BATTERY TESTING SYSTEM WITH BASIC VOLTAGE CONVERTERS AND BOOSTER VOLTAGE CONVERTERS

Description

[0001] The invention relates to a testing system for the simultaneous testing of several batteries, in particular high-voltage batteries, and a method for testing several test specimens with a testing system.

[0002] The demand for electrical test systems is currently increasing sharply due to the electrification of various previously non-electrified technology fields. Test systems can be configured to simulate the stresses of a device under test's life cycle and are capable of charging and / or discharging a device connected to a test channel with the power required by the respective test procedure. This applies to each individual test channel and each individual device under test. Battery testing is of particular interest. Battery test procedures often exhibit significant differences in the test power required at different times. Frequently, only low charging or discharging power is needed for extended periods, while for short periods, a particularly high charging or discharging power is required on a single device under test.

[0003] In known test systems, electrical transducers are used to provide the necessary power transfer. Each transducer is coupled to a test channel. To cover the power requirements of each device under test, the transducers are designed for the maximum power that can be supplied by the respective test channel. Such transducers must therefore cover a large power range and are thus particularly expensive. However, in many applications, the maximum power range is only used for very short periods. With such a one-to-one coupling between transducer and test channel, the exclusive use of inexpensive transducers with a lower power range is not possible due to the power range required for the test.

[0004] For example, patent WO2021 / 174278 A1 discloses a converter arrangement with at least two converters and a control unit connected to the converters. The control unit is configured to continuously or at discrete time intervals determine or receive from the converters their permissible electrical power range, in particular their minimum power value Pmin and / or their maximum power value Pmax, and the current power balance of the individual converters. Furthermore, it is configured to change the permissible electrical power range of the converters so that the power balance of the entire converter group does not exceed a predetermined range.

[0005] Furthermore, document DE102015215233 A1 discloses a system for a battery management system in vehicles, which serves to diagnose leaks in electronic components and to maintain the vehicle's drive state. The system monitors the insulation resistance of electronic components during vehicle operation to prevent safety risks such as electric shocks. The battery management system detects insulation resistance breakdown and locates defective parts. It can switch off the battery relay to stop the vehicle if necessary. The system is designed to perform stepwise measurements of the insulation resistance in various vehicle states, from switching on the vehicle and starting the engine to operating various load components such as the drive motor and air conditioning system.

[0006] Furthermore, document CN 110850294 A discloses a test system for battery packs. The test system comprises a bidirectional DC / DC converter, an AC / DC power supply module, a controller, an upper computer, a first battery pack under test, and a second battery pack under test. One end of the bidirectional DC / DC converter is connected to one end of the controller, the other end of the bidirectional DC / DC converter is connected to the first battery pack under test, and the other end of the controller is connected to the second battery pack under test and the AC / DC power supply module.

[0007] It is not fundamentally impossible for more than one converter to provide the required power. This would allow for the transfer of high power within a short period. However, if test systems are capable of transferring high power in the kW or MW range within a short timeframe, stringent safety requirements must be met to prevent the risk of a faulty circuit and the resulting short circuit. Simply coupling multiple converters to transfer additional power as needed leads to highly complex safety systems, even with just a few converters. This high complexity, due to the associated risk of individual component failure, is detrimental to the safety of the test system.

[0008] It is therefore the object of the invention to at least partially overcome the disadvantages described above in a cost-effective and simple manner. In particular, it is the object of the present invention to provide a testing system for the simultaneous testing of several test specimens that can be manufactured more cost-effectively than existing testing systems without compromising safety.

[0009] The problem is solved by a testing system with the features of claim 1 and a method for testing one or more test specimens according to claim 17. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the testing system according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always refers to, or can refer to, each other.

[0010] According to a first aspect, the invention provides a test system for the simultaneous testing of several batteries, in particular high-voltage batteries, comprising: a DC link, several base converters connected to the DC link, each of which is switchably connected to a test channel via a connecting line, a booster converter connected to the DC link, which during operation of the test system can be switched to various connecting lines to at least one of the test channels via a booster line and a switching node, a control unit for controlling the base converters and the booster converter according to a desired power transfer; wherein each connecting line has a safety-related switch between the test channel and the switching node.

