A system and a method for powering a plurality of electrodes, an electrical weeding device, and, a vehicle

Abstract

The present invention relates to a system for powering a plurality of electrodes (31, 500, 600) of an electrical weeding device (100, 200, 400), comprising: a power input (20); a shared switching arm (23) connected to the power input (20); a plurality of power cells (5) connected to the shared switching arm (23), each of the plurality of power cells (5) comprising: an inverter switching arm (10), wherein the inverter switching arm (10) forms with the shared switching arm (23) a Full Bridge converter; a gate driver (16) connected to the inverter switching arm (10), wherein the gate driver (16) is configured to drive its inverter switching arm (10) upon receiving an activation signal; and a transformer (11), wherein each inverter switching arm (10) is connected to the shared switching arm (23) in a parallel configuration and to a primary side of the transformer (11), and the secondary side of each transformer (11) is connected in a series configuration to a full-wave rectifier bridge (12), the full-wave rectifier bridge (12) is connected to a LC filter (13) and the LC filter (13) is further connected to the plurality of electrodes (31, 500, 600); a control unit (30) configured to determine an output power level of the plurality of power cells (5) based on a weed pressure in a weeding area, and wherein the control unit (30) is further configured to send the activation signal to each gate driver (16) of the plurality of power cells (5) to adjust the phase shift between the inverter switching arms (10) and the shared switching arm (23), wherein the phase shift defines the output voltage to be applied in the plurality of electrodes (31, 500, 600) by means of the Full Bridge converter. The present invention is also related to a method for powering a plurality of electrodes (31, 500, 600) of an electrical weeding device (100, 200, 400), the electrical weeding device (100, 200, 400) and a vehicle (120) carrying the electrical weeding device (100, 200, 400).

Description

A SYSTEM AND A METHOD FOR POWERING A PLURALITY OF ELECTRODES, AN ELECTRICAL WEEDING DEVICE, AND, A VEHICLE FIELD OF THE DISCLOSURE

[0001] The present invention relates to the field of electrical weeding systems, devices, and processes. More specifically, the invention relates to a system and method for powering a plurality of electrodes of an electrical weeding device that allows to easily adjust the output voltage in the electrodes in view of a plurality of resistance band levels.DESCRIPTION OF RELATED ART

[0002] Efficacy on systemic plant control is direct consequence of killing the plant’ s root system, not the air system. A plant might recover if its air system is somewhat damaged, but it will certainly die if its root system becomes unable to send nutrients to the rest of the plant, that necessarily will perish from nutrient deficiency. Ideally, the efficacy of plant electrocution can be considered to be binary (plant is dead or not dead). The efficacy can be considered as the relation between the Fatal Energy Consumption needed at the individual plant’s root and the volume of the root system.

[0003] Active power in a given electrical circuit is given by the average of the instantaneous power over a period of time (T). As long as the instantaneous power is the product of the instantaneous voltage by the instantaneous current, it can be written as:

[0004] For a constant voltage ( (f) = V) and current (z(f) = T) functions, it can be simplified as follows,P = V * I

[0005] where P is the active power, V is the voltage across the circuit terminals and I is the current provided by the source.

[0006] FIG. 1A illustrates the amplitude and peaks of a generic sinusoidal waveform and FIG. IB illustrates the peak voltage and peak-to-peak voltage of sinusoidal waveforms. FIGs. 1A and IB are presented for better understanding of the electrical concepts used to explain the working of the present invention.

[0007] Additionaly, Energy is Power consumed over a period of time, which may be given by:E = P * t

[0008] where E is energy in Watt-seconds, P is the active power and t is a time interval. Therefore, for given constant voltage V and a certain time interval applying this voltage across the plant, a lower total resistance means more power flows through the plant, and a higher total resistance means less power flows through the plant. Total resistance or load or load resistance is a series of parallel plant resistances and soil resistances that exist between the electrodes that approximates the total impedance experienced by the electrodes of the equipment.

[0009] There may be a plurality of electrodes and a plurality of plants, the electrodes may all be directed to the plants, or to the plants and the soil, but at least one active electrode should always be directed to the targeted plants.

[0010] Considering that such system is always constrained by the maximum power output of an alternating current (AC) or direct current (DC) power source, the ideal system must provide constant power regardless of the total resistance the electrodes experience.

[0011] In order to maximize the effectiveness of the treatment, it is necessary to maximize energy consumed, and the energy consumed is the integral of the instantaneous power over time, which is by itself dependent on the instantaneous voltage, as shown above. Therefore, the ideal system should preferably provide a DC voltage output that ensures constant power, given the everchanging load of real field operating conditions.

[0012] The DC voltage values should lie in the range of 1 kV - 10 kV, which is the range necessary to ensure constant power delivery in the most common load range of a regular field operation. The peak DC voltage is defined as the maximum DC voltage. In particular cases, such as railway dead beds, highways and urban roads, these values can reach up to 15 kV, 20 kV, 30 kV or even 40 kV.

[0013] This means, ideally, that the processed electrical output power should not be a waveform with repeating shapes, but rather a DC power source that is able to vary its voltage level according to the load so as to ensure constant power delivery. Given the cycles of charge and discharge of the capacitors of the voltage multiplier, when the load is low, parasite voltage peaks may be seen, but should be kept as low as possible and always below IkV.

[0014] Parasitic peak voltages may arise as the charge of the capacitors decrease faster than the input from the secondary of the transformer can charge. This effect is especially high when either loads or switching frequencies are too low. When loads are too low, the capacitors discharge too fast and when switching frequencies are too low, the PWM or similar controls cannot act fast enough to counter act the discharge. Typical switching frequencies are above 1kHz and below 1MHz.

[0015] The parasitic peak voltage is defined as the peak amplitude of the repeating units of the parasitic waveform which superimposes the variable DC voltage, and may take form as ripples, commonly found in rectifiers. Peak-to-peak voltage is greater than the peak voltage and typically twice that of a sinusoidal waveform. The parasitic waveform is the repeating unit defined as a unit that repeats with substantially the same form, e.g., it may comprise waveforms of substantial the same shape including when the amplitude and / or duty cycle or period is adjusted for control of the processed electrical energy. These definitions can be found indocument “WO20 16016627 - APPARATUS AND METHOD FORELECTRICALLY KILLING PLANTS”.

[0016] Weed pressure is a function of the density of weeds per area, organic mass per area and type of weeds. The weed pressure faced by the equipment can vary, changing with it the energy needed to ensure proper weed control. As the ideal equipment should be able to always output constant power to maximize the use of the power source constraints, in the case of any surplus energy, due to low weed pressure, it is more efficient to adjust power delivery by means of a sensor that measures weed pressure, or to just speed up the equipment, reducing the energy per area.

[0017] Traditional systems that have AC or greatly varying voltages with fixed waveforms with high voltage peaks, such as the ones exemplified in documents WO2013051276, WO2015119523, WO2016016627 and EP3744173 have a hugely varying power delivery through changing resistances that will be sub-optimal on its energy efficiency usage due to hugely varying energy consumption at the plant, leading to either uneven quality of application or will require a much larger power input capability with higher energy consumption to ensure enough energy is delivered when resistances are high because plants or plants-soil or plants-soil-plants resistive systems vary greatly in practical applications. Such behavior can be seen in FIG. 2. It is possible to smooth the instantaneous power close to the average power delivered to the load through continuity switches and controls such as PWM and PDM, as taught in EP3744173, but this accounts for average power, not continuous power delivery, which can only be achieved by a continuous DC that varies its voltage level to account for dynamic resistance changes to ensure continuous power delivery, as the present invention proposes.

