Variable Inductance Power Converter for Harmonic Distortion
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Solution Overview
Problem
Existing power converters experience voltage oscillations and degradation of Total Harmonic Distortion (THDi) and Partial Weighted Harmonic Distortion (PWHD) when the electrical load absorbs more power than the converter is designed for, leading to unsatisfactory harmonic distortion management.
Innovation Solution
A power converter with a variable inductor made of ferromagnetic material, featuring multiple coils wound on different parts of the core and a DC/DC converter connected to the power supply lines, which detects voltage oscillations and controls the inductance value by saturating the inductor to reduce inductance when oscillations occur, thereby maintaining acceptable harmonic distortion levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple inductance is connected to the DC power supply bus to manage harmonic distortion, then the THDi and PWHD are improved, but when the electrical load absorbs higher power, voltage oscillations occur on the DC supply bus causing degradation of THdi or PWHD
Solution Approach 1:
The patent applies the dynamics principle by making the inductance value variable rather than fixed. The inductor's inductance can be dynamically adjusted based on operating conditions: at normal load, the inductor operates in linear region providing harmonic filtering; when load exceeds converter capacity and voltage oscillations occur, the inductor saturates to reduce inductance value, allowing the system to adapt to different power levels and maintain stability.
Solution Approach 2:
The patent changes the inductance parameter of the inductor from constant to variable. By controlling the DC flux in the magnetic material through an additional winding, the inductance value can be modified. When voltage oscillations are detected, the control system adjusts the flux to saturate the magnetic core, thereby reducing inductance and preventing further degradation of harmonic distortion metrics under overload conditions.
2Object-generated harmful factors
If the inductor operates with high inductance value to filter harmonics, then THDi and PWHD are reduced, but the inductor becomes more susceptible to saturation and voltage oscillations under overload conditions
Solution Approach 1:
The inductor transitions from a static high-inductance component to a dynamic device that can adjust its inductance value. During normal operation, the inductor maintains high inductance for effective harmonic filtering. When overload causes voltage oscillations, the control system modifies the DC flux to reduce inductance, preventing saturation and maintaining voltage stability. This dynamic adaptation resolves the contradiction between harmonic filtering performance and overload reliability.
Solution Approach 2:
The patent implements feedback control by monitoring the DC bus voltage and detecting oscillations. When voltage oscillations indicate overload conditions, the control system responds by adjusting the DC flux in the inductor's magnetic core, which changes the inductance value. This closed-loop feedback mechanism allows the system to automatically adjust the inductor's characteristics to maintain both harmonic distortion performance and voltage stability under varying load conditions.
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
The solution effectively maintains THDi and PWHD at acceptable values even when the electrical load exceeds the converter's designed capacity, reducing voltage oscillations and harmonic distortion, thus enhancing the converter's performance and stability.
Implementation Method 1
the control means being arranged to saturate the variable inductance in order to lower the value of said inductance when oscillations appear on the DC supply bus
Implementation Method 2
a variable inductor comprising a core made of ferromagnetic material
Data Source
Figure 1~3
Figure 4~6
AI summary
The converter has a variable inductor (Lv) comprising a coil (B1) wound on a part of a ferromagnetic material core and connected in series on a power supply line (10) of a continuous power supply bus. A direct current supply source is connected to another coil (B2) of the inductor, which is wound on another part of the core. A detecting unit detects oscillations of direct voltage (Vbus) on the bus. A control unit (22) controls direct current provided to the latter coil to vary inductance value of the inductor, and saturates the inductor to lower the value when oscillations appear on the bus.