Pre-charge Unit Thermal Protection Using Voltage-Based Current Estimation

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Solution Overview

Problem

Existing methods for thermal protection of pre-charge units in electric power conversion systems require expensive current sensors and fast digital signal processing hardware, making them costly and inefficient.

Innovation Solution

A method that uses existing voltage sensors to estimate currents flowing through the pre-charge unit's step-up transformer, eliminating the need for dedicated current sensors and reducing digital signal processing bandwidth by estimating thermal levels based on voltage inputs, thereby providing thermal overload protection without expensive hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dedicated current sensors and fast digital signal processing hardware are used for thermal protection, then thermal protection reliability is improved, but system cost increases

Engineering Contradiction:

Improvethermal protection reliabilityVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses voltage sensor measurements to estimate current values through mathematical relationships rather than directly measuring current. The voltage waveform characteristics are copied and processed to derive current information, eliminating the need for expensive current sensors while maintaining protection reliability

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces hardware-based current sensing with a computational approach using voltage measurements and mathematical estimation. The physical measurement system is substituted with an information processing system that calculates current from voltage data, reducing hardware costs

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If dedicated current sensors and fast digital signal processing are implemented, then thermal protection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvethermal protection accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the existing voltage sensor serve multiple functions: it not only provides voltage information for normal operation but also enables current estimation for thermal protection. This multi-functionality eliminates the need for separate current sensing hardware, reducing device complexity while maintaining protection accuracy

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own existing voltage measurement infrastructure to provide thermal protection functionality. The voltage sensor and processing system serve themselves by deriving current information from their own voltage measurements, eliminating the need for additional dedicated protection hardware

Inventive Principle:

Principle #25Self-service

3Speed

If fast digital signal processing hardware is used for current sampling, then thermal response time is improved, but manufacturing cost increases

Engineering Contradiction:

Improvethermal response timeVSAvoidmanufacturing cost

Core Design Contradiction:

SpeedVSEase of manufacture

Solution Approach 1:

The patent pre-establishes the mathematical relationships and estimation algorithms that allow rapid current calculation from voltage measurements. By preparing the computational framework in advance, the system achieves fast thermal response without requiring expensive real-time hardware acceleration

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20240250517A1Method for providing thermal protection to a pre-charge unit and electric power conversion system for executing the method

Publication Date: 2024.07.25 DANFOSS POWER ELECTRONICS AS

AI summary

A method for providing thermal protection to a pre-charge unit (PRC) of an electric power conversion system, such as a medium-voltage adjustable-speed drive, with a step-up transformer and a DC link includes the steps of executing a parameter identification block identifying the electrical and thermal parameters of the PRC; of an electric power conversion system executing a current estimation block estimating the current flowing though the PRC's step-up transformer based on a voltage input; executing a thermal level estimation block estimating a thermal level at the PRC's step-up transformer based on the estimated current flowing though the PRC's step-up transformer; executing a protection logic block comparing the estimated thermal level to a pre-determined trip threshold to determine whether a thermal overload has occurred; and outputting a trip signal if the trip threshold has been exceeded. The disclosure further discloses an electric power conversion system, such as a medium-voltage adjustable-speed drive, with a step-up transformer and a DC link for executing a corresponding method.