Online Control of Modular Active Power Line Conditioner to Improve Performance of Smart Grid

This thesis is explored the detrimental effects of nonlinear loads in distribution systems and investigated the performances of shunt FACTS devices to overcome these problems with the following main contribution: APLC is an advanced shunt active filter which can mitigate the fundamental voltage harmonic of entire network and limit the THDv and individual harmonic distortion of the entire network below 5% and 3%, respectively, as recommended by most standards such as the IEEE-519

Finite-fixed switching predictive control technique for a 7-level cascaded H-bridge multilevel active power filter. A comparative study.

This paper presents a finite-fixed predictive control technique applied to the three-wire cascade H-bridge multilevel converters for active power filter applications. The focus of this paper is to examine the impacts of the use of optimum modulation techniques combined with predictive current control in order to increase the control performance in terms of reactive power compensation and total harmonic distortion.CONACYT – Consejo Nacional de Ciencia y Tecnologí

Control of MMC-based STATCOM as an effective interface between energy sources and the power grid

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This paper presents a dynamic model of modular multilevel converters (MMCs), which are considered as an effective interface between energy sources and the power grid. By improving the converter performance, appropriate reactive power compensation is guaranteed. Modulation indices are calculated based on detailed harmonic evaluations of both dynamic and steady-state operation modes, which is considered as the main contribution of this paper in comparison with other methods. As another novelty of this paper, circulating current control is accomplished by embedding an additional second harmonic component in the modulation process. The proposed control method leads to an effective reduction in capacitor voltage fluctuation and losses. Finally, converter’s maximum stable operation range is modified, which provides efficiency enhancements and also stability assurance. The proficiency and functionality of the proposed controller are demonstrated through detailed theoretical analysis and simulations with MATLAB/Simulink

Modular Multilevel Cascaded Flying Capacitor STATCOM for Balanced and Unbalanced Load Compensation

Voltage and current unbalance are major problems in distribution networks, particularly with the integration of distributed generation systems. One way of mitigating these issues is by injecting negative sequence current into the distribution network using a Static Synchronous Compensator (STATCOM) which normally also regulates the voltage and power factor. The benefits of modularity and scalability offered by Modular Multilevel Cascaded Converters (MMCC) make them suitable for STATCOM application. A number of different types of MMCC may be used, classified according to the sub-module circuit topology used. Their performance features and operational ranges for unbalanced load compensation are evaluated and quantified in this research. This thesis investigates the use of both single star and single delta configured five-level Flying Capacitor (FC) converter MMCC based STATCOMs for unbalanced load compensation. A detailed study is carried out to compare this type of sub-module with several other types namely: half bridge, 3-L H-bridge and 3-L FC half bridge, and reveals the one best suited to STATCOM operation. With the choice of 5-L FC H-bridge as the sub-module for STATCOM operation, a detailed investigation is also performed to decide which pulse width modulation technique is the best. This was based on the assessment of total harmonic distortion, power loss, sub-module switch utilization and natural balancing of inner flying capacitors. Two new modulation techniques of swapped-carrier PWM (SC-PWM) along with phase disposed and phase shifted PWM (PS-PWM) are analyzed under these four performance metrics. A novel contribution of this research is the development of a new space vector modulation technique using an overlapping hexagon technique. This space vector strategy offers benefits of eliminating control complexity and improving waveform quality, unlike the case of multilevel space vector technique. The simulation and experimental results show that this method provides superior performance and is applicable for other MMCC sub-modules. Another contribution is the analysis and quantification of operating ranges of both single star and delta MMCCs in rating the cluster dc-link voltage (star) and current (delta) for unbalanced load compensation. A novel method of extending the operating capabilities of both configurations uses a third harmonic injection method. An experimental investigation validates the operating range extension compared to the pure sinusoidal zero sequence voltage and current injection. Also, the superiority of the single delta configured MMCC for unbalanced loading compensation is validated

A novel predictive-fixed switching frequency technique for a cascade H-bridge multilevel STATCOM

There are several control techniques for active power filter applications. This paper presents a new alternative of predictive current control for a cascade H-bridge multilevel converter, where the optimal vector selected by the predictive controller is used for a modulation stage to obtain a fixed switching frequency. Simulation results validate the proposal where almost similar results can be obtained in comparison with the traditional methods.CONACYT – Consejo Nacional de Ciencia y Tecnologí

Modulated Model Predictive Control with Branch and Band Scheme for Unbalanced Load Compensation by MMCC-STATCOM

This paper presents a novel modulated model- predictive control (MMPC) scheme for Modular Multilevel Cascaded Converter-based STATCOMs (MMCC-STATCOM) to compensate unbalanced load current and regulate reactive power flow. By adding a common mode voltage (CMV) to the phase-voltages of the star-connected MMCC current model, the method allows natural injection of a non-sinusoidal voltage to the neutral point of the converter, hence achieving inter-phase cluster voltage balance. Moreover the imposed CMV is shown to extend the operating ranges of MMCC STATCOMs when used for negative sequence current compensation. The proposed MMPC method incorporates a modified branch and bound (B&B) algorithm to optimize the per-phase switch duty ratios. It is shown to be computationally more efficient compared to model-predictive control schemes using optimal voltage level method combined with voltage sorting schemes. Experimental results with different weighting factors confirm the effectiveness of this control scheme, and compared favorably with the conventional scheme of injecting only a sinusoidal zero sequence voltage

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

Modulated Model Predictive Control with Common Mode Voltage Injection for MMCC-STATCOM Based Unbalanced Load Compensation

This paper presents a novel modulated model- predictive control (MMPC) scheme for Modular Multilevel Cascaded Converter-based STATCOMs (MMCC-STATCOM) to compensate unbalanced load current and regulate reactive power flow. By adding a common mode voltage (CMV) to the phase-voltages of the star-connected MMCC current model, the method allows natural injection of a non-sinusoidal voltage to the neutral point of the converter, hence achieving inter-phase cluster voltage balance. Moreover the imposed CMV is shown to extend the operating ranges of MMCC STATCOMs when used for negative sequence current compensation. The proposed MMPC method incorporates a modified branch and bound (B&B) algorithm to optimize the per-phase switch duty ratios. It is shown to be computationally more efficient compared to model-predictive control schemes using optimal voltage level method combined with voltage sorting schemes. Experimental results with different weighting factors confirm the effectiveness of this control scheme, and compared favorably with the conventional scheme of injecting only a sinusoidal zero sequence voltage