Modular DC Chopper Circuit for Voltage Stress Management
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Solution Overview
Problem
In DC power transmission schemes, existing chopper circuits face issues with high voltage stress and electromagnetic noise due to uncontrolled energy accumulation in DC transmission lines during faults, leading to potential damage and imbalance in power transmission.
Innovation Solution
A control circuit with primary and secondary terminals, including modules with energy storage devices that can be selectively removed from the current transmission path, and an auxiliary energy conversion element to manage voltage and current levels, allowing for efficient regulation and dissipation of excess energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple semiconductor switch is used to connect a resistor between DC transmission lines to absorb excess energy, then the device complexity is reduced, but high voltage stress and electromagnetic noise occur due to uncontrolled energy accumulation
Solution Approach 1:
The chopper circuit is divided into multiple independent modules, each with its own semiconductor switch and energy storage device. This segmentation allows distributed control of voltage and current, reducing the voltage stress on individual switches and minimizing electromagnetic noise through localized energy management.
Solution Approach 2:
The circuit transitions from static resistor connection to dynamic modular control, where modules are selectively activated based on real-time energy accumulation conditions. This dynamic approach enables precise control over energy absorption rates, preventing voltage spikes and electromagnetic interference while maintaining system simplicity.
2Measurement precision
If PWM switching is used to control energy absorption in chopper circuits, then energy control precision is improved, but high rates of change of voltage and current cause electrical spikes and electromagnetic noise
Solution Approach 1:
Instead of continuous PWM switching, the circuit uses periodic activation of modular units. Each module is switched on for a controlled duration to absorb a specific energy quantity, then switched off. This periodic action maintains precise energy control while avoiding the high-frequency voltage and current transitions that generate electromagnetic noise.
Solution Approach 2:
The circuit employs multiple low-voltage semiconductor switches in modular units that are sequentially activated rather than continuously switched. Each switch operates for a limited duration to perform its energy absorption function, reducing voltage stress and electromagnetic interference compared to continuous PWM operation of a single switch.
3Reliability
If DC transmission lines continue to transmit power during a fault, then the receiving electrical network can ride through the supply dip, but excess power accumulates causing voltage stress and potential component damage
Solution Approach 1:
Modular chopper units are introduced as intermediary components between the DC transmission lines and the load. These units act as buffer elements that can selectively absorb excess energy during faults, protecting downstream components from voltage stress while allowing the transmission lines to continue operating and maintaining network ride-through capability.
Solution Approach 2:
The circuit dynamically changes the resistance parameter by selectively activating different modular units based on the level of excess energy. As energy accumulates, additional modules are engaged to increase total absorption capacity, thereby adapting the system's voltage handling capability to match real-time conditions and prevent component damage.
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 control circuit effectively regulates energy levels, protects components from overvoltage and overcurrent, and minimizes the size and cost by maintaining compatible voltage and current ratings during normal and fault operations, while enabling safe discharge of excess energy.
Implementation Method 1
each module including at least one energy storage device
Implementation Method 2
an auxiliary energy conversion element and an auxiliary terminal, the or each auxiliary energy conversion element being connected in series between the secondary and auxiliary terminals
Data Source
AI summary
The control circuit includes first and second primary terminals for connection to a DC network, a secondary terminal connected in series between the first and second primary terminals and at least one auxiliary energy conversion element and an auxiliary terminal. The first and second primary terminals have a plurality of modules and a plurality of primary energy conversion elements connected in series therebetween to define a current transmission path, each module including at least one energy storage device, each energy storage device being selectively removable from the current transmission path. The plurality of modules include a first module and a second module the first module being connected in series with at least one primary energy conversion element between the first primary terminal and the secondary terminal to define a first current transmission path portion, and the second module being connected in series with at least one other primary energy conversion element between the second primary terminal and the secondary terminal to define a second current transmission path portion. The auxiliary energy conversion element is connected in series between the secondary and auxiliary terminals, the auxiliary terminal being for connection to ground.