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The constant growth of distributed energy resource (DER) in the electric power system (EPS) is a reality on account of some aspects, for example, technical, financial, environmental. The insertion of DERs can be positive, providing ancillary services, for example, harmonic mitigation, or negative, causing overvoltage, depending on the proper control and the characteristics of the grid. This paper proposes a pq‐based control strategy for distributed generation, wherein the studied system is composed by a photovoltaic DER and a three‐phase converter for processing the generated power and providing ancillary services (ASs) to a three‐wire EPS. The power control is based on the power balance between the grid and the converter. Besides supplying active and reactive power, the proposed strategy can provide ASs by controlling the grid currents from a pq transformation. Some advantages over other solution can be mentioned, such as reduced sensor number and instantaneous control response. In addition, neither additional harmonic‐extraction method nor a phase‐locked loop is required. To validate this study and theoretical considerations, simulation results are presented and evaluated. From tests in a downscaled laboratory setup, experimental results are also presented to verify the effectiveness of the proposed control strategy.

This article proposes four converters for interfacing a single dc power source and loads of a single-phase three-wire system. The topologies of the proposed converters are based on two-level (2L) and three-level neutral point clamped (NPC) legs. For regulating the dc-link capacitors of the NPC-based converters, a dc-link voltage-balancing technique is proposed to balance the neutral-point voltage using the space-vector pulsewidth modulation, considering the harmonic distortion of the output voltages and the semiconductor losses from an algorithm that defines the vector sequences to be applied. These characteristics make the proposed converters suitable for applications in microgrid employing dc distributed energy resources or ac power supply by adding ac–dc stage. The proposed converters are compared to a conventional 2 L converter from simulated results for evaluating the semiconductor losses in balanced and unbalanced load scenarios. Experimental results are presented to verify the effectiveness of the proposed voltage-balancing technique and to validate the converters.

This paper proposes two hybrid asymmetric cascaded multilevel inverters for driving medium-voltage open-end winding motors. Each phase of the proposed systems consist of a three-level (3L) H-bridge cell and a nine-level (9L) H-bridge cell connected in series. An unequal dc-voltage ratio of 1:8 between cells is used, providing 19 phase voltage levels. The topologies of the 9L H-bridge cell are based on modular multilevel cascade converter (MMCC) with double-star chopper cells, while the 3L H-bridge cell is fed by a floating capacitor. Compared to conventional MMCC for open-end stator winding motor drives, the proposed inverters can produce more phase voltage levels. In addition, they require a smaller number of power semiconductor switches, drivers and capacitors. Simulations and experimental results are presented in order to demonstrate the performance and feasibility of the proposed topologies.

This paper presents a multilevel ac-dc single-phase converter with cascaded transformers and two dc links. The configuration is composed by k cascaded transformers, which isolate the load from the power source, and 2(k + 1) two-level (2L) legs, in which some insulated-gate bipolar transistor (IGBT) legs can be replaced by diode legs if bidirectional operation is not required. The cascaded transformers have different turns ratio characterizing as an asymmetric configuration. In addition, the second dc link is used to increase the number of voltage levels, which results in better input voltage quality. This dc link has a lower voltage and can be a floating capacitor. The proposed configuration is compared with a conventional configuration. Simulation and experimental results are shown to demonstrate the feasibility of the system.

This paper presents two universal active power filters (UAPFs) configurations using single-phase four-leg ac–dc–ac converters. The proposed topologies are used for disturbance compensation in the power supply, such as voltages sags/swells, and to compensate harmonic distortions in the current. The operation of the proposed configurations is compared with the conventional single-phase four-leg UAPF. The harmonic distortions, semiconductor losses, and average switching frequency are used as comparison parameters. Compared to the conventional configuration, the proposed topologies use a transformer with lower power, provide lower average switching, and reduced current total harmonic distortion (THD) and voltage weighted THD. The pulsewidth modulation (PWM) strategy was designed based on a space vector modulation technique, and a control system for the grid current and dc-link bus voltage regulation was also developed. Simulation and experimental results are presented showing the efficiency of the PWM and control strategies and validating the proposed topologies.

A implantação dos sistemas de armazenamento de energia por baterias tem crescido junto ao sistema elétrico, principalmente, com o advento das redes elétricas inteligentes e integração de geração distribuída por fontes renováveis. Frente às diferentes possibilidades de aplicação e diversidade de tecnologias das baterias, a sistematização do processo de seleção mostra-se fundamental. Nesta conjuntura, este artigo propõe o uso de um processo hierárquico analítico pela aplicação do método AHP (Analytic Hierarchy Process) para tomada de decisão na seleção de tecnologias de baterias. O procedimento desenvolvido com método AHP promove a avaliação de características técnico-econômicas por meio de indicadores quantitativos e qualitativos estabelecendo critérios e prioridades para comparação e hierarquização destes atributos. Os resultados obtidos demonstram a objetividade do método, sua coerência com o desenvolvimento tecnológico atual das baterias e sua abrangência de aplicação devido à base de conhecimento construída, além de não exigir informações específicas do sistema de armazenamento a ser implantado.

Este trabalho apresenta uma análise abrangente de modelo e controle de um sistema de conversão de energia como interface de recurso energético distribuído (distributed energy resource) (DER) para suporte à rede elétrica. Nesta aplicação, o sistema de conversão, com a estratégia de controle, deve responder de forma rápida e robusta para adequar as variações e intermitências dos DERs aos padrões normativos da rede, controlando instantaneamente potência ativa e reativa. Portanto, o sistema é composto por um conversor ponte ativa dupla (dual-active bridge) (DAB) como estágio adicional para regulação de tensão do barramento do conversor CC-CA, o qual é conectado a rede elétrica. Na implementação da estratégia de controle, avaliou-se a contribuição do emprego do controlador integral-proporcional como alternativa ao convencional proporcional-integral, tanto na regulação da tensão de saída do conversor DAB como no controle das potências instantâneas. Simulações foram realizadas e os resultados foram avaliados para validar as considerações teóricas.

