Active Damping of Current Harmonics in Multi-Level Converters
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Solution Overview
Problem
Converter circuits with weakly damped oscillating circuits suffer from undesired oscillations and current distortions, which existing methods fail to effectively dampen, leading to inefficiencies and reliability issues.
Innovation Solution
The method involves controlling power semiconductor switches in converter circuits using control signals formed from reference signals and damping signals, where the damping signals are derived from measured currents and resistance values, effectively attenuating currents by simulating a voltage drop across an ohmic resistor, and utilizing local calculation units to ensure redundancy and reduce transmission overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If freely selectable time periods for switching operations are used to dampen oscillations, then oscillation damping is achieved, but current distortions and undesired oscillations persist
Solution Approach 1:
The invention introduces feedback control by measuring the actual current through the partial converter system and using this measurement to generate a damping signal. The damping signal is formed from the measured current and a predeterminable resistance value, creating a closed-loop system that continuously adjusts the control signal to counteract oscillations and distortions, thereby resolving the contradiction between achieving oscillation damping and eliminating current distortions.
Solution Approach 2:
The invention changes the control parameter by adding a damping signal component to the control signal that is proportional to the measured current and a resistance value. This parameter modification allows the system to actively counteract oscillations and distortions by adjusting the effective resistance in the control loop, thereby simultaneously achieving oscillation damping and reducing current distortions.
2Device complexity
If central calculation unit generates all control signals, then system coordination is simplified, but transmission overhead increases and redundancy is reduced
Solution Approach 1:
The invention segments the control signal generation function by distributing local calculation units to individual switching cells or groups of cells. Each local unit independently generates control signals for its associated cells using locally available measurements, eliminating the need for continuous central control signal transmission. This segmentation reduces transmission overhead while maintaining system coordination through the unified damping control strategy.
Solution Approach 2:
The invention enables self-service control by allowing local calculation units at each switching cell to autonomously generate their own control signals based on local current measurements and the damping control algorithm. This decentralized self-service approach eliminates transmission overhead for control signals while maintaining system-wide coordination through the common damping principle applied at each local unit.
3Loss of information
If measurement systems are centralized, then system-wide monitoring is achieved, but reliability decreases due to single point of failure
Solution Approach 1:
The invention segments the measurement and control functions by placing local calculation units at distributed locations throughout the converter system. Each local unit independently measures current and generates control signals for its associated switching cells. This segmentation creates redundant measurement paths, so if one measurement system fails, others continue to operate, thereby improving reliability while still achieving system-wide monitoring through the distributed architecture.
Solution Approach 2:
The invention applies local quality by enabling each local calculation unit to perform measurements and control functions independently at its specific location in the system. This local autonomy creates multiple independent measurement channels, improving reliability through redundancy while collectively achieving system-wide monitoring coverage through the distributed arrangement of local units throughout the converter.
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 actively damps specific oscillation components of currents, enhancing the stability and reliability of converter circuits by effectively attenuating currents and maintaining redundancy even in case of measurement failures, thus improving overall performance.
Implementation Method 1
The effect of the respective damping signal corresponds to a voltage drop across an ohmic resistor in the associated partial converter system
Data Source
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AI summary
The method involves controlling power semiconductor switches in switching cells in a sub-converter system by a control signal (S1). Power semiconductor switches in switching cells in another sub-converter system (S2) is controlled by another control signal. The former control signal and the latter control signal are formed from a respective damping signal with the respective sub-converter system, where the damping signal is formed from a measured current through the respective sub-converter system and a predeterminable resistance value.