[0018] For the purposes of this invention, the resistive load is the sum of the resistance seen by the electrode terminals. It can be composed either of the sum ofthe serial resistances of targeted plant or plants and the soil, or a plant or plants, soil, plant or plants arrangement; and the usual operational load range of the resistive system varies between 0.5 kQ to 15 kQ, but it may go up to 35 kQ or even higher in urban or railroad beds. The load range may change slightly according to the crop or geography the invention is set to operate.

[0019] Document EP3744173 explains thoroughly the use of PWM and PDM to control for power in electrical weeding operations. It offers a constant voltage architecture as the output of a transformer, and the PWM and PDM controls work as a continuity switch that controls the power by controlling the continuity of the current. In other words, it is a constant AC voltage supply that is controlled by continuity to limit current, offering a constant power source. This is a sub-optimal solution considering the output is not constant DC that only varies with the dynamically changing loads to ensure constant power delivery.

[0020] Document EP19152341 describes a frequency converter, a transformer and a capacitive voltage multiplier composed of diodes and capacitors. To ensure semi-constant power, it uses the impedance matching implicit of the voltage multiplier, which happens in a self-adjustable way, without the necessity of a control strategy implementation. This happens to a certain degree because when the resistive load tends to a low value (short-circuit situation), the voltage multiplier presents a series impedance reflected to the primary that, associated with the external inductor of the filter, protects the transformer against high short-circuit currents. When the load tends to a high value (open circuit situation), all the capacitors of the voltage multiplier are charged, increasing the secondary voltage peak, but still limiting it to a maximum value equals the multiplier stage. In other words, when the load is higher than the load that delivers maximum power, the power diminishes because the converter cannot increase the voltage enough to ensure constant power, and when the load is lower than the load that deliver maximum power, the internalimpedance reflected increases, lowering the power delivered. A typical power curve (y axis in watts - w) against the load (x axis in kilo ohms - kQ) can be found in FIG. 3. The actual graph with the power curve of the invention shown in that patent can be found in FIG. 4. Although it has some degree of power control, it is semi-constant, given the nature of the power output curve of a regular voltage multiplier.

[0021] Document WO2013051276 contains a frequency converter, a transformer and a capacitive voltage multiplier composed of diodes and capacitors, more specifically a Cockroft- Walton circuit for several uses. In this invention, the concept is to ensure a voltage boost without impedance matching, multiple peaks of voltage, constant or semi-constant power, nor PWM controls. As proposed, a constant power delivery is optimal for electrical weeding, therefore, it may be used, but it would not fit all scenarios, especially the ones where the load level is not the one where the system outputs peak power or the load varies dynamically, which is the operational scenario of a regular electrical weeding operation. Therefore, it is not suited to the target operation of the present invention.

[0022] Document WO2015119523 contains a feedback assembly of transformers and voltage multipliers. It solves the challenge of the dynamically changing load that electrical weeding devices face through a feedback loop that feeds the final transformer outputting AC or highly varying voltage output with a constant voltage waveform. Output coming from a transformer directly means that this varying voltage will have a power curve in time that is not constant, therefore its output cannot provide the ideal constant DC that varies its voltage according to the output load ensuring constant power delivery. Therefore, although it can vary its voltage to face a dynamically changing load, it cannot provide the optimum voltage constantly through a constant DC that varies its voltage according to the output load ensuring constant power delivery. It may provide some degree of impedance matching or some degree of semi-constant power, but as high peaks are parasites tothe optimum voltage and constant power delivery, it cannot provide an ample range of semi constant power for a given range of loads, nor can it offer a constant DC output that only varies according to the load, keeping the power output constant. For those reasons, the invention described in WO2015119523 is not optimal to the target objective of the present invention.

[0023] Document WO2016016627 relates to the use of outputting processed electrical energy that comprises a waveform with a frequency of at least 18 kHz or more, with peak voltages of at least IkV. Although this invention may output a functioning equipment, with the advantages stated in the referred document, it is sub-optimal. As described, the invention of WO2016016627 cannot deal with the varying impedances to output constant (neither semi-constant, for that matter) power. Moreover, the voltage peaks of more than IkV reduce the efficacy of the use of electrical energy by not delivering constant DC that only varies with the dynamically changing loads to ensure constant power delivery. WO2016016627 proposes that the use of higher frequency to be less dangerous to humans, but this effect is offset by the need for a much higher voltage output, because to achieve the same power a system with high voltage peaks will need higher peak voltage than a system with continuous DC. This effect is much increased when taken into consideration that the power capabilities of such a system will have to be even higher to account for varying impedances, even if it has a PWM system to ensure that average power is constant. Average power being constant does not mean peak power is constant or closely so.

[0024] Document EP3415004B1 relates to the use of capacitors as means of storing energy that is then pulsed to the vegetation. This creates a continuous downward voltage curve on every triggering of the device, which reduces efficiency as the capacitors discharge and less energy is applied. This document also demands a high-voltage pulse generator to ensure a minimum voltage of the application.Limiting the voltage to a minimum is not usable in very large loads, where applied voltage needed may be quite low. Moreover, working with a voltage minimum and letting the power vary according to the load will not be optimum if compared to a system that keeps power constant, as is proposed in the present invention.

[0025] The international application WO2023178398A1, entitled “Electrical Weeding Device” solves the prior-art problems through the construction and combination of two new features. The teachings of WO2023178398A1 are fully incorporated into this description for ready reference. Firstly, a multiple setting of different values for the voltage multiplier. For instance, paralleling multiple voltage multipliers with different peaks may provide a power curve with multiple peaks, where the power output is stable at a much wider load range. Secondly, a control unit comprising a PWM module and at least one sensor, wherein the PWM module is coupled to the at least one electronic converter adjusting the duty cycle of the PWM module according to the load; and limiting parasitic voltage peaks to IkV. Voltage peaks relate to small undesired voltage variations due to capacitor discharge, or harmonic interactions between the components. These peaks diminish as frequency and capacitance increases and must be kept as low as possible to achieve higher efficiency.

[0026] The teachings of EP3437 shows that the state of the art has some degree of power control, the solutions of the prior art are semi-constant, given the nature of the power output curve of a regular voltage multiplier. To improve upon this, a multiple setting of different values for the voltage multiplier can be constructed. For instance, paralleling multiple voltage multipliers with different peaks may provide a power curve with multiple peaks, where the power output is stable at a much wider load range. The results of a combination of two and three of those voltage multipliers can be seen in FIG. 5 and FIG. 6, where two and three peaks can be seen, respectively, and where a growing stable area of semi-constantpower can be found. It is an objective of this particular invention to provide use of small, cheap, high-power factor efficient and effective electronic converter to control for constant power output with minimal voltage parasitic fluctuations.

