Three-Phase DC Power Supply Control for Power Factor and Harmonics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional direct-current power supply devices for three-phase power systems experience unbalanced currents and increased harmonic components, leading to reduced power factor and higher costs due to larger reactor sizes.
Innovation Solution
A direct-current power supply device that converts three-phase alternating current to direct current, utilizing a configuration with series-connected capacitors and a control unit to manage charging periods and charge timing with respect to the reference phase of the three-phase alternating current, thereby controlling power factor and harmonic currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching element is operated once or more in synchronization with a half period of the power supply in a three-phase power supply system, then the conduction angle of input current is increased, but the currents flowing in respective phases become unbalanced, causing reduction in power factor and increase in harmonic components
Solution Approach 1:
The patent applies periodic action by operating the switching element at a frequency that is an integer multiple of the power supply frequency. This synchronized periodic operation ensures that switching occurs at optimal moments in each cycle, maintaining balance among three-phase currents while improving power factor and reducing harmonic components through controlled timing rather than arbitrary switching.
Solution Approach 2:
The patent employs feedback control by detecting the actual current balance and power factor conditions, then adjusting the switching element's operation timing and frequency accordingly. This closed-loop control ensures that the switching element operates at frequencies that are integer multiples of the power supply frequency, maintaining optimal performance and preventing current imbalance while continuously optimizing power factor and minimizing harmonics.
2Reliability
If the switching element is operated once or more in synchronization with a half period of the power supply in a three-phase power supply system, then the conduction angle of input current is increased, but the currents flowing in respective phases become unbalanced, leading to size increase in reactor and cost increase
Solution Approach 1:
The patent applies periodic action by operating the switching element at a frequency that is an integer multiple of the power supply frequency. This synchronized periodic operation ensures that switching occurs at optimal moments in each cycle, maintaining balance among three-phase currents while improving power factor and reducing harmonic components through controlled timing rather than arbitrary switching.
Solution Approach 2:
The patent changes the operating parameters of the switching element by controlling it to operate at frequencies that are integer multiples of the power supply frequency. This parameter optimization allows the system to achieve improved power factor with smaller reactor sizes, as the controlled switching reduces current imbalance and harmonic content, thereby reducing the reactive power requirements and enabling downsizing of energy storage components.
3Reliability
If the switching element is operated once or more in synchronization with a half period of the power supply in a three-phase power supply system, then the conduction angle of input current is increased, but the currents flowing in respective phases become unbalanced, causing cost increase
Solution Approach 1:
The patent applies periodic action by operating the switching element at a frequency that is an integer multiple of the power supply frequency. This synchronized periodic operation ensures that switching occurs at optimal moments in each cycle, maintaining balance among three-phase currents while improving power factor and reducing harmonic components through controlled timing rather than arbitrary switching.
Solution Approach 2:
The patent changes the operating parameters of the switching element by controlling it to operate at frequencies that are integer multiples of the power supply frequency. This parameter optimization allows the system to achieve improved power factor with smaller reactor sizes, as the controlled switching reduces current imbalance and harmonic content, thereby reducing the reactive power requirements and enabling downsizing of energy storage components.
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
This solution improves efficiency and reduces costs by minimizing harmonic generation and optimizing power factor, allowing for smaller reactor sizes and increased cooling and heating capacities in refrigeration-cycle applications.
Implementation Method 1
a first capacitor (6b) and a second capacitor (6a) connected in series between output terminals to the load (10)
Data Source
AI summary
A direct-current power supply device is a direct-current power supply device that converts a three-phase alternating current to a direct current and supplies the direct current to a load, and includes a first capacitor and a second capacitor connected in series between output terminals to the load, a charge unit that selectively charges one or both of the first capacitor and the second capacitor, and a control unit that controls the charge unit. The control unit controls an output voltage of the direct-current power supply device by a charging period of the charge unit, and also controls a power factor and a harmonic current of the direct-current power supply device by a charge timing with respect to a reference phase of the three-phase alternating current of the charge unit as a reference.