Field of the disclosure

The disclosure relates to a system for an electrochemical process such as e.g. electrolysis or electrodialysis. Furthermore, the disclosure relates to a method for supplying electric power to an electrochemical process.

Background

An electrochemical process where electric power is supplied to process fluid can be for example an electrolysis process or an electrodialysis process. The electrolysis can be e.g. water electrolysis for decomposing water into hydrogen gas H2 and oxygen gas O2. A widely used type of water electrolysis is alkaline water electrolysis where electrodes operate in alkaline liquid electrolyte that may comprise e.g. aqueous potassium hydroxide “KOH” or aqueous sodium hydroxide “NaOH”. The electrodes are separated by a porous diaphragm that is non-conductive to electrons, thus avoiding electrical shorts between the electrodes. The porous diaphragm further avoids a mixing of produced hydrogen gas H2 and oxygen gas O2. The ionic conductivity needed for electrolysis is caused by hydroxide ions OH- which are able to penetrate the porous diaphragm. The electrodialysis is typically used to desalinate saline solutions but other applications such as treatment of industrial effluents, demineralization of whey, and deacidification of fruit juices are becoming increasingly important. The electrodialysis is carried out in an electrodialysis stack that is between electrodes and comprises an alternating series of anion-selective membranes and cation-selective membranes. Areas between successive ones of the anion- and cation-selective membranes constitute dilute compartments and concentrate compartments. Electric field moves cations through the cation-selective membranes and anions through the anion-selective membranes. The net result is that ion concentration in the dilute compartments is reduced, and the adjacent concentrate compartments are enriched with ions.

An electrochemical process of the kind described above requires a direct current “DC” supply. Thus, conversion from alternating current “AC” to direct current “DC”, i.e. rectification, is needed in a system connected to an alternating voltage network. Power electronics plays a key role in implementation of a controllable direct current supply. The rectification can be done with a passive rectifier, and the direct voltage level at an electrochemical reactor, e.g. an electrolyzer, can be adjusted with a direct voltage “DC-DC” converter between the passive rectifier and the electrochemical reactor. A typical passive rectifier is a 6-pulse diode rectifier. In industrial electrolysis and electrodialysis systems, rectifiers based on thyristors are a common choice. A direct voltage converter between a rectifier and an electrochemical reactor is not needed when the rectifier is a thyristor rectifier. The wide use of thyristor rectifiers in industrial systems is accomplished by the high efficiency, high reliability, and high current-handling capability of thyristors. Typical thyristor rectifiers in industrial use are typically 6- and 12-pulse rectifiers.

The above-mentioned diode and thyristor rectifiers produce considerable distortion to grid currents drawn by a system for an electrochemical process. Furthermore, a thyristor rectifier produces a high level of voltage fluctuation to an electrochemical reactor, which can be non-ideal for the operation of the electrochemical reactor.

Summary

The following presents a simplified summary to provide a basic understanding of some aspects of various embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts in a simplified form as a prelude to a more detailed description of exemplifying and non-limiting embodiments.

In accordance with the invention, there is provided a new system for an electrochemical process that can be for example an electrolysis process or an electrodialysis process. A system according to the invention comprises: an electrochemical reactor configured to carry out the electrochemical process in response to supplying direct current to electrodes of the electrochemical reactor, - a rectifier comprising an alternating voltage terminal for receiving alternating voltages, a direct voltage terminal for supplying the direct current to the electrodes of the electrochemical reactor, and a diode bridge between the alternating voltage terminal and the direct voltage terminal so that the diode bridge is configured to receive the alternating voltages, and

- a transformer connected to the alternating voltage terminal and configured to transfer electric power from an alternating voltage network to the rectifier,

The rectifier comprises switching circuitries configured to constitute bi-directional controllable switches which are: i) able to conduct and block electric current in both directions, ii) connected to the alternating voltage terminal, and iii) connected to each other to form a star- or a delta-connection. The switching circuitries are controllable to achieve sufficiently sinusoidal alternating input currents of the rectifier so that the alternating input currents of the rectifier are sufficiently in the same phase with respect to alternating input voltages of the rectifier. Therefore, losses and other negative effects caused by current distortion and fundamental wave reactive power can be avoided or at least reduced. In an exemplifying and non-limiting embodiment, the transformer comprises a tap-changer for changing the transformation ratio of the transformer to control the direct voltage supplied to the electrochemical reactor.

