Active Grid Converter Control for Flicker-Free Load Changes
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Solution Overview
Problem
Existing power grid systems face challenges in preventing flicker emissions due to load changes, which cause harmful voltage fluctuations affecting lighting equipment and worker health, especially in industrial settings, where current solutions are complex and uncertain.
Innovation Solution
The method involves determining the grid impedance and adjusting the active grid converter to limit permissible grid current changes, using a DC link capacitor as an energy buffer to compensate for load changes, and generating warnings for additional capacitance when limits are approached, ensuring flicker emissions are prevented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter adjusts the DC link voltage to a constant value, then the power consumption of the load is stabilized, but the grid current changes directly reflect load changes causing voltage fluctuations and flicker emissions
Solution Approach 1:
The invention changes the control parameter from constant DC link voltage to controlled DC link voltage variations. The converter deliberately allows DC link voltage to fluctuate within permissible limits, transforming the voltage parameter dynamically to compensate for load changes and prevent flicker emissions while maintaining power stability.
2Object-generated harmful factors
If the grid impedance is low to ensure permissible voltage changes, then flicker emissions are reduced, but the design becomes complex and uncertain
Solution Approach 1:
The invention implements a feedback control mechanism where the converter continuously monitors grid impedance and adjusts the DC link voltage accordingly. The control system uses feedback from grid conditions to dynamically determine permissible voltage variations, eliminating the need for complex design calculations and simplifying the overall system while ensuring flicker compliance.
3Object-generated harmful factors
If the converter limits grid current changes to prevent flicker, then voltage fluctuations are reduced, but the DC link voltage must vary which requires additional energy storage
Solution Approach 1:
The invention makes the DC link capacitor serve multiple functions: it provides its traditional energy storage function for voltage stabilization while simultaneously acting as a buffer to absorb load changes and prevent flicker emissions. This multi-functionality eliminates the need for additional energy storage components, as the existing capacitor handles both voltage regulation and flicker prevention.
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 maintains permissible voltage changes, preventing flicker emissions and allowing devices to be connected to power grids without causing health hazards, simplifying the design of electric drives and reducing customer complaints.
Implementation Method 1
The at least one DC link capacitor is used as an energy store to compensate for preferably small load changes
Data Source
AI summary
A converter includes a load converter for supplying an electric load, an active grid converter connected at a connection point to an electric power supply grid, and an intermediate circuit supplied by the active grid converter with an intermediate circuit voltage. Flicker emissions of the active grid converter on the power supply grid can be prevented by controlling the active grid converter so that a grid current change at the connection point maintains a maximum permissible change of effective values of successive voltage half-cycles of a voltage at the connection point by taking into account a grid impedance determined from a power grid analysis of the active grid converter at the connection point.