Motor Drive DC Bus Voltage Feedback for Transient Load Regulation
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Solution Overview
Problem
Current power conditioners for non-motor loads, such as medical imaging scanners, struggle to rapidly adjust to transient load conditions, leading to under-voltage and over-voltage issues that can cause equipment failure due to their reliance on slow-reacting RMS voltmeters, resulting in downtime and service calls.
Innovation Solution
A motor drive system with a voltage feedback circuit that monitors DC bus voltage changes and adjusts the power conditioning scheme using a PID controller to maintain near steady-state conditions, incorporating a derivative term from the DC bus voltage to quickly respond to transient loads, ensuring ±1% load voltage regulation with less than 3% total harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a power conditioner uses RMS voltmeters for voltage feedback, then voltage regulation can be achieved during steady-state conditions, but the response time is too slow to address transient load conditions, causing under-voltage and over-voltage failures
Solution Approach 1:
The patent segments the voltage measurement function into two separate systems: RMS voltmeters for steady-state voltage regulation and DC bus voltage sensors for transient condition detection. Each sensor type is optimized for its specific operating condition, allowing the system to maintain precise voltage regulation while rapidly responding to transient loads without the limitations of a single measurement system
Solution Approach 2:
The patent introduces DC bus voltage as an intermediary parameter that indirectly reflects transient load conditions before they affect the output voltage. By monitoring DC bus voltage changes, the controller can predict and respond to transient conditions proactively, rather than reactively waiting for output voltage deviations detected by slow RMS voltmeters
2Ease of operation
If a power conditioner operates with standard voltage feedback control, then normal operating conditions can be maintained, but transient load conditions cause significant voltage drops and current inrush that trip protective devices
Solution Approach 1:
The patent implements preliminary action by detecting DC bus voltage changes that indicate impending transient conditions and preemptively adjusting the switching duty cycles of power devices. This proactive control prevents voltage drops and current inrush before they occur, avoiding trips of protective devices while maintaining stable normal operation through standard feedback control
3Ease of manufacture
If a motor drive is used to control power to a non-motor load, then cost-effective power conditioning can be achieved, but the motor drive was not originally designed to handle transient load conditions of non-motor loads
Solution Approach 1:
The patent achieves universality by enabling motor drives to perform dual functions: traditional motor control and power conditioning for non-motor loads. By adding DC bus voltage monitoring and transient response control algorithms, the motor drive becomes adaptable to transient non-motor load conditions while maintaining its original motor control capabilities, providing cost-effective multi-functional power conditioning
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
The system effectively prevents load failures by rapidly adjusting to transient conditions, maintaining stable voltage and reducing downtime, with experimental results confirming ±1% load voltage regulation and less than 3% total harmonic distortion, making it suitable for high-performance applications like medical imaging scanners.
Implementation Method 1
A voltage sensor provides voltage feedback to a controller
Implementation Method 2
motor drives typically provide a volts-per-hertz control
Implementation Method 3
The controller determines what changes in power conditioning are needed
Data Source
AI summary
A motor drive for conditioning power to be delivered to a non-motor load includes a voltage feedback circuit that monitors a DC bus voltage and, based on changes in the DC bus voltage, adjusts a power conditioning scheme such that near steady-state load conditions are maintained in response to a transient load condition. The voltage feedback circuit has a voltage sensor that provides voltage feedback to a controller that determines what changes in power conditioning are needed in response to a transient load condition that manifests itself in a change in DC bus voltage.