High-voltage DC / DC converter for charging an electric vehicle and operating procedure for the converter

Abstract

A method for operating a high-voltage DC-DC converter (1) comprising an intermediate circuit (15) which is coupled via a respective converter stage (14) to at least one vehicle connection (12) for an electrically powered motor vehicle (4) as the device (D) to be supplied, to at least one storage connection (6) for an electrical energy storage device (2) as the device (D) to be supplied, and to at least one source connection (10) for a renewable energy source (3) as the device (D) to be supplied, wherein in the method a control unit (16) for transmitting (7, 11, 13) electrical energy between at least two of the connections (6, 10, 12) controls the respective converter stages (14) of the connections (6, 10, 12), characterized in that a communication interface (8) is provided for each connection (6, 10, 12) and the control unit (16) can be accessed from each connection (6, 10, 12) 10,12) connected device (D) balance data (17), which includes at least one of the following details of the device (D): , Specifies energy demand, power demand, energy supply, and capacity, receives and sets an energy quantity and transmission direction of the electrical energy transferred between the terminals (6, 10, 12) such that an energy balance of the energy exchanged between the devices (D) satisfies a balancing criterion (18) determined on the basis of the balance data (17), wherein the connected energy storage device (2) has a power converter unit (23) through which the energy storage device (2) indirectly obtains additional energy by the energy balance is balanced via the power converter unit (23), via which the energy storage unit (2) is coupled to a building network (24) of a building (5) which is operated on an alternating current basis, and the building network (24) is coupled to a public supply network (25), with which balancing energy (26) is exchanged to balance the energy balance of the control device (16).

Description

[0001] The invention relates to a method for operating a high-voltage DC-DC converter, via which an electrically powered motor vehicle can be coupled with a renewable energy source and an electrical energy storage device in order to exchange electrical energy between these devices. The invention also includes the high-voltage DC-DC converter, which has corresponding connections for connecting the aforementioned devices.

[0002] A DC-DC converter of the type described is known, for example, from US 2015 / 0061569A1 and US 2008 / 0013351A1. According to these patents, the terminals in question are each coupled to a DC link of the DC-DC converter via a converter stage, so that only two converter stages are involved in the transfer of electrical energy between two terminals. An inductor is provided for intermediate energy storage in the DC link. A Modbus interface is used to configure the operating characteristics of the DC-DC converter, allowing the control registers of the converter to be set. Depending on the register values, the direction and amount of electrical energy transferred in the converter stages are determined.A disadvantage of this voltage converter is that the electrical energy transfer is configured relatively rigidly, with register values ​​being set and the voltage converter then continuously behaving according to these set register values. If there is a change in the electrical energy demand or availability of a device, for example, because a connected solar panel can provide a different output power, this is only taken into account if the register values ​​are readjusted via Modbus.

[0003] US Patent 6,370,050 B1 discloses a power converter that couples two converter stages via a DC link. An inductor is also provided in the DC link to store energy. The electrical voltage at the converter's outputs is set to determine the direction of energy flow. A connected device thus only draws electrical energy if its input voltage is lower than the voltage applied at the terminal. Similarly, energy flows from the device to the terminal only if the device generates a higher output voltage. A disadvantage of this passive control of the energy flow direction is that it can only control the current energy flow and does not allow for predictive energy transfer.

[0004] German patent DE 10 2013 019 373 A1 discloses a stationary system for recycling traction batteries, in which the traction batteries are used as energy storage devices to operate other system components. To control the energy flow, an intermediate circuit with voltage converters is provided, which are controlled depending on energy values ​​to balance the power supply between the system components. To determine the necessary performance data, the system components are monitored by means of monitoring lines to determine when one of the connected devices is switched on or off.

[0005] WO 2013 / 039 753 A1 discloses an energy management system for charging an electric vehicle. Energy sources that can be connected include solar cells, a wind turbine, an electrical grid, and other sources, with the energy flow between the respective connections controlled by a master controller.

