Shunt Control for Multiple Power Converters on Shared DC Bus
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Solution Overview
Problem
In systems with multiple adjustable speed motor drives (ASDs) sharing a common DC bus, existing shunt resistor configurations lead to uneven utilization and potential premature failure due to differences in power ratings and measurement noise, causing excessive loading on some resistors.
Innovation Solution
A system that monitors and adjusts the utilization rate of shunt devices by modifying configuration parameters to control the connection frequency of shunt devices to the DC bus, using voltage thresholds and duty cycles to balance the dissipation of regenerative energy across multiple power converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple ASDs share a common DC bus with individual shunt resistors, then regenerative energy can be dissipated, but uneven utilization occurs causing some resistors to be excessively loaded and fail prematurely
Solution Approach 1:
The system continuously monitors the DC bus voltage and the operational status of each shunt resistor, using this feedback information to dynamically adjust which shunt resistors are activated. When one shunt resistor approaches its power rating limit, the control system detects this condition and switches to utilizing other available shunt resistors, thereby preventing any single resistor from being excessively loaded and failing prematurely.
Solution Approach 2:
The shunt resistor configuration is made dynamic rather than static. The control system can switch between different shunt resistors based on real-time operating conditions, power ratings, and utilization levels. This dynamic switching capability allows the system to adapt to varying regenerative energy levels and distribute the dissipation load across multiple resistors as needed, preventing any single resistor from being overloaded.
2Power
If shunt resistors are sized according to ASD power ratings, then higher power ASDs have larger resistors, but measurement noise and bias cause one ASD to connect first resulting in excessive loading on that resistor
Solution Approach 1:
The control system is configured with predetermined connection thresholds and prioritization schemes for multiple shunt resistors. Instead of relying solely on real-time voltage measurements that may be affected by noise and bias, the system has pre-established rules for which shunt resistors should be activated first under specific conditions. This preliminary configuration helps overcome measurement uncertainties by providing a structured approach to shunt selection.
Solution Approach 2:
The system adjusts operational parameters such as connection thresholds and activation sequences based on the specific characteristics of each shunt resistor and the current operating conditions. By dynamically changing these parameters, the system can compensate for measurement noise and bias, ensuring that shunt resistors are activated in an optimal sequence that prevents excessive loading on any single resistor.
3Speed
If a shunt resistor connects at a lower voltage level, then it activates earlier to dissipate energy, but it becomes heavily utilized and subject to excessive loading
Solution Approach 1:
The system segments the total power dissipation requirement across multiple shunt resistors rather than relying on a single resistor to handle all regenerative energy. By dividing the dissipation function among several resistors with different power ratings and connection characteristics, the system prevents any single resistor from being heavily overloaded while maintaining effective energy dissipation.
Solution Approach 2:
Multiple shunt resistors are combined into a coordinated system where they work together to dissipate regenerative energy. The control system manages the collective operation of these resistors, switching between them based on their utilization levels and power ratings. This merging approach allows the system to leverage the combined capacity of multiple resistors, preventing any single one from being excessively loaded while maintaining fast activation response.
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 approach ensures more even utilization of shunt devices, preventing premature failure and maintaining stable voltage levels by adjusting the connection thresholds and duty cycles based on utilization rates, thereby distributing regenerative energy effectively among multiple ASDs.
Implementation Method 1
When the resistor is connected to the DC bus, current flows through the resistor and the power is dissipated from the resistor as heat.
Data Source
AI summary
A system for managing shunt utilization among multiple power converters sharing a common DC bus is disclosed. Each power converter includes a shunt device, typically one or more power resistors, configured to dissipate power from the DC bus. The power converter is configured according to an initial set of configuration parameters to selectively connect the shunt device to the DC bus. Each power converter monitors the amount of power being dissipated from the DC bus via the shunt device connected to that power converter and determines a utilization rate for the shunt device. As the utilization rate increases, the configuration parameters are modified to less frequently connect the shunt device to the DC bus. As the utilization rate decreases, the configuration parameters are modified to more frequently connect the shunt device to the DC bus.