[0027] For optimal usage, it is desirable to have constant power across a large range of loads. This may be provided through more complex arrays and combinations of voltage multipliers resulting in multiple peaks of power output to ensure a semi-constant power delivery throughout a larger range of resistances such as shown in FIG. 6, and in contrast with FIG. 4, reducing the need to use PWM duty cycles that might be too low, which are potentially more lossy and less energy efficient. The controlled PWM signal ensures that the voltage output does not have parasitic peak voltages of more than IkV, and that the voltage output to be connected to the at least two electrodes is controlled to ensure that the DC power output is constant throughout the usual load range.

[0028] If a pulse width modulation (PWM), pulse density modulation (PDM) or any other similar control used as a feedback loop is incorporated to the improved design, ensuring that the capacitor charge will limit the output voltage to the exact degree that outputs the desired power (i.e., 250 W in this example), the converter may find a large load range where it can function with stable constant power, as shown in FIG. 7.

[0029] For that, the needed information for the feedback loop is the output power. If the output power deviates upwards, the PWM (or similar) decreases the duty cycle, if it deviates downwards, it increases the duty cycle.

[0030] Duty cycle is the amount of time a digital signal is in the “active” state relative to the period of the signal. Duty cycle is usually given as a percentage. For example, a perfect square wave with equal high time and low time has a duty cycle of 50%, as shown in FIG. 8. The duty cycle controls the gates of the inverter(usually IGBTs are used). The proposed system changes the duty cycle to ensure higher duty cycles when power reduces and lower duty cycles if the power increases due to, for instance, a change in load, as exemplified in FIG. 9.

[0031] The duty cycle adjustments will provide more power keeping the charge of the capacitors of the voltage multiplier at a lower voltage state when the load is lower and keeping the charge of the capacitors of the voltage multiplier at a higher voltage state when the load is higher. This means that with the combination of an architecture of voltage multipliers with multiple voltage peaks throughout a continuum of loads with a PWM control that ensure power delivery never goes above a certain value, it is possible to provide constant power throughout a large load band, and through a dynamically varying load. According to Ohm’ s law, the relationship between power, voltage and load should follow FIG. 10 for a constant power source.

[0032] The addition of an inductor and / or inductive / capacitive filter may allow for the inverter’ s IGBT to work with resonant switching, reducing its losses and increases the converter’s efficiency. The IGBT’s in this case is tuned at the resonance between the external inductor and the total capacitance reflected to the transformer’ s primary or directly to the voltage multiplier, considering the effects of the variable load and the voltage multiplier.

[0033] Turning to the electronic converter according to the present invention it comprises a power inverter, a transformer coupled to the power inverter and a voltage multiplier coupled to the transformer. Power inverters are power electronic devices capable of converting direct current energy to alternating current energy in an almost lossless manner. This is possible by employing an assortment of electronic switches, usually transistors (bipolar junction, MOSFET or IGBTs selected according to the switching frequencies), which are commuted (changing from on / off states periodically) in synch by a gate controller to achieve a determined reference signal. The result is a pulse width modulation (PWM) or a pulse density modulationof the DC energy of the input, which after filtering results in an AC waveform closely resembling the desired reference signal.

[0034] The output of the power inverter is then coupled to the primary of a transformer, which provides galvanic isolation to the converter and enables both the inverter and the voltage multiplier to work almost independently. For size reduction, the transformers used in the present invention are preferably high-frequency transformers. For safety reasons, the transformers need to be able to sustain high voltages without damaging their internal and external isolations.

[0035] Further, the voltage multiplier is then coupled to the secondary of the transformer. Several different topologies of voltage multipliers exist in the literature. For the applications of the present invention, size and cost are significant constraints therefore topologies involving capacitor and diode arrangements are preferred. FIGs. 11 to 14 show some of these topologies. Stacking multiple voltage multipliers, as shown for example in FIG. 12, makes it possible to achieve high voltages with a few iterations. In the circuit of FIG. 13, for instance, the output voltage Vo is 4 times the input Vi with few as 4 diodes and 4 capacitors. In the example of FIG.14 is shown a transformer in which the secondary has two separate windings with 180° phase shift in order to get full wave rectification. The two windings need to be insulated against the large voltage between them, though.

[0036] One additional advantage of voltage multiplier topologies comprising diodes and capacitors is that the output is often rectified, that is, converted from AC to DC. This avoids having to include one module specifically for this purpose.

[0037] The output of the electronic converter, i.e., the output of the voltage multiplier, is then coupled to the electrodes of the weed inactivation device to provide the necessary power to perform weed inactivation. To ensure that a constantamount of power is provided to the electrodes, thus to the weeds themselves, a control unit may be coupled to both the electrodes and the electronic converter.

[0038] This control unit comprises a PWM module and at least one sensor: the PWM module being coupled to the at least one electronic converter and the at least one sensor being coupled to the electrodes. The purpose of this coupling is to form a closed feedback loop allowing the control unit to monitor the power provided to the electrodes (by measuring voltage, current or both) and adjust the duty cycle of the power inverter’s PWM to ensure that substantially the same amount of power is being provided to the electrodes regardless of the load (such as weed, weed-soil or weed-soil-weed resistances). For example, if the control unit is configured to ensure a given constant power output (within an acceptable margin of error), should the power output be above the upper limit of an acceptable threshold, the control unit should reduce the duty cycles of the PWM; should the power output be below the lower limit of the threshold, the control unit should increase the duty cycles of the PWM.

[0039] Although the output is rectified it is not necessarily stable and constant. Since the capacitors are not ideal components, their charge / discharge cycles produce an unavoidable parasitic voltage peaks in the output. However, for performance and efficiency reasons, these parasitic voltage peaks on the output should be as low as possible and not superior to IkV.

[0040] So, in the state of the art, even when targeting only one plant, AC or high voltage peak waveforms would cause electrical weeding systems to present different efficacies at different plants with different electrical resistances, so being not optimal to the objectives of the present invention. Therefore, the present invention can claim to be the only one to take the most out of the power source by keeping the output power constant throughout a varying load band, delivering the same power regardless of plant and soil resistance, ensuring application qualityuniformity, combining impedance matching of capacitive voltage multipliers to broaden the semi constant power band and keeping the power constant throughout the aforementioned varying load band by controlling the charge present at the capacitors in the voltage multiplier connected to the application electrodes through PWM feedback controls.

[0041] A downside for such a system is that it by itself may work to maintain voltaic arcs that may be created when the electrodes briefly leave the resistive system and travel through the air without proper contact. There are mechanical solutions to minimize this effect, but sensors that sense electrical parameters of the resistive system, the applied voltage, or the creation of sparks themselves can be used to signal to briefly interrupt, for 1ms up to 1000ms, the application and extinguish any sparks before they represent a higher fire hazard. Another solution is to periodically do so. Document WO 2021 / 053086 explains in detail how to deal with this issue.

[0042] There is an alternative electronic architecture that can be used in combination with prior features to further improve upon prior art. A particular embodiment of the IPOS (Input Parallel, Output Series) configuration, which is proven to provide improvements at characteristics in the fields of energy storage in batteries, renewable energy generation, and high-voltage pulse generators, etc., due to its high voltage gain and high efficiency compared to conventional two -stage energy conversion systems (References 1-4); in combination with other features creates a cheaper, easier to construct, modular converter.

