Phased Activation Method for Electric Machine Neutral Point Current Control
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Solution Overview
Problem
In vehicles with multiple on-board electric sub-systems, existing systems face challenges in efficiently transferring power and managing neutral point currents, leading to high current ripples and torque generation in the rotor, which limits the operating range and efficiency of electric machines.
Innovation Solution
The implementation of a phased activation method for the electric machine's inverter controller, utilizing both leakage and main inductance to smooth neutral point currents, along with a phase-shifted pulse pattern generation, allows for reduced current ripples and expanded operating ranges by minimizing torque generation and optimizing power transfer between sub-systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC chopper converter is used to transfer electric power between on-board electric sub-systems, then power transfer capability is improved, but current ripples and device complexity increase
Solution Approach 1:
The electric machine is designed to perform multiple functions: it acts as both a propulsion motor and a power transfer device between on-board electric sub-systems. The neutral point connection enables the machine to function as a bidirectional power converter, eliminating the need for separate DC chopper converters and reducing overall system complexity while maintaining power transfer capability
Solution Approach 2:
The invention merges the power transfer function with the electric machine's existing propulsion function. By connecting the neutral point to the second on-board electric sub-system, the machine combines motor operation with power conversion capabilities, integrating multiple functions into a single device rather than using separate components
2Device complexity
If conventional inverter control is used, then control simplicity is maintained, but neutral point current ripples increase
Solution Approach 1:
The invention employs periodic pulse pattern generation with phase shifts for different inverter switches. By systematically varying the switching patterns in a periodic manner and introducing phase shifts between different phases, the control method achieves neutral point current smoothing through constructive and destructive interference of current waves, reducing ripples without complex control algorithms
Solution Approach 2:
The control method changes the switching parameters of the inverter by implementing phase-shifted pulse patterns. By adjusting the timing and duration of switch activation in a phased manner, the system modifies the current waveform characteristics to minimize neutral point current ripples while maintaining effective power transfer
3Power
If the electric machine operates with high power demand, then power output is improved, but torque generation in the rotor increases
Solution Approach 1:
The invention extracts the power transfer function from the traditional motor function. By utilizing the neutral point connection and implementing phased activation control, the system separates the electromagnetic torque production from the power conversion function, allowing high power transfer between on-board systems without generating unnecessary torque in the rotor
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
This approach effectively reduces current ripples in neutral point currents by over 50%, enhances efficiency, and extends the operating range of electric machines by leveraging both leakage and main inductance for current smoothing, without generating additional torque in the rotor.
Implementation Method 1
the inverter (2) for converting a DC voltage into an AC voltage
Implementation Method 2
a phased activation method which utilizes both the leakage inductance and the main inductance of the machine for smoothing the neutral point current
Implementation Method 3
the electric machine, which can also be operated as an engine in a vehicle having an electrified drive train, functions as an electric energy source or as an energy sink in the vehicle
Data Source
AI summary
A vehicle is configured with an N-phase electric machine, a first on-board electrical sub-system and a second on-board electrical sub-system. The electric machine includes a rotor and a stator system, wherein the first onboard electrical sub-system includes an inverter and the stator system is linked to the inverter. The electric machine can be operated using an inverter controller on the principle of a field-oriented control system, so that the electric machine is linked to a control unit, wherein the inverter can be controlled by the control unit, and the control unit uses a phased activation method to control the inverter.