and electric vehicle (EV) loads, is established. Control strategies and observer design are presented, followed by a stability analysis using the minor loop gain methods. Simulation results validate the theoretical analysis and demonstrate improved dynamic response and robustness of the overall system.

To overcome the heterogeneous dynamics and unreliable communication which adversely effect the stable control for connected and automated vehicle platoons, a new intelligent control approach, named virtual order-degradation interconnection and damping assignment (VO-IDA), is proposed in this article. First, the internal stability of vehicle platoons is abstracted into a class of tracking control problems for general chained integral systems. By converting the chained integral system into standard closed-loop port-controlled Hamiltonian form, VO-IDA achieves asymptotic tracking through the integration of backstepping order degradation and virtual stabilization control techniques. This conversion effectively eliminates the dependence on preceding vehicular acceleration as well. Second, under heterogeneous dynamics, explicit stable domains of control parameters are provided to ensure the attenuation of string stability for vehicle platoons via Laplace transform. Furthermore, a linear-proportional relationship between heterogeneous and homogeneous dynamics regarding spacing error ratio is uncovered. Leveraging this relationship, a modified multiobjective genetic algorithm is employed to online explore target locations within stable domains, enabling VO-IDA to conduct stable and precise control under heterogeneous dynamics. Comparative experiments verify the superiority of this approach.

In this article, on the basis of an existing dual layer nested (DLN) adaptive sliding-mode control (ASMC) strategy, an observer-based sliding-mode control strategy with an improved DLN adaptive tuning mechanism (IDLN-ASMC) is proposed for a three-level neutral-point-clamped converter. The proposed controller not only ensures good system performance but also mitigates two problems of the existing DLN-ASMC strategy. Meanwhile, three objectives are achieved. First, an adaptive supertwisting algorithm is utilized in the power tracking loop to converge power tracking errors to bounded regions in finite time. Next, a disturbance observer-based IDLN-ASMC strategy is proposed in the dc-link voltage regulation loop to regulate the dc-link voltage to its reference value. Finally, a simple proportional-integral controller is used in the dc-link voltage-balancing loop to reduce the voltage difference between the two dc-link capacitors. The results of simulation and experiment demonstrate the effectiveness and superiority of the proposed strategy.

High penetration of power converters may lead to power ripple, voltage swings, and weak antidisturbances for microgrids. Confronting these issues, this work proposes a robust control scheme, discrete-time super-twisting observer (DSTO)-embedded quasi-integral sliding-mode control (QISMC), for a three-level neutral-point-clamped power converter system, dramatically enhancing power/voltage regulation performance and antidisturbance capability. A fast convergence DSTO is deployed to offset multidisturbances caused by parameter mismatches, unknown loads, current path changes, switch mode noise, and self-compensating power/voltage tracking biases in QISMC. To further mitigate power/voltage steady-state error and boost system robustness, a new quasi-integral sliding-mode surface is built, inherently improving power/voltage tracking performance. Experimental data confirm that the proposed control outperforms the discrete-time extended-state-observer-based QISMC, DSTO-based quasi-sliding mode control, and discrete-time proportional–integral control in power/voltage, grid current harmonics, and robustness.

Phase-shifted pulse width modulation (PS-PWM) is one of the preferred modulation strategies for cascaded H-bridge (CHB) converters due to its excellent harmonic performance. Nevertheless, this modulation strategy needs a fast sampling frequency, which can increase with the number of H-bridge sub-modules (SMs). Moreover, the advantages related to the harmonic content of the output voltages are usually lost for applications that require unbalanced operation conditions regarding SM power or voltage references, such as solar PV or battery energy storage systems. This work proposes a feed-forward compensation technique that reduces the sampling frequency to two times the carrier frequency while maintaining the good harmonic performance of the CHB output voltages. Simulation results are carried out to compare and demonstrate the superior performance of the proposed technique.

