⚡ PV–Battery System with Bidirectional Converter

Case-Based Control under Varying Irradiance & Load Conditions

PV–Battery integrated system using a bidirectional converter, along with a case-based battery control strategy. The model is designed to evaluate system behavior under two operating cases:1️⃣ Case 1 – Varying Irradiance Condition2️⃣ Case 2 – Varying Load Condition

A simple mode-selection logic allows switching between the two cases during simulation.

Energy Management in PV Wind Diesel Generator Battery System in MATLAB

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🧭 Case Selection Logic

A Constant block is used to select the operating case:

• 🔘 Constant = 0 → Case 1 (Varying Irradiance)

• 🔘 Constant = 1 → Case 2 (Varying Load)

Based on this selection, the controller routes the appropriate reference current to the battery control loop.

☀️ Case 1: Varying Irradiance Condition

In Case 1, the control focuses on solar PV behavior:

• 🔋 PV current is measured and scaled (×1000 A)

• 🔁 Compared with a reference current derived from irradiance logic

🧠 Battery Decision Logic (Case 1)

• 🌥️ Low irradiance → Battery discharges

• 🌞 High irradiance → Battery charges

This logic generates a battery reference current that commands charging or discharging based on available PV power.

🔌 Case 2: Varying Load Condition

In Case 2, the controller responds to load demand:

• ⚡ Load power is measured

• 🔄 Converted into an equivalent current reference

🧠 Battery Decision Logic (Case 2)

• 📈 High load demand → Battery discharges

• 📉 Low load demand → Battery charges

A base load reference is used to determine the charging/discharging threshold.

🔀 Reference Current Selection

A switching block selects the appropriate reference:

• Case 1 → PV-based reference current

• Case 2 → Load-based reference current

The selected reference current is:

• 🔍 Compared with actual battery current

• 🎯 Processed through a PI controller

• ⚙️ Converted into a duty cycle

• 📡 Sent to a PWM generator

The generated pulses control the two IGBTs of the bidirectional converter, enabling smooth battery charge/discharge operation.

🔋 Battery & PV Measurements

The following parameters are continuously monitored:

• 🔌 Battery power

• 🔋 Battery current

• ⚡ Battery voltage

• 📊 State of Charge (SoC)

• ☀️ PV power

🏷️ PV Rating Setup

• Power rating is defined in 100 kW units

• Example:

  • Value = 20 → 20 × 100 kW = 2000 kW (2 MW)

• Grid side:

  • ⚡ Line voltage: 400 V

  • 🔁 Frequency: 50 Hz

📈 PV Characteristics Analysis

The PV block allows visualization of:

• 📉 I–V characteristics

• 📈 P–V characteristics

• Performance under different irradiance and temperature conditions

✔️ Maximum PV power observed is around 2 MW, matching the system rating.⚠️ Since the PV model is inside a masked block, the Pmode output must be explicitly connected to visualize characteristics correctly.

🔌 Grid-Connected Inverter Control

The DC link connects to:

• 🔄 Three-phase inverter

• 🧲 LC filter

• 🔼 Step-up transformer

🧠 Inverter Control Strategy

• ☀️ P&O MPPT generates a reference DC voltage

• 🔍 Compared with measured DC-link voltage

• 🎯 PI voltage regulator produces Id reference

• Grid voltages and currents are transformed ABC → dq0

• Id/Iq references are compared with actual values

• ⚙️ PI + feed-forward compensation generates Vd/Vq

• 🔄 dq0 → ABC conversion

• 📡 PWM pulses control the inverter

This ensures stable power transfer from PV to grid/load.

🔀 Load Switching (Case 2)

Three loads are connected via circuit breakers:

• 🧷 Case 1: Breakers remain always ON

• 🧷 Case 2:

  • Load-1: Connected after 4.6 s

  • Load-2: Connected after 9.2 s

This controlled switching creates step changes in load demand, validating the battery control logic.

🌦️ Irradiance Profile

• Case 1: Dynamic irradiance pattern☀️ 200 → 1000 → 200 W/m² (cyclic)

• Case 2: Constant irradiance☀️ 1000 W/m²

Selection is handled automatically using the case constant.

💨 Wind & Backup Generation

🌬️ Wind Turbine (DFIG)

• 🔋 Rating: 3 MW

• Uses a DFIG model

• Rotor frequency converted via AC–DC–AC converters

• Power fed back to the point of common coupling (PCC)

• Built-in controls:

  • Pitch control

  • Speed regulation

  • Rotor-side & grid-side converter control

🛢️ Diesel Generator

• ⚡ Rating: 5 MW, 400 V, 50 Hz

• Supports PQ control and PV control

• Includes:

  • Governor (prime mover)

  • AVR (excitation control)

• Acts as a backup source in the common bus

🖥️ Simulation & Results

• ⏱️ Simulation time: 40 seconds

• 🕒 Execution time: ~10 minutes

• 📊 Scopes used:

  • PV parameters

  • Load profiles

  • Battery behavior

  • Wind generation

After simulation:

• 🔍 Use Auto-scale to view full waveforms

• 🧭 Switch between Case 1 & Case 2 to compare results

✅ Conclusion

✔️ Case-based logic enables flexible battery operation✔️ Battery responds intelligently to irradiance and load variations✔️ Bidirectional converter ensures smooth power flow✔️ Integration of PV, wind, battery, and diesel improves reliability✔️ Model is suitable for large-scale (MW-level) hybrid power systems