Electrolysis device with pulse power converter and transformer

Abstract

The invention relates to an electrolysis device (1) having precisely one pulse power converter (2), an electrolyzer (3), a transformer (4), and connections (6) for supplying with electric energy, wherein the transformer (4) is electrically connected to the connections (6) on the primary side in order to supply the transformer with electric energy, the pulse power converter (2) is electrically connected to the electrolyzer (3) on the DC voltage side, the pulse power converter (2) is electrically connected to a secondary side (42) of the transformer (4) on the AC voltage side, and the pulse power converter is designed to be operated with a pulse frequency (fP). In order to reduce the harmonic currents of the electrolysis device (1), the electrolysis device (1) is designed without a network filter. A stray inductance (Lσ) and / or a short circuit voltage (uK) of the transformer (4) is dimensioned such that harmonic currents between the transformer (4) and the connections (6) fall below a specifiable limit. The invention additionally relates to the use of a stray inductance (Lσ) of a transformer (4) of such an electrolysis device in order to reduce harmonic currents between the electrolysis device (1) and an energy supply network (7) and to a method for operating such an electrolysis device (1), the pulse power converter being operated with a pulse frequency (fP) at which the resulting harmonic currents between the transformer (4) and the connections (6) fall below the specified limit.

Description

[0001] Description

[0002] ELECTROLYSIS DEVICE WITH PULSE CONVERTER AND TRANSFORMER

[0003] The invention relates to an electrolysis device, comprising a pulse-controlled power converter, an electrolyzer, a transformer and connections for the supply of electrical energy, wherein the transformer is electrically connected on the primary side to the connections for the supply of electrical energy, wherein the pulse-controlled power converter is electrically connected on the DC side to the electrolyzer, wherein the pulse-controlled power converter is electrically connected on the AC side to a secondary side of the transformer, wherein the pulse-controlled power converter is designed to be operated at a pulse frequency. The invention further relates to the use of a stray inductance of a transformer of such an electrolysis device for reducing harmonic currents between the electrolysis device and a power supply network. Furthermore, the invention relates to a method for operating such an electrolysis device.

[0004] For electrolysis, power converters are used to generate a direct voltage from the alternating voltage of an energy source or a power supply network. These converters convert the alternating voltage from an energy source or a power grid into a direct voltage with which the electrolysis can take place in the electrolyzer. The power converter creates harmonics. These lead to currents on the alternating voltage side of the power converter, which are particularly undesirable for the power supply network. These currents are also referred to as harmonic currents. They are usually filtered out using filter circuits. These filters serve to prevent or suppress harmonics in the mains current and are therefore also referred to as mains filters. The mains current is the current between a power supply network and the electrolysis device. This can be measured, for example, at the connections of the electrolysis device.The mains filter has at least one inductance and one capacitance which are arranged together in a structural unit.

[0005] By staggering the timing of several pulse-controlled converters, it is possible for some of the harmonics to compensate for each other, i.e. to cancel each other out.

[0006] The invention is based on the object of reducing the harmonic currents of the electrolysis device.

[0007] This object is achieved by an electrolysis device having precisely one pulse-controlled power converter, one electrolyzer, one transformer and connections for supplying electrical energy, the transformer being electrically connected on the primary side to the connections for supplying electrical energy, the pulse-controlled power converter being electrically connected on the DC side to the electrolyzer, the pulse-controlled power converter being electrically connected on the AC side to a secondary side of the transformer, the pulse-controlled power converter being set up to be operated with a pulse frequency, the electrolysis device being designed without a mains filter, a stray inductance and / or a short-circuit voltage of the transformer being dimensioned such that harmonic currents between the transformer and the connections fall below a predeterminable limit.This object is further achieved by using a stray inductance of a transformer of such an electrolysis device to reduce harmonic currents between the electrolysis device and a power supply network. This object is further achieved by a method for operating such an electrolysis device, wherein the pulse-controlled converter is operated at a pulse frequency at which the harmonic currents that develop between the transformer and the terminals fall below the specified limit.

[0008] Further advantageous embodiments of the invention are specified in the dependent claims. The invention is based, inter alia, on the finding that the behavior of the pulse-controlled power converter of an electrolyzer can be improved with regard to the harmonic currents in the mains current by selecting a stray inductance of the transformer that is high enough to sufficiently reduce the harmonic currents. This means that a mains filter is not required. In other words, the electrolysis device is designed to be mains filter-free. Mains filter-free means that there is no mains filter in which a current is kept away from the mains in a structural unit via a combination of inductance and capacitance. The electrolysis device is designed to be connected to a power supply network or an energy source at the terminals for supplying electrical energy.For an electrolysis capacity of around 5 MVA, a medium-voltage supply from the power grid with a voltage in the range of 100 kV to 30 kV has proven advantageous. This results in nominal currents of around 100 A to 300 A between the power grid and the transformer or electrolysis device. For the electrolysis, a DC voltage of around 800 V (+ / - 20%) can be generated from this by the power converter in a particularly efficient manner. To ensure adequate suppression of harmonics by the transformer, a short-circuit voltage of u. K in the range of 10% to 25%, and especially in the range of 10% to 15%, has proven particularly effective. It has been shown that the additional cost of a transformer with such a short-circuit voltage is more cost-effective than a line filter for suppressing harmonics.

