DC/DC Converter Ripple Suppression via Duty Ratio Control
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Solution Overview
Problem
Existing ripple voltage suppression methods for DC/DC converters in renewable energy systems are costly and complex, with conventional methods requiring additional components like active DC filters or double-loop controllers, which increase costs and complexity while failing to efficiently suppress ripple voltage, thereby affecting power generation efficiency and fuel cell system longevity.
Innovation Solution
A simplified control circuit for the DC/DC converter that uses a voltage detector to generate AC and DC control signals to control the duty ratio of a power electronic switch, eliminating the need for an extra current detector and reducing costs, by detecting only the output voltage of the DC/DC converter to suppress ripple voltage through a PWM signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active DC filter is added to suppress ripple voltage, then the ripple voltage suppression effect is improved, but the system cost and device complexity increase
Solution Approach 1:
The patent extracts and eliminates the unnecessary active DC filter component from the system. By analyzing the ripple voltage generation mechanism, the invention discovers that the ripple can be suppressed through optimized control of existing components (DC/DC converter and DC/AC inverter) without requiring additional filtering hardware, thus removing the harmful complexity while maintaining suppression effectiveness
Solution Approach 2:
The system uses its own existing components to suppress the ripple voltage. The DC/DC converter and DC/AC inverter work together in a coordinated control manner where the inverter's switching actions are specifically designed to counteract the ripple generated by the converter, allowing the system to self-regulate and suppress ripple without external filtering devices
2Reliability
If a double-loop controller with current detector is used to suppress ripple voltage, then the ripple voltage suppression effect is improved, but the control circuit complexity and cost increase
Solution Approach 1:
The patent removes the current detector and simplifies the control structure from a double-loop controller to a single-loop voltage-controlled system. By focusing control effort on the voltage regulation and utilizing the inherent dynamics of the power stages, the invention achieves ripple suppression without requiring current sensing hardware or complex nested control loops
Solution Approach 2:
The patent implements a voltage feedback control mechanism where the output voltage is continuously monitored and used to adjust the duty cycle of the power electronic switches. This feedback loop, combined with specific switching strategies, enables the system to automatically compensate for and suppress ripple voltage while maintaining simple control circuitry
3Reliability
If conventional ripple suppression methods are applied, then the ripple voltage is reduced, but the power generation efficiency decreases due to system losses
Solution Approach 1:
The patent converts the potentially harmful ripple voltage into a beneficial control mechanism. By deliberately introducing controlled switching actions in the DC/AC inverter that are synchronized with and opposite to the ripple frequency from the DC/DC converter, the system transforms the ripple problem into an opportunity for active cancellation, achieving suppression without energy-dissipating filters while actually improving overall efficiency
Data Source
AI summary
A ripple voltage suppression apparatus includes a DC/DC converter and a control circuit. The DC/DC converter has a power electronic switch. The control circuit has a voltage detector detecting a DC output voltage of the DC/DC converter, a ripple voltage suppression circuit receiving the detected DC output voltage to generate an AC control signal for controlling an AC component of a duty ratio of the power electronic switch, an output voltage regulation circuit receiving the detected DC output voltage to generate a DC control signal for controlling an DC component of a duty ratio, an adder adding the AC and DC control signals to form a combined control signal, and a PWM circuit converting the combined control signal into a PWM signal to control the power electronic switch. Only the DC output voltage of the DC/DC converter has to be detected for the control circuit.