DE202019100805U1 - Dc link - Google Patents

Abstract

DC intermediate circuit comprising a DC intermediate circuit supply unit (110) and at least one of the DC voltage supply unit DC voltage supplied capacitor arrangement (150) having a nominal voltage and a discharge voltage, which is greater than zero.

Description

The present invention relates to a DC voltage intermediate circuit.

State of the art

DC intermediate circuits are known in the art. They have one or more supply units (eg regulated mains rectifier), through which the DC voltage for the DC link is made available. From the intermediate circuit, the power is taken, for example, via inverters (so-called inverters) as alternating current, eg for electric drives. Voltage smoothing and buffering in the DC link can be provided by capacitors (so-called DC link capacitors). Such a solution with a designed in particular as an electrolytic capacitor buffer capacity is for example in the DE 10 2010 025 647 A1 shown.

The consumers determine the load in the DC intermediate circuit. For example, during acceleration or deceleration processes of electric motors as consumers high short-term peak loads are achieved. These short-term peak loads can lead to short-term voltage peaks (period of a few seconds). To reduce these short-term voltage peaks, high-performance energy storage devices, e.g. Supercapacitors or double-layer capacitors, are used, which are coupled for voltage adjustment with the DC link via a DC-DC converter. However, this is expensive.

Disclosure of the invention

The invention proposes a DC voltage intermediate circuit according to claim 1. Advantageous embodiments emerge from the respective subclaims and the following description.

The invention uses the measure to use in the DC voltage intermediate circuit a capacitor arrangement with a charge end voltage, a discharge end voltage which is greater than zero, and a nominal voltage therebetween. In particular, therefore, no conventional capacitor arrangements comprising e.g. Electrolytic or double-layer capacitors whose discharge voltage is zero used. A particularly suitable capacitor arrangement has at least 30% energy content at least 75% of the rated voltage in the discharged state. Preferably, the capacitor arrangement in the discharged state at about 10% energy content still about 80% of the rated voltage. The rated voltage itself usually corresponds to a wide state of charge range of about 40% to about 70%. In addition, the charging voltage increases up to the charging end voltage, below which it drops to the discharge end voltage.

In order to be able to make targeted use of these advantages, the voltage in the DC voltage intermediate circuit can be regulated to a nominal voltage value which corresponds to a charge state of the capacitor arrangement of at least 50% and at most 80%, preferably at least 60% and at most 70%. Since the energy (kWh) stored in the capacitor arrangement in this region is dependent on the charging voltage, buffering is used, for example. in the latter case 30-40% up and down available. A relationship between state of charge and voltage is at least for commercially available capacitors for the loaded and unloaded state, for example from data sheets known or at least ascertainable. In particular, the nominal voltage value may be the rated voltage of the capacitor arrangement.

If the voltage in the DC intermediate circuit drops below the nominal voltage value, e.g. as a result of power removal, the capacitor assembly is discharged and the DC link power supply automatically recharges power to maintain or recover the desired voltage. If the voltage in the DC intermediate circuit exceeds the nominal voltage value, e.g. as a result of consumer shutdown, the capacitor assembly is charged.

The invention has the advantage that a large part of the energy stored in the capacitor arrangement is available in a small voltage range and therefore in particular no DC-DC converter or the like. must be used to adjust the voltage levels between the DC link and capacitor assembly and yet a significant amount of storage capacity can be used. In contrast to the aforementioned DE102010025648A1 the voltage in the DC voltage intermediate circuit is adapted to the electrical properties of the capacitor arrangement, which is why a charger or a DC / DC converter between DC intermediate circuit and capacitor arrangement can be saved and a high proportion of the storable energy can be used with little control effort.

