Person: Gubía Villabona, Eugenio
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Gubía Villabona
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Eugenio
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0000-0002-0067-1715
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1768
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Publication Open Access Active damping based on the capacitor voltage positive-feedback for grid-connected power converters with LCL filter(IEEE, 2019) Samanes Pascual, Javier; Gubía Villabona, Eugenio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónThe capacitor voltage positive-feedback is a widely extended active damping strategy. It can effectively damp the LCL output filter resonant poles for low ratios of resonance to sampling frequencies. However, the existing delays in the control loop limit the applicability of the capacitor-voltage positive-feedback. For high ratios of resonance to sampling frequencies, it becomes ineffective and can even destabilize the system. This limitation is overcome in this paper by adjusting the delay in the feedback path. With the delay adjustment, a robust damping can be achieved if the delays are properly considered, including the filters, and the grid impedance variations are taken into account. Simulation results validate the proposed active damping strategy.Publication Open Access Multisampled-capacitor-voltage active damping for parallel interleaved grid connected voltage source converters with LCL filter(IEEE, 2017) Samanes Pascual, Javier; Gubía Villabona, Eugenio; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaParallel interleaved converters for high power renewable energy systems present stability issues at the LCL resonance frequency. A multisampled measurement and filtering strategy is proposed to stabilize the system based on the capacitor voltage derivative active damping, overcoming its limitations for low switching power converters. The effects of the delays on the stability of the active damping strategy would be analysed. The solution developed is robust against grid inductance variations, ensuring the fulfilment of the stringent harmonic grid codes.Publication Open Access Robust multisampled capacitor voltage active damping for grid-connected power converters(Elsevier, 2019) Samanes Pascual, Javier; Urtasun Erburu, Andoni; Gubía Villabona, Eugenio; Petri, Alberto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThe derivative feedback of the capacitor voltage is one of the most extended active damping strategies, used to eliminate stability problems in grid-connected power converters with an LCL filter. This strategy is equivalent to the implementation of a virtual impedance in parallel with the filter capacitor. This virtual impedance is strongly affected by the control loop delays and frequency, creating changes in the sign of the emulated virtual resistor, and raising instability regions where the active damping is ineffective. As a consequence, the LCL resonance frequency is restricted to vary, as the effective grid inductance changes, within the active damping stability region. This is an additional restriction imposed on the LCL filter design that can compromise the achievement of an optimised design. For this reason, in this work, a different strategy is presented; by adjusting the delay in the active damping feedback path, it becomes stable within the range where the LCL resonance frequency can be located for a given filter design, achieving a robust damping. Analytical expressions are provided to adjust this delay. To widen the stability region of the capacitor voltage derivative active damping, a multisampled derivative is implemented, overcoming its limitations close to the control Nyquist frequency. Experimental and simulation results validate the active damping strategy presented.Publication Open Access Deadbeat voltage control for a grid-forming power converter with LCL filter(IEEE, 2023) Samanes Pascual, Javier; Rosado Galparsoro, Leyre; Gubía Villabona, Eugenio; López Taberna, Jesús; Pérez, Marcelo A.; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenGrid-forming power converters are controlled as voltage sources to regulate the grid voltage and frequency. These converters can increase power system strength if they impose a voltage waveform resilient to grid transients. For this reason, in this paper, we propose a deadbeat control strategy of the capacitor voltage for high power converters with LCL filter. To damp the LCL resonant poles, an active damping strategy is developed, based on a modification of the deadbeat control law. With this purpose, a notch filter is applied to the electrical variables allowing to emulate different damping resistances for the fundamental component and the harmonics. As a result, the active damping does not introduce tracking errors of the fundamental frequency component, while it provides damping to the filter resonance. The proposed strategy does not require knowledge of the grid impedance, an interesting feature in grid-connected power converters because the grid impedance is generally unknown. Experimental results validate the proposed strategy.Publication Open Access On the limits of the capacitor-voltage active damping for grid-connected power converters with LCL filter(IEEE, 2018) Samanes Pascual, Javier; Gubía Villabona, Eugenio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaActive damping strategies are widely extended to avoid stability issues at the LCL filter resonant poles in grid-connected voltage source converters. The capacitor voltage derivative active damping effectively damps the filter resonant poles without additional sensors, but it loses its effectiveness as the resonance frequency approaches the converter control Nyquist frequency, influenced by the existing delays in the control loop. To reduce this limitation, the delays can be reduced by performing a multisampled derivative, however, even though the stability limits might be extended, the oversampled approach might increase noise amplification problems. An appropriate filtering solution is required in the feedback path in order to reduce noise amplification and eliminate aliasing problems, without compromising the stability, as a result of a modification in the active damping feedback path. This work examines the limits of applicability of the capacitor voltage derivative strategy taking into account the filters used in the AD path, providing experimental results to validate the presented approach.Publication Open Access Capacitor current feedback active damping with lagged compensator for DFIG wind turbines with LCL filter(IEEE, 2020) Rosado Galparsoro, Leyre; Samanes Pascual, Javier; Gubía Villabona, Eugenio; López Taberna, Jesús; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y ElectrónicaSeveral active damping strategies have been proposed in the literature for grid-connected converters with LCL filter but there are not specific strategies for DFIG wind turbines. In this system, there is an interaction between the two converters of the back-to-back conversion structure, which must be properly modeled in order to design effective damping strategies for the LCL filter resonant poles. This paper proposes a robust active damping strategy for DFIG wind turbines with LCL filter that considers the special features of this system. In this technique the filter capacitor current is fed back through a lag compensator that adjusts the delay of the feedback loop to emulate a virtual impedance that has dominant resistive behavior in the range of possible resonance frequencies. It is shown that a similar damping of the LCL filter resonance is achieved when the strategy isimplemented in either of the two converters.Publication Open Access Sensorless active damping strategy for parallel interleaved voltage source power converters with LCL filter(IEEE, 2017) Samanes Pascual, Javier; Gubía Villabona, Eugenio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaGrid-connected pulse-width modulation converters with LCL filters are widely extended as an interface for renewable energy generating systems. Those filters arise stability issues due to the filter resonance, which, must be damped, preferably by active damping methods, to avoid additional power losses. In some applications, such as offshore wind energy conversion systems, where high power converters are connected to low voltage networks, the commutation frequency is limited to low values to reduce the power losses and the resulting filter components are bulky. For this reason, in addition to its higher current handling capabilities, the use of power converters in parallel with the application of advanced modulation strategies, such as interleaving, is gaining importance. In this structure the filter components can be reduced, setting the filter resonance frequency at a higher value. As a consequence, the filter resonance frequency is close to the Nyquist frequency, complicating the implementation of some of the existing active damping solutions. In this work, an active damping approach based on a third order digital filter is proposed to stabilize the system. The robustness of the solution is investigated against grid inductance variations and the grid current harmonic content will be tested to comply with the most demanding grid codes. The proposed active damping strategy does not require extra sensors and can be easily designed by examining the open loop Bode plots. It is suitable to stabilize the LCL filter with a resonance frequency close to the Nyquist frequency, where some of the existing active damping approaches are unable to damp the system. The proposed method can be also an appropriate solution for existing grid connected power converters with stability issues due to changes in the effective grid impedance at which they are connected.