SOLAR PV INVERTER ( CENTRAL / STRING ) PROTECTIONS

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Protection is essential in any kind of electrical system / apparatus, to protect the equipment's heart of component / sub component's, from any kind of electrical faults either from internal or external circuits, also protection is not only for the equipment healthy life also it's more essential for human safety.

Solar PV Inverter and it's operation is heart of Solar PV power plant and it's operation. Selection of Quality Inverter is essential one to ensure to achieve committed PR ( Performance Ratio ) & Generation figures. Understanding this fact, The designer have to pay special attention to select proper inverter, to achieve higher PR, higher Generation & mainly to ensure efficient operation & healthy life of PV power plant. In Inverter selection, equipped protection features of inverter, is playing main & instrumental factor of same, compare than other factors.

Inverter by nature converting DC to AC. i.e Pulsating DC waveform to AC pure sine waveform. Grid Synchronization is important operation of every inverter, so protections are too important on AC side for every inverter, compare than DC side. Presence of grid protection of Inverter will ensure the Inverter safety & healthy life from the grid faults i.e external faults. Protecting the inverter from PV array i.e from the internal faults, by DC protection system.

Let's we will move forward to have a look, Essential required Inverter protections on DC side, AC side & mainly for Grid side.

Protections should be equipped in the ON- Grid Central / String Inverters :

DC Side :

• DC Input Units protected by : Fuse / MCCB
• DC Output protected by : DC MCCB / Motorized LBS.
• Over Voltage Protection.
• Over Current Protection.
• Ground Fault Protection.
• Negative Grounding.
• Reverse polarity.
• Anti-PID.
• Temperature Protection.
• Cooling Fan ( for IGBT ) Protection.
• DC Surge Protection.
• Insulation Monitoring.
• Leakage Current Monitoring.
• Emergency Stop button @ DC side, especially for Central Inverter.

In earlier time and even today, 1000V series string inverters have been equipped with fuses at each DC input and DC common controlling switch at DC output. Interestingly current renowned design of string inverters especially in 1500V series, Most of the inverter OEM's eliminated old design pattern of fuses at DC input, these models are mostly coming with fuse-less design at DC input and Multi DC input formed with single MPPT output and further multiple MPPT controlled by single output control switch.

AC Side :

• Under & Over Voltage Protection.
• Over Current Protection.
• Under & Over Frequency Protection.
• Earth Fault Protection.
• Leakage Current Monitoring.
• Insulation Monitoring.
• Short Circuit Protection.
• AC Surge Protection.
• Reverse Polarity.
• AC Output controlled by : Isolator / MCCB / ACB.

Grid Supportive Features / Protections :

• Voltage Ride through Protection : Low Voltage RT (LVRT) / High Voltage RT (HVRT).
• Frequency Ride through (FRT).
• Islanding Protection.
• Active & Reactive Power Control regulation.
• pf (Power Factor) Control.
• Reactive Power at Night time.
• Automatic wake-up / soft shut down.

The above mentioned protections are essential for every grid connected Central & String Inverter, However some protections couldn't possible to implement at string inverter because of size & DC handling capacity.

Before procuring inverter for your PV plant, kindly take comparative analysis of proposed inverter GTP with this post. Check whether these protections are equipped in the proposed inverter or not, in parallel also check whether inverter OEM ( Original Equipment Manufacturer ) obtained IEC certification for his inverter equipped with above protections or not ? This quality analysis will help to ensure to achieve higher PR & Generation than committed, also it will mainly help to reduce time frame of Pay back years.