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A multiscale electrothermal simulation approach is presented to optimize the design of a hybrid switch soft-switching inverter using a library of dynamic electrothermal component models parameterized in terms of electrical, structural, and material properties. Individual device area, snubber capacitor, and gate drive timing are used to minimize the total loss of the soft-switching inverter module subject to the design constraints including total device area and minimum on-time consideration. The proposed multiscale electrothermal simulation approach allows for a large number of parametric studies involving multiple design variables to be considered, drastically reducing simulation time. The optimized design is then compared and contrasted with an already existing design from the Virginia Tech Freedom Car Project using the generation II module. It will be shown that the proposed approach improves the baseline design by 16% in loss and reduces the cooling requirements by 42%. Validation of the electrical and thermal device models against measured data is also provided. [ABSTRACT FROM AUTHOR]

As wind power technology points to increase power ratings, the implementation based on a permanent-magnet synchronous generator (PMSG) with a full-power converter is expanding its market share. Multilevel converters, as for example, neutral-point clamped (NPC) converters, are therefore well suited for this application. Predictive current control presents similar dynamic response and reference tracking than other well-established control methods, but working at lower switching frequencies, and providing extensive flexibility to apply either online or offline different control laws to the same plant. In this work, the predictive current control is applied to both sides of the back-to-back NPC converter connecting a permanent-magnet synchronous wind power generator to the grid. DC-link neutral-point balance is achieved by means of the predictive control algorithm, which considers the redundant switching states of the back-to-back NPC converter. Reduced number of commutations, current spectrum control, and compliance with the low-voltage ride-through (LVRT) requirement are carried out with the predictive control. The obtained experimental results confirm the suitability of the proposed control approach. [ABSTRACT FROM PUBLISHER]

The predictive control method deals with the prediction of the motor behavior based on a mathematical model of the motor. This model is dependent on the motor parameters. However, these parameters may not match with their actual values due to the measurement error or they may change during the operation of the motor. All these uncertainties and model inexactitude lead to inaccurate prediction of the motor behavior and deteriorate the performance of the predictive algorithm. This paper presents an extension of the predictive current control (PCC) method to improve the prediction accuracy for a permanent-magnet synchronous motor (PMSM). The proposed strategy not only reduces the current ripple but also improves the robustness of the system against parameter uncertainties. Simulation and experimental results that confirm the good performance of the proposed method are presented. [ABSTRACT FROM PUBLISHER]

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future. [ABSTRACT FROM PUBLISHER]

In this paper, the experimental validation of a predictive current control strategy for a four-leg indirect matrix converter is presented. The four-leg indirect matrix converter can supply energy to an unbalanced three-phase load while providing a path for the zero sequence load. The predictive current control technique is based on the optimal selection among the valid switching states of the converter by evaluating a cost function, resulting in a simple approach without the necessity for modulators. Furthermore, zero dc-link current commutation is achieved by synchronizing the state changes in the input stage with the application of a zero-voltage space vector in the inverter stage. Simulation results are presented and the strategy is experimentally validated using a laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper presents a finite control set model predictive strategy and its application to the load voltage control of two-level four-leg inverters. The proposed approach uses the novel discrete-time model of the inverter and output $LC$ filter in order to predict the variables to be controlled. These predictions are carried out for the 16 switching states of the inverter and are evaluated using a cost function. The switching state that forces the load voltages to be closest to their respective references is chosen and applied to the inverter. The behavior of the predictive controller has been investigated, and the changes to both inductive and capacitive filter parameters have been considered. In order to improve the reliability of the fourth leg as well as the overall inverter efficiency, a solution is proposed, which combines hardware and software reconfigurations. The feasibility of the proposed method is verified through simulation and experimental results considering single-/three-phase, balanced/unbalanced, and linear/nonlinear loads. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized multilevel direct power control (ML-DPC) scheme for grid-connected multilevel power converters. The proposed method extends the original DPC operating principle by considering only the closest subset of two-level voltage vectors to the present switching state. The implementation of this principle requires the power derivatives for feedback, which can present numerical problems when applied experimentally, mainly due to high measurement noise sensitivity. Therefore, a derivative estimator is proposed based on the converter-grid model in the synchronous reference frame. In addition, a virtual flux observer is developed to achieve synchronization and improve robustness in the presence of grid voltage harmonics. The proposed method is applicable to any multilevel converter topology of any number of levels. In this paper, simulations and experimental results are presented for a seven-level cascaded H-bridge converter. [ABSTRACT FROM AUTHOR]

