Arrangement and method for auxiliary voltage supply for power electronic converters

Abstract

The invention relates to an arrangement for auxiliary voltage supply for power electronic converters with a transformer having a transmitter with a primary side and a secondary side, wherein the primary side is designed with a first winding connected to a primary circuit of the transformer, and the secondary side is designed with a second winding connected to a secondary circuit of the transformer, wherein the secondary side of the transformer has a third winding arranged next to the second winding, in particular sharing the same coil core, which is arranged next to the second winding in such a way that it is inductively coupled to the first winding for voltage transmission, wherein the input of the third winding is connected to a first branch of a first rectifier and the output of the third winding is connected to a second branch of the first rectifier in such a way,that the rectifier ensures the provision of at least one auxiliary voltage. The invention relates, mutatis mutandis, to a method.

Description

[0001] The invention relates to an arrangement for the auxiliary voltage supply for power electronic converters according to the preamble of claim 1 and to a method for the auxiliary voltage supply for power electronic converters according to the preamble of claim 9.

[0002] It is known that converters feeding into an electrical grid must comply with grid guidelines, so-called grid codes, in order to obtain approval.

[0003] Grid codes are a set of guidelines in the form of technical regulations and standards established by energy utilities and grid operators to ensure the efficient and safe integration of electrical energy systems, including renewable energy sources, into the electrical grid. These codes are designed to ensure the stability, reliability, and security of the power grid. The term "grid" refers to the electrical network or power system. These guidelines vary from country to country and can differ depending on the specific characteristics of the respective power grid and regional requirements.

[0004] These guidelines generally include, among other things, that grid faults above a certain power level must not lead to disconnection from the grid.

[0005] It is also known that a rectifier (AC-DC converter) converts alternating current (AC) to direct current (DC), and that in some configurations, a rectifier may have an intermediate circuit in which an intermediate circuit voltage is present. This voltage can be used to provide an auxiliary power supply.

[0006] Since grid faults and short-term voltage outages must be bridged by the inverter according to the grid, AC / DC power supplies are no longer suitable for auxiliary supply, as they require a minimum grid voltage.

[0007] Until now, the problem was mainly solved by using a DC / DC converter in addition to the AC / DC power supply, which generated the auxiliary supply from the intermediate circuit voltage.

[0008] The object underlying the invention is therefore to provide a solution that at least partially overcomes the disadvantages of the prior art. In particular, the object is to provide a technical solution that improves the efficiency of power electronics converters.

[0009] This object is achieved by the arrangement for the auxiliary voltage supply for power electronic converters according to the preamble of claim 1, starting from the features of the preamble by its characterizing features, and by a method for the auxiliary voltage supply for power electronic converters according to the preamble of claim 9, starting from the features of the preamble by its characterizing features.

[0010] In the arrangement according to the invention for the auxiliary voltage supply for power electronic converters with a transformer having a transmitter with a primary side and a secondary side, wherein the primary side is designed with a first winding connected to a primary circuit of the transformer, and the secondary side is designed with a second winding connected to a secondary circuit of the transformer, the secondary side of the transformer has a third winding arranged next to the second winding, in particular sharing the same coil core, which is arranged next to the first winding in such a way that it is inductively coupled to the first winding for voltage transmission, wherein the input of the third winding is connected to a first branch of a first rectifier and the output of the third winding is connected to a second branch of the first rectifier in such a way,that the rectifier ensures the provision of at least one auxiliary voltage.,

[0011] This creates a power supply that enables the provision of an auxiliary voltage. Branching off from an existing transformer stage eliminates the need for a separate circuit. This also paves the way for further reductions, such as circuit complexity, dimensioning, and / or costs. It also paves the way for additional operating variants, such as bidirectional auxiliary voltage supply.

