A method for extending the voltage range of a rectifier, a rectifier for performing that method, and an electrolytic system
By exchanging reactive power between the AC/DC converter and the AC grid, the DC voltage range of rectifiers is expanded, addressing inefficiencies and high losses in electrolytic cells, enabling efficient and controlled electrolysis.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SMA SOLAR TECH AG
- Filing Date
- 2021-04-13
- Publication Date
- 2026-05-20
AI Technical Summary
Existing rectifiers have limited DC voltage ranges, especially when operating below the critical voltage, leading to high conversion losses and inefficiencies in electrolytic cells, and there is a need for a method to expand this range while minimizing losses.
A method involving the exchange of reactive power between the AC/DC converter and the AC grid using inductance to adjust the AC voltage amplitude, allowing the DC voltage to be set below the critical value, with minimal hardware adaptation, using existing semiconductor switches and freewheeling diodes.
This approach extends the DC voltage range of the rectifier, enabling efficient operation of electrolytic cells at lower voltages with reduced conversion losses and controlled transitions, thus optimizing electrolysis processes.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for extending the DC voltage range of a rectifier, a rectifier for carrying out the method, and an electrolytic system having such a rectifier. [Background technology]
[0002] Hydrogen can be produced in an electrolytic cell by an electrolytic reaction that decomposes water into its constituent substances, hydrogen and oxygen. The rate of the electrolytic reaction is set by the DC voltage applied to the input of the electrolytic cell. The DC voltage is usually generated by a rectifier, with the input side of the rectifier connected to an AC grid and the output side connected to a DC load in the form of an electrolytic cell. In many cases, an actively controlled single-stage rectifier is used as the rectifier. The converter circuit of the AC / DC converter assigned to the rectifier includes multiple semiconductor switches, each containing a freewheeling diode, which is connected to each semiconductor switch in an antiparallel configuration. The antiparallel connection of the freewheeling diodes limits the minimum DC voltage at the DC output of the AC / DC converter to the amplitude of the AC voltage applied to the input side of the AC / DC converter. That is, the minimum DC voltage at the DC output of the AC / DC converter corresponds to the amplitude of the AC voltage applied to the input side of the AC / DC converter. This is true when the DC output of an AC / DC converter has at least a primarily capacitive DC load, performing DC voltage smoothing to the extent that the DC output voltage ripple can be ignored. As the ohmic component of the DC load increases, the voltage ripple at the DC output of the AC / DC converter becomes more pronounced, and the minimum DC voltage is slightly reduced. In this case, the minimum DC voltage at the DC output is usually expressed as the "rectified value." The rectified value corresponds to the arithmetic mean of the rectified DC voltages and depends on the rectifier used, and especially on the topology of the AC / DC converter.
[0003] Conventional electrolytic cells are typically characterized by a current-voltage characteristic curve (IU curve). The IU curve is divided into two regions: the DC voltage present at the input of the electrolytic cell is the critical voltage U.cr If the value falls below this level, the electrolytic reaction has not yet progressed, and therefore no steady-state current is flowing. The electrolytic cell exhibits a primarily capacitive response, which is related to the configuration of the double layer within the electrolytic cell. Critical voltage U cr Electrolysis only occurs when the DC voltage exceeds a certain level, and the rate of this reaction increases as the DC voltage rises. In this region, a steady current flows to promote the electrolysis, and the electrolytic cell primarily acts as an ohmic load here. Maximum allowable DC voltage U DC,max This is limited by the rated capacity or component characteristics of the electrolytic cell. Critical voltage U cr and maximum allowable DC voltage U DC,max The value depends on the design of the electrolytic cell and, as a result, usually differs from type to type.
[0004] Generally, it is desirable that the electrolytic cell be continuously adjustable by a rectifier and be able to operate over the entire operating range of the DC voltage applied to the input, but at least the critical voltage U cr From a voltage slightly lower than the maximum allowable DC voltage U DC,max It must be able to operate within the range up to [a certain value]. Furthermore, it is desirable to generate a high reaction rate and the associated high DC voltage at the input of the electrolytic cell while minimizing conversion losses in the rectifier. In a single-stage rectifier, a critical voltage U is required at the DC rectifier output. cr To generate only DC voltages below a certain level, the amplitude of the AC voltage at the AC input of the converter circuit can be adjusted to a correspondingly lower value, for example, by a transformer. However, this results in high conversion losses when a high DC voltage is required at the DC rectifier output during the operation of the electrolytic cell.
[0005] Prior art, such as document WO2013 / 160486A2, provides a method for performing voltage correction at the node point of the AC grid where a regenerative power generation system is connected to the AC grid. When the amplitude of the AC voltage deviates from its specified nominal value, reactive power is exchanged between the regenerative power generation system and the AC grid. This exchanged reactive power cancels out the deviation in a way that supports the grid system in order to minimize the deviation.
[0006] Document DE10303710A1 discloses a method for adjusting a self-rectifying line converter having a DC voltage output section in case of line overvoltage. In this method, a target value of the reactive component of the line current is defined according to a specified line overvoltage value, whereby the actual value of the duty cycle of the self-rectifying line converter is reduced. SUMMARY OF THE INVENTION
[0007] Objective of the present invention An object of the present invention is to provide a method for expanding the DC voltage range of an active controlled rectifier, particularly to set a DC voltage at a value slightly lower than the critical voltage U cr even when the critical voltage undershoots the nominal value with respect to the amplitude of the AC voltage, for expanding the DC voltage range of a half-wave rectifier having a DC output section of the half-wave rectifier. Further, it is necessary to be able to set a high DC voltage at the DC rectifier output section with minimal conversion losses. This method is intended to be as simple as possible to implement and cost-effective. A further object of the present invention is to disclose a suitable rectifier for carrying out this method, and to disclose an electrolysis system having such a rectifier.
[0008] solution According to the present invention, this object is achieved by a method of the above-described type having the features of independent claim 1. According to the present invention, the object of disclosing a suitable rectifier for carrying out this method is satisfied by the features of independent claim l0. According to the present invention, the object of disclosing an electrolysis system having such a rectifier is satisfied by the features of independent claim 14. Advantageous aspects of the method are described in claims 2 to 9, and advantageous embodiments of the rectifier are described in claims 11 to 13. Advantageous embodiments of the electrolysis system are shown in claims 15 and 16.
