The Difference Between Photovoltaic Inverters And Energy Storage Inverters

With the rapid development of renewable energy, photovoltaic power generation and energy storage have gradually become important components of green energy. For the past 20 years, photovoltaics and energy storage have spread to every corner of cities and rural areas, across different industries. So, as the core components of photovoltaics and energy storage, are inverters the same?

1    Photovoltaic inverter

A photovoltaic inverter is a key device that converts the direct current (DC) generated by photovoltaic modules into alternating current (AC). Due to the fact that the output of photovoltaic power generation systems is direct current, while most power systems and household appliances use alternating current, the role of photovoltaic inverters is to convert direct current into alternating current that meets grid standards.

1. Principle of photovoltaic inverter

The basic principle of a photovoltaic inverter is to periodically reverse switch the DC current through switching elements such as IGBT or MOSFET, and form a stable AC output after filtering, control, and regulation. This process is achieved through an inverter circuit, usually using pulse width modulation (PWM) technology to ensure that the output voltage and frequency meet the requirements of the power grid.

The inverter also includes an MPPT (Maximum Power Point Tracking) controller, which is used to adjust the operating point of the photovoltaic modules in real time, so that the photovoltaic system can always operate at the optimal power output state, thereby improving the system's power generation efficiency. In addition, many inverters now also have functions such as low voltage ride through and islanding protection.

2. Classification of photovoltaic inverters

Classified by structure:

Centralized inverter: suitable for large-scale photovoltaic power plants, it aggregates the DC power of all photovoltaic modules into one inverter for conversion. Centralized inverters have a large capacity and are typically used in large photovoltaic power plants.

String inverter: suitable for small and medium-sized photovoltaic power plants, multiple photovoltaic modules are connected in series, and multiple inverters are used to invert the output of each string separately. String inverters have low cost and flexible installation, making them suitable for distributed photovoltaic systems such as residential and commercial buildings.

Micro inverter: Each photovoltaic module is equipped with a small inverter that can independently convert the DC power of each panel. This method can minimize power generation losses caused by partial shadows or faults, and is suitable for residential photovoltaic power generation.

Classified by working method:

Grid connected inverter: It sends the AC power generated by the photovoltaic system into the public grid, usually meeting the standard requirements of the power grid company, and is suitable for grid connected photovoltaic power generation systems.

Off grid inverter: Used in areas without grid connection, it stores electrical energy through batteries and operates independently.

2    Energy storage inverter

Energy storage inverters are used to convert direct current (DC) stored in batteries into alternating current (AC) and manage the charging and discharging process of batteries. Energy storage inverters and photovoltaic inverters have similarities in functionality, but due to the fact that energy storage systems not only involve grid interfaces, but also factors such as battery management, energy storage inverters need to have more control and management functions.

1. Principle of energy storage inverter

The main principle of an energy storage inverter is to convert the DC power in the battery pack into standard AC power through an inverter circuit. Similar to photovoltaic inverters, energy storage inverters also convert direct current into alternating current through switching elements.

In addition, the energy storage inverter also has a battery management system (BMS), which is responsible for real-time monitoring of battery charging and discharging status, voltage, current, temperature and other parameters to ensure the safety and service life of the battery. At the same time, energy storage inverters can interact with the grid and support bidirectional communication, that is, feedback the electrical energy in the battery to the grid, or charge from the grid when the grid power is insufficient.

2. Classification of energy storage inverters

Grid connected energy storage inverter: suitable for grid connected energy storage systems, capable of outputting stored electrical energy to the grid or providing emergency power in case of grid failure.

Off grid energy storage inverter: used in isolated areas or emergency backup systems to convert the electrical energy in energy storage batteries into alternating current for use in households or devices.

3. Application scenarios of energy storage inverters

Home energy storage system: When used in conjunction with solar photovoltaic systems, home energy storage inverters can convert the stored electrical energy in the battery into AC power for household use, or send the remaining electrical energy to the grid.

Industrial and commercial energy storage system: used to balance power supply and demand, support demand response, and provide power support especially during peak electricity price periods.

Grid energy storage: provides load balancing for the grid, and the grid energy storage system can store electricity during low demand periods and release electricity during peak periods to optimize grid load.

3    Comparison between photovoltaic inverters and energy storage inverters

Although photovoltaic inverters and energy storage inverters are both power electronic devices used for converting direct current to alternating current, they have significant differences in principles, functions, and application scenarios.