[0012] In the method according to the invention for the auxiliary voltage supply for power electronic converters with a transformer having a transmitter with a primary side and a secondary side, wherein the primary side is designed with a first winding connected to a primary circuit of the transformer, and the secondary side is designed with a second winding connected to a secondary circuit of the transformer, a third winding, which is arranged next to the second winding and in particular shares the same coil core, is arranged and operated on the secondary side of the transformer in such a way that it is inductively coupled to the first winding for voltage transmission, wherein the input of the third winding is connected to a first branch of a first rectifier and the output of the third winding is connected to a second branch of the first rectifier in such a way thatthat the rectifier ensures the provision of at least one auxiliary voltage.,

[0013] By proceeding or operating according to the method according to the invention, the advantageous properties of the circuit according to the invention are used to solve the problem and the advantages of the arrangement are fully realized.

[0014] Advantageous embodiments and further developments of the invention are specified by the subclaims.

[0015] In an advantageous development of the arrangement according to the invention, the third winding uses the same coil core as the second winding and has a smaller number of turns, in particular 1 to 2 turns, than the second winding. This enables a voltage supply with a low voltage value, which enables the provision of an auxiliary voltage. By using the same core, the inventive branching of a supply voltage from an existing transformer, a solution with minimal modification to conventional circuits is possible. Furthermore, a transformer is used which minimizes the wiring complexity of the modified transformer and optimizes the inductive coupling and efficiency. The low voltage is generally sufficient for the usage and circuit variants envisaged according to the invention.

[0016] For example, in a preferred embodiment of the arrangement according to the invention, it is further developed in such a way that a capacitor is connected in parallel at the output of the first rectifier. The capacitor is an output capacitor to which the rectified output voltage of the rectifier is applied. Among other things, it also has the advantage of smoothing the rectified voltage.

[0017] According to a further development of the arrangement according to the invention, the branches of the first rectifier are each formed by a diode. This ensures a simple implementation of the treatment of voltage pulses within the framework of rectification.

[0018] Alternatively or additionally, the arrangement according to the invention is advantageously further developed such that the branches of the first rectifier are formed by switches. This enables bidirectional operation, with the switches forming an inverter that applies voltage to the transformer. The semiconductors, which are generally located in the primary and secondary sides of the power electronic converter improved by the invention, then functionally form a rectifier. This allows, for example, intermediate circuit capacitors to be precharged for start-up, thus eliminating the need for an additional precharging circuit for an intermediate circuit containing the intermediate circuit capacitors.

[0019] In a further development of the arrangement according to the invention, this is preferably further developed in such a way that the switches are each formed by a parallel connection of a transistor, in particular one designed using MOSFET technology, and a diode. This results in increased efficiency and improved controllability, as well as additional degrees of freedom in the function of the switches. The diode can, among other things, absorb voltage spikes caused by induction.

[0020] Due to the advantageous development of the arrangement according to the invention such that the voltage regulator is connected to an auxiliary voltage bus which is designed to provide an auxiliary direct voltage fed by a battery and / or a second rectifier, wherein the second rectifier receives input signals via at least one phase of a power network providing alternating current and a neutral conductor, the voltage regulator can be used in particular for bidirectional operation and, if emergency power operation is required, a battery can additionally be connected to the auxiliary voltage bus. This can supply the control system and the auxiliary converter can be used to charge the intermediate circuit capacitors. Only then can the voltage required for the vehicle battery to be connected be generated on the vehicle side.Once this has been done, an island grid can be created for emergency power supply.

[0021] According to a further advantageous development of the arrangement according to the invention, an output of the voltage regulator is connected to a control device, in particular one that controls the power electronic converter, the first rectifier, the second rectifier, the voltage regulator, and / or the battery, in such a way that it supplies them with a supply voltage. A control device generally requires low DC voltage values, and supplying the control ensures an essential function. The voltage regulator ensures stable signals for one or more required voltages. Alternatively or additionally, it is also conceivable for other essential functional groups / circuits to be supplied by the voltage regulator.

