Heat pump device, heat pump system, and method for controlling three-phase inverter
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Solution Overview
Problem
Existing heating methods for compressors in heat pump devices face inefficiencies, including non-uniform heating due to open-phase currents and limitations in generating high-frequency currents, which restrict power efficiency and introduce noise.
Innovation Solution
A heat pump device with a three-phase inverter and an inverter control unit that generates high-frequency AC voltage by switching between phases θp and θn, correcting voltage command values to prevent DC excitation and ensure accurate waveform output, thereby efficiently heating refrigerant while minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If open-phase current is caused to flow to warm the motor winding, then the compressor can be heated, but the heating is non-uniform and the compressor cannot be uniformly heated
Solution Approach 1:
The patent segments the heating process by applying high-frequency voltage to each phase winding separately through controlled switching of the inverter. By dividing the three-phase system into individual phase control and applying voltage sequentially or in controlled combinations, the heating is distributed more uniformly across all windings rather than concentrating current in a single phase as with open-phase methods.
Solution Approach 2:
The patent changes the frequency parameter of the applied voltage to high-frequency range. This high-frequency AC voltage generates iron losses and copper losses that produce uniform heating throughout the motor windings and compressor components, overcoming the non-uniform heating limitation of low-frequency open-phase current methods.
2Use of energy by moving object
If open-phase current is caused to flow using an inverter, then current can be applied to the motor, but the winding inductance depends on rotor position making it difficult to cause open-phase current to flow
Solution Approach 1:
The patent employs dynamic control of the inverter switching elements to adapt to the changing rotor position. The control system continuously monitors or estimates rotor position and adjusts the switching patterns accordingly, enabling reliable application of high-frequency voltage despite the position-dependent inductance characteristics of the motor windings.
Solution Approach 2:
The patent changes the frequency parameter to high-frequency range, which alters the electrical characteristics of the motor windings. At high frequencies, the impedance is dominated by inductive reactance, and the control strategy uses this characteristic to overcome the position-dependent inductance issue that plagues low-frequency open-phase current methods.
3Loss of energy
If switching elements are repeatedly switched on/off to reverse current direction, then heat generation occurs, but the current frequency cannot be made high enough to generate sufficient iron loss and efficiency cannot be improved
Solution Approach 1:
The patent uses periodic switching of the inverter elements to generate high-frequency AC voltage. By switching at high frequency (typically several kHz), the system generates both copper losses (I²R heating) and iron losses (hysteresis and eddy current losses in the motor core), achieving efficient heating through combined loss mechanisms rather than relying solely on resistive heating at low frequencies.
Solution Approach 2:
The patent fundamentally changes the frequency parameter from low-frequency periodic reversal to high-frequency AC voltage application. This parameter change enables significant iron loss generation in the motor windings and core, dramatically improving heating efficiency compared to low-frequency methods that rely primarily on ohmic heating.
4Productivity
If high-frequency AC voltage is generated by switching between phases, then efficient heating is achieved, but noise and shaft vibrations are generated
Solution Approach 1:
The patent uses carefully designed periodic switching patterns that synchronize with the motor's electrical cycles. By controlling the switching frequency and duty cycle, the system generates high-frequency voltage for efficient heating while avoiding resonant frequencies that would amplify mechanical vibrations and noise. The periodic action is optimized to separate electrical heating effects from mechanical disturbance.
Solution Approach 2:
The patent optimizes the frequency parameter to a range that maximizes heating efficiency while minimizing mechanical resonance. By selecting high-frequency voltage (typically above audible range) and controlling the switching harmonics, the system achieves efficient heating through iron and copper losses while suppressing noise and vibration that occur at lower, resonant frequencies.
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
The solution enables efficient heating of refrigerant in compressors with reduced noise and shaft vibrations, improving power efficiency and uniform heating regardless of rotor position.
Implementation Method 1
the inverter control unit causes the three-phase inverter to generate a high-frequency AC voltage
Implementation Method 2
heat generation due to hysteresis loss is performed so that sufficient preheating can be performed
Data Source
AI summary
A selection unit switches between a phase θp and a phase θn different from the phase θp substantially by 180 degrees, and outputs one of them in synchronization with a carrier signal. A voltage-command generation unit generates and outputs three-phase voltage command values Vu*, Vv* and Vw* based on the phase outputted by the selection unit. A PWM-signal generation unit generates three-phase voltage command values Vu*′, Vv*′ and Vw*′ by correcting the three-phase voltage command values Vu*, Vv* and Vw* outputted by the voltage-command generation unit according to a predetermined method, and generates six drive signals corresponding to switching elements of the inverter based on the three-phase voltage command values Vu*′, Vv*′ and Vw*′ and the carrier signal. The PWM-signal generation unit outputs the generated drive signals to the corresponding switching elements of the three-phase inverter, to cause the inverter to generate a high-frequency AC voltage.