[0006] US Patent 9,153,847 B2 discloses a solar charging station for a motor vehicle. The energy transfer can be configured by a user via a user interface. Additionally, it is possible to consider other external conditions that should also influence the energy transfer.

[0007] The invention is based on the objective of enabling a predictive and flexible energy transfer between at least one electrically powered motor vehicle, at least one vehicle-external electrical energy storage device and at least one renewable energy source.

[0008] The problem is solved by the subject matter of the independent patent claims. Advantageous further developments of the invention are given by the features of the dependent patent claims.

[0009] The invention provides a method for operating a high-voltage DC-DC converter. In the context of the invention, "high voltage" refers to an electrical voltage greater than 60 volts. The method is based on a high-voltage DC-DC converter, or simply DC-DC converter, which has an intermediate circuit. This intermediate circuit is coupled via a respective converter stage to at least one vehicle connection for an electrically powered vehicle, at least one storage connection for an electrical energy storage device (e.g., a high-voltage battery), and at least one source connection for a renewable energy source.In the context of the invention, a converter stage is understood to be a DC-DC converter unit that can convert the voltage value of the DC voltage provided in the intermediate circuit into a DC voltage to be provided at the respective terminal and / or can convert the voltage value of an electrical voltage applied at the terminal into the electrical voltage in the intermediate circuit. A converter stage can, for example, include a boost converter and / or a buck converter.

[0010] In the following, a device connected to one of the terminals is referred to as a device to be supplied. In the case of the vehicle terminal, this device could be a motor vehicle; in the case of the storage terminal, an energy storage device; and in the case of the source terminal, a renewable energy source. The procedure involves a control unit of the high-voltage DC / DC converter controlling the respective converter stages of the terminals in order to transfer electrical energy between at least two of the terminals.

[0011] To ensure that this transmission of electrical energy is predictive and demand-driven, the method according to the invention provides that a communication interface is available for each connection and that the control unit receives balance data from each device connected to a respective connection. In the context of the invention, balance data specifies at least one of the following aspects of the device: its energy demand, its power demand, its energy reserve, or its capacity. "Capacity" refers to the electrical power that the device can deliver or provide.

[0012] The control unit sets the amount and direction of electrical energy transferred between the terminals such that the energy balance of the energy exchanged between the devices meets a balancing criterion. This balancing criterion is determined based on the balance data. In other words, the control unit balances the energy demand and / or power demand of at least one of the connected devices with the energy supply and / or capacity of at least one other connected device, if possible. The direction of energy flow can be set, for example, in a known manner by generating a corresponding voltage value at the respective terminals, so that electrical energy flows either from the terminal to the connected device or vice versa.

[0013] The invention offers the advantage that the voltage values ​​at the electrical connections can be precisely adjusted so that energy and / or power is transferred between devices as needed. This also allows, for example, a vehicle's traction battery to be used proactively, contrary to initial expectations, not for charging, but as an energy source to charge an energy storage system in a building. Accordingly, the vehicle can signal its energy reserves and / or performance capacity through its energy balance data.Similarly, an energy storage system provided in the building may be fully charged, but its balance data may indicate that it has no available energy supply and / or performance capacity because the energy stored in the energy storage system is needed within the building and therefore cannot be supplied to the motor vehicle.

[0014] The communication interface and the balance data transmitted via it allow the energy flow to be specifically adjusted to the demand, supply, or capacity of individual devices, regardless of current electrical conditions. This eliminates the need for complex coordination between the devices; each device can signal its own status through its balance data. The DC-DC converter's control unit then coordinates the devices accordingly.

[0015] One way to balance the energy supply is to compensate for any discrepancies in the overall energy balance of the devices, resulting in an energy deficit or surplus. Typically, an AC-DC converter or a power converter unit is connected to the intermediate circuit to connect to an AC power supply network. To meet the balancing criterion, the control unit balances the energy balance via the power converter unit using the AC power supply network. This allows excess electrical energy, such as that supplied by a renewable energy source, to be fed into the grid, or a shortfall in electrical energy to be drawn from the grid. As an alternative to a dedicated power converter unit, the invention provides for a connected energy storage device to have a power converter unit through which the energy storage device can indirectly draw additional energy.

