Impedance Injection Power Supply for Surge-Tolerant Startup
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Solution Overview
Problem
Modern power transmission and distribution systems face challenges with surge currents due to load switching and faults, which can damage control circuitry in impedance injection units unless mitigated, and there is a need for a power supply that can start up safely from zero line-current.
Innovation Solution
A multi-mode power supply for impedance injection units that includes a charge harvester and a power switching assembly with IGBTs to clamp voltage and generate a supply voltage, capable of withstanding surge currents and starting from zero line-current, using a combination of line-connected and internal current transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impedance injection unit is connected to the power transmission line, then it can perform its function of injecting reactive power, but surge currents from load switching and faults can damage the control circuitry
Solution Approach 1:
A power supply unit is introduced as an intermediary component between the impedance injection unit and the power transmission line. This power supply includes a charge harvester and voltage clamping circuitry that mediates the harmful surge currents, preventing them from reaching and damaging the control circuitry while allowing the impedance injection unit to function normally
Solution Approach 2:
The power supply unit is designed with surge protection capabilities that are activated before surge currents can damage the control circuitry. The charge harvester and voltage clamping mechanisms provide beforehand cushioning by limiting voltage excursions and filtering harmful transients before they affect the sensitive control electronics
2Adaptability or versatility
If the power supply starts up from zero line-current, then it can operate in initial states, but it must safely handle the in-rush current into the DC link capacitor
Solution Approach 1:
The power supply employs dynamic control of the power switching assembly during startup. The system transitions from an initial state of zero line-current to operational state by dynamically managing the charging of the DC link capacitor through controlled switching, preventing dangerous in-rush currents while enabling startup from any initial condition
Solution Approach 2:
The power supply incorporates feedback control mechanisms that monitor the charging state of the DC link capacitor and adjust the power switching assembly accordingly. This feedback ensures safe startup from zero line-current by preventing excessive in-rush current while maintaining the ability to operate from initial states
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 power supply effectively manages surge currents and ensures safe startup from zero line-current, preventing damage to control circuitry and maintaining operation during disturbances, while efficiently powering impedance injection units.
Implementation Method 1
harvests charges by the multi-mode power supply from the phase of the power transmission line to charge a DC link capacitor
Implementation Method 2
The power switching assembly includes a bank of insulated-gate bipolar transistors (IGBTs) that clamps a potential overvoltage to a safe level
Data Source
AI summary
A multi-mode power supply is described for providing power to an impedance injection unit that is operable to inject reactive power into a power transmission line. The impedance injection unit is configured to operate safely in the presence of switching states of the impedance injection unit, and in the presence of disturbances such as surge currents in the power transmission line, by the multi-mode power supply clamping a potential overvoltage to a safe level. The power supply contains analog and digital circuits and can recover automatically from a surge current in the transmission line, or from a condition of zero line current. Power harvesting may be achieved via a line connected current transformer, via an internal current transformer, via a DC link capacitor, or from combinations of these.