[0043] A very simple embodiment of a non-IPOS (Input Parallel, Output Series) electronic architecture with only two multiplier arrays connected using a mid-tap reference of the transformer can be found in FIG. 11. It considers the output of a DC input power source as VDC1 and VDC2, switching inputs to control PWM or similar at SI and S2, higher frequency inputs at the transformer primary as HF Al and HFB1, higher frequency outputs of the transformer secondary as HFA3 and HFB3, two parallel arrays of multipliersusing a common middle capacitor MPY C2, the final output at one electrode is approximately 10 kV, the other electrode can be used actively or as ground and the resistive system is R.

[0044] As such, the solutions of the prior art reached a constant power output curve, but they are not easily adjustable into new needed resistance band levels (which can happen when you take a converter from a wet environment into a dry environment to perform electrical weeding i.e.), and their efficiency levels, although relatively high, have limits due to the nature of a capacitive voltage multiplier with multiple stages, due to losses such as the ones caused by circulating currents in the stray capacitances. Thus, diminishing the stages of those multipliers significantly improves upon, not only insulation needs, but also upon energy efficiency.OBJECTIVES OF THE INVENTION

[0045] It is therefore an objective of the present invention to teach a system and method for powering a plurality of electrodes of an electrical weeding device that provides easy adjustment for the output voltage of the electrodes in view of a plurality of resistance band levels.SUMMARY OF THE INVENTION

[0046] As such, the present invention more particularly relates to a system for powering a plurality of electrodes of an electrical weeding device comprising: a power input; a shared switching arm connected to the power input; a plurality of power cells connected to the shared switching arm, each of the plurality of power cells comprising: an inverter switching arm, wherein the inverter switching arm forms with the shared switching arm a Full Bridge converter; a gate driver connected to the inverter switching arm, wherein the gate driver is configured to drive its inverter switching arm upon receiving an activation signal; and a transformer, wherein each inverter switching arm is connected to the shared switching arm in a parallel configuration and to a primary side of the transformer, and the secondaryside of each transformer is connected in a series configuration to a full-wave rectifier bridge, the full-wave rectifier bridge is connected to a LC filter and the LC filter is further connected to the plurality of electrodes; a control unit configured to determine an output power level of the plurality of power cells based on a weed pressure in a weeding area, and wherein the control unit is further configured to send the activation signal to each gate driver of the plurality of power cells to adjust the phase shift between the inverter switching arms and the shared switching arm, wherein the phase shift defines the output voltage to be applied in the plurality of electrodes by means of the Full Bridge converter.

[0047] In addition to the system above, the present invention also discloses a method for powering a plurality of electrodes of an electrical weeding device comprising the system of the present invention, the method comprising: powering the system by means of an input power; determining a weed pressure in a weeding area; determining, by a control unit, an output power level of a plurality of power cells based on the weed pressure, sending, by the control unit, activation signal to each gate driver of the of the plurality of power cells, driving, by each gate driver of the plurality of power cells, its inverter switching arm; and powering the plurality of electrodes with the voltage from the plurality of power cells.

[0048] Furthermore, the present invention also discloses an electrical weeding device comprising the system for powering a plurality of electrodes of the present invention.

[0049] Lastly, the present invention also relates to a vehicle carrying the electrical weeding device of the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention is explained in greater detail below and makes references to the drawings and figures, attached herewith, when necessary.

[0051] FIG. 1A shows the amplitude and peaks of a generic sinusoidal waveform.

[0052] FIG. IB shows the peak voltage and peak-to-peak voltage of a generic sinusoidal waveforms.

[0053] FIG. 2 shows the behavior of AC electrical parameters with dynamic impedances.

[0054] FIG. 3 shows a typical power curve (y axis in watts - w) and the load (x axis in kilo ohms - kQ).

[0055] FIG. 4 shows a plot of the power curve as seen in the prior-art.

[0056] FIG. 5 shows a power curve with two peaks, where the vertical axis relates to the power and the horizontal axis relates to the electrical resistance.

[0057] FIG. 6 shows a power curve with three peaks where the vertical axis relates to the power and the horizontal axis relates to the electrical resistance.

[0058] FIG. 7 shows a power curve with stable constant power where the vertical axis relates to the power and the horizontal axis relates to the electrical resistance.

[0059] FIG. 8 shows examples of PWM signal with different duty cycles.

[0060] FIG. 9 shows an example of PWM changes to keep constant power upon changes in the load.

[0061] FIG. 10 shows the power relationship for an ideal constant power source.

[0062] FIG. 11 shows an exemplary embodiment of an electronic converter circuit of the prior art.

[0063] FIG. 12 shows a topology for an arrangement of voltage multiplier circuits that may be used in the electronic converter of the prior art.

[0064] FIG. 13 shows an alternative topology of a voltage multiplier circuit that may be used in the electronic converter of the prior art.

[0065] FIG. 14 shows another alternative topology of a voltage multiplier circuit that may be used in the electronic converter of the prior art.

[0066] FIG. 15 shows an IPOS diagram of converter connections with input in parallel and output in series according to an embodiment of the present invention.

[0067] FIG. 16 shows a part of the converter that will be aggregated according to an embodiment of the present invention.

[0068] FIG. 17 shows the aggregated part of the converter according to an embodiment of the present invention.

[0069] FIG. 18 shows the power cells according to an embodiment of the present invention.

[0070] FIG. 19 shows a shared switching arm, the control unit and the power cells according to an embodiment of the present invention.

[0071] FIG. 20 shows a power bus according to an embodiment of the present invention.

[0072] FIG. 21A shows a shared LC filter configuration according to an embodiment of the present invention.

[0073] FIG. 2 IB shows an individual LC filter configuration according to an embodiment of the present invention.

[0074] FIG. 22 shows the converter circuit of one power cell according to an embodiment of the present invention.

[0075] FIG. 23 shows a first exemplary embodiment of an electrical weeding device comprising the system according to an embodiment of the present invention.

[0076] FIG. 24 shows a second exemplary embodiment of an electrical weeding device comprising the system according to an embodiment of the present invention.

[0077] FIG. 25 shows a second exemplary embodiment of an electrical weeding device comprising the system according to an embodiment of the present invention.

[0078] FIG. 26 shows an example of an arrangement with two electrodes of the system according to an embodiment of the present invention.

[0079] FIG. 27 shows an example of an arrangement with two sets of electrodes of the system, each set with two electrodes, according to an embodiment of the present invention.

[0080] FIG. 28 shows an exemplary usage embodiment according to an embodiment of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0081] The present invention more particularly relates to a system for powering a plurality of electrodes 31, 500, 600 of an electrical weeding device 100, 200, 400, comprising: a power input 20; a shared switching arm 23 connected to the power input 20; a plurality of power cells 5 connected to the shared switching arm 23, each of the plurality of power cells 5 comprising: an inverter switching arm 10, wherein the inverter switching arm 10 forms with the shared switching arm 23 a Full Bridge converter; a gate driver 16 connected to the inverter switching arm 10, wherein the gate driver 16 is configured to drive its inverter switching arm 10 upon receiving an activation signal; and a transformer 11, wherein each inverter switching arm 10 is connected to the shared switching arm 23 in a parallel configuration and to a primary side of the transformer 11 , and the secondary side of each transformer 11 is connected in a series configuration to a full -wave rectifier bridge 12, the fullwave rectifier bridge 12 is connected to a LC filter 13 and the LC filter 13 is further connected to the plurality of electrodes 31, 500, 600; a control unit 30 configured to determine an output power level of the plurality of power cells 5 based on a weed pressure in a weeding area, and wherein the control unit 30 is further configured tosend the activation signal to each gate driver 16 of the plurality of power cells 5 to adjust the phase shift between the inverter switching arms 10 and the shared switching arm 23, wherein the phase shift defines the output voltage to be applied in the plurality of electrodes 31, 500, 600 by means of the Full Bridge converter.

