Direct Power Converter Control for LC Filter Resonance Suppression
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Solution Overview
Problem
The existing direct power converters face challenges in preventing degradation of the sampling and command value updating in the control system due to the resonance of the LC filter, which affects the inverter's performance.
Innovation Solution
A method for controlling a charge and discharge circuit in a direct power converter that includes a current blocking unit and a booster circuit, where the resonance suppression controller adjusts the current command value by subtracting a correction value based on the reactor voltage, preventing the suppressing current from being superimposed on the inverter current, thus maintaining the stability of the control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a suppressing current is obtained from the reactor voltage and superimposed on the inverter current to suppress LC filter resonance, then the resonance suppression effect is improved, but the sampling and command value updating in the control system are degraded
Solution Approach 1:
The patent divides the current control into separate independent control loops: one for the inverter current and another for the suppressing current. The suppressing current is generated independently from the rectifier side based on reactor voltage, rather than being superimposed on the inverter current. This segmentation prevents interference between the two control functions, maintaining both resonance suppression effectiveness and control system accuracy.
Solution Approach 2:
The patent introduces an intermediary approach by generating the suppressing current from the reactor voltage through a dedicated control path that does not interfere with the inverter current sampling. The suppressing current is injected at the rectifier output side rather than being added to the inverter current, serving as a mediator that achieves resonance suppression without degrading the control system's measurement precision.
2Reliability
If the suppressing current is superimposed on the inverter current, then the LC filter resonance is suppressed, but the control system stability is degraded
Solution Approach 1:
The patent segments the control system into independent pathways: the inverter current control maintains its original stability while the suppressing current is generated separately from the reactor voltage and injected at the rectifier output. This prevents the suppressing current from interfering with the inverter current sampling and command value updating, thereby maintaining control system stability while achieving resonance suppression.
3Reliability
If the resonance frequency of the LC filter is set to a fraction of the carrier frequency, then the filter performance is improved, but the control system sampling is degraded due to resonance suppression requirements
Solution Approach 1:
The patent separates the resonance suppression function from the inverter control sampling by generating the suppressing current independently from the reactor voltage and injecting it at the rectifier output side. This segmentation allows the LC filter resonance frequency to be set at a fraction of the carrier frequency for optimal filter performance without causing sampling delays in the inverter control system, as the suppressing current generation does not interfere with the inverter current sampling process.
Data Source
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AI summary
Sampling of a control system that controls an inverter and updating of a command value are prevented from being degraded, even when the resonance of an LC filter is suppressed using a suppressing current. In a block 10a, a current distribution factor generator 11 receives an amplitude Vm of a single-phase AC voltage Vin, an amplitude Im of an input current, a command value Idc* of a DC current Idc, a command value Vc* of a both-end voltage Vc, and a power angular velocity ω, and outputs a current command value Ib*. A resonance suppression controller 15 receives a reactor voltage VL, and outputs a correction value k·VL. A subtractor 17 subtracts the correction value k·VL from the current command value Ib*, and provides the result to a chopper controller 16. The chopper controller 16 outputs a boost duty dl based on a corrected current command value (Ib* - k·VL). A comparator 14 compares the booster ratio dl with a carrier C2, and outputs the result as a control signal SSI.