In accordance with the invention, there is provided also a new method for supplying electric power to an electrochemical process. A method according to the invention comprises:

- supplying alternating voltages via a transformer to a rectifier, and

- supplying direct current from the rectifier to an electrochemical reactor to carry out the electrochemical process.

The rectifier comprises an alternating voltage terminal which receives the alternating voltages, a direct voltage terminal which supplies the direct current to electrodes of the electrochemical reactor, and a diode bridge between the alternating voltage terminal and the direct voltage terminal so that the diode bridge is configured to receive the alternating voltages. Furthermore, the rectifier comprises switching circuitries that act as bi-directional controllable switches which are: i) capable of conducting and blocking electric current in both directions, ii) connected to the alternating voltage terminal, and iii) connected to each other to form a star- or a delta-connection.

Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and nonlimiting embodiments when read in conjunction with the accompanying drawings.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features.

The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

Brief description of the figures

Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: figure 1 a illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process, figures 1 b, 1 c, 1d, 1 e, and 1f illustrate details of systems according to exemplifying and non-limiting embodiments for an electrochemical process, figure 2 illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process, figure 3 illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process, and figure 4 shows a flowchart of a method according to an exemplifying and non-limiting embodiment for supplying electric power to an electrochemical process.

Description of the exemplifying embodiments

The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

Figure 1 a illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process. The system comprises an electrochemical reactor 101 for containing liquid and comprising electrodes for directing electric current to the liquid. In figure 1 a, two of the electrodes are denoted with references 102 and 103. In the exemplifying system illustrated in figure 1 a, the electrochemical reactor 101 comprises a stack of electrolysis cells. The electrolysis cells may contain for example alkaline liquid electrolyte for alkaline water electrolysis. In this exemplifying case, the liquid electrolyte may comprise for example aqueous potassium hydroxide “KOH” or aqueous sodium hydroxide “NaOH”. It is however also possible that the electrolysis cells contain some other electrolyte. In figure 1 a, four of the electrolysis cells are denoted with references 120, 121 , 122, and 123. Each of the electrolytic cells comprises an anode, a cathode, and a porous diaphragm dividing the electrolysis cell into a cathode compartment containing the cathode and an anode compartment containing the anode. The system may comprise e.g. tens or even hundreds of electrolysis cells. It is however also possible that a system according to an exemplifying and non-limiting embodiment comprises from one to ten electrolysis cells. In the exemplifying system illustrated in figure 1 a, the electrolysis cells are electrically series connected. It is however also possible that electrolytic cells of a system according to an exemplifying and non-limiting embodiment are electrically parallel connected, or the electrolytic cells are arranged to constitute series connected groups of parallel connected electrolytic cells, or parallel connected groups of series connected electrolytic cells, or the electrolytic cells are electrically connected to each other in some other way. The system comprises a hydrogen separator tank 125 and a first piping 124 from the cathode compartments of the electrolysis cells to an upper portion of the hydrogen separator tank 125. The system comprises an oxygen separator tank 126 and a second piping 136 from the anode compartments of the electrolysis cells to an upper portion of the oxygen separator tank 126. The system comprises a third piping 127 for circulating the liquid electrolyte from a lower portion of the hydrogen separator tank 125 and from a lower portion of the oxygen separator tank 126 back to the electrolysis cells. In the hydrogen and oxygen separator tanks 125 and 126, hydrogen and oxygen gases H2 and O2 are separated as gases continue to rise upwards and the liquid electrolyte returns to the electrolyte cycle. In the exemplifying system illustrated in figure 1 a, the third piping 127 comprises a controllable pump 129 for pumping the liquid electrolyte to the electrolysis cells. A pump-controlled electrolyte cycle is advantageous especially when temperature control is needed. It is however also possible that a system according to an exemplifying and non-limiting embodiment comprises a gravitational electrolyte circulation. In the exemplifying system illustrated in figure 1a, the third piping 127 further comprises a filter 128 for filtering the liquid electrolyte. The filter 128 can be for example a membrane filter for removing impurities from the liquid electrolyte.

