Examinando por Autor "Tilaguy-Lezama, Sebastián"
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- PublicaciónSólo datosAdaptive Sampling Frequency Synchronized Reference Generator for Grid Connected Power Converters(Communications in Computer and Information Science, 2018-09-13) López-Santos, Oswaldo; Tilaguy-Lezama, Sebastián; García, GermainThis paper introduces a simplified method for digital generation of high-quality references required for control of single-phase grid-connected (GC) power converters, which can generate synchronized sinusoidal waveforms at the same frequency of the input signal or its harmonics. Therefore, its application can be useful for active power filtering, high power factor rectification, and grid integration of renewable energy sources. A hybrid analog-digital implementation is proposed integrating an Adaptive Sampling Frequency Moving Average Filter (ASF-MAF) and a discrete-time Proportional-Integral (PI) controller into a Digital Signal Processor (DSP) operating with a sampling frequency defined by an external hardware-based Voltage Controlled Oscillator (VCO). The main advantages attributed to the method are immunity to harmonic content, accuracy in computations despite of frequency changes, flexibility to produce phase displacements and reduced computational cost. Performance of the proposal was verified by means of simulation and experimental results.
- PublicaciónSólo datosControl of the bidirectional buck-boost converter operating in boundary conduction mode to provide hold-up time extension(Energies, 2018-09-26) López-Santos, Oswaldo; Urrego-Aponte, Jose O; Tilaguy-Lezama, Sebastián; Almansa-López, José DavidA hold-up time extension circuit (HTEC) is used to charge and discharge an auxiliary capacitor. This capacitor stores the energy required to extend the operation time of critical loads experiencing short duration failures (SDF) at the DC bus to which they are connected. This paper presents complete modeling and a control-wise approach to a parallel HTEC based on the bidirectional buck-boost converter, which operates in Boundary Conduction Mode (BCM) with a variable switching frequency. The circuit permanently regulates the voltage of the auxiliary capacitor as well as the voltage of the DC bus during SDF, which is uncommon in industrial versions of HTEC. Enforcing the operation in BCM allows a reduction in the size of the inductor in the converter without requiring additional control circuitry. The entire behavior of the proposed HTEC, in all its operation modes, was analyzed theoretically and validated using simulation and experimental results, showing the potential of the circuit to be used in real applications.
- PublicaciónSólo datosDiscrete Time Nested-Loop Controller for the Output Stage of a Photovoltaic Microinverter(Communications in Computer and Information Science, 2017-01-01) López-Santos, Oswaldo; Cortes-Torres, Luis; Tilaguy-Lezama, SebastiánThis paper presents a comprehensive study of the digital implementation of the control requirements of the output stage of a two-stage solar microinverter. This approach uses a synchronized nested-loop controller which ensures the tracking of an internally generated high-quality current reference, the estimation and cancelation of the effect of the DC-link voltage ripple in the control loops and the regulation of the average value of the DC-link voltage. The proposed control architecture is validated by means of simulation results comparing operation of the inverter using continuous time, quasi-discrete time and discrete time implementations.
- ÍtemAcceso abiertoOperation of a Photovoltaic Microinverter as Active Power Filter using the single phase PQ Theory and Sliding Mode Control(2017-05-10) Lopez-Santos, Oswaldo; Tilaguy-Lezama, Sebastián; Rico-Ramírez, Sandra Patricia; Cortes-Torres, Luis DaríoContext: Microinverters are widely used in modular photovoltaic installations but its operation with reduced power is limited to inject real power into the grid. One way to optimize the use of microinverters consist of providing them the Active Power Filtering (APF) capability, which allows its use as both distributed generation and compensation unit even under unfavorable conditions of insolation. With this approach, the output stage of the microinverter can provide reactive and distortive components of power in order to compensate power quality defects of a localized load. Method: This paper proposes a non-linear control strategy to integrate the APF function in a singlephase two-stage photovoltaic microinverter. The proposal involves the use of the single-phase P-Q theory to generate the current reference, sliding mode control to achieve a robust tracking of that reference and linear robust control to maintain the power balance regulating the DC-link voltage of the microinverter. The proposed control does not require the use of low-pass filters and in turn uses a recursive average computation improving the general performance of the system. Results: The theoretical approach is validated by means of simulation results in which appropriate levels of harmonic distortion are obtained in the grid-side current for different load types and power levels. The robustness of the control system is tested by applying disturbances in the harmonic content of the load current and its power level obtaining an appropriate dynamic performance adapted to the demands of the application. Conclusions: The main advantage of this proposal is the possibility to add the active filter function to coventional microinverters extending its capability to power conditioning only integrating some algorithms. A simple design method to ensure reliability, robustness and high power quality is detailed.