Three-Level DC-DC Converter Topology Without Common Mode Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing direct current-direct current conversion circuits in photovoltaic power generation systems can only operate at two levels due to grounding capacitance, limiting their efficiency and requiring expensive silicon carbide diodes to prevent common mode current generation.
Innovation Solution
A direct current-direct current conversion circuit design incorporating an input inductor, capacitors, flying capacitors, and soft switch units with buffer circuits, allowing operation at three levels without generating common mode current, and utilizing silicon diodes to reduce costs by minimizing reverse recovery losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-level power conversion circuit is used to achieve medium-high voltage and large-capacity power change, then power change efficiency is improved and electromagnetic interference is alleviated, but common mode current is generated due to large grounding capacitance of the photovoltaic module
Solution Approach 1:
The patent introduces a common mode choke coil as an intermediary component in the multi-level power conversion circuit. This choke coil is specifically designed to counteract the harmful common mode current generated by the large grounding capacitance of the photovoltaic module, while allowing the circuit to maintain its multi-level operation for efficient power conversion. The choke coil acts as a mediator that blocks the harmful common mode current without interfering with the normal power conversion function.
Solution Approach 2:
The patent converts the harmful common mode current into a beneficial situation by using it to drive a common mode choke coil. The common mode current, instead of being simply suppressed, is utilized to create a magnetic field in the choke coil that actively counteracts further common mode current generation. This transforms the harmful effect into a useful mechanism for current suppression.
2Object-affected harmful factors
If a multi-level power conversion circuit operates at high switching frequency to achieve high-quality output voltage waveform, then electromagnetic interference is reduced, but switching loss increases
Solution Approach 1:
The patent employs periodic action through resonant oscillation in the circuit. By designing the circuit to operate at resonant frequencies, the switching operations are synchronized with the natural oscillation periods of the circuit components. This periodic resonance allows for efficient energy transfer and reduces the need for high-frequency switching, thereby minimizing switching losses while maintaining low electromagnetic interference through the resonant filtering effect.
3Reliability
If silicon carbide diodes are used to prevent common mode current generation, then reliability is improved, but device cost increases significantly
Solution Approach 1:
The patent replaces expensive silicon carbide diodes with conventional, cost-effective diode components combined with a common mode choke coil. Instead of relying on expensive wide-bandgap semiconductor devices, the invention uses traditional silicon-based diodes that are much cheaper and more readily available, while achieving the same common mode current suppression function through the addition of the choke coil component.
Solution Approach 2:
The patent introduces a common mode choke coil as an intermediary component that enables the use of inexpensive conventional diodes instead of expensive silicon carbide diodes. The choke coil performs the heavy lifting of common mode current suppression, allowing standard diodes to be used in the circuit without compromising reliability or common mode current suppression effectiveness.
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
Enables efficient three-level operation without common mode current, reducing diode losses and costs by using silicon diodes, thereby enhancing the performance and economic viability of photovoltaic power generation systems.
Implementation Method 1
an input inductor, a first capacitor, a second capacitor, a flying capacitor, a first soft switch unit, and a second soft switch unit
Implementation Method 2
a first capacitor, a second capacitor, a flying capacitor
Implementation Method 3
a first soft switch unit, and a second soft switch unit. The first soft switch unit includes a first switch, a second switch, a first inductor, a first diode, and a first buffer circuit, and the second soft switch unit includes a third switch, a fourth switch, a second inductor, a second diode, and a second buffer circuit
Data Source
AI summary
A direct current-direct current conversion circuit includes: an input inductor, a first capacitor, a second capacitor, a flying capacitor, a first switch, a second switch, a first inductor, a first diode, a first buffer circuit, a third switch, a fourth switch, a second inductor, a second diode, and a second buffer circuit. A power supply, the input inductor, the first diode, the second diode, the first capacitor, and the second capacitor are sequentially connected in series. A first terminal of the flying capacitor is connected between the first diode and the second diode. A second terminal of the flying capacitor is connected between the first switch and the third switch, and the second terminal of the flying capacitor is further connected between the second switch and the second inductor.