Three-Phase Drive Speed Estimation Without Test Signals
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Solution Overview
Problem
Existing methods for determining the speed and motor parameters of frequency converter-fed three-phase drives are unreliable at low speeds and require additional test signals, leading to noise pollution and increased motor losses, and they lack a consistent solution across all speed ranges.
Innovation Solution
A method that converts space vector components into a nonlinear system with complex-valued input and output variables, using a nonlinear regression analysis to determine motor parameters and rotor position without test signals, allowing reliable determination across the entire speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless methods are used to avoid position sensors, then cost and reliability are improved, but measurement precision deteriorates at low speeds and zero speed
Solution Approach 1:
The patent changes the mathematical parameters of the estimation approach by using a nonlinear regression model with complex-valued variables instead of traditional linear methods. This allows the system to maintain measurement precision across the entire speed range including zero speed, while still using sensorless methods to avoid additional hardware costs and reliability issues associated with physical sensors.
2Measurement precision
If high-frequency test signals are continuously impressed to determine motor parameters, then measurement precision is improved, but loss of energy increases due to additional motor losses
Solution Approach 1:
Instead of continuously impressing high-frequency test signals, the patent uses periodic evaluation of the nonlinear regression model based on normal operating current and voltage measurements. The motor parameters are determined periodically throughout operation without requiring continuous additional excitation, thereby maintaining measurement precision while minimizing energy losses.
Solution Approach 2:
The patent enables the motor control system to determine its own parameters using its normal operating signals (current and voltage measurements during regular operation). No external test signals or additional excitation are required - the system uses its own operational data to continuously update and refine motor parameter estimates through the nonlinear regression analysis.
3Ease of operation
If linear regression analysis is used to determine rotor position, then ease of operation is improved, but measurement precision deteriorates at low speeds and zero speed
Solution Approach 1:
The patent transitions from a static linear regression approach to a dynamic nonlinear regression model that adapts to varying operating conditions. The nonlinear model with complex-valued variables can dynamically capture the anisotropic behavior of the motor across different speeds and load conditions, maintaining measurement precision while remaining computationally tractable through iterative solution methods.
Data Source
Figure 1
AI summary
The invention relates to a method for determining the speed and/or motor parameters of a three-phase drive operated with a frequency converter, comprising the following steps: providing motor currents in stator coordinates (iα, iβ) as the first input to a first processing unit (11), determining motor setpoint voltages in stator coordinates from a current DC link voltage of the frequency converter and PWM signals (S1 - S6), and providing the motor setpoint voltages in stator coordinates as the second input to the first processing unit (11), calculating the speed and/or motor parameters in stator coordinates, wherein - starting from the general voltage equation of the rotating field machine in space vector representation, a partition into the two voltage space vector components is carried out, - the voltage setpoint space vectors (uαs,uβs) and the current actual value space vectors (iα,iβ) are transformed into a nonlinear system with complex-valued input and output variables and - using the input variables of the first computing unit (11) the rotational speed and/or motor parameters are determined as output variable(s) of this system by means of a suitable recursive procedure.,