Frequency Converter DC/DC Inverter Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing frequency converters face inefficiencies in generating adjustable output voltages for electric motors, particularly at low rotational speeds, leading to increased torque ripple and high power losses due to fundamental clocking and block clocking.
Innovation Solution
A frequency converter design incorporating a clocked DC/DC converter and inverter with controllable switches, utilizing a precontrol or modulation signal to adjust the DC/DC converter output voltage level and inverter switching frequency, allowing for independent control of output voltage amplitude and frequency, and employing unipolar power switches connected in parallel to reduce losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fundamental clocking or block clocking is used in the inverter, then the inverter switching frequency can be reduced, but torque ripple increases and power losses increase at low rotational speeds
Solution Approach 1:
The patent segments the frequency conversion function into two independent parts: the DC/DC converter handles amplitude control while the inverter handles frequency control. This segmentation allows the inverter to operate at low switching frequencies using fundamental or block clocking without suffering from torque ripple and power losses, because the amplitude modulation function has been transferred to the DC/DC converter stage.
Solution Approach 2:
The DC/DC converter acts as an intermediary component between the DC link and the inverter. It conditions the DC voltage by adjusting its amplitude according to the desired output voltage level before feeding it to the inverter. This intermediary function enables the inverter to focus solely on frequency conversion with simplified switching strategies.
2Device complexity
If the inverter switching frequency is reduced for fundamental clocking, then device complexity is reduced, but manufacturing precision of output voltage amplitude deteriorates
Solution Approach 1:
The patent divides the control functions by separating amplitude regulation (handled by the DC/DC converter) from frequency regulation (handled by the inverter). This segmentation allows the inverter to use simple fundamental or block clocking schemes with low switching frequencies, while the DC/DC converter independently ensures precise output voltage amplitude control through its controlled rectifier and switching mechanisms.
3Adaptability or versatility
If conventional frequency converters are used, then adjustable output voltage and frequency can be achieved, but efficiency is reduced due to high power losses
Solution Approach 1:
The patent segments the power conversion process into two efficient stages: a controlled rectifier/DC/DC converter stage for precise DC voltage regulation, and an inverter stage for frequency conversion. This segmentation allows each stage to operate in its optimal efficiency range, with the DC/DC converter handling amplitude control at low losses and the inverter handling frequency control with simplified switching, thereby reducing overall power losses while maintaining full adaptability.
Solution Approach 2:
The patent changes the operating parameters by using low inverter switching frequencies (fundamental or block clocking) combined with precise DC voltage control. This parameter change from high-frequency PWM switching to low-frequency switching with upstream voltage control reduces switching losses in the inverter while maintaining the ability to provide adjustable output voltage and frequency.
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 enables efficient generation of adjustable frequency converter output voltages with reduced torque ripple and power losses, enabling cost-effective structural and cooling concepts for high-power applications without massive heat sinks.
Implementation Method 1
a clocked DC/DC converter which is designed to generate from an input direct voltage comprising an input voltage level a DC/DC converter output voltage having a prescribable DC/DC converter output voltage level
Implementation Method 2
a clocked inverter comprising a number of controllable switches, to which inverter the DC/DC converter output voltage is applied and which is designed to actuate the switches with an inverter switching frequency
Data Source
AI summary
A frequency converter is used for generating at least one frequency converter output voltage a prescribable frequency converter output voltage amplitude and a prescribable frequency converter output voltage frequency for an electric motor. The frequency converter has: a clocked DC/DC converter is designed to generate from an input direct voltage having an input voltage level a DC/DC converter output voltage having a DC/DC converter output voltage level, wherein the DC/DC converter is designed to generate the DC/DC converter output voltage level based on the prescribable frequency converter output voltage amplitude, and a clocked inverter having a number of controllable switches, to which inverter the DC/DC converter output voltage is applied and which actuates the switches with an inverter switching frequency such that the at least one frequency converter output voltage with the prescribable frequency converter output voltage frequency is generated from the DC/DC converter output voltage.