Power Converter Current Detection via Neutral Point Merging
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Solution Overview
Problem
Existing power converting devices for multi-phase winding alternating current motors face challenges in reducing the number of current detectors, leading to increased size and weight, and higher harmonic issues due to voltage command restrictions.
Innovation Solution
A power converting device using bridge-connected switching elements with a reduced number of current detectors, where each detector measures the total current of two phases, and a power converter controller generates PWM signals with phase-shifted carrier signals to control the switching elements, allowing for efficient current detection and reduced harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the number of current detectors is reduced to minimize size and weight, then the size and weight of the power converting device are reduced, but current detection accuracy and control stability deteriorate
Solution Approach 1:
The patent merges current detection for multiple phases into a single current detector by utilizing the neutral point connection. Specifically, it detects the sum of currents flowing through switching elements in different phases (e.g., Ru = ia1 + ia2 for U-phase, Rv = ib1 + ib2 for V-phase) using one detector connected to the neutral point, thereby reducing the number of detectors while maintaining detection capability through mathematical relationships.
Solution Approach 2:
The patent introduces the neutral point as an intermediary element that enables current detection. By connecting the current detector to the neutral point formed by winding groups, it creates a common reference point through which combined phase currents can be measured, allowing indirect detection of individual phase currents via calculation.
2Device complexity
If voltage command restrictions are applied to enable current detection with reduced detectors, then the number of current detectors is reduced, but harmonic distortion increases
Solution Approach 1:
The patent dynamically adjusts PWM control parameters based on the reduced current detection configuration. It modifies switching sequences and carrier signal phases adaptively to ensure that states where voltage is applied to all phase windings and states where counter electromotive force refluxes do not occur consecutively, thereby optimizing current detection timing and reducing harmonic distortion dynamically.
Solution Approach 2:
The patent changes control parameters including carrier signal phase shifts, PWM switching sequences, and voltage command timing to accommodate the reduced detector configuration. By adjusting these parameters, it ensures accurate current detection while minimizing harmonic distortion without requiring additional hardware.
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 configuration reduces the number of current detectors, minimizing the size and weight of the power converting device while ensuring stable power supply and accurate current detection, thereby improving motor control and reducing harmonic distortion.
Implementation Method 1
PWM control is carried out so that each PWM control unit executes a switching sequence such that a state wherein a power supply voltage is applied across the phase winding relating to the corresponding power converter
Implementation Method 2
a value of current flowing through the corresponding phase winding is detected, a deviation from a current command value is calculated
Data Source
AI summary
In order to reduce the number of current detectors detecting phase current in a power converting device that controls a power converter connected to a motor, thereby achieving a size reduction, the power converting device includes a current detector that detects, of winding groups of multi-phase windings, a total value of values of current flowing into a first switching element connected to a first phase of a first winding group and a second switching element connected to a second phase of a second winding group, and calculates a current value of another phase from current detected by the current detector.