[0009] It has proven advantageous that the leakage inductance of the transformer is in the same order of magnitude as a filter choke of the power converter, as has been used to date to reduce harmonic currents. The transformer leakage can then be used as a working inductance to suppress the harmonic currents. Alternatively, it has proven advantageous to design the short-circuit voltage of the transformer instead of the leakage inductance in such a way that the formation of harmonic currents is sufficiently suppressed. Instead of requiring a certain leakage inductance for the transformer, the filtering effect is generated by a corresponding short-circuit voltage of the transformer. This short-circuit voltage is a fundamental property of the transformer that can be adapted to existing requirements when designing the transformer.

[0010] Another degree of freedom is the pulse frequency f P of the pulse-controlled converter in order to reduce the harmonics. The higher the pulse frequency, the lower the required leakage inductance of the transformer. In addition, it has also been shown that only a lower short-circuit voltage u p is required at the transformer in order to comply with a limit value for harmonic currents.

[0011] In an advantageous embodiment of the invention, the stray inductance and / or a short-circuit voltage of the transformer is dimensioned such that a current in the range of the pulse frequency and / or in the range of a multiple of the pulse frequency between the transformer and the connections falls below the predeterminable limit. A detailed examination of the pulse-controlled converter with regard to its behavior when generating harmonic currents has shown that these currents occur in a bundled manner in the range of the pulse frequency. The pulse frequency range in which these currents occur extends over a range of seven times the mains frequency or, depending on the impedance conditions at the mains connection point, thirteen times the mains frequency around the pulse frequency. In other words, the pulse frequency range extends from the pulse frequency minus seven times orThree ten times the mains frequency up to the pulse frequency plus seven times or three ten times the mains frequency. In addition, the power converter also generates harmonics in the range of multiples of the pulse frequency. The range of multiples of the pulse frequency extends from the multiple of the pulse frequency minus seven times or three ten times the mains frequency up to the multiple of the pulse frequency plus seven times or three ten times the mains frequency. The width of the range therefore remains the same for multiples of the pulse frequency as it is for a single pulse frequency.

[0012] It has proven advantageous to use the pulse frequency range and currents in the pulse frequency range when designing the transformer with regard to its leakage inductance or short-circuit voltage. In doing so, an effective value is calculated from the individual current components in this range, which describes the current in this pulse frequency range or in the range of the corresponding multiple of the pulse frequency. This results in particularly simple design of the leakage inductance or short-circuit voltage. These currents can be determined particularly easily, particularly by means of simulation, due to the known behavior of the pulse-controlled converter. This determination is therefore also independent of the grid parameters of the power supply network or other consumers in the vicinity of the electrolysis device. These are often not known during design or can only be determined by complex measurements.It has been shown that the consideration of the currents in the range of the pulse frequency and / or its multiples leads to a sufficient result in the dimensioning of the stray inductance and / or the short-circuit voltage.

[0013] In a further advantageous embodiment of the invention, a capacitor is arranged between the connections for the electrical energy supply and the pulse-controlled power converter. By arranging one or more capacitors in the connection between the connections for the electrical energy supply and the pulse-controlled power converter, any remaining harmonic currents can be further reduced. This means that higher harmonic currents in the pulse-controlled power converter or power converters can be permitted, which only require a lower stray inductance or a lower short-circuit voltage in the transformer. These are then suppressed or eliminated by the capacitor. Instead of a mains filter with coils and capacitors, only the capacitors can be used.Due to the associated lower energy storage in the electrolysis device, it is less prone to the formation of oscillations between the energy supply network and the electrolysis device or within the energy supply network.

[0014] In a further advantageous embodiment of the invention, the leakage inductance of the transformer and the capacitor form a blocking circuit with a resonant frequency in the range of the pulse frequency or in the range of a multiple of the pulse frequency. For this purpose, the capacitor is advantageously arranged between the transformer and the pulse-controlled power converter. The arrangement is then made, for example, in a parallel circuit in which a capacitor is connected to one of the phases and the capacitors are connected to one another at a star point. The blocking circuit suppresses the formation of harmonic currents in a narrow frequency band. It is therefore particularly suitable for suppressing currents in the range of the pulse frequency or a multiple of the pulse frequency since, in contrast to filtering with a mains filter, only a narrow range of frequencies needs to be eliminated.This results in a particularly simple and, due to the low vibration tendency of this arrangement, robust solution.

