Dynamic Firing Angle Control for Thyristor Bridge Converters
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Solution Overview
Problem
Current control solutions for load-commutated inverters in current source converters are conservative and do not fully account for operating conditions, leading to inefficiencies and harmonic content issues in electrical drives.
Innovation Solution
A method for determining a dynamic upper bound for the firing angle of thyristor bridges based on voltage and current measurements, ensuring the firing angle is maximized while preventing misfiring and optimizing power factor, harmonic content, and drive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a precomputation approach with lookup tables is used to determine firing angles, then the control system is simple to implement, but the operating conditions are not fully taken into account and a significant buffer is incorporated reducing efficiency
Solution Approach 1:
The patent transitions from static precomputed lookup tables to dynamic real-time calculation of firing angles. The controller continuously computes optimal firing angles based on current operating conditions (voltage, current, power factor requirements), eliminating the need for conservative buffered values and enabling adaptive optimization across all operating points.
Solution Approach 2:
The invention changes the control parameters from fixed lookup table values to dynamically calculated values based on real-time measurements. The firing angles are adjusted continuously according to actual voltage, current, and power factor conditions, allowing the system to operate at optimal efficiency points rather than conservative pre-determined values.
2Reliability
If conservative firing angle values are used to guarantee operation under all conditions, then reliability is improved, but power factor and harmonic content are not optimized
Solution Approach 1:
The system implements closed-loop feedback by continuously measuring voltage and current and using these measurements to adjust firing angles in real-time. This feedback mechanism ensures reliable operation while simultaneously optimizing power factor and minimizing harmonic content, as the controller adapts to actual operating conditions rather than relying on conservative fixed values.
Solution Approach 2:
The patent employs dynamic adjustment of firing angles based on real-time operating conditions. Rather than using static conservative values, the system continuously adapts the firing angles to maintain optimal performance while ensuring reliable operation across all conditions, thereby reducing harmonic content and improving power factor.
3Object-generated harmful factors
If the firing angle is maximized to optimize power factor, then power factor is improved, but misfiring may occur reducing reliability
Solution Approach 1:
The patent calculates the maximum possible firing angle that can be applied without causing misfiring, based on real-time commutation window measurements. By determining and applying this optimal partial action (the maximum safe firing angle), the system improves power factor while maintaining reliability, avoiding both conservative under-utilization and excessive action that would cause misfiring.
Solution Approach 2:
The system uses feedback from voltage and current measurements to dynamically determine the maximum safe firing angle. This feedback mechanism allows the controller to push the firing angle to its optimal limit without exceeding the misfiring threshold, thereby improving power factor while maintaining reliable operation.
4Device complexity
If fixed firing angles are used from lookup tables, then device complexity is reduced, but adaptability to different operating conditions is limited
Solution Approach 1:
The control system performs self-service by automatically calculating optimal firing angles based on its own measurements of voltage, current, and operating conditions. Rather than relying on pre-programmed lookup tables, the controller independently determines the appropriate firing angles for each operating point, providing full adaptability without increasing device complexity.
Solution Approach 2:
The invention changes from fixed parameters stored in lookup tables to dynamically calculated parameters based on real-time measurements. This allows the system to adapt to any operating condition while maintaining a relatively simple control structure that only requires basic voltage and current sensing and calculation capabilities.
Data Source
AI summary
A thyristor bridge of an electrical converter is connected to at least one DC link and including at least one phase leg for each output phase and each phase leg being composed of two series-connected thyristor arms. The thyristor arms of a thyristor bridge are cyclically switched by: determining an upper bound for a firing angle of a thyristor arm, wherein the upper bound is determined from voltage and current measurements; and determining a firing angle for the thyristor bridge, which firing angle determines a switching time of the thyristor arm, wherein the firing angle is determined, such that it is less or equal to the upper bound.