The system comprises a rectifier 104 that comprises an alternating voltage terminal 106 for receiving alternating “AC” voltages and a direct voltage terminal 107 for supplying direct “DC” current to the electrodes of the electrochemical reactor 101 . The rectifier 104 comprises a diode bridge 105 between the alternating voltage terminal 106 and the direct voltage terminal 107. In this exemplifying case, the alternating voltage terminal 106 is constituted by alternating voltage poles of the diode bridge 105 and the direct voltage terminal 107 is constituted by positive and negative direct voltage poles of the diode bridge 105. The system comprises a transformer 108 connected to the alternating voltage terminal 106 and configured to transfer electric power from an alternating voltage network 131 to the rectifier 104. The rectifier 104 comprises switching circuitries configured to constitute bidirectional controllable switches 109, 110, and 111 each of which is capable of conducting and blocking electric current in both directions. In this exemplifying case, the bi-directional controllable switches 109-111 are connected to each other to form a star-connection which is in turn connected to the alternating voltage terminal 106. In this exemplifying case, the rectifier 104 comprises a capacitive circuit 112 that is connected to the direct voltage terminal 107. The capacitive circuit 112 comprises a first capacitor 113 connected between the positive direct voltage pole of the diode bridge 105 and a star-point 115 of the star-connection of the bi-directional controllable switches 109-111 , and a second capacitor 114 connected between the negative direct voltage pole of the diode bridge 105 and the star-point 115.

Exemplifying implementations of switching circuitries configured to constitute the above-mentioned bi-directional controllable switches 109-111 are presented in figures 1 b, 1 c, 1d, 1 e, and 1f. The switching circuit 154 shown in figure 1f is a modification of the switching circuit 153 shown in figure 1 e. It is straightforward to see that the switching circuits 153 and 154 operate in the same way when an electric potential at the point between the capacitors is between electric potentials of the positive and negative direct voltage poles of the rectifier. Furthermore, it is straightforward to understand that the switching circuits shown in figure 1 f, and thus also the switching circuits shown in figure 1e, constitute bi-directional controllable switches which are: i) able to conduct and block electric current in both directions, ii) connected to the alternating voltage terminal of the diode bridge, and iii) connected to each other to form a star-connection. The switching circuitries shown in figure 1 e limit the range of an electric potential of the star-point, i.e. the point between the capacitors, so that the switching circuitries shown in figure 1 e allow electric current from the star-point to the positive direct voltage pole of the diode bridge in response to a situation in which the electric potential of the star-point exceeds the electric potential of the positive direct voltage pole of the diode bridge and, correspondingly, allow electric current from the negative direct voltage pole of the diode bridge to the star-point in response to a situation in which the electric potential of the negative direct voltage pole of the diode bridge exceeds the electric potential of the star-point.

The exemplifying switching circuitries 150, 151 , 152, 153, and 154 illustrated in figures 1 b-1f are implemented with insulated gate bipolar transistors “IGBT”. It is however also possible that a switching circuitry comprises e.g. a gate turn-off thyristor “GTO”, or a metal oxide field effect transistor “MOSFET”, or some other suitable semiconductor switch in lieu of each IGBT.

The system comprises a controller 140 for controlling the operation of the bidirectional controllable switches 109-111 so that the alternating input currents of the rectifier 104 are sufficiently sinusoidal, have the same frequency as the alternating voltages at the alternating voltage terminal 106, and are sufficiently in the same phase with respect to the alternating voltages at the alternating voltage terminal 106. In other words, the bi-directional controllable switches 109-111 are controlled so that power factor correction is carried out concerning both a distortion power factor and a fundamental wave power factor. Therefore, losses and other negative effects caused by current distortion and fundamental wave reactive power can be avoided or at least reduced. Furthermore, the bi-directional controllable switches 109-111 are controlled so that the direct voltage of the direct voltage terminal 107 is balanced between the first and second capacitors 113 and 114. The rectifier 104 can be deemed to be a Vienna rectifier whose functionality and control is explained in more detail e.g. in publication EP0660498A2.

