Photovoltaic Inverter Control for Power Oscillation and Global MPPT
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Solution Overview
Problem
Conventional photovoltaic inverters fail to track the maximum power point of a photovoltaic array in real time due to rapid changes in external environmental factors, leading to power oscillations that affect grid-connected power quality.
Innovation Solution
A photovoltaic inverter with a controller that regulates the direct-current voltage to a difference from the open-circuit voltage of the photovoltaic array and performs a global maximum power point tracking (MPPT) search to suppress power oscillations, using a detection module to proactively identify and address these oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional maximum power point tracking (MPPT) strategy is used, then the photovoltaic inverter can track maximum power points under different environmental conditions, but it fails to operate at the maximum power point in real time when environmental factors change rapidly
Solution Approach 1:
The controller performs a global MPPT search to proactively identify the true maximum power point before environmental changes fully manifest, then uses this information to guide subsequent tracking operations. This preliminary action ensures the system is prepared for rapid environmental changes and maintains real-time maximum power point operation.
Solution Approach 2:
The system continuously monitors power output and voltage characteristics, using feedback signals to detect deviations from the maximum power point. When power oscillation is detected or environmental changes are sensed, the controller adjusts the operating point by regulating DC voltage, ensuring real-time tracking while maintaining stability through closed-loop control.
2Device complexity
If the photovoltaic inverter operates without global MPPT search, then the control system is simpler, but power oscillation occurs when direct-current voltage enters an unstable interval of the characteristic curve
Solution Approach 1:
The controller implements feedback control by continuously monitoring the DC voltage and power output, comparing actual operating conditions against the characteristic curve of the photovoltaic array. When the DC voltage approaches or enters the unstable interval, the feedback mechanism triggers global MPPT search or adjusts operating parameters to move the operating point to a stable region, thereby eliminating power oscillation while maintaining relatively simple control architecture.
3Measurement precision
If global maximum power point tracking search is performed continuously, then the maximum power point is accurately tracked, but power generation loss increases due to frequent adjustments and shutdowns
Solution Approach 1:
Instead of performing continuous global MPPT search, the system applies partial action by conducting global search only when necessary - specifically when power oscillation is detected or when environmental changes are anticipated. Between these events, the system uses lighter local tracking methods, thereby maintaining accurate maximum power point tracking while significantly reducing power generation loss from frequent adjustments.
Data Source
AI summary
A photovoltaic inverter and a method for controlling the photovoltaic inverter are provided. The photovoltaic inverter includes a main circuit and a controller. A direct-current side of the main circuit is configured to connect a photovoltaic array, and an alternating-current side of the main circuit is configured to connect a power grid and/or a load. The controller controls the main circuit to operate; and in response to an occurrence of a power oscillation in the main circuit, regulates a direct-current voltage of the main circuit to an open-circuit voltage or a voltage close to the open-circuit voltage and then controls the main circuit to perform a global MPPT search based on the regulated voltage.