Javier Perez Ramirez

Designing propulsion systems for agricultural drones involves a repetitive process that is both expensive and time-intensive. At the same time, conducting comprehensive experimental tests demands specialized equipment and strict safety protocols. In this work, the design and assessment of the propulsion system (propeller, motor, and battery) for large-sized drones in agricultural applications are conducted using numerical methods. To properly predict and validate the performance of a brushless direct current motor, a three half-bridge inverter circuit, featuring a trapezoidal commutation, is implemented and constructed. First, the propeller is studied using the finite volume method, obtaining a maximum variation of 6.32% for thrust and 10.1% for torque. Additionally, an electromagnetic analysis on a commercial brushless direct current motor (BLDC) using JMAG software from JSOL corporation (JMAG designer 23.2, Cd.Obregón, México) resulted in 4.43% deviation from experimental electrical measurements. The selected propulsion system is implemented in a 30 kg drone, where motor performance is evaluated for two instants of time in a typical agriculture trajectory. The findings demonstrate that numerical methods provide valuable insights in large-sized unmanned aerial vehicle (UAV) design, decreasing the experimental tests conducted and accelerating implementation time.

Typically, in electrical microgrids (MG), the grid-forming type converter (GFRTC) includes a battery pack at its DC bus; thus, the GFRTC is modelled as a voltage source. In contrast with papers reported in recent literature, where the GFRTC with a battery pack is seen as a voltage source, this work proposes a GFRTC which can be used without a battery pack; with this, the GFRTC operates as a smart load to form the voltage at the point of common coupling (PCC); this is possible, as long as the smart load is supported by a grid-following type converter (GFLTC). This battery-less GFRTC proposal ensures a suitable operation of the isolated MG under linear and nonlinear load conditions. Also, this work proposes a control strategy for both GFRTC and GFLTC with a photovoltaic array. The test results showed that the control proposal allows to form a correct PCC voltage, ensuring a suitable operation of the isolated MG; this while the battery pack is: connected, disconnected, and reconnected to the GFRTC DC bus. This GFRTC proposal is very attractive for isolated MGs where the GFRTC battery pack must be replaced or reconfigured because of new demand profiles, without interrupting the isolated MG operation.

In an islanded microgrid, the grid-forming (GFM) converters are used to stablish an AC voltage whereas the grid-following (GFL) converters rely on the formed AC voltage to supply the loads. This paper presents a system consisting of a GFM converter with a battery pack and a GFL converter with a photovoltaic (PV) array. For this work, it is assumed that the microgrid is in islanded mode. The proposed control strategy allowed the GFM converter to form a stable AC voltage, regulate its DC voltage, and simultaneously charge or discharge the batteries without being affected by load changes. An outstanding capability for the GFM converter was proposed as part of the control strategy, which is carrying out the charging of the batteries during islanded mode while the AC voltage is being formed. This is suitable for the case when there is surplus energy in a microgrid, and the demand is less than the available energy. It also enabled the GFL converter to extract the required power from the PV array. The proposed GFL converter control strategy, which depends on the GFM control strategy, is simple and easy to implement, avoiding the use of complex PV power extraction algorithms. The simulation tests demonstrated that the microgrid was not significantly affected by load changes or by fluctuations of irradiance.

Both the transition from grid-tied mode (GTM) to islanded mode (ISM), denoted as GTM-ISM transition, and the transition from ISM to GTM, denoted as ISM-GTM transition, are one of the main topics in AC electrical microgrid (MG) research. Within the MG, the grid-forming power converter (GFRC) is responsible to carry out both the GTM-ISM and ISMGTM transitions. Usually, the GFRC includes a power supply source at the DC bus; in most cases, this DC source is a battery pack. In abnormal mains conditions, the MG must operate in ISM, then, the GFRC uses the battery power to generate the voltage at the point of common coupling (PCC) during the GTM-ISM transition; in the same way, the GFRC uses the power from the battery pack to sustain the PCC voltage during ISM and for synchronizing it when the nominal conditions of the mains are recovered. The transition of MG operating modes with a battery-less GFRC in the literature has not been reported. Thus, this paper presents a control scheme proposal to perform both GTM-ISM and ISM-GTM transitions with a battery-less GFRC. The results showed the capacity of the battery-less GFRC to operate as smart load during both GTM-ISM and ISM-GTM transitions. This battery-less GFRC proposal highlights a contribution within the research of GFRC units, since the GFRC operation has always been reported using a power supply source at the DC bus, mainly battery packs, but not using a battery-less GFRC working as a smart load for the generation of the PCC voltage.

Primary controls for performing the transitions between grid-tied mode (GTM) and islanding mode (ISM) of an AC microgrid (MG) are proposed. The MG includes a grid-forming (GFR) unit wi ...

The Microgrid (MG) operating modes are Grid-Tied Mode (GTM) and Islanded Mode (ISM). However, the transitions from GTM to ISM (GTM-ISM) and from ISM to GTM (ISM-GTM) are currently studied as operation modes. To correctly perform GTM-ISM and ISM-GTM, in this paper an Islanding Detection Algorithm (IDA) and Grid-Synchronization Algorithm (GSA) are developed. The development of IDA and GSA is based on the DQ transformation and the IEEE 1547 Standard. Both IDA and GSA operate together as a secondary control level to provide synchronizing signals to the primary control level. The results show a correct IDA and GSA performance, which allowed the Grid-Forming Type Converter (GFTC) to be capable of carrying out both GTM-ISM and ISM-GTM, correctly. This is possible because of the cascade control schemes outstandingly perform tasks such as: to extract mains power, to charge the battery, to regulate the DC bus voltage, and to synchronize and to regulate the GFTC output voltage.

In this paper, a grid-feeding power converter topology is proposed so that a photovoltaic array and the mains, if necessary, can charge a battery pack. The proposal presented also considers extracting the maximum power of the photovoltaic array. The grid-feeding power converter topology is composed by a boost DC-DC converter and a bidirectional DC-AC converter connected to the mains, the control strategies for each converter are also presented. The control scheme for the boost DC-DC converter includes a maximum power point tracking algorithm. The control scheme for the bidirectional DC-AC converter has two operating modes, current-control mode and voltage-control mode. To validate the performance of the grid-feeding converter simulation results are presented. The grid-feeding converter control strategy successfully carries out the power management between the mains, the PV array and the battery.

To avoid the negative effects of using a control signal with a ripple, which is generated by the feedback of measured active power filter (APF) variables, a nonlinear observer is employed in this paper. The observer design, through the use of exact TS models and Lyapunov-based LMI conditions, is achieved. Both the APF output current and the DC voltage are estimated by the observer, and they are used in the cascade control feedback. In this way, high gains in the inner control loop are employed, giving place to a control signal without undesired harmonic components or overmodulation. This allows an APF performance improvement for compensation tasks and for reducing the undesired components injection to the mains. A simulation and experimental comparison between APF results using observer and APF results without using observer is presented. Better results are achieved for the observer version case, reducing the THD from 47.6% to 4.8% in experimental conditions, satisfying the IEEE Standard 519^TM-2014. Also, load change tests are carried out, where the stability of the system is kept. Moreover, by using the observer, a DC voltage sensor was not required, reducing the number of system sensors.