Analysis of Core Performance Parameters of Solar Photovoltaic Inverters

A solar photovoltaic inverter is a power regulation device built on semiconductor components, with its core function being the conversion of direct current (DC) electricity into alternating current (AC) electricity. Its typical structure consists of two parts: a boost circuit and an inverter bridge circuit. The boost circuit raises the DC voltage from the solar cells to the level required for inverter output control. The inverter bridge circuit then converts the boosted DC voltage into an AC voltage that matches the grid frequency.

This device is also referred to as a power regulator. In photovoltaic power generation systems, inverters can be classified by application scenario into off-grid type and grid-connected type. Based on waveform modulation methods, they include square wave, step wave, sine wave, and combined three‑phase inverters. For grid‑connected systems, dedicated inverters are further divided into transformer‑equipped and transformer‑free types.

The core performance parameters of solar photovoltaic inverters are as follows:

Rated output voltage

Within the allowable fluctuation range of the specified input DC voltage, the inverter must be capable of delivering the rated voltage value. Typically, the rated single‑phase output is 220V, and three‑phase output is 380V. Voltage fluctuation deviations are specified as:

• During steady‑state operation, deviation usually does not exceed ±5% of the rated value.
• Under sudden load changes, deviation shall not exceed ±10% of the rated value.
• Under normal conditions, three‑phase output voltage unbalance should be ≤8%.
• Distortion requirements for the output AC voltage (sine wave): three‑phase output ≤5%, single‑phase output ≤10%.
• Under normal operation, frequency deviation of the AC output should be ≤1%. According to national standard GB/T 19064-2003, the output voltage frequency range is 49Hz to 51Hz.

Load power factor

This parameter reflects the inverter's ability to drive inductive or capacitive loads. For sine‑wave output, the load power factor is typically set between 0.7 and 0.9, with the rated value generally being 0.9. At a given load power, a lower inverter power factor requires larger capacity configuration, increasing cost. Moreover, higher apparent power raises loop current, leading to greater losses and reduced overall system efficiency.

Rated output current and rated output capacity

• Rated output current is the rated current value the inverter can deliver within the specified load power factor range, measured in amperes (A).

• Rated output capacity is the product of rated output voltage and rated output current when the output power factor is 1 (i.e., for pure resistive loads), expressed in kilovolt‑amperes (kVA) or kilowatts (kW).