Dual DC-Link Inverter Control for Unbalanced Three-Phase Loads
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Solution Overview
Problem
Existing devices for converting between direct current (DC) and alternating current (AC) suffer from significant voltage variations when supplying unbalanced three-phase loads, necessitating large and costly DC link capacitors, which increase installation space and reduce efficiency.
Innovation Solution
A device comprising two DC voltage units connected in parallel to capacitors, with an inverter connected in parallel to the series-connected capacitors, allowing for smaller capacitors and reduced voltage variations, and a control method to adjust power output to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single DC voltage unit with grounded center point is used, then the device can convert DC to AC voltage, but significant voltage variations occur across the DC link capacitors when supplying unbalanced three-phase loads
Solution Approach 1:
The single DC voltage unit is segmented into two separate DC voltage units (first and second), each with its own DC link capacitor. This segmentation allows independent control of each unit's power output, enabling better voltage stability while maintaining the required power conversion capability.
2Stability of the object's composition
If large DC link capacitors are used to limit voltage variation, then voltage stability is improved, but costs and installation space increase
Solution Approach 1:
The total capacitance requirement is segmented into two separate capacitors (first DC link capacitor and second DC link capacitor), each handling a portion of the power conversion. This allows using smaller capacitors compared to a single large capacitor, reducing installation space while maintaining voltage stability.
Solution Approach 2:
By changing the configuration from a single capacitor system to a dual capacitor system with independent DC voltage units, the voltage stability parameter is improved without requiring excessively large capacitor values, thus optimizing the balance between stability and physical size.
3Stability of the object's composition
If large DC link capacitors are used to limit voltage variation, then voltage stability is improved, but device costs increase
Solution Approach 1:
The system is divided into two modular DC voltage units with separate capacitors, allowing the use of smaller, more cost-effective capacitor components rather than requiring a single large, expensive capacitor to achieve the same voltage stability.
4Stability of the object's composition
If the power output of DC voltage units is freely selectable, then voltage variation is reduced, but device complexity increases
Solution Approach 1:
The device is segmented into two independently controllable DC voltage units, each with adjustable power output. This segmentation provides the flexibility to optimize voltage variation by independently controlling each unit's contribution to the total power output.
Solution Approach 2:
The power output of each DC voltage unit is made dynamically adjustable, allowing the system to adaptively control the contribution of each unit to minimize voltage variation under different operating conditions and load scenarios.
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 reduces costs and installation space while ensuring efficient operation by minimizing voltage variations and power losses, making the device cost-effective and compact.
Implementation Method 1
DC link capacitors are used, which limit the voltage variation by temporarily storing energy
Implementation Method 2
The inverter can convert a direct current (DC) voltage into an alternating current (AC) voltage
Data Source
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AI summary
The invention relates to a device (102) for converting between direct current and alternating current comprising an inverter (104), two capacitors (106) and two DC voltage units (108), wherein each DC voltage unit (108) comprises at least one DC voltage converter (110), wherein each of the two DC voltage units (108) is connected in parallel to one of the two capacitors (106) on the inverter side, wherein the capacitors (106) are connected in series, and wherein the inverter (104) is connected in parallel to the capacitors (106) connected in series.