Multi-Channel Generator with PMG Exciter for Voltage Regulation
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Solution Overview
Problem
Variable frequency generators face challenges in voltage regulation due to sudden load changes and rotational speed variations, leading to unpredictable output voltage, and existing systems require complex field regulation and exciter control.
Innovation Solution
A generator system with a multi-channel architecture incorporating a permanent magnet, rotating rectifier, and main field rotating power converters, where high-side and low-side switches control the main field winding current to regulate output voltage, utilizing a generator control unit for feedback-based pulse width modulation to maintain voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a belt-type interface is used between prime mover shaft and generator shaft, then mechanical energy transmission is simplified, but sudden load changes cause sudden changes in generator speed leading to voltage instability
Solution Approach 1:
The patent implements a control system that continuously monitors generator output voltage and adjusts the exciter field current accordingly. The controller receives voltage feedback from the generator terminals and modulates the exciter firing angle to maintain stable voltage output despite speed variations from belt-driven prime movers.
Solution Approach 2:
The patent changes the exciter field current parameter dynamically to compensate for speed variations. By adjusting the exciter field current in response to detected voltage deviations, the system maintains stable generator output voltage even when generator speed fluctuates due to belt interface elasticity.
2Reliability
If a field regulated exciter is used to control generator output voltage, then voltage regulation capability is improved, but system complexity and control difficulty increase
Solution Approach 1:
The patent extracts the field regulation function from the exciter system by using a separate control circuit that directly modulates the exciter field current through controlled rectification. This separates the voltage regulation control logic from the exciter mechanism, simplifying the overall system architecture while maintaining regulation capability.
Solution Approach 2:
The patent replaces mechanical field regulation mechanisms with an electronic control system using solid-state rectifiers and firing angle control. This substitution eliminates complex mechanical linkages and provides more reliable, maintenance-free voltage regulation through electronic modulation of exciter field current.
3Device complexity
If permanent magnets are used in the generator, then construction is simplified and reliability is improved, but output voltage cannot be regulated without additional field control mechanisms
Solution Approach 1:
The patent introduces an exciter system as an intermediary between the permanent magnet generator and the load. The exciter provides a controllable magnetic field that interacts with the permanent magnet rotor, enabling voltage regulation while preserving the simplicity of permanent magnet construction in the main generator.
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 effectively regulates output voltage by independently controlling each channel, reducing sudden voltage fluctuations and simplifying control by eliminating the need for a field-regulated exciter, thereby enhancing voltage stability and control simplicity.
Implementation Method 1
A permanent magnet generator (PMG) utilizes permanent magnets to generate a constant magnetic field, which is rotated via the mechanical energy supplied by a prime mover such that the rotating magnetic field interacts with the stator coils to provide an output voltage
Implementation Method 2
The AC voltage provided by the permanent magnet portion is rectified and selectively applied to the exciter field winding
Implementation Method 3
The exciter field current interacts with the rotating exciter armature windings to provide AC voltage. A rotating rectifier rectifies the AC voltage and supplies the DC voltage to a main field winding on the rotating portion of the main generator section
Data Source
Figure 1
Figure 1
AI summary
A generator system includes a generator 52 having a stationary portions 60 and a rotating portion 61. The generator includes a permanent magnet based exciter with permanent magnets 62 disposed on the stationary portion. A first channel 98 includes a first main field winding 72 and a first main field power converter 78 disposed on a rotating portion. The first main field power converter selectively delivers voltage from the exciter winding to the first main field winding. A second channel 100 includes a second main field winding 74 and a second main field power converter 80 disposed on the rotating portion. The second main field power converter selectively delivers voltage from the exciter winding to the second main field winding. A generator control unit 54 is connected to the first channel and the second channel, The generator control unit monitors an output voltage at each of the first channel and the second channel and generates the first and second control signals based on the output voltage.