Load Control Relay Cycle Adjustment for Thermostat Delay Compensation

Solution Overview

Problem

Thermostat delays in HVAC systems lead to extended periods of load shedding, causing discomfort and inefficiency in demand response systems, as the thermostat protection timer delays power restoration to HVAC loads even after the load control relay is closed.

Innovation Solution

A system and method that measures the thermostat delay time and adjusts the cycle shed and restore times for the load control relay to compensate for this delay, ensuring that HVAC loads receive power for the maximum intended duration by modifying the commanded cycle percentages based on real-time operation data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thermostat protection timer is used to delay power restoration after LCR closure, then utility grid stability is improved, but load shedding duration is extended causing user discomfort

Engineering Contradiction:

Improveutility grid stabilityVSAvoidload shedding duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary action by measuring the thermostat delay time in advance during initial operation. This measured delay time is then stored and used to pre-calculate adjusted cycle parameters before actual demand response events occur, allowing the LCR controller to compensate for the delay proactively rather than reactively

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring the actual power restoration timing and using this information to refine the measured thermostat delay time. This feedback loop ensures that the delay measurement remains accurate and that cycle parameter adjustments remain effective in compensating for thermostat delays

Inventive Principle:

Principle #23Feedback

2Loss of time

If cycle parameters are adjusted to compensate for thermostat delay, then load shedding duration is reduced, but control system complexity increases

Engineering Contradiction:

Improveload shedding durationVSAvoidcontrol system complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The system applies parameter changes by modifying the cycle parameters (cycle duration, on-time, off-time) based on the measured thermostat delay time. The LCR controller calculates adjusted parameters that account for the delay, ensuring that the effective load control duration matches the intended duration despite the thermostat's delayed response

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements self-service by automatically measuring the thermostat delay time during normal operation and using this measurement to self-adjust the cycle parameters. The LCR controller performs these calculations and adjustments autonomously without requiring external intervention or complex external control systems

Inventive Principle:

Principle #25Self-service

3Ease of operation

If LCR is controlled with standard cycle percentages, then system operation is simple, but actual load control duration is reduced due to thermostat delay

Engineering Contradiction:

Improvesystem operation simplicityVSAvoidload control duration

Core Design Contradiction:

Ease of operationVSDuration of action of moving object

Solution Approach 1:

The system performs preliminary action by measuring the thermostat delay time in advance during initial operation. This measured delay time is then stored and used to pre-calculate adjusted cycle parameters before actual demand response events occur, allowing the LCR controller to compensate for the delay proactively rather than reactively

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring the actual power restoration timing and using this information to refine the measured thermostat delay time. This feedback loop ensures that the delay measurement remains accurate and that cycle parameter adjustments remain effective in compensating for thermostat delays

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10295212B2Load control system and method for regulating power supply to a thermostat

Publication Date: 2019.05.21 EATON INTELLIGENT POWER LTD

AI summary

A system for controlling a load control relay (LCR) supplying power to a thermostat of a heating, ventilating, and air conditioning (HVAC) system includes a controller programmed to maximize the amount of time that a load of the HVAC system may receive power. The controller operates by measuring a thermostat delay time of the thermostat and modifying cycle shed and restore times for controlling the LCR based on the measured thermostat delay time. By controlling the LCR according to the modified cycle shed and restore times, the controller compensates for the thermostat delay time, and the load is able to be active for a longer period of time than it otherwise would be when operating under demand-response controls.