Power converter, motor driver, and refrigeration cycle applied equipment
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Solution Overview
Problem
Conventional power converters accelerate the aging of smoothing capacitors due to high current flow, leading to increased device size and cost when attempting to mitigate this through capacitor capacity increases or degradation tolerance enhancements.
Innovation Solution
A power converter system that includes a rectifier, a capacitor, an inverter, and a controller, where the controller adjusts the pulsation width of the current flowing to the capacitor based on the operation mode of the refrigeration cycle equipment, reducing stress on the capacitor and minimizing its deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacity of the smoothing capacitor is increased to suppress ripple change of capacitor voltage, then the deterioration of the smoothing capacitor is suppressed, but the size of the device increases
Solution Approach 1:
The inverter dynamically adjusts the pulsation width of current according to operation mode (cooling/heating) to match the natural pulsation characteristics of the capacitor, transforming a static capacitor design problem into a dynamic control solution that adapts to varying operational conditions
Solution Approach 2:
The controller changes the pulsation width parameter of the inverter output current based on operation mode, allowing the system to optimize capacitor stress characteristics without changing the capacitor's physical capacity or size
2Reliability
If a smoothing capacitor with large degradation tolerance due to ripple is used to suppress ripple change, then the deterioration of the smoothing capacitor is suppressed, but the cost of the capacitor component increases
Solution Approach 1:
Instead of selecting a capacitor based on its degradation tolerance parameters, the system changes the electrical operating parameters (pulsation width) to protect a standard capacitor, avoiding the need for expensive specialized components
Solution Approach 2:
The inverter system actively compensates for capacitor stress by adjusting its own output characteristics, making the system itself protective toward the capacitor rather than relying on the capacitor's inherent tolerance
3Power
If a large current flows into the smoothing capacitor to ensure adequate power conversion, then the power conversion performance is maintained, but the aged deterioration of the smoothing capacitor is accelerated
Solution Approach 1:
The system utilizes periodic pulsation in the inverter output current that synchronizes with the capacitor's natural charging/discharging cycles, creating a rhythmic current pattern that reduces peak stress while maintaining average power transfer
Solution Approach 2:
The controller dynamically adjusts the pulsation width based on operation mode to optimize the balance between power transfer efficiency and capacitor stress, allowing high power performance when needed while protecting the capacitor during extended operation
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 suppresses the increase in device size while maintaining capacitor performance, reducing the need for larger capacitors and associated costs, and allows for stable operation across varying temperature conditions.
Implementation Method 1
a rectifier configured to rectify a first alternating-current power supplied from an alternating-current power supply
Implementation Method 2
a capacitor connected to output ends of the rectifier
Implementation Method 3
an inverter configured to convert power output from the rectifier and the capacitor into a second alternating-current power
Data Source
AI summary
A power converter installed in a refrigeration cycle applied equipment includes a rectifier configured to rectify a first alternating-current power supplied from a commercial power supply, a capacitor connected to output ends of the rectifier, an inverter configured to convert power output from the rectifier and the capacitor into a second alternating-current power and to output the second alternating-current power to a motor, and a controller configured to control an operation of the inverter such that the second alternating-current power containing pulsation according to pulsation of power flowing into the capacitor from the rectifier is output from the inverter and to reduce current flowing to the capacitor. The power converter is configured to operate such that the pulsation width of the pulsating current generated by the second alternating-current power is different depending on whether an operation of the refrigeration cycle applied equipment is a cooling operation or a heating operation.