10 research outputs found
A two stage hybrid maximum power point tracking technique for photovoltaic applications
No full textPhotovoltaic (PV) systems are widely used now a days for coping the growing energy demands all across the globe. The non-linear behavior of the characteristic curve of solar module requires special arrangement to harvest maximum amount of power. To track the Maximum Power Point (MPP) across the non linear IV curve of PV module, techniques are used in addition to the power electronic circuit and are called Maximum Power Point Tacking (MPPT). Various methods of MPPT exists in literature, each bearing its own pros and cons. In this paper we presents a novel technique to improve the performance of conventional Perturb and Observe (P&O) algorithm of MPPT. Our technique removes the drawbacks of P&O under rapidly changing environmental conditions. It also executes less power oscillations under steady state conditions. The algorithm is a hybrid of Fractional Short Circuit current (FSCC) and P&O algorithms. The system takes the advantage of rapid tracking near to MPP using the FSCC and then carry on to track the exact MPP using the traditional P&O technique. The technique is verified through simulation using Matlab/SIMULIN
Microprocessor Based Power Factor Improvement of Induction Motor
No full textThis paper describes the design of a microprocessor controller for a fixed-capacitor, thyristor controller reactor (FC-TCR) compensator to achieve on line and fast power factor improvement of a dynamic load. The microprocessor system monitors the power factor of the load and uses a look-up table to adjust the FC-TCR compensator to give a unity supply power factor. The results show that under all loading conditions, the power factor of almost unity is achieved automatically. The response time of the system is very fast
Microprocessor based power factor improvement of induction motor
No full textThis paper describes the design of a microprocessor controller for a fixed-capacitor, thyristor controller reactor (FC- TCR) compensator to achieve on line and fast power factor improvement of a dynamic load. The microprocessor system monitors the power factor of the load and uses a look-up table to adjust the FC- TCR compensator to give a unity supply power factor. The results show that under all loading conditions, the power factor of almost unity is achieved automatically. The response time of the system is very fast
A New Sensorless Hybrid MPPT Algorithm Based on Fractional Short-Circuit Current Measurement and P&O MPPT
No full textThis paper presents a new maximum power point tracking (MPPT) method for photovoltaic (PV) systems. The proposed method improves the working of the conventional perturb and observe (P&O) method in changing environmental conditions by using the fractional short-circuit current (FSCC) method. It takes the initial operating point of a PV system by using the short-circuit current method and later shifts to the conventional P&O technique. The advantage of having this two-stage algorithm is rapid tracking under changing environmental conditions. In addition, this scheme offers low-power oscillations around MPP and, therefore, more power harvesting compared with the common P&O method. The proposed MPPT decides intelligently about the moment of measuring short-circuit current and is, therefore, an irradiance sensorless scheme. The proposed method is validated with computer software simulation followed by a dSPACE DS1104-based experimental setup. A buck-boost dc-dc converter is used for simulation and experimental confirmation. Furthermore, the reliability of the proposed method is also calculated. The results show that the proposed MPPT technique works satisfactorily under given environmental scenario
A new irradiance sensorless hybrid MPPT technique for photovoltaic power plants
No full textA hybrid Maximum Power Point Tracking (MPPT) method without using an irradiance sensor is proposed in this paper. The hybrid MPPT method is a combination of conventional Perturb and Observe (P&O) and Fractional Short Circuit Current (FSCC) MPPT technique. The proposed hybrid MPPT decides intelligently about the initial operating point of P&O by using the FSCC MPPT method. This method requires no sensor for irradiation measurement because it detects intelligently about the change in irradiance. Therefore, under dynamic weather conditions the decision about measuring the initial operating point of P&O is intelligent. After finding the initial operating point the system shifts to the conventional P&O method and starts to perturb with a small perturbation size. The use of small perturbation steps enables the system to work with less power oscillations around the Maximum Power Point (MPP), while the use of FSCC helps in rapid tracking of MPP especially under the varying environmental conditions. Thus, the proposed method is fast in tracking the MPP with less power oscillations and hence better performance in terms of energy harvesting when compared with the conventional P&O technique. Impedance matching between solar panel and load is achieved using a DC-DC boost converter and the proposed method is simulated in MATLAB/SIMULINK environment. The system is simulated against the steady and dynamic weather conditions. The results shows that under steady weather condition the proposed method harvests 5% extra energy as compared with the conventional P&O. For dynamic weather conditions the proposed method harness an additional 3.5% energy when compared with the P&O method, which makes it very promisin
