Parallel Synchronous Motor Control With Single-Drive Current Feedback
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Solution Overview
Problem
Existing systems for controlling multiple synchronous motors in parallel often result in voltage mismatch and excessive current draw due to lack of signal feedback, potentially causing damage to the system.
Innovation Solution
A system and method utilizing a single motor drive with a current sensor to detect output signals and control multiple synchronous motors in parallel, incorporating vector control and scalar Volts per Hertz control with stabilization loops to maintain net active and reactive power equilibrium and reject power perturbations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor drive controls multiple synchronous motors in parallel without individual current sensor signals, then the system complexity is reduced, but voltage mismatch occurs and excessive current is drawn
Solution Approach 1:
The patent combines multiple synchronous motors into a single parallel-controlled system using one motor drive unit, eliminating the need for separate drives for each motor. This merging approach reduces device complexity while maintaining system reliability through shared control architecture and common current sensing.
Solution Approach 2:
The single motor drive is designed to universally control multiple synchronous motors simultaneously, performing the function of multiple individual drives with one unified controller. This multi-functional approach reduces component count while ensuring reliable operation through centralized control logic that monitors overall system current.
2Reliability
If individual current sensor signals are used for each synchronous motor, then voltage mismatch is prevented, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the current sensing function from individual motor-level components and consolidates it to the system level. Instead of embedding sensors in each motor, a single current sensor measures the total output current from the motor drive, which is then used to infer and control the operating state of all parallel-connected motors collectively.
Solution Approach 2:
The single current sensor acts as an intermediary that provides centralized feedback about the overall system current state. This intermediary measurement point allows the control system to monitor and adjust voltage and current distribution across multiple motors without requiring direct sensing at each motor terminal, thereby reducing sensor quantity while maintaining voltage matching.
3Ease of operation
If open loop control is used for multiple asynchronous motors, then the control simplicity is improved, but excessive current draw occurs due to lack of feedback
Solution Approach 1:
The patent implements feedback control by using the current sensor to continuously measure the output current and feeding this information back to the motor drive controller. This feedback mechanism enables the system to detect current draw conditions and adjust control parameters accordingly, preventing excessive current consumption while maintaining operational simplicity through automated closed-loop adjustment.
Solution Approach 2:
The control system transitions from static open-loop control to dynamic closed-loop control, where control parameters are continuously adjusted based on real-time current feedback. This dynamic adaptation allows the system to maintain optimal current efficiency across varying load conditions while preserving ease of operation through automatic control adjustments.
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AI summary
A system for controlling plurality of synchronous motors connected in parallel including a motor drive, current sensor, and plurality of synchronous motors connected in parallel to the motor drive. The synchronous motors connected to the motor drive can include the same size and power rating to allow synchronous operation and have similar load capacity. Further, the system can operate with substantially similar loads on each of the plurality of synchronous motors. The motor drive can be a variable speed drive using vector control and a closed loop current controller to control the motors. The motor drive can be a variable frequency drive using scalar control and open loop controller to control the motors. The motor drive controls the plurality of synchronous motors by maintaining net active power and net active power, and by rejecting power perturbations, at the common node.