In the exemplifying system illustrated in figure 1 a, the transformer 108 comprises a tap-changer 116 for changing the transformation ratio of the transformer 108. The tap-changer 116 can be e.g. an on-load tap-changer that allows to change the transformation ration during loading. The tap-changer 116 can be used for controlling the level of the direct voltage supplied to the electrochemical reactor 101 . Furthermore, the exemplifying system illustrated in figure 1 a comprises a grid filter 117 between the transformer 108 and the alternating voltage terminal 106 of the rectifier 104. In this exemplifying case, the grid filter 117 comprises an inductorcapacitor “LC” filter 119 and serial inductors 118 so that the inductor-capacitor filter and the serial inductors constitute an inductor-capacitor-inductor “LCL” filter. It is however also possible that the grid filter comprises serial inductors only, or there is no grid filter in cases where the stray inductances of the transformer 108 are sufficient for enabling proper power factor correction by the bi-directional controllable switches 109-111 . The system may further comprise a current sensor for measuring the direct current supplied to the electrochemical reactor 101 and/or a voltage sensor for measuring the direct voltage of the direct voltage terminal 107. Furthermore, the system may comprise voltage sensors for measuring the direct voltages of the first and second capacitors 113 and 114 to enable balancing of the direct voltage of the direct voltage terminal 107 between the first and second capacitors 113 and 114. The above- mentioned current sensor and the one or more voltage sensors are not shown in figure 1 a. The current sensor and/or the one or more voltage sensors can be for example parts of the rectifier 104. For another example, the current sensor and/or the voltage sensor for measuring the direct voltage of the direct voltage terminal 107 can be parts of the electrochemical reactor 101. An output signal of the current sensor and/or one or more output signals of the one or more voltage sensors can be delivered to the controller 140 that controls the bi-directional controllable switches 109-111. Furthermore, the output signal of the voltage sensor for measuring the direct voltage of the direct voltage terminal 107 can be delivered to a controller that controls the tap-changer 116. The controller of the tap-changer 116 is not shown in figure 1 a.

Figure 2 illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process. The system comprises an electrochemical reactor 201 for containing liquid and comprising electrodes 202 and 203 for directing electric current to the liquid. In the exemplifying system illustrated in figure 2, the electrochemical reactor 201 comprises an electrodialysis stack that is between the electrodes 202 and 203 and comprises an alternating series of anionselective membranes and cation-selective membranes. In figure 2, one of the anionselective membranes is denoted with a reference 233 and one of the cationselective membranes is denoted with a reference 234. Areas between successive ones of the anion- and cation-selective membranes constitute dilute compartments 239 and concentrate compartments 238. Electric field moves cations through the cation-selective membranes and the anions through the anion-selective membranes. The net result is that ion concentration in the dilute compartments 239 is reduced, and the adjacent concentrate compartments 238 are enriched with the ions. In the exemplifying system illustrated in figure 2, the feed to be processed, e.g. saline feed, is received via an inlet 235, and the diluted liquid such as e.g. fresh water is removed via a first outlet 236, and the concentrate such as e.g. concentrated brine is removed via a second outlet 237.

The system comprises a rectifier 204 that comprises an alternating voltage terminal 206 for receiving alternating “AC” voltages and a direct voltage terminal 207 for supplying direct “DC” current to the electrodes of the electrochemical reactor 201 . The rectifier 204 comprises a diode bridge 205 between the alternating voltage terminal 206 and the direct voltage terminal 207. In this exemplifying case, the alternating voltage terminal 206 is constituted by alternating voltage poles of the diode bridge 205 and the direct voltage terminal 207 is constituted by positive and negative direct voltage poles of the diode bridge 205. The system comprises a transformer 208 configured to transfer electric power from an alternating voltage network 231 to the rectifier 204. In a system according to an exemplifying and nonlimiting embodiment, the transformer 213 comprises a tap-changer 214, e.g. an onload tap-changer, for changing the transformation ratio of the transformer.