Three-level active neutral-point-clamped (NPC) (ANPC) (3L-ANPC) voltage-source converters (3L-ANPC VSCs) offer three additional switch states and an increase of commutations by a factor of four, compared to the three-level NPC voltage-source converter. This paper presents, for the first time, a detailed analysis of all 3L-ANPC VSC commutations using high-power 5SHY55L4500 integrated gate-commutated thyristors. Starting with a description of the switching states and commutations, a new 3-kV 5-kA medium-voltage 3L-ANPC testbench is described. To verify the function of all commutations, this paper derives suitable switching sequences and analyzes the commutations and switching transients in detail for dc-link voltages of 2.13–2.43 kV and load currents of 3.95–4.36 kA. The experimental investigations show that, although the ANPC commutations substantially differ from NPC commutations, the ANPC commutations do not present critical operating conditions for the power semiconductors or the converters. Thus, all 32 ANPC commutations can be applied in a new medium-voltage converter realization. [ABSTRACT FROM PUBLISHER]

While the classical control techniques for three-phase two-level four-leg inverters are based on pulsewidth modulation or 3-D space vector modulation, this paper presents a simple digital current control strategy without the modulation stage. The proposed controller uses the discrete nature of the four-leg inverter and filter to generate the switching states. Using a predictive cost function, the optimal switching state to be applied in the next sampling interval is selected. The proposed controller offers excellent reference tracking with less current harmonic distortion for balanced and unbalanced loading conditions. The feasibility of the proposed strategy is verified by digital implementation on a dSPACE DS1104-based rapid prototype platform. [ABSTRACT FROM PUBLISHER]

In this paper, a simple model predictive current control strategy is proposed for four-leg inverters to deliver power to the (un)balanced/(non)linear loads. Unlike classical control schemes, the proposed method does not require current PI controllers or a complex modulation stage. The discrete-time model of the inverter, filter, and load are used to predict the future behavior of the load currents for each of the 16 possible switching states. The control method chooses a switching state that minimizes the error between the output currents and their references. The performance of the proposed method has been investigated for perturbations in the filter and load parameters. The neutral-leg switching frequency reduction algorithm is also proposed to improve the efficiency of the converter. The feasibility of the proposed method is verified in this first part, through simulation results. [ABSTRACT FROM PUBLISHER]

Finite-states model predictive control is a rising alternative in the control of power converters and drives. Successful application to different topologies and applications such as two-level voltage source inverters, neutral-point-clamped and cascaded H-bridge inverters, and matrix converters has shown its potential in power converters. However, when multiple control objectives are desired, weighting factors are required to appropriately select the switching states. The selection of these factors is a time-consuming and complex task. In this work, the standard selection stage is replaced by a fuzzy decision-making strategy, considering, as a case study, the control of both load and supply currents in the direct matrix converter (DMC). As a result, weighting-factor selection is avoided, and a simple selection scheme is obtained for this application. In addition, a more natural design approach to the state selection is opened for other applications. Simulation and experimental results are presented to validate the approach in an experimental DMC prototype. [ABSTRACT FROM PUBLISHER]

Matrix converters (MCs) are a very attractive alternative to conventional back-to-back converters with dc links. In this paper, a performance comparison between the well-established space vector modulation (SVM) technique and model predictive control (MPC) is presented for the current regulation in a direct MC. Both methods are analyzed and contrasted through simulation and experimental results. In order to establish their strengths and weaknesses, the assessment is made by measuring and comparing output and input currents and voltages with the same voltage source and load current conditions. Our results show that MPC is simpler than SVM from a conceptual point of view and provides better source current behavior, particularly with a distorted source voltage. [ABSTRACT FROM PUBLISHER]

Multilevel cascaded H-bridge converters have found industrial application in the medium-voltage high-power range. In this paper, a generalized modulation technique for this type of converter based on a multidimensional control region is presented. Using the multidimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feedforward version of this technique is also introduced to determine the switching sequence and the switching times, avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts. [ABSTRACT FROM AUTHOR]