Bipolar DC Voltage Control with Multiple Converters for Load Imbalance
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Solution Overview
Problem
Bipolar DC power systems face challenges in stabilizing two voltage levels due to unbalanced loading conditions, leading to over- and undervoltage issues, and existing control methods are prone to single points of failure and lack scalability.
Innovation Solution
A system with multiple voltage converters is employed to control bipolar DC systems, ensuring redundancy and scalability by coordinating setpoints to maintain positive and negative pole-to-neutral voltages within acceptable limits, avoiding counteraction between converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage balancer or bidirectional converter is used to control pole-to-neutral voltages, then voltage stability is improved, but the system becomes vulnerable to single points of failure
Solution Approach 1:
The patent divides the voltage control function into multiple independent converters (first voltage converter for positive pole, second voltage converter for negative pole) instead of using a single voltage balancer. Each converter independently controls its respective pole-to-neutral voltage, eliminating the single point of failure inherent in centralized voltage balancer architectures.
Solution Approach 2:
Each voltage converter is equipped with its own control means that independently regulates the voltage at its specific pole. The first converter controls positive pole-to-neutral voltage while the second controls negative pole-to-neutral voltage, allowing localized control that improves reliability without requiring coordination that would increase system vulnerability.
2Reliability
If multiple voltage converters are used to control bipolar DC systems, then redundancy and scalability are improved, but converter counteraction may occur
Solution Approach 1:
The control function is segmented such that each voltage converter operates independently with its own control means. The first converter manages positive pole voltage while the second manages negative pole voltage, preventing counteraction by eliminating the need for complex coordination between converters.
Solution Approach 2:
Each voltage converter performs self-service by independently regulating its own pole-to-neutral voltage through dedicated control means. This autonomous operation allows multiple converters to coexist without counteraction, as each converter autonomously maintains its designated voltage level without requiring communication or coordination with other converters.
3Reliability
If stacked AC-DC or DC-DC converters are used for voltage control, then voltage regulation capability is improved, but the control system becomes more complex
Solution Approach 1:
The patent uses stacked converters (AC-DC or DC-DC) for each pole but segments the control function so that each stack has its own independent control means. This segmentation maintains voltage regulation capability while reducing overall control system complexity by eliminating the need for centralized coordination of multiple stacked converters.
Solution Approach 2:
Each stacked converter configuration is given local control autonomy through dedicated control means that regulates only its specific pole-to-neutral voltage. This localized control approach maintains the voltage regulation benefits of stacked converters while avoiding the complexity of coordinating multiple stacked converters through a centralized control system.
Data Source
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Figure 2c~2d
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AI summary
A system (100) for controlling a bipolar DC power system (101) is disclosed. The bipolar DC power system (101) comprises a positive conductor (102), a neutral conductor (103) and negative conductor (104), wherein a positive pole-to-neutral voltage is a voltage between the positive conductor (102) and the neutral conductor (103) and a negative pole-to-neutral voltage is a voltage between the negative conductor (104) and the neutral conductor (103). The system (100) comprises control means for controlling the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, the control means comprising a first voltage converter (105) configured to control a sum or difference of the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, respectively as a function of the sum or difference of the positive output current and negative output current, and a second voltage converter (106). If the first voltage converter (105) is configured to control the sum of the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, then the second voltage controller (106) is configured to control the positive pole-to-neutral voltage, the negative pole-to-neutral voltage, or the difference of the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, respectively as a function of the positive output current, the negative output current or the difference of the positive output current and the negative output current. If the first voltage converter (105) is configured to control the difference of the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, then the second voltage controller (106) is configured to control the positive pole-to-neutral voltage, the negative pole-to-neutral voltage, or the sum of the positive pole-to-neutral voltage and the negative pole-to-neutral voltage, respectively as a function of the positive output current, the negative output current or the sum of the positive output current and the negative output current.