Solar Hybrid PCU MPPT Based Internal Circuitry

Let’s break down the internal circuitry of a Solar Hybrid PCU (Power Conditioning Unit) with an isolation transformer and UART connectivity for Bluetooth/Wi-Fi dongles. This is a complex system, so we’ll cover the major blocks and their functions.

1. Solar Input Stage (PV Array Connection)

• PV Array Input: Connects to the solar panels.
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  Solar System with battery and Solar Panels

   

• DC Disconnect Switch: For safety, allowing isolation of the PV array.
• Surge Protection Device (SPD): Protects against voltage surges from lightning strikes.
• Blocking Diode (or MOSFET): Prevents reverse current flow from the battery to the PV array.   
• MPPT (Maximum Power Point Tracking) Controller:
• This is a crucial component. It optimizes the power extracted from the solar panels by constantly adjusting the voltage and current.   
• It uses algorithms to find the maximum power point under varying irradiance and temperature conditions.  
• Typically uses a DC-DC converter (buck, boost, or buck-boost) controlled by a microcontroller.

2. DC-DC Conversion Stage (MPPT Output to DC Bus):

• DC-DC Converter (from MPPT): Converts the variable DC voltage from the MPPT controller to a stable DC bus voltage.
• Capacitors: Smooth out voltage ripples on the DC bus.
• Current Sensors: Measure the current flow for monitoring and control.

Internal circuitry of Hybrid Solar MPPT PCU

3. Battery Charging and Management Stage:

• Battery Connection: Connects to the battery bank.   
• Battery Disconnect Switch: For safety and maintenance.
• Charge Controller:
• Manages the charging process, preventing overcharging and deep discharge.
• Monitors battery voltage, current, and temperature.
• Uses algorithms like constant current/constant voltage (CC/CV) charging.
• Battery Protection Circuit: Includes fuses, circuit breakers, and temperature sensors for battery safety.

4. DC-AC Inverter Stage:

• DC Bus: The stable DC voltage from the MPPT and battery stages.
• Inverter Bridge:
• Uses MOSFETs or IGBTs to convert the DC voltage to AC voltage.
• Generates a sinusoidal AC waveform.   
• Typically uses a full bridge configuration.
• LC Filter: Filters out high-frequency harmonics from the inverter output, producing a clean sinusoidal AC waveform.
• Current and Voltage Sensors: Monitor the AC output for feedback control.

5. Isolation Transformer Stage

• Isolation Transformer:
• Provides galvanic isolation between the inverter output and the AC load.
• Enhances safety by preventing ground loops and electrical shocks.
• Can also step up or step down the AC voltage if needed.
• AC Output: Connects to the AC load or the grid.
• AC Disconnect Switch: For safety and maintenance.
• Relays: To connect or disconnect the grid or generator input.

7. Control and Monitoring Stage

• • • The “brain” of the PCU is Microcontroller or MCU which has the software embedded. It has the provision of adding features later on as per the requirements.
    • Controls all the stages, including MPPT, battery charging, and inverter operation. As the Solar PCU need complex software to control the MPPT solar charge controller and the Inverter and it has all the Inverter software written in the MCU having 2 to 4 UART ports for the communication purpose.
    • Implements algorithms for power management, as there are PWM channels to create Sinewave, Charging waveform, voltage and current control in various conditions and protection, and communication.

    • 

      # phase Waveform of BESS

    • Monitors sensors and controls switches and relays.
    • Display: Shows system parameters like voltage, current, power, and battery status, there are LEDs or can be a LCD display
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    • UART (Universal Asynchronous Receiver/Transmitter):
      • Provides a serial communication interface.
      • Connects to a Bluetooth or Wi-Fi dongle.
      • Allows remote monitoring and control of the PCU via a smartphone or computer. 
      • 

        Solar PCU wiring

         
      • Bluetooth/Wi-Fi Dongle:
        • Enables wireless communication.
        • Transmits system data and receives control commands.
        • Data Logging: Stores system data for analysis.

8. Protection Circuitry

• Overvoltage Protection (OVP): Protects against excessive voltage.
• Undervoltage Protection (UVP): Protects against low voltage.
• Overcurrent Protection (OCP): Protects against excessive current.   
• Short Circuit Protection (SCP): Protects against short circuits.   
• Over Temperature Protection (OTP): Protects against overheating.   
• Ground Fault Protection: Protects against ground faults.
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UART and Wireless connectivity:

The UART port is used to communicate with the Bluetooth or Wi-Fi dongle. The microcontroller sends and receives data through the UART. This data contains system parameters, status information, and control commands. The dongle then transmits this data wirelessly to a connected device (smartphone, computer, or cloud server).

Key Considerations:

• Efficiency: High efficiency is crucial to minimize power losses.   
• Reliability: The PCU must be reliable and robust, especially in harsh environments.
• Safety: Safety is paramount, with multiple protection mechanisms in place.

This breakdown provides a general overview. The specific implementation details can vary depending on the manufacturer and the intended application.