Power Conversion Device Temperature Correction
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Solution Overview
Problem
Inverter devices require costly voltage detection circuits and struggle to accurately suppress switching element temperature due to high heat generation and noise interference, especially when temperature detection units are positioned away from the converter unit.
Innovation Solution
A power conversion device with a rectifier, converter unit, smoothing capacitor, reactor current detection, bus voltage detection, and a control unit that calculates switching commands and corrects temperatures based on a correction table or function, allowing accurate temperature recognition of the switching element even when the temperature detection unit is not close, eliminating the need for a voltage detection unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a voltage detection circuit is provided to detect input voltage for controlling the inverter circuit, then the temperature increase of the switching element can be suppressed, but the cost increases and the device complexity increases
Solution Approach 1:
The patent extracts and removes the voltage detection circuit from the system. Instead of detecting input voltage to control the inverter, the system uses only temperature detection from the temperature detection unit near the switching element, eliminating the need for voltage detection circuitry and its associated costs and complexity.
Solution Approach 2:
The system uses the switching element's own temperature characteristics to control the inverter circuit. The temperature detection unit monitors the switching element's temperature directly, and the control unit adjusts the inverter output based on this temperature feedback, allowing the system to self-regulate without external voltage detection.
2Measurement precision
If the temperature detection unit is positioned close to the switching element to accurately detect temperature, then the temperature measurement precision improves, but the device complexity increases and noise interference worsens
Solution Approach 1:
The patent segments the temperature detection function from the switching element itself by using a separate temperature detection unit positioned near the switching element. This allows the detection unit to be optimally positioned for temperature measurement without requiring the switching element to have embedded sensors, simplifying the overall module design.
Solution Approach 2:
The temperature detection unit acts as an intermediary between the switching element and the control unit. It is positioned close to the switching element to accurately sense temperature without being directly integrated into the switching element structure, and transmits temperature signals to the control unit for processing.
3Measurement precision
If the temperature detection unit is positioned close to the switching element, then the temperature detection accuracy improves, but the reliability worsens due to noise interference from switching operations
Solution Approach 1:
The patent extracts the temperature detection unit from the immediate switching element structure and positions it nearby. This separation allows accurate temperature monitoring while reducing exposure to electromagnetic noise and interference generated by the switching operations, thereby improving detection reliability.
Solution Approach 2:
The temperature detection unit serves as an intermediary that is close enough to the switching element to accurately sense temperature but sufficiently separated to avoid direct interference from switching noise. The control unit then processes this temperature information to control the inverter output, ensuring reliable 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
This solution accurately corrects switching element temperatures, reduces costs by eliminating the need for voltage detection units, and improves reliability by accurately recognizing temperatures despite the distance between the temperature detection unit and the switching element.
Implementation Method 1
a rectifier configured to rectify an input voltage supplied from an AC power supply
Implementation Method 2
a converter unit including: a reactor connected to an output end of the rectifier; a backflow prevention element connected in series to the reactor; and a switching element connected between the reactor and the backflow prevention element, the converter unit being configured to boost a DC voltage rectified by the rectifier
Implementation Method 3
a smoothing capacitor configured to smooth a bus voltage outputted from the converter unit
Implementation Method 4
a temperature detection unit configured to detect a temperature of the switching element
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A power conversion device includes: a rectifier, a converter unit including a reactor connected to an output end of the rectifier, a backflow prevention element connected in series to the reactor, and a switching element connected between the reactor and the backflow prevention element, the converter unit being configured to boost a DC voltage rectified by the rectifier, a smoothing capacitor, a reactor current detection unit configured to detect a reactor current flowing through the reactor, a bus voltage detection unit configured to detect a bus voltage, a temperature detection unit configured to detect a temperature of the switching element, and a control unit. The control unit includes a converter control unit configured to calculate a switching command value for driving the switching element, on the basis of a target command voltage which is the bus voltage to be targeted, the bus voltage detected by the bus voltage detection unit, and the reactor current detected by the reactor current detection unit, and a temperature correction unit configured to correct the temperature of the switching element detected by the temperature detection unit, on the basis of the switching command value calculated by the converter control unit.