[0016] An energy balance is maintained via a DC / AC converter, through which the energy storage system is connected to the building's electrical network, which can operate on alternating current (e.g., 230 volts, 50 hertz). The building's electrical network is connected to a public grid, allowing for the exchange of balancing energy to maintain the energy balance of the control unit.

[0017] The invention also includes optional further developments whose features provide additional advantages.

[0018] The aforementioned balancing criterion can, for example, stipulate that the balance data for each device is met, or at least met to a specified minimum extent, such as at least 70 percent or at least 80 percent. Performance data is considered met if the energy demand / power requirement is covered and / or the energy supply and / or capacity is utilized. A further development stipulates that the balancing criterion includes the requirement that the balance data for at least one of the connected devices is met to at least a specified minimum extent. This can therefore apply to a single connected device, to some of the connected devices, or to all of the connected devices. Another balancing criterion could, for example, state that only the demand side, i.e., the energy demand and / or power requirement, is met, or at least met to a specified minimum extent.

[0019] Further training stipulates that the balance data of at least one device must include a time indication for the validity of that data, and that the control unit executes the transfer of electrical energy based on time and / or sets the balancing criterion based on time. In other words, a device can specify in its balance data, by adding a time indication, the time within which the energy demand must be met, or at what point in time the energy and / or power must or will be available. This allows the energy transfer to be postponed or delayed, for example, to take place at a later, more favorable time, because a vehicle is not used overnight and its balance data only needs to be fulfilled the following morning.

[0020] One advanced feature addresses the situation where balance data can conflict, meaning that the balance requirements of all devices cannot be met. In this feature, the control unit receives user-defined default data for priority control via a user interface. Depending on this default data, the control unit then prioritizes the balance data of one device over that of another when defining the balancing criterion. This ensures that a device whose balance data is given priority is always supplied according to the balance requirements. This is particularly advantageous when charging a motor vehicle.

[0021] Further training also considers economic aspects of the operation. This training takes into account control parameters, such as energy tariff information and / or energy compensation, when setting a time profile for energy transmission and / or defining the balancing criterion. For example, if solar energy from a solar panel, as a renewable energy source, receives a high compensation, its output can be fed into a public grid, and simultaneously, or in parallel, a vehicle can be charged with energy from the energy storage system if this is more cost-effective or profitable than charging the vehicle directly via the solar panel.

[0022] A further development of the invention enables the gentle operation of the connected devices. In this further development, the control unit receives operating data from at least one connected device via the communication interface of the associated connection. This data signals an operating state and / or at least one permissible or available operating point of the device. For example, the current operating temperature of the device can be specified as an operating state, allowing the control unit to enable thermally gentle operation of the device. An available operating point refers to an operating state of the device that can be assumed without damaging the device. For example, a permissible maximum current of an electric current flowing between the device and its connection and / or a valid voltage range for the electric voltage generated at the device can be specified.Depending on the received operating data, the control unit sets a time-based profile for the energy transfer. This allows, for example, a predetermined amount of energy to be exchanged with the device over a predetermined time interval in such a way that the device is in a valid operating point at all times.

[0023] Therefore, it is specifically intended that the operating data will indicate an operating temperature and / or a maximum current and / or an operating time. The operating time can, for example, be specified as the time interval within which the device is connected to a terminal of the DC-DC converter and must be supplied with electrical energy or can supply electrical energy.

[0024] Further development enables the control unit itself to adjust the operating state of a connected device, thereby facilitating the exchange of electrical energy. In this process, the control unit transmits control data via the corresponding communication interface of the respective port to regulate the energy input and / or output of the device. Thus, the control unit can actively or selectively configure the device to have an operating state favorable for energy transfer.