[0015] In a further advantageous embodiment of the invention, the electrolysis device has a control device for controlling the pulse-controlled power converter, which is set up to clock the pulse-controlled power converter at a higher pulse frequency when undesired interference currents occur. In order to reduce the effort required to generate a sufficiently large leakage inductance of the transformer, it has proven advantageous to operate the pulse-controlled power converter at a higher pulse frequency. This higher pulse frequency results in the spectrum of the harmonics shifting towards higher values. The higher values ​​result in a lower required value for the leakage inductance or also the short-circuit voltage of the transformer. The electrolysis device can therefore be designed not only to be redundant, but also to be cost-effective at the same time.The losses associated with increasing the pulse frequency can be compensated for in the power supply of an electrolyzer by increasing the voltage of the pulse-controlled converter. The higher voltage requires less current to achieve the same power. This allows the current to be reduced. This lowers the converter's conduction losses, so that the total losses can be kept constant with increasing pulse frequency when using the pulse-controlled converter in an electrolyzer, unlike in drive technology applications.

[0016] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. They show:

[0017] FIG 1 an example of a filterless

[0018] electrolysis device,

[0019] FIG 2 and FIG 3 each show an embodiment of an electrolysis device with a capacitor, FIG 4 and FIG 5 each show an embodiment of an electrolysis device with several pulse converters and

[0020] FIG 6 a typical frequency spectrum of a pulse converter.

[0021] 1 shows an electrolysis device 1 which is connected to a power supply network 7 via its connections 6 for supplying electrical energy. An electrolyzer 3 is supplied with a direct voltage generated by a pulse-controlled power converter 2. The pulse-controlled power converter is connected to the connections 6 on the alternating voltage side, advantageously three-phase, via a transformer 4. The connections 6 are located on the primary side 41 of the transformer 4 and the pulse-controlled power converter 2 is on the secondary side 42. The pulse-controlled power converter is controlled by a control device 11 which transmits switching signals to the pulse-controlled power converter 2. It can be seen that the electrolysis device 1 does not have a mains filter, i.e. it is designed without a mains filter.

[0022] 2 shows a further exemplary embodiment of the electrolysis device 1. Like the following exemplary embodiment in FIG. 3, this has a capacitor 5 which is arranged between the terminals 6 and the pulse-controlled power converter 2. In the exemplary embodiment in FIG. 2, this capacitor is arranged on the primary side 41 of the transformer 4. This means that any harmonic currents that arise, reduced by the stray inductance of the transformer 4, can develop but flow away via the capacitor 5 and are thus kept away from the power supply network 7. In the exemplary embodiment in FIG. 3, the capacitor 5 is arranged on the secondary side 42 of the transformer 4. In addition to the effect of the capacitor described above, it also acts as a blocking circuit.Viewed from the pulse converter 2 in the direction of terminals 6, the leakage inductance of the transformer 4 and the capacitor 5 form a parallel circuit which acts as a blocking circuit and blocks harmonic currents when the resonance frequency w. R in the range of the pulse frequency or in the range of multiples of the pulse frequency. To avoid repetition in the description of the embodiments in Figures 2 and 3, reference is made to the description of Figure 1 and to the reference numerals introduced there.

[0023] FIG. 4 shows an exemplary embodiment of the electrolysis device 1 with two pulse-controlled converters 2. These are arranged in parallel on the AC side, since a mains current is divided between the two pulse-controlled converters 2. On the DC side, these feed the same electrolyzer, as they are also arranged in parallel on the DC side at the intermediate circuit capacitor. However, this parallel connection on the DC side is not required. It is also possible, for example, for both pulse-controlled converters to each supply one or more electrolyzers 3 with electrical energy via a corresponding DC voltage. If the two pulse-controlled converters are clocked offset, which means a phase shift of 180°, the frequency components in the currents of the pulse frequency cancel each other out, and the stray inductance or the short-circuit voltage of the transformer 4 is limited to twice the pulse frequency f PThis reduces the leakage inductance or the short-circuit voltage of the transformer 4, so that the transformer 4 and the electrolysis device 1 can be manufactured more cost-effectively. To avoid repetition, reference is made to the description of Figures 1 to 3 and to the reference symbols used therein.

[0024] The described embodiments are preferably designed with three phases on the AC side. This allows a continuous supply of energy to the electrolysis device 1 from a conventional power grid 7, which nowadays is generally designed with three phases.

[0025] In the embodiment of FIG. 5, three pulse-controlled converters 2 are arranged in parallel on the AC voltage side. To avoid repetition, reference is made to the description of FIGS. 1 to 4 and to the reference symbols used there. Due to the three pulse-controlled converters, which are clocked offset, i.e. with a phase shift of 120°, the harmonic currents of the pulse frequency and twice the pulse frequency cancel each other out. The stray inductance and the short-circuit voltage of the transformer 4 are then limited to three times the pulse frequency f P This further reduces the stray inductance and the short-circuit voltage of the transformer 4, so that the transformer 4 and the electrolysis device 1 can be manufactured even more cost-effectively.