[0082] It is easily appreciated by those skilled in the art that, although the present disclosure makes reference to specific technologies and components, several other technologies and components capable of performing the same or equivalent functions may replace those disclosed herein while still being part of the scope of the present invention.

[0083] FIGs. 1-14 were used to explain the prior art in Description of the Related Art section. The present invention will be explained from the FIG. 15 and beyond.

[0084] Preferably, the present invention uses an IPOS (Input Parallel, Output Series) configuration which provides converters with a favorable step-up voltage electronic architecture due to its high voltage gain and high efficiency compared to conventional two-stage energy conversion systems. (References 1-4)

[0085] FIG. 15 presents an IPOS diagram of the connections of converters with input in parallel and output in series, a solution implemented in the invention with the aim of increasing the voltage that will be supplied to the load.

[0086] Moreover, FIG. 15 presents a general IPOS diagram of the connections of converters with input in parallel and output in series, a solution implemented in this invention that aims to increase the voltage that will be supplied to the load.

[0087] FIG. 16 shows a primary side of transformers with the conventional H-bridge marked in doted circle that will be aggregated to be shared among the transformers of the present invention. This preferable configuration comprises a shared power converter stage, such as illustrated in FIG. 17, which determines thesizing power components, since it involves sharing one of the legs of the inverter (H-bridge in this example) in the primary circuit of parallel-input full-bridge converters.

[0088] The generation of the high-voltage signal is carried out by the plurality of power cells 5 in the IPOS (Input Parallel - Output Serial) topology as illustrated in FIGs. 18 and 19. Preferably, the power input 20 of the system is an AC power source. Preferably, the present invention comprises five power cells 5 to generate a DC peak voltage between 0.5-2.5 kV, which in series results in a combined voltage of 2.5-12.5 kV. It is possible to reduce the total power capacity of the system by reducing the number of power cells 5 mounted the shared switching arm 23.

[0089] Converter topologies can vary, as explored in the prior art, but preferably the present invention uses the PSFB (Phase Shift Full Bridge) configuration, where two switching arms are required, and the phase shift between them defines the average output voltage. Each of the power cells 5 is composed of one inverter switching arm 10, while the second arm is a shared switching arm 23 that is shared among all the cells 5. Preferably, the shared switching arm 23 and each inverter switching arm 10 comprise switches Si, S2, S3, S4in a Half bridge configuration, wherein the Full Bridge converter formed between the shared switching arm 23 and each inverter switching arm 10 is a Phase Shift Full Bridge converter.

[0090] In this topology, the sum of all output voltages from the converters over the load is obtained, and the output current is identical across the modules. This indicates that the current of each module is reduced with an increase in the number of modules, allowing the power delivered by the module to be distributed among the power cells 5 located at the output. This implies that the output voltage of each module is reduced with an increase in the number of modules with series output.

[0091] Preferably, the converter of the present invention consists of a shared power converter stage 23, such as the circuit presented in FIG. 17, which determines the sizing power components, since it involves sharing one of the legs of the inverter (Full H-bridge in this example) in the primary circuit of parallel -input full-bridge converters. FIG. 16 shows the primary side of the transformer with the conventional H-bridge with markings on the leg that will be aggregated to be shared among the transformers.

[0092] Preferably, the shared switching arm 23 of the two delayed legs marked by the doted circle in FIG. 16 may be aggregated as illustrated in FIG. 17. With the aggregation of the arms, there is a higher current in this junction of the circuit, requiring the switching elements to have a greater capacity than the nonshared switching elements.

[0093] Due to the series characteristic of the IPOS configuration, the power cells 5 can be replicated multiple times with minimal differences between them. In this particular example, the only difference between one cell 5 and another lies in the reference resistor located within the voltage sensor block 15 of FIG. 18, specific to the individual voltage sample of the cells 5. Due to the high voltage, to measure the voltage output, a resistive voltage divider can be used, as insulation, optocouplers can also be added.

[0094] With this technique, it is possible to reduce control signals, provided that the aggregated components are correctly sized for the sum of all currents from the non-shared circuits. Additionally, this junction allows the power losses of the switching components to be concentrated at a common point for practical dissipation, aiming to simplify the cooling system.

[0095] The power cells 5 are the final elements of the system of the present invention. It is in the power cell 5 that hold the transformers responsible for the previously mentioned IPOS configuration are located. This configuration allows thevoltage to be raised to the levels desired by the system. As shown in FIG. 18, each power cell 5 comprises a transformer 11 ; an individual arm gate driver 16; crossover protection 14 connected to the gate driver 16 configured to protect the switch from overvoltage; the inverter switching arm 10; a full-wave rectifier bridge 12; a LC filter 13; and a voltage sensor 15 configured to measure the output voltage of the power cell 5.

[0096] Preferably, the present invention is a modular electro-electronic converter for electrical weeding comprising of at least one power source, connected to at least one shared power converter stage. The shared power converter stage consists of the shared switching arm 23 and the plurality of power cells 5 as illustrated in FIG. 19. The plurality of power cells 5 comprise at least one transformer 11 (FIG. 18), through a IPOS configuration.

[0097] Preferably, the hardware development should be guided by the insulation between the control part and the power part. Thus, the electronic design can account for four printed circuit boards, which are responsible for the power bus 22, the shared switching arm 23, the power cells 5, and the control unit 30, as presented in FIG. 19. The signals between the boards can be insulated through specific components to protect the control circuit from possible abnormalities that the power stage may generate. FIG. 19 also illustrates a current sensor 24 (preferably a hall sensor) connected between the LC filter 13 and the plurality of electrodes 31, the current sensor 24 configured to measure current reaching the plurality of electrodes 31.

[0098] The shared switching arm 23 in FIG. 19 corresponding to the switches Si and S2 illustrated in FIG. 16 when aggregated as in FIG. 17. Whereas the switches S3 and S4 of FIGs. 16 and 17 represents the inverter switching arm 10 of each power cell 5 (also in FIG. 18). Preferably, the switches (Si, S2, S3and S4) are transistors such as MOSFETs, IGBTs and BJTs.