[0009] Description of the present invention The present invention aims to extend the DC voltage range of a rectifier for supplying a DC load connected to a DC rectifier output from an AC voltage (AC) grid, wherein the AC rectifier input of the rectifier is connected to the AC grid via a grid connection point. The rectifier comprises an AC / DC converter having an AC input and a DC output, and this AC / DC converter comprises a converter circuit having a semiconductor switch and a freewheeling diode connected in antiparallel thereto. The AC input of the AC / DC converter is optionally connected to the AC rectifier input via an AC isolation unit, and the DC output of the AC / DC converter is optionally connected to the DC rectifier output via a DC isolation unit. An inductance L is placed between the AC input of the AC / DC converter and the grid connection point. -The operation of the semiconductor switch of the AC / DC converter provides the desired DC operating voltage U to the DC output section and / or DC rectifier output section of the AC / DC converter. DC,Soll Includes the step of setting, - Desired DC operating voltage U DC,Soll When the amplitude U4 of the AC voltage at the AC input of the AC / DC converter falls below the value of the AC / DC converter's semiconductor switch is activated to exchange reactive power Q1(t) with the AC grid. This exchange of reactive power Q1(t) has a voltage drop effect on the amplitude U4 of the AC input of the AC / DC converter, and consequently on the AC input of the converter circuit. Due to this voltage drop effect, the amplitude U4 of the AC voltage becomes the desired DC operating voltage U DC,Soll Approaching the desired DC operating voltage U DC,Soll The approach of amplitude U4 to the desired DC operating voltage U (unless the allowable reactive power exchange with the AC grid, for example, according to instructions issued by the AC grid operator, restricts this approach) DC,Soll This is also achieved. The exchange of reactive power Q1(t) with the AC grid is performed simultaneously with the electrical connection and / or electrical disconnection of the DC load to and from the rectifier.
[0010] Here, the term "at the same time" should be understood as "during and / or immediately before." In particular, the rectifier can be a single-stage rectifier without a DC / DC converter, placed between the AC / DC converter and the DC rectifier output. The rectifier may include only one phase terminal on the AC side, but alternatively, it may also include multiple phase terminals. The AC input of the AC / DC converter corresponds to the AC input of the converter circuit, but since the latter is connected to the latter in at least a low-impedance configuration, the amplitude U4 applied to the AC input of the AC / DC converter also corresponds to the amplitude applied to the AC input of the converter circuit.
[0011] The amplitude U4 of the AC voltage applied to the AC input of an AC / DC converter and the amplitude U7 of the AC voltage applied to the AC rectifier input of a rectifier can each include the amplitude of the dominant AC voltage of the phase conductors relative to the neutral point or star point of the transformer, i.e., the amplitude of the phase-neutral voltage. This is especially true when the converter circuit of an AC / DC converter is configured in the form of a star connection. In this case, the output terminal of the DC output can be connected to the neutral point of the transformer or the neutral conductor of the AC grid. Alternatively, the amplitude U4 of the AC voltage applied to the AC input of an AC / DC converter can also be the amplitude of the dominant AC voltage between the two phase conductors of the AC grid, i.e., the amplitude of the interconnection voltage. The same applies to the amplitude U7 of the AC voltage applied to the AC rectifier input of a rectifier. This is especially true when the converter circuit of an AC / DC converter is configured in the form of a "bridge circuit". In this case, since the current flows only between the phase conductors of the AC grid, there is no requirement for a transformer with a neutral point tap. For example, in a three-phase AC grid, the amplitudes of the neutral point voltage and the interconnection voltage are correlated by an interconnection coefficient of √3.
[0012] The method according to the present invention utilizes the finding that the amplitude U4 of the AC voltage applied to the AC input of an AC / DC converter fluctuates due to the exchange of reactive power between the AC / DC converter and the AC grid via the interposed arrangement of an inductance L. Specifically, the amplitude U4 of the AC voltage can be reduced by the exchange of one type of reactive power, such as inductive reactive power, while it can be increased by the exchange of a complementary type of reactive power, such as capacitive reactive power. In the present invention, the exchange of reactive power Q1(t) is intentionally used to change the amplitude U4 of the AC voltage so as to affect the DC voltage of the DC output section of the converter circuit, and thereby also affect the DC voltage of the DC rectifier output section when the DC isolation unit is closed. For example, the DC rectifier output section (and thus the DC output section of the AC / DC converter) is subjected to a DC operating voltage U lower than the amplitude U4 of the AC voltage of the AC input section of the AC / DC converter. DC,Soll When attempting to set the desired DC operating voltage U4, a short-term exchange of reactive power Q1(t) with the AC grid is performed. The current associated with the reactive power Q1(t) flows through the inductance L, causing a voltage drop effect on the amplitude U4 of the AC voltage. This reduces the amplitude U4 of the AC voltage applied to the AC / DC converter. The reduced amplitude U4 generates a similarly reduced DC voltage at the DC output section of the converter circuit, i.e., the DC rectifier output section, via the freewheeling diode of the converter circuit. Depending on the amount of reactive power Q1(t) exchanged, it is possible to set the rate of decrease or increase of the amplitude U4 compared to the original amplitude U4, i.e., before the reactive power exchange. The short-term exchange of reactive power Q1(t) affects the amplitude U4 of the AC input section of the AC / DC converter, and consequently the DC voltage of the DC output section of the AC / DC converter, resulting in the desired DC operating voltage U4. DC,Soll The system is operated to approach the desired DC operating voltage U (depending on the maximum possible or allowable replacement of reactive power Q1(t)). DC,Soll This will also be achieved.
[0013] Unlike known prior art, the exchange of reactive power Q1(t) between the AC / DC converter and the AC grid is not performed with the purpose of canceling out existing deviations in the AC voltage amplitude to support the AC grid. In this case, unlike the prior art, the purpose of the exchange of reactive power Q1(t) is to intentionally deviate the amplitude U4 from its nominal value, at least temporarily. The resulting intentional deviation of the amplitude from the nominal value is used, according to the present invention, to operate a DC load, particularly an electrolytic cell, at a lower DC voltage at its input, at least temporarily, than in other cases. Thus, a short-term change in DC voltage, in this case a drop in DC voltage, is the actual purpose of the exchange of reactive power Q1(t). This provides the least possible load-free arrangement for connecting or disconnecting the DC load, particularly the electrolytic cell, to the rectifier, thereby enabling protective operation of the disconnection unit and the electrolytic cell.
