Power conversion device having a control unit that outputs based on detected inductor current
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Solution Overview
Problem
Power conversion devices in air conditioners face instability due to harmonic current components flowing through dc-end capacitors induced by ripple components of input voltage, which can lead to unbalanced systems and increased manufacturing costs.
Innovation Solution
A power conversion device with a rectification unit, boost converter, inductor current detection, dc-end voltage detection, and a control unit that generates a converter switching control signal through proportional resonant control to reduce harmonic current components, using phase-locked loop control for unbalanced systems, allowing for the use of low-capacitance capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional power conversion devices are used without proportional resonant control, then the system structure is simple, but harmonic current components flow through the dc-end capacitor due to input voltage ripple
Solution Approach 1:
The patent applies proportional resonant control to change the control parameters of the boost converter, specifically modifying the duty cycle based on detected inductor current and dc-end voltage. This parameter adjustment eliminates harmonic current components by dynamically adapting the converter operation to compensate for input voltage ripple, thereby resolving the contradiction between reducing harmful factors and maintaining simple device structure.
2Reliability
If high-capacitance capacitors are used to filter ripple currents, then the system stability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent converts the harmful effect of input voltage ripple into a controllable parameter by using proportional resonant control. The control system detects the ripple and actively compensates for it through duty cycle adjustment, transforming what would require large capacitors for passive filtering into an active control problem that can be solved with smaller, less expensive capacitors combined with intelligent control algorithms.
3Adaptability or versatility
If the load connected to the inverter varies significantly, then the adaptability of the system is improved, but the operation becomes temporarily unstable
Solution Approach 1:
The patent implements feedback control by continuously detecting the inductor current and dc-end voltage, then using this information to adjust the duty cycle of the boost converter through proportional resonant control. This closed-loop feedback mechanism enables the system to adapt to varying loads while maintaining operational stability, as the control system automatically compensates for load changes to prevent temporary instability.
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 reduces harmonic current ripples, stabilizes the system, and lowers manufacturing costs by minimizing ripple currents in capacitors, enhancing the operational stability and efficiency of air conditioners.
Implementation Method 1
a rectification unit for rectifying input alternating current power
Implementation Method 2
a boost converter for boosting power rectified from the rectification unit
Data Source
AI summary
The power conversion device may include a rectification unit, a boost converter for boosting power rectified from the rectification unit, a dc-end capacitor connected to an output end of the boost converter, an inductor current detection unit for detecting an inductor current flowing in an inductor within the boost converter, a dc-end voltage detection unit for detecting voltages of both ends of the dc-end capacitor, and a control unit for controlling the boost converter. The control unit may generate and output a converter switching control signal by performing proportional resonant control for a duty command value of a switching element within the boost converter, based on the detected inductor current and dc-end voltage. Therefore, a harmonic current component flowing through a dc-end capacitor induced by a ripple component of an input voltage may be reduced.