[0099] Preferably, the electronic converter of the present invention comprises a power bus 22 configured to convert an alternating input voltage into DC voltage to be used by the converter, in cases where the power supply is made by an alternator. This power bus 22 is illustrated in the block diagram of FIG. 20 as a power unit 22 coupled to the power source 20 and to a switch disconnector 21 (configured to disconnect the system if necessary). The power bus 22 comprising a power bus rectifier 34 connected to the switch disconnector 21 and to a pre-charge circuit 33; the pre-charge circuit 33 (configured to pre-charge the capacitors so the inrush current is not too large) connected to a link DC 37; a power bus current sensor 32 (such as a hall sensor) configured to measure the current from the link DC 37; fault protections 35 for the power bus rectifier 34 and for the link DC 37; and link DC protection sensors 36, as the fault protection sensor 35. The Link DC 37 is an association of capacitors to provide the operational supply for the switching elements, i.e., Power Bus. The link DC protection sensors 36 is configured to sense the current and voltage at the link DC 37. Preferably, the voltage level of the link DC 37 is monitored by overvoltage and undervoltage circuits, used to detect faults when the voltage of link DC 37 is out of the operational value.[000100] Preferably, the shared switching arm 23, the pre-charge 33, the current sensor 32, the fault protections 35 and the link DC sensor 36 are further connected to the control unit 30 for controlling and exchanging information on the circuit. Optionally, the control unit 30 is supplied with a 24 VDC power supply 29. Optionally, an ECU 28 (Electronic Control Unit) is connected to the control unit 30. Optionally, an air cooling 26 is connected to the control unit 30, the air cooling 26 configured to cool down the system. Optionally, the system further comprises a NTC temperature sensor 25 connected to the control unit 30 for measuring the system temperature.[000101] Given that each of the transformers in each of the cells 5 requires an individual rectification bridge 12 on the secondary side to convert the voltage back to DC and then reduce the ripple, the use of an output LC filter 13 may be desired. There are two distinct alternatives of output filters 13 of the secondary side illustrated in FIGs. 21 A and 21B for implementing the necessary output filter for the system's functionality were considered, which comprise two suitable options for the system of the present invention. FIG. 21A shows the use of a shared LC filter 13 for all power cells 5, wherein the LC filter 13 is connected in parallel with the plurality of power cells (5), while FIG. 21B depicts the use of an individual output filter 13 for each power cell 5 connected to each full- wave rectifier bridge 12 of the transformer 11 of each power cell 5.[000102] Preferably, the gate driver 16 is configured to drive the inverter switching arm 10 to adjust the phase shift between the inverter switching arms 10 and the shared switching arm 23 according to the weed pressure detected. For example, if the weed pressure detected is low, the system may be configured to set the output power of each power cell 5 to its lower level, so the total output power lever is the lower. The power voltage of each power cell 5 is equipotential. The activation of each gate drive 16 by the control unit 30 is performed by a PWM unit of the control unit 30.[000103] The Control Unit monitors the individual voltages for each cell to control the sum of all voltages and maintain equipotential voltage between them. The estimate of the power delivery is based with the output current and the sum of voltage for all the cells present in the power module and the number of individual arms also define the max power that it could maintain in the range operational load. [000104] Preferably, the weed pressure is detected by a computer vision system 27 connected to the control unit 30. Optionally, the user may set manually the weed pressure in the system of the present invention.[000105] Furthermore, the control to be performed for the power cells 5 may require the individual acquisition of voltage from each of them, thus providing a power control loop with individual voltage measurements from the output cells 5 and a single power loop supplied with the sum of these voltages and the current measurement of the cells 5 that are in series.[000106] Due to the change in the load seen by the converter when altering the region where the electric discharge is applied, it is necessary to analyze the voltage values that will be used at the system output for the power control of the equipment. An example of potential operating conditions is presented in Table 1.Table 1: exemplary parameter behavior of the system.[000107] Considering situations where the ground impedance is high (i.e. above 15 kQ), the system of the present invention will behave by applying a derating factor of 80% to the total supplied power. This strategy allows the reduction of components that will be rated for the power cells 5. As an example, this derating is applied considering the Full-Power operating mode of the equipment for the condition in which the system is supplying 6 kW of power to an impedance of 35 kQ, as shown in Table 2.Table 2: exemplary parameter behavior of the system, considering de-rating.[000108] Subsequently, the derating percentages for the maximum considered power are observed. Opting for derating for high loads, the control will maintain a top ceiling voltage (i.e. 13 kV) at the electrodes 31, thus reducing the system's stresses. This allows for meeting the conditions that the system will actually operate under most of the time, without needing to implement extremely high insulations. Also, this operation allows for the option of using small rated components in the power cells 5, as an LC filter is required at the output of each cell 5, as shown in FIG. 22, where a simplified embodiment of the full converter can be seen.[000109] Therefore, the present invention is a modular electro-electronic converter for electrical weeding connected to at least one Power Source, connected to at least one Shared Power Converter Stage, connected to, at least two power cells 5 composed of at least one Transformer side, through an IPOS configuration.[000110] The present invention also related to a method for powering a plurality of electrodes 31, 500, 600 of an electrical weeding device 100, 200, 400 comprising the system of the present invention, the method comprising: powering the system by means of an input power 20; determining a weed pressure in a weeding area; determining, by a control unit 30, an output power level of a plurality of powercells 5 based on the weed pressure, sending, by the control unit 30, activation signal to each gate driver 16 of the of the plurality of power cells 5, driving, by each gate driver 16 of the plurality of power cells 5, its inverter switching arm 10; and powering the plurality of electrodes 31, 500, 600 with the voltage from the plurality of power cells 5.[000111] Preferably, the shared switching arm 23 and each inverter switching arm 10 comprise switches SI, S2, S3, S4 in a Half Bridge configuration, wherein the shared switching arm 23 forms with each inverter switching arm 10 a Phase Shift Full Bridge converter, wherein the switches S S2, S3, S4are one transistor selected from the list of MOSFETs, IGBTs and BJTs; and sending activation signal further comprises sending PWM signal to each gate driver (16) of the plurality of power cells (5) to adjust the phase shift between the inverter switching arms (10) and the shared switching arm (23).[000112] Preferably, each of the plurality of power cells 5 further comprises a crossover protection 14; a voltage sensor 15; a full-wave rectifier bridge 12; and a LC filter 13; wherein the method further comprises: protecting, by the crossover protection 14, the gate driver 16; measuring, by the voltage sensor 15, the output voltage of each power cell 5, wherein the voltage sensor 15 is a resistive voltage divider with optocouplers; rectifying, by the full-wave rectifier bridge 12, a transformer secondary signal; and filtering, by the LC filter 13, the rectified transformer secondary signal.[000113] Preferably, the method of the present invention further comprises measuring, by a current sensor 24, a current reaching the plurality of electrodes 31, 500, 600, wherein the current sensor 24 is a hall sensor.[000114] Preferably, the method of the present invention further comprising: converting, by a power bus 22, the AC input voltage into DC voltage; wherein converting further comprises: rectifying, by a power bus rectifier 34, the AC inputpower 20 and delivering DC power to a link DC 37; measuring, by a power bus current sensor 32, a current from the link DC 37, wherein the current sensor 32 is a hall sensor; protecting, by fault protections 35, for the power bus rectifier 34 and for the link DC 37; and sensing , by link DC sensors 36, current and voltage at the link DC 37.[000115] Preferably, determining a weed pressure in a weeding area further comprising determining the weed pressure by means of a computer vision system 27.[000116] The present invention also related to an electrical weeding device 100, 200, 400, comprising the system for powering a plurality of electrodes (31 , 500, 600) of the present invention.[000117] The present invention also related to a vehicle (120) carrying the electrical weeding device (100) of the present invention.[000118] FIGs. 23-25 show exemplary embodiments of three different electrical weeding devices 100, 200, 400 comprising the system according to the present invention.[000119] Particularly, FIG. 23 shows a vehicle carriable electrical weeding device 100 being carried out by a vehicle 120 (for example a truck or a car) comprising a horizontal beam 104 attached thereto supporting a plurality of mount structures 108 each coupled to a plurality of electrodes 31. In addition, the vehicle 100 comprises a housing 106 which holds a power source, the electronic converter and a control unit of the present invention.[000120] FIG. 24 shows a portable handheld electrical weeding device 200 comprising the system of the present invention. This handheld device comprises two handles 202 coupled to a housing of the control unit 204. The control unit 204 is coupled to a main shaft 206 which extends both upstream and downstream of the control unit 204. Upstream of the control unit is a power source 208 coupled to anend of the main shaft 206. Downstream of the control unit 206 is the system of the present invention is present in the housing 212 coupled to the other end of the main shaft 204. Coupled to the electronic converter is the plurality of electrodes 31 which will deliver the current to kill the plant 300. A usual path of the current is shown by the arrow connecting the electrodes 31.[000121] FIG. 25 shows yet another portable hand-pushed electrical weeding device 400 comprising the system of the present invention. This device 400 comprises a panel 402 attached to two handles 404. The handles 404 extend downwardly to connect to a housing 406, the housing 406 comprising a power source, a control unit and the electronic converter of the system of the present invention within said housing 406.[000122] As for the electrodes 500 used in the system of the present invention, FIG. 26 shows frontal, lateral and top example views of electrodes 500 used in the present invention. The electrodes are coupled to a support structure 502 that mechanically connects the electrodes 500 to a device such as the device 100 shown in Figure 23. In this embodiment of the invention, the electrodes 31 are presented as electrodes 500.[000123] FIG. 27 shows another example of electrodes for the system of the present invention. The plurality of electrodes 600 comprise first and second electrodes 600a, 600b. In this embodiment of the invention, the electrodes 31 are presented as electrodes 600.[000124] FIG. 28 shows a detailed embodiment of a vehicle 120 using the invention. Weed pressure is determined by visually estimating the total volume or area of all weed species in a weeding area. This visual estimation can be man made through a skilled professional by just going to the application field and estimating the weed pressure, or through a dynamic vision sensor that dynamically sees and estimates how many weeds, the coverage of the soil by weeds, or other key variablerelated to the weed pressure. Preferably, the weed pressure is determined by analyzing the weeding area with a computer vision system that sets output power level of the plurality of power cells 5 automatically based on that weed pressure determined. Optionally, the weed pressure is manually determined by the user analyzing the weeding area and setting output power level of the plurality of power cells 5.[000125] FIG. 28 shows a truck 120 carrying the system of the present invention and running through a weeding area. The computer vision system is displaced in the font of the truck and determine in real time the weed pressure of the weeding area and adjust the output power level of the plurality of power cells 5 automatically based on that weed pressure determined, consequently triggering more or less voltage in the electrodes 31 for weeding accordingly to the output power level of the plurality of power cells 5.[000126] Therefore, the system and method for powering a plurality of electrodes 31 of an electrical weeding device 100, 200, 400 of the present invention is advantageous by providing modular electro-electronic converter that powers the plurality of electrodes 31 with the approximate amount of voltage as necessary for that specific weeding area, thus saving energy. Moreover, the shared switching arm 23 possibilities the modularity of this invention with a less complex circuit, saving costs and space by requiring less electronic components.[000127] Numerous variations affecting the scope of protection of this invention are permitted. This reinforces the fact that the present invention is not limited to the particular realizations / embodiments described above.LIST OF REFERENCES[000128] Reference 1: S. Lee, Y. -C.-C. (2019). “Voltage Balancing Control of IPOS Modular Dual Active Bridge DC / DC Converters Based on HierarchicalSliding Mode Control” (Vol. 7). in IEEE Access, doi: 10.1109 / ACCESS.2018.2889345[000129] Reference 2: Li, S. S. (March 2020). “High-gain high-efficiency IPOS LLC converter with coupled transformer and current sharing capability” (Vol. 5). in CPSS Transactions on Power Electronics and Applications. doi:10.24295 / CPSSTPEA.2020.00006[000130] Reference 3: Chen, Y., Kang, Y., Nie, S., & Pei, X. (2011). “The Multiple-Output DC-DC Converter With Shared ZCS Lagging Leg”. 26, pp. 2278- 2294. doi: 10.1109 / TPEL.2010.2096543[000131] Reference 4: Chen, W., Ruan, X., Yan, H., & Tse, C. K. (2009). “DC / DC Conversion Systems Consisting of Multiple Converter Modules: Stability, Control, and Experimental Verifications” (Vol. 24). IEEE Transactions on Power Electronics, doi: 10.1109 / TPEL.2009.2012406

