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Power Management of Solar PV Battery Supercapacitor in DC Microgrid

Power Management of Solar PV Battery Supercapacitor in DC Microgrid


Introduction to the DC Microgrid

A DC microgrid is a decentralized power system that integrates various renewable energy sources and storage systems to provide reliable and efficient power. Our model includes:

  • Solar PV system

  • Battery energy storage

  • Super capacitor storage system



System Components and Specifications

  1. Solar PV Panel:

  • Total Rating: 2000 watts

  • Individual Panel Rating: 250 watts

  • Open Circuit Voltage: 37.3 volts

  • Voltage at Maximum Power Point: 30.7 volts

  • Short Circuit Current: 8.66 amps

  • Current at Maximum Power Point: 8.15 amps

  1. IV and PV Characteristics:

  • At 1000 W/m²: Maximum power is around 2002 watts, voltage is 245.6 volts.

  • At 800 W/m²: Maximum power is 1599 watts.

  • At 600 W/m²: Maximum power is 1197 watts.

  • At 400 W/m²: Maximum power is 791.8 watts.

  • At 200 W/m²: Maximum power is around 200 watts.

  1. Battery Energy Storage:

  • Nominal Voltage: 220 volts

  • Rated Capacity: 48 Ah

  • Initial State of Charge: 50%

  1. Super Capacitor:

  • Rated Capacitance: 99.5 farads

  • Rated Voltage: 300 volts

  • Initial Voltage: 295 volts



Control Logic

The system operates using a combination of voltage and current control loops to ensure optimal power management. Here’s how it works:

  1. Solar PV System:

  • Connected to the DC bus (maintained at 400 volts) via a boost converter.

  • Uses Maximum Power Point Tracking (MPPT) with the Incremental Conductance algorithm to maximize power extraction under varying irradiance conditions.

  1. Battery and Super Capacitor:

  • Connected to the DC bus via bidirectional converters.

  • Use a double-loop control strategy:

  • Outer Loop (Voltage Control): Compares the actual DC bus voltage with the reference voltage (400 volts) and processes the error through a PI controller to generate a reference current.

  • Inner Loop (Current Control): Compares the reference current with actual currents and processes errors through PI controllers to generate duty cycles for controlling the bidirectional converters.

Simulation Results

The model simulates various irradiance conditions to demonstrate how power management adapts to changing inputs:

  1. PV Voltage and Current:

  • PV voltage remains around 245-250 volts.

  • PV current varies with irradiance, maintaining around 8 amps at 1000 W/m² and decreasing as irradiance drops.

  1. DC Bus Voltage:

  • Maintained consistently at 400 volts.

  1. Load Conditions:

  • DC load is constant at 1000 watts.

  1. Battery and Super Capacitor Response:

  • 0-2 seconds: PV power is greater than load power. Excess power charges the battery and super capacitor.

  • 2-3 seconds: PV power matches load power. Battery discharges minimally, and the super capacitor remains neutral.

  • 3-5 seconds: PV power drops below load power. Battery discharges to compensate, and the super capacitor provides transient support during rapid changes in irradiance.

Conclusion

This model effectively demonstrates how solar PV, battery, and super capacitors can be managed within a DC microgrid to ensure stable and efficient power delivery. By utilizing MPPT and bidirectional converters with robust control logic, the system can adapt to varying irradiance conditions, maintaining a consistent DC bus voltage and efficiently sharing power between the PV array, battery, and super capacitor.

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