[0022] Further advantages and details of the invention are explained with reference to the embodiment of the invention shown in the single figure. FIGURE shows a schematic circuit diagram of an embodiment of the arrangement according to the invention in the form of a multi-stage converter modified according to the invention and supplemented according to the invention with an auxiliary voltage supply circuit.

[0023] The exemplary embodiments and functions partly shown and partly only explained in the FIGURE below are a preferred embodiment and further developments of the arrangement according to the invention and the method according to the invention.

[0024] In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another, which also further develop the invention independently of one another and are therefore to be regarded as part of the invention individually or in a combination other than that shown.

[0025] Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0026] The FIGURE shows an exemplary embodiment of the arrangement according to the invention for supplying auxiliary voltage to a power electronic converter. The upper part of the FIGURE shows the power electronic converter (converter) UM, which is modified according to the invention and connected to additional circuit elements in such a way that the auxiliary voltage supply is ensured.

[0027] It can be seen that the converter has a multi-stage topology, as disclosed in the application by Siemens AG with the same seniority, entitled "Stationary DC charging device for electrically powered vehicles, method for providing a DC charging device for electrically powered vehicles" as the present application, Siemens file number 202400762. On the grid side, a typical 6-pulse rectifier circuit can be seen as the grid front end, which is connected to a three-phase AC voltage grid GRID via an AC FILTER filter. Therefore, the rectifier also has three branches or, for the six pulses, switches T1...T6, D1...D6, each of which is implemented as a pair consisting of a MOSFET transistor and a freewheeling diode, each of which is switched, i.e. can be controlled, by a driver signal S1...S6.

[0028] The output of this rectifier arrangement is a first smoothing capacitor Cdc_prim, to which the rectified first DC voltage is applied. This first DC voltage represents the input voltage of a second stage, which consists of a transformer circuit, which represents a DC-DC converter that generates a galvanically isolated second DC voltage from the first DC voltage and provides it at its output.

[0029] A typical topology is shown, centered around a transformer with primary and secondary circuitry. Two branches can be seen on the primary side, with two series-connected MOSFET transistors T7...T8, T9...T10, each forming a switch with a parallel-connected freewheeling diode D7...D8, D9...D10, each of which is switched by a driver signal S7...S10. The two branches are connected in parallel at the first smoothing capacitor Cdc_prim. A first coil L:Ls / 2 and a second coil L:Lm, as well as a primary-side capacitor C_prim, are connected between the junction points of the two series-connected switches T7...T8, T9...T10, D7...D8, D9...D10.

[0030] The second coil L:Lm is connected to the terminals of the primary winding of the transformer, i.e. parallel to its inductance.

[0031] On the secondary side, the inventive modification of the transformer can now be seen, which consists in the fact that on the secondary side there are two windings opposite the primary winding, so that the inductance of the primary side acts on both coils (windings). It can be seen that the upper of the two secondary-side windings has the typical topology of a transformer secondary side. The secondary side circuit is therefore constructed analogously to the primary side and thus has two branches, each with two series-connected MOSFET transistors T11...T12, T13...T14 and parallel freewheeling diodes D11...D14. It can be seen that between the connection points of the series-connected switches, a third coil L:Ls / 2 / n^2 is connected in series with the upper secondary-side winding of the carry and a secondary-side capacitance C_sec. The variable n represents the transformation ratio from the primary to the secondary side. By selecting n accordingly, the leakage inductance can be divided accordingly between the primary and secondary leakage inductance. This can, for example, be determined in a simulation in an optimized manner for a specific application.

[0032] Furthermore, it can be seen that, parallel to the series-connected switch branches T / D11...T / D12, T / D13...T / D14, the transformer output terminates with a second smoothing capacitor Cdc_sec connected in parallel. A second galvanically isolated DC voltage is applied to the capacitor. This second galvanically isolated DC voltage forms the input voltage of a third stage configured as two step-down converters connected in parallel. The third stage's task is to transform this second galvanically isolated DC voltage to a lower level, which is ultimately made available by this multi-stage converter to a load OUT. This load can be, for example, an electrically powered vehicle. The arrangement therefore represents a charger.

