An Overview of Applications of the Modular Multilevel Matrix Converter

The modular multilevel matrix converter is a relatively new power converter topology suitable for high-power alternating current (AC)-to-AC applications. Several publications in the literature have highlighted the converter capabilities, such as full modularity, fault-redundancy, control flexibility and input/output power quality. However, the topology and control of this converter are relatively complex to realise, considering that the converter has a large number of power-cells and floating capacitors. To the best of the authors’ knowledge, there are no review papers where the applications of the modular multilevel matrix converter are discussed. Hence, this paper aims to provide a comprehensive review of the state-of-the-art of the modular multilevel matrix converter, focusing on implementation issues and applications. Guidelines to dimensioning the key components of this converter are described and compared to other modular multilevel topologies, highlighting the versatility and controllability of the converter in high-power applications. Additionally, the most popular applications for the modular multilevel matrix converter, such as wind turbines, grid connection and motor drives, are discussed based on analyses of simulation and experimental results. Finally, future trends and new opportunities for the use of the modular multilevel matrix converter in high-power AC-to-AC applications are identified.Agencia Nacional de Investigación y Desarrollo/[Fondecyt 11191163]/ANID/ChileAgencia Nacional de Investigación y Desarrollo/[Fondecyt 1180879]/ANID/ChileAgencia Nacional de Investigación y Desarrollo/[Fondecyt 11190852]/ANID/ChileAgencia Nacional de Investigación y Desarrollo/[ANID Basal FB0008]/ANID/ChileAgencia Nacional de Investigación y Desarrollo/[Fondef ID19I10370]/ANID/ChileUniversidad de Santiago/[Dicyt 091813DD]//ChileUCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería Eléctric

Small-Signal Modelling and Stability Assessment of Phase-Locked Loops in Weak Grids

This paper proposes a low-complexity small signal model for a 3-leg converter connected to a balanced three-phase, three-wire weak grid and synchronised to this grid using a PLL implemented in a synchronous rotating d-q axis. A thorough analysis of the system stability as a function of the PLL bandwidth and the short circuit ratio (SCR) of the grid is performed based on a linearised model. By using the proposed model, an improved design process is proposed for the commonly used dq-PLL that accounts for the potential stability issues which may occur in weak grids. Using the proposed approach, it is possible to optimise the PLL design to find the fastest PLL that can operate stably considering the SCR of the grid. In addition, the proposed model is very simple, resulting in a straightforward design tool that could also be used for online stability monitoring. The method is validated through simulations and experimental results from a 5kW laboratory system

A novel Capacitor Voltage Balancing strategy for Modular Multilevel Converters

This paper presents a simple and innovative Capacitor Voltage Balancing (CVB) strategy for Modular Multilevel Converters (MMC) based on full H-bridge cell topologies. The method computes specific modulation indexes for each cell using the explicit solution of an underlying optimal control problem. Based on the structure of its analytical solution, the proposed CVB scheme is integrated to a Phase-Shifted PWM scheme with an easy implementation. Experimental results obtained from a nine-cell single-phase converter demonstrate an improved performance of the proposed method, especially under transient operating conditions

A Novel Control System for Medium-Voltage Hexverter-Based Drives

In this paper, a novel control system for the Hexverter-based drive is proposed and analysed. Unlike previously proposed control schemes, the proposed one does not require the information of the machine variables to regulate the converter floating capacitors, as required in high-performance drive applications. The feasibility of the proposed control system is demonstrated by using simulation results of an Hexverter-based drive driving a medium-voltage machine, including the whole frequency range and high starting torque loads.Universidad de Costa Rica/[322-B9-242]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería Eléctric

Cooperative regulation of imbalances in three-phase four-wire microgrids using single-phase droop control and secondary control algorithms