[0025] To carry out the method according to the invention, the invention also provides the described high-voltage DC-DC converter, which, as described, has an intermediate circuit that is coupled via a respective converter stage to at least one vehicle connection, at least one storage connection, and at least one source connection, in order to connect, as described, at least one electrically powered motor vehicle, at least one electrical energy storage device, and at least one renewable energy source to the DC-DC converter. The converter stages are controlled by the aforementioned control unit.According to the invention, the DC-DC converter now has a communication interface in addition to each terminal, wherein the control device is configured to carry out an embodiment of the inventive method in order to control or adjust a transfer of electrical energy between the terminals depending on the balance data received via the communication interface.

[0026] The high-voltage DC-DC converter according to the invention can, for example, be provided in the form of a connection device or a connection module, which can be installed, for example, in a building. The building can then be equipped with at least one energy storage device, at least one renewable energy source, and a connection for charging an electric vehicle, and these devices can then be coordinated with each other with respect to energy exchange via the DC-DC converter. Since all converter stages operate on the same intermediate circuit, i.e., are coupled to the same intermediate circuit, the number of conversion steps for transferring energy between two devices is minimal.

[0027] An embodiment of the invention is described below. The single figure (Fig.) shows a schematic representation of an embodiment of the high-voltage DC-DC converter according to the invention.

[0028] The embodiment described below is a preferred embodiment of the invention. In this embodiment, the described components each represent individual features of the invention that can be considered independently of one another. Each of these features further develops the invention independently and can therefore be considered part of the invention individually or in a combination other than that shown. Furthermore, the described embodiment can also be supplemented by other features of the invention already described.

[0029] The figure shows a high-voltage direct current (DC) converter, or DC converter 1 for short, to which, in the example shown, one or more electrical buffer storage devices or energy storage devices 2, one or more renewable energy sources 3, and one or more electrically powered motor vehicles, or electric vehicles 4 for short, can be connected. The DC converter 1 can, for example, be installed in a stationary position in a building 5.

[0030] For the sake of simplicity, and without limiting the generality of the example, it is assumed that a single energy storage device 2, a single renewable energy source 3, and a single electric vehicle 4 are connected to the DC-DC converter 1. The energy storage device 2 could, for example, be a high-voltage battery. The renewable energy source 3 could, for example, be a solar panel or a wind turbine. The electric vehicle 4 could, for example, be a motor vehicle, in particular a passenger car, which can be powered purely electrically or may be a hybrid vehicle.

[0031] The energy storage device 2 is connected via a storage terminal 6 to provide a transfer 7 of electrical energy between the DC-DC converter 1 and the energy storage device 2. Additionally, a communication interface 8 is provided through which communication data 9 can be exchanged between the DC-DC converter 1 and the energy storage device 2. Similarly, the energy source 3 is connected to a source terminal 10 of the DC-DC converter 1 for the transfer 11 of electrical energy from the energy source 3 to the DC-DC converter 1. Additionally, a communication interface 8 is provided through which the energy source 3 and the DC-DC converter 1 can exchange communication data 9. The vehicle 4 is connected to a vehicle terminal 12 for the transfer 13 of electrical energy between the electric vehicle 4 and the DC-DC converter 1.Additionally, a communication interface 8 is provided, via which the DC voltage converter 1 and the electric vehicle 4 can exchange communication data 9.

[0032] In general, the energy storage devices 2, energy sources 3 and electric vehicles 4 connected to terminals 6, 10, 12 are referred to below as devices D (Device - device) to be supplied.

[0033] The terminals 6, 10, and 12 of the DC-DC converter 1 are connected to a DC intermediate circuit 15 via a respective converter stage 14 in a manner known per se. This intermediate circuit allows the converter stages 14 to exchange electrical energy, thus providing electrical energy for the transmission 7, 11, and 13 between the terminals 6, 10, and 12. Each converter stage 14 can, for example, be based on a controllable boost converter and / or buck converter.

[0034] The converter stages 14 of the DC-DC converter 1 can be controlled in a manner known per se by a control unit 16. The control unit 16 can, for example, be based on a microcontroller or an integrated circuit (IC), such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and / or on a microprocessor.

