Two-Wire Load Control Power Estimation Without Neutral Sensing
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Solution Overview
Problem
Two-wire load control devices lack the capability to accurately compute and report real-time power consumption due to the absence of a direct connection to the neutral side of the AC power source, preventing them from determining the actual voltage drop across the load.
Innovation Solution
A two-wire lighting control device is configured with a controllably conductive device and a control circuit that measures voltage across the device during a half-cycle, generates a complementary voltage waveform to approximate the voltage across the load, and computes power consumption based on this estimation and current measurement, enabling accurate power estimation without a neutral connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-wire load control device is used, then the device complexity is reduced and installation is simplified, but the measurement precision of power consumption is lost due to inability to directly measure voltage across the load
Solution Approach 1:
The patent creates a complementary voltage waveform that copies the characteristics of the actual load voltage during the off-period. This complementary waveform serves as a substitute measurement signal that enables power calculation without direct voltage measurement across the load during the on-period, thus maintaining measurement precision while using simplified two-wire connectivity.
Solution Approach 2:
The patent measures and stores voltage characteristics during the off-period (when the load control device is non-conductive) before the actual power delivery period. This preliminary measurement of voltage across the device during the off-period enables subsequent calculation of power consumption during the on-period without requiring direct measurement during power delivery.
2Measurement precision
If voltage measurement is performed across the two-wire device during non-conductive period, then power consumption can be estimated, but the voltage measured is not the actual voltage across the load during conductive period
Solution Approach 1:
The patent uses the measured voltage across the device during the off-period as feedback to generate a complementary waveform. This complementary waveform is then used in conjunction with current measurements to calculate power consumption, creating a feedback-based estimation system that recovers load voltage information indirectly through the relationship between device voltage and load voltage.
Solution Approach 2:
The patent changes the measurement parameter from direct load voltage (unavailable during on-period) to device voltage (available during off-period). By measuring voltage across the control device when it is non-conductive, and then using this measurement to derive complementary waveform parameters, the system transforms an unavailable measurement into a usable one through parameter transformation.
Data Source
AI summary
A two-wire load control device may be configured to compute an accurate estimate of real-time power consumption by a load that is electrically connected to, and controlled by, the two-wire load control device. The load control device may be adapted to measure a voltage drop across the device during a first portion of a half-cycle of an AC waveform provided to the device. The device may be further configured to estimate a voltage drop across the load during the second portion of the half-cycle. The estimated voltage drop may be based on the measured voltage drop. The device may be further configured to measure a current supplied to the load during a second portion of the half-cycle. The device may be configured to estimate power consumed by the load based on the measured current and the estimated voltage drop.