[0011] A test system is defined as a device for simultaneously testing the physical properties of multiple test specimens. In particular, the test system is suitable for testing the electrical properties of test specimens at different temperatures. Suitable test specimens include, for example, batteries, especially high-voltage batteries such as those used in electric vehicles. Batteries are defined as individual cells, cells connected to form modules, and modules connected to form packs. Furthermore, it is generally possible to use the test system to test inverters, fuel cells, powertrains, DC / DC converters, chargers, or other electrical power transfer devices. Preferably, the test system is a power electronic test system.

[0012] A high-voltage battery is a storage device for electrical energy. It consists of several interconnected elements and of a few to thousands of battery cells or cell blocks connected in parallel and series.

[0013] A DC link is a DC circuit designed to transfer electrical power between different components of a test system. The voltage provided by the DC link should remain as constant as possible, even under load, and can be, for example, 750 V. The DC link can also have more than two voltage levels, thus representing a multi-level topology. Alternatively, or in addition to a DC link, a DC circuit can also be used.

[0014] A basic-mode power converter (BMC) is an electrical circuit that converts an input DC voltage into a DC voltage with a higher, lower, or inverted voltage level and is designed to transfer a basic voltage level and / or a basic power level via its output. Besides converting one DC voltage to another, a BMC can also be designed to convert AC voltage to DC, AC voltage to another AC voltage, or DC voltage to AC voltage. The conversion is achieved using a power electronic circuit and one or more energy storage devices. A basic power supply can, for example, range from 20 kW to 300 kW. BMCs are fundamentally designed to convert electrical power bidirectionally.

[0015] A connecting cable is an electrical cable designed to connect a basic converter to a test channel. The connecting cable is preferably multi-pole.

[0016] A test channel is a device used to connect a unit under test (UUT) for testing. A UUT can be connected via multiple test channels. The test channel can be part of a test setup. The test setup could be, for example, a battery test bench, a fuel cell test bench, a charger test bench, a powertrain test bench, or a test bench for testing DC-DC converters. A test channel can be multi-pole.

[0017] A booster converter, like a basic converter, is an electrical circuit that converts an input DC voltage into a DC voltage with a higher, lower, or inverted voltage level. Booster converters are also fundamentally designed to convert electrical power bidirectionally and can be identical in design to basic converters. Preferably, however, booster converters are designed to transfer a power level at their output that, at a voltage level matching the basic converter, is higher than the basic power level.

[0018] Operation of the test system means that a device under test (DUT) is connected to the test system and a test run is being performed. During this operation, power may be transferred to or from the DUT, or the test system may be in a state where no power transfer to or from the DUT is taking place. The power transfer is not constant. The feature that a booster converter can be switched on during operation of the test system therefore also includes necessary safety devices that allow for switching on and off without damaging the test system or its operator.

[0019] A booster line is an electrical line extending from a booster converter. Several connecting lines are switchably linked to the booster line. The booster line can consist of several segments, connected, for example, by nodes. In particular, it may be designed so that only segments of the booster line are switchably connected to the multiple connecting lines. It is essential to ensure that, during operation of the test system, only one connecting line, or none at all, is connected to the booster line. If several connecting lines are simultaneously connected to the booster line during operation of the test system, there is a risk of unintended voltage transfer if different voltages are present on the connected lines.

[0020] A switching node is a point in the electrical network of the test system where two terminals of the connecting cable and one terminal of the booster cable meet, and where the current can branch. At the switching node, a current flowing in the connecting cable can thus be superimposed on a current flowing in the booster cable.

[0021] The control unit is configured to control the base converters and the booster converter(s), i.e., to set the power to be transferred by the converters. For this purpose, the control unit is coupled to the converters via a signal connection. The control unit knows the contents of the storage unit and the setpoints for current and / or voltage and / or power, and measures or collects the corresponding actual values. Furthermore, the control unit can be configured to calculate the current or future setpoints for feedforward control of an input into the DC link (e.g., an active front-end converter) and / or the storage unit.

[0022] A power transfer can be positive, negative, or zero, thus encompassing both a power output and a power input.

[0023] A safety-related switch is designed according to safety-related design principles that must be adhered to in order to minimize the risk of malfunction. Safety-related switches are specifically designed to detect or make detectable their own switching state and / or a malfunction.