[0035] The communication interfaces 8 can be implemented, for example, as radio interfaces or as wired interfaces, the latter being integrated, for example, in a plug socket through which the respective connection 6, 10, 12 is implemented.

[0036] The connected devices D can signal their electrical energy or electrical power requirements, or the electrical energy and / or electrical power they can provide, to the control unit 16 of the DC-DC converter 1. The communication data 9 then includes corresponding balance data 17.

[0037] Based on the balance data 17, the control unit 16 can determine a balancing criterion 18, which specifies, for example, that one, some, or all of the devices must exchange energy with the DC / DC converter 1 to at least a predetermined minimum extent, according to their balance data. For this purpose, the DC / DC converter 1 can be operated by the control unit 16 as a current-controlled DC / DC converter. Such control of the converter stages 14 by the control unit 16 is known from the prior art.

[0038] Via a user interface 19, a user can optionally transmit preset data 20 to the control unit 16, which can give priority to one of the devices D, for example to ensure that at a certain time, for example in the morning, the device D is supplied with energy according to its balance data 17, for example the motor vehicle 4 is charged.

[0039] The control unit 16 can also take into account, for example, control parameters 21, such as an energy price or an energy compensation tariff.

[0040] Operating data 22 of the devices D, such as an operating temperature and / or a permissible maximum current and / or an operating time, can also be taken into account when defining the compensation criterion 18 and / or during transmission 7, 11, 13. The operating data 22 can be provided by the devices D as part of the communication data.

[0041] In the example shown, an energy balance can be achieved via a DC / AC converter 23, through which, for example, the energy storage device 2 can be connected to the building's electrical network 24, which can operate on alternating current (e.g., 230 volts, 50 hertz). The building's electrical network 24 can be connected to a public power grid 25, with which balancing energy 26 can be exchanged to balance the energy balance of the control unit 16.

[0042] The control unit 16 can also be designed to send control data 27 as communication data 9 to the devices D via the respective communication interface 8, and thereby to set the operating state of the devices D.

[0043] Energy storage device 2 can be operated as both an energy source and an energy sink. Connection 6 is configured accordingly. Similarly, the vehicle 4 can also be operated as both an energy source and an energy sink; connection 12 is configured accordingly. The renewable energy source 3 is solely an energy source, so connection 10 only needs to be configured as an input for electrical energy. For example, a 150-volt solar module could be used. Energy storage device 2 could, for example, be a 75-volt storage device. In contrast, the traction battery of the electric vehicle 4 could, for example, be a 450-volt battery. The different voltage levels can be equalized or converted to a common DC link voltage level by means of the converter stages 14.

[0044] Thus, direct charging of the electric vehicle 4 or the electrical home buffer storage or energy storage system 2 is achieved by means of a variable current-controlled high-voltage DC / DC converter and suitable high-voltage DC / DC current direction control by the control unit 16. Every possible DC current charging direction is realized with only one conversion process, i.e.: 1. Electric vehicle → electrical buffer storage in the house 2. Electrical buffer storage in the house → Electric vehicle 3. Solar panels → Electric vehicle 4. Solar modules → electrical buffer storage in the house 5. Solar modules → Electric vehicle and electrical buffer storage in the house

[0045] Since only the three converter stages 14 are required as the sole conversion elements for all conversion processes, the costs of providing the DC-DC converter 1 are low. In operation, the small number of converter stages in operation also results in high efficiency due to low converter losses.

[0046] Naturally, the electric vehicle 4 and the energy storage device 2 must have suitable communication interfaces and provide control options for charging and / or discharging so that they can communicate with the control unit 16 via the communication interfaces 8.

[0047] Optionally, a power converter unit for DC / AC conversion can also be provided, which is supplied directly by the DC voltage converter 1 instead of the converter 23 and is coupled to the intermediate circuit 15.

[0048] Thus, the DC voltage converter 1 results in a power converter that can directly convert the energy between its inputs / outputs into any format (DC / AC single-phase / AC multi-phase) and, in combination with a parameterizable control that controls these power flows, continuously exchanges, updates and recalculates parameters with all connected components or devices D.

