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Ld Estimator

Estimate stator inductance (Ld) of permanent magnet synchronous motor (PMSM)

Since R2023a

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Libraries:
Motor Control Blockset / Parameter Estimation / PMSM Parameter Estimation

Description

The Ld Estimator block computes the d-axis stator inductance of a PMSM using the phase currents, stator resistance, and the test configuration elements.

At first, the block locks the rotor along the d-axis by injecting a constant voltage (Vd). This ensures that the rotor remains stationary (aligned with d-axis) during frequency injection. To estimate d-axis stator inductance, the block injects a high-frequency voltage signal along the d-axis and then performs the frequency sweep process by gradually reducing the injected signal frequency using the step size defined by Step for frequency sweep (Hz) parameter. During frequency sweep, the block monitors the magnitude of the motor phase current. When the current magnitude becomes appropriately high or when the injected signal frequency reaches the minimum value (Minimum frequency (Hz) parameter), the block starts the estimation process by injecting a signal with rising frequency having a step size of Frequency step size for estimation (Hz) with number of steps defined by the Number of frequencies for estimation parameter. For details about these parameters, see PMSM Parameter Estimation Configurator.

This image shows the frequency sweep and the incremental steps of rising frequency.

The Ld estimation process uses the measured frequency sweep time duration as well as the step size of the changing frequency to estimate the d-axis stator inductance, Ld.

Examples

Estimate PMSM Parameters Using Parameter Estimation Blocks

Estimate PMSM Parameters Using Parameter Estimation Blocks

Uses the parameter estimation blocks provided by Motor Control Blockset™ to estimate these parameters of a permanent magnet synchronous motor (PMSM) with a quadrature encoder sensor:

Estimate PMSM Parameters Using Parameter Estimation Blocks on Real-Time Systems

Estimate PMSM Parameters Using Parameter Estimation Blocks on Real-Time Systems

Uses the parameter estimation blocks provided by Motor Control Blockset™ to estimate these parameters of a permanent magnet synchronous motor (PMSM):

Ports

Input

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The three-phase current response (in amperes) of the motor measured by the current sensors.

Note

Providing phase-c current input is optional. The block functionality is not impacted if you do not provide the phase-c current input.

Data Types: single

Estimated stator resistance (in ohms) of the PMSM. You can either connect this input port to the Rs output of the PMSM Rs Estimator block or provide the resistance value manually using a Constant block.

Data Types: single

Signal that either starts or stops Ld estimation:

  • 1 (rising edge of a pulse) — This signal initiates the Ld estimation process.

  • 0 (falling edge of a pulse) — This signal immediately stops the Ld estimation process. If you interrupt the estimation process abruptly before completion, the block does not compute or output the Ld value.

Data Types: Boolean

This table summarizes the expected configuration elements in the bus signal input.

CategoryConfiguration elementUnits

Elements for motor and inverter hardware

Number of pole pairs

-

Rated speed of motor

RPM

Rated current of motor

A

Maximum measurable inverter current

A

Board resistance

ohms

Current sense gain

A/ADC Count

Voltage sense gain

V/ADC Count

Parameter estimation sample time

seconds

Elements for estimating motor inductances (Ld and Lq)

Maximum frequency

Hz

Minimum frequency

Hz

Step for frequency sweep

Hz

Frequency step size for estimation

Hz

Number of frequencies for estimation

-

Elements for estimating back EMF constant (Ke), motor inertia (J), and friction constant (B)

Back EMF estimation time

seconds

Back EMF estimation maximum speed limit

RPM

Specify current controller gains (off/on)

-

Proportional gain

-

Integral gain

-

Iq reference current as a ratio of rated motor current

PU current

Lower speed limit for inertia estimation

RPM

You can connect this input port to the Config output port of the PMSM Parameter Estimation Configurator block.

Data Types: single

Output

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Stator reference voltage components along the a, b, and c axes of the abc reference frame. Each voltage component has a range between -1 and 1.

Data Types: single

Estimated d-axis stator inductance (in henries).

Data Types: single

Debug signals that the block provides for examination. The bus includes these debug signals.

Debug signalDescriptionUnits

InjFreq

Frequency of signal injected most recently

Hertz

status

0Ld estimation did not start yet.

-

1Ld estimation is in progress.

-

2Ld estimation completed successfully.

-

8100Ld estimation failed because the current feedback from motor did not increase proportionally to the rise in the injected voltage.

-

Id

D-axis current

amperes

Vd

D-axis voltage

volts

PhaseDiff_rad

Phase difference between the injected voltage and current response

radians

Data Types: single

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2023a

See Also

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