A boost DC-DC converter is used to control the solar PV power. The boost converter operates in both MPPT mode and voltage control mode. The voltage control mode is used only when load power is less than the maximum power generated by solar PV plant given the incident irradiance and panel temperature.
Boost converter is used to obtain this maximum power point which helps in step down the array voltage to the maximum operating point voltage. So by using MPPT algorithm and boost converter solar array is operated at maximum power point irrespective of solar irradiance.
Maximum power point tracking (MPPT) is an algorithm implemented in photovoltaic (PV) inverters to continuously adjust the impedance seen by the solar array to keep the PV system operating at, or close to, the peak power point of the PV panel under varying conditions, like changing solar irradiance, temperature, and load.
solar inverters implement MPPT algorithms to maximize the power generated by PV systems. The algorithms control the voltage to ensure that the system operates at “maximum power point” (or peak voltage) on the power voltage curve.MPPT algorithms are typically used in the controller designs for PV systems. The algorithms account for factors such as variable irradiance (sunlight) and temperature to ensure that the PV system generates maximum power at all times.
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Perturbation and observation (P&O): This algorithm perturbs the operating voltage to ensure maximum power. While there are several advanced and more optimized variants of this algorithm.
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Incremental conductance: This algorithm, shown below, compares the incremental conductance to the instantaneous conductance in a PV system. Depending on the result, it increases or decreases the voltage until the maximum power point (MPP) is reached. Unlike with the P&O algorithm, the voltage remains constant once MPP is reached.
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Fractional open-circuit voltage: This algorithm is based on the principle that the maximum power point voltage is always a constant fraction of the open circuit voltage. The open circuit voltage of the cells in the photovoltaic array is measured and used as in input to the controller.
- Method 1
- Method 2
- Flowchart
- MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used for extracting maximum available power from PV module under certain conditions.
- The main benefit of MPPT charge controllers is that they can increase the charging efficiency and the power output of the solar system, especially in low-light or cold conditions, where the solar panels produce more voltage than the battery bank can handle.
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Vinput = 250 - 350V
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Voutput = 600V
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Rated Power = 100KW
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Switching frequency, fsw=5KHz
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Current ripple, I = 5%
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Volatge ripple, V = 1%
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Input Current = 100Kw/250=400A
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Current Ripple = 5% of 400 = 20A
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Voltage Ripple = 1% of 600 = 6V
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Output Current = 100Kw/600 = 166A
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Inductance , L= [Vip(Vop - Vip)]/fsw * I * Vop = 1.45mH
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Capacitance, C= [Iop(Vop - Vip)]/fsw * V * Vop = 3227uF
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Schematic Diagram
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MPP Voltage
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Verification in Scope
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Changing the irradiation to 500W/m^2
The main factor to be considered while designing any converter is the ripple current through the inductor.
- For the main aim of the project the boost converter is to be used along with a Maximum Power Point Tracking control mechanism. The MPPT is responsible for extracting the maximum possible power from the photovoltaic and feed it to the load via the buck-boost converter which steps up the voltage to required magnitude.