DC Chopper Circuit with Segmented Switches for Energy Dissipation
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Solution Overview
Problem
In DC power transmission systems, the accumulation of excess energy during faults leads to uncontrolled charging of transmission lines, causing voltage stress and potential damage, as generators continue to feed energy into lines, and existing chopper circuits suffer from high electromagnetic noise and complex control requirements.
Innovation Solution
A control circuit with parallel current transmission paths and converters, including power dissipation elements, allows selective energy storage device removal to manage energy flow, enabling efficient energy removal and regulation through simultaneous charging and discharging of converters, thus preventing voltage transients and maintaining an uninterrupted load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple semiconductor switch is used to connect a resistor between DC transmission lines for energy absorption, then the device complexity is reduced, but high electromagnetic noise and interference are generated due to PWM action and rapid voltage/current changes
Solution Approach 1:
The chopper circuit is segmented into multiple series-connected semiconductor switches instead of using a single switch. This segmentation allows for lower voltage stress on each individual switch and enables more gradual commutation, reducing electromagnetic noise and interference while maintaining the energy absorption function.
Solution Approach 2:
The circuit employs periodic action through controlled switching sequences where switches are turned on and off in a coordinated manner. This periodic switching allows for smooth energy transfer and dissipation, reducing transient spikes and electromagnetic interference compared to abrupt single-switch operation.
2Measurement precision
If a large number of lower voltage semiconductor switches are used in series with PWM control for accurate energy absorption, then the energy control precision is improved, but the device complexity and passive component size increase
Solution Approach 1:
The use of multiple series-connected switches segments the total voltage requirement across individual components. Each switch handles a portion of the total voltage, allowing for simpler individual switch designs while collectively achieving the required voltage rating and control precision through coordinated operation.
Solution Approach 2:
Multiple semiconductor switches are merged in series configuration to collectively handle the full DC link voltage. This merging approach distributes the voltage stress and enables precise energy control through combined switching action, reducing the complexity burden on any single component while maintaining overall system precision.
3Reliability
If energy storage devices are used to temporarily store excess power in the transmitting electrical network, then the energy buffering capability is improved, but the amount of real power that can be stored is limited by the finite energy storage capability
Solution Approach 1:
The invention extracts the energy dissipation function from the energy storage system by providing a dedicated chopper circuit pathway. This allows excess energy to be actively removed and dissipated separately from the stored energy in capacitors, effectively increasing the total energy handling capacity beyond what storage alone could provide.
Solution Approach 2:
The chopper circuit acts as an intermediary mechanism between the energy storage capacitors and the DC transmission lines. It provides a controlled pathway for excess energy to be dissipated, complementing the energy storage function and enabling the system to handle larger energy fluctuations than storage alone could manage.
4Productivity
If a load dump chopper circuit is used to divert excess power away from DC transmission lines, then the excess energy removal capability is improved, but complex control methods and large passive devices are required to ensure equal voltage sharing among semiconductor switches
Solution Approach 1:
The chopper circuit uses multiple series-connected switches that segment the voltage handling requirements. This segmentation naturally facilitates more uniform voltage distribution across switches and reduces the complexity of control methods needed to achieve equal voltage sharing, as each switch operates at a lower, more manageable voltage level.
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 effectively regulates energy levels in DC power transmission systems, preventing damage and electromagnetic interference, while ensuring smooth power dissipation and minimizing disturbances during fault conditions.
Implementation Method 1
each module including at least one energy storage device
Implementation Method 2
dissipate power via the first and second power dissipation elements
Data Source
Figure 1a~1b
Figure 2
Figure 3~4
AI summary
A control circuit (30) comprises: first and second terminals (32,34) for connection to an electrical network (36,38); a current transmission path extending between the first and second terminals (32,34), the current transmission path including first and second current transmission path portions (40,42), the first and second current transmission path portions (40,42) being arranged to permit a current flowing, in use, between the first and second terminals)(32,34) and through the first current transmission path portion (40) to bypass the second current transmission path portion (42) and to permit a current flowing, in use, between the first and second terminals (32,34) and through the second current transmission path portion (42) to bypass the first current transmission path portion (40), each current transmission path portion (40,42) including a respective converter (50a,50b), each converter (50a,50b) including at least one module, each module including at least one energy storage device, the current transmission path further including at least one energy conversion element (44,46,48); and a controller (100) configured to selectively remove the or each energy storage device from the respective current transmission path portion (40,42) to cause current to flow from the electrical network (36,38) through the current transmission path and the or each energy conversion element (44,46,48) to remove energy from the electrical network (36,38), wherein the controller (100) is configured to selectively remove the or each energy storage device from the respective current transmission path portion (40,42) to control first and second currents respectively flowing, in use, in the first and second current transmission path portions (40,42) to simultaneously charge the converter (50a,50b) of one of the first and second current transmission path portions (40,42) and discharge the converter (50b) of the other of the first and second current transmission path portions (40,42).