[0026] FIG. 6 shows a typical frequency spectrum of a pulse-controlled converter 2 which is clocked at a pulse frequency of 3000 Hz. Currents arise in the range of the clock frequency and in the range of multiples of the clock frequency. The ranges are shown with curly brackets. From the current components of the curly brackets, an effective value can be determined for the relevant range of the pulse frequency or for the range of the corresponding multiple of the pulse frequency and compared with a limit value. The stray inductance is then selected to be at least high enough that the corresponding harmonic current which develops falls below this limit value.

[0027] In summary, the invention relates to an electrolysis device 1, comprising a pulse converter 2, an electrolyzer 3, a transformer 4 and connections 6 for the supply of electrical energy, wherein the transformer 4 is electrically connected on the primary side to the connections 6 for the supply of electrical energy, wherein the pulse converter 2 is electrically connected on the DC side to the electrolyzer 3, wherein the pulse converter 2 is electrically connected on the AC side to a secondary side 42 of the transformer 4, wherein the pulse converter is set up to operate with a pulse frequency f P To reduce the harmonic currents of the electrolysis device 1, it is proposed that the electrolysis device 1 be designed without a mains filter, wherein a stray inductance L o and / or a short-circuit voltage u Kof the transformer 4 is dimensioned such that harmonic currents between the transformer 4 and the terminals 6 fall below a predeterminable limit. Furthermore, the invention relates to the use of a leakage inductance L o a transformer 4 of such an electrolysis device for reducing harmonic currents between the electrolysis device 1 and a power supply network

[0028] 7 . The invention further relates to a method for operating such an electrolysis device 1 , wherein the pulse converter is operated with a pulse frequency f P is operated at which the harmonic currents formed between the transformer 4 and the terminals 6 fall below the specified limit.

Claims

Patent claims 1. Electrolysis device (1), comprising exactly one pulse converter (2), an electrolyzer (3), a transformer (4) and connections (6) for the supply of electrical energy, wherein the transformer (4) is electrically connected on the primary side to the connections (6) for the supply of electrical energy, wherein the pulse converter (2) is electrically connected on the DC side to the electrolyzer (3), wherein the pulse converter (2) is electrically connected on the AC side to a secondary side (42) of the transformer (4), wherein the pulse converter (2) is set up to operate at a pulse frequency (f P ), characterized in that the electrolysis device (1) is designed without a mains filter, wherein a stray inductance (L o ) and / or a short-circuit voltage (u K) of the transformer (4) is dimensioned such that harmonic currents between the transformer (4) and the terminals (6) fall below a predeterminable limit.

2. Electrolysis device (1) according to claim 1, wherein the leakage inductance (L o ) and / or a short-circuit voltage (u K ) of the transformer (4) is dimensioned such that a current in the range of the pulse frequency (f P ) and / or in the range of a multiple of the pulse frequency (f P ) between the transformer (4) and the terminals (6) falls below the preset limit.

3. Electrolysis device (1) according to one of claims 1 or 2, wherein a capacitor (5) is arranged between the terminals (6) for the supply of electrical energy and the pulse converter (2) in parallel with the transformer (4).

4. Electrolysis device (1) according to claim 3, wherein the leakage inductance (L o) of the transformer (4) and the capacitor (5) form a blocking circuit with a resonant frequency (w R ) in the Pulse frequency range (f P ) or in the range of a multiple of the pulse frequency (f P ) form.

5. Electrolysis device (1) according to one of claims 1 to 4, wherein the electrolysis device has a control device (11) for controlling the pulse converter (2), which is designed to clock the pulse converter (2) with a higher pulse frequency when undesired interference currents occur.

6. Use of a leakage inductance (L o ) of a transformer (4) of an electrolysis device (1) according to one of claims 1 to 4 for reducing harmonic currents between the electrolysis device (1) and a power supply network (7).

7. A method for operating an electrolysis device (1) according to one of claims 1 to 6, wherein the pulse converter (2) is operated with a pulse frequency (fP ) in which the harmonic currents generated between the transformer (4) and the terminals (6) fall below the specified limit.

8. The method according to claim 7, wherein the pulse converter is operated with a pulse frequency (f P ), in which the currents formed are in the range of the pulse frequency (f P ) and / or in the range of a multiple of the pulse frequency (f P ) between the transformer (4) and the terminals (6) falls below the preset limit.

9. Method according to one of claims 7 or 8, wherein the pulse converter (2) is clocked at a higher pulse frequency when undesired interference currents occur.

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