Técnicas de controle aplicadas a um sistema eólico equipado com o PMSG com função de filtragem de corrente harmônica da rede Sob distorções na tensão da rede / Control techniques applied to a wind power system equipped with PMSG with grid harmonic current filtering function under grid voltage distortions

Este artigo avalia técnicas de controle aplicadas a um sistema de geração de energia eólica equipado com o gerador síncrono de ímã permanente (PMSG - Permanent Magnet Synchronous Generator) conectado à rede elétrica sob tensão de rede distorcida. O conversor eletrônico back-to-back é utilizado para conectar a fonte de geração eólica a rede elétrica através de um filtro indutivo. As potências ativa e reativa do gerador são controladas pela orientação do fluxo do rotor pelo conversor do lado do gerador (CLG) utilizando controladores PI para as malhas de correntes e velocidade. O conversor do lado da rede (CLR) regula a tensão do barramento CC e controla as correntes sintetizadas na saída do conversor. A mitigação harmônica é incorporada ao sistema de energia eólica e, juntamente com o algoritmo DSOGI-PLL (do inglês Dual Second Order Generalized Integrator-Phase Locked Loop) garantem a melhoria da qualidade da energia por meio da redução da distorção da corrente da rede. O sistema de energia eólica é analisado em três estudos de casos sob variação da potência gerada e distorções na tensão da rede elétrica com a mesma carga não-linear conectada no ponto de acoplamento comum (PAC). Os resultados obtidos na simulação mostram que as estratégias de controle aplicadas ao sistema em conjunto com a filtragem ativa pelo CLR e DSOGI-PLL garantem o fornecimento de energia à rede elétrica e apresentam as menores distorções harmônicas nas correntes da rede. Para esta condição de carga, foi possível verificar que o DSOGI-PLL funciona melhor para maiores distorções de tensão na alimentação

Fault-Tolerant Operation of DFIG-WT with Four-Switch Three-Phase Grid-Side Converter by Using Simplified SVPWM Technique and Compensation Schemes

IEEE In this paper, in response to the open-circuit fault scenario in the grid-side converter (GSC) of doubly-fed induction generator-based wind turbines (DFIG-WTs), a fault-tolerant four-switch three-phase (FSTP) topology-based GSC is studied. Compared with other switch-level fault-tolerant converter topologies, fewer switches, less switching and conduction losses, and simpler converter structure are derived. A simplified space vector pulse width modulation (SVPWM) technique is proposed to improve the output current quality and reduce the computational complexity in the control process. Unified expressions of duty ratios for the two remaining healthy bridge arms are obtained. In addition, the three-phase unbalance phenomenon caused by the capacitive impedance in the faulty phase is analysed from the AC point of view, and a current distortion compensation scheme is illustrated. Furthermore, a DC-bus voltage deviation suppression strategy is proposed to maximize the DC-bus voltage utilization rate and mitigate the damage to the DC-link capacitors. Simulations are carried out in Matlab/Simulink2017a to demonstrate the validity of the proposed SVPWM technique and compensation schemes in FSTP GSC for a 1.5MW grid-connected DFIG-WT when different working conditions are considered

Performance Analysis of a Four-Switch Three-Phase Grid-Side Converter with Modulation Simplification in a Doubly-Fed Induction Generator-Based Wind Turbine (DFIG-WT) with Different External Disturbances

This paper investigates the performance of a fault-tolerant four-switch three-phase (FSTP) grid-side converter (GSC) in a doubly-fed induction generator-based wind turbine (DFIG-WT). The space vector pulse width modulation (SVPWM) technique is simplified and unified duty ratios are used for controlling the FSTP GSC. Steady DC-bus voltage, sinusoidal three-phase grid currents and unity power factor are obtained. In addition, the balance of capacitor voltages is accomplished based on the analysis of current flows at the midpoint of DC bus in different operational modes. Besides, external disturbances such as fluctuating wind speed and grid voltage sag are considered to test its fault-tolerant ability. Furthermore, the effects of fluctuating wind speed on the performance of DFIG-WT system are explained according to an approximate expression of the turbine torque. The performance of the proposed FSTP GSC is simulated in Matlab/Simulink 2016a based on a detailed 1.5 MW DFIG-WT Simulink model. Experiments are carried out on a 2 kW platform by using a discrete signal processor (DSP) TMS320F28335 controller to validate the reliability of DFIG-WT for the cases with step change of the stator active power and grid voltage sag, respectively

Resilient DC voltage control for islanded wind farms integration using cascaded hybrid HVDC system