This paper presents a single-phase to single-phase three-wire converter, which comprises a conventional two-level(2L) four-leg converter in series with H-bridge. The H-bridges are supplied from the main converter by means of a DC-DC converter with a high-frequency transformer. The proposed converter: (i) can supply three loads, wherein two are phase voltages 180 degrees-lagged, and a third load with twice the amplitude of the phase voltage, (ii) has the output voltages with constant frequency and amplitude even under unbalanced loads, and (iii) has sinusoidal grid current and high-power factor even supplying nonlinear loads. In this way, the proposed system is suitable for uninterruptible power supply. Furthermore, the pulsewidth modulation (PWM) technique is proposed to generate the pole voltages of the converters, so that the output voltages have better power quality. The proposed converter is compared with a conventional 2L in terms of harmonic distortion. Simulated results are provided to verify the operation of the proposed system.

This paper presents a hybrid single-phase to single-phase three-wire converter, using two-level and three-level neutral-point clamped (NPC) legs. The converter can supply two loads, 180 lagged from each other, with sinusoidal waveform and constant amplitude and frequency, even with nonlinear or unbalanced loads. Moreover, the converter can supply a third load with twice the amplitude of the phase voltage. Also, the converter provides sinusoidal grid current and unity power factor. Furthermore, the pulsewidth modulation (PWM) technique and the control strategy are discussed and implemented. Simulation and experimental results are provided to illustrate and compare the operation of the proposed systems.

This paper presents three single-phase three-wire converters. One converter is composed of three three-level-based legs, and the others are hybrid converters using three-level-based and two-level-based legs. The converters can supply two loads, 180 degrees lagged from each other, with sinusoidal waveform and constant amplitude and frequency, even with nonlinear or unbalanced loads. Furthermore, the pulsewidth modulation (PWM) technique is discussed and implemented. Simulation and experimental results are provided to illustrate and compare the operation of the proposed systems.

In this paper is presented the modeling of a twelve-phase induction machine considering the flux space harmonics and the analysis of time harmonic injection. It is shown that from the fundamental up to the eleventh harmonics it is possible to produce dc torque, therefore, improving the torque density of the drive system. It is presented the machine dynamical model, the steady state analysis and a set experimental results.

A tecnica de injecao de harmonicos pode proporcionar a um sistema eletromecânico um ganho de conjugado em uma maquina com um numero maior de fases em seu estator, assim, deixam de serem necessarias maquinas trifasicas de dimensoes maiores para suprir a necessidade de torques elevados. Este estudo pode contribuir de forma significativa em sistemas que seja necessario um grau de eficiencia maior, ou seja, um maior conjugado ocupando menos espaco e com um grau de confiabilidade maior. Este trabalho propoe uma modelagem matematica e um posterior acionamento de uma maquina de inducao de nove fases assimetrica, com o objetivo de se comprovar o aumento de conjugado eletromagnetico com injecao harmonica. O modelo matematico foi desenvolvido de forma completa, representando o equacionamento para todas as componentes harmonicas, mas para realizar os testes foram utilizados os termos referentes aos tres primeiros componentes harmonicos, que foram as contribuicoes de conjugado mais significativas para a maquina.

In this paper is presented the modeling and analysis of a six-phase induction machine consideringthe space harmonic components. It is shown that the harmonic injection in phase voltages provides an increasein torque, therefore, improving the torque density of the drive system. It is presented the machine dynamicalmodel, the steady state analysis and experimental results.

This paper proposes two universal active power filters (UAPFs) configurations for single-phase systems using four-legs ac/ac converters. The proposed configurations are used for disturbances compensation in grid voltage and current. The proposed topologies are compared to the conventional structure. For this comparison, harmonic distortions, semiconductor losses and average switching frequency are used as parameters. The pulsewidth modulation (PWM) strategy, based on a space vector modulation technique, as well as the control strategy for the grid current and the dc-link bus are discussed. The simulation and experimental results are presented for validation of the proposed strategies.

This paper introduces an asymmetric cascaded multilevel inverter consisting of series-connected two nine-level (9L) H-bridge cells, which are based on modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC). An unequal dc voltage ratio of 1:2 is used, so that the proposed topology can generate 25 output voltage levels. A modulation strategy for the inverter is proposed. A comparative analysis is performed, demonstrating that the proposed inverter offers reduced losses in the semiconductor devices and smaller number of components compared to 25-level conventional MMCC. Besides that, in order to maintain the stable system, a circulating current control and voltage balancing algorithm are discussed. At last, simulation and experimental results are presented to validate the proposed system.

This paper investigates two power generation systems that utilize a rectifier with small number of controlled switches associated to a two-phase permanent magnet synchronous machine. The proposed topologies have as a main purpose converting wind energy into electrical energy for low-power applications, giving them large potential to be employed in urban and rural areas. Each configuration is commanded by only two controlled switches and has natural protection against short circuit on the dc link. Compared with two three-phase generation systems that use a reduced number of controlled switches, the proposed topologies permit obtaining sinusoidal machine currents, with low harmonic distortion, using a smaller number of controlled switches. At last, to investigate the proposed system and control strategy, simulation and experimental results are presented.