Inverter DC Voltage Compensation for Motor Cable Loss
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Solution Overview
Problem
The calibration of a vehicle's drive system is compromised by the resistance introduced by a cable connected to the dynamometer during the calibration process, leading to a discrepancy between the DC voltage set point measured during calibration and the actual operating conditions without the cable.
Innovation Solution
A method and system to adjust the DC reference voltage by calculating the cable resistance and determining a DC compensation voltage to account for the voltage drop caused by the cable, using a processor to modify the reference voltage based on the cable's resistance, power factor, and modulation index, and applying this adjustment during normal vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cable is used during calibration to connect the inverter and motor, then the calibration can be performed with a dynamometer, but the cable resistance introduces a significant voltage drop that causes discrepancy between calibration DC voltage set point and actual operating DC voltage set point
Solution Approach 1:
The patent calculates the cable resistance and determines a DC compensation voltage in advance during the calibration process. This preliminary compensation value is then applied to adjust the DC voltage set point, ensuring that the calibration accounts for cable losses before the actual operation begins. The compensation is calculated using the formula: DC compensation voltage = (cable resistance × current × power factor) / modulation index
Solution Approach 2:
The patent modifies the DC voltage set point parameter by adding or subtracting the calculated DC compensation voltage based on the operating mode (motoring or regenerative). This parameter adjustment ensures that the inverter output voltage compensates for the cable resistance voltage drop, maintaining accurate motor control despite the presence of cable losses
2Reliability
If the DC voltage set point is adjusted to compensate for cable resistance, then accurate motor performance is maintained, but additional calculations and adjustments are required during calibration
Solution Approach 1:
The patent incorporates feedback by measuring the actual current flowing through the cable during calibration and using this information to calculate the voltage drop. The measured current, combined with the known cable resistance and power factor, provides real-time feedback that enables accurate calculation of the DC compensation voltage, ensuring reliable motor performance 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
Ensures consistent motor operation by correcting the DC voltage set point to match actual vehicle conditions, maintaining the modulation index and ensuring accurate motor performance by compensating for cable resistance.
Implementation Method 1
the cable having a resistance that introduces a significant voltage drop at the motor
Data Source
AI summary
A system performs a method for operating a vehicle. A cable is attached between an inverter of the vehicle and a motor of the vehicle, the cable having a resistance. The inverter is operated using a first direct current (DC) reference voltage. A processor obtains a current from the motor, calculates a power factor at the inverter, obtains a resistance of the cable, determines a voltage drop between the inverter and the motor from the current, the resistance and the power factor due to a presence of the cable, determines a DC compensation voltage from the voltage drop, and adjusts the first DC reference voltage to a second DC reference voltage using the DC compensation voltage.