Power Converter Neutral Line Elimination
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Solution Overview
Problem
Existing power converters using three-phase AC power supplies face issues with noise leakage due to the neutral line and require high-voltage insulation and step-down circuits, increasing component count and complexity.
Innovation Solution
A power converter design that eliminates the need for a step-down circuit and reduces noise components by using series-connected capacitors between two phases of the three-phase AC power lines, allowing for a lower withstand voltage and eliminating the neutral line, thereby simplifying the power supply unit and reducing noise filtering requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-phase four-wire AC power supply including neutral line is connected to the power converter, then the power supply unit can obtain power supply, but noise generated in the power converter leaks from all four lines including the neutral line to an outside (power supply system), requiring noise removing components such as noise filters
Solution Approach 1:
The invention extracts and eliminates the neutral line from the power supply connection, transitioning from a three-phase four-wire system to a three-phase three-wire system. By removing the neutral line connection, the path for noise leakage is eliminated, and the power supply unit obtains power from only the three phase lines (R, S, T), thereby preventing noise from leaking to the power supply system while maintaining reliable power supply.
Solution Approach 2:
The invention changes the power supply configuration parameter from four-wire (including neutral) to three-wire (phase lines only). This parameter change fundamentally alters the noise propagation path, eliminating the neutral line as a noise conduit while maintaining sufficient power supply capability for the drive control unit through the three phase lines.
2Object-generated harmful factors
If power is obtained from any two phases among three phases without using the neutral line, then noise leakage is reduced, but the power supply unit has to convert the three-phase line voltage to a desired power supply voltage, requiring consideration of insulation measures for high voltage (200 V or 400 V), withstand voltage of elements, and addition of a step-down circuit
Solution Approach 1:
The invention utilizes all three phase lines (R, S, T) for power supply purposes, making the power supply system multi-functional. The three phase lines simultaneously provide both the power supply voltage and the neutral reference point for the power supply unit, eliminating the need for separate step-down circuits and insulation measures while maintaining low noise leakage.
Solution Approach 2:
The invention creates a virtual neutral point by connecting capacitors between the three phase lines, which copies the function of a physical neutral line without requiring actual neutral line connection. This virtual neutral point provides the necessary reference potential while avoiding the noise leakage issues associated with physical neutral line connections.
3Reliability
If a step-down circuit is added to convert three-phase line voltage to desired power supply voltage, then the power supply unit can operate at lower voltage, but the device complexity increases and noise removing components are required
Solution Approach 1:
The invention enables the power supply unit to directly utilize the three-phase line voltage without external step-down circuits. The power supply unit itself performs the voltage conversion function by using the three phase lines and capacitor network to generate the required power supply voltage, making the system self-sufficient and eliminating additional complexity.
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 design reduces the number of noise removing components and lowers the required withstand voltage, allowing for a more compact and cost-effective power supply unit with reduced insulation needs, while maintaining effective noise suppression.
Implementation Method 1
two capacitors that are connected in series between one phase power line and another phase power line among the three-phase AC power lines
Data Source
Figure 1
Figure 2
AI summary
A power converter (1) includes: a power conversion module (11) that converts input three-phase AC power to desired power output state and outputs the desired power; a drive control unit (15) that drives an active element (11a) included in the power conversion module (11); a power supply unit (12) that generates a power supply voltage for use in the drive control unit (15) and outputs the power supply voltage to the drive control unit (15); a T-phase power line (23) of input three-phase AC power lines (20); filter capacitors (C1), (C2), and (C3) that are connected by star connection to the three-phase AC power lines (20) ; and power supply lines (LN) that are respectively connected between the T-phase power line (23) and the power supply unit (12) and between the filter capacitors (C1), (C2), and (C3) and the power supply unit (12) to supply power to the power supply unit (12).