POWER SUPPLY SYSTEM

A power supply system with a large number of battery modules, wherein each battery module has a first electrical connection and a second electrical connection, via which the battery modules are connected in series in an interconnection branch of the power supply system. Each battery module also has an accumulator which can be connected via a bridge circuit of the battery module to the first electrical connection and the second electrical connection, and to a charging path via which the power supply system can be charged, and to a discharging path via which the power supply system can deliver electrical power to a connected consumer. The power supply system has a switching component to which the charging path, the discharging path and the interconnection branch are connected, and wherein the switching component can connect the charging path and/or the discharging path electrically conductively to the interconnection branch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. 10 2021 111 861.1, filed on May 6, 2021, the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The disclosure relates to a power supply system. Combustion engines are predominantly used today for the mobile supply of high-performance machines and vehicles, particularly those with an output power of more than 1 kW. In order to reduce environmental pollution and health impairment due to exhaust gases and noise, such power supply systems are increasingly being replaced by those based on battery storage.

BACKGROUND

For many applications, it is advantageous if such a power supply system can provide an AC voltage. Consumers that are suitable for operation with a conventional mains AC voltage or electric motors such as 3-phase asynchronous machines are given as an example. Furthermore, it is desirable for high-power consumers to provide the highest possible supply voltage in order to keep required operating currents and thus also electrical losses small. An example of this is the Central European mains AC voltage of 230 V with a peak value of 325 V or the typical voltage of 400 V for mobile electric drives.

In order to generate an AC voltage from a DC voltage of a power supply system with battery storage, an electrical converter is required. So-called two- or three-point inverters are almost exclusively used here today, which generate a 1- or 3-phase, sinusoidal output voltage from an intermediate circuit voltage (battery voltage) by chopping and smoothing.

U.S. Pat. No. 3,867,643 A describes an alternative electrical converter in which multi-stage conversion takes place. A large number of direct current sources, for example batteries, are each periodically connected in series in the current path or bridged by a bridge circuit, so that the resulting output voltage assumes an approximately sinusoidal curve. Document U.S. Pat. No. 5,642,275 A details the implementation of this converter technology with battery modules, each battery module having at least one direct current source and a bridge circuit. Such converters are often referred to in the literature as “cascaded multilevel inverter/converter” or “modular multilevel inverter/converter”. Converters of this type have proven to be advantageous compared to two-point or three-point converters, particularly with regard to costs, thermal losses and size.

SUMMARY

It should be possible for such a power supply system both to provide electrical power to a consumer and to draw power from a supply network, for example. The disclosure is therefore based on providing a power supply system with a “cascaded multilevel inverter/converter” that can carry out both a charging process and a discharging process, and in which a change between the charging process and the discharging process can be easily accomplished.

This achieved by specifying the power supply system according to claim1. The subclaims relate to various advantageous developments of the present disclosure that are independent of one another, the features of which can be freely combined with one another by a person skilled in the art within the scope of what is technically reasonable. The disclosure relates to a power supply system with a large number of battery modules, wherein each battery module has a first electrical connection and a second electrical connection, via which the battery modules are connected in series in an interconnection branch of the power supply system, wherein each battery module also has an accumulator which can be connected via a bridge circuit of the battery module to the first electrical connection and the second electrical connection, and to a charging path via which the power supply system can be charged, and to a discharging path via which the power supply system can deliver electrical power to a connected consumer, wherein the power supply system has a switching means to which the charging path, the discharging path and the interconnection branch are connected, and wherein the switching means can connect the charging path and/or the discharging path electrically conductively to the interconnection branch.

Such a device can be charged directly from an AC voltage source and can also provide a consumer with electrical power in the form of AC voltage. It is possible to generate an AC voltage by means of a suitable control of the bridge circuits in the battery modules. Depending on the switching state of the switching means, the interconnection branch can be connected to the charging path and/or the discharging path in different ways. Such an interconnection can in principle take place in different modes, according to the disclosure a single-pole or dual-pole switchover between the charging path and the discharging path is conceivable. In principle, the bridge circuit can be any type of bridge circuit. According to the disclosure, the use of a half bridge, preferably a full bridge, is conceivable. With the help of the bridge circuit, it is preferably possible to connect the accumulator to the interconnection branch in different ways. It is thus conceivable according to the disclosure to connect the battery module with different polarities, or for the battery module to be bridged by means of the bridge circuit. In order to be able to control the bridge circuit in a suitable manner, the power supply system preferably has a control unit. The power supply system is preferably dimensioned to be quite compact. It is therefore preferably a portable/mobile power supply system that can be used variably, for example on construction sites, to provide electrical power.

