Power Electronic Box (PEB)
The abbreviation PEB stands for Power Electronic Box and refers to the control unit used in the E72 to activate and control the hybrid-specific components.
The PEB controls the high voltage electrical system in all operating conditions, the bidirectional energy flow of the electric machines, the speed and torque of the two electric machines and the electrical hybrid oil pump control unit (electrical motor pump inverter). The PEB has been developed as part of the hybrid co-operation along with GM, DaimlerChrysler (later Daimler and Chrysler) and is based in part on the developments of a predecessor project in which BMW did not participate. The manufacturer and developer of the PEB is Hitachi, Ltd., Automotive Systems Japan.
The PEB is the central bidirectional high voltage hybrid control unit, consisting of four microcontrollers (control units). These four control units are the HCP, MCPA, MCPB and EMPI.
During diagnostics, each control unit sends its signals individually, where the fault entries of the EMPI and MCP are stored in the fault memory of the HCP. The communication of the control units in the PEB with other control units in the vehicle takes place independently via the H-CAN and the H-CAN2.
The following are the functions of the four control units in the PEB:
- HCP: co-ordinates all central functions of the hybrid system, selects the gear, calculates the torque distribution between the combustion engine, electric machines, chassis and suspension and monitors the complete system.
- MCPA: calculates the control of electric machine A depending on the requirement of the HCP.
- MCPB: calculates the control of electric machine B depending on the requirement of the HCP.
- EMPI: controls the electric motor of the hybrid oil pump.
In addition to these four control units, the PEB contains the power electronics of the two impulse converters (AC/DC converters) to control the two electric machines, one impulse converter (AC/DC converter) to control the electrical hybrid oil pump control unit and a capacitor (1 mF) as the intermediate voltage circuit as well as the external hardware for all four control units.
Other functions:
- Control of the high voltage electrical system
- Bidirectional distribution and transfer of the energy between the electric machines of the drive system and the high voltage system
- Controlled discharge of the high voltage in the vehicle
- Filtering of the high voltage electrical system
- Insulation and insulation monitoring of the high voltage to earth
- Diagnostic functions and self-protection of the components
- Control of the electric machines in torque, speed
- Activation and control of the hybrid oil pump
- Pre-charge mode, which allows the high voltage system to be started
The energy operational strategy in the hybrid master control unit HCP continuously adjusts the energy distribution depending on the environmental conditions, vehicle condition and driver's choice. The most important input and control variable for the operational strategy is the state of charge of the high voltage battery.