Arrangement consisting of a power supply unit and at least one buffer module

Abstract

The invention relates to an arrangement consisting of a power supply unit (1) and at least one buffer module (10) having an electrical energy store (11), wherein the power supply unit (1) has an input-side rectifier (3), an input-side DC link (4) having a DC link capacitor, and an output-side DC-to-DC voltage converter (5), in a common housing, wherein the at least one buffer module (10) is arranged in a separate housing, is electrically connected to the power supply unit (1) and is used to buffer an output voltage of the power supply unit (1). The arrangement is distinguished by the fact that the buffer module (10) is coupled to the input-side DC link (4) of the power supply unit and, during operation, a DC link voltage of the DC link (4) of the power supply unit is applied to said buffer module.

Description

[0001] Arrangement of a power supply and at least one buffer module

[0002] The invention relates to an arrangement comprising a power supply and at least one buffer module with an electrical energy storage device. The power supply comprises an input-side rectifier, an input-side intermediate circuit with an intermediate circuit capacitor, and an output-side DC-DC converter in a common housing. The buffer module is arranged in an external housing and electrically connected to the power supply and serves to buffer an output voltage of the power supply.

[0003] Power supplies of the type described, also known as switching power supplies, are widely used to operate DC-powered devices from an AC power supply. Particularly in industrial applications, it is often required to be able to absorb (“buffer”) at least short interruptions in the mains voltage so that connected devices are not affected by this short-term power interruption. For cost reasons and to limit the space and weight of a power supply, internal energy storage devices in the power supply are usually only available in a size that allows buffer times in the range of a few milliseconds to several tens of milliseconds.

[0004] To increase buffer times when needed, it is common practice to connect external buffer modules in parallel on the output side of the power supply. These modules contain, for example, capacitors or rechargeable batteries as energy storage devices. To enable use with different power supplies and different output voltages, or even with power supplies with adjustable output voltages, such buffer modules generally have their own DC-DC converter. In addition, when using a capacitor as an energy storage device in the buffer module, a DC-DC converter is always required to adapt the capacitor voltage, which changes with decreasing charge, to the DC voltage at the power supply output, which must be kept constant. The design of the buffer modules is therefore complex both electrically and in terms of cost.

[0005] Siemens offers a power supply system known as the "SITOP PSU8600" in which a basic unit – the actual power supply – can be coupled with external modules that increase the buffer time in the event of a power failure. The power supply has a three-stage design and includes an input-side rectifier (first converter stage), an input-side intermediate circuit, and two series-connected DC-DC converters (second and third converter stages). The two DC-DC converters are coupled via an additional intermediate circuit. The external modules can contain capacitors or batteries that are connected in parallel with the additional intermediate circuit of the power supply on the output side.Such a power supply can advantageously be supplemented with a desired buffer capacity depending on the application, whereby the second, output-side DC-DC converter is advantageously used to provide a constant DC voltage at the output of the power supply even when the voltage of the buffer module changes with discharge.

[0006] It is an object of the present invention to provide an arrangement comprising a power supply and at least one buffer module with an energy storage device, in which the buffer module can also be used without an additional DC-DC converter to provide a constant output voltage and which can also be used in conjunction with a power supply that does not have a three-stage structure with two DC-DC converters.

[0007] This object is achieved by an arrangement having the features of independent claim 1. Advantageous further developments and embodiments are the subject of the dependent claims.

[0008] An arrangement according to the invention of the type mentioned at the outset is characterized in that the buffer module is coupled to the input-side intermediate circuit of the power supply and, during operation, is supplied with an intermediate circuit voltage of the input-side intermediate circuit of the power supply.

[0009] Unlike prior art, in the arrangement according to the invention, the buffer module is not coupled to the power supply on the output side or to the additional output-side intermediate circuit, but is electrically connected to the input-side intermediate circuit of the power supply. Accordingly, the buffer module operates with the input-side intermediate circuit voltage, which is essentially independent of the output voltage of the power supply. The input-side intermediate circuit voltage is generally determined only by the mains voltage, the number of mains phases used (single-phase versus three-phase power supply), and any power factor correction filter (PFC).Within a country or region, the mains voltage is constant, so that many different types of power supplies, regardless of their output voltage, have comparable intermediate circuit voltages, to which the energy storage device can then be matched in its dielectric strength.

