Predictive DC Voltage Control for Series Hybrid Motor Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing series hybrid vehicle motor control systems fail to accurately follow target torque due to delays in responding to changes in DC voltage, leading to inefficiencies and increased maintenance costs, particularly in mining and construction vehicles where precise torque control is essential.
Innovation Solution
An electric motor control system that predicts changes in DC voltage and uses a power converter to adjust the AC motor's excitation magnetic flux, allowing the motor torque to follow the target torque by varying the voltage applied to the AC motor faster than the inherent response time constant of the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the excitation magnetic flux component (d-axis component) is kept constant or gradually weakened to minimize response time, then the control response speed is improved, but the motor torque cannot accurately follow the target torque when DC voltage varies
Solution Approach 1:
The patent applies preliminary action by predicting the future DC voltage value before it actually changes. The prediction unit calculates what the DC voltage will be based on its rate of change, and this predicted value is used in advance to adjust the excitation magnetic flux component. This allows the motor torque to follow the target torque accurately without waiting for the actual voltage change to occur, resolving the contradiction between fast response and accurate torque control.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual DC voltage and comparing it with the predicted DC voltage. The prediction unit uses the actual voltage changes to refine future predictions, creating a closed-loop system. This feedback mechanism ensures that the excitation magnetic flux component is continuously adjusted to maintain accurate torque control while keeping the response time constant, thus resolving the contradiction between response speed and control accuracy.
2Adaptability or versatility
If the DC voltage varies with engine speed changes, then the system adapts to different operating conditions, but the motor torque lags behind the torque command due to the first order lag in excitation magnetic flux
Solution Approach 1:
The patent applies preliminary action by predicting the future DC voltage value before it actually changes. The prediction unit calculates what the DC voltage will be based on its rate of change, and this predicted value is used in advance to adjust the excitation magnetic flux component. This allows the motor torque to follow the target torque accurately without waiting for the actual voltage change to occur, resolving the contradiction between fast response and accurate torque control.
Solution Approach 2:
The patent applies dynamics by making the excitation magnetic flux component dynamically adjustable based on the predicted DC voltage. Instead of keeping the excitation flux constant or using a fixed weakening schedule, the system continuously adjusts the d-axis current command to maintain the optimal excitation level that corresponds to the predicted DC voltage. This dynamic adjustment eliminates the first-order lag and enables the motor torque to respond immediately to torque commands across varying operating conditions.
3Loss of energy
If one-pulse control is used in most speed regions to reduce switching losses, then energy efficiency is improved, but the amplitude of AC voltage applied to the motor varies with DC voltage changes, causing torque control inaccuracies
Solution Approach 1:
The patent applies preliminary action by predicting the future DC voltage value before it actually changes. The prediction unit calculates what the DC voltage will be based on its rate of change, and this predicted value is used in advance to adjust the excitation magnetic flux component. This allows the motor torque to follow the target torque accurately without waiting for the actual voltage change to occur, resolving the contradiction between fast response and accurate torque control.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the excitation magnetic flux component (d-axis current) in response to predicted DC voltage changes. Under one-pulse control, instead of keeping the excitation flux constant, the system modifies this parameter to compensate for voltage variations. This maintains the relationship between voltage and flux that ensures accurate torque control while preserving the energy efficiency benefits of one-pulse control.
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 solution enables the AC motor torque to accurately follow the target torque even when DC voltage varies, reducing switching losses and maintaining system efficiency, thus addressing the inefficiencies and maintenance challenges in series hybrid vehicles.
Implementation Method 1
a rectifier, a battery for being charged with an DC output of the motor
Implementation Method 2
an inverter for converting a DC power charged by the battery into an AC power
Implementation Method 3
the motor torque proportional to a product of the magnetic flux component (d-axis component) and the torque current (q-axis component)
Data Source
AI summary
An electric motor control system including a generator, an AC motor, a power converter for driving the AC motor using a DC output voltage of the generator, and an electric motor controller for controlling the power converter. The electric motor controller controls the power converter by predicting a change in the DC voltage.