[0033] The invention is not limited to the exemplary embodiment. For example, it is applicable not only to the multi-stage topology. Rather, it is fundamentally applicable to all power electronic drivers that have a transformer that can be modified according to the invention.

[0034] The FIGURE further shows that a further rectifier circuit provided according to the invention is connected to the second secondary-side winding of the transformer, the output voltage of which is fed to a voltage regulator VOLTAGE REGULATOR so that the auxiliary voltage can be generated.

[0035] It can therefore be seen that the invention utilizes the existing transformer of the isolated DC-DC converter stage of the multi-stage converter UM by, on the one hand, applying an additional winding to it. On the other hand, an auxiliary voltage can be generated by the additional rectifier, which is supplied with voltage by the additional winding, and the subsequent voltage regulator. This allows sufficient energy to be supplied even in the event of a grid fault, so that essential functions, such as the control system, can be supplied in the event of grid problems. According to the exemplary embodiment, the rectifier and voltage regulator thus form an auxiliary voltage supply circuit HV, which is used for the auxiliary voltage supply according to the invention.

[0036] It is sufficient to branch off a low voltage for the additional rectifier or the auxiliary voltage supply circuit HV, so that the number of turns of the second secondary winding can generally be much smaller than the number of turns of the first secondary winding. For example, for the illustrated embodiment, one or two turns for the second secondary winding may be sufficient.

[0037] In principle, the rectifier can have the typical design using only diodes in the branches.

[0038] If the rectifier of the auxiliary voltage supply circuit is implemented with switches instead of diodes according to a further development of the invention, bidirectional operation is possible. Since the branches of the illustrated further rectifier are formed by switches S_aux_1...S_aux_4 connected in parallel with a diode and a MOSFET transistor, the illustrated embodiment is capable of providing such bidirectional operation. The operating mode in the opposite direction, as explained above, would therefore be that the branch through the second secondary-side coil L_aux does not feed the auxiliary voltage supply circuit HV, but rather the latter applies voltage to the secondary-side coil L_aux.

[0039] The switches S_aux_1...S_aux_4 of the additional rectifier functionally form an inverter, which applies this voltage to the transformer via the second secondary-side coil L_aux. The semiconductors of the primary and secondary sides of the main converter then functionally form rectifiers. This allows, for example, the intermediate circuit capacitors Cdc_prim and Cdc_sec to be precharged for start-up, thus eliminating the need for an additional precharging circuit for the intermediate circuit.

[0040] To supply power for use in this reverse direction, the VOLTAGE REGULATOR can be connected to an auxiliary voltage bus. The voltage present on the auxiliary voltage bus can be provided, as shown in the figure, by a third rectifier connected, for example, to a phase and neutral conductor of the AC grid. This third rectifier converts these pulses into a DC voltage of, for example, 24 V, which can then be tapped by circuits connected to the auxiliary voltage bus, such as the VOLTAGE REGULATOR.If the voltage regulator is operated in such a way that it taps it, then it generates the voltage for the transformer; if, on the other hand, it is operated in the other direction, the voltage branched off from the transformer is applied to the second rectifier and the voltage regulator VOLTAGE REGULATOR generates a low voltage in order to supply, for example, the control of the CONTROL circuits with a supply voltage, for example 3.3 V.

[0041] According to a further development of the invention, if emergency power operation is required, a 24V battery can also be connected to the auxiliary voltage bus. This allows the CONTROL controller to be supplied with power even in the event of a power failure, and the auxiliary voltage supply circuit HV according to the invention can now be used in battery mode to charge the intermediate circuit capacitors Cdc_prim and Cdc_sec.

[0042] In an application for charging an electric vehicle, the voltage required to connect the vehicle battery would only be generated in a first step on the vehicle side and, once this has been done, an island network for emergency power supply would be created in a second step.

