Motor Current Control Using Dynamic D-Axis Injection
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Solution Overview
Problem
Existing electric motor control systems in HVAC systems face inefficiencies due to suboptimal power factor correction, leading to increased energy storage and return, rather than effective real power usage.
Innovation Solution
A current control module generates a voltage request based on d-axis current demand, with a switching control module adjusting the motor operation and an Idr injection module applying adjustments to improve efficiency by optimizing current and voltage alignment, using a combination of lookup tables and feedback signals to refine the d-axis current demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional motor control is used without dynamic Idr adjustment, then the control system is simple, but the power factor is suboptimal and real power utilization is reduced
Solution Approach 1:
The patent implements dynamic adjustment of the d-axis current (Idr) demand based on real-time operating conditions including DC bus voltage, motor speed, and torque demand. The Idr injection module continuously modifies Idr demand using lookup tables and feedback signals, transitioning the control system from static to dynamic operation to optimize power factor across varying load conditions.
Solution Approach 2:
The control system incorporates feedback mechanisms where the Idr injection module uses measured DC bus voltage, speed, and torque demand to adjust Idr demand. The system monitors the voltage request versus available voltage and uses this feedback to refine current alignment, creating a closed-loop control that improves real power utilization while managing complexity through intelligent feedback processing.
2Use of energy by moving object
If Idr demand is increased to improve power factor, then real power utilization improves, but current consumption may increase
Solution Approach 1:
The patent dynamically changes the Idr demand parameter based on operating conditions. By adjusting Idr demand according to DC bus voltage, speed, and torque demand, the system optimizes the balance between power factor improvement and current consumption. The lookup tables provide pre-calculated optimal Idr values that achieve power factor correction without excessive current increase.
Solution Approach 2:
The system applies partial adjustment to Idr demand rather than maximum correction at all times. The Idr injection module selectively applies adjustments based on whether improvement is identified through feedback, avoiding excessive current consumption while still achieving meaningful power factor improvement. This selective application prevents over-correction that would waste energy.
3Productivity
If dynamic adjustment of Idr demand is implemented, then power factor and real power utilization improve, but control algorithm complexity increases
Solution Approach 1:
The patent uses lookup tables that contain pre-calculated optimal Idr demand values for various operating conditions. This preliminary computation approach allows the real-time control to simply retrieve and apply appropriate values based on current speed, torque, and voltage conditions, significantly reducing the computational complexity of the real-time control algorithm while maintaining dynamic optimization capabilities.
Solution Approach 2:
The lookup table acts as an intermediary between the complex optimization calculations and the real-time control execution. Instead of performing complex real-time optimization algorithms, the system uses the lookup table to translate operating conditions into optimal Idr demand values, simplifying the control algorithm while preserving energy efficiency benefits.
Data Source
AI summary
A current control module generates a voltage request based on a d-axis current (Idr) demand. A switching control module controls a motor based on the voltage request and generates an out-of-volts (OOV) signal based on a comparison of the voltage request and an available voltage. An Idr injection module generates the Idr demand based on a direct current (DC) bus voltage, a rotational speed, and a demanded torque and selectively applies a first adjustment to the Idr demand. The Idr injection module identifies whether an improvement resulted from the first adjustment, wherein the improvement is identified based on at least one of (i) a measured current of the motor and (ii) the OOV signal. The Idr injection module selectively applies a second adjustment to the Idr demand based on whether the improvement is identified.