Parallel Module Phase Current Sensing With Digital Summation
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Solution Overview
Problem
Existing methods for measuring phase current in power electronics devices with multiple parallel-connected power semiconductor modules suffer from interference susceptibility and inaccuracies in analog current addition, especially when more than three modules are used, leading to unreliable measurements and lack of information about current distribution.
Innovation Solution
A device comprising current sensing devices to detect partial currents, conversion units to convert analog signals to digital, and an evaluation unit to generate control and diagnostic information by digitally adding these signals, providing symmetry and asymmetry analysis of current distribution among partial currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If decentralized current measurement via shunt measurement is used for each parallel-connected power semiconductor module, then information about current distribution among modules is available, but analog addition of partial currents becomes extremely complex and impractical when more than three modules are used
Solution Approach 1:
The patent replaces the mechanical/analog signal addition system with a digital system. Each shunt resistor generates a voltage signal that is individually amplified and converted to digital form by separate ADCs. The digital signals are then added by a digital adder unit, eliminating the complexity of analog addition circuits while preserving current distribution information.
Solution Approach 2:
The patent segments the current measurement system into independent measurement channels for each parallel-connected power semiconductor module. Each module has its own shunt resistor, amplifier, and ADC, allowing individual measurement of partial currents. This segmentation enables flexible digital processing and addition of the separated current signals without the limitations of analog circuitry.
2Measurement precision
If analog addition of partial currents is performed, then total phase current is obtained, but the signal processing is very susceptible to interference and yields inaccurate and unreliable measurement results
Solution Approach 1:
The patent substitutes analog signal processing with digital signal processing to eliminate interference susceptibility. Each partial current is measured by a shunt resistor and amplified, then converted to digital signals by individual ADCs. The digital adder unit sums these digital signals without being affected by electromagnetic interference, ground loops, or signal degradation that plague analog addition circuits.
Solution Approach 2:
The patent introduces digital conversion as an intermediary step between analog measurement and signal addition. The ADCs act as mediators that convert analog voltage signals from shunt resistors into digital form, isolating the measurement process from interference. This intermediary conversion ensures accurate representation of partial currents before they are added digitally.
3Ease of operation
If a central current transformer is used to measure total phase current, then measurement is simple, but no information is available about how currents are distributed within the parallel module circuit
Solution Approach 1:
The patent segments the current measurement into individual partial current measurements for each parallel-connected power semiconductor module using separate shunt resistors. This segmentation provides detailed information about current distribution among modules while maintaining relatively simple implementation through modular measurement channels that can be independently configured.
Solution Approach 2:
The patent creates separate measurement copies for each parallel module instead of using a single central measurement point. Each shunt resistor creates a copy of the current flow through its respective module, allowing individual monitoring and analysis of current distribution. This copying approach provides comprehensive information without significantly increasing system complexity.
Data Source
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AI summary
The invention relates to a device for inspecting and/or monitoring current (IU, IV, IW) in a phase (U, V, W) in a power electronics device (30), wherein the power electronics device (30) has at least two power semiconductor modules (LM1, LM2), wherein the at least two power semiconductor modules (LM1, LM2) on the phase (U, V, W) are connected in parallel, wherein the device (MV) comprises at least two current detection devices (SV1, SV2), at least two conversion units (ADW1, ADW2) and an evaluation apparatus (ED), wherein each current detection device (SV1, SV2) is designed to detect a partial current (TS1, TS2) at each power semiconductor module (LM1, LM2) and to output an analogue signal (AS1, AS2) which corresponds to the detected partial current (TS1, TS2), wherein a sum of all of the detected partial currents (TS1, TS2) gives the current (IU, IV, IW) in the phase (U, V, W), wherein each conversion unit (ADW1, ADW2) is connected downstream of a respective current detection device (SV1, SV2) and is designed to convert the analogue signal (AS1, AS2) into a digital signal (S1, S2), wherein the evaluation apparatus (ED) is connected downstream of the at least two conversion units (ADW1, ADW2) and is designed and configured to generate, based on the digital signals (S1, S2), an output signal which contains control-relevant and/or diagnostics-relevant information about the current (IU, IV, IW) in the phase (U, V, W).