A capacitor arrangement with a discharge end voltage which is greater than zero has in particular so-called hybrid capacitors, for example lithium-ion capacitors and the like. on. As hybrid capacitors capacitors are referred to, which Store energy in at least two ways, for example electrostatically and electrochemically. Such capacitors combine the advantages of electrostatic (short charge and discharge times, high specific power (W / kg)) and electrochemical (high specific energy (Wh / kg)) energy storage. Hybrid capacitors have two different electrodes, a double-layer electrode that stores the electrical energy electrostatically in an electric Helmholtz double layer, and a battery-like electrode that stores the energy electrochemically. Their electrical capacitance is thus composed of the series connection of an electrode of a conventional double-layer capacitor with a static double-layer capacitance and a battery-like electrode with an electrochemical pseudo-capacitance.

Preferably, the capacitor arrangement comprises a dielectric material having the non-stoichiometric formula MeO _x , where Me is a metal and x = 1, 2, 3, such as MgO, CaO, Y 2 O 3, Sc 2 O 3, Fe 2 O 3, La 2 O 3, Nd 2 O 3, Sm 2 O 3, Yb 2 O 3 , Lu2O3, Pr2O3, CeO2, Er2O3, Dy2O3, Dy2O3, Gd2O3, Eu2O3, Bi2O3, BeO, AION, ZnO, MgTiO3, CaTiO3.

Preferably, the capacitor arrangement comprises as the electrolyte an aqueous solution, e.g. KOH and AI on.

The capacitor arrangement preferably has activated carbon (AC) as electrode and / or a hydrogen-storing metal (MeH) as electrode.

The capacitor arrangement preferably has at least one hybrid capacitor of the form MeO _x / KOH / MeH-AC and / or of the form MeO _x / KOH / AC.

One or more of the above configurations may be used to provide a hybrid capacitor with high specific power and energy.

Another advantage is that hybrid capacitors have a flatter discharge characteristic than supercapacitors or double-layer capacitors. As a result, the intermediate circuit voltage is less volatile and the consumers are easier to control. In addition, can be dispensed with a conventional DC link capacitor when hybrid capacitors are used with their high current carrying capacity. The provision of a separate buffer memory in addition to the DC link capacitor is eliminated and functions are fulfilled by the same component.

Preferably, the DC voltage intermediate supply unit is also configured to feed back energy into the supply network. This is advantageous in particular when the charge level of the capacitor arrangement is relatively high or full. Without regeneration, the electrical energy would then have to be converted into heat, in particular in a so-called braking resistor.

Preferably, the DC intermediate circuit supply unit is also arranged to supply an electric current (i.e., from the supply network to the DC link) flowing through it to a nominal value with an allowable tolerance of e.g. Limit +/- 10%. As a result, in particular network-side current and power peaks are reduced. In addition, going power or recovery requirement is preferably absorbed by the capacitor assembly.

Preferably, in the DC intermediate circuit, a braking resistor of the capacitor arrangement is connected in parallel when the voltage in the DC intermediate circuit exceeds the maximum permissible voltage. As a result, damage to the capacitor arrangement can be avoided. For safety reasons, the braking resistor should be able to accommodate either the total possible regenerative power of the consumers or this regenerative power minus the regenerative power of the DC intermediate circuit supply unit.

An increase in the storage capacity can be achieved if parallel to the capacitor arrangement 150 a lithium / ion battery is connected.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

list of figures

• 1 schematically shows a preferred embodiment of a DC intermediate circuit according to the invention.
• 2 shows charging and discharging characteristics of a preferred capacitor arrangement for different current values.
• 3 shows a preferred embodiment of a DC intermediate circuit according to the invention in a traction drive.
• 4 shows a further preferred embodiment of a DC intermediate circuit according to the invention in a traction drive.
• 5 shows a further preferred embodiment of a DC intermediate circuit according to the invention in a traction drive.

Embodiment (s) of the invention

In 1 a preferred embodiment of a DC intermediate circuit according to the invention is shown schematically and designated 100 in total. The DC voltage intermediate circuit has a DC regulator 110 formed DC intermediate circuit supply unit on the input side receives, for example, a two- or three-phase AC voltage from a supply network and this converts the output side into a DC voltage. This DC voltage is applied between two supply lines +/- of the DC intermediate circuit.

