Single Phase Grid Connected Solar PV and Battery with INC MPPT

👋 Introduction

Hi viewers, welcome to LMS Solution. Today we are going to see the MATLAB/Simulink implementation of a single-phase grid-connected solar PV and battery system using the Incremental Conductance (INC) MPPT algorithm.This system demonstrates how solar PV, battery energy storage, and the utility grid can work together to ensure maximum power extraction, stable DC-link operation, and controlled power injection into the grid.

🧩 Overall System Configuration

The complete system consists of the following main components:

• ☀️ Solar PV Array

• ⬆️ Boost Converter with INC MPPT

• 🔋 Battery Energy Storage System (BESS)

• 🔁 Bidirectional DC–DC Converter

• 🔄 Single-Phase Full-Bridge Inverter

• 🌐 Utility Grid (110 V, 50 Hz)

• 🏠 Local DC and AC Loads

All components are connected through a common DC bus, which plays a key role in power exchange.

☀️ Solar PV Array Modeling

The PV system is built using four series-connected solar panels.

🔹 Single panel rating

• Power: 250 W

• Voltage at MPP (VMPP): 30.7 V

• Current at MPP (IMPP): 8.15 A

🔹 Total PV capacity

• 4 panels × 250 W = 1 kW (1000 W) at STC

• Conditions: 1000 W/m² irradiance, 25°C temperature

📈 PV Characteristics

• At 1000 W/m² → ~1000.8 W

• At 800 W/m² → ~800 W

• At 600 W/m² → ~598.86 W

• At 400 W/m² → ~396.1 W

👉 These nonlinear I–V and P–V characteristics clearly show the need for MPPT.

🎯 Why Incremental Conductance (INC) MPPT?

Because PV characteristics are nonlinear and vary with irradiance and temperature, direct operation cannot guarantee maximum power extraction.

✔️ INC MPPT advantages:

• Tracks MPP based on slope condition

• Faster and more accurate than simple P&O under rapidly changing irradiance

• Uses the condition:

  dIdV=−IVat MPP\frac{dI}{dV} = -\frac{I}{V} \quad \text{at MPP}dVdI​=−VI​at MPP

🧠 INC MPPT Algorithm Logic

The INC MPPT block receives:

📥 Inputs

• PV voltage (V)

• PV current (I)

📐 Calculated signals

• ΔV = V(n) − V(n−1)

• ΔI = I(n) − I(n−1)

🔹 First set of conditions

• If ΔV = 0 and ΔI = 0 → system already at MPP

  • ✅ Duty cycle unchanged

• If ΔV = 0 and ΔI > 0 → move toward MPP

  • 🔽 Decrease duty cycle

• If ΔV = 0 and ΔI < 0 → move away from MPP

  • 🔼 Increase duty cycle

🔹 Incremental Conductance condition

• If ΔI/ΔV = −I/V → at MPP

• If ΔI/ΔV > −I/V → decrement duty cycle

• If ΔI/ΔV < −I/V → increment duty cycle

🔒 Duty cycle limits

• Duty cycle is checked against minimum and maximum limits

• If violated, previous duty cycle is retained

📌 This logic runs continuously at each sampling instant.

⬆️ Boost Converter Operation

The boost converter performs two tasks:

• ⚡ Extract maximum power from the PV using INC MPPT

• 🔋 Boost PV voltage from ~120 V to ~220–225 V DC

🎛️ Control Strategy

• Duty cycle from INC MPPT → PWM generator

• PWM pulses → boost converter switch

Result:

• PV operates close to MPP

• DC bus receives regulated power

🔋 Battery Energy Storage System (BESS)

The battery provides energy buffering between PV, load, and grid.

🔹 Battery specifications

• Rated voltage: 48 V

• Capacity: 50 Ah

• Initial SOC: 50%

🔁 Bidirectional DC–DC Converter (Battery Interface)

The battery is connected to the DC bus through a bidirectional converter.

🎯 Why voltage-controlled bidirectional converter?

• PV and battery share the same DC bus

• A stiff DC bus is required for stable inverter operation

• Enables:

  • PV → Battery charging

  • Battery → DC bus discharging

🎛️ Control Method

• DC-link voltage measured

• Compared with reference voltage (225 V)

• Error processed via PI controller

• PI output → PWM generator

• Complementary pulses drive the two IGBTs

🔄 Operating modes:

• 🔋 Charging mode: surplus PV power

• ⚡ Discharging mode: PV deficit or load demand

🔄 Single-Phase Inverter Control

The inverter transfers power from DC bus to AC grid.

🔹 Grid specifications

• Voltage: 110 V RMS

• Frequency: 50 Hz

🔹 Current-Controlled Inverter

• Reference grid current set to 3 A (peak)

• Converted into sinusoidal waveform using PLL

🔹 Control Steps

1. Grid voltage → PLL → sin/cos signals

2. Reference current × sine wave → sinusoidal current reference

3. Clarke transformation applied

4. Actual inverter current transformed to α–β frame

5. Error processed via PI current controller

6. Control signal → inverse transform

7. Final signal → sinusoidal PWM generator

📌 PWM pulses control the full-bridge inverter.

🏠 Load and Grid Interaction

• 🏠 Local DC load connected to DC bus

• 🔌 AC load and grid connected on inverter side

The inverter injects controlled current into the grid while supporting local loads.

🌦️ Irradiance Change Test

The system is tested by varying irradiance:

• 1000 → 500 → 1000 W/m²

This validates:

• MPPT response

• Battery charging/discharging

• Grid power exchange

📊 Simulation Results – Key Observations

☀️ PV Side

• PV voltage ≈ 120 V

• PV current ≈ 6 A

• PV power ≈ 800 W at high irradiance

📌 INC MPPT extracts ~80% efficiency under fast irradiance transitions.

🔋 DC Bus

• DC-link voltage maintained around 225 V

• Stable despite irradiance changes

🔋 Battery Behavior

• Initial charging when PV power is high

• Switches to discharging when irradiance drops

• SOC increases and decreases smoothly

🌐 Inverter & Grid

• Inverter voltage ≈ 110 V RMS

• Grid current follows reference (~3 A peak)

• Smooth power injection into the grid

⭐ Key Highlights of the System

• ☀️ INC MPPT for PV power extraction

• 🔋 Battery buffering improves reliability

• 🔁 Bidirectional power flow (charge/discharge)

• 🌐 Stable grid-connected operation

• ⚡ DC bus voltage tightly regulated

🏁 Conclusion

This MATLAB/Simulink model demonstrates a single-phase grid-connected solar PV and battery system using Incremental Conductance MPPT. The system successfully manages power flow between PV, battery, load, and grid while maintaining DC-link stability and controlled grid current injection. The results clearly show the dynamic interaction of MPPT, battery charging/discharging, and grid support under varying irradiance conditions.