The rectifier 204 comprises switching circuitries configured to constitute bidirectional controllable switches 209, 210, and 211 each of which is capable of conducting and blocking electric current in both directions. In this exemplifying case, the bi-directional controllable switches 209-211 are connected to each other to form a delta-connection which is in turn connected to the alternating voltage terminal 206 of the rectifier 204. The system comprises a controller 240 for controlling the operation of the bi-directional controllable switches 209-211 so that the alternating “AC” input currents of the rectifier 204 are sufficiently sinusoidal, have the same frequency as the alternating voltages at the alternating voltage terminal 206, and are sufficiently in the same phase with respect to the alternating voltages at the alternating voltage terminal 206. In other words, the bi-directional controllable switches 209-211 are controlled so that power factor correction is carried out concerning both distortion power factor and fundamental wave power factor. Furthermore, the rectifier 204 comprises a capacitive circuit 212 connected to the direct voltage terminal 207. The exemplifying system illustrated in figure 2 comprises a grid filter 217 connected between the transformer 208 and the alternating voltage terminal 206 of the rectifier 204. In this exemplifying case, the grid filter 217 comprises serial inductors only.

Figure 3 illustrates a system according to an exemplifying and non-limiting embodiment for an electrochemical process. The system comprises first and second electrochemical reactors 301 a and 301 b each of which can be for example such as the electrochemical reactor 101 shown in figure 1 a or such as the electrochemical reactor 201 shown in figure 2. The system comprises a rectifier 304 that comprises an alternating voltage terminal 306 for receiving alternating “AC” voltages, a first direct voltage terminal 307a for supplying direct “DC” current to the first electrochemical reactor 301a, and a second direct voltage terminal 307b for supplying direct “DC” current to the second electrochemical reactor 301 b. The rectifier 304 comprises a diode bridge 305 and switching circuitries configured to constitute bi-directional controllable switches 309, 310, and 311 each of which is capable of conducting and blocking electric current in both directions. In this exemplifying case, the bi-directional controllable switches 309-311 are connected to each other to form a star-connection which is in turn connected to the alternating voltage terminal 306.

In the exemplifying system illustrated in figure 3, the alternating voltage terminal 306 is constituted by alternating voltage poles of the diode bridge 305. The first direct voltage terminal 307a is constituted by a positive direct voltage pole of the diode bridge 305 and a star-point 315 of the star-connection of the bi-directional controllable switches 309-311. The second direct voltage terminal 307b is constituted by the star-point 315 and a negative direct voltage pole of the diode bridge 305. In this exemplifying case, the rectifier 304 comprises a capacitive circuit 312 that comprises a first capacitor 313 connected between the positive direct voltage pole of the diode bridge 305 and the star-point 315, and a second capacitor 314 connected between the negative direct voltage pole of the diode bridge 305 and the star-point 315. The system comprises a transformer 308 configured to transfer electric power from an alternating voltage network to the rectifier 304. In a system according to an exemplifying and non-limiting embodiment, the transformer 308 comprises a tap-changer 316, e.g. an on-load tap-changer, for changing the transformation ratio of the transformer 308.

The system comprises a controller 340 for controlling the operation the bi-directional controllable switches 309-311 so that the alternating input currents of the rectifier 304 are sufficiently sinusoidal, have the same frequency as the alternating voltages at the alternating voltage terminal 306, and are sufficiently in the same phase with respect to the alternating voltages at the alternating voltage terminal 306. In other words, the bi-directional controllable switches 309-311 are controlled so that power factor correction is carried out concerning both a distortion power factor and a fundamental wave power factor. Furthermore, the bi-directional controllable switches 309-311 are controlled so that the direct voltage of the capacitive circuit 312 is balanced between the first and second capacitors 313 and 314.

Each of the controllers 140, 240, and 340 shown in figures 1 a, 2, and 3 comprises driver circuits for controlling the bi-directional controllable switches. Furthermore, each of the controllers 140, 240, and 340 may comprise a processing system for running the driver circuits. The processing system may comprise one or more analogue circuits, one or more digital processing circuits, or a combination thereof. Each digital processing circuit can be a programmable processor circuit provided with appropriate software, a dedicated hardware processor such as for example an application specific integrated circuit “ASIC”, or a configurable hardware processor such as for example a field programmable gate array “FPGA”. Furthermore, the processing system may comprise one or more memory circuits each of which can be for example a Random-Access Memory “RAM” circuit.