[0014] According to the present invention, the exchange of reactive power Q1(t) is performed during and / or immediately before the connection of the DC load to the rectifier. After the electrical connection of the DC load to the rectifier, and especially immediately thereafter, it is possible, but not necessarily, to perform a further exchange of reactive power Q1(t) with the AC grid. Specifically, when the DC load is an electrolytic cell, the voltage at the input of the electrolytic cell is the critical voltage U crIt can be reduced to a value slightly lower than that. As a result, the connection and disconnection of the electrolytic cell to and from the rectifier can be performed in a way that is as unloaded and protective as possible for each disconnection unit. A controlled and gradual start and / or termination of the electrolytic reaction can also be achieved by a change in the reactive power Q1(t) exchanged. Specifically, at the start of the electrolytic reaction, the active power P(t) converted can be increased while the exchange of reactive power Q1(t) can be decreased. Similarly, at the end of the electrolytic reaction, the active power converted can be decreased while the exchange of reactive power can be increased simultaneously to further reduce the DC voltage at the DC output section of the AC / DC converter. Furthermore, after the DC load is disconnected from the rectifier, and especially immediately thereafter, it is possible, but not necessarily required, to perform a further exchange of reactive power Q1(t) with the AC grid. For this reason, for example, the exchange of reactive power Q1(t) with the AC grid can be reduced in a particularly stable and controlled manner, for example, by a controlled downward slope. In this way, abrupt changes in the reactive power Q1(t) exchanged with the AC grid, and the resulting undesirable reactions occurring in the AC grid, can be prevented.
[0015] Inductance L is a component of a rectifier that is at least to some extent normally present. Specifically, in the rectifier considered here, a filter is provided between the AC rectifier input and the AC input of the AC / DC converter to attenuate high-frequency interference signals, and this filter comprises one or more filter reactors. In many cases, one or more filter reactors can be employed as an element of inductance L with no or at least minimal adaptation, and the exchange of reactive power Q1(t) with the AC grid is performed through this inductance. For this reason, in many cases no additional hardware is required, or only to a limited extent. Similarly, with respect to the semiconductor switches of the converter circuit, there is no requirement for hardware adaptation for the exchange of reactive power Q1(t), only the duty cycle of the software needs to be adjusted. Overall, this can result in a relatively cost-effective and uncomplicated adaptation of a conventional rectifier to carry out the method according to the present invention.
[0016] In one advantageous embodiment of this method, the reactive power Q1(t) exchanged between the AC / DC converter and the AC grid is substantially composed solely of displacement reactive power, or at least almost entirely displacement reactive power. Therefore, it contains either no or only unavoidable components of distortion reactive power. This ensures that the desired sinusoidal waveform of the AC voltage is maintained even with the exchange of reactive power Q1(t).
[0017] In a further embodiment of this method, the exchange of reactive power Q1(t) between the AC / DC converter and the AC grid is performed to obtain a desired DC operating voltage U DC,soll This is only possible if the amplitude U4 is less than a specific difference value. For example, the desired DC operating voltage U DC,soll However, if, in addition to the value of amplitude U4, the rectified value of the AC voltage at amplitude U4 also undershoots, the exchange of reactive power can be promoted. In this way, when the DC load mainly has an ohmic component, the unwanted exchange of reactive power Q1(t) and the associated undesirable reactions in the grid can be reduced.
[0018] According to a further aspect of the present invention, the exchange of reactive power Q1(t) is used not only to decrease the amplitude U4 of the AC voltage but also to increase it. In the latter case, under specific operating conditions of a DC load, for example, a desired DC operating voltage U DC,Soll The voltage threshold U TH If the voltage reaches or exceeds this value, the semiconductor switch of the AC / DC converter is activated to exchange additional reactive power Q2(t) with the AC grid, and this exchange of additional reactive power Q2(t) is intended to cause a voltage increase in amplitude U4 at the AC input of the converter circuit. In this way, the desired DC operating voltage U is also achieved. DC,Soll The amplitude can be brought closer to U4. Furthermore, the additional reactive power Q2(t) can be complementary to the reactive power Q1(t). That is, if the reactive power Q1(t) is inductive reactive power, the additional reactive power Q2(t) can be capacitive reactive power, and vice versa. In this case, the AC / DC converter is required to rectify the AC voltage and, at the same time, slightly boost the DC voltage present in the AC output section of the AC / DC converter. Overall, this reduces the conversion loss of the AC / DC converter.
[0019] The exchange of reactive power Q1(t) and / or further reactive power Q2(t) may include determining a reactive power target value based on a known voltage fluctuation characteristic u(Q) as a function of the reactive power Q exchanged between the AC input of the AC / DC converter and the grid connection point of the AC grid. Specifically, the relationship with the known voltage fluctuation characteristic u(Q) can be determined, for example, only once and stored in a data memory connected to the rectifier control unit. Alternatively, the exchange of reactive power Q1(t) and / or further reactive power Q2(t) can be performed adaptively by adjustment units connected to the control unit. The DC voltage U present at the AC output of the AC / DC converter DC,4 The actual value is detected, and the detected actual value is the desired DC operating voltage U DC,Soll The actual value is compared to the desired DC operating voltage U DC,SollEach reactive power Q approaches 1,2 The exchange of (t) can be adjusted. The adjustment unit may include a proportional controller, an integral controller, and / or a differential controller.
[0020] Whether the exchange of reactive power Q1(t) and / or further reactive power Q2(t) is performed by a known voltage fluctuation characteristic u(Q) or adaptively by an adjustment unit, the exchange of reactive power Q1(t) and / or further reactive power Q2(t) can result in a change in amplitude U4 of at least 10%, preferably at least 20%, and particularly preferably at least 25% of the nominal value of amplitude U4 at the AC input of the AC / DC converter. The amount of reactive power Q to be exchanged required to produce the corresponding change in amplitude U4 is... 1,2 The amount of (t) depends on the value of the inductance L between the AC / DC converter and the grid connection point. Here, the nominal value of the amplitude U4 is the reactive power Q between the AC / DC converter and the AC grid. 1,2 This is understood as the value of amplitude U4 that would be present in the AC input of the AC / DC converter if (t) were not replaced.
[0021] In an advantageous embodiment of this method, under certain limiting conditions, for example, for voltage stability, a grid service exchange of reactive power between the AC / DC converter and the AC grid can be performed. Specifically, during AC grid conditions where the amplitude U7 of the AC voltage at the AC rectifier input deviates from its nominal value, a third reactive power Q3(t) can be exchanged between the AC / DC converter and the AC grid, causing a voltage drop or voltage rise in the AC voltage amplitude U7 depending on the quality of the third reactive power Q3(t). For voltage stability, the third reactive power Q3(t) is selected such that the resulting effect on the amplitude U7 cancels out the deviation from its nominal value. The specified limiting conditions may include ripple control signals and / or contractual agreements with the AC grid operator.