DC consumers are via DC-DC converters 120 connected to the supply lines. AC consumers, in particular electric motors, are via inverters 130 connected to the supply lines. Between the supply lines is by pressing a switch 141 a braking resistor 140 switchable to convert excess electrical energy into heat to prevent damage to the components.

According to the illustrated embodiment of the invention is also a capacitor arrangement 150 connected to the supply lines, which has a design or type-related rated voltage, end of charge and discharge voltage greater than zero. For example, the capacitor arrangement may comprise hybrid capacitors and in the discharged state at about 10% energy content still have about 80% of the nominal voltage. This is due to an electrochemical energy storage characteristic of the capacitor arrangement 150 due. For example, the nominal voltage 480 V, the end-of-charge voltage about 500 V and the discharge end voltage can be about 380 V. For this purpose, the capacitor arrangement 150 formed in particular as a capacitor bank comprising a plurality of capacitors. For example, N capacitors may be connected in series and M of such series may be connected in parallel, so that a total of NxM capacitors are present.

The DC voltage supply unit 110 is, in particular programmatically, arranged to regulate the voltage in the DC voltage intermediate circuit to a desired voltage value, which corresponds to a charge level of the capacitor arrangement of at least 50% and at most 80%, for example 70%. Thus, about 30% of the capacity is still available at the top and bottom for cushioning power and power peaks. If the voltage in the DC intermediate circuit drops below the nominal voltage value, eg as a result of power consumption, the capacitor arrangement is discharged and the DC intermediate circuit supply unit automatically charges power in order to maintain or reach the setpoint voltage. If the voltage in the DC voltage intermediate circuit exceeds the nominal voltage value, for example as a result of switching off consumers, the capacitor arrangement is charged.

For example, the DC voltage intermediate supply unit 150 also set up to feed energy back into the utility grid. This is advantageous in particular when the charge level of the capacitor arrangement 150 is relatively high or full. Without feedback, the electrical energy would then especially in the braking resistor 140 be converted into heat.

Preferably, the DC voltage intermediate supply unit 150 also adapted to limit the electric current through the DC intermediate circuit supply unit (ie from the supply network to the DC link or back) to a nominal value with an allowable tolerance of eg +/- 10%. As a result, in particular network-side current and power peaks are reduced and beyond going power or recovery is required by the capacitor arrangement 150 collected.

Exemplary charge and discharge characteristics of a preferred capacitor arrangement for different current values are shown in FIG 2 shown. In this case, the discharge voltage U is plotted against the charge level SOC in%, with a nominal voltage curve, which can be regulated, for example, with 210. Below the rated voltage curve run the discharge characteristics, the current drain increases from top to bottom. As is known, real energy sources have a finite internal resistance, so that the voltage decreases with increasing current drain. Above the rated voltage curve 210 The charging characteristics run, whereby the current consumption increases from bottom to top. A preferably usable within the scope of the invention range 220 is also marked. In particular, a setpoint voltage value which corresponds to approx. 60% - 70% SOC.

In the 3 to 5 now various preferred embodiments of a DC intermediate circuit according to the invention are shown, which is used in a traction drive. In each case, a driven vehicle axle with 300 designated.

In 3 is an internal combustion engine 310 , For example, a diesel engine, provided via a clutch 320 a hydraulic machine designed here as a variable displacement pump 330 drives. The pump 330 is via a hydraulic circuit with a hydraulic motor 340 connected, which the driving axle 300 drives. By adjusting the hydraulic pump 330 In particular, the driving speed can be varied.

