AC Cascade PV System Master Slave Control for Over-Modulation
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Solution Overview
Problem
AC cascade photovoltaic power generation systems often operate in over-modulation conditions, leading to instability and unreliable operation due to differences among photovoltaic cell panels and mismatched control inputs and feedback variables.
Innovation Solution
A method and apparatus using a master and slave controller system to acquire total output power, determine if it exceeds a preset value, and generate control signals to prevent over-modulation by controlling individual cascade units to perform maximum power point tracking (MPPT) or anti-over-modulation strategies, ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If each cascade unit operates independently to track maximum power point, then power generation efficiency is improved, but system stability deteriorates due to over-modulation conditions
Solution Approach 1:
The master controller collects real-time output power data from all cascade units and uses this feedback to dynamically adjust control signals. The system continuously monitors total output power and compares it against reference values, then generates appropriate control signals (first or second control signals) to maintain stable operation while maximizing power generation.
Solution Approach 2:
The control system dynamically switches between different operating modes based on real-time conditions. When total output power exceeds the reference value, the system transitions to power limitation mode; otherwise, it operates in maximum power tracking mode. This dynamic adaptation allows the system to optimize performance while preventing over-modulation instability.
2Productivity
If total output power is increased to maximize energy generation, then productivity is improved, but system reliability worsens due to over-modulation conditions
Solution Approach 1:
The master controller proactively prevents over-modulation by monitoring total output power before instability occurs. When the sum of output powers approaches the reference value, the system preemptively generates control signals to limit further power increase, thereby preventing the harmful over-modulation condition from developing.
Solution Approach 2:
The system changes control parameters dynamically based on operating conditions. The control signal type (first or second) is changed based on whether total output power exceeds the reference value, thereby adjusting the operating parameters of cascade units to maintain stability while maximizing power generation.
3Device complexity
If cascade units operate without centralized coordination, then device complexity is reduced, but system reliability deteriorates due to mismatched control inputs and feedback variables
Solution Approach 1:
The control system is segmented into a master controller that handles centralized coordination and slave controllers that execute local control tasks. This segmentation allows distributed operation at the unit level while maintaining centralized oversight for system-wide stability, resolving the conflict between simplicity and reliability.
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 solution effectively prevents cascade units from operating in over-modulation conditions, ensuring normal, reliable, and stable operation of the AC cascade photovoltaic power generation system by dynamically adjusting power output based on total system power levels.
Implementation Method 1
The DC source is a photovoltaic (PV) cell panel
Data Source
AI summary
A method for controlling an alternating current cascade photovoltaic power generation system is provided, which includes: acquiring, by a master controller, a current total output power of the system; determining, by the master controller, whether the total power value is greater than a preset power value; generating, by the master controller, a first control signal if the total power value is greater than the preset power value; generating, by the master controller, a second control signal if the total power value is smaller than or equal to the preset power value; receiving, by the slave controller, the first or second control signal generated by the master controller; and controlling, by the slave controller based on the first control signal, a cascade unit to independently perform an MPPT operation, or controlling, by the slave controller based on the second control signal, the cascade unit to output power.