PM Motor Voltage Control Using Load Angle Estimation in ESPs

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Solution Overview

Problem

Controlling permanent magnet synchronous motors in electric submersible pump (ESP) applications is challenging due to their complex design, non-self-starting nature, and the need for precise voltage and energy management, especially in deep well environments where sensor data collection is impractical, leading to inefficiencies and potential motor damage from voltage drops.

Innovation Solution

A method and system for dynamically optimizing voltage in PM synchronous motors by estimating the load angle and power factor, adjusting voltage based on these estimates to maintain efficient operation, using a control module with components for load angle extraction, dynamic voltage compensation, and scalar control, which includes a sliding mode observer for rotor angle estimation and power factor calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional scalar control is used for PM motor, then implementation is simple, but motor operates at lower efficiency

Engineering Contradiction:

Improvecontrol implementation simplicityVSAvoidmotor efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The control system continuously estimates the load angle based on terminal voltage and current measurements, and uses this feedback to dynamically adjust the voltage magnitude applied to the motor. This closed-loop approach enables the motor to operate at optimal efficiency points across varying load conditions while maintaining scalar control simplicity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces complex mechanical sensor-based measurement systems with an electronic estimation approach. Instead of using physical sensors to directly measure rotor position and load angle, the system calculates these parameters electronically from terminal voltage and current, simplifying the hardware while improving efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If vector control is used for PM motor, then motor efficiency is maximized, but implementation complexity increases

Engineering Contradiction:

Improvemotor efficiencyVSAvoidcontrol system complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent extracts only the essential element needed for efficiency optimization - the load angle estimation - from the complex vector control system. By isolating and implementing just this critical parameter estimation and adjustment mechanism, the system achieves significant efficiency improvements without adopting the full complexity of vector control.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of implementing the complete vector control algorithm, the system applies a partial approach by focusing solely on load angle-based voltage magnitude adjustment. This partial implementation provides sufficient efficiency gains for ESP applications while avoiding the excessive complexity of full vector control.

Inventive Principle:

Principle #16Partial or excessive action

3Length of moving object

If long power cable is used to reach deep well, then motor can be positioned at required depth, but voltage drop increases

Engineering Contradiction:

Improvecable lengthVSAvoidvoltage drop

Core Design Contradiction:

Length of moving objectVSLoss of energy

Solution Approach 1:

The control system proactively compensates for voltage drop by estimating the load angle and calculating the required voltage adjustment before it causes performance degradation. This preliminary action allows the system to maintain optimal voltage levels at the motor terminals despite the long cable length, preventing energy losses and ensuring stable operation.

Inventive Principle:

Principle #10Preliminary action

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 approach allows the PM motor to operate at or near maximum efficiency across varying loads, maintaining stability and reducing energy wastage, while being simpler to implement than vector control and more effective than conventional scalar control, ensuring efficient and stable operation from 25% to 110% of rated load and speed.

Implementation Method 1

the rotor angle corresponds to an induced electromagnetic field (EMF) within the PM motor

Methodology Applied

Scientific EffectElectromagnetic field: Electromagnetic Induction

Implementation Method 2

The VSD, also sometimes called a variable-frequency drive, adjustable frequency drive, AC drive, micro drive or inverter drive, is an adjustable speed drive used to control the speed and torque of the ESP induction motor by varying motor input frequency and voltage

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11750057B2Voltage optimization technique for a permanent magnet motor used in an electric submersible pump

Publication Date: 2023.09.05 TOSHIBA INTERNATIONAL CORP

AI summary

A method for controlling a permanent magnet (PM) synchronous motor in an ESP application is provided. A load angle of the PM motor is estimated. A voltage adjustment value is determined for the PM motor based at least on the estimated load angle of the PM motor. A voltage to be applied to the PM motor is determined based on the voltage adjustment value.