Controller and method for minimizing phase advance current
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Solution Overview
Problem
Existing electric motor control systems in HVAC systems face inefficiencies in power factor correction, leading to suboptimal use of real power and increased reactive power storage and return, which affects motor performance and energy efficiency.
Innovation Solution
A system comprising a current control module, a switching control module, and an Idr injection module that dynamically adjusts the d-axis current demand based on measured voltage, commanded speed, and torque, with adaptive adjustments to optimize motor operation and power factor correction by generating and applying voltage requests and adjustments to minimize out-of-volts signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional power factor correction is used in electric motor control systems, then the circuit's use of real power increases, but reactive power storage and return increases, leading to suboptimal energy efficiency
Solution Approach 1:
The system dynamically adjusts the d-axis current demand (Idr) in real-time based on operating conditions including measured voltage, commanded speed, and torque requirements. This dynamic adjustment allows the motor control system to optimize the balance between real power utilization and reactive power management, preventing excessive reactive power storage and return while maintaining efficient real power usage throughout varying operating conditions.
Solution Approach 2:
The invention changes the d-axis current parameter (Idr) to optimize power factor correction. By selectively adjusting Idr demand based on measured voltage and operating conditions, the system modifies the motor's magnetic field characteristics to improve the relationship between current and voltage, thereby increasing real power utilization while minimizing reactive power wastage.
2Use of energy by moving object
If d-axis current demand is increased to improve power factor correction, then real power utilization improves, but motor current increases, potentially reducing motor efficiency
Solution Approach 1:
The system employs feedback mechanisms by continuously monitoring measured voltage, commanded speed, and torque requirements to dynamically adjust the d-axis current demand. This feedback loop ensures that Idr is increased only when necessary for power factor correction while preventing excessive current that would reduce motor efficiency. The switching control module compares voltage request with measured DC bus voltage to generate out-of-volts signals that trigger appropriate Idr adjustments.
Solution Approach 2:
The d-axis current demand is made dynamic rather than fixed, adjusting in real-time based on the interplay between power factor correction needs and motor efficiency requirements. The system selectively applies adjustments to Idr demand based on out-of-volts signals and operating conditions, optimizing the balance between power factor improvement and current minimization throughout varying operational states.
Data Source
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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.