[0024] Preferably, in the test system according to the invention, the DC voltage intermediate circuit is connected to a power grid via a power converter.

[0025] The power converter transforms a voltage available at the test bench, for example, a multi-phase mains voltage, into a DC voltage, which is referred to as the intermediate circuit voltage. The power converter can be a rectifier (AC-DC converter, active front-end converter), for example, a switched bridge rectifier. The voltage conversion is bidirectional. Converting the AC voltage to a DC voltage results in more precise control due to the smoother input voltage.

[0026] A power grid is a network for the transmission and distribution of electrical energy. The power grid is preferably an alternating current (AC) grid, but can also be a direct current (DC) grid. If the grid is a DC grid, a DC / DC converter is used as the grid converter, which converts the grid voltage into a suitable intermediate circuit voltage.

[0027] A further advantage can be achieved if the test system also includes a storage device which is configured to transfer power to or from at least one of the test channels, wherein the storage device is connected directly or via additional power electronics to the DC link.

[0028] The energy storage device is a device for storing electrical energy and can include accumulators, supercapacitors, or other physical or chemical energy storage devices. The energy storage device serves to stabilize the DC link in situations where the test system draws a large amount of power from or supplies a large amount of power to the DC link.

[0029] It is also advantageous if the storage device includes a chopper.

[0030] A chopper is a switchable resistor that converts power into heat when needed, thus drawing electrical power from the test system. The chopper can be actively or passively controlled.

[0031] It is further advantageous if the test system also includes an active front-end converter that is designed to transfer power into or out of the power grid.

[0032] The active front-end converter is a controllable rectifier with bidirectional power transfer between AC and DC and the ability to feed power back into the grid. If the test system is connected to a power grid in such a way that current can be fed back from the test system to the grid, the test system must include an active grid-connected power converter (active front-end converter).

[0033] In particular, it may be provided that the basic converter can be operated in a first power range and the booster converter can be operated in a second power range, and that the first power range is smaller than the second power range.

[0034] In test systems for high-voltage batteries, the first power range can, for example, cover power outputs up to 300 kW, and the second power range up to 750 kW. Converters with particularly large power ranges are more expensive to purchase than those with lower power ranges. The cost advantage in manufacturing the test system can be further increased by using different power ranges.

[0035] It is also advantageous if the ratio of the number of booster converters to the number of basic converters in the test system is between 1 / 2 and 1 / 6, in particular between 1 / 3 and 1 / 5.

[0036] The ratio of booster converters to base converters can be optimized according to the booster converter utilization. A booster converter should be available when it is needed to provide higher transfer rates, but has short idle times during which its power is not required. This ratio depends on the specific application and the power ranges of the base and booster converters. For high-voltage battery test systems and the associated test runs, a ratio of four base converters per booster converter can represent a cost-optimized compromise.

[0037] It is also advantageous if a voltage measuring device is arranged above each of the safety-related switches.

[0038] The voltage measuring device is designed to measure the voltage on both sides of a switch, thus preventing the switch from closing in the event of unwanted voltage differences on either side. This measurement is preferably performed on all switches in the test system. The data acquired from the voltage measurement are transmitted to the control unit.

[0039] A further advantage can be achieved if at least one of the safety-related switches has a parallel connection of several switches.

[0040] The parallel circuit can consist of a resistance-coupled switch and a resistance-free switch. When the resistance-coupled switch is closed first, voltage differences on both sides of the safety-related switch are balanced in such a way that no excessively high currents flow, which could cause damage or distort the test result. In the closed position, the entire current is then conducted through the resistance-free switch with virtually no loss.

[0041] Furthermore, it is advantageous if at least one of the safety-related switches is designed to switch a direct current superimposed with ripple current.

[0042] In this particular embodiment of the invention, the corresponding safety-related switch comprises a parallel connection of several switches, wherein one of the switches in the parallel connection is configured for conducting direct current and another switch in the parallel connection is configured for conducting alternating current. In test systems for high-voltage batteries, the currents to be transferred are often direct currents (DC component) superimposed on an alternating current or ripple current (AC component). The ripple currents can be generated by modulating the setpoint of the booster converter. Typically, the majority of the power is transferred via the direct current, while a smaller portion is transferred via the alternating current or ripple current. To ensure a realistic test situation, the transfer of both components is necessary.A simple high-power switch is generally unsuitable for transmitting such superimposed DC and AC components, since the high currents of the DC component require conductors with a large diameter, while the AC components can only flow on the surface of such conductors. Connecting an AC switch and a DC switch in parallel allows for better transmission of both components. Due to the different current intensities of the AC and DC components, the AC switch can be designed to conduct smaller currents than the DC switch. In particular, such a parallel circuit can be configured to close the AC switch first and then the DC switch in a switching process.

