Power Converter Overheat Control Using Heat-Equivalent Power Limiting
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Solution Overview
Problem
In power conversion devices, overheat protection mechanisms often result in excessive restriction of output to the inverter, leading to low operation efficiency.
Innovation Solution
An overheat protection control device for a power converter that includes a power calculation unit, a heat amount calculation unit, and a power command unit. The heat amount calculation unit adds a product of current squared and time when the electric power exceeds a threshold, and subtracts a value when it falls below the threshold, allowing for dynamic adjustment of electric power based on heat equivalent values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter operation is stopped in overheat protection mode, then the power converter is protected from overheating, but the operation efficiency of the inverter drops due to excessive protection restriction
Solution Approach 1:
The patent implements dynamic control of the inverter operation during overheat protection by adjusting the switching frequency based on the heat amount-equivalent value. Instead of a static stop command, the system dynamically modulates the switching frequency to maintain protection while allowing continued operation at reduced intensity, thus resolving the contradiction between reliability and productivity
Solution Approach 2:
The patent changes the control parameter from binary (stop/continue) to continuous (switching frequency modulation). By controlling the switching frequency according to the heat amount-equivalent value, the system achieves gradual power reduction rather than abrupt cessation, maintaining both protection effectiveness and operational efficiency
2Productivity
If the switching frequency is controlled based on heat amount-equivalent value, then excessive protection is reduced and operation efficiency is maintained, but the control system complexity increases
Solution Approach 1:
The patent introduces a heat amount-equivalent value as an intermediary parameter that simplifies the control logic. Instead of directly monitoring temperature and making binary decisions, the system uses this intermediate calculation (product of current squared and time) to drive the switching frequency control, making the complex thermal management problem more manageable
Solution Approach 2:
The patent implements a feedback mechanism where the heat amount-equivalent value continuously informs the switching frequency adjustment. This closed-loop control allows the system to automatically adapt the inverter operation based on accumulated thermal stress, reducing the need for complex external control systems while maintaining high operation efficiency
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 reduces the drop in operation efficiency of the power converter by minimizing excessive protection measures, thereby maintaining optimal performance while preventing overheating.
Implementation Method 1
a value of a product of a current squared and time which is a value obtained by multiplying a square of an electric current flowing in a conductor by the time
Data Source
AI summary
In an overheat protection control device for a power converter, a heat amount calculation unit adds a value of a product of a current squared and time to a heat amount-equivalent value of a last time when an electric power is equal to or more than a first determination output value, and, when the electric power is less than the first determination output value, subtracts a subtraction value from the heat amount-equivalent value of the last time. When a heat amount-equivalent value calculated by the heat amount calculation unit becomes a first determination heat amount-equivalent value or larger, a power command unit restricts the electric power in the power converter, and lifts the restriction on the electric power in the power converter when the heat amount-equivalent value calculated by the heat amount calculation unit becomes a second determination heat amount-equivalent value or smaller.