Can I connect two solar inverters together and how do I do that?

Absolutely. Sometimes a single inverter cannot provide enough power to meet the demand. In such cases, connecting two inverters in parallel becomes a practical solution. This approach is commonly used for off-grid solar systems, backup power setups, and other scenarios requiring higher power (e.g., industrial applications).

This blog will explain the detailed process of connecting two inverters in parallel, from basic concepts to step-by-step instructions.

Why parallel inverters?

Capacity expansion

Increasing capacity is a key driver. As energy demand increases, especially for larger facilities, adding more inverters allows more solar panels to be integrated, significantly increasing the overall energy output of the system. This scalability makes it easy to meet the growing energy needs of the system without having to replace equipment.

Redundancy

In large solar systems, a fail-safe mechanism can be achieved by using a configuration with multiple inverters connected in parallel. If one inverter fails, the others can continue to operate, ensuring that the system continues to operate and that energy production does not come to a complete halt.

Improved efficiency

Multiple inverters can optimize energy distribution, adjusting power output according to real-time load demand to match the power needs of each part of the system. The system can more efficiently balance the flow of energy, avoiding overloading or underloading certain parts of the system and improving the stability and efficiency of the overall system.

❗Potential danger

• Inaccurate settings: If there are communication problems or improper coordination between inverters, it can lead to unstable system operation or failure.
• Power mismatch: Inverters of different brands and models may have different power characteristics, leading to power mismatch problems when operating in parallel.
• Connection procedure: Connections must be made correctly to avoid possible damage.

Preparation before paralleling inverters

There are some key things to prepare for before you start paralleling two inverters:

Compatibility Check

• Voltage compatibility: Input and output voltages must match when inverters are connected in parallel.
• Frequency compatibility: The output frequencies of the inverters must match to ensure proper system operation. In most cases, the output frequency is typically 50 Hz or 60 Hz, depending on the region and system requirements.
• Phase Synchronization: The inverter must be able to synchronize its output phases to avoid phase mismatch, which can cause damage to the equipment.

Choose the right cables and connectors.

• Cable size: Select a cable that is large enough to handle the combined current output of both inverters. Cables that are too small may not be able to handle high current loads and may overheat, resulting in voltage drops and system performance issues.
• Connectors: The use of high-quality connectors is essential to ensure a safe and reliable connection. Especially for high-current applications, choose connectors that are specifically designed for such applications to ensure a solid, low-resistance connection that reduces the risk of overheating and electrical problems.

Safety Precautions

• Isolation: During initial installation, ensure that inverters are sufficiently isolated from each other to prevent accidental short circuits. Inverters should be properly installed and isolated according to the manufacturer's guidelines.
• Fuses and circuit breakers: Installing properly rated fuses or circuit breakers is an important measure to protect the system from overcurrent conditions. These protective devices can shut down the circuit if the current exceeds a safe range, preventing damage to equipment or hazards such as fire.
• Grounding: Ensure the inverter system is properly grounded to minimize the risk of electric shock and protect the equipment from electrical faults. Good grounding is one of the most important factors in ensuring safe system operation.

Step-by-step guide for connecting two inverters:

Before making the parallel connection, ensure that the system is de-energized and that appropriate safety precautions are taken, such as disconnecting the main supply.

1️⃣Securing inverter: Ensure that each inverter is securely fastened to the mounting surface to prevent damage from vibration or movement. Proper installation is essential for long-term stability and performance.

2️⃣Connecting the DC input: Connect the DC input from the solar panel to the DC input terminal of each inverter, connecting the positive terminal of the inverter to the positive terminal of the battery or DC power supply and repeating the same steps for the negative terminal. Ensure that the connections are secure and that the wiring is sized for the combined current.

3️⃣Connect the AC outputs: Use a combiner box or parallel connection kit to interconnect the AC outputs of each inverter. This will combine the outputs into a single AC output. Follow the manufacturer's instructions to ensure a safe and efficient connection.

4️⃣Grid or load connection: Depending on your system design, the combined AC outputs will be connected to the main switchboard or directly to the grid. Correct synchronization with the grid is essential for stable operation. This step allows the inverter to deliver power in parallel to your home or the grid.

Test the system

1️⃣Switch on each inverter in turn and observe the indicator lights. Check that they are correctly energized and that there are no fault indications. Check that each inverter is operating correctly and ready for synchronization.

2️⃣Use a multimeter to measure the AC output voltage and frequency. Make sure they are within the expected range. In a grid-tied system, check that each inverter is correctly synchronized to the grid frequency and voltage. This step is critical to ensure that the system operates in harmony with the grid and to avoid potential interruptions.

3️⃣Evaluate the performance of each inverter using a monitoring tool or software. Ensure that all inverters are operating efficiently within specified parameters and producing the expected energy output. This step will help identify any problems early and ensure optimum system performance.

Common problems troubleshooting

Phase mismatch: If the inverters are not properly synchronized, a phase mismatch may occur. This can cause interference, equipment failure, or damage. To resolve this problem, check the synchronization settings and wiring connections.

Overheating: Ensure that the inverter is adequately ventilated and not overloaded. If overheating occurs, reduce the load or improve the cooling system.

Can 2 inverters be connected to 1 battery?

Yes, you can connect any number of inverters to the battery, provided they all meet the following conditions:

• Inverter type: Ensure that the selected inverter supports multiple inverters connected in parallel to the same battery system.
• Communication protocols: Inverters often need to communicate with the battery for effective energy management. Make sure the two inverters can work together and avoid conflicts.
• Power distribution: It is necessary to ensure that the power distribution and control between the two inverters is efficient to avoid overload or imbalance.
• Safety: When connecting several inverters to the same battery system, it is necessary to ensure the safety and stability of the system, especially during charging and discharging.
• Design and installation: Electrical wiring, protection devices, control systems and other aspects must be considered when designing the system to ensure that the system can operate properly.

Conclude

Connecting two inverters in parallel in a solar system can be an effective way to increase the power output and reliability of the system. However, this practice can also increase system complexity and cost. Before implementing parallel connection of solar inverters, carefully weigh the pros and cons to determine if it is the right solution for your solar system. If you're not sure how to proceed, it's best to consult a professional solar installer. They can advise you on the design and configuration of your system and ensure that it is safe and efficient.