Highly Integrated Power Electronic Systems
Semikron Danfoss Power Electronics for Electromobility
Semikron Danfoss has offered integrated power electronic systems for vehicle applications for more than 25 years and can build on many years of experience. Initially just power silicon and gate drivers in custom designed enclosures, these systems have evolved to become more highly integrated, now including control electronics and vector control software. To date, a total of more than 2 million highly integrated fork-lift inverter systems have been manufactured at Semikron Danfoss. Furthermore, 100,000 400V and 800V inverters have been built for use in electrified buses and trucks. The timeline below shows Semikron Danfoss vehicle systems shipped to customers in the last three decades
Requirements for Power Electronic Systems in Vehicle Applications
Flexible, highly efficient power electronics are a central requirement to make electromobility a success. To achieve maximum power density, electrical losses and thermal resistances must be kept to a minimum. Maximum component integration is required while also being affordable. The EMC requirements stipulated in the European EMC Directive for registered vehicles must be adhered to. The interface for connection to the master controller in the vehicle must be flexible enough to facilitate adaptation to different conditions. For example, the 3-phase IGBT-based inverter SKAI 2 HV (shown above) achieves a power density of up to 20 kVA/liter at a nominal efficiency of >98%.
SKAI – Power Electronic Building Blocks
All SKAI power electronic systems are based on the same architectural principles depicted below. The core of these systems is the power section comprising the semiconductor switches, the DC-link capacitor bank, sensors for phase currents, DC-link voltage and temperature sensors on the ceramic substrate, as well as EMI filtering. The systems are complete with gate driver, protection functions for over-current, over-voltage and over-temperature, isolated power supplies for all required internal voltages and a micro-controller.
Converters from the SKAI product family from Semikron Danfoss have been optimized for use in hybrid and full electric vehicles. The SKAI systems boast a high level of integration and offer major advantages over comparable systems. They are developed in line with the latest standards, allowing short time-to-market and low development costs. The SKAI systems are supplied as standard platforms with low-voltage MOSFETS or high-voltage IGBTs as the silicon base. SKAI systems can also be developed to meet individual customer specifications.
Optional Control Software SKAIwareTM
The interface between control unit and master controller in the vehicle comes as either a CAN bus interface or, alternatively, as a switching signal interface. Also available is the motor control software SKAIwareTM, which is based on field-oriented control. SKAIwareTM guarantees stable control of the electric motor up to the field-weakening range and thus enables the implementation of dynamic and efficient traction drives and generator solutions. SKAIwareTM normally receives input from a central controller via CAN and accurately converts this into speed or torque.
The SKAIwareTM software solution, developed in compliance with the MISRA-C standard and adapted to the SKAI hardware, is designed to control interior permanent-magnet and surface-mount permanent-magnet synchronous motors, as well as three-phase induction motors. Parameters for different types of motors can be selected using this software. SKAIwareTM includes features such as temperature monitoring in motors and inverters, battery deep discharge protection, overvoltage protection for DC energy recovery, CAN communication per CANopen, software update via CAN boot loader in the vehicle network, etc. Users can also choose to use their own individual control software if they prefer. In certain cases, the controller hardware can also be adapted to specific requirements.
For the design of reliable electronic or mechatronic components, it is important to know the operating conditions to determine the effects of aging and failure mechanisms. In addition to the extreme environmental temperatures, there are the semiconductor temperature excursions and their durations in operation ("Mission Profile").
Based on the provided profile, the overall service life, and the impact of critical load variations can be determined. With this detailed data, optimized motor control is easily achievable.For those designing a electric drive solution, Semikron Danfoss can parameterize the generic SKAIwareTM motor control software for a customer-specific motor. It is also feasible to upload customer specific control software before delivery.