This paper is concerned with the controller design for grid-connected inverter facing parameter variation and stochastic perturbation. Considering these two factors, a stochastically perturbed linear parameter varying (LPV) system for the inverter is formulated, upon which the stability analysis and controller synthesis have been conducted. Parameter dependent sufficient conditions have been obtained to guarantee the asymptotical and exponential mean square stability, with which the asymptotical and exponential controllers are designed respectively. A two-level three-phase inverter is used to verify the effectiveness of proposed theories. Simulation results show that both the controllers are effective under parameter variation and stochastic perturbation, and the exponential controller performs better than the asymptotical controller.

In this paper, a disturbance observer based control strategy is proposed to regulate the dc-link voltage of three-phase two-level pulse-width-modulation active-front-end rectifiers. In the voltage regulation loop, a linear disturbance observer is designed to improve the system performance. The load connected to the dc-link capacitor is considered as an external disturbance and the observer is used to estimate its value. The estimated disturbance is compensated to the PI controller. Simulations are carried out to verify the effectiveness and advantage of the proposed control strategy. Three different loads have been provided to test the robustness of the control strategy. Simulation results show that the proposed control strategy improves the transient response of the dc-link voltage, meanwhile maintains the steady-state performance in term of the output current total harmonic distortion, and has strong robustness against the external load variation.

The control of three-phase inverters with output LC filter is of great importance in many applications such as renewable energy, energy storage systems and uninterruptible power supplies, where the generation of sinusoidal output voltages with required amplitude, frequency and lowest harmonic distortion is desired. However, the inevitable parameter uncertainties and disturbances caused by manufacturing tolerance, aging of electrical components and load changes will degrade controller performance, which have always been challenges to traditional model predictive control methods. To deal with these challenges, a data-driven predictive control scheme is proposed in this paper. All unknown parameters and load current can be estimated online with a moving window adaptive observer. The estimation results are used to build a predictive model. Then, predictive control is applied to minimize the error between the output voltage and the reference value. Simulation results verify that the proposed scheme has a better ability to deal with parameter uncertainties and load changes than the traditional model predictive control scheme.

This article proposes a sliding-mode-observer (SMO)-based control strategy to regulate the dc-link voltage for a three-phase two-level active front end (AFE). The SMO is designed for the voltage control loop to estimate the external load which is abruptly connected to the AFE dc-link and consequently causes the dc-link voltage fluctuation. The estimated load value is used to compensate the voltage loop controller, therefore, the voltage loop gains more robustness against the load perturbation and its disturbing effect is greatly reduced. The effectiveness and advantage of the proposed control strategy has been verified through theoretical analysis, simulations, and the real-application experiments conducted on a 5 KVA laboratory AFE. The results show that the proposed control strategy provides obvious improvement of the dc-link voltage control performance comparing with the conventional PI controller and demonstrates stronger robustness against the operating point variations caused by the changes in external load and dc-link capacitance.

The importance of Cascaded H-Bridge (CHB) converters in several applications has led to the introduction of advanced control strategies like Model Predictive Control (MPC). This paper proposes a new adaption of the Optimal Switching Sequence MPC (OSS-MPC) for application in a Single-Phase CHB. The control region of CHB converters is studied in order to apply this new strategy with the objective of tracking grid current and balancing the capacitor voltages of the modules. Another important contribution is the fixed switching period, which is an improvement over other MPC techniques. Starting from the control region, switching sequences are designed considering both switching states and time duration of each state. The method is tested through simulations.

This paper presents voltage regulation and current tracking control strategies for three phase two-level grid-connected power converters. By using power-invariant Park's transformation, an averaged mathematical model of power converters is obtained in dq synchronous reference frame. Then a novel control strategy using adaptive control and H∞technique is proposed to regulate the dc-link output voltage as well as track a desired current reference for three-phase power rectifiers. More specifically, an efficient adaptive controller is established in the external loop for regulating dc-link output voltage in the presence of external disturbances. A set of H∞controllers are designed in the internal loop to force the input currents track their desired values. Finally, simulation results obtained from the proposed control method are presented, analyzed, and compared with that of sliding mode control, and the superiority of the proposed control laws is verified.