[0022] According to one embodiment of this method, the inductance may include a filter reactor positioned between the AC / DC converter and the AC rectifier input, through which reactive power Q1(t) and / or further reactive power Q2(t) are exchanged with the AC grid. Alternatively or additionally, the inductance may include the transformer winding on the secondary side of the transformer assigned to the rectifier. This is particularly true when the rectifier is connected to the AC grid via a transformer, with the rectifier connected to the secondary side of the transformer and the AC grid connected to the primary side of the transformer. In this type of configuration, at least one additional piece of equipment suitable for reactive power compensation may be further connected to the AC grid, i.e., the primary side of the transformer, which can function as a sink for the reactive power Q1(t) and / or further reactive power Q2(t) exchanged with the AC grid by the AC / DC converter. The appropriate equipment for reactive power compensation can be controlled in cooperation with the rectifier, thereby performing the exchange of its reactive power with the AC grid. Because the additional equipment acts as a sink for the reactive power exchanged with the AC grid by the AC / DC converter, the reaction in the AC grid associated with the exchange of reactive power can be eliminated or at least reduced. Therefore, the AC grid operator does not need to secure additional equipment to perform the necessary reactive power compensation. Thus, the permissible component of reactive power exchanged with the AC grid can be optionally increased.
[0023] The rectifier according to the present invention is comprised of an active-controlled rectifier configured to supply power from an AC grid having an AC voltage to a DC load. This rectifier is - An AC rectifier input section having multiple input terminals for connecting to an AC grid, and a DC rectifier output section having two output terminals for connecting to a DC load, - The AC / DC converter includes an AC input section connected to an AC rectifier input section, a DC output section connected to a DC rectifier output section, and a converter circuit positioned between the AC input section and the DC output section. The converter circuit of the AC / DC converter includes an actively controllable semiconductor switch and a freewheeling diode connected to it in antiparallel. In addition to its rectification function, the AC / DC converter also controls the AC grid and reactive power Q 1,2 (t) is further configured and designed to replace the rectifier. The rectifier further includes a control unit for controlling the AC / DC converter, in particular its semiconductor switches. The rectifier is characterized by being configured and designed to carry out the method according to the present invention.
[0024] The multiple input terminals of the rectifier may have only one phase terminal and a neutral conductor terminal. However, alternatively, they may include multiple phase terminals and not include a neutral conductor terminal, or they may include a single neutral conductor terminal. The advantages of the present method described above apply accordingly.
[0025] According to one advantageous embodiment, the rectifier includes an adjustment unit which adjusts the DC voltage of the DC output section of the AC / DC converter to a desired DC operating voltage U DC,Soll To get closer to it, if possible, the DC operating voltage U DC,Soll Until it reaches a certain point, it is configured and designed to work with the control unit to set the reactive power Q1(t) that is exchanged with the AC grid, and optionally an additional reactive power Q2(t). Specifically, the adjustment unit, - DC voltage U present in the DC output section and / or DC rectifier output section of the AC / DC converter DC,4 Detect, -Detected DC voltage U DC,4 and the desired DC operating voltage U DC,Soll Compare, -Detected DC voltage U DC,4 The desired DC operating voltage U DC,Soll Approaching the desired DC operating voltage U DC,SollThe AC / DC converter can be configured and designed to control the AC / DC converter in cooperation with a control unit to achieve a specific outcome. In this way, the AC / DC converter can adaptively respond to the voltage fluctuation characteristic u(Q) currently present between the AC input and the grid connection point of the AC / DC converter without requiring prior identification and optionally its storage. Alternatively, however, the voltage fluctuation characteristic u(Q) can be identified in advance as a function of reactive power Q, and the reactive power Q1(t) and / or further reactive power Q2(t) to be exchanged with the AC grid can be set according to the thus identified voltage fluctuation characteristic u(Q). For this purpose, the rectifier control unit can include, or be connected to, a data memory designed to store pairs of identified values reflecting the previously defined voltage fluctuation characteristic u(Q).
[0026] In one advantageous embodiment, the rectifier may include a filter unit having one or more filter reactors. At least one filter reactor may be positioned between the AC input of the AC / DC converter and the AC rectifier input. Thus, it constitutes at least one element of inductance through which reactive power Q1(t) and / or further reactive power Q2(t) are exchanged with the AC grid. Advantageously, the impedance of the filter reactor can be defined such that when a nominal current I0 flows through the filter reactor of the rectifier, a voltage drop of at least 25%, preferably at least 35%, and particularly preferably at least 45% occurs over the AC voltage present at the AC rectifier input. The impedance of the filter reactor, and thus its inductance L, along with additional current limiting in the event of a short circuit on the DC side, controls the reactive power Q 1,2 The replacement of (t) is first configured to provide a particularly effective voltage reduction effect with respect to amplitude. This additional current limiting minimizes the risk of damage to the converter circuit's freewheel diode in the event of a DC load short circuit.
[0027] The electrolytic system according to the present invention comprises a rectifier according to the present invention and an electrolytic cell as a DC load connected to the output side of the rectifier. The electrolytic system may further comprise a transformer, the secondary side of which is connected to the input of the AC rectifier and the primary side of which is connected to the AC grid via a grid connection point. If the electrolytic system includes a transformer, it may further comprise appropriate reactive power compensation equipment for reducing reactions on the grid. The appropriate reactive power compensation equipment is connected to the AC grid on the primary side of the transformer and acts as a sink for reactive power Q1(t) and / or further reactive power Q2(t) exchanged with the AC grid by an AC / DC converter. Here again, the advantages described above with respect to the present method apply. [Brief explanation of the drawing]
[0028] The present invention will be described below with reference to the drawings. [Figure 1] Figure 1 shows one embodiment of the electrolytic system according to the present invention, which has a rectifier according to the present invention. [Figure 2] Figure 2 shows one embodiment of the converter circuit of the rectifier according to the present invention shown in Figure 1. [Figure 3] Figure 3 schematically shows the temporal characteristics of the method according to the present invention in one embodiment. [Modes for carrying out the invention]
[0029] Figure 1 shows one embodiment of the electrolytic system 50 according to the present invention. The electrolytic system 50 comprises an electrolytic cell 22 as a DC load 20, a rectifier 1 according to the present invention, and a transformer 32. The primary side 32.P of the transformer 32 is connected to an AC voltage (AC) grid 30 via a grid connection point 31. The secondary side 32.S of the transformer 32 is connected to the AC rectifier input section 7 of the rectifier 1. The transformer 32 has an amplitude U Netz The primary AC voltage is converted into an AC voltage with amplitude U7 present on both the secondary side and the AC rectifier input section 7. The DC rectifier output section 8 of the rectifier 1 is connected to the input section 21 of the electrolytic cell 22.