[0043] Preferably, the storage device may also include a fast storage device with fast access time and a slow storage device with slow access time, and the fast storage device has a lower capacity than the slow storage device.

[0044] The combination of fast and slow storage enables cost-optimized use of both systems. While fast storage devices can absorb and release short-term load changes, slow storage devices generally allow for lower-loss storage of electrical energy at a lower cost. Examples of fast storage devices include supercapacitors, and examples of slow storage devices include accumulators.

[0045] Preferably, the booster line includes a booster switch for switching booster power to at least one of the test channels.

[0046] The booster switch can be designed as a contactor switch, but is preferably a power electronics semiconductor switch such as an IGBT or MOSFET. The power electronics semiconductor switch can utilize semiconductor materials such as silicon (Si), GaN, SiC, or other semiconductor materials. A short switching time is advantageous when adding the booster power to the base power, allowing for precise adherence to the voltage profile specified in a test run and enabling de-energized switching even during rapid changes in the power being transferred. The fast switching times of a power electronics semiconductor switch allow the booster line to be de-energized at any time during operation, even during load changes, to any of the multiple connecting lines.Power electronic semiconductor switches achieve switching times in the nanosecond range, while contactor switches have switching times of approximately 10 milliseconds and are therefore significantly slower. To prevent multiple test channels from being short-circuited via the booster line, the booster switches preferably have a safety-related input. This safety-related input can either prevent or allow the switching state of the booster switch to be changed. Such a safety-related input can be easily implemented analogously to a safe torque-off switch in a drive converter. The switch can only be closed or opened if the safety-related input allows a change in the switching state. Furthermore, the control unit can be configured so that only one booster switch may be closed at a time.A channel would therefore only be enabled for activation via the booster switch once it has been ensured that no further channel can be activated. A safety-related input does not, in principle, delay the switching time of the booster switch.

[0047] Furthermore, preferably the base converter and / or the booster converter(s) each have decoupling capacitors and the output capacitance of the decoupling capacitors of the booster converter or the booster converter is smaller than the output capacitance of decoupling capacitors of the base converter.

[0048] The output capacitors of the converters support the output voltage and keep it stable. However, if one of the base converters or one of the booster converters is not connected to a test channel without a voltage being de-energized, a current flows between the test channel and the decoupling capacitor. The current depends on the size of the connected output capacitor and can also affect the test run. Such faulty connections can occur, in particular, during faulty voltage measurements. It is therefore advantageous to keep the capacitors not located directly at the test channel as small as possible. This applies especially to the output capacitors of the regularly connected booster converters. The booster converter can also include a multi-level converter. In this case, an output capacitor can be omitted.

[0049] It is also advantageous if at least one of the base converters is galvanically isolated from the DC link.

[0050] Galvanic isolation refers to the prevention of electrical conduction between two circuits between which power or signals are to be exchanged. With galvanic isolation, the electrical potentials are separated, and the circuits are therefore potential-free from each other. Preferably, the booster converter is also galvanically isolated from the DC link. Particularly preferably, all base converters and / or all booster converters are galvanically isolated from the DC link. Galvanic isolation offers greater safety, enables more accurate voltage measurements independent of the DC link, and prevents electromagnetic interference as well as unwanted interactions between the test channels.

[0051] A further advantage can be achieved if the safety-related switches are connected to a safety system via signaling technology.

[0052] The safety system primarily controls the safety-related switches. An isolation monitor measures whether the intended galvanic isolation of the base converters and / or booster converters is intact. If a fault related to one or more galvanic isolation points is detected, the safety system opens the safety-related switches associated with the fault and / or prevents them from closing. Furthermore, the control unit for the safety-related switches is integrated.

[0053] It is also conceivable that the test system includes a second booster converter connected to the DC link, which can be switched on to the booster line during operation of the test system.

