How to Choose the Ideal Solar Inverter: A Step-by-Step Approach

Firstly, it is essential to have a basic understanding of solar inverters.

A solar inverter is a device that converts direct current (DC) power from batteries or storage batteries into alternating current (AC) with a fixed frequency and voltage, typically a 220V, 50Hz sine wave. It consists of three main components: an inverter bridge, control logic, and a filter circuit.

The working principle of solar inverters involves transforming DC power into AC power through a process known as voltage inversion. This conversion is achieved by utilizing a converter, which transforms the AC voltage from the grid into a stable 12V DC output. Subsequently, the inverter takes this 12V DC voltage output from the converter and converts it into high-frequency, high-voltage AC power. Both the converter and inverter employ pulse width modulation (PWM) technology, which is commonly used in such applications.

The pivotal component of this system is the PWM integrated controller, with the UC3842 chip being utilized in the converter and the TL5001 chip in the inverter. The TL5001 chip operates within a voltage range of 3.6 to 40V and incorporates various features such as an error amplifier, regulator, oscillator, deadband control of the PWM generator, low-voltage protection circuit, and short-circuit protection circuit.

The categorization of solar inverters

1. Centralized Inverter

Centralized inverter technology involves connecting multiple parallel PV strings to the DC input of a single centralized inverter. Typically, large power systems utilize three-phase IGBT power modules, while smaller power systems employ field effect transistors. These inverters incorporate DSP conversion controllers to enhance the quality of the output power, ensuring it closely resembles a sinusoidal current. Centralized inverters are commonly used in large-scale PV power plants (>10kW). The key advantage lies in their high power capacity and cost-effectiveness. However, due to the mismatch in output voltages and currents among different PV strings (especially when partial shading occurs due to cloudy conditions, shade, stains, etc.), the use of centralized inverters can lead to reduced efficiency in the conversion process and decreased energy output. Additionally, the poor performance of a particular PV unit group can impact the overall power generation reliability of the entire PV system. To address these challenges, ongoing research focuses on employing modulation control using space vectors and developing new topological connections of inverters to achieve high efficiency even in partial load situations.

2. String Inverter

String inverters are widely adopted in the international market due to their modular design. Each PV string (1-5kw) is connected to an inverter that incorporates maximum power peak tracking at the DC end. This allows for parallel connection to the grid at the AC end, making it the most favored inverter type nowadays.

String inverters are extensively used in large-scale PV power plants. One of their key advantages is their ability to mitigate the impact of module differences and shading between strings. By reducing the mismatch between the optimal operating point of PV modules and the inverter, they enhance power generation. This not only lowers the system cost but also enhances system reliability. Moreover, the introduction of the "master-slave" concept enables the linking of multiple groups of PV strings. This allows for the operation of one or more strings, thereby maximizing power generation even if a single string is incapable of operating a single inverter.

3. Microinverter

In a conventional PV system, the DC input of each string inverter is connected to approximately 10 PV panels in series. However, if one of these panels malfunctions, the entire string is affected. Furthermore, if the inverter employs the same maximum power point tracking (MPPT) for multiple inputs, all inputs will suffer, leading to a significant reduction in power generation efficiency. In a microinverter photovoltaic (PV) system, each individual panel is connected to its own microinverter. This design ensures that if one panel is not performing optimally, only that specific panel will be affected. The rest of the PV panels will continue to operate at their peak efficiency, resulting in a higher overall system efficiency and increased power generation. In contrast, when a string inverter fails, it can cause several kilowatts of panels to cease functioning, whereas the impact of a microinverter failure is relatively minor. This highlights the superiority of microinverters in terms of reliability and performance in real-world applications.

Secondly, it is crucial for solar systems to utilize solar inverters.

As the essential power conversion equipment in a photovoltaic power station, the inverter plays a pivotal role. It is a power electronic device that converts the low-voltage DC power generated by the solar modules into AC power. This AC power can be connected to the load or integrated into the power grid, making the inverter the core device in the entire photovoltaic system.

The solar inverter not only facilitates direct AC conversion but also maximizes the performance of the solar cells and ensures system failure protection. It encompasses various functions, including automatic operation and shutdown, maximum power tracking control, anti-individual operation (specifically for grid-connected systems), automatic voltage adjustment (for grid-connected systems), DC detection (for grid-connected systems), and DC grounding detection (for grid-connected systems).

To summarize, the solar inverter is a versatile device that not only converts DC power to AC power but also enhances the efficiency of solar cells while safeguarding the system against potential failures. Its wide range of functions ensures seamless operation, optimal power utilization, and reliable performance in grid-connected systems.

Last, how to select the appropriate solar inverters for your system?

1. It is crucial to ensure that the voltage and current of the solar inverters match the existing PV modules. This ensures the optimal utilization of the power generated by the system.

2. The solar inverters should have a modular design and expandable interface options to facilitate future system upgrades and expansion. This allows for seamless integration of additional components as your system grows.

3. The rated output power of the inverter should be appropriately matched to the installed capacity. Typically, it is recommended to over-match the rated output power by 1.1-1.2 times to ensure efficient operation.

4. It is important to consider the output voltage regulation performance of the inverters. This ensures a stable output voltage, which is essential for the smooth functioning of the entire system.

5. The overall efficiency and starting performance of the inverters should be taken into account. Higher efficiency ensures maximum power conversion, while reliable starting performance guarantees consistent operation.

In conclusion, PV inverters play a vital role in the performance of your PV system. Selecting the right inverter and utilizing it correctly can greatly enhance the gains of your PV system. If you require assistance in choosing an inverter, please do not hesitate to reach out to our sales team. They will gladly recommend the most suitable inverter for your specific requirements.