Detailed explanation of nine parameters of energy storage inverter[Copy link]
Preface
In energy storage projects, key equipment such as inverters and batteries constitute the core units of the system.
This article will provide a detailed introduction to the parameters, application forms, and configuration methods of energy storage inverters, including single-phase energy storage, three-phase energy storage, and energy storage converters (DC coupling, AC coupling) .
Warm reminder: This article is informative, and the detailed parameter explanation involves nine categories: DC input parameters, battery parameters, output parameters (grid-connected), output parameters (off-grid), communication conditions, basic parameters, inverter protection, inverter efficiency, regulations and standards.
1. Why choose to install an energy storage inverter?
Increase the proportion of self-use. During the day, the electricity generated by photovoltaics is used by the load, and the excess electricity is stored in the battery; at night, the photovoltaics do not generate electricity, and the battery electricity is used by the load, achieving the purpose of not using the grid or using less grid electricity.
When the power grid is out or unstable, it can automatically switch to battery power mode. The switching time is very short (UPS effect) and the load can continue to be used.
The effect of bidirectional energy storage - photovoltaics can charge batteries, and the same power from the grid can also charge batteries (when electricity rates are lower); in this way, batteries can be used to adjust the price difference between peak and valley electricity or used as a backup power source.
It can also be used in pure off-grid conditions to drive loads of a certain power.
2. Technical parameters of energy storage inverter
Take the most commonly used single-phase energy storage model as an example.
Interpretation: There are 2 input strings and 2 MPP tracking channels on the DC side of the energy storage machine. The maximum input current of each string is 11A, the maximum input voltage is 580V, and the MPPT operating voltage range is 125~550V. When designing the number of strings, it is necessary to consider that the open-circuit voltage of the string should not exceed 580V (considering the site's extreme temperature), the operating voltage is between 125~550V, and the recommended rated operating voltage is 360V; if a 285W board is used, it is recommended to use 20~22 pieces, and the component capacity is preferably 5.70~6.27kWp).
The battery voltage is 48V (rated voltage). If the user uses a lead-acid battery with a voltage of 2V, 12V, etc., a voltage of 48V can be obtained by connecting multiple batteries in series.
The capacity of the battery is related to the number of batteries and the ampere-hours of a single battery. When choosing the battery capacity, you must make a reasonable selection. The most common method is to calculate the battery capacity based on the load size and power usage duration on the user side. If the load is relatively large or the power usage situation is complicated, you can consider the 1-2 days photovoltaic power generation capacity of the energy storage machine to configure the battery.
The selection of batteries generally needs to consider factors such as battery life, discharge depth, and number of cycles. Lead-acid batteries are relatively cheap, but the battery life is relatively short, the DOD depth is low, and the charge and discharge of lead-acid battery packs are not managed by the BMS protocol, which leads to inconsistencies and possible battery bulging. Therefore, they are not recommended. Lithium batteries are more expensive, but because they are managed by the BMS protocol for charge and discharge, they generally have a longer life. GoodWe energy storage machines are compatible with lithium battery manufacturers such as BYD, LG, and ZTE Payne.
Battery wiring: The charging and discharging current of ES battery input can reach DC 100A. Considering the parameters from battery to inverter, 25mm DC cable is generally used.
The energy storage inverter has two output terminals:
One is the grid-connected output terminal, also called the on-grid terminal;
Another off-grid output terminal is also called the back-up output terminal.
The grid-connected output terminal must be connected to the grid to have output. A load can be connected between the grid-connected terminal and the grid, which is called the grid-connected load.
When the grid is out of power, these loads cannot work (anti-islanding protection). When the grid has power, photovoltaic power will be used first for the loads. When photovoltaic power is insufficient, the grid will supplement it. There is no limit on the capacity of the loads.
As for the off-grid output end (back-up output end) , the output voltage of the back-up end is 220/230V, and it can only connect to loads. Common loads can be connected. The load power is limited by the inverter power. Generally, the maximum output of the off-grid end of a 5kW (GW5048D-ES) inverter does not exceed 4.6kW, and the single inductive load does not exceed 1.5kW, and the total inductive load does not exceed 2.5kW.
At the same time, the following matters must be noted: the off-grid terminal cannot be connected to the grid terminal. The off-grid terminals of multiple energy storage machines cannot be connected together.
In standby mode, the back-up is powered by the grid. If there is a sudden power outage, it will automatically switch to battery power. The off-grid switching time is less than 10ms , which is the UPS-level response time and is an uninterruptible power supply. The energy storage inverters of many inverter manufacturers are EPS, which are emergency power supplies , and the switching time is only less than 5s.
1. Connect to BMS protocol communication. The inverter comes with a 3m communication cable, and the default is CAN communication.
2 is the DRED interface, required by the Australian power grid;
3 is RS485 interface, which can be used for third-party monitoring;
4 is a reserved interface.
The WiFi module can realize local configuration. The inverter has no buttons and display screen. You need to connect to the solar-wifi of the inverter through a mobile phone APP or tablet to set the relevant working mode. At the same time, WiFi can also realize remote monitoring like a grid-connected machine.
The Ezmeter port is connected to the Ezmeter meter, the cable length is 10m, provided by GoodWe. The meter communication is RS485 communication. The Ezmeter meter can monitor the local load and can also realize the function of anti-backflow (not sending electricity to the grid).
Installation method—Wall-mounted, including back plate.
Protection level——IP65 (can be installed outdoors)
Human-computer interaction—LED lights, APP control, there are 8 LEDs on the inverter, representing SYSTEM, BACK-UP, SOLAR, BATTERY, GRID, ENERGY, WIFI, FAULT, and the meaning of each light is as follows:
Interpretation: The efficiency of the inverter is very important. At the same time, the stability, protection, electromagnetic interference capability, output voltage redundancy, short-time overload capability and harmonic resonance of the inverter are also very important. For this reason, the country or industry has formulated relevant regulations and standards, such as Article ③.
Interpretation: To connect the inverter to the local power grid, it must comply with the local grid connection standards, safety standards and EMC standards. At present, there are no standards for energy storage in China, and the grid connection standards are not applicable to energy storage inverters. We look forward to the early arrival of regulations and subsidies for energy storage.
Summarize
The technical parameters of the energy storage inverter are the most direct reflection of the inverter's performance and application methods. The above content provides a detailed introduction to the parameters of the energy storage inverter. In the future, Xiao Gu will have the opportunity to conduct a more detailed analysis of some special content. You are also welcome to put forward your understanding of the technical parameters of the energy storage inverter, or the energy storage products or technologies you want.
Reposted from: Official Account: GoodWe Photovoltaic Community
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