Sensorless MPPT for PV Micro-Inverters Using Current Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photovoltaic (PV) power conditioning systems face challenges with Hall effect and resistive current sensors, which introduce complexity, cost, and efficiency issues due to limitations in measuring PV panel output current, particularly at light loads and in multi-input systems, where precise current measurement is compromised, affecting maximum power point tracking (MPPT) performance.
Innovation Solution
A current sensorless MPPT system using a current estimator based on nonlinear dynamics of the DC/DC converter, estimating output current from PV panel output voltage and DC-bus voltage, eliminating the need for current sense circuitry and enabling precise current estimation for maximum power point tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall effect current sensors are used to measure PV panel output current, then current measurement capability is provided, but system complexity increases due to required correction algorithms and the reliability decreases due to time varying DC-bias and bandwidth limitations
Solution Approach 1:
The patent extracts and eliminates the Hall effect current sensor from the system. Instead of using physical current sensors, the invention uses a current estimator that calculates the PV panel output current based on measurements of PV voltage and DC-bus voltage, along with control signals. This extraction removes the problematic sensor while maintaining current measurement capability through estimation.
Solution Approach 2:
The patent introduces a current estimator as an intermediary component that mediates between voltage measurements and the control system. The estimator uses PV voltage, DC-bus voltage, and control signals as inputs to generate an estimated current output, serving as a virtual intermediary that replaces the need for direct current sensing.
2Measurement precision
If Hall effect current sensors are used to measure PV panel output current, then current measurement is enabled, but cost significantly increases
Solution Approach 1:
The patent replaces expensive Hall effect current sensors with a software-based current estimator implementation that uses standard microcontroller resources. The estimator algorithm runs on existing processing units without requiring additional expensive hardware components, significantly reducing the bill of materials cost while maintaining functional equivalence.
3Measurement precision
If resistive current sensors are used to measure PV panel output current, then current measurement is provided, but power losses increase and efficiency deteriorates
Solution Approach 1:
The patent extracts and removes the resistive current sensor from the system architecture. The current estimation approach eliminates the need for physical current-sensing resistors that would dissipate power, thereby removing the source of efficiency deterioration while maintaining the ability to obtain current information for control purposes.
4Measurement precision
If resistive current sensors are used to measure PV panel output current, then current measurement is enabled, but measurement accuracy is compromised at light loads
Solution Approach 1:
The patent changes the measurement parameters from direct current sensing to voltage-based estimation. The current estimator uses PV voltage and DC-bus voltage measurements combined with control signals to calculate current, providing accurate estimation across the full operating range including light load conditions where resistive sensors fail due to their small sense resistor values.
5Measurement precision
If current sensors are used in multi-input PV power conditioning systems, then current measurement for each panel is provided, but system complexity and cost significantly increase
Solution Approach 1:
The patent creates a universal current estimator algorithm that can estimate current for multiple PV panels using a single implementation framework. Each panel's current is estimated using its own voltage measurements and control signals processed through the same estimation algorithm, eliminating the need for separate sensor circuits for each panel while maintaining individual current measurement capability.
Data Source
AI summary
Systems, methods, and devices for use with photovoltaic micro-inverters. A control system for controlling power switches in a full bridge inverter in a DC/DC converter uses an estimate of the output current of a photovoltaic (PV) panel. The estimate is provided by a current estimator that takes as input the output voltage of the PV panel as well as the bus voltage of the DC/DC converter. Also used as input to the current estimator are two of the control signals for specific power switches in the full bridge inverter in the DC/DC converter.