Harmonic minimization in a Chopper-type AC voltage controller
No full textElectrical Engineering Department, College of Engineering, King Saud University, P.O. Box-800 Riyadh 11421, Saudi Arabia
email: [email protected] AC voltage regulator of the chopper-type presents an attractive alternative for AC voltage control. This is attributed to its extended range of control coupled with independence of the switching angles with respect to load phase angle. Moreover. using microprocessors to determine firing instances makes it possible to change regulator's ON and OFF periods at will with appreciable ease. This adds a new merit for this type of controllers since it would be possible to alter the magnitudes of harmonics present in load voltage or even eliminating selected orders. In this paper the values of switching angles yielding minimum harmonic content in load current are determined. Profiles of these angles at different values of load phase angle are presented for cases of out-put load voltage with three, five and seven pulses per haf cycle. Optimal values of switching angles are evaluated using an algorithm based on optimization technique of the direct search method. Validity of the results obtained is confirmed by comparing it with relevant values obtained by direct manipulation for the possible combinations of switching angles. Experimental results obtained from a microprocessor-control-led AC chopper confirming the theoretical analysis are presented. The approach presented is general and can be well extended for harmonic minimization with any number of pulses per half cycle and specific values of load phase angle
Operation of a Photovoltaic Microinverter as Active Power Filter using the single phase P-Q Theory and Sliding Mode Control
No full textContext: 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 single-phase 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.
Language: Englis
Operación de un Microinversor Fotovoltaico como Filtro Activo de Potencia Usando la Teoría P-Q Monofásica y Control en Modo Deslizante
No full textContext: 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 single-phase 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.Language: English Contexto: Los microinversores son ampliamente utilizados en instalaciones fotovoltaicas modulares pero su operación con potencia reducida es limitada a inyectar potencia real en la red. Una forma de optimizar el uso de los microinversores consiste en proveerles la capacidad para realizar Filtrado Activo de Potencia (FAP), lo que permite su uso como una unidad tanto de generación como de compensación distribuida, incluso en condiciones desfavorables de irradiación solar. Con esta propuesta, la etapa de salida del microinversor puede suministrar componentes de potencia reactiva y de distorsión para compensar defectos en la calidad de energía de una carga localizada.Método: Este artículo propone una estrategia de control no lineal para integrar la función FAP en un microinversor fotovoltaico monofásico de dos etapas. La propuesta involucra el uso de la teoría P-Q monofásica para generar la referencia de corriente, control en modo deslizante para conseguir un seguimiento robusto de dicha referencia y control lineal robusto para mantener el balance de potencia regulando el voltaje del bus DC intermedio del microinversor. El control propuesto no requiere del uso de filtros pasa-bajos y en cambio usa un cómputo recursivo de valor promedio, mejorando el desempeño general del sistema.Resultados: La propuesta teórica es validada usando resultados de simulación en los que se evidencian niveles apropiados de distorsión armónica en la corriente de la red, los cuales se obtienen para diferentes tipos de carga y niveles de potencia. La robustez del sistema de control es puesta a prueba aplicando perturbaciones en el contenido armónico de la corriente de la carga y su nivel de potencia obteniendo un desempeño dinámico adecuado para las exigencias de la aplicación.Conclusiones: La principal ventaja obtenida con el sistema de control propuesto es la posibilidad de adicionar la función de filtrado activo a los microinversores convencionales para extender su contribución hacia el acondicionamiento eléctrico con la integracción de algunos algoritmos. Se detalla un diseño simple para asegurar confiabilidad, robustez y altos niveles de calidad de potencia.Idioma: Inglé