[0030] Rectifier 1 controls the DC voltage U DC,Last This is an actively controllable rectifier designed to convert the AC voltage present on the input side into the DC voltage present in the DC rectifier output section 8 in order to supply power to the electrolytic cell 22. For this purpose, the rectifier 1 includes an AC / DC converter 4 having an AC input section 4.1 and a DC output section 4.2, which is controlled by a control unit 9. The AC input section 4.1 is connected to a filter reactor 3.1 and a filter capacitance 3.2 via a filter unit 3, and further connected to the AC rectifier input section 7 via an AC isolation unit 2. The DC output section 4.2 is connected to the DC rectifier output section 8 via a DC isolation unit 6. In parallel with the DC output section 4.2, the DC voltage U present in the DC output section 4.2 DC,4 An output capacitance 5 is connected to smooth the current. The DC isolation unit 6 includes two current paths, which are arranged in parallel with each other. The first current path includes a pre-charge resistor and an isolation switch connected in series and is used for pre-charging the electrolytic cell 22. The second current path, arranged in parallel with this, includes only an additional isolation switch. In addition to pre-charging, the electrolytic cell 22 operates within its ohmic range, and the closed additional isolation switch forms a low-impedance electrical connection between the DC output section 4.2 of the AC / DC converter 4 and the electrolytic cell 22. Both the DC isolation unit 2 and the AC isolation unit 6 are operated by the control unit 9 of the rectifier 1.
[0031] The rectifier 1 according to the present invention, through the corresponding operation of the semiconductor switches of the AC / DC converter 4, transmits reactive power Q to the AC grid 30 via the transformer 32. 1,2 It is configured to replace (t). Reactive power Q 1,2 The current associated with (t) flows through the inductance L formed by the filter reactor 3.1 of the filter unit 3 and the winding of the secondary side 32.S of the transformer 32, in the example shown in Figure 1. Reactive power Q 1,2 (t) is essentially composed solely of displacement reactive power, or at least almost entirely of displacement reactive power. Reactive power Q1,2 The replacement of (t) will be explained in more detail with reference to Figures 2 and 3, with regard to reactive power Q 1,2 Depending on the type of (t), a voltage drop or voltage rise effect is brought about on the amplitude U4 of the AC voltage applied to the AC input section 4.1 of the AC / DC converter 4, thereby extending the DC voltage range of the rectifier 1, in particular the AC / DC converter 4. On the other hand, the amount of reactive power to be exchanged can be set in cooperation with the control unit 9, for example by referring to a known voltage fluctuation characteristic u(Q) that is determined only once. For this purpose, the rectifier 1 may include a data memory 11 for storing pairs of values that reflect previously determined voltage fluctuation characteristics u(Q). Alternatively or additionally, the rectifier 1 may also include an adjustment unit 10, which adjusts the DC voltage U present in the DC output section 4.2 of the AC / DC converter. DC,4 Furthermore, it is configured to optionally detect the AC voltage of amplitude U4 present in the AC input section 4.1, and the detected DC voltage U DC,4 The desired DC operating voltage U DC,soll The DC voltage U is compared with the control unit 9, and the comparison result is sent to the control unit 9. DC,4 The desired operating voltage U DC,soll The reactive power Q is exchanged between the AC grid 30 and the AC / DC converter 4 to approach the desired operating voltage and reach it as close to the desired voltage as possible. 1,2 (t) is changed by the corresponding operation of the semiconductor switches of the AC / DC converter 4.
[0032] In Figure 1, the rectifier 1, transformer unit 32, and AC grid are shown exemplarily as three-phase components. However, according to the present invention, each of these can also be configured as a single-phase component. Furthermore, the control unit 9 of the rectifier 1 can be connected to a communication unit (not shown in Figure 1). This allows for the synchronous operation of additional reactive power compensation equipment connected to the AC grid on the primary side of the transformer to be initiated and coordinated.
[0033] Figure 2 shows in more detail one embodiment of the AC / DC converter 4 of Figure 1, assigned to the rectifier 1. Similar to the rectifier 1 of Figure 1, the AC / DC converter 4 is exemplary configured as a three-phase AC / DC converter 4 and comprises a converter circuit 40 having a total of three bridge arms 45. Each of the bridge arms 45 includes two series-connected semiconductor switches 41, each having a freewheeling diode 42 connected in antiparallel. The freewheeling diodes 42 can be configured as inherent diodes for each semiconductor switch 41 or as separate diodes. The semiconductor switches 41 can be MOSFETs or IGBT semiconductor switches. According to the three-phase configuration of the converter circuit 40, the AC input section 4.1 of the AC / DC converter 4 has three input terminals, each of which is connected to a connection point 46 of the two semiconductor switches 41 of the bridge arm 45 assigned to it. The DC output section 4.2 of the DC / AC converter 4 has positive (+) and negative (-) output terminals.
[0034] During conversion, the AC / DC converter 4 can transmit active power P(t) from the AC input section 4.1 to the DC output section 4.2, and optionally, it can also transmit it in the reverse direction from the DC output section to the AC input section 4.1. The AC / DC converter 4 can further transmit reactive power Q between the AC input section 4.1 of the AC / DC converter 4 and the AC grid 30 (not shown in Figure 2) connected to the AC input section 4.1. 1,2 (t) is configured to be replaced. For this purpose, a semiconductor switch 41 (not shown in Figure 2) of the control unit 9 is activated. Depending on the corresponding cycle rate of the semiconductor switch 41, the AC / DC converter 4 converts the AC voltage present in the AC input section 4.1 to the DC voltage U of the DC output section 4.2. DC,4 It can be converted to a DC voltage. The magnitude of the converted DC voltage, i.e., the DC voltage range, is the minimum DC voltage U DC,min and maximum DC voltage U DC,max It can take values between [values]. Minimum DC voltage U DC,minThe freewheel diode 42 limits the DC voltage U4 present in the AC input section 4.2 to a value corresponding to the amplitude U4 of the AC voltage (excluding the conduction voltage of the freewheel diode 42). The freewheel diode 42 limits the DC voltage U4 of the AC voltage applied to the input side to a value greater than (not less than, or at least not significantly less than) the amplitude U4 of the AC voltage applied to the input side. DC,4 The DC output section 4.2 can generate the DC voltage U4 on the output side relative to the amplitude U4 of the AC voltage on the input side. DC,4 As the ratio increases, the conversion loss increases. The AC / DC converter 4 transmits reactive power Q to the AC grid 30 via inductance L, for example, the inductance assigned to the secondary side of the filter reactor 3.1 and / or the transformer. 1,2 By swapping (t), a voltage drop or voltage rise effect is achieved with respect to the amplitude U4 of the AC voltage present on the AC input section 4.1. This will be explained in more detail with reference to Figure 3.
