Control systems and methods for heat pump systems

Solution Overview

Problem

Existing heat pump systems face inefficiencies and accumulator flooding due to inadequate control of expansion valves, particularly when compressor speed changes, leading to reduced system performance and reliability.

Innovation Solution

Implementing a system controller with a proportional-integral-derivative (PID) controller and feedforward control elements, utilizing gain scheduling based on ambient temperature and compressor speed to precisely control the expansion valves, preventing accumulator flooding and maintaining optimal superheat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional expansion valve control is used in heat pump systems, then the system structure remains simple, but accumulator flooding occurs and system efficiency decreases

Engineering Contradiction:

Improveprevention of accumulator floodingVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The feedforward control element anticipates changes in compressor speed and proactively adjusts the expansion valve opening command before flooding can occur. By detecting compressor speed changes and preemptively modifying valve positioning, the system prevents accumulator flooding rather than merely reacting to it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The PID controller continuously monitors system parameters including expansion valve opening position and compressor speed, comparing actual values against desired setpoints. The controller dynamically adjusts the expansion valve opening command based on the error between actual and target values, ensuring precise control while preventing flooding conditions.

Inventive Principle:

Principle #23Feedback

2Productivity

If expansion valves are not precisely controlled, then the control system remains simple, but system efficiency and COP are reduced

Engineering Contradiction:

Improvesystem efficiencyVSAvoidcontrol system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The feedforward control element anticipates changes in compressor speed and proactively adjusts the expansion valve opening command before flooding can occur. By detecting compressor speed changes and preemptively modifying valve positioning, the system prevents accumulator flooding rather than merely reacting to it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The PID controller continuously monitors system parameters including expansion valve opening position and compressor speed, comparing actual values against desired setpoints. The controller dynamically adjusts the expansion valve opening command based on the error between actual and target values, ensuring precise control while preventing flooding conditions.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If expansion valve control does not account for compressor speed changes, then the control algorithm remains simple, but superheat control becomes inefficient

Engineering Contradiction:

Improvesuperheat control precisionVSAvoidcontrol algorithm complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The feedforward control element anticipates changes in compressor speed and proactively adjusts the expansion valve opening command before flooding can occur. By detecting compressor speed changes and preemptively modifying valve positioning, the system prevents accumulator flooding rather than merely reacting to it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The PID controller continuously monitors system parameters including expansion valve opening position and compressor speed, comparing actual values against desired setpoints. The controller dynamically adjusts the expansion valve opening command based on the error between actual and target values, ensuring precise control while preventing flooding conditions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11137164B2Control systems and methods for heat pump systems

Publication Date: 2021.10.05 CARRIER CORP

AI summary

Heat pump systems and methods of operating including a first unit having a first unit heat exchanger, a compressor, an accumulator, and a first unit expansion valve, a second unit fluidly connected to the first unit by piping, the second unit having a second unit heat exchanger, and a system controller, the system controller having (I) a PID control element receiving as inputs (i) gain scheduling, (ii) an error signal, and (iii) feedback relating to an opening command of the first unit expansion valve, and (II) a feedforward control element generating a feedforward term that is combined with an output of the PID control element to generate the opening command of the first unit expansion valve. The system controller controls an opening of the first unit expansion valve using the opening command of the first unit expansion valve.