[0043] An advantage of the inventive approach is that the auxiliary supply from the intermediate circuit of the multi-stage converter UM can be realized more cost-effectively, since components already existing in the multi-stage converter UM are reused.

[0044] In addition, the solution according to the invention can also be implemented bidirectionally with little effort, which enables emergency power operation; for example, the solution can be used to provide bidirectional charging stations for electric cars or DC-DC converters.

[0045] A further advantage is that the power electronic converter, such as the AC-DC power supply UM shown in the figure, can be smaller in size because it is only needed for starting from the mains. Furthermore, any precharging circuits for the intermediate circuit can be eliminated, since precharging can also be performed by the converter.

[0046] However, the invention is not limited to what has been described and illustrated. Rather, the exemplary embodiment represents only one of the many possible implementations of the inventive solution and method with regard to the design of the stages, for example, the type and polarity of the transistors and / or other circuit elements. These implementations may differ in circuit details, for example, according to dimensioning specifications and / or optimized for specific applications.For example, the MOSFET transistors could also be designed, in contrast to the circuit diagram, not entirely or partially as so-called enhanced n-channel MOSFET transistors as shown in the exemplary embodiment shown, but could be replaced entirely or partially by other electronic elements providing the switching function, which generally also leads to analogous adaptations of the other elements of the topology, which the person skilled in the art who intends to make such a change to the circuit can always take into account and easily carry out.

Claims

[1] Arrangement for auxiliary voltage supply for power electronic converters with a transformer which has a transmitter with a primary side and a secondary side, wherein the primary side is designed with a first winding connected to a primary circuit of the transformer, and the secondary side is designed with a second winding connected to a secondary circuit of the transformer, characterized bythat the secondary side of the transformer has a third winding which is arranged next to the second winding, in particular sharing the same coil core, and which is arranged next to it in such a way that it is inductively coupled to the first winding for voltage transmission, wherein the input of the third winding is connected to a first branch of a first rectifier and the output of the third winding is connected to a second branch of the first rectifier in such a way that the rectifier ensures the provision of at least one auxiliary voltage. [2] Arrangement according to the preceding claim, characterized by that the third winding uses the same coil core as the second winding and has a smaller number of turns, in particular 1 to 2 turns, than the second winding. [3] Arrangement according to one of the preceding claims, characterized bythat a capacitor is connected to the output of the first rectifier. [4] Arrangement according to one of the preceding claims, characterized by that the branches of the first rectifier are each formed by a diode. [5] Arrangement according to one of claims 1 to 3, characterized by that the branches of the first rectifier are formed by switches. [6] Arrangement according to the preceding claim, characterized by that the switches are each formed by a parallel connection of a transistor, in particular designed according to MOSFET technology, and a diode. [7] Arrangement according to one of the two preceding claims, characterized byin that the voltage regulator is connected to an auxiliary voltage bus which is designed to provide an auxiliary DC voltage which is fed by a battery and / or a second rectifier, the second rectifier receiving as input signals at least one phase of a power system providing an AC current and a neutral conductor. [8] Arrangement according to one of claims 3 to 7, characterized by that an output of the voltage regulator is connected to a control device, in particular controlling the power electronic converter, the first rectifier, the second rectifier, the voltage regulator and / or the battery, in such a way that it supplies them with a supply voltage. [9] Method for auxiliary voltage supply for power electronic converters with a transformer having a transmitter with a primary side and a secondary side, wherein the primary side is designed with a first winding connected to a primary circuit of the transformer, and the secondary side is designed with a second winding connected to a secondary circuit of the transformer, characterized bythat on the secondary side of the transformer, a third winding arranged next to the second winding, in particular sharing the same coil core, is mounted and operated in such a way that it is inductively coupled to the first winding for voltage transmission, wherein the input of the third winding is connected to a first branch of a first rectifier and the output of the third winding is connected to a second branch of the first rectifier in such a way that the rectifier ensures the provision of at least one auxiliary voltage.

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