Electromechanical Steering DC Bus Overvoltage Control
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Solution Overview
Problem
The operation of electric motors in generator mode in electromechanical steering systems can generate electrical currents that exceed the capacity of modern vehicle electrical systems to absorb, leading to potential damage and overvoltages, particularly in hybrid or electric vehicles with advanced electrical designs.
Innovation Solution
A method and system that utilizes the phase resistance of electric motors to convert generated currents back into energy, monitored by control units to maintain a stable DC bus voltage level, employing vector control to adjust the d-vector of the motor's rotor-related d/q system, and redundant motor configurations to manage excess energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If electric motors operate in generator mode to recover energy, then energy efficiency is improved, but electrical system stability deteriorates due to overvoltages and current feedback
Solution Approach 1:
The patent converts the harmful effect of generated currents in generator mode into a beneficial energy recovery process. When electric motors operate as generators, instead of allowing currents to feedback into the DC bus and cause overvoltages, the system redirects these currents through controlled resistance elements, transforming the potentially harmful regenerative current into useful energy dissipation and recovery.
Solution Approach 2:
The patent introduces intermediary components (resistance elements and control units) between the electric motors and the DC bus. These intermediaries manage the current flow from generators, preventing direct feedback into the electrical system while enabling controlled energy recovery, thus mediating between the generator mode operation and electrical system stability requirements.
2Device complexity
If conventional vehicle batteries are used to absorb generated currents, then electrical system simplicity is maintained, but adaptability to modern high-voltage electrical systems deteriorates
Solution Approach 1:
The patent creates a universal current management system that can handle both conventional 12V and modern 48V high-voltage electrical systems. The resistance elements and control architecture are designed to be voltage-agnostic, allowing the same basic structure to absorb and manage generated currents across different voltage platforms, thus providing multi-functionality and adaptability.
Solution Approach 2:
The patent enables adaptation to different voltage levels by changing key parameters of the current management system, including resistance values, power handling capacities, and control thresholds. This allows the system to be configured for conventional or high-voltage applications without fundamental redesign, achieving versatility through parameter adjustment.
3Loss of energy
If generated currents are allowed to feedback into the DC bus, then energy recovery is achieved, but component damage risk increases due to overvoltages
Solution Approach 1:
The patent applies preliminary anti-action by preemptively preventing harmful current feedback before it can cause overvoltages. The control system continuously monitors generator mode operation and activates resistance elements in advance to intercept and safely dissipate generated currents, preventing the harmful feedback effect from occurring in the first place.
Solution Approach 2:
The patent transforms the harmful regenerative current that would cause overvoltages into a beneficial energy recovery opportunity. By routing currents through controlled resistance elements, the system captures energy that would otherwise be wasted, converting a potentially damaging effect into a useful energy recovery mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively prevents damage from overvoltages by converting generated currents, maintaining stable DC bus voltage, and ensuring minimal impact on steering behavior and feel, while optimizing energy management.
Implementation Method 1
the at least one electric motor operates in either motor or generator mode depending on the driving situation
Implementation Method 2
the phase resistance of the at least one electric motor of the steering system is used to compensate for a regenerative direct current in the DC bus
Data Source
Figure 1~2
AI summary
The present invention relates to a method for operating an electromechanical steering system (1) in a motor vehicle, wherein the steering system (1) comprises at least one actuator (2, 3) with at least one electric motor (21, 31), wherein the at least one electric motor (21, 31) is connected to the vehicle's electrical system via a DC bus (40), and wherein the at least one electric motor (21, 31) is operated in motor mode or generator mode depending on the driving situation. At least one control unit (22, 32) of the steering system (1) monitors the actual voltage level of the DC bus (40) with respect to whether it exceeds a target voltage level of the DC bus (40) by a predetermined value, and upon detection of an exceedance by a first predetermined value, the actual voltage level is reduced by converting electrical energy in at least one of the electric motors (21, 31).Furthermore, the invention relates to an electromechanical steering system (1) designed to be operated according to such a method.