Dual-Sampling MPPT Algorithm for PV Systems Under Dynamic Irradiance
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Solution Overview
Problem
Existing maximum power point tracking (MPPT) algorithms, such as Perturb and Observe (P&O), face limitations like oscillations, slow response, and incorrect tracking under dynamic atmospheric conditions in photovoltaic (PV) systems, leading to reduced power output, especially when coordinating with other energy sources.
Innovation Solution
Implementing a dual-sampling MPPT algorithm that adjusts voltage steps based on power changes and irradiance variations, allowing for more precise tracking of the maximum power point by distinguishing between voltage and irradiance effects, and applying a variable voltage step to drive the PV system towards an external power constraint when maximum power output cannot be provided to the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Perturb and Observe (P&O) algorithm is used for MPPT, then implementation is simple, but oscillations occur around MPP and response speed is slow
Solution Approach 1:
The patent segments the power measurement into two separate sampling instances: first sampling power before voltage perturbation and second sampling power after voltage perturbation. This segmentation allows the system to distinguish between power changes caused by voltage adjustments and those caused by environmental factors, thereby improving response speed while maintaining implementation simplicity.
Solution Approach 2:
The patent implements dynamic voltage step adjustment where the voltage step size is adapted based on operating conditions. The controller dynamically modifies the perturbation magnitude according to the rate of change of irradiance and operating point position, enabling faster response under rapidly changing conditions while avoiding excessive oscillations near the MPP.
2Device complexity
If traditional single-sampling MPPT is used, then computational load is low, but tracking accuracy deteriorates under rapidly changing irradiance conditions
Solution Approach 1:
The patent performs preliminary power sampling before applying voltage perturbation. This first sampling captures the power level under current operating conditions, establishing a baseline that allows the controller to accurately attribute subsequent power changes to either voltage adjustments or environmental variations, thereby improving tracking accuracy without excessive computational burden.
Solution Approach 2:
The patent implements a feedback mechanism where the controller compares power measurements from two sampling instances and uses the power difference to determine both the direction and magnitude of voltage adjustments. This feedback loop continuously refines the operating point tracking under dynamically changing irradiance conditions while maintaining manageable computational requirements.
3Speed
If voltage step is increased to improve response speed, then tracking speed improves, but oscillations around MPP increase
Solution Approach 1:
The patent dynamically adjusts the voltage step size based on the operating conditions and proximity to the MPP. When the system is far from the MPP or under rapidly changing irradiance, larger voltage steps are applied to improve tracking speed. As the system approaches the MPP or under stable conditions, the voltage step size is reduced to minimize oscillations, thereby balancing tracking speed and operating point stability.
Solution Approach 2:
The patent changes the perturbation parameter (voltage step size) based on the state of the system. The controller monitors the power difference between sampling instances and adjusts the voltage step magnitude accordingly, implementing a state-dependent perturbation strategy that optimizes both tracking speed and stability across different operating conditions.
Data Source
AI summary
A method for operating a PV system that is integrated into a power system connected to a power grid includes determining a voltage operating point for the PV system based on a maximum power point tracking (MPPT) algorithm. If an available power output of the PV system can be provided to the power grid, the method includes operating the PV system based on the voltage operating point. If the maximum available power output of the PV system cannot be provided to the power grid, the method includes applying a voltage step to the voltage operating point to drive a power output of the PV system towards an external power constraint.