People often hear about inverters featuring "support for three-phase unbalanced output." However, what does this feature entail?
What Is a Three-phase AC System?
A three-phase AC system is a power system composed of three alternating circuits with the same frequency, equal voltage amplitudes, and phase differences of 120° between each other.
Three-phase power systems are known for their high transmission efficiency and stable power output, making them suitable for powering large equipment while reducing energy consumption and costs. They allow for smooth motor startup and operation, reducing vibration and noise, extending equipment lifespan, and effectively minimizing harmonic interference. This leads to more balanced load distribution and higher power density.
Due to these advantages, three-phase power is widely used in various settings. For example, homes in countries like Germany and Austria use three-phase power, and commercial and industrial buildings such as shopping centers, parking lots, and factories commonly employ three-phase AC systems.
Why Does Three-phase iImbalance Occur?
Ideally, the power load connected to each phase in a three-phase circuit should remain consistent. However, in practical scenarios where both single-phase and three-phase loads are used simultaneously, this often leads to a three-phase imbalance. Three-phase imbalance refers to the situation where the magnitude of the current in the three phases of the power system is unequal, with the difference exceeding the specified range.
1.When the power difference between the operating equipment in the three phases exceeds a certain value, it results in an imbalance in three-phase power usage.
2.Since different countries have regulations on grid output and specific requirements regarding three-phase imbalance, inverters are needed to control the output power of each phase accordingly.
What Are the Risks Associated with Three-phase Imbalance?
Increased Losses in the Power Grid and Equipment: In a three-phase unbalanced load situation, current flows through the neutral line, causing losses in both the phase and neutral lines, which increases the overall power grid losses.
Increased Losses in Distribution Transformers: When three-phase loads are unbalanced, the distribution transformer operates in an asymmetrical state, which increases its losses (including no-load losses and load losses), affecting its lifespan and efficiency. Excessive zero-sequence current can cause local metal parts to overheat and may even lead to transformer failure.
Impact on the Safe Operation of Electrical Equipment: Three-phase imbalance can cause unbalanced output voltage, affecting the normal operation of electrical equipment and potentially causing damage to the equipment.
Reduced Motor Efficiency: Unbalanced voltage leads to reduced motor efficiency, increased temperature rise, and higher reactive power losses.
How Does the Hinen Inverter Achieve the "100% Three-Phase Unbalanced Output Function"?
When a photovoltaic (PV) system is connected to a three-phase power grid, the equipment may output different amounts of power to each phase. If the power is too high or unbalanced, it can impact the grid, so it is necessary to limit the output power of each phase to ensure that it remains within a safe range.
This is where the inverter and a three-phase smart meter work together. The smart meter monitors the power drawn by each phase from the grid in real time and provides feedback to the Hinen inverter. The inverter system, through internal software, independently controls the power for each phase, ensuring that the power drawn from the grid remains balanced. This reduces the impact of grid imbalance and improves the overall stability of the grid system. When using the three-phase unbalanced output function, if the load power is less than the maximum power capacity for a single phase, no power needs to be drawn from the grid.
Next, we’ll showcase how Hinen products achieve the 100% three-phase unbalanced output function by using the A20000t and H12000t models in a zero-export power limit scenario.
Conclusion
In summary, the inverter's "three-phase unbalanced output" function is especially important in complex load environments. It effectively addresses voltage fluctuations caused by unbalanced loads, enhancing the stability and reliability of system operations. Additionally, it helps reduce equipment failures and energy losses. As smart grids and distributed energy systems continue to evolve, this feature will play a critical role in more application scenarios, providing a solid foundation for the efficient and safe operation of power systems.