[0035] Figure 2 shows an exemplary two-stage converter circuit 40 having two voltage stages. However, the present invention also allows for converter circuits with more voltage stages than just two, such as three-stage or five-stage converter circuits. Furthermore, the present invention allows for the converter circuit to be configured in the form of a neutral point circuit. The output terminal (-) of the DC output section 4.2 can be connected to the neutral point tap of the transformer 32, through which the AC / DC converter 4 is connected to the AC grid 30. Alternatively, it can be connected to the neutral conductor of the AC grid 30.
[0036] Figure 3 schematically shows the temporal characteristics of the method according to the present invention in one embodiment that can be performed using the adjustment unit 10. Here, the DC voltage U of the DC output section 4.2 of the AC / DC converter 4 DC,4The time characteristics of the AC voltage amplitude U4 at the AC input section 4.1 of the AC / DC converter 4, and the reactive power Q1(t) exchanged between the AC / DC converter 4 and the AC grid 30 via the inductance L are plotted. In Figure 3, a positive value of the exchange of reactive power Q1(t) results in a voltage drop effect on the AC voltage amplitude U4. Next to the vertical axis in Figure 3, individual time characteristics are shown by different types of lines. These time characteristics illustrate an exemplary case that may occur, for example, when the electrolytic cell 22 as a DC load 20 is connected to the active control rectifier 1.
[0037] The starting point is a state where the electrolytic cell 22 is separated from the rectifier 1. However, precharging of the electrolytic cell 22 has already been performed, and the input DC voltage U DC,Last The critical voltage U cr The value is slightly lower, indicating that the electrolytic reaction has not yet progressed. (Time point t) <t I In this case, the reactive power Q1(t) is not initially exchanged between the AC / DC converter 4 and the AC grid 30, and t <t I In this case, Q1(t)=0. The value of the amplitude U4 of the AC voltage present in the AC input section 4.1 is above the critical voltage in order to minimize conversion losses as much as possible at a high electrolytic reaction rate.
[0038] time t I The electrolysis system 50 is then notified that the rectifier 1 is to be connected to the electrolytic cell 22. To perform this connection in the least load-bearing arrangement possible, or at least with a reduced compensation current, at time t I The first value U of the desired DC operating voltage thereafter DC,Soll,1 Similarly, the DC voltage U currently present at the input of the electrolytic cell 22 DC,Last It is set to this value. Therefore, the first value U of the desired DC operating voltage DC,Soll,1 The DC voltage U of the DC output section 4.2 is lower than the amplitude U4 of the AC voltage present on the AC input section 4.1, and excludes the conduction state voltage of the freewheeling diode 42. DC,4 Since this corresponds to amplitude U4, the DC voltage U present on the output side DC,4 It is also lower than the desired DC operating voltage UDC,Soll,1 and the DC voltage U existing on the output side DC,4 there is a relatively large difference ΔU(t I ). The adjustment unit 10 detects the DC voltage U existing on the output side DC,4 and compares it with the desired DC operating voltage U DC,Soll,1 to transmit the voltage difference ΔU(t I ) to the control unit 9. In response, the control unit 9 operates the semiconductor switch 41 of the converter circuit 40 in accordance with an increase in the reactive power Q1(t I ) exchanged with the AC grid 30. The exchange of the reactive power Q1(t) causes a voltage drop effect on the amplitude U4 of the AC voltage existing in the AC input section 4.1, particularly due to the flow of its accompanying current through the inductance L. As a result, the value of the amplitude U4 and the corresponding DC voltage U DC,4 (t) of the AC output section 4.2 of the AC / DC converter 4 decrease. Between t I and t II , the currently existing DC voltage U DC,4 (t) is continuously detected by the adjustment unit 10 and compared with the first value U DC,Soll,1 of the desired DC operating voltage. This comparison indicates a quantitative decrease in the difference ΔU(t), which is transmitted to the control unit 9. The control unit 9 operates the semiconductor switch 41 of the converter circuit 40 again for the purpose of further increasing the exchange of the reactive power Q1(t). The increase in the reactive power Q1(t), the accompanying decrease in the amplitude U4, and the decrease in the DC voltage U DC,4 of the DC output section 4.2 of the AC / DC converter 4 are executed until the difference between the DC voltage U I of the DC output section 4.2 of the AC / DC converter 4 and the first value U II of the desired DC operating voltage disappears between t DC,4 and t DC,Soll,1 . Finally, as a result, at the time point t II , the amplitude U4 of the input-side AC voltage and the DC voltage U DC,4 of the DC output section 4.2 of the AC / DC converter 4 reach the first value U DC,Soll,1 of the desired DC operating voltage. For this reason, at the time point t IIIn this case, the electrolytic cell 22 can be connected to the rectifier 1 in a low-impedance and substantially no-load configuration by closing the DC separation unit 6.
[0039] Time point t II After that, the first value U of the desired DC operating voltage DC,Soll,1 is replaced by the second value U of the desired DC operating voltage DC,Soll,2 where the electrolytic reaction is carried out. For this reason, during the time interval from t II to t IV the DC voltage U at the DC output section 4.2 of the AC / DC converter 4 DC,4 slopes towards the second value U of the currently applicable desired DC operating voltage. This is accompanied by the reactive power Q1(t) also sloping down to the value 0 during the time interval from t DC,Soll,2 to t II to t III After time point t III no further exchange of reactive power Q1(t) takes place between the AC / DC converter 4 and the AC grid 30, and the amplitude U4 of the AC voltage at the input section 4.2 of the AC / DC converter returns to its original value at t = 0.