[0010] At the mains voltage of 230 volts (V) typical in Europe, the input-side intermediate circuit voltage after rectification of the mains voltage is approximately 325 V (slightly higher for power supplies with power factor correction filters). It has been shown that capacitors, particularly electrolytic capacitors, suitable for this voltage range, i.e., capacitors with a dielectric strength of approximately 380-450 V, have a particularly low energy-specific volume, i.e., they have a particularly high maximum energy density. For a given buffer storage volume, a longer buffer time can be achieved than when using capacitors with a lower dielectric strength connected in parallel to the output-side intermediate circuit or the output voltage.

[0011] In an advantageous embodiment of the arrangement, the energy storage device of the at least one buffer module is at least one capacitor and / or at least one rechargeable battery. Capacitors can be charged and discharged quickly and are low-maintenance. They are particularly suitable as short-term buffer storage devices. Due to their high capacity, rechargeable batteries can also be used to buffer longer power outages.

[0012] In an advantageous embodiment of the arrangement, a connection between the power supply and the at least one buffer module comprises a power bus. Advantageously, the at least one buffer module has a switching unit via which the energy storage device is connected to the power bus, allowing the connection between the power supply and the energy storage device to be controlled. For this purpose, the switching unit can have at least one semiconductor switching element for coupling the energy storage device to the power bus or for disconnecting it from it. Furthermore, different current paths for charging and discharging the energy storage device are preferably provided.

[0013] By controlling the switching device accordingly, the charging voltage for the energy storage device can be limited to a specified maximum value. Furthermore, current peaks that could otherwise occur, for example, when a buffer module is connected to a power supply during operation, can be prevented. Ripple currents can also be reduced, which has a positive effect on the service life of the energy storage device.

[0014] In a further advantageous embodiment, the arrangement between the power supply and the at least one buffer module comprises a data and / or signal bus. Preferably, the at least one buffer module has a control unit that is coupled to the data and / or signal bus and controls the switching unit. Information can be exchanged between the power supply and the at least one buffer module via the data and / or signal bus, which can be used to optimize the use of the at least one buffer module.

[0015] In a further advantageous embodiment of the arrangement, the control unit is configured to control at least one semiconductor switching element of the switching unit using a pulse-width modulation method. Preferably, the control unit is configured to regulate a charging and / or discharging current of the energy storage device. In this way, for example, the aforementioned limitations of the charging voltage and / or charging current for the energy storage device can be implemented.

[0016] In a further advantageous embodiment of the arrangement, the control unit is configured to transmit information about the at least one buffer module via the data and / or signal bus to the power supply and / or a higher-level controller. The transmitted information can, for example, be status information about the condition (operating condition, aging condition, etc.) of the energy storage device and / or the switching unit. The power supply can then advantageously adapt the use of the buffer module to its condition.

[0017] In a further advantageous embodiment of the arrangement, the at least one buffer module has options for connecting another buffer module. This allows buffer modules to be chained together, and the buffer capacity can be increased simply by adding additional buffer modules. Due to the chaining, only one connection option for a buffer module is required on the power supply itself.

[0018] The invention is explained in more detail below using an exemplary embodiment with the aid of three figures. The figures show: Fig. 1 is a schematic block diagram of an arrangement comprising a power supply and two buffer modules;

[0019] Fig. 2 is a more detailed schematic block diagram of one of the buffer modules according to Fig. 1; and

[0020] Fig. 3 is a schematic circuit diagram of a switching unit of the buffer module according to Fig. 2.

[0021] Fig. 1 shows a block diagram of a power supply unit 1 with, as an example, two buffer modules 10 connected.

[0022] The power supply unit 1 has an AC input 2, which allows it to be connected to an AC power supply network during operation. The AC input 2 can be single-phase, i.e., with two conductors, or three-phase, with three conductors and, if necessary, a neutral conductor.

[0023] In the power supply 1, the AC voltage from the AC input 2 is fed to a rectifier 3, also called an AC / DC converter (AC - Alternating Current; DC - Direct Current). The rectifier 3 can be purely passive and consist of only a diode arrangement. Typically, the rectifier 3 has actively controlled switching elements to reduce distortion reactive power and thus disruptive harmonics in the grid. This is known as a power factor correction filter (PFC).

[0024] At the output of rectifier 3, an intermediate circuit 4 is arranged, which essentially comprises one or more intermediate circuit capacitors connected in parallel. Downstream of intermediate circuit 4 is a DC / DC converter 5, also called a "DC / DC converter," which converts the intermediate circuit voltage into a DC voltage of the desired level, which is provided at an output 6 of power supply 1 to supply loads. With rectifier 3 (AC / DC converter) and DC / DC converter 5 (DC / DC converter), power supply 1 thus has a two-stage design.