In this article, a linear extended state observer (LESO) based second-order sliding mode (SOSM) control strategy with the direct power control is proposed for a three-phase neutral-point-clamped (NPC) power converter connected to a dc microgrid. Comparing with the PI control method, the proposed approach implements the advanced SOSM controller into the voltage regulation loop and instantaneous power tracking loop to enhance the dynamic and steady state performance. Furthermore, saturation function is applied in the SOSM method to weaken the chattering phenomenon. On the other hand, since the dc load is regarded as an external disturbance, an efficient LESO is designed in the voltage regulation loop to reject this disturbance. The design process of the proposed control strategy is shown based on the continuous averaged model of the NPC converter. Finally, comparison experiments among PI, LESO-based PI, and proposed LESO-based SOSM control strategies are implemented, which validate the superiority of the proposed approach.

Flexible power point tracking (FPPT) is control of active power generated by grid-connected photovoltaic power plants (GCPVPPs) to provide various grid-support functionalities, such as frequency response and voltage support. Fast transient response is required during grid voltage and frequency variations. An algorithm, based on dynamic voltage reference design and model predictive control for the dc-dc converter in GCPVPPs is introduced in this paper. The main novelty of the proposed algorithm is fast dynamic response based on the maximum capacity of the system. This feature enables fast FPPT operation in GCPVPPs. The proposed control algorithm results in several features for the FPPT operation, including: higher bandwidth, low power oscillations during steady-state, flexibility for adding constraints based on the operation conditions, and ease of implementation without requiring any complex control parameters tuning and design procedure. The transient performance of the proposed algorithm is evaluated under conditions of voltage sag and frequency deviation. Experimental results are also provided to demonstrate the effectiveness of the proposed algorithm when subjected to rapid changes in PV reference power.

This paper presents an adaptive sliding mode observer (ASMO) to estimate three-phase grid voltage parameters, including both positive and negative sequences of voltage and grid frequency under unbalanced grid faults. First, the dynamic of three-phase voltage is reformulated as the second-order uncertain system, which can transform the traditional phase locked loop problem to the observer design problem. Based on the obtained dynamic system, an ASMO is constructed to estimate three-phase grid voltage parameters, using the adaptive and sliding mode techniques. The stability of the overall system including the observer estimation errors, sliding variable and adaptive estimation errors is rigorously proved by Lyapunov stability theory. The performance of proposed observer is assessed for estimation of three-phase grid voltage parameters by simulation in which two types of faults, i.e., the amplitude of voltage and grid frequency variations. are considered.

Reduction of switching losses in power converters is especially important for very high power applications looking for improving the reliability and efficiency. In contrast to carrier-based modulations, selective harmonic elimination and mitigation techniques use optimal waveform computation to generate a fundamental component while managing voltage harmonic content. However, these techniques, and specially selective harmonic mitigation, impose a high non-linear set of expressions to be solved. Therefore, complexity and computational burden rise up. Meta-heuristic algorithms are commonly used to solve the mathematical optimization problem involved. Preliminary application of Exchange Market Algorithm for harmonic mitigation problem has already been presented. However, in this paper a redefinition of the optimization is proposed to consider harmonic content for a wider range of frequencies. Results from computation for a wide range of modulation index are presented.

Nowadays, the design of power converters has been focused on the optimization in terms of reliability, fault-tolerant capability and power density. The use of modular converters leads to natural fault-tolerant capability because the power system can be still operating even when some module has failed. In this paper, the reliability of modular converters, which is high-dependent of several factors like as thermal stress, is studied. In the paper, the power devices aging of dc/dc interleaved power converters is managed. The proposed method is based on sharing conveniently the total managed power between the power modules. This can be done without losing performance in the power system. The proposed power routing technique has been tested in a three-module interleaved boost converter which is used in multiple applications.

This paper proposes an effective method to control the modular multilevel converters (MMC). The whole control scheme can be divided into three stages. Firstly, the prediction technique is employed to derive a quadratic programming problem from a cost function, leading to the voltage reference for each arm of the MMC. Secondly, the simple nearest level control is adopted to get the number of on-state SMs for each arm. At last, within each arm the submodules (SMs) are selected based on the sorting results of their capacitor voltages. Simulation based on a three-phase grid connected MMC system is conducted to evaluate the effectiveness of the proposed method. The results show that the proposed technique is capable of tracking the output current reference with very low distortion, while the SM capacitor voltages are well balanced and the circulating currents are almost suppressed. The transient response is fast and accurate as well.