Claims

CLAIMS1. A system for powering a plurality of electrodes (31, 500, 600) of an electrical weeding device (100, 200, 400), comprising: a power input (20); a shared switching arm (23) connected to the power input (20); a plurality of power cells (5) connected to the shared switching arm (23), each of the plurality of power cells (5) comprising: an inverter switching arm (10), wherein the inverter switching arm (10) forms with the shared switching arm (23) a Full Bridge converter; a gate driver (16) connected to the inverter switching arm (10), wherein the gate driver (16) is configured to drive its inverter switching arm (10) upon receiving an activation signal; and a transformer (11), wherein each inverter switching arm (10) is connected to the shared switching arm (23) in a parallel configuration and to a primary side of the transformer (11), and the secondary side of each transformer (11) is connected in a series configuration to a full-wave rectifier bridge (12), the full-wave rectifier bridge (12) is connected to a LC filter (13) and the LC filter (13) is further connected to the plurality of electrodes (31, 500, 600); a control unit (30) configured to determine an output power level of the plurality of power cells (5) based on a weed pressure in a weeding area, and wherein the control unit (30) is further configured to send the activation signal to each gate driver (16) of the plurality of power cells (5) to adjust the phase shift between the inverter switching arms (10) and the shared switching arm (23), wherein the phase shift defines the output voltage to be applied in the plurality of electrodes (31, 500, 600) by means of the Full Bridge converter.

2. The system according to claim 1, wherein the power input (20) is an AC power source, and the power provided to the plurality of electrodes (31, 500, 600) is DC power, wherein each power cell (5) provides a DC peak voltage between 0.5-2.5 kV.

3. The system according to claim 1 or 2, wherein the shared switching arm (23) and each inverter switching arm (10) comprise switches (Si, S2, S3, S4) in a Half Bridge configuration, wherein the Full Bridge converter formed between the shared switching arm (23) and each inverter switching arm (10) is a Phase Shift Full Bridge converter.

4. The system according to claim 3, wherein the switches (Si, S2, S3, S4) are one transistor selected from the list of MOSFETs, IGBTs and BJTs.

