Power calculation algorithm for single-phase droop-operated inverters considering nonlinear loads and unsing n-order SOGI filtering

The average active and reactive powers, P and Q, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, the droop method algorithm should employ low-pass filters (LPF) with very low cut-off frequency to minimize the distortion impact in the provide droop amplitude and frequency references. This situation forces the droop control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed in literature to increase the droop velocity, but the issues derived from the sharing of nonlinear loads had not been properly considered. This work proposes a novel method to calculate P and Q based on the fundamental components of the inverter's output voltage and current and using the measured phase angle between the output voltage and current. The method is used under normal and highly distorting conditions due to the sharing non-linear loads. The fundamental components are obtained by means of the highly filtering capability provided by norder cascaded second order generalized integrators (nSOGI). The proposed method leads to faster and more accurate P and Q calculations that enhances the droop-method dynamic performance. Simulations are provided to validate the proposal.Peer ReviewedPostprint (published version

A power calculation algorithm for single-phase droop-operated-inverters considering linear and nonlinear loads HIL-assessed

The active and reactive powers, P and Q, are crucial variables in the parallel operation of single-phase inverters using the droop method, introducing proportional droops in the inverter output frequency and voltage amplitude references. P and Q, or P-Q, are calculated as the product of the inverter output voltage and its orthogonal version with the output current, respectively. However, when sharing nonlinear loads these powers, Pav and Qav, should be averaged by low-pass filters (LPFs) with a very low cut-o frequency to avoid the high distortion induced by these loads. This forces the droop method to operate at a very low dynamic velocity and degrades the system stability. Then, di erent solutions have been proposed in literature to increase the system velocity, but only considering linear loads. Therefore, this work presents a method to calculate Pav and Qav using second-order generalized integrators (SOGI) to face this problem with nonlinear loads. A double SOGI (DSOGI) approach is applied to filter the nonlinear load current and provide its fundamental component to the inverter, leading to a faster dynamic velocity of the droop-based load sharing capability and improving the stability. The proposed method is shown to be faster than others in the literature when considering nonlinear loads, while smoothly driving the system with low distortion levels. Simulations, hardware-in-loop (HIL) and experimental results are provided to validate this proposal.Peer ReviewedPostprint (published version

HIL-assessed fast and accurate single-phase power calculation algorithm for voltage source inverters supplying to high total demand distortion nonlinear loads

The dynamic performance of the local control of single-phase voltage source inverters (VSIs) can be degraded when supplying to nonlinear loads (NLLs) in microgrids. When this control is based on the droop principles, a proper calculation of the active and reactive averaged powers (P–Q) is essential for a proficient dynamic response against abrupt NLL changes. In this work, a VSI supplying to an NLL was studied, focusing the attention on the P–Q calculation stage. This stage first generated the direct and in-quadrature signals from the measured load current through a second-order generalized integrator (SOGI). Then, the instantaneous power quantities were obtained by multiplying each filtered current by the output voltage, and filtered later by utilizing a SOGI to acquire the averaged P–Q parameters. The proposed algorithm was compared with previous proposals, while keeping the active power steady-state ripple constant, which resulted in a faster calculation of the averaged active power. In this case, the steady-state averaged reactive power presented less ripple than the best proposal to which it was compared. When reducing the velocity of the proposed algorithm for the active power, it also showed a reduction in its steady-state ripple. Simulations, hardware-in-the-loop, and experimental tests were carried out to verify the effectiveness of the proposal.Peer ReviewedPostprint (published version

Assessment of the Royal Decree 244/2019 in the Spanish Electrical Regulatory Framework considering power quality issues related to harmonic distortion associated to nonlinear loads in grid-connected microgrids

Postprint (published version

Comparison between different droop based control techniques and a virtual control oscillator