It is preferred if the switching means selectively enables either the charging path or the discharging path to be connected to the interconnection branch. In other words, the switching means exclusively enables switching states in which all poles of the interconnection branch are connected either to the charging path or to the discharging path. Faults such as a connection of the charging path to the discharging path can thus be avoided. The switching means is particularly preferably designed in such a way that it galvanically separates the charging path from the discharging path at every operating time. This can be ensured by a suitable design of the switching means, which will be explained below.

It is advantageous if the switching means has at least one relay. A relay allows a remote-controlled change of a connection of the interconnection branch to the charging path or to the discharging path. In principle, the use of a wide variety of relay types is conceivable. It is particularly advantageous if the relay is a safety relay.

According to the disclosure, it can be provided that the power supply system has a locking circuit coupled to the at least one relay, which ensures that the charging path is separated from the interconnection branch when the at least one relay electrically conductively connects the discharging path to the interconnection branch, and which ensures that the discharging path is separated from the interconnection branch when the at least one relay electrically conductively connects the charging path to the interconnection branch. This ensures that the discharging path is galvanically isolated from the charging path at every operating time. To this end, the relays can have auxiliary contacts which are connected to one another in a suitable manner.

According to an advantageous embodiment of the disclosure, the switching means has two DPST relays with mirror contacts or one DPDT relay. A DPST relay only switches through in one switch position, while a DPDT relay switches through in both switch positions. Accordingly, DPST is defined as “Dual Pole, Single Throw” while DPDT stands for “Dual Pole, Double Throw”. Designing the DPST relays with mirror contacts allows the DPST relays to be coupled, which ensures that they cannot connect the connected charging path or discharging path to the interconnection branch at the same time. The DPDT relay should preferably be designed as a safety relay with two openers and two closers, which are connected to one another by means of forced guidance. In this way, galvanic isolation can also be ensured, for example, in the case of single-pole switching faults.

The power supply system preferably has no isolating converter circuit between the interconnection branch and the charging path or the discharging path. Coupling the interconnection branch to the charging path and/or to the discharging path by means of a converter circuit would also ensure galvanic isolation of the interconnection branch from the charging path or from the discharging path, but according to the disclosure this should be achieved using an advantageous alternative design. In the present case, a converter circuit is to be understood to mean a circuit comprising at least one transformer.

It can be provided according to the disclosure that the charging path and the discharging path each have two branches. A branch is to be understood here in each case as a current path. The two branches can be coupled via the switching means to a two-terminal network formed by the interconnection branch.

The power supply system is preferably equipped with an input filter in the charging path and with an output filter in the discharging path, wherein the input filter has a comparatively high total inductance and is designed for comparatively low currents, and wherein the output filter has a comparatively low total inductance and is designed for comparatively high currents. The total inductance of the respective filter is to be understood as the total inductance thereof, regardless of whether the filter is implemented by one component or by a plurality of components. In the present case, it is possible to dimension the input filter and the output filter differently for the requirements when charging the power supply system on a public supply network or delivering power via the discharging path. By dividing the filters, weight and installation space can be saved, since otherwise a filter with a high total inductance would be required in the interconnection branch, which would also have to be designed for a high current.

The input filter and the output filter are preferably designed in such a way that disturbance variables, which are caused, for example, by switching processes in bridge circuits of the mobile power supply system, are suppressed as well as possible. The wording that the input filter or the output filter is designed for a certain current is to be understood as meaning that such a current can be applied continuously to the input filter or the output filter without undesirable effects generally occurring. Thus, it should be possible to apply this current continuously, at least until the power supply device has been fully charged or discharged, without thermal damage to components and/or current paths occurring. This can also be understood in such a way that a permanent application of this current is possible at least until the power supply device is fully charged or discharged, and without an inductive component of the respective filter at its peak (peak current) losing more than 50% of its nominal inductance.

