Heat Pump Compressor Speed Control for External Power Limit Compliance
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Solution Overview
Problem
Existing methods for managing electrical power consumption of electrically driven heat pumps, particularly during peak load periods, result in grid instability and significant customer discomfort due to complete shutdowns or oversizing of systems, without allowing for gradual power adjustments.
Innovation Solution
A method combining a temperature setpoint controller with a power limiting controller to predict and adjust compressor power consumption based on external limits, using correction values and predictive algorithms to ensure compliance with power limits while maintaining thermal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor is completely switched off during peak load periods to reduce electrical power consumption, then grid stability is improved, but customer comfort deteriorates due to loss of thermal energy supply
Solution Approach 1:
The patent applies dynamics by transitioning from a static binary control state (compressor fully on or fully off) to a dynamic continuous control state where the compressor speed can be adjusted to any value within its operating range. The control unit continuously modulates the compressor speed based on real-time power consumption measurements and external power limit signals, enabling gradual adaptation to grid conditions while maintaining thermal energy supply at reduced but non-zero levels, thus resolving the contradiction between grid stability and customer comfort.
2Use of energy by moving object
If the compressor speed is reduced to match external power limits, then electrical power consumption is reduced to comply with grid constraints, but thermal output decreases affecting heating performance
Solution Approach 1:
The patent applies parameter changes by systematically adjusting the compressor speed parameter in response to changing power consumption requirements. The control unit monitors electrical power consumption and externally received power limits, then modifies the compressor speed parameter to achieve the target power consumption level. This dynamic parameter adjustment allows the system to comply with external power constraints while maintaining optimal thermal output within the available power envelope, resolving the contradiction between energy consumption reduction and productivity maintenance.
3Productivity
If a predictive function is used to determine compressor power requirements before startup, then compressor operation can be optimized to meet power limits, but system complexity increases due to additional control algorithms
Solution Approach 1:
The patent applies preliminary action by implementing a predictive function that calculates the expected power consumption before the compressor actually starts operating. This prediction is based on ambient conditions, desired temperature differentials, and compressor characteristics. By determining the anticipated power requirements in advance, the system can pre-assess whether compressor startup is permitted under current external power limits, and pre-adjust operational parameters to ensure compliance. This preliminary calculation approach optimizes compressor operation efficiency while keeping the control system relatively simple through use of established thermodynamic relationships and lookup tables.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables energy suppliers to manage power consumption effectively, reducing grid instability and minimizing customer discomfort by allowing controlled thermal output adjustments.
Implementation Method 1
ambient heat is transferred to the refrigeration circuit via the fan and the air/refrigerant heat exchanger
Implementation Method 2
The electrically driven compressor then raises the pressure (or 'pumps') the heat to a higher energy level
Implementation Method 3
finally makes it available as usable heat via the refrigerant/water heat exchanger
Data Source
Figure 1
Figure 2
AI summary
The procedure consists of the following steps: checking whether an external power limit exists, checking whether the compressor is out of service if both conditions are met, predicting the compressor power requirement using a central control unit, then checking whether the determined compressor power requirement is above the external power limit and whether starting the compressor is possible, then starting the compressor if the determined compressor power requirement is below the external power limit. If the compressor is in operation and an external power limit exists, then limiting the compressor speed to the power consumption corresponding to the external power limit, checking whether the external power limit is below the minimum compressor power requirement, checking whether protective functions prevent shutdown, if not: shutting down the compressor, otherwise continuing the protective operation.