[0054] A second booster converter can be configured in the same or different ways as the first. The second booster converter can be connected to a second booster line, which in turn can be connected to various connecting lines to at least one of the test channels via a switching node. The connection of the second booster converter to the booster line of the first booster converter can be made via a connecting switch connected to both booster lines. Before connection, the voltage across the connecting switch is measured and, if necessary, regulated to ensure that the connection is voltage-free. In addition to a second booster converter, the test system can include further booster converters as required, which can be connected and switched in the same way as the first two booster converters.

[0055] According to a second aspect, the invention provides a method for testing one or more test specimens with a testing system, in particular according to one of the preceding claims, comprising the steps: a) Connecting a device under test to one of the test channels; b) Starting a test run on the device under test; c) Sending a power request for a test channel to the control unit; d) Checking whether the requested power is greater in magnitude than the power transferable by the basic converter; e) Connecting the booster converter to one of the test channels if the requested power is greater in magnitude than the power transferable by the basic converter; f) Transferring the requested power via the basic converter and the booster converter.

[0056] Any unit that supplies or receives electrical energy is suitable as a test object. In particular, suitable test objects include: batteries, preferably rechargeable batteries, especially high-voltage batteries, inverters, fuel cells, electric drive trains, DC / DC converters, and electric charging devices.

[0057] In a test run, the device under test is operated under various conditions to test its function and performance. The sequence of these conditions is defined before the test run begins. For example, with high-voltage batteries, the test run can include charge and discharge cycles that are expected to occur during the battery's lifetime. Typically, several test runs are started simultaneously or in quick succession on a test setup with multiple test channels. It is advantageous if the test runs are started in such a way that, throughout the entire duration of all test runs, only one of the test channels sends a power request that exceeds the power of the base converter connected to that channel. This ensures that only one of the test channels needs to connect the booster converter(s) to transfer the requested power.

[0058] It is particularly advantageous to coordinate test runs performed on different test channels in such a way that the power input of one test channel matches the power output of another. This reduces the load on the DC link and minimizes overall power transfer. As a result, operating costs for the test equipment can be lowered. Naturally, such optimization is only possible with devices under test where power transfer in both directions is possible, such as high-voltage batteries.

[0059] In the method according to the second aspect of the invention, it is preferably provided that the power request is sent to the control unit at least 1µs, preferably at least 100µs, before the power is provided.

[0060] By sending the power request before providing the power, the control unit can equalize voltages between parts of the test system to be switched, thereby improving the switching operations.

[0061] Furthermore, the invention provides a computer program product comprising instructions which, when the program is executed by a computer, cause it to execute the method according to one of claims 17 or 18.

[0062] Finally, the invention provides a computer-readable data carrier on which the computer program product according to claim 19 is stored.

[0063] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination. The drawings schematically show: Figure 1 shows a circuit diagram of a test system according to a particular embodiment of the invention; and Figure 2 shows an enlarged section of the circuit diagram. Figure 1 , which shows additional details.

[0064] Figure 1 shows a circuit diagram of a test system 10 according to the invention in a particular embodiment of the invention.

[0065] Test system 10 is designed for the simultaneous testing of several devices under test 20a-20h. The test system includes a DC link 22 to which essential elements of test system 10 are connected. The DC link 22 is designed with two poles. Furthermore, test system 10 includes several base-mode converters 1a-1h connected to the DC link 22. Each base-mode converter 1a-1h can be connected to a test channel 4a-4h via a connecting line 24. Thus, there is a one-to-one coupling between the base-mode converter 1a-h and the test channel 4a-h. Each test channel 4a-4h is electrically connected to exactly one of the base-mode converters 1a-1h.

[0066] In addition to the eight basic converters 1a-1h, the test system 10 also includes a first booster converter 2a and a second booster converter 2b connected to the DC link 22. The booster converters 2a-2b can each be connected to various connection lines 24 to the test channels 4a-4h via a booster line 26a, 26b, and a switching node 18a-18h. Specifically, the connection is made via booster switches 16a-16h, to which a booster line 26a, 26b is switchably connected to several connection lines. The connection lines 24 are in Figure 1For clarity, they are shown as single-pole connections, but are fundamentally designed with at least two poles. Specifically, booster converter 2a can be switched to test channels 4a-4d via booster line 26a, and booster converter 2b can be switched to test channels 4e-4h via booster line 26b, at least as long as there is no coupling between the two booster lines 26a-26b, which is discussed below.

