Isolated CLLC DC-DC Converter for Partial Discharge Control
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Solution Overview
Problem
Existing high voltage DC bus systems face challenges in integrating low voltage systems and components, and providing sufficient protection against corona effects and partial discharge hazards.
Innovation Solution
A bidirectional isolated high voltage DC-DC converter is developed, featuring a primary three-level circuit, a CLLC resonant tank network with an isolation transformer, and a secondary three-level circuit, along with active capacitor middle point voltage control. This design allows for efficient conversion between high and low voltage DC levels while managing partial discharge hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage DC bus is used to handle electric power needs, then power distribution capability is improved, but integration of low voltage systems and protection against corona effects becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the voltage conversion function into two separate DC-DC converter stages: a first converter reducing high voltage to intermediate voltage, and a second converter reducing intermediate voltage to low voltage. This multi-stage approach allows the high voltage DC bus to be integrated with low voltage systems through progressive voltage reduction, solving the adaptability problem while maintaining high power distribution capability.
2Ease of operation
If conventional designs use IGBTs to emulate mechanical contact with pre-charging, then inrush current control is improved, but disconnect capability upon motor drive inverter bridge failure becomes weak
Solution Approach 1:
The patent introduces an intermediary protective device (contactor or circuit breaker) controlled by the controller that can disconnect the motor drive inverter bridge from the DC bus upon failure. This intermediary component provides reliable disconnection capability while the controller manages both pre-charging for inrush current control and failure disconnection, resolving the contradiction between ease of operation and reliability.
3Ease of operation
If low voltage DC buses are used with internal DC bus rails from chassis, then ease of operation is improved, but partial discharge hazard situation deteriorates
Solution Approach 1:
The patent replaces the conventional low voltage DC bus architecture with a high voltage DC bus system that uses electronic voltage conversion (through DC-DC converters) instead of direct mechanical/chassis-based voltage distribution. This substitution eliminates the partial discharge hazards associated with low voltage chassis-based systems while maintaining ease of operation through controlled electronic voltage reduction to intermediate and low voltage levels for various systems.
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
The bidirectional converter optimizes partial discharge hazard management and enables the interfacing of standard power systems with high voltage DC buses, improving system efficiency and power density.
Implementation Method 1
a capacitor-inductor-inductor-capacitor (CLLC) resonant tank network connected to the primary three-level circuit
Implementation Method 2
The CLLC resonant tank network includes an isolation transformer that separates the primary side from the secondary side of the bidirectional high voltage DC-DC converter
Data Source
AI summary
A bidirectional isolated high voltage DC-DC converter includes a primary three-level circuit, a capacitor-inductor-inductor-capacitor (CLLC) resonant tank network connected to the primary three-level circuit, a secondary three-level circuit connected to the CLLC resonant tank network, and a controller that controls one or more of the components of the bidirectional isolated high voltage DC-DC converter. The primary three-level circuit and the secondary three-level circuit include capacitor middle points having respective voltages that are actively controlled by the controller. The controller implements a novel space vector PWM (SVPWM). The secondary capacitor middle point is chassis grounded to provide an optimal system level partial discharge hazard management for aircraft. vehicle and vessel applications. GaN power MOSFETs are used for high frequency operation of the power switches.