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DRCC, A Maximum Power Point Tracking Technique for Photovoltaic Applications

DRCC, A Maximum Power Point Tracking Technique for Photovoltaic Applications. Jonathan Kimball Power Affiliates Program, May 11, 2007. What is maximum power point tracking? Ripple correlation control Discrete-time ripple correlation control (DRCC) Conclusions. Overview.

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DRCC, A Maximum Power Point Tracking Technique for Photovoltaic Applications

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  1. DRCC, A Maximum Power Point Tracking Technique for Photovoltaic Applications Jonathan Kimball Power Affiliates Program, May 11, 2007

  2. What is maximum power point tracking? Ripple correlation control Discrete-time ripple correlation control (DRCC) Conclusions Overview

  3. Photovoltaic panels (solar panels) have a well-defined operating point that delivers maximum power An MPPT actively seeks this operating point This is a special case of optimal control Maximum Power Point Tracking

  4. PV Panel Characteristics • A PV cell can be modeled as a current source and a diode • Maximum power is delivered near the “knee” of the curve

  5. Perturb & Observe Move the operating point Observe the change in power Keep moving towards higher power Fractional Open-Circuit Voltage Periodically sample unloaded voltage Control voltage to be kVoc Many others MPPT Techniques

  6. Objective: Track optimum on the time scale of the switching frequency RCC exploits the inherent switching ripple Posed as a general-purpose optimal control technique Previously implemented as an analog MPPT Some research has been done for electric machine efficiency maximization Ripple Correlation Control

  7. RCC Theory • Generic cost function J to be optimized • J is only a function of z, a relevant state variable • Control law generates u, the input to the plant

  8. RCC has been proven stable Implementation is somewhat problematic Time derivatives Analog multipliers Digital implementation can reduce power consumption, improve overall robustness Discrete-Time RCC

  9. DRCC Algorithm • Switching waveforms are close to piecewise linear • Substitute this approximation and simplify • Reduces to a sampling problem

  10. Sampling

  11. Fractional Voc is robust, but inaccurate DRCC is accurate and efficient when maximum is well-defined Mode-switching uses fractional Voc to re-initialize operation near the maximum power point Mode-Switching

  12. Mode Switching for Robust Operation

  13. Maximum power point tracking is an important element of a photovoltaic system DRCC is a robust, accurate MPPT method DRCC also has applications in motor efficiency maximization, other optimal controllers Summary

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