EV Charging DC/DC Converter With Neutral-Point Common-Mode Suppression
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Solution Overview
Problem
Existing electric vehicle charging systems face challenges in achieving high electrical performance quickly while minimizing common-mode interferences, often requiring complex charging circuits and transformers.
Innovation Solution
The solution involves connecting the center point of the intermediate circuit to the neutral conductor of the multiphase power grid, allowing for a 'common-mode free' operation of rectifiers and DC/DC converters. This simplifies the DC/DC converter circuit and reduces the blocking voltage requirements for semiconductor switching elements, enabling the use of GaN-based buck converters and reducing the size and complexity of the filter circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a transformer is used in the DC/DC converter for galvanic isolation, then common-mode interferences are reduced, but the device complexity and structural size increase
Solution Approach 1:
The patent removes the transformer from the DC/DC converter circuit, extracting the galvanic isolation function and replacing it with a direct connection between the intermediate circuit center point and the neutral conductor. This eliminates the harmful effect of common-mode interferences while avoiding the complexity and size of transformer-based isolation.
Solution Approach 2:
The neutral conductor acts as an intermediary element, providing a reference potential connection between the power grid and the intermediate circuit. This mediator enables common-mode interference reduction without requiring a transformer, thereby simplifying the charging circuit while maintaining isolation performance.
2Reliability
If a transformer is used in the DC/DC converter, then galvanic isolation is achieved, but the structural size and weight of the charger increase
Solution Approach 1:
The transformer is extracted from the charging system, replacing the heavy magnetic isolation component with an electrical connection to the neutral conductor. This maintains galvanic isolation functionality while dramatically reducing the charger's weight and structural size.
Solution Approach 2:
The mechanical/magnetic isolation system (transformer) is replaced with an electrical system utilizing the neutral conductor connection. This substitution eliminates bulky magnetic components while achieving the same isolation objective, thereby reducing weight and size.
3Strength
If the blocking voltage of semiconductor switching elements is increased to 1000 V or 1200 V, then higher voltage tolerance is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent changes the voltage parameter requirement for switching elements from high voltage (1000-1200 V) to lower voltage (600 V) by establishing a stable reference potential through the neutral conductor connection. This parameter change enables the use of simpler, less expensive switching elements while maintaining adequate voltage tolerance.
4Object-affected harmful factors
If the filter circuit on the grid side is enlarged to handle transformerless operation, then common-mode interference reduction is achieved, but the structural size increases
Solution Approach 1:
The need for an enlarged filter circuit is eliminated by extracting the common-mode interference source (transformer) from the system. The neutral conductor connection provides inherent common-mode rejection, allowing the use of a compact filter circuit rather than a bulky one.
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 approach enables a high charging current with reduced common-mode interferences, resulting in a more efficient and compact charging system. It also allows for single-phase charging at household power outlets and reduces the structural size and weight of the charger.
Implementation Method 1
an alternating current or rotary current provided by a multiphase power grid is rectified
Implementation Method 2
an intermediate circuit which is arranged on the charging side of the rectifier and is coupled to the latter and has a number of capacitances and a center point
Data Source
AI summary
An apparatus for charging a (fully) electric battery vehicle with a direct current, having a rectifier connected to a multiphase power supply system, having an intermediate circuit which is arranged on the charging side of the rectifier and is coupled to the latter and has a number of capacitances and a centre point, having a DC/DC converter which is arranged on the charging side of the intermediate circuit and is coupled to the latter and is intended to adapt an intermediate circuit voltage of the intermediate circuit to a charging voltage of a battery of the battery vehicle, wherein the centre point of the intermediate circuit is connected to a neutral conductor of the multiphase power supply system.