[0067] Each connecting line 24a-24h has a safety-related switch 6a-6h between test channel 4a-4h and switching node 18a-18h. In principle, each of the safety-related switches 6a-6h is designed such that each individual line of the multi-pole connecting lines 24a-24h can be switched. The safety-related switches 6a-6h are located on a connecting line 24a-24h between test channel 4a-4h and switching node 18a-18h.

[0068] During operation of test system 10, booster converter 2a can be connected to each of the connection lines 24a-24d via booster line 26a and connection nodes 18a-18d, and via these to the respective test channels 4a-4d. Similarly, booster converter 2b can be connected to the connection lines 24e-24h via booster line 26b and connection nodes 18e-18h, and via these to the respective test channels 4e-4h. Although booster lines 26a and 26b can be connected to several of the connection lines 24a-24h, to prevent short circuits between the connection lines, it is specified that each booster line 26a or 26b can only be connected to one of the connection lines 24a-24h at any given time.

[0069] The test system 10, with its two booster converters 2a and 2b and two booster lines 26a and 26b, provides power to two separate test channels 4a-4h, one from the group of test channels 4a-4d and one from the group 4e-4h. Booster lines 26a and 26b are connected to each other via a coupling switch 32, which can also be switched between them. This allows the power of a base converter 1a-1h to be combined with the power of the first booster converter 2a and the power of the second booster converter 2b. This enables the transfer of even higher power levels to or from a test channel 4a-4h. The coupling switch 32 is also connected to the safety system 9, which prevents multiple test channels 4a-4h from being coupled together via a single booster line 26a or 26b.

[0070] The test system 10 further comprises a control unit 27 for controlling the basic converters 1a-1h and the booster converters 2a, 2b according to a desired power transfer. For this purpose, the control unit 27 is connected via a first signal line 28a to the basic converters 1a-1h and the booster converters 2a, 2b, and via a second signal line 28b to voltage measuring devices 30a-30h, which are configured to measure the voltages present at the test channels 4a-4h. The first signal line 28a is configured to send control signals to the basic converters 1a-1h and the booster converters 2a, 2b. The second signal line 28b measures the voltage present at the test channel 4a-4h. The signal lines 28a, 28b, and 28c are shown as dashed lines. Furthermore, the control unit 27 is connected to the safety system 9 via a connecting cable. Alternatively, the safety system 9 can also be integrated directly into the control unit 27.Safety system 9 is designed to ensure the safety of the personnel operating the test system and the safety of the devices under test (20a-20h). It is connected to the connecting lines 24a-24h via signal line 28c and an insulation monitor 11. The insulation monitor 11 is configured to cyclically measure whether the galvanic isolation of the base converters 1a-1h and the booster converters 2a, 2b from the DC link is functioning. Faults in the galvanic isolation would lead to detectable fluctuations in the connecting lines 24a-24h. Furthermore, safety system 9 is connected via signal line 28d to the safety-related switches 6a-6h located between each test channel 4a-4h and a switching node 18a-18h. The switching of the safety-related switches 6a-6h is usually carried out by a switching signal sent from the control unit 27 to the safety system 9 via the connecting line 29.After verification and release by Safety System 9, Safety System 9 then switches the safety-related switches 6a-6d according to the received switching signal. Independently of this, Safety System 9 can open any of the safety-related switches 6a-6h, thus interrupting the electrical connection to the test channels 4a-4h and the devices under test 20a-20h. This may be necessary, in particular, if a fault in the operation of the galvanic isolation of the base converters 1a-1h and / or the booster converters 2a, 2b is detected.

[0071] Safety System 9 is also connected to booster switches 18a-18h via another signal line (not shown). Booster switches 16a-16h are configured to switch on booster power. Safety System 9 is responsible for ensuring that at any given time, either only one or no test channel 4a-4h is connected to a booster line 26a, 26b. Booster switches 16a-16h are power semiconductor switches equipped with a Safety Torque Off (STO) switch. The STO switch does not delay the very fast switching times of the power semiconductor switches, but it can prevent the equipped booster switch 16a-16h from closing at all. The Safety System can only release one of the STO switches at any given time, thereby preventing more than one booster switch 16a-16h from being closed per separate booster line 26a, 26b.This prevents a short circuit between two test channels 4a-4h and a resulting unwanted power transfer with potential damage to the test system 10 and technical personnel.