[0040] The sloping characteristics of the reactive power Q1(t) and the DC voltage U at the DC output section 4.2 of the AC / DC converter 4 shown in FIG. 3 can also assume a steeper gradient than shown, and a substantially stepwise time variation can be observed. DC,4
[0041]
[0041] FIG. 3 shows the method according to the invention for potential execution in an adaptive manner by the adjustment unit 10. Detailed knowledge of the voltage fluctuation characteristic u(Q) between the grid connection point 31 of the AC grid 30 and the AC input section 4.1 of the AC / DC converter is not required. However, in the present invention, it is also possible to execute the method using the known voltage fluctuation characteristic u(Q). By referring to the known voltage fluctuation characteristic u(Q), in addition to the detection of the DC voltage U present at the DC output section 4.2 of the AC / DC converter 4 and the comparison with the first value U of the desired DC operating voltage DC,4 the corresponding voltage difference ΔU(t DC,soll,1 to IThe voltage difference ΔU(t) obtained in this way is then calculated. I By comparing this with known voltage fluctuation characteristics u(Q), the desired DC operating voltage U DC,soll,1 The reactive power Q1(t) required for the setting can be determined. In response, the control unit 9 can activate the semiconductor switch 42 of the AC / DC converter 4 to replace the required reactive power Q1(t). The method according to the present invention has been described with reference to the connection of the electrolytic cell 22 to the rectifier 1 in the least load configuration possible. However, alternatively or additionally, it can also be performed in combination with no-load isolation of the electrolytic cell 22 from the rectifier 1 by opening the DC isolation unit 6. Specifically, by short-term replacement of the reactive power Q1(t), the DC voltage U of the DC output section of the AC / DC converter 4, which is similarly present at its input section 21, is replaced immediately before and during the opening of the DC isolation unit 6 in the case of a low-impedance connection between the rectifier 1 and the electrolytic cell 22. DC,4 The limit voltage U required to maintain the electrolytic reaction cr It is possible to reduce it to less than [a certain level]. [Explanation of Symbols]
[0042] 1 rectifier 2 AC Isolation Units 3 filter units 3.1 Filter Reactor 3.2 Filter Capacitance 4 AC / DC Converters 4.1 AC Input Section (of AC / DC Converter) 4.2 DC Output Section (of AC / DC Converter) 5. Output capacitance (of the AC / DC converter) 6 DC Isolation Unit 7 AC Rectifier Input Section 8 DC rectifier output 9 Control Unit 10 Adjustment Unit 11 Data Memory 20 DC load 21 Input section (for DC load) 22 Electrolytic cell 30. AC (Alternating Current) Grid 31 Grid connection points 32 Transformers 32.P Primary side 32.S Secondary side 40 Converter Circuits 41 Semiconductor switches 42 Freewheeling diode 43 Input section (of the converter circuit) 44 Output section (of the converter circuit) 45 Bridge Arm 46 connection points Q1(t),Q2(t) Reactive power P(t) Active power U Netz ,U7,U4 amplitude U DC,4 Milk Voltage U DC,Soll Milk Voltage U DC,min ,U DC,max Milk Voltage U TH Voltage threshold
Claims
1. A method for extending the DC voltage range of a rectifier (1) for supplying power from an AC grid (30) to a DC load (20) connected to the DC rectifier output section (8) of the rectifier (1), The AC rectifier input section (7) of the rectifier (1) is connected to the AC grid (30) via the grid connection point (31). - The rectifier (1) comprises an AC / DC converter (4) having an AC input section (4.1) and a DC output section (4.2), and this AC / DC converter (4) comprises a converter circuit (40) having a semiconductor switch (41) and a freewheeling diode (42) connected thereto in antiparallel configuration. - An inductance L is connected between the AC input section (4.1) of the AC / DC converter (4) and the grid connection point (31). The method described above is - The operation of the semiconductor switch (41) of the AC / DC converter (4) causes the DC output section (4.2) and / or the DC rectifier output section (8) of the AC / DC converter (4) to produce a desired DC operating voltage U ＤＣ，Ｓｏｌｌ The step includes setting up - Desired DC operating voltage U ＤＣ，Ｓｏｌｌ When the amplitude U of the AC voltage at the AC input section (4.1) of the AC / DC converter (4) is lower than the value of ４ the semiconductor switch (41) of the AC / DC converter (4) is activated to exchange reactive power Q １ with the AC grid (30), and the current associated with the type of reactive power Q １ (t) flowing through the inductance L has a voltage drop effect on the amplitude U of the AC voltage at the AC input section (4.1) of the AC / DC converter (4), so that the amplitude U ４ approaches the desired DC operating voltage U ４ and reaches the desired DC operating voltage U ＤＣ，Ｓｏｌｌ as close as possible, and reaches the desired DC operating voltage U ＤＣ，Ｓｏｌｌ if possible, - Reactive power Q with respect to the AC grid (30) １ The replacement of (t) is performed at least one of the following: (i) during the operation of electrically connecting the DC load to the rectifier, (ii) immediately before the operation of electrically connecting the DC load to the rectifier, (iii) after the operation of electrically disconnecting the DC load from the rectifier, (iv) immediately before the operation of electrically disconnecting the DC load from the rectifier, and (v) during the operation of electrically disconnecting the DC load from the rectifier, and the operation of electrically connecting is performed by closing the DC isolation unit (6) located between the DC output unit (4.2) and the DC load (20), and the operation of electrically disconnecting is performed by opening the DC isolation unit (6). - The DC load (20) is an electrolytic cell, A method characterized by intentionally causing the amplitude U4 of the AC voltage to deviate from the nominal value by replacing the reactive power Q1(t), thereby reducing the voltage at the input of the electrolytic cell to a value below the critical voltage Ucr, and thereby achieving the operation of electrically connecting and electrically disconnecting the electrolytic cell with minimal load.
2. In the method according to claim 1, The method is characterized in that the inductance includes a filter reactor (3.1) positioned between the AC / DC converter (4) and the AC rectifier input section (7), and / or the transformer winding on the secondary side (32.S) of the transformer (32) assigned to the rectifier (1).
3. In the method according to claim 1 or 2, Desired DC operating voltage U ＤＣ，Ｓｏｌｌ The voltage threshold U ＴＨ If Q is reached or exceeded, the semiconductor switch (41) of the AC / DC converter (4) will further reduce the reactive power Q with the AC grid (30). ２ Activated to replace (t), the additional reactive power Q ２ (t) is the reactive power Q １ This is a type of reactive power complementary to type (t), and this further reactive power Q ２ The exchange of (t) causes the amplitude U in the AC input section (4.1) of the AC / DC converter (4) ４ It has a voltage-increasing effect on the amplitude U ４ The desired DC operating voltage U ＤＣ，Ｓｏｌｌ A method characterized by approaching [something].
