An adaptive synchronous-reference-frame phase-locked loop for power quality improvement in a polluted utility grid

Si el © es de IEEE cuando se deposite una versión de autor hay que poner el siguiente texto en "descripción": “© © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”The proper operation of grid-connected power electronics converters needs using a synchronization technique to estimate the phase of the grid voltage. The performance of this synchronization technique is related to the quality of the consumed or delivered electric power. The synchronous-reference-frame phase-locked loop (SRF-PLL) has been widely used due to its ease of operation and robust behavior. However, the estimated phase can have a considerable amount of unwanted ripple if the grid voltage disturbances are not properly rejected. The aim of this paper is to propose an adaptive SRF-PLL which strongly rejects these disturbances even if the fundamental frequency of the grid voltage varies. This is accomplished by using several adaptive infinite-impulse-response notch filters, implemented by means of an inherently stable Schur-lattice structure. This structure is perfectly suited to be programmed in fixed-point DSPs (i.e., it has high mapping precision, low roundoff accumulation, and suppression of quantization limit cycle oscillations). The proposed adaptive SRF-PLL has been tested by means of the TI TMS320F2812 DSP. The obtained experimental results show that the proposed synchronization method highly rejects the undesired harmonics even if the fundamental harmonic frequency of a highly polluted grid voltage abruptly varies. © 2011 IEEE.This work was supported by the Spanish Ministry of Science and Innovation under Grants ENE2009-13998-C02-02 and ENE2006-15521-C03-02.González Espín, FJ.; Figueres Amorós, E.; Garcerá Sanfeliú, G. (2012). An adaptive synchronous-reference-frame phase-locked loop for power quality improvement in a polluted utility grid. IEEE Transactions on Industrial Electronics. 59(6):2718-2731. doi:10.1109/TIE.2011.2166236S2718273159

An Adaptive Control System for Three-Phase Photovoltaic Inverters Working in a Polluted andVariable Frequency Electric Grid

Theproportional+resonant (PR) controller has been proposed in the past as a suitable method to control the current generated by the grid-connected photovoltaic voltage source inverters. Due to the fact that information regarding the frequency of the grid is needed to use this control technique, the synchronous reference frame phase-locked loop (SRF-PLL) is commonly used. To assure that the total harmonic distortion of the injected current (THDi) meets the appropriate standards, even if the grid voltage is polluted and its frequency varies, an adaptive control strategy is presented in this paper. This control strategy can improve the behavior of both, the conventional SRF-PLL and the conventional PR controller, when they are used in a polluted grid with a time varying frequency. The experimental results obtained by means of a digitally controlled 10-kVA inverter, show up that the THDi of the injected current is improved when the proposed adaptive control strategy replaces the conventional one.This work was supported by the Spanish Ministry of Science and Innovation under Grant ENE2009-13998-C02-02. Recommended for publication by Associate Editor B. Lehman.González Espín, FJ.; Gabriel Garcerá; Patrao Herrero, I.; Figueres Amorós, E. (2012). An Adaptive Control System for Three-Phase Photovoltaic Inverters Working in a Polluted andVariable Frequency Electric Grid. IEEE Transactions on Power Electronics. 27(10):4248-4261. https://doi.org/10.1109/TPEL.2012.2191623S42484261271

An Adaptive Digital Control Technique for Improved Performance of Grid Connected Inverters

Grid connected voltage source inverters may be controlled in the stationary reference frame by means of the infinite impulse response (IIR) P+Resonat regulator. This regulator is able to correctly track fixed frequency sinusoidal references, but does not perform well if the frequency of the electric grid voltage is varied. In order to avoid the lack of precision to track variable frequency sinusoidal references, an adaptive IIR filter structure is proposed which offers good tracking properties even if the frequency of the grid voltage varies. This filter adapts its coefficients in real time and is inherently stable no matter the adaptation process, thus overcoming one of the most important drawbacks of the IIR filter structure. Furthermore, this structure is perfectly suited to be programmed in fixed point digital signal processors (DSPs) because of some important numeric properties, i.e., it has a high mapping precision and a low round-off accumulation, and it avoids quantization limit cycle oscillations. The proposed adaptive controller has been tested by means of the TI TMS320F2812 DSP. The obtained experimental results show up that this controller allows the correct tracking of a sinusoidal reference, even if this reference is time variant.This work was supported by the Spanish Ministry of Science and Innovation under Grant ENE2012-37667-C02-01. Paper no. TII-11-622.González Espín, FJ.; Patrao Herrero, I.; Figueres Amorós, E.; Gabriel Garcerá (2013). An Adaptive Digital Control Technique for Improved Performance of Grid Connected Inverters. IEEE Transactions on Industrial Informatics. 9(2):708-718. https://doi.org/10.1109/TII.2012.2225437S7087189

Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter

[EN] An accurate small-signal model of three-phase photovoltaic (PV) inverters with a high-order grid filter is derived in this paper. The proposed model takes into account the influence of both the inverter operating point and the PV panel characteristics on the inverter dynamic response. A sensitivity study of the control loops to variations of the dc voltage, PV panel transconductance, supplied power, and grid inductance is performed using the proposed small-signal model. Analytical and experimental results carried out on a 100-kW PV inverter are presented.Figueres Amorós, E.; Garcerá, G.; Sandia Paredes, J.; González Espín, FJ.; Calvo Rubio, J. (2009). Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter. IEEE Transactions on Industrial Electronics. 56(3):706-717. doi:10.1109/TIE.2008.2010175S70671756

Measurement of the Loop Gain Frequency Response of Digitally Controlled Power Converters

[EN] The study of the loop gain frequency response in a power converter is a powerful tool commonly used for the design of the controllers used in the control stage. As the control of medium- and high-power electronic converters is usually performed digitally, it is useful to find a method to measure the digital loop gains. The purpose of this paper is to present a method for properly measuring the loop gain frequency response of digitally controlled power converters by means of an analog frequency response analyzer (FRA). An analog sinusoidal reference signal generated by the FRA is injected through an analog-to-digital converter into the digital controller, and added to the discrete feedback signal. To obtain the frequency response of the open-loop gain, both feedback and disturbed feedback signals are sent back to the FRA by using the pulsewidth modulation peripherals of the controller.This work was supported by the Spanish Ministry of Science and Innovation under Grants ENE2006-15521-C03-02 and ENE2009-13998-C02-02.González Espín, FJ.; Figueres Amorós, E.; Garcerá, G.; González-Medina, R.; Pascual Molto, M. (2010). Measurement of the Loop Gain Frequency Response of Digitally Controlled Power Converters. IEEE Transactions on Industrial Electronics. 57(8):2785-2796. https://doi.org/10.1109/TIE.2010.2056610S2785279657

Improving the energy efficiency of slightly inductive three-phase three-wire linear systems through single-phase capacitors banks

[EN] Recent low-voltage, three-phase distribution networks carry inefficient power, which can be attributed to the reactive power, imbalance of linear loads, and increase in non-linear loads. Researchers have mainly focused on developing active filters to improve the quality of electrical energy. However, in most cases, compensating for the reactive power is sufficient, considering cost and quality. Active filters are expensive, thus, passive compensators are more appealing. These devices are composed of single-phase or three-phase capacitor banks that act on the reactive power consumed by the load. The operation of these devices has been sufficiently validated owing to their long-term use. For unbalanced power, compensators that contain coils are used. A methodology to obtain compensators comprising only single-phase capacitors for the inductive reactive power consumed by the load is presented here; if designed appropriately, these compensators can compensate for a part of or the entire unbalanced power, resulting in greater efficiency in the transfer of electrical energy.Spanish Ministry of Science, Innovation, and Universities (MICINN); European Regional Development Fund (ERDF), Grant/AwardNumber: RTI2018100732-B-C21Blasco Espinosa, PA.; Montoya-Mira, R.; Diez-Aznar, J.; Montoya Villena, R.; Garcerá, G.; Figueres Amorós, E. (2022). Improving the energy efficiency of slightly inductive three-phase three-wire linear systems through single-phase capacitors banks. IET Generation Transmission & Distribution. 16(6):1212-1224. https://doi.org/10.1049/gtd2.12361S1212122416

Drift reduction of low drift nozzles in spraying citrus orchards

Drift is especially critical when spraying fruit, vine and citrus orchards where pesticides are intensively used. In this context, cone low drift nozzles (LDN) intended for spraying tree crops, have been evaluated relating to cone standard nozzles (STN) in laboratory and deciduous fruit orchards (Van de Zande et al. 2012); (Planas et al., 2013)

Efecto de boquillas de baja deriva y convencionales sobre la deriva y el control de Aonidiella aurantii (Maskell) en cítricos

