ABC Frame Grid-Tied Converter Power Control Without dq Transformation

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Solution Overview

Problem

Existing control techniques for grid-tied converters, such as those used in electrical vehicle battery chargers, face high computational burdens and electromagnetic compatibility issues due to the need for dq transformation in balanced grid assumptions, leading to increased CPU load and harmonic distortion.

Innovation Solution

A method for direct active and reactive power control in the ABC frame without transformation, where active power is controlled by managing battery charging and discharging currents, and reactive power is controlled by adjusting the phase shift between Power Factor Correction (PFC) current and voltage, using a linearized control loop to reduce computation and enhance harmonic content.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dq transformation is used for active and reactive power control, then power factor correction is achieved, but CPU load increases and computation burden rises

Engineering Contradiction:

Improvepower factor correctionVSAvoidCPU load

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and removes the dq transformation step from the control algorithm, working directly in the ABC frame. This eliminates the computationally intensive coordinate transformation while maintaining the ability to control active and reactive powers independently through direct manipulation of three-phase currents.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The control algorithm is segmented into independent per-phase processing, where each phase is controlled separately to achieve overall power factor correction. This segmentation allows parallel computation and reduces the need for complex global transformations, thereby lowering CPU burden.

Inventive Principle:

Principle #1Segmentation

2Reliability

If dq transformation is used for power control, then active and reactive powers are controlled, but harmonic content increases and electromagnetic compatibility problems occur

Engineering Contradiction:

Improvepower controlVSAvoidharmonic content

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potential harm of direct ABC frame control into benefit by using it to generate cleaner current waveforms. By avoiding dq transformation, the method eliminates the source of harmonic distortion and electromagnetic interference, resulting in improved EMC performance while maintaining effective power control.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces the mathematical transformation mechanism (dq transformation) with a direct control approach in the ABC frame. This substitution eliminates the computational complexity and harmonic generation associated with coordinate transformations while achieving the same power control objectives.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If dq transformation is used, then control is simplified for balanced grids, but the system becomes complex for unbalanced grids requiring tripled control loops

Engineering Contradiction:

Improvecontrol simplicityVSAvoidhandling unbalanced grids

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal control algorithm that functions effectively for both balanced and unbalanced grid conditions. By working directly in the ABC frame without dq transformation, the method inherently handles unbalanced conditions without requiring separate control loops or sequence decomposition, making it adaptable to various grid scenarios.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Device complexity

If Direct Power Control (DPC) is used, then computation burden is reduced, but electromagnetic compatibility problems arise due to hysteresis-based control

Engineering Contradiction:

Improvecomputation burdenVSAvoidelectromagnetic compatibility issues

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary control layer between the power control objectives and the switching actions. Instead of using hysteresis-based direct switching, the method employs a controlled modulation approach that mediates between the desired power flow and the actual switching, thereby reducing electromagnetic interference while maintaining computational efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20230318297A1Method of active and reactive power control in abc frame of a grid-tied converter

Publication Date: 2023.10.05 WATT & WELL

AI summary

A method for controlling active and reactive powers in grid-tied converters having a grid side and a battery side, in which said grid side supplies an alternative current to said converter whereas the battery side receives a direct current from said converter, said method comprising direct active and reactive power control in ABC frame where no transformation is used, and wherein active power is controlled by controlling the battery charging and discharging currents, and reactive power is controlled by controlling the phase shift between power factor correction current and voltage.