Input Voltage Regulator for Current Source Inverter Stability
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Solution Overview
Problem
In large-scale distributed generator installations, such as utility-scale solar power systems, grid voltage drops can lead to unstable conditions in current source inverters (CSI) due to output voltages being lower than input voltages, making it difficult to control current generation.
Innovation Solution
A method and apparatus for regulating the input voltage to a power conversion module by computing a voltage regulation threshold based on the output voltage, comparing the input voltage to this threshold, and generating an average input voltage that is less than the threshold using a controller and an input voltage regulator, which includes a capacitor, switch, and diode, to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the CSI increases voltage towards the grid, then the need for additional DC-DC boost stage is eliminated, but the input voltage must be lower than output voltage which causes unstable condition when grid voltage drops
Solution Approach 1:
The patent applies preliminary action by proactively regulating the input voltage to remain below the output voltage threshold before unstable conditions can develop. The controller continuously monitors and adjusts the input voltage from photovoltaic modules to prevent the condition where input voltage exceeds output voltage, thereby avoiding instability before it occurs.
Solution Approach 2:
The patent implements feedback control by continuously comparing the input voltage and output voltage levels and using this information to adjust the operating point of the photovoltaic modules. The controller uses voltage measurements to provide feedback that maintains the input voltage below the output voltage, ensuring stable operation of the CSI inverter.
2Power
If grid voltage drops, then additional power must be injected from DG to maintain grid operation, but output voltage at CSI becomes lower than input voltage causing unstable condition
Solution Approach 1:
The patent applies preliminary action by pre-regulating the input voltage to stay below the output voltage level before grid voltage drops cause instability. The controller anticipates potential instability by maintaining voltage margins, allowing the system to continue injecting power into the grid while preventing the dangerous condition where input voltage exceeds output voltage.
Solution Approach 2:
The patent implements dynamics by making the voltage regulation adaptive to changing grid conditions. The controller dynamically adjusts the input voltage regulation based on real-time measurements of output voltage and grid conditions, enabling the system to maintain stable current control even as grid voltage fluctuates and additional power injection is required.
3Productivity
If input voltage is allowed to exceed output voltage, then maximum power point tracking efficiency increases, but current generation becomes uncontrollable
Solution Approach 1:
The patent implements feedback control to maintain current controllability while operating near maximum power point. The controller continuously monitors voltage levels and provides feedback to adjust the operating point, ensuring that the input voltage remains below the output voltage threshold. This feedback mechanism allows the system to efficiently track the maximum power point without sacrificing current controllability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the operating voltage parameters of the photovoltaic modules to maintain optimal power generation. The controller modifies voltage and current parameters in real-time to keep the system operating at or near the maximum power point while maintaining the critical constraint that input voltage remains below output voltage for stable current control.
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 ensures stable operation of the CSI by maintaining an average input voltage below the regulation threshold, preventing unstable conditions and ensuring continuous current generation even when grid voltage drops, thereby maintaining grid stability and reducing common mode emissions.
Implementation Method 1
The input voltage regulator may include a capacitor, a switch, and a diode
Implementation Method 2
The input voltage regulator may include a capacitor, a switch, and a diode
Data Source
AI summary
A method and apparatus for regulating an input voltage to a power conversion module. In one embodiment, the method comprises computing a voltage regulation threshold based on an output voltage for the power conversion module; comparing an input voltage of the power conversion module to the voltage regulation threshold; and generating, when the input voltage satisfies the voltage regulation threshold, an average input voltage less than the voltage regulation threshold, wherein the average input voltage is generated from the input voltage.