Three-Phase Power Drive Control with Sequence Harmonic Cancellation

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Solution Overview

Problem

Three-phase power systems face challenges in achieving fast dynamic response while meeting total harmonic distortion (THD) requirements due to disturbances from nonlinear or unbalanced loads, which existing repetitive control methods struggle to address effectively.

Innovation Solution

A control system comprising positive, negative, and zero sequence channels, each equipped with harmonic repetitive controllers, repetitive controller compensators, and fundamental frequency controllers, configured to process error signals in a dq coordinate system, providing distinct frequency responses to effectively manage harmonics and improve dynamic response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If traditional repetitive control is used to reject periodic harmonic disturbances, then harmonic suppression is improved, but dynamic response becomes slow

Engineering Contradiction:

Improveharmonic distortionVSAvoiddynamic response

Core Design Contradiction:

Object-generated harmful factorsVSSpeed

Solution Approach 1:

The control system is divided into three independent sequence channels (positive, negative, and zero sequence), each processing specific types of disturbances. This segmentation allows each channel to be optimized independently, enabling the positive sequence channel to achieve fast dynamic response while other channels focus on harmonic suppression, thereby resolving the contradiction between speed and harmonic rejection performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different dynamic characteristics are assigned to different sequence channels through tailored compensators. The positive sequence channel uses a compensator designed for fast transient response, while other channels use compensators optimized for their specific functions. This dynamic differentiation allows the overall system to achieve both fast response and effective harmonic suppression simultaneously.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If repetitive control with delay line and low-pass filter is implemented, then periodic signal tracking is improved, but system complexity increases

Engineering Contradiction:

Improveperiodic signal trackingVSAvoidcontroller structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The three sequence channels share common computational resources and processing architecture, allowing the system to achieve sophisticated periodic signal tracking across multiple frequency components without proportionally increasing hardware complexity. The unified structure enables multi-functionality in handling different sequence components efficiently.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Rather than implementing full repetitive control with all its complexity for all sequence channels, the invention applies selective repetitive control only where necessary (positive, negative, and zero sequence channels with specific compensators), achieving sufficient periodic signal tracking performance without excessive system complexity.

Inventive Principle:

Principle #16Partial or excessive action

3Object-generated harmful factors

If high gain is used in repetitive controller to improve harmonic rejection, then harmonic suppression is improved, but system stability becomes difficult to maintain

Engineering Contradiction:

Improveharmonic distortionVSAvoidsystem stability

Core Design Contradiction:

Object-generated harmful factorsVSStability of the object's composition

Solution Approach 1:

Each sequence channel has its own tailored compensator designed with specific frequency response characteristics. The positive sequence channel compensator is optimized for fast response with appropriate stability margins, while other channel compensators are designed for their specific harmonic rejection needs. This local optimization allows each channel to achieve high gain where needed while maintaining overall system stability through distributed design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The repetitive control structure inherently uses feedback through the delay line that feeds back the error signal from one period to the next. This feedback mechanism allows the system to gradually reduce harmonic distortion over multiple periods while maintaining stability, as the feedback loop naturally limits the effective gain at any single moment while achieving high steady-state rejection.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9048726B1Power system having repetitive control in symmetric sequences with harmonics cancellation

Publication Date: 2015.06.02 THE BOEING CO

AI summary

A control system for a power drive section of a three-phase system is disclosed. The control system comprises a positive sequence channel, a negative sequence channel, and a zero sequence channel. The positive sequence channel processes positive sequence error signals, the negative sequence channel processes negative sequence error signals, and the zero sequence channel processes zero sequence error signals. Each sequence channel includes a harmonic repetitive controller, a repetitive controller compensator, and a fundamental frequency controller configured to operate in parallel with the harmonic repetitive controller and repetitive controller compensator. Both the repetitive controller compensator of the negative sequence channel and the repetitive controller compensator of the positive sequence channel are configured with the same, first frequency response. The repetitive controller compensator of the zero sequence channel is configured with a second frequency response that is different from the first frequency response.