Generator Voltage Ripple Reduction via Power Converter Control
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Solution Overview
Problem
Internal combustion engine rotational nonuniformity causes undesirable voltage ripples in generator output, particularly at low speeds, due to the slow response of rotor windings and exacerbated by permanent magnets, which existing methods fail to adequately address.
Innovation Solution
Implementing an electrical freewheeling system that controls the commutation angle of power converters with controllable switching elements to manage generator current, reducing voltage ripples by decreasing current at maximum rotational speed and increasing it at minimum speed, using the generator rotational speed, voltage, and exciter field position as input variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field controller regulation is used to control generator output voltage, then voltage stability is improved, but response speed deteriorates due to rotor time constant
Solution Approach 1:
The patent introduces a power converter with controllable switching elements as an intermediary between the generator and the electrical system. This power converter acts as a mediator that can rapidly adjust the output voltage by controlling the switching elements, thereby decoupling the slow rotor response from the voltage regulation task while the field controller maintains overall voltage stability.
2Loss of energy
If permanent magnets are added for leakage flux compensation, then generator efficiency is improved, but voltage ripple worsens due to steeper power characteristic curve
Solution Approach 1:
The patent implements a control method that uses feedback from the generator's operating conditions (rotational speed, voltage, position of exciter field) to dynamically adjust the commutation angle of the power converter. This feedback mechanism compensates for the steep power characteristic curve caused by permanent magnets, reducing voltage ripple while maintaining the efficiency benefits of leakage flux compensation.
3Speed
If stator-side regulation via power converter is implemented, then response speed is improved, but device complexity worsens
Solution Approach 1:
The patent designs the power converter with controllable switching elements to perform multiple functions: it serves as a rectifier for converting AC to DC, as a voltage regulator for reducing ripple, and as a means for stator-side control. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving fast response speed for voltage regulation.
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 minimizes voltage ripples by short-circuiting a portion of the current within the power converter, reducing output ripples below acceptable thresholds, especially in the near-idling range, and allows for efficient operation of generators as motors or starters.
Implementation Method 1
a generator (10) having a stator winding (11) and a rotor winding (12)... the current through the rotor winding (12) is used as a manipulated variable for regulating the desired output voltage
Implementation Method 2
the current level on the stator side may be regulated via targeted control of the switching elements or rectifier elements... Control voltage fluctuations in the vehicle electrical system are minimized
Data Source
AI summary
A method for reducing a ripple, caused by rotational nonuniformity of an internal combustion engine, in the output voltage of a generator which is driven by the internal combustion engine is provided. The generator has a stator winding, a rotor winding, a field controller, associated with the rotor winding, for regulating the output voltage of the generator, and a downstream power converter having controllable switching elements. To reduce the voltage ripple, the output voltage of the generator is regulated on the stator side by appropriately controlling the switching elements of the power converter.