Variable Speed Windmill Pulse Width Modulation Timing Synchronization
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Solution Overview
Problem
Wind power plants with variable speed windmills face challenges in transmitting smooth alternating current to the electricity network due to the use of pulse width modulated frequency converters, resulting in voltage and amperage discontinuities and increased power absorption by filters, which reduces net transmission and profitability.
Innovation Solution
A method where windmills with variable rotational speed synchronize the timing of pulse width modulated alternating current pulses to achieve a smoother current output, using time-delayed feeding and GPS signals for calibration, allowing for smaller RCL filters and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If RCL filters are used to smooth the alternating current from pulse width modulated frequency converters, then the current quality is improved, but power is absorbed from the network reducing net transmission
Solution Approach 1:
The patent divides the power generation system into multiple independent generating units, each with its own pulse width modulated frequency converter. By segmenting the system this way, the discontinuities from individual converters are distributed and smoothed when combined, reducing the need for large RCL filters and thereby reducing power absorption from the network.
Solution Approach 2:
The patent employs pulse width modulation with periodically switched transistors to convert DC to AC. The periodic switching action allows for controlled generation of AC current with adjustable frequency and amplitude, enabling multiple generators to be synchronized and combined to produce smoother overall current output.
2Manufacturing precision
If RCL filters are used to smooth the alternating current, then the current quality is improved, but the filter size increases entailing higher costs
Solution Approach 1:
By dividing the system into multiple smaller generating units with independent converters, the patent reduces the burden on individual filtering components. The combined output of multiple units naturally smooths the current, allowing for smaller, less expensive RCL filters compared to a single large-scale system.
Solution Approach 2:
The patent merges the outputs of multiple generating units with slightly different frequencies and phase relationships. This combining effect naturally smooths the overall current output, reducing the filtering requirements and allowing for smaller RCL filters.
3Productivity
If pulse width modulated frequency converters are used to convert DC to AC, then the conversion efficiency is improved, but voltage and amperage discontinuities occur
Solution Approach 1:
The patent segments the power conversion function across multiple independent frequency converters, each handling a portion of the total power. This segmentation allows each converter to operate efficiently while the combined output smooths out discontinuities, maintaining both conversion efficiency and current stability.
Solution Approach 2:
Each generating unit operates with its own optimized pulse width modulation parameters, allowing local adjustment of switching frequencies and duty cycles. This local optimization maintains high conversion efficiency for each unit while the aggregate output achieves smooth current delivery.
Data Source
AI summary
A method and a wind power plant are provided for smoothing alternating electric current from a number of power generators are provided. Generators are electrically connected to an electric network. Each power generator includes a transformer with pulse width modulation for converting direct current to pulse width modulated alternating current for feeding to the network. The time for feeding the pulses of the pulse width modulated alternating current is different for each generator in order to achieve a more even alternating current as a sum of respective outputs of alternating current from the generators.