[0025] When using a passive rectifier, the level of the intermediate circuit voltage depends on the mains voltage and, for example, is approximately 325 V for a single-phase power supply supplied with 230 V AC. Power supplies are generally designed for lower output voltages at the DC voltage output 6, so a DC-DC converter 5, possibly with galvanic isolation and a step-down effect, in the simplest case a step-down converter, is used. Such a step-down converter loads its input with a pulsed input current. The intermediate circuit 4 with its intermediate circuit capacitors is used to provide this pulsed current regardless of the current phase position of the mains voltage supplied at the AC voltage input 2.

[0026] The components of the power supply 1 , in particular the DC-DC converter

[0027] 5 and the PFC stage of the rectifier 3 are controlled and monitored by a power supply controller 7.

[0028] In addition to the AC input 2 and the DC output

[0029] 6, a power bus 8 and optionally also a data and / or signal bus 9 are led out of the housing of the power supply 1, to which a first of the buffer modules 10 is connected. As indicated by the capacitor symbol on the buffer module 10, the buffer module 10 has an energy storage device that is connected to the intermediate circuit 4 via the power bus 8. For example, the energy storage device of the buffer module 10 can be a capacitor or an arrangement of several capacitors that are connected in parallel to the capacitor of the intermediate circuit 4 via the power bus 8. In this case, the power bus 8 is formed by two lines with corresponding current-carrying capacity.

[0030] Connectors are preferably provided on the power supply 1 and / or on the buffer module 10, so that the power bus 8 and the data and / or signal bus 9 can be easily connected or disconnected. Due to the high voltages involved, the power bus 8 in particular requires appropriate insulation strength and contact protection. The data and / or signal bus 9 can be used to control the buffer module 10 or its connection to the power supply 1, as will be explained in more detail below in connection with Fig. 2.

[0031] As a special type of connector, so-called cross-connectors can also be used, especially when the power supply unit 1 and buffer module 10 are designed as devices that can be snapped onto a mounting rail next to each other. The cross-connectors are then inserted in the form of plug-in elements, bridging the gaps, into adjacent insertion openings in the housings of the power supply unit 1 and buffer module 10. In this case, appropriate dielectric strength of the insulation and contact protection are also provided.

[0032] As shown in the example of Fig. 1, it can be provided that the power bus 8 and the data and / or signal bus 9 are passed on from the first buffer module 10, for example also in the form of connectors, as are also found on the power supply 1, so that one or more further buffer modules 10 can be connected in series as required. By way of example, a continuous data and / or signal bus 9 is shown in Fig. 1. However, it is also conceivable for a point-to-point connection between adjacent devices to be implemented in the data and / or signal bus 9.

[0033] Both the power supply unit 1 and the buffer modules 10 can be arranged in housings designed for snapping onto a mounting rail. Alternatively or additionally, mounting means can be provided for direct mounting, e.g., on a mounting plate.

[0034] Fig. 2 shows a possible structure of one of the buffer modules 10 according to Fig. 1 in more detail. It comprises an energy storage device 11 as already mentioned, for example one or more capacitors, in particular electrolytic capacitors. In further embodiments, rechargeable batteries and / or so-called high-capacity “super caps” or “gold caps” can be used as energy storage devices alternatively or additionally. The energy storage device 11 is connected to the energy bus 8 via a switching unit 12. The switching unit 12 can, for example, comprise semiconductor switches or a relay in order to connect the energy storage device 11 to the energy bus 8 in a selective and controlled manner. An embodiment of a switching unit 12 is shown in Fig. 3 and is explained in more detail below. For control purposes, a control unit 13 is provided which receives control signals or control data from the data and / or signal bus 9. Furthermore, parameters can be received from the power supply unit 1 orParameters are transmitted to the buffer module(s) 10 from its power supply controller 7 and, if applicable, a higher-level controller in order to adjust its operating behavior. Alternatively or additionally, information for controlling the buffer module can be derived from a voltage state of the power bus 8. In addition, it can be provided that status information, for example, about the state (operating state, environmental parameters, e.g., temperature, aging state, etc.) of the energy storage device 11 and / or the switching unit 12, is transmitted to the power supply 1 or its power supply controller 7 and, if applicable, additionally to a higher-level controller.