5. The system according to any one of claims 1 to 4, wherein activation signal is PWM signal.

6. The system according to any one of claims 1 to 5, wherein each of the plurality of power cells (5) further comprises a crossover protection (14) connected to the gate driver (16); and a voltage sensor (15) configured to measure the output voltage of the power cell (5); wherein each power cell (5) of the plurality of power cells (5) has an individual LC filter (13) connected to each full-wave rectifier bridge (12); wherein the voltage sensor (15) is a resistive voltage divider with optocouplers.

7. The system according to any one of claims 1 to 5, wherein each of the plurality of power cells (5) further comprises a crossover protection (14) connected to the gate driver (16); a voltage sensor (15) configured to measure the output voltage of the power cell (5); a full-wave rectifier bridge (12) connected to the secondary side of the transformer (11), wherein the voltage sensor (15) is a resistive voltage divider with optocouplers;wherein the plurality of power cells (5) shares a same LC filter (13) connected in parallel with the plurality of power cells (5).

8. The system according to claim 6 or 7, further comprising a current sensor (24) connected between the LC filter (13) and the plurality of electrodes (31, 500, 600), the current sensor (24) configured to measure current reaching the plurality of electrodes (31 , 500, 600), wherein the current sensor (24) is a hall sensor.

9. The system according to any one of claims 1 to 8, further comprising a switch disconnector (21) configured to disconnect the system if necessary, the switch disconnector (21) connected to the power input (20) and a power bus (22) configured to convert the AC input voltage into DC voltage, the power bus (22) further connected to the shared switching arm (23); wherein the power bus (22) comprises: a power bus rectifier (34) connected to the switch disconnector (21) and to a pre-charge circuit (33) configured to pre-charge capacitors so the inrush current is not too large, the pre-charge circuit (33) connected to a link DC (37), a power bus current sensor (32) configured to measure the current from the link DC (37), wherein the current sensor (32) is a hall sensor; fault protections (35) for the power bus rectifier (34) and for the link DC (37); and link DC protection sensors (36) configured to sense the current and voltage at the link DC (37).

10. The system according to claim 9, wherein the shared switching arm (23), the pre-charge (33), the current sensor (32), the fault protections (35) and the link DC sensor (36) are further connected to the control unit (30).

11. The system according to any one of claims 1 to 10, further comprising an Electronic Control Unit (28) connected to the control unit (30); a 24VDC power supply (29) configured to feed the control unit (30); a temperature sensor (25) and an air colling (26) configured to cool down the system.

12. The system according to any one of claims 1 to 11, further comprising: a computer vision system (27) configured to determine the weed pressure.

13. The system according to any one of claims 1 to 12, further comprising: an Electronic Control Unit, ECU, (28) connected to the control unit (30); an air cooling (26) connected to the control unit (26), the air cooling 26 configured to cool down the system; and / or a NTC temperature sensor (25) connected to the control unit (30) for measuring the system temperature, wherein the control unit (30) is supplied with a 24 VDC power supply (29).

14. A method for powering a plurality of electrodes (31, 500, 600) of an electrical weeding device (100, 200, 400) comprising the system as defined in any one of claims 1 to 13, the method comprising: powering the system by means of an input power (20); determining a weed pressure in a weeding area; determining, by a control unit (30), an output power level of a plurality of power cells (5) based on the weed pressure, sending, by the control unit (30), activation signal to each gate driver (16) of the of the plurality of power cells (5), driving, by each gate driver (16) of the plurality of power cells (5), its inverter switching arm (10); andpowering the plurality of electrodes (31, 500, 600) with the voltage from the plurality of power cells (5).

15. The method according to claim 14, wherein the shared switching arm (23) and each inverter switching arm (10) comprise switches (Si, S2, S3, S4) in a Half Bridge configuration, wherein the shared switching arm (23) forms with each inverter switching arm (10) a Phase Shift Full Bridge converter, wherein the switches (Si, S2, S3, S4) are one transistor selected from the list of MOSFETs, IGBTs and BJTs; and sending activation signal further comprises sending PWM signal to each gate driver (16) of the plurality of power cells (5) to adjust the phase shift between the inverter switching arms (10) and the shared switching arm (23).

16. The method according to claim 14 or 15, wherein each of the plurality of power cells (5) further comprises a crossover protection (14); a voltage sensor (15); a full-wave rectifier bridge (12); and a LC filter (13); wherein the method further comprises: protecting, by the crossover protection (14), the gate driver (16); measuring, by the voltage sensor (15), the output voltage of each power cell (5), wherein the voltage sensor (15) is a resistive voltage divider with optocouplers; rectifying, by the full-wave rectifier bridge (12), a transformer secondary signal; and filtering, by the LC filter (13), the rectified transformer secondary signal.

17. The method according to any one of claims 14 to 16, further comprising measuring, by a current sensor (24), a current reaching the plurality of electrodes (31, 500, 600), wherein the current sensor (24) is a hall sensor.

18. The method according to any one of claims 14 to 17, further comprising: converting, by a power bus (22), the AC input voltage into DC voltage; wherein converting further comprises: rectifying, by a power bus rectifier (34), the AC input power (20) and delivering DC power to a link DC (37); measuring, by a power bus current sensor (32), a current from the link DC (37), wherein the current sensor (32) is a hall sensor; protecting, by fault protections (35), for the power bus rectifier (34) and for the link DC (37); and sensing, by link DC sensors (36), current and voltage at the link DC (37).

19. The method according to any one of claims 14 to 18, wherein determining a weed pressure in a weeding area further comprising determining the weed pressure by means of a computer vision system (27).

20. An electrical weeding device (100, 200, 400), comprising the system for powering a plurality of electrodes (31, 500, 600) as defined in any one of claims 1 to 13.

21. The electrical weeding device (100, 200, 400) according to claim 20, wherein the plurality of electrodes (31 , 500, 600) is coupled to a support structure (502) that mechanically connects the electrodes plurality of electrodes (31 , 500, 600) to the electrical weeding device (100, 200, 400); preferably wherein the plurality of electrodes (600) comprises a first and second electrodes (600a, 600b).

22. The electrical weeding device (100) according to claim 20 or 21, wherein the electrical weeding device (100) is a vehicle carriable electrical weeding device (100) comprising a horizontal beam (104) attached thereto for supporting aplurality of mount structures (108), each one of the plurality of mount structures (108) coupled to the plurality of electrodes (31, 500, 600); and a housing (106) which holds the system for powering the plurality of electrodes.

23. The electrical weeding device (200) according claim 20 or 21, wherein the electrical weeding device (200) is a portable handheld electrical weeding device (200) comprising: two handles (202) coupled to a housing of a control unit (204), the control unit 204 being coupled to a main shaft (206) extending both upstream and downstream from the control unit (204); a power source (208) coupled to an end of the main shaft (206); a housing (212) coupled to the other end of the main shaft 204, the housing (212) configured to hold the system for powering the plurality of electrodes; and the plurality of electrodes (31) coupled to the system (208).

24. The electrical weeding device (400) according to claim 20 or 21, wherein the electrical weeding device (400) is a hand-pushed electrical weeding device (400) comprising comprises a panel (402) attached to two handles (404), wherein the handles (404) extend downwardly to connect to a housing (406) comprising the system for powering the plurality of electrodes.

25. A vehicle (120) carrying the electrical weeding device (100) as defined in claim 22.

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