NPC Rectifier and Buck Converter Layout for Modular EV Fast Charging
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Solution Overview
Problem
Existing charging systems for plug-in hybrid and electric vehicles are limited by low efficiency and power density due to the integration of DC chargers within the vehicles, which restricts fast charging capabilities and modularity.
Innovation Solution
The implementation of a DC charging circuit and station that utilizes a neutral-point clamped (NPC) rectifier and DC/DC buck converters, along with multi-winding step-down transformers and energy management strategies, to efficiently convert AC power to DC power for electric vehicles, enabling modular assembly and energy sourcing from various storage solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If DC chargers are integrated into plug-in hybrid and electric vehicles, then the charging system is compact and portable, but the charging efficiency and power density are limited
Solution Approach 1:
The patent extracts the DC charging function from the vehicle and places it in an external charging station. The charging station contains the DC charger, NPC rectifier, and DC/DC buck converter, while the vehicle only needs an onboard DC connector. This extraction resolves the contradiction by enabling high-efficiency DC fast charging externally while keeping the vehicle design simple.
Solution Approach 2:
The patent transitions from vehicle-integrated charging (one-dimensional solution) to a station-based charging system (adding spatial dimension). The charging infrastructure is deployed at locations like gas stations, transforming the charging paradigm from mobile to fixed, thereby achieving high power density without compromising vehicle design.
2Productivity
If high current is delivered in a short period for fast charging, then charging speed increases, but the charging system requires high power density which integrated vehicle chargers cannot provide
Solution Approach 1:
The patent segments the charging system into multiple independent modules: NPC rectifier module, DC/DC buck converter module, and control module. Each module can be independently sized and optimized for high power density. The modular architecture allows the system to deliver high current for fast charging without requiring the entire vehicle to accommodate high-power components.
Solution Approach 2:
The patent introduces a DC distribution bus as an intermediary between the power source and the vehicle. The DC distribution bus can handle high current and power density, acting as a buffer that decouples the high-power charging infrastructure from the vehicle's electrical system. This intermediary enables fast charging without requiring the vehicle to have high power density capabilities.
3Adaptability or versatility
If modular DC charging stations are implemented, then scalability and adaptability improve, but system complexity increases
Solution Approach 1:
The patent divides the DC charging station into standardized modular units that can be independently manufactured, tested, and deployed. Each module has defined interfaces and functions, making the overall system scalable. Additional modules can be added to increase charging capacity without redesigning the entire system, thereby achieving adaptability while managing complexity through standardization.
Solution Approach 2:
The patent designs the modular DC charging station with universal interfaces and standardized protocols that can serve multiple vehicle types and charging requirements. The same modular architecture can be configured for different power levels and charging speeds, providing versatility without requiring separate complex systems for each application.
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
This solution enhances the efficiency and power density of DC fast charging, reduces grid current demand during peak times, and allows for modular and scalable charging solutions that meet the diverse voltage and power needs of electric vehicles, eliminating the need for integrated DC chargers in vehicles.
Implementation Method 1
The NPC rectifier is coupled to the multi-winding step-down transformer and is configured to convert the first three-phase AC voltage to a first DC voltage at a rectifier output stage
Implementation Method 2
The DC/DC buck converter is configured to convert the first DC voltage to a second DC voltage to be supplied to the electric vehicle
Implementation Method 3
The DC/DC buck converter includes a first DC stage coupled to the rectifier output stage, and a second DC stage configured to be coupled to the electric vehicle
Implementation Method 4
The multi-winding step-down transformer is configured to be coupled to a three-phase AC power source. The multi-winding step-down transformer is configured to generate a first three-phase AC voltage
Data Source
AI summary
A DC charging circuit for an electric vehicle includes a neutral-point clamped (NPC) rectifier and a DC/DC buck converter. The NPC rectifier is configured to convert three-phase AC power to a first DC voltage at a rectifier output stage. The DC/DC buck converter includes a first DC stage coupled to the rectifier output stage, and a second DC stage configured to be coupled to the electric vehicle. The DC/DC buck converter is configured to convert the first DC voltage to a second DC voltage to be supplied to the electric vehicle.