The input filter particularly preferably has a total inductance that is at least twice as great as the total inductance of the output filter, and the output filter is designed for a current that is at least twice as great as the current for which the input filter is designed. It is also advantageous if the input filter has a total inductance that is at least four times greater than a total inductance of the output filter, and the output filter is designed for a current that is at least four times greater than a current for which the input filter is designed. According to one variant of the disclosure, the input filter has a total inductance of at least 200 pH, preferably at least 400 pH, and is designed for a maximum current of at most 8 A, preferably at most 6 A, and the output filter has a total inductance of a maximum of 100 pH, preferably a maximum 50 pH and is designed for a maximum current of at least 12 A, preferably at least 16 A. A corresponding design would be advantageous with an operating voltage of 230 V. However, depending on the operating voltage and possibly other parameters, a different design of the filter can also be selected.

The input filter is preferably implemented in an LC configuration or an LCL configuration. The LC configuration is preferably formed by an inductive and a capacitive component, while the LCL configuration is formed by two inductive components and one capacitive component. According to the disclosure, it is possible for the output filter to be implemented in an LC configuration. The output filter can therefore have the same design as the input filter, although the components in the discharging path and in the charging path should have different dimensions.

According to a particular embodiment of the disclosure, the power supply system has an input filter in the charging path and an output filter in the discharging path, wherein the output filter is designed without an inductive component, and wherein at least one inductive component is connected upstream of the battery modules in the interconnection branch. In contrast, the input filter preferably has an inductive component in this embodiment. Capacitive components of the input filter and the output filter are preferably arranged exclusively in the charging path or the discharging path, but not in the interconnection branch. In this embodiment of the disclosure, the input filter and the output filter can, so to speak, share the inductive component in the interconnection branch. Thus, since the output filter in the discharging path has no inductive component at all and the inductive component of the input filter can be dimensioned to save space, space can be saved.

An EMC filter, which has a comparatively high filter inductance and a comparatively high filter capacitance and is designed for comparatively low currents, is preferably arranged in the charging path, and an EMC filter, which has a comparatively low filter inductance and a comparatively low or no filter capacitance and is designed for comparatively high currents, is arranged in the discharging path. The filter inductances of the EMC filters are preferably formed by current-compensated chokes. They are therefore particularly suitable for damping interference emissions and, in particular, for suppressing common-mode interference.

It is advantageous if the filter inductance of the EMC filter in the charging path is at least twice as great as the filter inductance of the EMC filter in the discharging path and the filter capacitance of the EMC filter in the charging path is at least twice as great as the filter capacitance of the EMC filter in the discharging path. According to a possible variant of the disclosure, the EMC filter in the discharging path has a current-compensated choke of at most 1.5 mH and optionally a connection-side capacitance of at most 1.0 μF, while the EMC filter in the charging path has a current-compensated choke of at least 3.0 mH and a terminal-side capacitance of at least 2.0 μF. On the connection side, that side of the EMC filter is arranged that faces the connections of the charging or discharging path, i.e. the connection of the charging path via which it can be connected to a supply network, for example, and the connection of the discharging path via which it can be connected, for example, to a consumer.

It is advantageous if the EMC filter in the discharging path is designed for a current that is at least twice as great, alternatively at least four times as great, as that of the EMC filter in the charging path. Preferably, the EMC filter in the discharging path is designed for a current of at least 18 A and the EMC filter in the charging path is designed for a current of at most 4.5 A. According to a further advantageous variant of the disclosure, the EMC filter in the discharging path is designed for a current of at least 15 A and the EMC filter in the charging path is designed for a current of at most 7.5 A. Due to their different design, the EMC filters better meet the requirements in the charging and discharging paths.

It is possible according to the disclosure for a current measuring device which is designed for a comparatively low maximum measured current to be arranged in the charging path and for a current measuring device which is designed for a comparatively high maximum measured current to be arranged in the discharging path. It is therefore not necessary to provide a common current measuring device in the interconnection branch which can measure both a comparatively high maximum measured current and a comparatively low measured current with sufficient accuracy. The maximum measured current is determined by the nominal measuring range of the respective current measuring device.