[0035] The switching unit 12 can be used to decouple the energy storage device 11 from the energy bus 8, for example, when there is no connection to a power supply unit 1. This prevents a high operating voltage of the energy storage device 11 from being present on the energy bus 8 while its connections are open because they are not connected to the power supply unit 1. Furthermore, this prevents high compensating currents from flowing directly between the intermediate circuit 4 and the energy storage device 11 when the buffer module 10 is connected to the power supply unit 1 if they are charged to different voltages. For example, it can be provided that a connection is only made when the intermediate circuit 4 and the energy storage device 11 both have essentially the same voltage, for example when both are discharged.

[0036] In particular, if the switching unit 12 has a semiconductor switch as a switching element, it can also be provided to regulate a charging or discharging current of the energy storage device 11, in particular after connecting the buffer module 10 to the power supply 1, and in particular to reduce it so that excessive charging or discharging currents do not flow. The maximum level of a charging or discharging current represents, for example, a parameter that can be transmitted by the power supply 1 or its power supply controller 7 or a higher-level controller to the buffer module(s) 10.

[0037] The control of the charging and discharging currents can be achieved, for example, by a corresponding pulse-width modulation of the switching element of the switching unit 12. In a further embodiment, the switching unit 12 can also be provided with a discharge option for the energy storage device 11, for example, to discharge it before disconnecting it for safety reasons.

[0038] Furthermore, the switching module 12 can be advantageously used to switch on the energy storage device 11 only when the power supply 1 signals a corresponding need. The number of charging and discharging cycles as well as the ripple current load on the energy storage device 11 can thus be reduced, thereby increasing its service life.

[0039] The aforementioned functions can be controlled by the control unit 13, if necessary in communication with the power supply controller 7. Furthermore, monitoring functionalities can be implemented in the control unit 13, for example, to determine the state of charge, for example the charging voltage, of the energy storage device 11 and to display it on the buffer module 10 via a corresponding signaling unit and / or to transmit it to the power supply 1 via the data and / or signal bus 9. Furthermore, the control unit 13 can be provided with an operating time or charging cycle recording function for the energy storage device 11, since this information provides information about the aging state of the energy storage device 11, which is useful with regard to operational reliability and / or predictive maintenance. A metrological determination of the aging state is also possible in this way.

[0040] The coupling of the energy storage device 11 to the intermediate circuit 4 has the advantage that a falling voltage of the energy storage device 11 during discharging does not need to be compensated by an additional DC / DC converter, but is, so to speak, inherently compensated by the DC / DC converter 5 of the power supply 1. A further advantage is that energy flowing back from the output 6 via the DC / DC converter 5, which can occur, for example, when motors are connected to the power supply 1 in a generator mode and the DC / DC converter 5 of the power supply 1 can operate bidirectionally, can be absorbed by the energy storage device 11 and does not need to be converted into heat energy. This requires a corresponding dielectric strength of the intermediate circuit that is above the nominal intermediate circuit voltage.

[0041] Figure 3 schematically shows an advantageous embodiment of a switching unit 12 together with an energy storage device 11, as can be used, for example, in the buffer module 10 shown in Figure 2.

[0042] The switching unit 10 is connected to the energy bus 8 via terminals 121. In the example shown, the energy storage device 11 is designed as a capacitor and is also referred to below as capacitor 11.

[0043] A special feature of the switching unit 12 shown in Figure 3 lies in two different current paths between the capacitor 11 and the power bus 8, wherein a first current path is designed for the defined charging of the capacitor 11 and a second current path is designed for the defined discharging of the capacitor 11. The first path comprises a series circuit consisting of a diode 122, a semiconductor switching element 123, and a coil 124. In addition, a freewheeling diode 125 is arranged in parallel with the series circuit consisting of coil 124 and capacitor 11. In this way, a controllable step-down converter is formed when the semiconductor switching element 123 is controlled in a clocked manner. A MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), for example, can be used as the semiconductor switching element 123.

[0044] By appropriately controlling semiconductor switching element 123, a charging voltage for capacitor 11 can be limited to a predetermined maximum value. Furthermore, current spikes can be prevented that could otherwise occur, for example, when a buffer module 10 is connected to a power supply 1 during operation. Ripple currents can also be reduced with the help of the step-down converter, which increases the service life of capacitor 11. Since charging of capacitor 11 can be controlled with comparatively low currents, the aforementioned components of the first path do not need to be designed for high power, which makes them cost-effective.

