MPPT Algorithm for Photovoltaic Systems Under Rapid Irradiation Changes
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Solution Overview
Problem
Conventional maximum power point tracking (MPPT) methods, such as the perturb&observe (P&O) method, struggle to accurately maintain the maximum power point under rapidly changing irradiation conditions due to the inability to separate the origin of power changes, leading to suboptimal power extraction.
Innovation Solution
The method involves storing historic data of power and voltage/current values to calculate a compensation term that accounts for irradiation changes, allowing for more accurate determination of the next voltage change and enhancing power extraction by compensating for irradiation-induced power fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If P&O method is used to track maximum power point, then the operation point can be driven to the best possible operation point under stable conditions, but under rapidly changing irradiation conditions the algorithm cannot find the maximum power point due to inability to separate power change origin
Solution Approach 1:
The patent segments the power change observation into two distinct components: power change due to reference voltage variation and power change due to irradiation variation. By storing historical power values at different reference voltages and calculating separate change rates, the algorithm can isolate and compensate for irradiation effects, thereby resolving the contradiction between measurement precision and adaptability to changing conditions.
Solution Approach 2:
The patent performs preliminary measurements by storing power values at multiple reference voltage points before making optimization decisions. This preliminary action of collecting and storing historical data allows the algorithm to calculate irradiation compensation terms in advance, enabling accurate MPP tracking even when irradiation conditions change rapidly during operation.
2Productivity
If reference voltage is constantly changed in P&O method, then power extraction can be optimized, but under changing irradiation the observed power change results from both reference change and irradiation change making the method unable to determine correct direction
Solution Approach 1:
The patent introduces an intermediary compensation term that accounts for irradiation-induced power changes. This intermediary element allows the algorithm to separate the information about reference-voltage-induced power change from irradiation-induced power change, thereby preserving the ability to determine the correct optimization direction even when both factors are simultaneously acting on the system.
Solution Approach 2:
The patent implements a feedback mechanism where historical power measurements are continuously stored and used to calculate compensation terms. This feedback loop provides information about irradiation trends, allowing the algorithm to adjust its reference voltage changes accordingly and maintain accurate MPP tracking despite changing environmental conditions.
3Measurement precision
If additional measurements are performed to separate power change origins, then accuracy under changing conditions can be improved, but system complexity and measurement requirements increase
Solution Approach 1:
The patent makes the system self-sufficient by utilizing power measurements that are already taken during normal P&O operation. Instead of requiring additional dedicated measurements, the algorithm reuses existing power data at different reference voltage points to calculate irradiation compensation terms, thereby improving accuracy without increasing measurement system complexity.
Solution Approach 2:
The patent makes the existing power measurement system multi-functional: the same measurements used for basic P&O tracking are also used to calculate irradiation compensation terms. This universal use of existing data eliminates the need for additional measurement devices or sensors, resolving the contradiction between measurement precision and device complexity.
Data Source
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AI summary
A method and an arrangement of tracking a maximum power point of a photovoltaic system, in which method an operation point of the photovoltaic system is changed based on the change of operation point and a change of power generated by the photovoltaic system, the method comprising repeatedly determining a current or voltage of the photovoltaic system, determining a power of the photovoltaic system, determining a change of power of the photovoltaic system with respect to a previous determined power, changing the operation point of the photovoltaic system by changing a current or voltage reference of the system stepwise depending on the change of power and a direction of a previous change of the current or voltage reference. The method comprises further storing the determined values of current or voltage and the determined power of the photovoltaic system together with a time value, wherein the determination of the change of power (ΔP) of the photovoltaic system comprises reading from the stored values a previous value of determined power and its time value having a current or voltage value equalling a present current or voltage value, calculating the change of power from the current value of power (P(k)), previous value of power (P(k-1)), stored value of power (P(m)) having a current or voltage value corresponding to a present current or voltage, and the time value (m) of the stored value of power (P(m)).