DC-Link Ramp-Up Control for Thyristor Current Spike Suppression
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Solution Overview
Problem
Existing variable speed drives (VSDs) face challenges in meeting harmonic regulation standards while maintaining a compact, lightweight design, as traditional solutions with sizable capacitors and inductors increase size, weight, and cost, and C-Less Links with thyristors cause high current spikes and oscillations.
Innovation Solution
Implementing a non-linear variation of firing angles for thyristors in the rectifier bridge to smooth the current ramp-up, reducing current peaks and oscillations without additional components, allowing for a mix bridge and C-Less Link topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sizable capacitors and inductors are used to meet harmonic regulation standards, then harmonic compliance is improved, but device size, weight, and cost increase
Solution Approach 1:
The patent changes the control parameters of the thyristors by implementing a non-linear variation of firing angles over time, specifically using a polynomial function (e.g., second-order polynomial) to control the thyristor conduction angle. This parameter change allows the system to meet harmonic regulation standards without requiring sizable passive components, thereby reducing device weight while maintaining compliance.
2Weight of stationary object
If C-Less Link topology with thyristors is used to reduce size and weight, then device compactness is improved, but current spikes and oscillations increase
Solution Approach 1:
The patent applies dynamic control by varying the thyristor firing angles non-linearly over time during the voltage ramp-up phase. Instead of a static or linear control approach, the system dynamically adjusts the conduction angle using a polynomial function, which smoothly controls the current ramp-up and eliminates current spikes and oscillations while maintaining the compact C-Less Link topology.
Solution Approach 2:
The patent implements preliminary action by pre-defining a non-linear polynomial function for the thyristor firing angle control before the voltage ramp-up occurs. This pre-planned control strategy ensures that the current ramp-up is smoothly managed from the beginning, preventing current spikes and oscillations before they can occur, rather than reacting to them after they appear.
3Device complexity
If linear variation of thyristor firing angles is used, then control simplicity is maintained, but current oscillations and peaks occur
Solution Approach 1:
The patent changes the control parameter from a linear variation to a non-linear polynomial variation of the thyristor firing angle. This parameter change, while slightly increasing control complexity, effectively eliminates current oscillations and peaks by smoothly controlling the current ramp-up, demonstrating that the added complexity is justified by the significant improvement in current quality.
Data Source
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AI summary
Examples include a computer-implemented method for controlling a ramp-up of a voltage in a DC-link, a computer-readable storage medium, a variable speed drive, and a system comprising a variable speed drive configured to carry out the method.