[EN] Harmonics generated by non-linear loads must be avoided to increase the overall quality of the power supply of power grids and microgrids. In this context, studies have been developed to improve the performance of active power filters. This work develops a control scheme for active filters composed of two Voltage Source Inverters that share the harmonics to be controlled. One of the inverters works at low frequency and controls the reactive power and the low order harmonics. Other inverter works at a high switching frequency and controls the high frequency harmonics. This inverter handles most of the harmonics, but its Root Mean Square (RMS) current is approximately 20% of the RMS current handled by the active power filter, so switching losses are significantly reduced., This research was funded by the Spanish Ministerio de
Asuntos Económicos y Transformación Digital and the
European Regional Development Fund (ERDF) under Grant
PID2021-122835OB-C22.

[EN] This paper presents an analytical study of the dynamics of a three-phase, grid-connected photovoltaic inverter based on the B4 topology. Following a similar procedure to that used for conventional B6 inverters, the inverter has been modelled and controlled in a synchronous reference frame by introducing the concept of 'positive sequence equivalent control signals'. A stability analysis of the control loops is presented, considering parametric variations in photovoltaic field voltage and grid inductance. A control strategy incorporating PI controllers, along with decoupling terms to enhance dynamic performance, has been implemented. To further evaluate the behavior of the inverter, additional simulations are conducted under ideal and distorted grid conditions. These tests evaluate harmonic propagation, DC bus voltage ripple and overall system performance in the presence of grid disturbances., This research was funded by the Spanish Ministerio de Ciencia e Innovación and the European Regional Development Fund (ERDF) under Grant PID2021-122835OB-C22.

[EN] The DC-Bus Signaling (DBS) is a proven method
to coordinate different agents in a microgrid, using the DCvoltage of the microgrid as a communication signal. The droop
control applied in a dc-microgrid leads to an error in the voltage
regulation of the microgrid, while the power sharing among
converters in such microgrid is achieved. By using the voltage at
each node of the grid as the DBS signal, the behavior of the
different agents in a microgrid can be managed. In this paper
the DBS technique is used to coordinate conventional
generators, Energy Storage Systems and loads in a microgrid.
The control laws proposed are tested in an experimental
microgrid., This research was funded by the Spanish Ministerio de Asuntos
Económicos y Transformación Digital and the European Regional
Development Fund (ERDF) under Grants RTI2018-100732-B-C21 and
PID2021-122835OB-C22.

[EN] Active Power Filters (APF) for reducing current harmonic distortion have been widely used in both grids and microgrids. This work proposes a topology for an APF consisting of two Voltage Source Inverters (VSIs) connected in parallel to the same DC-link, which saves space and reduces cost compared to independent APFs. One inverter operates at a low switching frequency and compensates for low-order harmonics. The second inverter operates at a high switching frequency to target high-frequency harmonics. As the high-frequency inverter handles only around 25% of the total RMS current managed by the overall APF, switching losses are significantly reduced. However, connecting inverters in parallel produces circulating currents that can have an adverse effect on the system. In this work, circulating currents are cancelled by controlling the zero-sequence component of the currents in the two inverters., This research was funded by the Spanish Ministerio de Asuntos
Económicos y Transformación Digital and the European Regional
Development Fund (ERDF) under Grant PID2021-122835OB-C22.

[EN] Electronic converters connected to a microgrid must
contribute to its stability while sharing the load proportionally of
their nominal power. This contribution presents the Universal
Control technique in a Stationary Reference Frame (UCStRf). The
UCStRf is a control technique that implements the power-tofrequency droop law for inverters connected to a microgrid while
implementing an output virtual impedance loop to ensure the
stability of the converter in spite of variations of the microgrid
parameters. Section II presents the UCStRf control technique;
section III details the virtual output impedance design criteria;
section IV develops the small-signal model of the Active Power Loop
(APL); section V details the design of the control loops to ensure the
stability criteria; and section VI validates the proposed control
scheme by means of simulations., This work was supported by the Spanish "Ministerio de
Ciencia e Innovación" and the European Regional Development Fund (ERDF) under Grant PID2021-
122835OB-C22.

[EN] This paper analyzes the performance of several
topologies of grid-connected inverters. For that purpose, a
comparative analysis has been carried out among a classical sixswitch three-phase inverter (B6) and several alternatives of the
four-switch three-phase inverter topology (B4). As figures of
merit to carry out the comparative study, the efficiency, the total
harmonic distortion of the current in the grid, the unbalance of
the grid currents and the cost of each alternative have been
considered. The performance of the inverters has been
evaluated by means of realistic simulations, which have been
carried out with PSIMTM software., This research was funded by the Spanish Ministerio de Asuntos
Económicos y Transformación Digital and the European Regional
Development Fund (ERDF) under Grants RTI2018-100732-B-C21 and
PID2021-122835OB-C22.

[EN] The parallel connection of inverters has some advantages like modularity and redundancy. Nevertheless, the connection in parallel of inverters produces circulating currents that cause adverse effects in the system. In this work, it is presented a control technique for the elimination of the circulating currents. In parallel inverters, the circulating currents agree with the zero-sequence component of the phase currents, so they are suppressed by controlling the zerosequence component of the phase currents of the inverters. Simulation results have been presented considering the connection in parallel of two 5 kW inverters connected in parallel in islanded mode. The results have been obtained by considering linear and non-linear AC loads., This research was funded by the Spanish Ministerio de
Asuntos Económicos y Transformación Digital and the
European Regional Development Fund (ERDF) under Grants
RTI2018-100732-B-C21 and PID2021-122835OB-C22.