Power Converter Damping Control for Harmonic Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power converters face challenges in suppressing harmonics due to inductive loads while maintaining resonance suppression and achieving optimal control responsiveness, particularly with LC filters, leading to complex control circuits and inefficiencies.
Innovation Solution
A power converter design that controls the inverter section to achieve a damping characteristic with a phase lead element and second-order lag element, setting the damping coefficient greater than 1, and utilizes feedback loops to independently set cut-off frequencies for harmonic and resonance suppression, allowing for downsizing of inductive elements and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large harmonics of the motor slot are involved in the motor load, then the reactor capacity is increased to lower the resonance frequency of the LC filter to suppress power harmonics, but the features of the capacitorless method cannot be utilized and the system becomes less efficient
Solution Approach 1:
The patent changes the control parameters of the inverter section to achieve a damping characteristic with a damping coefficient greater than 1. This is accomplished by controlling the transfer characteristic of the inverter section to match a specific damping characteristic, which allows suppression of power harmonics without increasing reactor capacity, thereby maintaining the efficiency of the capacitorless method.
2Object-affected harmful factors
If the reactor capacity is increased to suppress power harmonics, then the resonance frequency of the LC filter is lowered, but the system complexity increases and the responsiveness to inductive loads deteriorates
Solution Approach 1:
The patent employs feedback control by detecting the voltage across the inductance element and using this information to control the inverter section. The controller adjusts the inverter output based on the detected voltage to maintain the damping characteristic, achieving harmonic suppression through intelligent control rather than increasing hardware complexity.
Solution Approach 2:
The patent changes the dynamic parameters of the inverter section to achieve optimal damping performance. By controlling the transfer characteristic to match the desired damping characteristic with damping coefficient greater than 1, the system achieves harmonic suppression without requiring complex additional control circuits or larger reactors.
3Object-affected harmful factors
If conventional control methods are used with LC filters, then resonance suppression is achieved, but the control responsiveness to inductive loads like motors is insufficient
Solution Approach 1:
The patent optimizes the control parameters of the inverter section to achieve a damping characteristic with damping coefficient greater than 1. This parameter optimization allows the system to simultaneously suppress resonance and improve control responsiveness to inductive loads, as the damping characteristic directly affects both resonance behavior and transient response speed.
Data Source
Figure 1
Figure 2
Figure 3(A)~3(C)
AI summary
There is provided a controller (100) for controlling an inverter section (12) on the basis of a voltage (VL) across a reactor (L) detected by a voltage detector (101). The controller (100) controls the inverter section (12) so that a transfer characteristic of an input voltage of the inverter section (12) versus a DC voltage from a diode bridge (11) becomes a damping characteristic by a phase lead element and a second-order lag element connected in series, while a damping coefficient (ζ) of a transfer characteristic of the input voltage of the inverter section (12) versus a DC voltage from the diode bridge (11) is set larger than 1. Thus, there is provided a power converter capable of suppressing harmonics due to an inductive load while suppressing resonance due to the LC filter and capable of fulfilling optimal control of good responsivity to the inductive load.