It is advantageous if the maximum measured current of the current measuring device in the discharging path is at least five times greater than the maximum measured current of the current measuring device in the charging path. It is particularly advantageous if the maximum measured current of the current measuring device in the discharging path is at least ten times greater than the maximum measured current of the current measuring device in the charging path. According to one embodiment of the disclosure, the maximum measured current of the current measuring device in the charging path can be at most 15 A, while the maximum measured current of the current measuring device in the discharging path is at least 75 A. According to a further embodiment of the disclosure, the maximum measured current of the current measuring device in the charging path is at most 10 A, while the maximum measured current of the current measuring device in the discharging path is at least 100 A.

It is also advantageous if a voltage measuring device is arranged in the interconnection branch. The voltage measuring device can be used to measure both a charging voltage and a voltage that the power supply system provides via the discharging path. Due to the generally comparable requirements for the voltage measuring device during the charging process and during the discharging process, preferably only this one voltage measuring device is provided in the power supply system. However, variants of the disclosure are also conceivable in which additional voltage measuring devices are used, which can be arranged, for example, in the charging path or in the discharging path.

According to a further variant of the disclosure, the power supply system is set up to check power supplied from an external power source via the charging path to the interconnection branch for at least one first fault characteristic and to switch off when the first fault characteristic is detected. This ensures that the power supply system is switched off in the event of faults during charging. It is possible according to the disclosure for the first fault characteristic to be selected from the group comprising the presence of an overcurrent, the presence of an overvoltage, a voltage rise rate being exceeded, a voltage drop rate being exceeded and a voltage frequency being exceeded or undershot. In principle, however, a check for the presence of other fault characteristics is also conceivable.

According to the disclosure, the power supply system can be set up to check for at least one second fault characteristic when electrical power is delivered via the discharging path, and to switch off when the second fault characteristic is detected. This ensures that the power supply system is switched off in the event of faults during discharging. It is preferred if the second fault characteristic is selected from the group comprising the presence of an overcurrent, the presence of an overload, the presence of a current reverse flow and the presence of an excessive reactive power. In principle, however, a check for the presence of other fault characteristics is also conceivable.

A rectifier bridge is preferably arranged in the charging path. In this way, it is possible to prevent the power supply system from feeding electrical power into a supply network, from which it is intended that electrical power should be drawn only in the event of a fault. It is also advantageous if at least one first overcurrent protection device is arranged in the charging path, wherein at least one second overcurrent protection device is arranged in the discharging path, and wherein a tripping current of the at least one second overcurrent protection device is at least twice as great as a tripping current of the at least one first overcurrent protection device. According to another variant of the disclosure, it can be provided that the tripping current of the first overcurrent protection device is at most 8 A and the tripping current of the second overcurrent protection device is at least 15 A. An overcurrent protection device within the meaning of this disclosure is to be understood as meaning an electrical fuse, in particular a circuit breaker or the like.

The power supply system is preferably designed in such a way that it allows the charging path to be electrically connected to the discharging path if the discharging path is not connected to the interconnection branch. Thus, in special cases, the charging path can be electrically conductively connected to the discharging path or the interconnection branch is bridged. This can be used, for example, to supply electrical power to a consumer connected to the power supply system via a supply network to which the power supply system is also connected. According to an advantageous embodiment of the disclosure, a switching device such as a relay can be provided to bridge the interconnection branch.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1is a schematic representation of a variant of the power supply system1according to the disclosure. The power supply system1has a charging path7and a discharging path8. The charging path7can be connected to a supply network, for example, so that the power supply system1can be charged. The supply network provides an AC voltage. The discharging path8can be connected to a consumer which can draw electrical power from the power supply system1via the discharging path8. The power supply system1can provide an AC voltage. A battery arrangement20of the power supply system1contains accumulators which are used to store electrical power. The accumulators are arranged in an interconnection branch10.

A switching means9which has two relays11can selectively connect the charging path7or the discharging path8to the interconnection branch10. The power supply system1also has a locking circuit12. This ensures that either the charging path7or the discharging path8is connected to the interconnection branch10at any time, but never both paths at the same time. Thus, a galvanic isolation between the charging path7and the discharging path8is always guaranteed.

