Rectifier Control Unit Regeneration Inrush Current Mitigation
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Solution Overview
Problem
In 120-degree conduction mode rectifiers, inrush currents and resonance occur when switching between regeneration and power running states, leading to potential component damage and abnormal heating due to frequent state transitions, especially when regenerative power is small.
Innovation Solution
A rectifier with a control unit that adjusts the ON period of switching devices based on calculated power values, curtailing inrush currents and preventing resonance by modifying the ON period duration during power running and regeneration states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If 120-degree conduction mode rectifier is used for power regeneration, then regenerative power can be returned to AC power supply, but inrush currents occur when switching from regeneration to power running state
Solution Approach 1:
The control unit performs preliminary action by gradually increasing the ON period of switching devices over multiple cycles before full power running operation. This gradual transition prevents sudden current surges when switching from regeneration to power running state, while still enabling effective power regeneration when needed.
Solution Approach 2:
The rectifier dynamically adjusts the ON period of switching devices based on operational state and cycle count. During regeneration to power running transition, the ON period is progressively increased over multiple cycles rather than being fixed, allowing the system to adapt smoothly between states and prevent inrush currents.
2Use of energy by moving object
If 120-degree conduction mode is used during regeneration, then power can be returned to AC supply, but resonance occurs when regenerative power is small causing frequent state transitions
Solution Approach 1:
The control unit requires a predetermined number of cycles to elapse before allowing transition from power running to regeneration state. This preliminary waiting period prevents premature or unstable state transitions when regenerative power is small, ensuring system stability while still enabling power return when conditions are appropriate.
Solution Approach 2:
The system employs periodic action by requiring multiple cycles to pass before allowing state transitions. This periodic timing mechanism filters out small or unstable regenerative power conditions, preventing resonance caused by frequent unwanted transitions while maintaining the ability to return power when conditions are stable.
3Device complexity
If switching devices are controlled with fixed ON period, then control is simple, but component damage and abnormal heating occur due to frequent state transitions
Solution Approach 1:
The control unit dynamically adjusts the ON period of switching devices based on the number of cycles elapsed and current operational state. This dynamic control prevents frequent state transitions that cause abnormal heating and component damage, while maintaining relatively simple control logic through cycle-based timing mechanisms.
Solution Approach 2:
The control unit implements preliminary timing checks before allowing state transitions by requiring a predetermined number of cycles to elapse. This preliminary action filters out unstable conditions that would cause frequent transitions and component damage, while keeping the control structure relatively simple through systematic cycle counting.
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 inrush currents and resonance, enhancing the reliability and longevity of rectifier components by optimizing switching operations based on power thresholds and state determinations.
Implementation Method 1
a main circuit unit including a rectifying device and a switching device in reverse-parallel connection with the rectifying device and configured to perform power conversion between AC power on a side of a three-phase AC power supply and DC power on a DC side by rectifying operation of the rectifying device
Data Source
AI summary
The rectifier includes: a main circuit unit configured to perform power conversion between AC power on a side of a three-phase AC power supply and DC power on a DC side by rectifying operation of a rectifying device and ON-OFF operation of a switching device; a power calculation unit configured to calculate a value of a power flowing between the side of the three-phase AC power supply and the DC side via the main circuit unit; and a control unit configured to perform control to execute the ON-OFF operation of the switching device, wherein the control unit changes a length of an ON period per cycle in the ON-OFF operation executed on the switching device according to the value of the power calculated by the power calculation unit.