[0072] Each of the connecting lines 24a-24h leads from a basic converter 1a-1h to a test channel 4a-4h and, if one is connected, to a device under test 20a-20h. Each connecting line 24a-24h has a safety-related switch 6a-6h between test channel 4a-4h and switching node 18a-18h. This arrangement allows for the safe switching of both power supplied by the basic converters 1a-1h and power amplified by the booster converters 2a, 2b.

[0073] The DC link 22 is connected via a power converter 12 to a three-phase power grid 13, which supplies the DC link 22 with electrical power and through which electrical power can be discharged. For this purpose, the power converter 12 can be designed as an active front-end converter. A in Figure 1 The galvanic decoupling of the power converter 12 shown is not absolutely necessary if all base converters 1a-1h and all booster converters 2a, 2b are galvanically decoupled.

[0074] The test system 10 further comprises a storage device 3 connected to the DC link 22, which is configured to transfer power to and from the test channels 4a-4h via the base converters 1a-1h and the booster converters 2a, 2b. The storage device may comprise a battery, a supercapacitor and / or a chopper.

[0075] In this embodiment, the test system comprises eight basic converters 1a-1h and two booster converters 2a, 2b. The ratio of the number of booster converters 2a, 2b to the number of basic converters 1a-1h is therefore 1 / 4.

[0076] To verify the proper functioning of the test system 10, electrical measuring devices are arranged at various positions. Particularly when the test system is operating in the high-power range, a voltage measurement must be performed across each switch to prevent abrupt equalizing currents with high power levels. For this purpose, a voltage measuring device 30a-30h is provided across each switch, especially each safety-related switch. This device is configured to measure the voltage on both sides of the switch and ensure that both sides are at the same potential. In principle, a current measuring device can also be provided at any position where a voltage measuring device 30a-30h is installed. This additionally enables a measurement of the power transfer at the respective location. For the sake of clarity, not all voltage measuring devices 30a-30h are shown in the diagram. Figure 1 marked.

[0077] Figure 2 shows an enlarged section of the circuit diagram of Figure 1 , which shows additional details. As in connection with Figure 1 described, are in Figure 1 For the sake of clarity, some features are not shown in detail. In particular, it shows Figure 2In detail, the connecting lines 24a, 24b originating from the base converters 1a, 1b, as well as the DC link, are designed to be two-phase. Furthermore, it is shown in detail that the safety switches 6a, 6b are configured to switch each of the phases of the connecting lines 24a, 24b separately. If the safety switches 6a, 6b have a parallel connection of several switches, it is provided that each of the phases has such a parallel connection of several switches, although this is not shown in the particular embodiment of the invention presented here. Furthermore, the booster line 26a is two-phase and the booster switches 16a, 16b are designed to switch the multi-phase booster line. The voltage measuring devices 30a, 30b are arranged such that they measure the voltage between the individual phases of the two-phase test channel. The test system 10 is not shown in the Figure 2The depicted section is designed in the same way as in the Figure 2 depicted section. Reference symbol list:

[0078] 1a-1h Base converter 2a, 2b Booster converter 3 Storage device 4a-4h Test channel 6a-6h Safety-related switch 9 Safety system 10 Test system 11 Insulation monitor 12 Power converter 13 Power grid 16a-16h Booster switch 18a-18h Switching node 20a-20h Device under test 22 DC link 24a-24h Connection cable 26a, 26b Booster cable 27 Control unit 28a-28c Signal cable 29 Connecting cable 30a-30h Voltage measuring device 32 Coupling switch

Claims

1. Test system (10) for the simultaneous testing of multiple batteries, in particular high-voltage batteries, comprising: a DC voltage intermediate circuit (22), a plurality of base converters (1a-1h) connected to the DC voltage intermediate circuit (22), each base converter being switchably connected via a connection line (24a-24h) to a test channel (4a-4h), characterized by a booster converter (2a, 2b) connected to the DC voltage intermediate circuit (22), which, during operation of the test system (10), is connectable via a booster line (26a, 26b) and a respective switching node (18a-18h) to different ones of the connection lines (24a-24h) to at least one of the test channels (4a-4h), a control unit (27) configured to control the base converters (1a-1h) and the booster converter (2a, 2b) in accordance with a desired power transfer; wherein each connection line (24a-24h) comprises a safety-oriented switch (6a-6h) arranged between the test channel (4a-4h) and the switching node (18a-18h), the safety-oriented switch (6a-6h) being configured to detect, or to make detectable, its own switching state and / or its own malfunction.

