Bidirectional Rectifiers for Mixed AC-DC Power Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrical energy distribution systems in ships and other applications face challenges in efficiently managing variable and fixed-frequency loads, optimizing generator operation, and limiting fault currents, particularly in systems with multiple generators and common DC buses.
Innovation Solution
A bidirectional electrical power distribution system incorporating fixed-frequency and variable-frequency AC generators, DC distribution networks, bidirectional rectifiers, and semiconductor-based protection means to manage power transfer and fault currents, with features like thyristor bridges and disconnecting stages for fault current interruption and energy dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple generators supply the primary distribution network in parallel with selective activation, then power redundancy and reliability are improved, but generator operation efficiency deteriorates because they operate at fixed nominal speed rather than controlled speed according to electrical load
Solution Approach 1:
The patent implements dynamic speed control of generators through power converters that adjust generator speed according to actual electrical load requirements. This transforms the static fixed-speed operation into dynamic variable-speed operation, allowing generators to operate at optimal efficiency points while maintaining power redundancy through multiple generators that can be selectively activated.
2Loss of energy
If a common DC bus is used to supply various loads and recover energy from generator-mode loads, then energy recovery capability is improved, but fault current management becomes more complex and difficult to control
Solution Approach 1:
The patent segments the distribution network into multiple isolated DC buses rather than using a single common DC bus. Each DC bus is served by dedicated rectifier stages connected to specific generators. This segmentation prevents fault currents from propagating across the entire network while maintaining energy recovery capability within each segmented bus through bidirectional power flow control.
Solution Approach 2:
The patent introduces bidirectional rectifier stages as intermediary devices between generators and DC buses. These rectifiers provide controlled power transfer and isolation, enabling energy recovery from generator-mode loads while acting as protective barriers that limit fault current propagation. The rectifiers serve as mediators that decouple the fault current paths while maintaining functional connectivity for power transfer.
3Adaptability or versatility
If bidirectional rectifier stages are used for power transfer between generators and DC distribution network, then power flexibility and energy recovery are improved, but protection against fault currents requires additional complex protection means
Solution Approach 1:
The patent designs the bidirectional rectifier stages to perform multiple functions simultaneously: power conversion, controlled power transfer, energy recovery, and fault current limitation. By making the rectifiers multi-functional, the patent eliminates the need for separate protection devices, thereby maintaining power flexibility while reducing overall system complexity despite the bidirectional power transfer requirements.
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 system ensures redundant power supply, continuity of service, and effective protection against faults, enabling efficient operation of both fixed-frequency and variable-frequency loads while limiting fault currents without the need for fuse protection.
Implementation Method 1
a first set of rectifier stages (12) connected between the fixed-frequency generators and the distribution network, and a second set of rectifier stages (12) connected between the variable-frequency generators and the DC distribution network
Implementation Method 2
a DC distribution network (II) supplying said variable-frequency loads by means of inverter stages (10)
Implementation Method 3
protection means (19, 20) against fault currents connected between the bidirectional rectifiers and the distribution network... semiconductor devices controlled as a function of a current flowing from the rectifiers or the voltage of the second DC distribution network... controllable means for interrupting a fault current flowing from said generator
Implementation Method 4
at least one portion of the inverter stages comprises a braking chopper having braking resistors capable of dissipating the energy from the loads
Data Source
AI summary
Electrical power distribution system for supplying a set of fixed-frequency loads and a set of variable-frequency loads, includes a set of at least one fixed-frequency AC voltage generator and a set of at least one variable-frequency AC voltage generator, a DC distribution network supplying the variable-frequency loads by means of inverter stages, a first set of rectifier stages connected between the fixed-frequency generators and the distribution network, and a second set of rectifier stages connected between the variable-frequency generators and the DC distribution network. The first set of rectifier stages includes bidirectional rectifiers capable of providing a bidirectional transfer of power and protection means against fault currents connected between the bidirectional rectifiers and the distribution network.