Power Converter Voltage Utilization via Dynamic DC Link
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Solution Overview
Problem
The existing power converter systems face a trade-off between increasing the voltage across the DC link and maintaining high efficiency, with the power buffer circuit's voltage being limited to avoid excessive power coverage, which restricts the voltage utilization ratio and requires high breakdown voltage for capacitors.
Innovation Solution
The power converter system adjusts the discharge duty cycle and rectifying duty cycle to optimize the voltage utilization ratio by varying the DC voltage within specific periods, reducing the required both-end voltage across the capacitor, thus minimizing the breakdown voltage needed for the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage across the DC link is increased to improve voltage utilization ratio, then the voltage utilization ratio is improved, but the current capacity of power devices in the inverter must be increased
Solution Approach 1:
The patent applies dynamics by making the DC link voltage variable rather than constant. The voltage is dynamically adjusted based on the instantaneous value of the single-phase AC voltage, creating a time-varying voltage profile that increases the average voltage utilization ratio while keeping peak voltage levels manageable, thus avoiding the need for increased power device current capacity
Solution Approach 2:
The patent changes the voltage parameter of the DC link from a fixed value to a variable value that follows a specific waveform pattern. By controlling the power buffer circuit to generate a DC voltage with a waveform obtained by full-wave rectification of two-phase AC, the system achieves an average voltage utilization ratio of 0.9 at maximum, optimizing the balance between voltage utilization and power device requirements
2Power
If the power buffer circuit voltage is limited to avoid excessive power coverage, then the breakdown voltage requirement for capacitors is reduced, but the voltage utilization ratio is restricted
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the power buffer circuit voltage according to the instantaneous AC voltage value. The voltage is varied over time following a full-wave rectified two-phase AC waveform pattern, which increases the average voltage utilization ratio while ensuring that the peak voltage remains within acceptable limits for the capacitor breakdown voltage
Solution Approach 2:
The patent changes the voltage parameter of the power buffer circuit from a constant limited value to a time-varying parameter that follows a specific waveform. This parameter change allows the system to achieve an average voltage utilization ratio of 0.9 at maximum while keeping the peak voltage within the capacitor's breakdown voltage rating
Data Source
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AI summary
An object is to provide a technique for increasing the voltage across a DC link without increasing the power covered by a power buffer circuit. A discharge duty (dc) that is a duty at which a switch (Sc) is conductive takes a value ((Vm/Vc)cos2(ωt)) obtained by dividing a product of a crest value (Vm) of a single-phase AC voltage (Vin) and a square (cos2(ωt)) of a cosine value of a phase (ωt) of the single-phase AC voltage (Vin) by a both-end voltage (Vc) across a capacitor (C4). A sum of a product of a rectifying duty (drec) that is a duty at which a converter (3) is conductive and a rectified voltage (Vrec) output from the converter (3) and a product of the both-end voltage (Vc) and the discharge duty (dc) varies in a period that is a half of the period of the single-phase AC voltage (Vin).