This paper presents a novel control scheme for DC-DC boost converter, maintaining the desirable voltage regulation performance under high load variation and large change of voltage reference. The model of converter is reformulated, in which the unknown equivalent load, input voltage, model uncertainties and unmodeled dynamics are lumped as external disturbance. The control strategy is designed with backstepping control technology, similar to the cascade control method in which the intermediate variable is introduced to fast respond the control demand, effectively dealing with the nonlinearity of the boost converter dynamics. The disturbance observers are established to estimate the lumped disturbances, rejecting disturbances and removing steady-state errors to improve the closed-loop performance. The simulation results demonstrate that the proposed control strategy, backstepping control combined with disturbance observer, provides lots of advantages superior to the conventional PI control such as faster dynamic response and less output voltage drop.

A new approach to the control of three-phase two-level grid-connected power converters is proposed in this paper. The proposed control is an extended state observer (ESO)based second order sliding mode (SOSM), which comprises two control loops: the outer loop is a voltage regulation loop, as well as inner loop is an instantaneous power tracking loop. The outer loop is accomplished by an H∞controller plus an ESO, which is designed to regulate dc-link capacitor voltage of the converter and asymptotically reject external disturbances and parameter perturbations. The SOSM strategy is employed in the inner loop to drive the active and reactive power convergence to their desired values. Control objectives of nearly unity power factor and dc-link capacitor voltage regulation are simultaneously satisfied. Availability of the ESO-based SOSM is compared with the classic proportional-integral control in simulations, and the comparison implies that the proposed strategy not merely achieves an almost perfect tracking performance, but also provides a complete robustness against resistance load variation.

This paper presents a comprehensive overview of power converters and their control techniques for AC microgrids. The aim is to give an insight and direction for researchers and applications on promising topologies, control, and application within future smart grid. The paper first focuses on presenting various power converter topologies used in AC microgrids. Then, suitable control techniques for grid-connected and islanded operation modes are critically reviewed and analyzed. Finally, challenges of these converter topologies and control techniques are identified along with their potential solutions.

This paper employs second-order sliding mode control (SOSMC) to carry out the current tracking and voltage regulation tasks of a grid-connected three-phase two-level power converter. For dc-link voltage regulation, a disturbance observer is adopted to improve the whole control performance. In this paper, four different types of disturbance observers are proposed for comparison, which are conventional linear observer (LINO), second-order sliding mode observer (SOSMO), linear extended state observer (LESO) and nonlinear extended state observer (NESO). To ensure fair comparison, the parameters of the observers are tuned to make the power converter achieve almost same current total harmonic distortion (THD) and steady error of dc-link voltage. The performances are compared in the term of transient response of the dc-link voltage. The simulation results show: first, the disturbance observers improve the control performance of SOSMC; second, SOSMO outperforms the other three observers.

The search of efficient, robust and fault-tolerant electronic power converters is a challenge for the industry and academia. Nowadays, the integration and exploitation of the renewable energy sources and energy storage systems is required. In these terms, the multilevel power converters and specifically the cascaded H-bridge (CHB) power converter is a very good candidate. However, if a CHB power converter operates under an unbalanced operation a low-frequency high-distortion content appears in the output voltage spectrum. In order to reduce this problem, an extra cell, equipped with a low voltage battery or supercapacitor, is added to the original CHB converter. The idea is to operate the extra cell with the convenient duty cycle value in order to eliminate the low-order harmonic distortion generated by the unbalanced operation. This makes the proposed method very interesting because it leads to a reduction of the grid connection filter.

Multilevel power converters are very attractive for medium- and high-voltage applications because they present some advantages compared with the traditional two-level converters. In this way, the multilevel technology is backed by the industry and academia support. Among multilevel converters, the modular multilevel converter (MMC) is very popular because it is well-suited for the high-voltage dc (HVDC) power transmission systems as well as it permits the connection of different nature ac grids. To operate the MMC power converter is required a proper modulation strategy. It can be based on carrier-less or pulse-width modulation (PWM) strategies. In order to determine the optimum modulation technique, several simulations have been performed in order to extract some conclusions related with the power losses and the power converter behavior.