[0045] A semiconductor switching element 126 and a diode 127 are also arranged in the second current path, which serves for discharging. The semiconductor switching element 126 can, for example, again be a MOSFET or an IGBT. Advantageously, the semiconductor switching element 126 is designed to transmit a higher current in order to be able to provide a potentially required high current of the power supply 1 in the buffer mode.

[0046] The semiconductor switching element 126 enables a defined release of the energy stored in the capacitor 11. The current directions in the charging path and the discharging path are defined by the two diodes 122 and 127. The diode 122 prevents unwanted discharging if the voltage to which the capacitor 11 is charged is greater than the voltage applied to the terminals 121. Conversely, the diode 127 prevents unwanted or uncontrolled charging of the capacitor 11. A further advantage of the separate charging and discharging paths is that the energy does not have to be transferred back from the capacitor 11 via the coil 124, which could potentially lead to overshoots and would require a low internal resistance for the coil 124 and thus a larger wire cross-section.As an alternative to using a controllable buck converter, a linear regulator could also be used to limit the charging of capacitor 11 to a defined voltage. The advantage of this is that less electromagnetic pollution occurs because there is no clocked semiconductor switching element. The disadvantage is increased power loss in the linear regulator.

[0047] List of reference symbols

[0048] 1 power supply

[0049] 2 AC inputs

[0050] 3 rectifiers (AC / DC converters)

[0051] 4 intermediate circuit

[0052] 5 DC-DC converters (DC / DC converters)

[0053] 6 DC output

[0054] 7 Power supply control

[0055] 8 Energy bus

[0056] 9 Data and / or signal bus

[0057] 10 Buffer module

[0058] 11 Energy storage (capacitor)

[0059] 12 Switching unit

[0060] 121 connection

[0061] 122 Diode

[0062] 123 Semiconductor switching device

[0063] 124 coil

[0064] 125 Diode

[0065] 126 semiconductor switching device

[0066] 127 Diode

[0067] 13 Control unit

Claims

Claims 1. Arrangement comprising a power supply unit (1) and at least one buffer module (10) with an electrical energy store (11), wherein the power supply unit (1) has, in a common housing, an input-side rectifier (3), an input-side intermediate circuit (4) with an intermediate circuit capacitor, and an output-side DC-DC converter (5), wherein the at least one buffer module (10) is arranged in a separate housing and is electrically connected to the power supply unit (1) and serves to buffer an output voltage of the power supply unit (1), characterized in that the buffer module (10) is coupled to the input-side intermediate circuit (4) of the power supply unit and, during operation, is supplied with an intermediate circuit voltage of the intermediate circuit (4) of the power supply unit.

2. Arrangement according to claim 1, wherein the energy storage device (11) of the at least one buffer module (10) is at least one capacitor and / or at least one rechargeable battery.

3. Arrangement according to claim 1 or 2, wherein a connection between the power supply (1) and the at least one buffer module (10) comprises a power bus (8).

4. Arrangement according to claim 3, wherein the at least one buffer module (10) has a switching unit (12) via which the energy store (11) is connected to the energy bus (8).

5. Arrangement according to claim 4, wherein the switching unit (12) has at least one semiconductor switching element (123, 126) in order to couple the energy storage device (11) to the energy bus (8) or to separate it from it.

6. Arrangement according to claim 4 or 5, wherein the switching unit (12) has different current paths for charging and discharging the energy storage device (11 ).

7. Arrangement according to one of claims 3 to 6, wherein the connection between the power supply (1) and the at least one buffer module (10) comprises a data and / or signal bus (9).

8. Arrangement according to claim 4 and 7, wherein the at least one buffer module (10) has a control unit (13) which is coupled to the data and / or signal bus (9) and controls the switching unit (12).

9. Arrangement according to claim 8, wherein the control unit (13) is designed to control at least one semiconductor switching element (123) of the switching unit (12) in a pulse width modulation method.

10. Arrangement according to claim 9, wherein the control unit (13) is configured to regulate a charging and / or discharging current of the energy storage device (11). 11 . Arrangement according to one of claims 8 to 10, wherein the control unit (13) is designed to transmit information about the at least one buffer module (10) to the power supply unit (1) via the data and / or signal bus (9).

12. Arrangement according to one of claims 1 to 11, wherein the at least one buffer module (10) has possibilities for connecting a further buffer module (10).

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