Three-Phase AC to DC Converter Phase Detection PWM Control
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Solution Overview
Problem
Three-phase AC to DC converters in existing technologies have low followability with voltage changes, leading to harmonic leakage current and noise, and require costly current sensors with through-type configurations, especially when applied to air-conditioning apparatuses with inverter loads.
Innovation Solution
A three-phase AC to DC converter design featuring a three-phase full-bridge circuit with serially-connected switching devices, reverse blocking diodes, a reactor, smoothing capacitor, power supply phase detection, and pulse width modulation (PWM) control based on power supply phase and output voltage to reduce harmonic leakage current and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensors are used to detect phase currents for controlling switching devices, then the converter can operate with basic control capability, but the followability with voltage changes is low and the system is susceptible to sensor characteristics such as frequency response and temperature drift
Solution Approach 1:
The patent replaces current sensors with a current sensorless control mechanism that uses voltage detection and mathematical modeling to determine switching device states. The control circuit detects voltage across switching devices and uses this information to control operation without physical current sensors, thereby eliminating sensor-related limitations while maintaining control reliability.
2Difficulty of detecting and measuring
If through-type current sensors are used to measure current, then current detection is possible, but the mounting cost and sensor cost increase due to the need to insert the current path through the sensor
Solution Approach 1:
The patent extracts the current detection function from physical current sensors and implements it through voltage measurement and control circuit processing. By removing the current sensor component entirely and using voltage detection across switching devices combined with control signal analysis, the system achieves current detection capability without the mounting complexity and cost of through-type current sensors.
3Device complexity
If basic rectifier circuits are used without PWM control, then the circuit structure is simple, but harmonic leakage current and noise generation occur
Solution Approach 1:
The patent implements dynamic PWM control of switching devices based on detected voltage conditions and control signals. This dynamic switching control allows the circuit to maintain simple structure while actively managing current flow to reduce harmonic leakage and noise, transitioning from static rectifier operation to dynamic controlled operation.
Solution Approach 2:
The control circuit uses feedback from detected voltage across switching devices to adjust switching timing and duration. This feedback mechanism enables the system to maintain simple circuit structure while actively compensating for harmonic leakage current and noise through real-time control adjustments based on actual operating conditions.
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 effectively reduces harmonic leakage current and noise levels while simplifying the sensor configuration and improving followability with voltage changes, making it suitable for air-conditioning apparatuses with inverter loads.
Implementation Method 1
a reactor that connects a connection point between the two serially-connected switching devices of each phase to a corresponding phase of the three-phase AC power supply
Implementation Method 2
a smoothing capacitor connected between the DC buses at an output side of the three-phase full-bridge circuit
Implementation Method 3
a three-phase rectifier bridge circuit that is connected to the three-phase AC power supply and that includes rectifying devices which are connected in a bridge configuration between two DC buses
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
To provide a three-phase AC to DC converter capable of reducing harmonic leakage current and the noise level, and an air-conditioning apparatus using the three-phase AC to DC converter. A three-phase AC to DC converter includes a three-phase AC power supply, a three-phase rectifier bridge circuit that is connected to the three-phase AC power supply and includes rectifying devices which are connected in a bridge configuration, a three-phase full-bridge circuit that includes two serially-connected switching devices for each of three phases, the two serially-connected switching devices being connected at an output side of the three-phase rectifier bridge circuit, and includes reverse blocking diodes which are connected in parallel to the respective switching devices, a reactor that connects the three-phase full-bridge circuit to the three-phase AC power supply, a smoothing capacitor connected to an output side of the three-phase full-bridge circuit, DC voltage detection means that detects an output voltage, power supply phase detection means that detects a power supply phase of the three-phase AC power supply, and pulse width modulation means that outputs PWM signals which control the switching devices. The pulse width modulation means outputs the PWM signals on the basis of the power supply phase and the output voltage.