La deriva es la mayor fuente de contaminación durante los tratamientos fitosanitarios en cultivos arbóreos. Una de las tecnologías efectivas para su reducción es el uso de boquillas de baja deriva (LDN). Sin embargo, su uso podría afectar la eficacia de control. El objetivo de este trabajo fue estudiar el efecto de LDN sobre la deriva y la eficacia de los tratamientos fitosanitarios en el control de Aonidiella aurantii en cítricos frente a boquillas convencionales (STN). Para evaluar la deriva se realizó un ensayo siguiendo la metodología de la norma ISO 22866 en una parcela comercial de Clemenules. Para evaluar la eficacia se llevó a cabo un ensayo en una parcela comercial de Clemenules y se emplearon los siguientes productos: Reldan® E + Atominal® 10 EC, Reldan® E y aceite parafínico contra la primera, segunda y tercera generación respectivamente. En ambos casos las aplicaciones se realizaron con un volumen de caldo de aproximadamente 2500 L ha-1, empleando un turboatomizador. Se aplicó un tratamiento con boquillas STN Teejet de disco y núcleo, y otro con boquillas LDN Albuz modelo TVI, seleccionando en cada ensayo el diámetro adecuado para ajustar el volumen aplicado a las características de cada parcela. En el ensayo de eficacia también hubo un tratamiento Control (sin insecticidas). Los resultados mostraron que la boquilla LDN redujo en un 22.7% la deriva depositada. No se encontraron diferencias significativas de eficacia entre los tratamientos con LDN y STN, pero si entre estos y el Control. Por lo tanto, se deduce de este trabajo que las boquillas LDN son la solución para reducir la deriva en tratamientos contra A. auranti en cítricos sin comprometer la eficacia

Recursos hospitalarios y letalidad por infarto de miocardio. Estudio IBERICA

[Abstract] Introduction and objectives. To determine the proportion of patients with myocardial infarction (MI) not admitted to a coronary care unit (CCU), the variables associated with admission into a CCU, and whether admission to a CCU, and the availability of coronary angiography in the same hospital, were associated with 28-day case fatality. Patients and method. Population-based registry of MI in patients 25 to 74 years of age, admitted during 1996-1998. Demographic and clinical characteristics were recorded, as well as management, clinical course and survival after 28 days. Hospitals were classified according to the availability of a CCU and catheterization laboratory (advanced hospital), CCU only (intermediate hospital) or neither (basic hospital). Admission to the CCU was also recorded. Results. In all, 9046 cases of MI were recorded; in 11.3% the patient was not admitted to a CCU. Age, smoking (OR=1.33; 95% CI, 1.08-1.64), non-Q MI (OR=0.62; 95% CI, 0.49-0.78) or undetermined location of MI (OR=0.34; 95% CI, 0.23-0.50), Killip 4 score on admission (OR=0.63; 95% CI, 0.40-1.00) and delay in arrival at the hospital >6 h were associated with CCU admission. Patients admitted to a CCU showed a lower case fatality in the first 24 h (4.2% vs 23.5%), which was independent of comorbidity, severity and treatment. The 24-hour survivors admitted to a basic hospital had higher case fatality (17.3% vs 7.8%) than other groups, which was related to differences in treatment. Conclusions. CCU admission is associated with a lower case fatality in the first 24 h. Admission to a basic hospital is associated with a higher 28-day case fatality even in patients who survive 24 h.[Resumen] Introducción y objetivos. Determinar el porcentaje de pacientes con infarto agudo de miocardio (IAM) que no ingresan en una unidad de cuidados intensivos coronaries (UCIC), las variables asociadas al ingreso en una UCIC y si el ingreso en una UCIC, su disponibilidad y la de hemodinámica en el hospital se asocian a la letalidad a 28 días. Pacientes y método. Registro poblacional (1996-1998) de casos de IAM en pacientes con edades comprendidas entre los 25 y los 74 años. Se recogieron variables demográficas, clínicas, el ingreso en UCIC y la letalidad a los 28 días. Se clasificaron los hospitales según la disponibilidad de UCIC y hemodinámica (hospital avanzado), solamente UCIC (hospital intermedio) o ninguno (hospital básico). Resultados. Se registraron 9.046 casos; el 11,3% no ingresó en una UCIC. La edad, el consumo de tabaco (odds ratio [OR] = 1,33; intervalo de confianza [IC] del 95%, 1,08-1,64), el infarto sin onda Q (OR = 0,62; IC del 95%, 0,49-0,78) o ilocalizable (OR = 0,34; IC del 95%, 0,23-0,50), el grado Killip 4 al ingreso (OR = 0,63; IC del 95%, 0,40-1,00) y el retraso > 6 h en llegar al hospital se asociaron al ingreso en UCIC. Los pacientes ingresados en UCIC presentaban menor letalidad que los ingresados en hospitales básicos en las primeras 24 h (el 4,2 frente al 23,5%), independientemente de la gravedad del IAM y de las variables relacionadas con el tratamiento. Los su-pervivientes a 24 h que ingresaban en un hospital bÁsico presentaban mayor letalidad a los 28 días (el 17,3 frente al 7,8%), relacionada con las variables de tratamiento. Conclusiones. El ingreso en una UCIC se asocia a una menor letalidad de los pacientes con IAM en las primeras 24 h. El ingreso en un hospital bÁsico se asocia a una mayor letalidad a los 28 días.Insituto de Salud Carlos III; FIS96/0026-01 to 05Insituto de Salud Carlos III; FIS97/1270Insituto de Salud Carlos III; FIS98/153