Converter Control Device Suppressing Voltage Variation
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Solution Overview
Problem
Existing control devices for converters fail to effectively suppress output voltage variations caused by dead time, leading to erroneous voltage control due to sensor errors and incomplete suppression of voltage fluctuations.
Innovation Solution
A control device for converters that includes a reactor, switching elements, diodes, a voltage control unit, a current control unit, and a signal generation unit, which adjusts output voltage and current to target values, and sets the voltage control cycle based on motor power variations to prevent current retention during dead time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead time is provided to prevent simultaneous conduction of switching elements, then switching safety is improved, but output voltage variation occurs when reactor current direction changes
Solution Approach 1:
The control device predicts the reactor current direction before the dead time occurs and prepares appropriate control signals in advance. By determining the current direction ahead of time and pre-positioning the switching control signals, the system ensures smooth current transition through the dead time without causing output voltage variations, thus maintaining both switching safety and voltage stability.
2Object-affected harmful factors
If voltage command value is corrected downward to suppress unexpected voltage increase, then voltage increase is suppressed, but the variation itself of output voltage is not suppressed and sensor errors cause erroneous determination
Solution Approach 1:
The control device continuously monitors the actual reactor current direction and compares it with the predicted direction. Based on this feedback, the system adjusts the control signals to compensate for any deviations caused by sensor errors or unexpected conditions. This feedback mechanism ensures accurate current direction detection and maintains reliable voltage control without erroneous corrections.
Solution Approach 2:
The control device replaces sensor-based current direction detection with a prediction mechanism that calculates current direction based on control signals and circuit parameters. This substitution eliminates reliance on potentially erroneous sensor measurements during the critical dead time period, improving control accuracy and preventing erroneous voltage corrections.
3Stability of the object's composition
If current control is added to adjust reactor current to target current, then output voltage variation is suppressed, but device complexity increases
Solution Approach 1:
The control device merges the current direction prediction function with the existing voltage control unit. By integrating the prediction mechanism into the existing control structure and sharing computational resources, the system achieves current control functionality without proportionally increasing device complexity. The merged structure efficiently suppresses output voltage variation while maintaining reasonable system complexity.
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 control device effectively suppresses output voltage variations by adjusting current flow through the reactor, stabilizing the output voltage and reducing the need for large smoothing capacitors, thus enhancing system responsiveness and reducing costs.
Implementation Method 1
the reactor has one end connected to a positive electrode of a DC power supply... The reactor has a function of storing electric energy in a magnetic field when a current flows through the reactor
Data Source
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Figure 3~5
AI summary
A voltage control operation unit (106) receives, from a subtraction unit (104), a value obtained by subtracting a detection value of a voltage (Vm) from a voltage command value (VR), and performs a control operation for setting the voltage (Vm) to be equal to the voltage command value (VR). The voltage control operation unit (106) outputs the calculated control amount as a current command value (IR). A current control operation unit (110) receives, from a subtraction unit (108), a value obtained by subtracting a detection value of a current (IL) from a current command value (IR), and performs a control operation for setting the current (IL) to be equal to the current command value (IR). A driving signal generation unit (112) generates a signal (PWC) for driving a boost converter based on a duty command value (d) received from the current control operation unit(110).