4. In the method according to any one of claims 1 to 3, Reactive power Q １ (t) replacement and / or additional reactive power Q ２ The exchange of (t) includes determining a reactive power target value based on a known voltage fluctuation characteristic u(Q) as a function of the reactive power Q exchanged between the AC input section (4.1) of the AC / DC converter (4) and the grid connection point (31) of the AC grid (30), A method characterized in that the known voltage fluctuation characteristic u(Q) is determined in advance on a one-off basis and selectively stored in a data memory via a specified pair of values that reflect the voltage fluctuation characteristic u(Q).
5. In the method according to claim 1 or 2, DC voltage U present in the DC output section (4.2) of the AC / DC converter (4) ＤＣ，４ The actual value is detected, and the detected actual value is the desired DC operating voltage U ＤＣ，Ｓｏｌｌ The actual value is compared with the desired DC operating voltage U, and the adjustment unit (10) connected to the control unit (9) adjusts the actual value. ＤＣ，Ｓｏｌｌ To approach the aforementioned reactive power Q １ A method characterized by the control of the exchange of (t).
6. In the method according to claim 3, DC voltage U present in the DC output section (4.2) of the AC / DC converter (4) ＤＣ，４ The actual value is detected, and the detected actual value is the desired DC operating voltage U ＤＣ，Ｓｏｌｌ The actual value is compared with the desired DC operating voltage U, and the adjustment unit (10) connected to the control unit (9) adjusts the actual value. ＤＣ，Ｓｏｌｌ To approach this, the further reactive power Q ２ A method characterized by the control of the exchange of (t).
7. In the method according to any one of claims 1 to 6, Reactive power Q １ (t) replacement and / or additional reactive power Q ２ By exchanging (t), the amplitude U ４ The amplitude U of the AC input section (4.1) of the AC / DC converter (4) is at least 10%, preferably at least 20%, and particularly preferably at least 25% of the nominal value. ４ A method characterized by the occurrence of a change.
8. In the method according to any one of claims 1 to 7, The amplitude U of the AC voltage at the AC rectifier input section (7) ７ While the AC grid (30) is in a state where it deviates from its nominal value, under certain limit conditions, a third reactive power Q ３ The exchange of (t) is performed between the AC / DC converter (4) and the AC grid (30), thereby reducing the amplitude U ７ A method characterized in that the effect on cancels out the deviation from the nominal value.
9. In the method according to any one of claims 1 to 8, A method characterized in that, when the critical voltage U cr of the electrolytic cell falls below the minimum DC voltage at the DC output section (4.2) of the AC / DC converter (4) in the absence of reactive power Q1 (t) exchange, the voltage at the DC output section (4.2) of the AC / DC converter (4) is set to the critical voltage U cr or less by exchanging reactive power Q1 (t).
10. An actively controlled rectifier (1) for supplying power from an AC grid (30) having an AC voltage to a DC load (20), - An AC rectifier input section (7) having multiple input terminals for connecting to the AC grid (30), and a DC rectifier output section (8) having two output terminals for connecting to the DC load (20), - The AC / DC converter (4) comprises an AC-side AC input section (4.1) connected to the AC rectifier input section (7), a DC-side DC output section (4.2) connected to the DC rectifier output section (8), and a converter circuit (40) disposed between the AC input section (4.1) and the DC output section (4.2), - The converter circuit (40) of the AC / DC converter (4) comprises an actively controllable semiconductor switch (41) and a freewheeling diode (42) connected thereto in antiparallel configuration. - The AC / DC converter (4) and the AC grid (30) have a reactive power Q １，２ (t) is configured to be replaced, - The rectifier (1) further comprises a control unit (9) for controlling the AC / DC converter (4), particularly its semiconductor switch (41), A rectifier characterized in that the rectifier (1) is configured and designed to perform the method described in any one of claims 1 to 9.
11. In the rectifier (1) according to claim 10, The rectifier (1) includes an adjustment unit (10), and this adjustment unit adjusts the DC voltage U present in the DC output section (4.2) of the AC / DC converter (4) and / or the DC rectifier output section (8). ＤＣ，４ Detects the detected DC voltage U ＤＣ，４ The desired DC operating voltage U ＤＣ，Ｓｏｌｌ Compared with the detected DC voltage U ＤＣ，４ The desired DC operating voltage U ＤＣ，Ｓｏｌｌ Approaching the desired DC operating voltage U ＤＣ，Ｓｏｌｌ A rectifier characterized by being configured and designed to control the AC / DC converter (4) in cooperation with the control unit (9) to reach a certain value.
12. In the rectifier (1) according to claim 10 or 11, The control unit (9) includes or is connected to a data memory (11) designed to store voltage fluctuation characteristics u(Q) as a function of reactive power Q. A rectifier characterized in that the voltage fluctuation characteristic u(Q) is determined in advance on a one-off basis and selectively stored in the data memory (11) via a specified pair of values that reflect the voltage fluctuation characteristic u(Q).
13. In the rectifier (1) according to any one of claims 10 to 12, The rectifier (1) further comprises a filter unit (3) having a filter reactor (3.1), and a nominal current I is supplied to the filter reactor (3.1). ０ When flowing, the AC voltage U present at the AC rectifier input section (7) ７ A rectifier characterized in that the impedance of the filter reactor (3.1) is defined such that a voltage drop of at least 25%, preferably at least 35%, and particularly preferably at least 45% occurs.
14. An electrolytic system (50) comprising a rectifier (1) according to any one of claims 10 to 13, and an electrolytic cell (22) as a DC load (20) connected to the output side of the rectifier (1).
15. In the electrolytic system (50) according to claim 14, An electrolytic system further comprising a transformer (32), the secondary side (32.S) of which is connected to the AC rectifier input section (7), and the primary side (32.P) of which is connected to the AC grid (30) via a grid connection point (31).
16. In the electrolytic system (50) according to claim 15, The system further includes appropriate reactive power compensation equipment to reduce the reaction on the grid, which is connected to the AC grid (30) on the primary side (32.P) of the transformer (32) and exchanges with the AC grid (30) by the AC / DC converter (4) for reactive power Q １ (t) and / or further reactive power Q ２ An electrolytic system characterized by functioning as a sink for (t).