Power Conversion Device 3N Harmonic Suppression
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Solution Overview
Problem
Existing power conversion devices face challenges in suppressing capacitor voltage pulsation and reducing capacitor losses, leading to increased size and cost, especially when controlling active power.
Innovation Solution
A power conversion device configuration that includes multiple power conversion cells and capacitors, where a 3N order higher-harmonic-wave voltage is added to AC voltages to minimize capacitor losses, reducing the capacity and volume of capacitors while controlling active power effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a self-excited reactive power control device is used to convert reactive current, then reactive power control is achieved, but capacitor voltage pulsation increases due to ripple component
Solution Approach 1:
The invention changes the voltage waveform parameters by superimposing a 3N-order higher-harmonic voltage component on the fundamental AC voltage. This parameter modification transforms the capacitor current waveform, eliminating the ripple component that causes voltage pulsation and energy loss, while maintaining the same fundamental power conversion function.
2Reliability
If capacitor capacity is increased to reduce voltage pulsation, then voltage stability improves, but device size and cost increase
Solution Approach 1:
Instead of increasing capacitor capacity, the invention changes the operating voltage waveform parameters by adding a 3N-order harmonic component. This allows the use of smaller capacitors while achieving the same voltage stability, as the modified waveform eliminates the harmful ripple that would otherwise require larger capacitance to filter.
3Power
If a power conversion device for active power control is used, then active power conversion is achieved, but capacitor voltage pulsation and losses increase
Solution Approach 1:
The invention modifies the voltage waveform parameters by superimposing a 3N-order higher-harmonic component on the fundamental voltage used for active power conversion. This parameter change eliminates the capacitor ripple current and voltage pulsation that normally accompany active power conversion, thereby reducing capacitor losses while maintaining full active power conversion capability.
Data Source
AI summary
A power conversion device that suppresses voltage pulsation of a capacitor of a power converter with respect to a control target whose effective power is to be controlled is provided. The power conversion device includes a plurality of power conversion cells that are connected to each other, and convert a primary-side system voltage into a secondary-side system voltage, a capacitor that is connected to each of the plurality of power conversion cells, and a power conversion cell driver that drives the power conversion cells to add a 3N order higher-harmonic-wave voltage of each of alternating voltages of the plurality of power conversion cells to the each of alternating voltages, and output a voltage made by adding the each of alternating voltages and the 3N order higher-harmonic-wave voltage, when N is a natural number.