Power Conversion System (PCS), as a key equipment in energy storage systems, can be divided into three categories based on different application scenarios: large storage PCS, industrial and commercial storage PCS, and household storage PCS. There are significant differences among these three types of PCS in terms of power scale, application scenarios, technical requirements, and cost price.
1. Large storage PCS
Power level: The power level of large storage PCS is usually high, reaching MW level, and even up to 100MW or more. This type of PCS is suitable for large energy storage power plants and can handle large-scale energy conversion needs.
Conversion efficiency: The requirements are extremely high, generally maintaining a conversion efficiency of over 95% to reduce energy loss and improve the economy of energy storage systems.
Response speed: With fast response capability, it can adjust the charging and discharging power within milliseconds to ensure the stability of the power grid.
System compatibility: It is well compatible with large-scale energy storage battery systems and complex power grids, adapting to various battery characteristics and grid access requirements.
Example:
Power range: 10MW-100MW
Efficiency: ≥ 95%
Response time:< 10ms
Input voltage range: 700VDC -1500VDC
Output voltage level: 35kV or higher
Mean Time Between Failures (MTBF):> 100000 hours
2. Industrial and commercial storage PCS
Power range: The power is generally between tens of kW and several MW, suitable for industrial and commercial user scenarios.
Reliability: With high reliability, it aims to reduce downtime due to failures, meet the needs of continuous production or operation, and has a longer average time between failures.
Functional characteristics: Compared with large storage PCS, its functions are relatively simple, but more adaptable; Some products also integrate BMS (Battery Management System) functionality. In addition, it also has certain grid support functions, such as primary frequency regulation and rapid dispatch of source grid loads.
Example:
Power range: 50kW -2MW
Efficiency: 90% -94%
Response time:< 20ms
Input voltage range: 500VDC -800VDC
Output voltage level: 400VAC/690VAC
MTBF：> 50000 hours
3. Household storage PCS
Power scale: The power is relatively small, usually between a few kW and a dozen kW, mainly used for household photovoltaic energy storage and emergency power supply.
Safety: Emphasize safety performance, equipped with a comprehensive battery management system to prevent overcharging, overdischarging, short circuits, and other situations, ensuring the safety of household users.
Usability: Easy to operate, easy to maintain, with an intuitive user interface, easy to install and integrate into home power systems.
Example:
Power range: 3kW-15kW
Efficiency: 85% -92%
Response time:< 50ms
Input voltage range: 200VDC -500VDC
Output voltage level: 230VAC
MTBF：> 30000 hours
For PCS in three different application scenarios of large storage, industrial and commercial storage, and household storage, they adopt similar but different strategies and technical means when dealing with abnormal situations such as overcharging, overdischarging, and short circuits.
1. Overcharge protection
Large scale energy storage: Due to the use of energy type batteries in large energy storage power plants and the need to provide power auxiliary services, the requirements for battery management systems (BMS) are very high. The BMS will continuously monitor the status information of each battery unit. Once it detects that a battery unit is approaching a fully charged state or the voltage exceeds the set threshold, it will immediately stop charging the battery unit through PCS and issue an alarm to notify the operator to check the problem. In addition, some advanced PCS also support SOC balancing control function, which to some extent avoids the occurrence of overcharging caused by uneven charging of individual battery cells.
Industrial and commercial energy storage: The BMS in industrial and commercial energy storage systems also provides overcharge protection mechanisms to ensure that overcharging does not damage battery life or cause safety accidents. When PCS receives the overcharge signal sent by BMS, it will quickly adjust its working mode, such as reducing input power until the power input is completely cut off to prevent further charging.
Household storage: Security is particularly important for household users. Therefore, the household storage PCS not only has strict overcharge protection logic built-in, but also often combines intelligent algorithms to optimize the charging process, ensuring effective prevention of overcharge risks even in unmanned situations. If overcharging occurs, PCS will automatically stop charging and upload relevant alarm information to the cloud platform for users to view.
2. Overdischarge protection
Large storage: In order to ensure stable output of electrical energy from energy storage stations over a long period of time, it is necessary to strictly control the minimum allowable discharge depth of the battery. BMS will monitor the overall State of Charge (SOC) of the battery pack in real-time based on preset parameters, and trigger PCS to perform corresponding protective actions before SOC drops to a critical value, such as limiting discharge power or even suspending discharge operations, until SOC returns to a safe range.
Industrial and commercial energy storage: Industrial and commercial energy storage systems also have similar over discharge protection measures, but considering the frequent charging and discharging cycles in practical applications, some high-end products will introduce more refined management strategies, such as dynamically adjusting SOC upper and lower limits, implementing capacity calibration, etc., in order to better maintain battery health.
Household storage: Household storage PCS also attach great importance to over discharge protection, especially in home environments that rely on energy storage for power supply under low light conditions at night. It can accurately determine when to terminate the discharge process and achieve the goal of prioritizing the use of clean energy during the day through linkage with the photovoltaic system, reducing the possibility of deep discharge at night.
3. Short circuit protection
Large scale energy storage: Given the complex electrical connection structure within large energy storage power plants, any short circuit fault can have serious consequences. Therefore, PCS design pays special attention to enhancing its own short-circuit resistance, including but not limited to configuring high-performance fuses, fast circuit breakers, and other hardware facilities; At the same time, in conjunction with software level security control programs, it is possible to identify and isolate faulty areas in a very short period of time, minimizing losses to the greatest extent possible.
Industrial and commercial energy storage: Industrial and commercial energy storage systems also face the risk of short circuits, especially when multiple PCS are running in parallel. To solve this problem, in addition to conventional fuses and circuit breakers, modern PCS also adopt more intelligent methods for short-circuit protection, such as using current sensors to quickly capture abnormal fluctuations and respond in a timely manner through built-in protection circuits, such as closing output channels and activating emergency cooling devices.
Household storage: For household storage, considering the dispersed installation environment and limited user expertise, the PCS was designed with ease of use and reliability in mind from the beginning. In addition to basic short-circuit protection functions, many products also integrate redundant designs such as double-layer fuses and multiple grounding protections to ensure maximum protection of users' personal and property safety even in the event of unexpected situations.