[0049] Overall, this example shows how the invention can provide a high-voltage DC / DC converter with priority control.

Claims

[1] Method for operating a high-voltage DC-DC converter (1) having an intermediate circuit (15) which is coupled via a respective converter stage (14) to at least one vehicle connection (12) for an electrically driven motor vehicle (4) as the device (D) to be supplied, and to at least one storage connection (6) for an electrical energy storage device (2) as the device (D) to be supplied, and to at least one source connection (10) for a regenerative energy source (3) as the device (D) to be supplied, wherein in the method the respective converter stages (14) of the connections (6, 10, 12) are controlled by a control device (16) for transmitting (7, 11, 13) electrical energy between at least two of the connections (6, 10, 12), characterized bythat a communication interface (8) is provided for each connection (6, 10, 12) and the control device (16) receives from each device (D) connected to a respective one of the connections (6, 10, 12) balance data (17), which includes at least one of the following information of the device (D): Energy requirement, power requirement, energy supply, performance capacity, and sets an energy quantity and transmission direction of the electrical energy transmitted between the terminals (6, 10, 12) in such a way that an energy balance of the energy exchanged between the devices (D) satisfies a balancing criterion (18) determined on the basis of the balance data (17), wherein the connected energy storage device (2) has a power converter unit (23) via which the energy storage device (2) indirectly obtains additional energy by the energy balance is balanced via the power converter unit (23), via which the energy storage device (2) is coupled to a domestic network (24) of a building (5) which is operated on an alternating current basis, and the domestic network (24) is coupled to a public supply network (25), with which balancing energy (26) is exchanged to balance the energy balance of the control device (16). [2] Method according to claim 1, wherein the balancing criterion (18) comprises that for at least one of the connected devices (D) its balance data (17) are fulfilled at least to a predetermined minimum extent. [3] Method according to one of the preceding claims, wherein the balance data (17) of at least one device (D) each contain a time indication for the validity of the balance data (17) and the control device (16) carries out the transmission (7, 11, 13) of the electrical energy in a time-dependent manner and / or sets the compensation criterion (18) in a time-dependent manner. [4] Method according to one of the preceding claims, wherein the control device (16) receives user-defined default data (20) for a priority control via a user interface (19) and the control device (16), depending on the default data (20), gives priority to the balance data (17) of one device (D) over the balance data (17) of another device (D) when determining the balancing criterion (18). [5] Method according to one of the preceding claims, wherein control parameters (21) describing tariff information for energy and / or a remuneration for energy are taken into account when setting a time profile of the transmission (7, 11, 13) of the energy and / or when setting the compensation criterion (18). [6] Method according to one of the preceding claims, wherein the control device (16) receives operating data (22) from at least one connected device (D) via the communication interface (8) of the associated connection (6, 10, 12), which signal an operating state and / or at least one available operating point of the device (D), and sets a time profile of the transmission (7, 11, 13) of the energy as a function of the operating data (22). [7] Method according to claim 6, wherein the operating data (22) signal an operating temperature and / or a maximum current and / or an operating time. [8] Method according to one of the preceding claims, wherein the control device (16) for transmitting (7, 11, 13) the energy between the at least one connection (6, 10, 12) and a device (D) connected thereto, via the associated communication interface (8) of the respective connection (6, 10, 12), transmits control data (27) for controlling an energy input or energy output of the device (D). [9] Arrangement comprising an electrical energy storage device (2) and a high-voltage DC-DC converter (1) having an intermediate circuit (15) which is coupled via a respective converter stage (14) to at least one vehicle connection (12) for an electrically driven motor vehicle (4) as the device (D) to be supplied, and to at least one storage connection (6) for the electrical energy storage device (2) as the device (D) to be supplied, and to at least one source connection (10) for a regenerative energy source (3) as the device (D) to be supplied, and which has a control device (16) for controlling the converter stages (14), characterized by that a communication interface (8) is provided for each connection (6, 10, 12) and the control device (16) is designed to carry out a method according to one of the preceding claims.

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