The modular multilevel converter (MMC) is considered among the top choices for very high-power applications due to its superior features. To operate with good performance, effective control and modulation techniques are required to suppress the detrimental effects, including the circulating current and the capacitor voltage ripples. This paper proposes an efficient variable nearest level control-model predictive control (VNLC-MPC) technique. With few control actions to evaluate at each controller sampling period, the proposed method can achieve high controllability of the converter output current and power with reduced computational burden. Simulations are carried out on a three-phase MMC-based power system. The simulation results validate the VNLC-MPC strategy achieving higher quality of output current waveforms, reduced circulating currents and smaller capacitor voltage ripples.

In this paper, a novel scheme of disturbance observer based second order sliding mode (SOSM) control for DC-DC buck converters is proposed. A cascade-control structure is established to regulate the output voltage and force the inductor current to track its reference, which comprises two control loops. The voltage regulation loop which is based on an SOSM controller combined with extended state observer (ESO) is the external loop. The current tracking loop also accomplished by SOSM controller is the internal loop. The fast motion is dominated by the dynamics of the current tracking loop whereas the slow motion stems from the dynamics of the output voltage. In addition, the load resistance that influences significantly the dynamics of whole system is regarded as the external disturbance in this papper. A disturbance observer, ESO, aims at asymptotically rejecting disturbances to converter. The proposed control strategy is verified using simulation test.

In the last decades, multilevel converters have been developed usually for medium-voltage high-power applications. They have become a mature solution for the increasing power demand of multiple applications such as renewable energy systems, power quality improvement, and motor drives. In this paper, the operation of multilevel converters is addressed focusing on control and modulation techniques for different well-known applications. The new developments are presented as an extension of conventional methods for two-level voltage-source converters which are still the mainstream solution for most cases.

The use of interleaved power converters is a mature solution for multiple applications where the power is shared between several power converters. The interleaving method is used in order to improve the quality of the total output current. However, the performance of the complete power system is poor if an unbalanced operation is present in each power converter. In this paper, a variable-angle interleaving method is presented where the angle to be applied to carry out the interleaving is not fixed, but it is variable and calculated in real time depending on the operational conditions of the overall system. Simulation results are presented in order to demonstrate the good performance of the proposal.

In this work, a Finite Control Set Model Predictive Control (FCS-MPC) strategy for Cascaded H-bridge (CHB) inverters is proposed. The key novelty of our proposal comes from the way the cost function is designed. Generally, in standard FCS-MPC formulations for power converters, the cost function only considers the current tracking error. In this proposal, the proposed cost function also takes into account the control input tracking error. This allows one to obtain a reduced common-mode voltage during the steady-state while achieving a fast dynamic response during transients, similarly to the one provided by standard FCS-MPC. To account for calculation time, a fast-optimization algorithm based on sphere decoding is also considered. To verify the performance of the proposed predictive strategy, simulation results for a three phase five-level CHB inverter governed by the proposed FCS-MPC are presented.

Among multilevel converters, the cascaded H-bridge topology is one of the most industrially accepted solution for multiple applications, mostly for motor drives and flexible AC transmissions systems. Besides, other applications are being considered taking advantage of its modularity. The conventional phase-shifted PWM is the common method to generate the power devices switching of the converter. However, the performance is poor when an unbalanced operation is present. In this paper, an adaptive modulation method is presented where the angle to be applied to the phase-shifted PWM modulator is not fixed, but it is variable and calculated in real time depending on the operational conditions. Some simulation results are presented in order to demonstrate the good performance of the system.

