Inverter Control Device for Shared DC Bus Ripple Reduction
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Solution Overview
Problem
Existing inverter control methods for multiple motors using shared direct current voltage bus lines face challenges in reducing switching loss and ripple current, leading to increased costs due to larger smoothing capacitors, and increased operational load from separate carrier waves for each motor.
Innovation Solution
An inverter control device and method that regulates the phases of inverter outflow currents to smooth the power supply voltage using a smoothing control unit and modulated wave level regulating unit, reducing switching loss and the size of the smoothing capacitor by optimizing two-phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two-phase modulation is used to reduce switching loss, then switching loss is reduced, but ripple of direct current bus line voltage increases
Solution Approach 1:
The patent combines the control of multiple inverters into a unified system where a single carrier wave is shared across all inverters. By coordinating the switching timing of multiple inverters using the same carrier wave, the system merges their output current contributions to smooth the overall direct current bus line voltage ripple while maintaining reduced switching loss through two-phase modulation.
Solution Approach 2:
The patent employs periodic switching actions with specifically designed phase differences between multiple inverters. By setting appropriate phase differences in the periodic switching patterns of multiple inverters using two-phase modulation, the system causes current pulses to complement each other over time, reducing the peak ripple current while maintaining the benefits of reduced switching frequency.
2Object-generated harmful factors
If separate carrier waves are used for each motor to smooth voltage, then voltage smoothing is achieved, but operation load increases
Solution Approach 1:
The patent makes a single carrier wave serve multiple functions by using it to control all inverters simultaneously. This universal carrier wave approach allows one signal to coordinate the switching of multiple inverters, achieving voltage smoothing across the entire system without requiring separate carrier wave generation and processing for each inverter, thereby reducing computational and operational load.
Solution Approach 2:
The patent merges the carrier wave generation and distribution function into a single unified approach. Instead of each inverter having its own independent carrier wave, the system combines them into one shared carrier wave that is distributed to all inverters, reducing the overall operational complexity and load while maintaining the ability to smooth voltage through coordinated switching.
3Object-generated harmful factors
If inverter outflow current pulses are displaced to smooth direct current voltage, then voltage smoothing is achieved, but device complexity increases
Solution Approach 1:
The patent achieves voltage smoothing by changing the phase angle parameter of the carrier wave for each inverter relative to a common reference. By simply adjusting phase angle parameters rather than implementing complex control logic or additional hardware components, the system displaces inverter outflow current pulses to complement each other, reducing ripple while maintaining simple device configuration.
Data Source
AI summary
An inverter control device that controls a multiple of inverters configured to use the same positive and negative direct current voltage bus lines connected to a power supply and driving a corresponding multiple of motors, the inverter control device including smoothing control means that controls an inverter outflow current so that voltage of the power supply is smoothed by a smoothing capacitor connected to the positive and negative direct current voltage bus lines, and two-phase modulation operation means that fixes a predetermined one phase of a three-phase modulated wave at either a maximum voltage or minimum voltage the inverter can output determined by a voltage between the positive and negative direct current voltage bus lines, and calculates a modulated wave that causes the other two phases to switch.