SOLAR CHARGE CONTROLLERS

The article talks about one of the main types of solar charge controllers i.e. Maximum Power Point Tracking (MPPT) that is widely used in the off-grid solar industry and an efficient option to charge a battery.

Solar photovoltaic (PV) based systems are among those renewable energy systems that are now at the top eco-friendly renewable energy solutions for power generation. Solar charge controller or charger regulator is a device that regulates the voltage and current in between solar panels and the battery. A ‘12 volt’ rated panel output is about 16 – 20 volts and if there is no regulation, the batteries will be damaged from overcharging as most of the batteries are needed voltage in between 13 to 14.5 volts to get fully charged.

The two main types of solar charge controllers are widely available i.e. Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT). Both technologies are widely used in the off-grid solar industry and are both efficient options to charge a battery.

Why MPPT is required
Since MPPT charge controllers can vary the charge current to the battery, the regulator can be a multi-stage charger with bulk, absorption, and float settings. They are always solid state; this means heat dissipation can become a problem, especially, in large solar arrays. MPPT controllers are typically step-down converters, so the array voltage always needs to be higher than the battery voltage. BS-EN 50530, European Standard provides a procedure for the measurement of accuracy of the maximum power point tracking (MPPT) of inverters, which are used in grid-connected photovoltaic systems. In that case, the inverter energises a low voltage grid of stable AC voltage and constant frequency. Both the static and dynamic MPPT efficiency is considered.

The Ministry of New and Renewable Energy (MNRE) has suggested that solar pumping controller should have MPPT ports for solar PV and provision for battery using bidirectional converter. For capacity of pump controller more than 7.5 HP, there must be multiple channel MPPT to enhance efficiency, to reduce degradation problems and partial shading problems.

Advantages of MPPT
• MPPT controllers offer a potential increase in charging efficiency up to 30 per cent.
• These controllers also offer the potential ability to have an array with higher input voltage than the battery bank.
• Available up to size of 80 amps.
• MPPT controller warranties are typically longer than PWM units.
• MPPT offer great flexibility for system growth.
• MPPT is the only way to regulate grid connect modules for battery charging.
• Lower cabling cost and lower cabling losses.

Major Thrust Area of Research in MPPT

• Power Conditioning Units (PCU) with high weighted average efficiency inverters (with MPPT) and Charge Controllers for off-grid solar power plants. Power Conditioning Units (PCU) with high weighted average efficiency inverters (with MPPT) for low capacity solar power plants for grid connected (Grid Exporter) configuration
• High Efficiency BLDC Motors (with MPPT) for solar pump configurations.
• High Efficiency inverters (with MPPT) for driven of solar AC pumps.



Dr. Neelam Rathore
Department of Renewable Energy Engineering,
MPUAT, Udaipur

Dr. Prashant Singh Rathore
Department of Renewable Energy Engineering,
MPUAT, Udaipur.

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