The hydraulic pump 330 is furthermore equipped with an electric motor which can be operated both mechanically and generically 350 connected, which in turn on the input side with the DC voltage intermediate supply unit 110 connected is. In this embodiment, the in the capacitor assembly 150 stored energy can be used for propulsion support by the electric machine 350 is powered by a motor. Furthermore, energy can enter the capacitor arrangement 150 be recuperated when the electric machine 350 is operated as a generator.

In 4 an embodiment is shown in which the internal combustion engine 310 via a gearbox 420 on the one hand a hydraulic pump 430 in particular for the supply of working equipment, such as hydraulic cylinders or the like, with hydraulic fluid and on the other hand, as an alternator working electric machine 450 drives.

The drive itself is in 4 also carried out electrically by an inverter 130 is connected to the DC voltage intermediate circuit and designed as a motor electric machine 460 provided. The motor 460 in turn drives the drive axle 300 at. This embodiment is advantageous for providing an electric traction drive.

In 5 another embodiment is shown without an internal combustion engine. The power supply of the DC voltage supply unit 110 takes place in this case, in particular at a charging station to the capacitor assembly 150 charge. In operation, the in the capacitor arrangement 150 stored energy used to go through the inverter 130 the engine 460 which in turn is via the gearbox 420 the hydraulic pump 430 and the drive axle 310 drives. This embodiment is suitable for an emission-free purely electric driving and working operation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010025647 A1 [0002]
• DE 102010025648 A1 [0008]

Claims (15)

DC intermediate circuit comprising a DC intermediate circuit supply unit (110) and at least one of the DC DC link power supply unit supplied with DC capacitor arrangement (150) having a nominal voltage and a discharge voltage, which is greater than zero. DC voltage intermediate circuit after Claim 1 wherein the capacitor assembly (150) has at least 30% energy content at least 75% of the rated voltage. DC link according to one of the preceding claims, wherein the capacitor arrangement (150) is a capacitor bank. DC link according to one of the preceding claims, wherein the capacitor arrangement (150) comprises at least one hybrid capacitor. DC voltage intermediate circuit after Claim 4 wherein the at least one hybrid capacitor comprises - a dielectric material having the non-stoichiometric formula MeO _x where Me is a metal and x = 1, 2, 3, and / or - as an electrolyte an aqueous solution, and / or - as an activated carbon electrode and / or a hydrogen storage metal. DC voltage intermediate circuit after Claim 5 wherein the capacitor arrangement (150) has at least one hybrid capacitor of the form MeO _x / KOH / MeH-AC and / or of the form MeO _x / KOH / AC. DC intermediate circuit according to one of the preceding claims, wherein a switch (141) is adapted to a braking resistor (140) of the capacitor assembly (150) to connect in parallel when the voltage in the DC intermediate circuit exceeds the maximum allowable voltage. DC link circuit according to one of the preceding claims, wherein the DC voltage intermediate supply unit (110) is adapted to feed back energy into a supply network when the voltage in the DC voltage intermediate circuit is above the target voltage value and the charge level of the capacitor assembly (150) is at least 80% or at least 90%. A DC link as claimed in any one of the preceding claims, wherein the DC link power supply unit (110) is adapted to limit a current flowing therethrough to a nominal range having a nominal value and a tolerable tolerance. DC intermediate circuit according to one of the preceding claims, wherein a lithium / ion battery is connected in parallel with the capacitor arrangement (150). DC voltage intermediate circuit according to one of the preceding claims, wherein the DC voltage intermediate supply unit (110) is supplied from the mains side by a generator, in particular a vehicle generator. DC voltage intermediate circuit according to one of the preceding claims, wherein the generator is driven by an internal combustion engine. DC link according to one of the preceding claims, comprising an inverter (130) as a consumer. DC voltage intermediate circuit after Claim 13 wherein the inverter (130) drives an electric motor. A DC link according to any one of the preceding claims, wherein the DC link supply unit (110) is arranged to regulate the voltage in the DC link to a target voltage value corresponding to a charge level of the capacitor array (150) of at least 50% and at most 80%.

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