Two-Winding Induction Generator Control for Stable Auxiliary DC Voltage
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Solution Overview
Problem
In a two-winding induction generator, maintaining a stable DC voltage on the auxiliary winding side is challenging due to excessive or deficient excitation currents when the load on the auxiliary winding varies, especially at low rotational speeds, leading to inefficiencies and inability to support the load.
Innovation Solution
An electrically driving system with a controller that computes d-axis current command values for both windings, using a single power converter on the auxiliary winding side, to stabilize DC voltage by adjusting current based on rotational speed and load demands, incorporating a rectifier, travelling inverter, and power converter to manage voltage and current across both windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If excitation current for the main winding is determined only depending on the rotational speed of the rotating electric machine, then the control is simplified, but the excitation amount may become deficient when the load on the auxiliary winding increases
Solution Approach 1:
The controller computes a second d-axis current command value based on the rotational speed and electric power demanded by the accessory, and controls the power converter to bring the d-axis current value into conformity with this command value. This feedback mechanism ensures the excitation amount is adjusted according to actual load conditions, preventing deficiency while maintaining manageable control complexity through systematic computation.
Solution Approach 2:
The system changes the control parameter from solely rotational speed-based excitation current determination to a dual-parameter approach considering both rotational speed and accessory power demand. This parameter change enables the excitation amount to adapt to varying load conditions, resolving the contradiction between simplified control and adequate excitation.
2Reliability
If the excitation amount becomes deficient, then the DC voltage on the main winding side cannot be maintained, but increasing excitation current may cause excessive excitation and reduce efficiency
Solution Approach 1:
The controller dynamically adjusts the d-axis current command value based on real-time conditions (rotational speed and accessory power demand). This dynamic control allows the excitation amount to be optimized for each operating state, maintaining DC voltage stability when needed while avoiding excessive excitation that would reduce efficiency, thus resolving the contradiction between voltage stability and energy efficiency.
Solution Approach 2:
The system changes the excitation control parameter from a fixed rotational speed-based value to a dynamically computed value that considers both rotational speed and accessory power demand. This parameter adaptation enables the system to maintain adequate DC voltage while optimizing electric generation efficiency by avoiding excessive excitation.
3Device complexity
If a single power converter is provided on the auxiliary winding side, then the device complexity is reduced, but it becomes challenging to maintain stable DC voltage regardless of rotational speed and load changes
Solution Approach 1:
The single power converter on the auxiliary winding side is designed to perform multiple functions: it controls voltages across both the main winding and auxiliary winding, converts AC voltage from the auxiliary winding to DC voltage for the accessory, and responds to control signals that consider both main machine and accessory conditions. This multi-functionality allows one converter to maintain DC voltage stability under varying conditions, reducing device complexity while preserving reliability.
Solution Approach 2:
The controller computes the second d-axis current command value based on feedback from rotational speed sensors and accessory power demand, then controls the power converter to maintain stable DC voltage on the auxiliary winding side. This feedback control enables a single power converter to adapt to varying operational conditions and maintain voltage stability without requiring additional converters.
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
The system maintains consistent DC voltage on the auxiliary winding side, regardless of rotational speed and load changes, enhancing efficiency and ensuring stable power supply to accessories.
Implementation Method 1
a rectifier that is connected to the main winding and converts an alternating-current voltage generated by the main winding to a first direct-current voltage
Implementation Method 2
a travelling inverter that is connected to the rectifier and converts the first direct-current voltage to an alternating-current voltage to be supplied to the travelling motor
Implementation Method 3
a power converter that is connected to the auxiliary winding, controls voltages across the main winding and the auxiliary winding, and converts an alternating-current voltage generated by the auxiliary winding to a second direct-current voltage to be supplied to the accessory
Implementation Method 4
a generator that has a stator including a main winding and an auxiliary winding
Data Source
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AI summary
An object of the present invention is to provide an electrically driving system capable of maintaining a DC voltage on an auxiliary winding side with a single power converter provided on the side of the auxiliary winding, regardless of the rotational speed of a two-winding induction generator and the magnitude of a load on the auxiliary winding side. To achieve the object, the controller computes a first d-axis current command value for the auxiliary winding on the basis of the first DC voltage and a command value for the first DC voltage, computes a second d-axis current command value for the auxiliary winding on the basis of a rotational speed of the generator and electric power demanded by the accessory, controls the power converter so as to bring a d-axis current value of the auxiliary winding into conformity with the first d-axis current command value in a traction state, and controls the power converter so as to bring the d-axis current value of the auxiliary winding into conformity with the second d-axis current command value in a retarded state or an idling state.