This work presents a literature review about control techniques for parallel connected power inverters under microgrid applications. Some control strategies, based on droop control for parallel inverters of distributed generation units in an ac distribution system will be presented in this work. Finally, an important method called Virtual Oscillating Control (VOC) is suggested for connecting voltage source inverters. Inverters are able to work in parallel with a constant-voltage constant frequency system, as well as with other inverters and also in standalone operation. The different power sources can share the load also under unbalanced conditions. Throughout this work several simulation results are presented in order to demonstrate the behaviour the behavior of the different control strategies tested.Peer ReviewedPostprint (published version

Research facilities for renewable energy management considering distributed generation based on microgrids

The aim of this work is to establish a guideline for the design of research facilities in the field of Energy Management in Distributed Generation in Electric Power Systems. First, a National trend towards the implementation of the main Renewables Energies Technologies is identified, yielding Wind and Photovoltaic Energy as the vanguard. A short review of the Architecture of the Hierarchical control of Microgrids is then presented to continue to analyse the future trends in research on Distributed Generation based on Microgrids. A short review of some of the main stakeholders in Distributed Generation research is carried out in order to evaluate research trends. Finally, after the introduction of the existing facilities at FIE-UMSNH in the field of Renewables Energies, a proposal of architecture of research facilities for the integration of Microgrids in the Grid Network is shown. All the process has been carried out considering IEEE standards related to Microgrids as well as considering the Mexican National Regulatory framework referred to the Energy Transition.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaPostprint (published version

Power calculation algorithm for single-phase droop-operated inverters considering nonlinear loads

The average active and reactive powers, Pav and Qav, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, low-pass filters (LPF) with very low cut-off frequency should be used to minimize the distortion impact in the amplitude and frequency references provided by the droop equations. This forces the control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed to increase the droop operation velocity in literature, but with the consideration of only sharing linear loads. The issues derived from the sharing of nonlinear loads had not been properly considered. This paper proposes a method to calculate Pav and Qav using second order generalized integrators (SOGI) that increase the velocity of the droop control algorithm considering nonlinear loads as the design worst case scenario. Then it is employed a double SOGI (DSOGI) approach to filter the current non-sinusoidal waveform and provide the fundamental component, which results in a faster transient response and improves the system's stability. The proposed calculation method shows to be faster than other approaches when considering nonlinear loads. Simulations are provided to validate the proposal.Peer Reviewe

Power calculation algorithm for single-phase droop-operated inverters considering nonlinear loads

The average active and reactive powers, Pav and Qav, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, low-pass filters (LPF) with very low cut-off frequency should be used to minimize the distortion impact in the amplitude and frequency references provided by the droop equations. This forces the control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed to increase the droop operation velocity in literature, but with the consideration of only sharing linear loads. The issues derived from the sharing of nonlinear loads had not been properly considered. This paper proposes a method to calculate Pav and Qav using second order generalized integrators (SOGI) that increase the velocity of the droop control algorithm considering nonlinear loads as the design worst case scenario. Then it is employed a double SOGI (DSOGI) approach to filter the current non-sinusoidal waveform and provide the fundamental component, which results in a faster transient response and improves the system's stability. The proposed calculation method shows to be faster than other approaches when considering nonlinear loads. Simulations are provided to validate the proposal.Peer Reviewe

Power calculation algorithm for single-phase droop-operated inverters considering nonlinear loads and unsing n-order SOGI filtering

The average active and reactive powers, P and Q, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, the droop method algorithm should employ low-pass filters (LPF) with very low cut-off frequency to minimize the distortion impact in the provide droop amplitude and frequency references. This situation forces the droop control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed in literature to increase the droop velocity, but the issues derived from the sharing of nonlinear loads had not been properly considered. This work proposes a novel method to calculate P and Q based on the fundamental components of the inverter's output voltage and current and using the measured phase angle between the output voltage and current. The method is used under normal and highly distorting conditions due to the sharing non-linear loads. The fundamental components are obtained by means of the highly filtering capability provided by norder cascaded second order generalized integrators (nSOGI). The proposed method leads to faster and more accurate P and Q calculations that enhances the droop-method dynamic performance. Simulations are provided to validate the proposal.Peer Reviewe