Delta-Configuration Converter With Harmonic Current Injection
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Solution Overview
Problem
Converters with a delta configuration experience energy pulsation during regulation and control, which is not effectively managed by existing methods, limiting their ability to reduce energy swing and efficiently compensate for reactive power, harmonics, and flicker.
Innovation Solution
A converter with three series circuits in a delta configuration, each comprising at least two series-connected switching modules, controlled to include additional current harmonics that circulate within the converter, reducing energy swing without external interference, and a harmonic determination module to optimize these harmonics based on the converter's operating state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control methods are used in delta-configuration converters, then the converter can operate for reactive power, harmonic, and flicker compensation, but energy pulsation occurs in the converter branches with significant energy swing
Solution Approach 1:
The patent changes the current waveform parameters by superimposing third-order harmonics on the fundamental frequency current. This parameter modification allows the converter to maintain compensation functionality while reducing energy pulsation in the branches by altering the current's frequency composition and temporal distribution
Solution Approach 2:
The patent employs periodic third-harmonic current injection that synchronizes with the fundamental frequency. This periodic action creates a controlled energy circulation pattern within the delta configuration that reduces the amplitude of energy oscillations while maintaining the converter's compensation effectiveness
2Ease of manufacture
If the number of switching modules in each branch is reduced to lower costs, then installation costs and losses decrease, but the converter's ability to manage energy pulsation is limited
Solution Approach 1:
By changing the current waveform parameters through harmonic injection, the patent reduces the RMS current and energy pulsation in each branch. This allows the use of fewer switching modules and smaller component ratings while maintaining effective energy management, thereby reducing installation costs and losses
3Loss of energy
If additional current harmonics are injected to reduce energy swing, then energy pulsation is reduced, but the control complexity increases
Solution Approach 1:
The patent modifies current parameters by adding third-harmonic components with specific amplitude and phase relationships. While this requires enhanced control capabilities, the structured approach of injecting only the third harmonic (rather than multiple harmonics) and using synchronized control reduces the overall control complexity compared to more comprehensive harmonic injection strategies
Data Source
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AI summary
The invention relates, among other things, to a converter (10) for a three-phase voltage with three electrically delta-connected series circuits (R1, R2, R3), each comprising at least two switching modules (SM) connected in series, and with a control device (30) connected to the switching modules (SM) that can drive the switching modules (SM) in such a way that branch currents with the fundamental frequency of the three-phase voltage and with at least one additional current harmonic flow in the series circuits (R1, R2, R3), the additional current harmonic being dimensioned such that it flows in the series circuits (R1, R2, R3) of the converter (10) and remains inside the converter.