In the exemplifying systems described above with reference to figures 1 a-1 f, 2, and 3, the alternating voltages constitute a three-phase system. It is to be noted that different number of phases are also possible in systems according to different embodiments of the invention. Furthermore, it is to be noted that the invention is not limited to any specific electrolysis processes and/or any specific electrodialysis processes. For example, a system according to an exemplifying and non-limiting embodiment may comprise an electrochemical reactor for proton exchange membrane “PEM” water electrolysis, an electrochemical reactor for a solid oxide electrolyte cell “SOEC” process, or an electrochemical reactor for some other electrolysis process.

Figure 4 shows a flowchart of a method according to an exemplifying and nonlimiting embodiment for supplying electric power to an electrochemical process such as e.g. water electrolysis or electrodialysis. The method comprises the following actions:

- action 401 : supplying alternating voltages via a transformer to a rectifier, and

- action 401 : supplying direct current from the rectifier to an electrochemical reactor to carry out the electrochemical process, wherein the rectifier comprises:

- an alternating voltage terminal which receives the alternating voltages,

- a direct voltage terminal which supplies the direct current to electrodes of the electrochemical reactor,

- a diode bridge between the alternating voltage terminal and the direct voltage terminal, and

- switching circuitries that act as bi-directional controllable switches which are: i) capable of conducting and blocking electric current in both directions, ii) connected to the alternating voltage terminal, and iii) connected to each other to form a star- or a delta-connection.

A method according to an exemplifying and non-limiting embodiment comprises changing a transformation ratio of the transformer with a tap-changer to control direct voltage supplied to the electrochemical reactor.

In a method according to an exemplifying and non-limiting embodiment, the rectifier comprises a capacitive circuit connected between positive and negative direct voltage poles of the diode bridge.

In a method according to an exemplifying and non-limiting embodiment, the bidirectional controllable switches are connected to each other to form the star- connection, and the capacitive circuit comprises a first capacitor connected between the positive direct voltage pole of the diode bridge and a star-point of the starconnection, and a second capacitor connected between the negative direct voltage pole of the diode bridge and the star-point of the star-connection.

In a method according to an exemplifying and non-limiting embodiment, the electrochemical reactor is a first one of two electrochemical reactors, the direct voltage terminal is a first one of two direct voltage terminals of the rectifier, the first one of the direct voltage terminals is constituted by the positive direct voltage pole of the diode bridge and the above-mentioned star-point of the star-connection, and a second one of the direct voltage terminals is constituted by the star-point of the star-connection and the negative direct voltage pole of the diode bridge. In the method according to this exemplifying and non-limiting embodiment:

- direct current is supplied to the first one of the electrochemical reactors via the first one of the direct voltage terminals, and

- direct current is supplied to the second one of the electrochemical reactors via the second one of the direct voltage terminals.

In a method according to an exemplifying and non-limiting embodiment, the switching circuitries limit a range of variation of an electric potential of the star-point so that the switching circuitries allow electric current from the star-point to the positive direct voltage pole of the diode bridge in response to a situation in which an electric potential of the star-point exceeds an electric potential of the positive direct voltage pole of the diode bridge and allow electric current from the negative direct voltage pole of the diode bridge to the star-point in response to a situation in which an electric potential of the negative direct voltage pole of the diode bridge exceeds the electric potential of the star-point.

In a method according to an exemplifying and non-limiting embodiment, the alternating voltages are supplied from the transformer to the rectifier via a grid filter. In a method according to an exemplifying and non-limiting embodiment, the grid filter comprises serial inductors between the transformer and the rectifier. In a method according to an exemplifying and non-limiting embodiment, the grid filter further comprises an inductor-capacitor “LC” filter so that the inductor-capacitor filter and the serial inductors constitute an inductor-capacitor-inductor “LCL” filter.

In a method according to an exemplifying and non-limiting embodiment, the electrochemical process is an electrolysis process that can be for example an alkaline water electrolysis process, a proton exchange membrane “PEM” water electrolysis process, or a solid oxide electrolyte cell “SOEC” process.

In a method according to an exemplifying and non-limiting embodiment, the electrochemical process is an electrodialysis process such as e.g. desalination of water. The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.