To integrate large-scale islanded onshore wind power with different sizes, this paper proposes an integration system based on the cascaded hybrid HVDC transmission system, which consists of LCC and several MMCs in series connection at the DC side of the rectifier. A large-scale wind farm is connected with one LCC and one MMC while several small-scale wind farms are connected with MMCs directly. Owing to the hierarchical integration arrangement, the operating flexibility can be improved with reduced capacity and the number of step-up interfacing transformers. A resilient DC voltage control is proposed for the integration system to adaptively redistribute power among the converters during wind power fluctuations. Firstly, the topology and operating characteristics of the wind power integration system are introduced. Then, a resilient DC voltage control is proposed to ensure stable operation during wind power curtailments. Finally, a simulation model of the hybrid cascaded HVDC transmission system is built in PSCAD/EMTDC to verify the effectiveness. The research results show that the system provides a new option for long-distance transmission of large-scale islanded wind power

A Review on Superconducting Magnetic Energy Storage System Applications

Superconducting Magnetic Energy Storage is one of the most substantial storage devices. Due to its technological advancements in recent years, it has been considered reliable energy storage in many applications. This storage device has been separated into two organizations, toroid and solenoid, selected for the intended application constraints. It has also been used in many industries, such as transportation, renewable energy utilization, power system stabilization, and quality improvement. This chapter discusses various SMES structures and their applications in electric and power systems. Here, the authors try to deliver a comprehensive view for scholars whose research is related to the SMES by examination of the published articles while providing a brief guideline of this modern technology and its applications

Reduction of switching losses and passive components rating in series-connected current source inverters

The current source inverter (CSI) is widely used in medium voltage drives due to its simple configuration, reliable short-circuit protection, and low dv/dt issue. Conventional series-connected current source inverters (SC-CSI) are constituted of several current source inverters (CSIs) connected in series through multi-winding transformers to enhance the power capacity. It is very promising in high-voltage applications. Switching losses of the semiconductor switches significantly impact the power efficiency of SC-CSIs. Therefore, inverter design must consider these losses, which depend on factors, such as switching frequency, modulation schemes and semiconductor parameters. This thesis aims to reduce the switching losses of conventional SC-CSIs by decreasing the switching frequency from 540 Hz to 360 Hz and eventually to 60 Hz. In Chapter 2, the switching frequency is reduced to 360 Hz for the switching loss reduction. The active damping control is implemented to mitigate the increase in filter capacitance caused by the lower switching frequency. Chapter 3 is to further reduce the switching losses by reducing the switching frequency to 60 Hz. However, this strategy results in a significant increase in the passive components. To address this issue, the multi-winding transformer is replaced with a phase-shifting transformer, as the active damping method applied in Chapter 2 is no longer effective at this reduced frequency. The switching losses and the passive components of SC-CSIs are investigated with switching frequencies of 540Hz, 360Hz and 60 Hz. Simulations are conducted using MATLAB/SIMULINK to verify the investigation

Power loss investigation of series-connected current source inverters

Current-source inverters (CSIs) are a type of direct current (DC) to alternating current (AC) converters that generate a defined AC output current waveform from a DC current supply. As the counterpart of voltage source inverters (VSIs), they feature a simple converter structure, low switching dv/dt on the ac-side, and reliable short-circuit protection. These advantages have made CSIs widely used in high power medium voltage drives. Besides, they have also been studied in other applications, such as wind energy conversion systems, superconducting magnetic energy storage (SMES) systems, and microgrid systems. Different topologies of CSIs and modulation schemes have been evolved to tailor various application requirements. For those applications with a higher power rating, two or more CSIs can be connected in series to form series-connected CSIs (SC-CSIs) to increase the power handling capability. To the best of the author’s knowledge, three topologies of SC-CSIs have been developed so far. The first topology referred to as topology A is constructed by connecting several identical CSIs in series. These CSIs are identical in terms of topology, modulation, and control. A multi-winding transformer is employed at the output to provide a clear current path for each CSI and step up the voltage if necessary. In the second topology designated as topology B, the multi-winding transformer is replaced by a phase-shifting transformer, and a phase-shifting modulation scheme is implemented. This topology features an increased DC current utilization, decreased switching losses, and reduced passive components. The third topology denominated as topology C adopts a different arrangement of switches leading to a reduced number of switching devices. A multi-winding transformer is used at the output in this topology. Power losses are an important attribute of SC-CSIs since they have a significant impact on the efficiency of the system. Besides, it is necessary to find out the power loss distribution of inverters to design an appropriate cooling system. However, the power losses and the power loss distribution of these three topologies have not been figured out. [...