Solar Drive System Frequency-Based MPPT Control
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Solution Overview
Problem
Conventional photovoltaic array power measurement using ADCs has poor accuracy due to non-linearities, leading to suboptimal performance and inefficient power transfer, as the maximum power point tracking (MPPT) relies on accurate power measurements which are often unreliable.
Innovation Solution
The solar drive system employs the Perturb and Observe (P&O) MPPT method, where the present rotational frequency of the electric motor is used to determine the step direction, eliminating the need for precise power measurements, thus improving the tracking of the maximum power point with increased accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ADC-based power measurement is used, then the measurement system is simple, but the measurement precision deteriorates due to non-linearities
Solution Approach 1:
The patent extracts the power measurement function from the traditional ADC-based system and replaces it with a frequency-based measurement approach. By measuring the frequency of the AC current directly (which is proportional to power) rather than measuring voltage and current separately and computing power through ADCs, the system eliminates the sources of measurement error while maintaining simplicity.
Solution Approach 2:
The patent substitutes the electronic measurement system (ADCs performing analog-to-digital conversion and arithmetic calculations) with a frequency measurement system. The frequency of the AC current serves as a direct indicator of power, replacing the complex electronic measurement and computation chain with a simpler frequency detection mechanism.
2Reliability
If Perturb and Observe MPPT method is used with traditional power measurement, then the MPPT function is implemented, but the reliability deteriorates due to inaccurate power measurements
Solution Approach 1:
The patent implements a feedback mechanism where the measured frequency (which directly reflects power) is used to determine the next perturbation step in the MPPT algorithm. This feedback loop uses reliable frequency measurements instead of inaccurate power measurements, ensuring that the MPPT process reliably converges to the maximum power point without being misled by measurement errors.
Solution Approach 2:
The patent introduces frequency as an intermediary parameter between the photovoltaic array output and the MPPT control decision. Instead of using directly measured power (which is inaccurate), the system uses frequency as a mediator that reliably indicates power level and guides the MPPT perturbations, eliminating the impact of ADC non-linearities on MPPT reliability.
3Reliability
If frequency-based MPPT control is used, then the MPPT reliability is improved, but the device complexity increases due to additional frequency measurement
Solution Approach 1:
The patent makes the frequency measurement serve multiple functions: it is used both for MPPT control (determining perturbation direction) and for protective functions (detecting islanding conditions and abnormal operating states). This multi-functionality means that the frequency measurement infrastructure supports multiple critical system functions without requiring separate measurement systems, thereby avoiding additional complexity while improving reliability.
Solution Approach 2:
The system uses the existing AC current waveform that is already present in the system for frequency measurement purposes. The same current that drives the motor also provides the frequency information needed for MPPT and protection functions. The system essentially measures what is already there (the operating current frequency) and uses it for multiple control purposes, avoiding the need for additional sensors or measurement devices.
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
This approach allows for more accurate tracking of the maximum power point, enhancing the efficiency of power transfer from the photovoltaic array to the electric motor by focusing on the monotonicity of power changes rather than absolute power levels, thereby improving the overall performance of the solar drive system.
Implementation Method 1
at least one photovoltaic array generating a DC current
Data Source
AI summary
A solar drive system, having: at least one photovoltaic array generating a DC current; at least one inverter electrically connected to the photovoltaic array for inverting the DC current into an AC current; at least one electric motor electrically connected to the inverter for supplying the electric motor with the AC current; and at least one device for determining a present rotational frequency of the electric motor; wherein the inverter is configured to track a maximum power point of the photovoltaic array by performing a Perturb and Observe Maximum Power Point Tracking method and to determine a step direction of the Perturb and Observe Maximum Power Point Tracking method using the determined present rotational frequency of the electric motor.