Collaborative control of power converters operating in microgrids with unbalanced single-phase loads is difficult to achieve, considering that the voltages and currents have positive-, negative-, and zero-sequence components. In this paper, a new control scheme for collaborative control of four-leg microgrids is proposed. The main advantage of the proposedmethodology is simplicity, because the sharing of the powers produced by the positive-, negative-, and zero-sequence voltage and currents is simple to achieve using the easy to implement and well-known droop control algorithms, i.e., as those based onP-. andQ-v droop control. The proposed droop algorithms do not require high bandwidth communication channels and the application of virtual impedances, whose design usually demands extensive simulation work, is not required. Three secondary control systems are also analyzed, discussed, and implemented in this paper to regulate the frequency, voltage, and phase at the point of common coupling (PCC), to achieve a balanced 50-Hz three-phase voltage supply in the PCC during steadystate operation. For these secondary control systems, single-phase phase-locked loop based on quadrature signal generators are implemented. Small signal modeling and design are discussed in this paper. A microgrid prototype of similar to 5 kW, implemented using two power converters of 3 kW(each), is used to experimentally validate the proposed algorithms.Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1170683 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT PIA/BASAL FB0008 CONICYT-PIA-FB0816 CONICYT-PCHA/Doctorado Nacional/2017-2117185

Model-predictive-control-based capacitor voltage balancing strategies for modular multilevel converters

This paper presents two capacitor voltage balancing (CVB) strategies for modular multilevel converter (MMC) applications. Both balancing schemes are based on model predictive control and are designed to efficiently solve a constrained optimal control problem, where the predicted capacitor voltage errors are included in the cost function with the demanded output voltage of a cluster being forced through an equality constraint. The first method proposed in this paper computes specific modulation indexes for each module using the explicit solution of a relaxed version of the original optimization problem. The second approach proposed in this paper reduces the complexity of the original problem by linearizing the objective function and using an optimal sorting network based on a greedy algorithm to solve this approximation. Considering the structures of both solution approaches, they are integrated into modulation schemes based on phase-shifted and level-shifted pulsewidth modulation algorithms, respectively. Experimental results obtained from a nine-cell single-phase MMC prototype demonstrate the good performance achieved with the proposed methodologies, as well as the implementation simplicity offered by the proposed CVB algorithms

Particle-filtering-based prognostics for the state of maximum power available in lithium-ion batteries at electromobility applications

Nowadays, electric vehicles such as cars and bicycles are increasing their popularity due to the rising environmental consciousness. The autonomy required by these means of transport has marked a significant and steady growth in the development of battery technologies. In this sense, it is crucial to estimate and prognosticate critical parameters of battery packs such as the State of Charge (SOC), the State of Maximum Power Available (SoMPA), and the Failure Time. All these indicators are relevant to determine if both the energy stored in the battery of electric vehicles and power specifications are sufficient to successfully complete a required route, avoiding battery preventive disconnection before arrival. In this regard, this paper presents a novel approach to estimate and prognosticate the SOC and SoMPA of Lithium-Ion batteries in the context of electromobility applications. The proposed method uses the formulation of an optimization problem to find an analytical relationship between the SOC and the SoMPA; whereas the battery pack is modeled in terms of both the polarization resistance and the SOC. Particle filtering algorithms are used to compute online estimates and prognostic results, while the characterization of the usage profile of the battery bank is achieved using probability-based models (Markov chains). The problem of battery monitoring for an electric bicycle is used as a case study to validate the proposed scheme, when driven in flat and sloped routes to generate different usage profiles. It is demonstrated that the proposed methodology allows to successfully prognosticate both SOC and SoMPA when the future discharge current profile is characterized in terms of probability-based models.Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1170044 Advanced Center for Electrical and Electronic Engineering, AC3E, Basal Project, ANID FB0008 University of Costa Rica CONICYT-PCHA/Doctorado Nacional 2015-21150121 2016-21161427 2014-21140201 Universidad Tecnológica de Panamá IFARHU (Grant for Doctoral Studies) SNI-SENACYT Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1170683 ANID PIA/BASAL AFB18000