2. Test system (10) according to claim 1, wherein the DC voltage intermediate circuit (22) is connected to a power supply grid (13) via a mains inverter (12).

3. Test system (10) according to claim 1 or 2, further comprising a storage device (3) configured to transfer power to at least one of the test channels (4a-4h) or from at least one of the test channels (4a-4h), wherein the storage device (3) is connected to the DC voltage intermediate circuit (22).

4. Test system (10) according to any one of the preceding claims, wherein the storage device (3) comprises a chopper.

5. Test system (10) according to any one of claims 2 to 4, further comprising an active front-end converter which is configured to transfer power to the power supply grid (13) or from the power supply grid (13).

6. Test system (10) according to any one of the preceding claims, wherein the base converter (1a-1h) is operable in a first power range and the booster converter (2a, 2b) is operable in a second power range, and the first power range is smaller than the second power range.

7. Test system (10) according to any one of the preceding claims, wherein the ratio of the number of booster converters (2a, 2b) to the number of base converters (1a-1h) in the test system (10) is between 1 / 2 and 1 / 6, and preferably between 1 / 3 and 1 / 5.

8. Test system (10) according to any one of the preceding claims, wherein a voltage measuring device (30a-30h) is arranged above each of the safety-related switches (6a-6h).

9. Test system (10) according to any one of the preceding claims, wherein at least one of the safety-related switches (6a-6h) comprises a parallel connection of several switches (6a-6h).

10. Test system (10) according to any one of the preceding claims, wherein at least one of the safety-related switches (6a-6h) is configured to switch a direct current that is superimposed with ripple current.

11. Test system (10) according to any one of the preceding claims, wherein the storage device (3) comprises a fast storage with fast access time and a slow storage with slow access time, and the fast storage comprises a lower capacity than the slow storage.

12. Test system (10) according to any one of the preceding claims, wherein the booster line (26a, 26b) comprises a booster switch (16a-16h) for switching a boost power to at least one of the test channels (4a-4h).

13. Test system (10) according to any one of the preceding claims, wherein the base converter (1a-1h) and / or the booster converter(s) (2a, 2b) each comprises back-up capacitors and an output capacitance of the back-up capacitors of the booster converter (2a, 2b) or the booster converters (2a, 2b) is less than an output capacitance of the back-up capacitors of the base converters (1a-1h).

14. Test system (10) according to any one of the preceding claims, wherein at least one of the base converters (1a-1h) is galvanically isolated from the DC voltage intermediate circuit (22).

15. Test system (10) according to any one of the preceding claims, wherein the safety-related switches (6a-6h) are signal-technically connected to a safety system (9).

16. Test system (10) according to any one of the preceding claims, wherein the test system (10) comprises a second booster converter (2a, 2b) connected to the DC voltage intermediate circuit (22) which is connectable to the booster line (26a, 26b) during operation of the test system (10).

17. Method for testing one or more devices under test (20a-20h) using a test system (10) according to any one of the preceding claims, comprising the steps of: a) connecting a device under test (20a-20h) to one of the test channels (4a-4h); b) starting a test run on the device under test (20a-20h); c) transmitting a power request for a test channel (4a-4h) to the control unit (27); d) checking whether the requested power is, in absolute terms, greater than the power transferable by the base converter (1a-1h); e) connecting the booster converter (2a, 2b) to one of the test channels (4a-4h) when the requested power is, in absolute terms, greater than the power transferable by the base converter (1a-1h); f) transferring the requested power via the base converter (1a-1h) and the booster converter (2a, 2b).

18. Method according to claim 17, wherein the power request is sent to the control unit (27) at least 1µs, preferably at least 100µs, prior to providing the power.