Two-Wire Load Control Power Measurement Using Half-Cycle Voltage Estimation
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Solution Overview
Problem
Existing two-wire load control devices cannot accurately compute the real-time power consumption of a load since they lack the necessary voltage measurement across the load.
Innovation Solution
A two-wire lighting control device is designed with a controllably conductive device and a control circuit that measures voltage across the device during one half-cycle and generates a complementary voltage waveform to estimate the voltage across the load during the other half-cycle, allowing for computation of real-time power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-wire load control device is used, then the device complexity is reduced, but the measurement precision of power consumption is insufficient
Solution Approach 1:
The patent applies preliminary action by measuring the voltage across the load during the off-state (when the triac is non-conductive) before the power delivery phase. This preliminary voltage measurement is stored and then used during the on-state to calculate power consumption, eliminating the need for simultaneous voltage and current measurements during power delivery. This resolves the contradiction by enabling accurate power measurement in a simple two-wire configuration without requiring complex measurement circuits during the conductive state.
2Measurement precision
If voltage measurement across the load is implemented in real-time, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent measures voltage during the off-state before power delivery occurs, storing this voltage value for later use during the on-state. This eliminates the need for complex real-time voltage measurement circuits during power delivery, as the voltage is predetermined and stored. The solution achieves accurate power measurement by combining this preliminary voltage measurement with current measurement during the on-state, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The load control device uses its own operational states (on-state and off-state) to facilitate measurement. During the off-state, the device naturally blocks current flow, creating an opportunity to measure voltage across the load without requiring additional measurement infrastructure. This self-service approach leverages the device's inherent operational characteristics to enable accurate power measurement while maintaining simplicity.
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.