Active Negative Reactance Synthesis for Stable AC Compensation

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Solution Overview

Problem

Existing technologies lack a practical solution for synthesizing standalone negative reactance, which is essential for effectively canceling unwanted or excessive reactance in AC power transmission and wireless power transfer systems without complicating the design or risking equipment damage.

Innovation Solution

A negative reactance synthesizer is developed, comprising a DC power source, converters for shaping input currents and voltages, and control circuitry to generate gate driver signals. This setup emulates a pure negative inductance or capacitance, achieving a high input power factor and stabilizing power imbalance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If inductors or capacitors are added for compensation, then the power factor and efficiency are improved, but the design complexity increases and system stability deteriorates due to harmonic resonance risks

Engineering Contradiction:

Improvepower factor and efficiencyVSAvoiddesign complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent replaces passive inductor/capacitor compensation with an active power electronics-based negative reactance synthesizer. The synthesizer uses a converter circuit with control circuitry to generate negative reactance, substituting the traditional mechanical/passive compensation approach with an electronically controlled solution that dynamically adjusts to maintain power factor without adding physical reactance components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental parameter approach by generating negative reactance values through controlled power conversion rather than using fixed positive reactance components. The control circuitry dynamically adjusts the negative reactance magnitude to match and cancel the unwanted positive reactance, enabling adaptive compensation that maintains stability across varying operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If inductors or capacitors are added for compensation, then the power factor is improved, but the system stability deteriorates due to harmonic resonance

Engineering Contradiction:

Improvepower factorVSAvoidsystem stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent replaces passive resonant compensation with active negative reactance synthesis. The converter-based synthesizer actively generates negative reactance to cancel positive reactance without creating resonant conditions, substituting the passive L/C resonance approach with an electronically controlled cancellation method that inherently avoids resonance instability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements feedback control through the control circuitry that continuously monitors the system's positive reactance and adjusts the negative reactance generation accordingly. This closed-loop control ensures stable compensation by dynamically matching the negative reactance to the actual positive reactance conditions, preventing resonance and maintaining system stability.

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If gyrator-based circuits are used to synthesize negative reactance, then small-signal negative reactance is achieved, but the application scope is limited due to voltage supply limits and operational frequency constraints

Engineering Contradiction:

Improvenegative reactance synthesis precisionVSAvoidapplication scope

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces the gyrator-based operational amplifier circuit with a power electronics converter system. This substitution eliminates the voltage supply limits and frequency constraints of operational amplifiers, enabling the negative reactance synthesizer to operate across a wide range of power frequencies and voltage levels suitable for both signal processing and power transfer applications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a universal negative reactance synthesizer that can function in both signal processing and power transfer applications. The converter-based design with controllable switches and energy storage elements provides multi-functionality, adapting to different operating conditions and application requirements without the limitations of gyrator circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250119117A1Negative Reactance Synthesizer

Publication Date: 2025.04.10 CITY UNIVERSITY OF HONG KONG

AI summary

The present invention provides a negative reactance synthesizer comprising: a DC power source; a first converter configured for shaping an input current under an AC input voltage that has a given peak value and converting a variable DC voltage to a fixed DC voltage; a second converter configured for converting the fixed DC voltage to a stack-up DC voltage being greater than the peak value of the AC input voltage and stacked on the AC input voltage to form the variable DC voltage; a first control circuitry configured to generate a first gate driver signal and a first complementary gate drive signal for controlling the first converter; and a second control circuitry configured to generate a second gate driver signal and a second complementary gate drive signal for controlling the second converter. The present invention provides a simple and low-cost solution to emulate a standalone negative reactance.