Parallel Inverter DC Bus Control for Circular Current Suppression
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Solution Overview
Problem
Parallel inverter systems face challenges with circular DC current, which reduces efficiency and can cause damage due to non-ideal factors like switching speed and voltage inconsistencies between DC buses.
Innovation Solution
The proposed inverter system includes a pre-conversion circuit, a post-conversion circuit, and a control circuit that detects DC components in the AC output, calculates a deviation value, performs PI adjustment, and adjusts the DC bus voltage to suppress circular DC current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inverter systems are connected in parallel to increase power capacity, then the power capacity and reliability are improved, but circular DC current is generated due to voltage inconsistencies and non-ideal factors
Solution Approach 1:
The patent implements a feedback control mechanism where the controller detects the DC component in the AC output voltage and uses this information to adjust the DC bus voltage. The controller continuously monitors the output and modifies the switching duty cycle of the power devices to eliminate the DC component, thereby suppressing circular DC current while maintaining parallel operation capability
Solution Approach 2:
The patent dynamically adjusts the DC bus voltage as a control parameter to eliminate circular DC current. By changing the DC bus voltage based on detected DC component levels, the system optimizes the operating parameters to prevent harmful current circulation while maintaining high power capacity
2Loss of energy
If the DC bus voltage is adjusted to suppress circular DC current, then the efficiency is improved and damage is prevented, but the control complexity increases
Solution Approach 1:
The control circuit uses feedback from DC component detection to automatically adjust the DC bus voltage through duty cycle modification. This closed-loop approach improves efficiency by eliminating circular DC current while keeping the control mechanism integrated within the existing inverter structure, avoiding excessive complexity
Solution Approach 2:
The inverter system performs self-regulation by detecting its own output DC component and automatically adjusting its internal DC bus voltage accordingly. The system uses its own output characteristics to control itself, reducing the need for external complex control mechanisms
3Adaptability or versatility
If inverter systems with different DC bus voltages are connected in parallel, then the adaptability is improved, but circular DC current cannot be eliminated
Solution Approach 1:
The patent dynamically adjusts the DC bus voltage as a controllable parameter to match conditions for parallel operation. By actively modifying the DC bus voltage based on detected DC components, the system can accommodate inverters with initially different voltage levels while eliminating circular DC current through real-time parameter optimization
Solution Approach 2:
The system transitions from static DC bus voltage to dynamic voltage adjustment. The DC bus voltage is continuously modified in response to operating conditions and detected DC components, enabling the system to adapt to parallel connection scenarios with different initial voltage levels while suppressing harmful circular currents
Data Source
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AI summary
An inverter system, including a pre-conversion circuit, a post-conversion circuit, and a control circuit; the pre-conversion circuit is configured to convert a voltage of a power supply into a DC voltage and output the DC voltage to the post-conversion circuit; a voltage between the pre-conversion circuit and the post-conversion circuit is a DC bus voltage; the post-conversion circuit is configured to output an alternating current; the control circuit is configured to detect a DC component of an output terminal of the post-conversion circuit, calculate a difference value of a zero value and the DC component to obtain a DC component deviation value, and perform PI adjustment on the DC component deviation value to obtain a voltage compensation value; the voltage compensation value is used to adjust the DC bus voltage.