Validation of High-Voltage Vehicle SystemsFast and Precise Measurement
Validation of High-Voltage Vehicle Systems
Electrification of the powertrain is leading to new and more stringent safety engineering requirements. For example, high-voltage components are subject to national and international regulations such as ECE-R 100 and standards like ISO 7637-4. At the same time, in-vehicle systems must also be functional, safe, robust, compact, lightweight and efficient. These requirements lead to high system complexity.
The overall system consists of components which are developed, in parallel, by different suppliers and development departments. Such components for the high-voltage (HV) vehicle system include the electric motor, battery, inverter, on-board charger, electric heater, electric compressor and DC/DC converter.
Both the individual components and the overall system must be verified and validated. In the early phases of development, this is done by simulation and on the test bench. However, a final release cannot be issued until the DUT is tested in its real environment.
The electrical system of an electric vehicle is significantly more complex than that of a conventional vehicle due to the two DC networks. The layout of the powertrain, the charging components and the HV consumers present entirely new requirements. They can vary from vehicle to vehicle depending on the electrical system topology and the voltage levels in the low-voltage and high-voltage systems that can extend up to 800 V. There are also varying requirements for load and dynamic response.
Validation of the HV electrical system involves very high requirements for sampling rate, HV safety and scalability of the measurement system used. The entire HV electrical system is instrumented and sampled at numerous points to assure that all HV system components perform their tasks and are operational in any conceivable driving situation.
These measurements must be made at very high sampling rates to acquire and quantify additional effects such as voltage peaks caused by line inductances, abrupt load alternation or capacitive coupling of fast switching processes in the power electronics. To analyze the causes of errors, all of these measurements must be time-synchronous and must not originate from different measurement systems that are not coupled. The ECUs in the vehicle, besides transmitting measurement parameters on the various vehicle buses, also provide information that is relevant and important for validation. That is why this information is also measured time-synchronously and needs to be incorporated into the evaluation of overall behavior.
Of course, the measuring instruments used must be suitable for HV to prevent any sorts of hazards to users in the service garage or in vehicle operation. Validation conducted under extreme driving and operating conditions ensures that the specific design of the HV electrical system in the vehicle has sufficient reserves without imposing any limitations on vehicle operation. The road tests conducted for this purpose can also examine the effects of two electric motors with superimposed interferences.
Since voltage peaks are very fast and sporadic, and the tester needs this precise information during the drive, the measurement software must meet an additional, special requirement. It must be able to evaluate the signals online, e.g., to calculate triggers for starting recording. The trigger condition might, for example, be derived from the voltage signal over time, to detect whether a maximum value is exceeded in fast voltage changes.
The measurement system must, of course, be able to record all data (HV signals, ECU measuring signals and calculated signals) for later detailed analysis or for documentation purposes.
A perfectly tuned tool chain of HV-safe measurement modules, ECU measurement technology and software for synchronized online acquisition of measurement data and data analysis during the road tests:
- Vector and CSM offer a modular, HV-safe measurement system for simultaneously acquiring measurement signals from the HV network and ECUs.
- The HV Breakout Modules (HV BM) from CSM are specially designed for decentralized and safe measurement applications on cables conducting high voltage (HV). Various HV BM shunt modules are available for the best possible adaptation to the HV network. They are permanently installed and are available over a nominal current range from 50 A to 800 A.
- Current and voltage are acquired synchronously in the HV BM at a data rate of up to 1 MHz (1 μs). The precision of current and voltage measurement is better than 0.2%.
- The powerful and flexible Vector network interfaces enable users to acquire information on ECUs over all available bus technologies and protocols.
- To validate the overall system, many more measurement points are necessary; their number is a function of the number of HV components used. These measurement points are used to check the efficiency and dynamic response of a component such as the electric motor. In a passenger car, the number of measurement points ranges from 10 to 20, and in heavy-duty vehicles there may be more. The signals are acquired synchronously by vMeasure exp software from Vector, and they can be processed directly online, e.g., to trigger specific events or to calculate other signals that are relevant to the test.
Innovative, fast, precise and flexible measurement for validating and verifying on-board HV electrical systems in the laboratory and in road tests:
- Like all measurement modules from CSM, the BM modules are also small, robust and designed to be mounted directly in the vehicle. This enables data acquisition right at the measuring point. It is not necessary to provide additional current sensors, long cables or measuring instruments in the vehicle. This not only saves time and reduces risk; it also shortens the measurement chain and improves the quality of the measurement.
- Synchronous acquisition of all signals, including from ECUs and vehicle bus systems.
- The powerful test software vMeasure exp executes complex mathematical operations on channels during the measurement. In addition to recording the measurement signals that are acquired directly, it is also possible to simultaneously filter or derive signals. They are also logged time-synchronously, or they are provided to the measurement system as trigger signals.
- The user can measure the dynamic current and voltage responses directly in the vehicle electrical system and at consumers, obtaining immediate feedback during the road tests. This makes testing and later in-depth analysis much more efficient.