Regenerative Converter Control for Stable DC Voltage and Lower Switching Loss
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Solution Overview
Problem
Conventional power conversion devices face issues with increased switching loss, heat generation, noise, and insulation deterioration due to fixed DC voltage settings during power regeneration, leading to overmodulation and voltage fluctuations.
Innovation Solution
A power regeneration converter that includes a control unit to dynamically adjust DC voltage based on AC voltage detection, current detection, and grid power source voltage, using bidirectional conversion and PWM modulation to maintain optimal DC voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high DC voltage is set to maximize output AC voltage during regeneration, then the AC voltage output capability is improved, but switching loss and heat generation increase
Solution Approach 1:
The patent applies dynamics by making the DC voltage command value variable rather than fixed. The control unit dynamically adjusts the DC voltage command value based on detected AC voltage and current conditions, allowing the system to adapt to different operating states. This resolves the contradiction by enabling high voltage output capability when needed while reducing voltage (and thus switching loss) during normal operation.
Solution Approach 2:
The patent changes the parameter of DC voltage from a fixed high value to a dynamically adjustable value. By modifying the DC voltage command value based on detected AC voltage and current, the system can optimize the balance between output capability and switching loss, directly addressing the technical contradiction.
2Power
If a high DC voltage is set to maximize output AC voltage during regeneration, then the AC voltage output capability is improved, but heat generation of filters including reactors increases
Solution Approach 1:
The dynamic adjustment of DC voltage command value based on AC voltage and current detection allows the system to reduce voltage during normal operation, thereby reducing heat generation in filters and reactors, while maintaining high voltage capability when regeneration requires maximum output.
Solution Approach 2:
By changing the DC voltage parameter from fixed to variable, the system can optimize heat generation in filters. The control unit adjusts the voltage based on actual conditions, reducing unnecessary heat generation while preserving the capability to deliver high power when needed.
3Power
If a high DC voltage is set to maximize output AC voltage during regeneration, then the AC voltage output capability is improved, but insulation deterioration of the loaded device accelerates
Solution Approach 1:
The dynamic voltage adjustment based on real-time detection allows the system to minimize the time that high voltage is applied to the load, thereby reducing insulation stress and deterioration while maintaining the capability to provide high voltage output when regeneration demands it.
Solution Approach 2:
By making the DC voltage a variable parameter rather than a fixed high value, the system reduces the cumulative exposure of insulation to high voltage stress, extending component life while preserving the ability to deliver maximum power when needed.
4Loss of energy
If DC voltage is reduced to suppress switching loss and heat generation, then energy efficiency is improved, but voltage fluctuations cause overmodulation and increased noise
Solution Approach 1:
The patent implements feedback by using the detected AC voltage and current information to continuously adjust the DC voltage command value. This closed-loop control ensures that the DC voltage is optimized for efficiency while maintaining stability and preventing overmodulation, as the system responds to actual operating conditions rather than using a fixed predetermined value.
Solution Approach 2:
The dynamic adjustment mechanism allows the DC voltage to adapt to changing conditions, maintaining stability despite fluctuations. The control unit processes detected voltage and current information to make real-time adjustments, preventing overmodulation and noise while keeping switching loss and heat generation minimized.
5Device complexity
If fixed DC voltage is used for simple control, then device complexity is reduced, but operating efficiency decreases due to inability to adapt to different operating conditions
Solution Approach 1:
The feedback mechanism uses detected AC voltage and current values to automatically adjust the DC voltage command, providing adaptive control without requiring complex manual intervention or multiple predetermined voltage levels. This maintains relatively simple device architecture while significantly improving operating efficiency across different conditions.
Solution Approach 2:
The control unit performs self-adjustment by using its own detection capabilities to determine the appropriate DC voltage command value. The system serves itself by automatically optimizing its operating parameters based on detected conditions, improving efficiency without adding significant complexity to the control architecture.
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 overmodulation, switching loss, noise, and insulation deterioration by maintaining appropriate DC voltage levels, enhancing operational efficiency and reducing heat generation.
Implementation Method 1
bidirectional conversion between DC and AC is performed by the conversion unit
Implementation Method 2
having a filter unit disposed between the conversion unit and the three-phase AC power supply
Implementation Method 3
a control unit for calculating a three-phase AC voltage target value for performing PWM modulation
Data Source
AI summary
A power regeneration converter is disposed between an inverter outputting a three-phase alternating current (AC) to an electric motor and a three-phase AC power source which is an input system, and supplies induced electric power generated by the motor to the three-phase AC power source, wherein a control unit calculates a three-phase AC voltage target value for performing PWM based on a three-phase AC voltage of the input system detected by an AC voltage detection unit, a three-phase AC detected by an AC detection unit, and a direct current (DC) voltage between the inverter and the power regeneration converter detected by a DC voltage detection unit, and controls the DC voltage between the inverter and the power regeneration converter based on the calculated three-phase AC voltage target value. An output DC voltage is maintained, overmodulation, noise, switching loss, heat generation, and insulation degradation of a load device are decreased.