The division into a charging path7and a discharging path8allows adapted dimensioning of various components. An input filter13is arranged in the charging path7and an output filter14is arranged in the discharging path8, and these filters are specially adapted to the respective requirements in the charging path7and in the discharging path8. The output filter14is designed without an inductive component21. In contrast, the input filter13has an inductive component21. In order to complement the filter effect of the input filter13and the output filter14, inductive components21assigned to them are arranged in the interconnection branch, these components being shared, so to speak, by the input filter13and the output filter14. Furthermore, the power supply system1also has EMC filters15in the charging path7and the discharging path8that are specially adapted to the requirements in the respective paths. The different dimensioning of components also affects current measuring devices16of the power supply system1, which are arranged in the charging path7and the discharging path8, respectively. The current measuring device16in the charging path7is designed for a comparatively low maximum measured current, and the current measuring device16in the discharging path8is designed for a comparatively high maximum measured current. On the other hand, regardless of whether the charging path7or the discharging path8is connected to the circuit branch10, a voltage measuring device17arranged in the interconnection branch10is used.

Furthermore, the power supply system1has a rectifier bridge18which is arranged in the charging path7. The rectifier bridge18can be used to prevent electrical power from flowing back into the supply network from the power supply system1via the charging path7. The power supply system1is also equipped with a switch22which is arranged in the charging path7and, if required, can disconnect the interconnection branch10from the supply network with little delay, for example in the event of voltage peaks or certain faults. A voltage directly at the supply network or at the consumer can be measured using additional voltage measuring devices23in the charging path7and the discharging path8.

FIG. 2shows a schematic representation of the battery arrangement20of the power supply system according toFIG. 1. A large number of battery modules2are arranged in the battery arrangement20. These are connected in series in the interconnection branch10. Each battery module2has a first electrical connection3and a second electrical connection4via which the relevant battery module2is connected to the interconnection branch10. A control unit24of the power supply system controls the battery modules2in a suitable manner during a discharging process, so that the total voltages thereof result in an approximately sinusoidal AC voltage. During a charging process, the control unit24controls the battery modules2in such a way that accumulators in the battery modules2are always connected to a voltage with the correct polarity and can therefore be charged.

FIG. 3is a schematic representation of one of the battery modules2of the battery arrangement according toFIG. 2. The battery module2has an accumulator5which can be electrically charged and discharged. The battery module2also has a bridge circuit6which is connected to the first electrical connection3and the second electrical connection4of the battery module2. The bridge circuit6can assume different switching states. For example, it can change a polarity with which the first electrical connection3and the second electrical connection4of the battery module2are connected to an inner branch25of the battery module2. The bridge circuit6can also bridge the inner branch25. A large number of battery modules2arranged in series can thus provide an AC voltage by a suitable change in the switching states. It is also possible to charge the accumulator5even though the charging path of the power supply system is connected to an AC voltage source. The battery module2also has an isolation device26. This isolates an interior of the battery module2galvanically from a control terminal27of the battery module2and contains an optocoupler for this purpose. Alternatively, a digital isolator could be used instead of the optocoupler.

A bridge controller19of the battery module2receives a signal generated by the control unit which indicates a desired switching state. This signal is fed to the bridge controller19from the control terminal27via the isolation device26. Depending on the signal, the bridge controller19controls the bridge circuit6in such a way that the switching state specified by the signal is set. A capacitor30is arranged in the inner branch25. A separating device31in the inner branch25makes it possible to separate the accumulator5from the inner branch25if necessary. Furthermore, a fuse32, which causes a disconnection of the accumulator5from the inner branch25in the event of an overcurrent, is provided in the inner branch25.

FIG. 4shows a schematic representation of the bridge circuit6of the battery module according toFIG. 3. This is a full bridge, which means that a particularly large number of switching states can be enabled. According to other embodiments of the disclosure, however, a half-bridge can also be used, for example.

FIG. 5shows a schematic representation of a second variant of the power supply system1according to the disclosure. A part of the power supply system1is shown, in which an interconnection branch10of the power supply system1can be coupled to a charging path7and to a discharging path8of the power supply system via a switching means9which has two relays11. The switching means9makes it possible to selectively connect either the charging path7or the discharging path8to the interconnection branch10. A switching relay28of the power supply system1makes it possible to connect the charging path7directly to the discharging path8. If a consumer is connected to the power supply system1and the power supply system1is also connected to a supply network, the consumer can be fed either by means of the battery modules of the power supply module or from the supply network. A switching controller29ensures that the switching means9and the switching relay28cannot assume any impermissible switching states.