In this paper, a model based robust control for three-phase three-level Neutral Point Clamped (NPC) power converters is studied. Based on the continuous averaged model of the system, a Second Order Sliding Mode (SOSM) technique is employed to the control design. The control objectives are to achieve desired dc-link capacitor voltage regulation, voltage balance in the two dc-link capacitors and the instantaneous active and reactive power tracking. In order to achieve fast dynamic response of the proposed controller in the presence of external disturbances, an Extended State Observer (ESO) is employed to asymptotically reject the disturbances which are integrated in the controller design. The proposed control strategy has a cascaded structure which consists of power tracking (inner loop) ESO-based dc-link voltage regulation and capacitors voltage balance (outer loop). Multi-rate simulation illustrates the effectiveness and robustness of the proposed controller under parametric uncertainties and load variations.

The integration of renewable energy systems and specifically of solar photovoltaic (PV) systems into the grid has become an important issue in the last decade because of the huge expansion of new power plants. PV systems have experienced an important evolution in the overall efficiency and in the variety of locations from low power installations (PV roof systems in domestic and residential applications) to high-power power plants currently reaching up to 550 MW. This fact has led to the appearance of new PV converter topologies and, among them, multilevel converters are very attractive due to its good features such as high nominal power and high quality of output waveforms. In this paper, a multilevel cascaded H-bridge converter is used to directly integrate the PV arrays into the grid. The proposed controller implements independent MPPT algorithms for each H-bridge extracting all the possible power from the available irradiation. Simulation results are presented to demonstrate the good performance of the PV system. The proposed system is modular and can be easily scaled to reach higher power so it could be used in large PV plants just adding extra H-bridges to the converter.

The phenomenon of control input saturation due to limitations in the duty cycles of the gate pulses of the power switches is an important issue in the performance of power electronic converters. This paper formulates and analyzes the control input saturation effects in a three-phase three-level neutral-point-clamped converter connected to the grid. Particularly, the phenomenon is studied when a direct power control strategy is implemented as an indirect control through a space vector modulation technique. The discrete set of values of the gating signals defines the power converter control region. Due to the modulation strategy, which is introduced to generate the switching sequence, any point located inside the control region is physically implementable. However, the points situated out of this area can not be generated because they represent duty cycles higher than 100%, leading to a saturation scenario. In this paper, several strategies are studied in order to cope with the saturation problem and obtain the final gating signals. The performance of the power converter under these different approaches is evaluated by means of simulation results in PSCAD©environment.

This work presents the design and experimental validation of a Model Predictive Control (MPC) strategy for a Voltage Source Inverter (VSI) used in a three-phase uninterruptible power supply (UPS) for critical loads. The solution is obtained in two steps: first an unconstrained MPC problem is solved, which computes the continuous values of the voltage that must be provided by the converter. Then, a PWM modulation scheme is used to define the switching sequence of the switches that generate the desired input voltage to the LC filter. The first stage implies a dynamic optimization while the second one is just a static relationship. The solution of the unconstrained MPC problem gives rise to an explicit control law that can be computed beforehand, allowing the prediction horizon to be easily extended. This can improve the performance of other MPC formulation that use very short prediction horizons. The effect of the length of the prediction horizon and the control-weighting factor over the system performance is also evaluated experimentally in the paper. This study addresses how these parameters should be tuned to minimize the error between the actual and the desired output voltage. The proposed control strategy has been tested on a UPS supplying a three-phase RL load. The experimental results show that the proposed MPC controller achieves high performance of the overall system, even in the case of a model mismatch.

In this work, a Model Based Adaptive Direct Power Control (MB-ADPC) with constant switching frequency for Three-Phase Three-Level Neutral Point Clamped (3L-NPC) converters is proposed. The rectifier and inverter operation mode are used to illustrate the flexibility of the proposed MB-ADPC controller. The control design process is based on the continuous averaged model of the system. Depending on the operation mode different control objectives have to be guaranteed. The proposed controller ensures the voltage regulation of the dc-link capacitors for the rectifier operation mode and to achieve voltage balance in the dc-link capacitors and the active and reactive power tracking for the rectifier and inverter operation modes. In addition, adaptive techniques are used to avoid system parameters uncertainties as smoothing inductors and grid frequency values. This work shows that the application of advanced control strategies based on the system model allows enhancing the performance of the overall system. The details of the controllers design process and the experimental results using a 50 kVA Three-Phase Three-Level NPC prototype are presented in this paper validating the proposed controllers.