Understand the architectural implementation of residential and commercial battery energy storage systems in one article

There are currently four types of energy storage systems - electrochemical energy storage , chemical energy storage , thermal energy storage and mechanical energy storage . Pumped storage hydro (PSH) remains the most mature mechanical energy storage system, covering more than 90% of the world's grid-scale energy storage capacity. However, the installation of such a giant facility has very high geographical requirements.

According to market research from MarketsandMarkets, the global battery energy storage system market size is expected to grow from US$4.4 billion in 2022 to US$15.1 billion in 2027, with a compound annual growth rate of 27.9%. Lithium-ion batteries account for approximately 86% of this market.

Global renewable energy installed capacity

As the most well-known type of electrochemical energy storage system, lithium-ion batteries have high power/high energy density, high round-trip efficiency, small footprint and flexible expansion. Lithium-ion batteries are a relatively mature technology and, after more than three decades of commercial development, have become a reliable and low-cost solution. It can be said that the continued decline in the cost of lithium-ion batteries is effectively accelerating the development of energy storage.

On-grid/off-grid solar inverter systems with batteries offer numerous benefits for residential and commercial use.

energy arbitrage

Four elements to build BESS:

Press and hold to identify the QR code and obtain it with one click

In order to better help engineers complete energy infrastructure design from product selection to solution implementation, ON Semiconductor has launched the e-book "Optical Storage and Charging - Energy Infrastructure Design Reference Book" , which includes ON Semi's Chinese official website Some key technical articles, reference designs, product application guides, etc. on (www.onsemi.cn) will focus on solar photovoltaics , energy storage , fast charging station construction and other parts to explain the challenges of new energy system design and share ON Semiconductor's proven design technology knowledge and high-performance products.

???? There are gifts for downloading????

Download gift: ON Semiconductor will randomly select 30 lucky users from those who download the e-book and give them a JD E-card worth 20 yuan.

????JD Card prizes will be distributed to the winners via email, and ON Semiconductor will announce the list of winners at the end of subsequent tweets.

⏱The event will start from the date of announcement and last until 18:00 on September 30, 2023;

*Please ensure that the personal information submitted is true and valid. ON Semiconductor does not assume any responsibility if you do not receive the prize due to incomplete or incorrect information;

*Participants must be over 18 years old;

*ON Semiconductor reserves the right to interpret this event.

PCS is an important part of the energy storage system and controls bidirectional power conversion. In a similar trend to other high-power energy infrastructure applications, higher power is always desired in order to match high growth rates in electricity demand, whether of residential or commercial type. At the same time, the smaller size can significantly reduce costs during transportation and installation. Additionally, mass production of wide-bandgap semiconductor components like silicon carbide can bring system efficiency and thermal performance to a new level. Energy storage systems are currently divided into two methods , AC coupling or DC coupling and power stage.

AC coupling and DC coupling

An AC coupled energy storage system is a stand-alone system that can be added to an existing solar/energy generation system. This is a simple upgrade, however, it will involve additional power conversion steps to charge/discharge the battery, which means more power loss. DC coupled systems, or we can call them hybrid (solar) inverters, require only one step of power conversion, but must be designed from the beginning.

Residential AC Coupled ESS (Gray Block)

Residential DC Coupled ESS (Gray Block)

Residential battery energy storage system

Residential inverters are either added to an existing solar inverter system or designed together with a solar inverter as a hybrid inverter. The stored energy can be used to charge backup batteries or to charge electric vehicles and home appliances to save costs.

A bidirectional DC-DC converter is connected between the battery pack and the DC link. In terms of safety and use cases, the bus voltage of a single-phase system is usually less than 600V, and the charge and discharge power will not exceed 10kW. Buck-boost is the most common bidirectional DC-DC configuration and has the advantages of fewer components and easy control. A 650VIGBT/MOSFET using two parallel diodes with good IF values ​​is sufficient for this bidirectional system.

Bidirectional DC-DC buck-boost configuration

FGH4L75T65MQDC50 is a newly released 650V FS4 IGBT that integrates SC diodes to provide excellent performance for high-efficiency applications with low conduction and switching losses.

Isolation is also another aspect to consider when considering battery safety. Dual Active Bridge Converter (DAB) or CLLC has become a common solution for isolated bidirectional DC-DC converters in the EV and ESS sectors. The use of a cascaded front-end buck-boost circuit can achieve a wide range of electronic music input/output when the battery voltage changes, while reducing reactive power circulation and expanding the soft switching area.

Dual active bridge DC-DC converter

Three-phase power is often seen as a common way of supplying electricity in commercial use cases, but these days, this technology has become more reliable and can be used in homes with higher power needs. To handle powers up to 15kW, and DC link voltages that may approach 1000V, the switches should be able to withstand higher operating voltages and currents.

This problem can be easily solved by replacing the 650V switch with a 1200V series. You can also consider a three-level symmetrical buck-boost. This three-level configuration provides smaller switching losses because only half the output voltage is applied to the switch and diode, a feature that helps reduce the inductor and achieve better EMI performance. However, doubling the number of components will inevitably increase the complexity of the bill of materials, difficulty of control, and overall cost.

Symmetric buck-boost converter

Commercial battery energy storage system

The input/output power of commercial energy storage systems ranges from 100 kW to 2MW, and such giant systems usually consist of three-phase subsystems ranging from tens of kW to more than 100 kW.

One of the important specifications is the maximum DC voltage, which depends on the bus voltage or battery voltage of the existing solar system. Common DC bus voltages for commercial solar inverters are 1100V and 1500V, sometimes used in utility-scale systems. A clear trend in this type of application is to increase the DC bus voltage, which helps reduce interconnect cable costs for a given power because the current is lower.

AC coupled systems are more common in energy storage projects because it can be added to an already built system. In addition, centralized energy storage units are easier to manage and place. In contrast, DC-coupled systems require more space and cost to handle distributed battery packs.

Three-level I-NPC is one of the common topologies in high-power industrial applications, especially in inverters. It has 4 switches, 4 reverse diodes and 2 clamping diodes, and the breakdown voltage is lower than the actual DC bus Voltage, for example a 650 V switch is sufficient in a 1100 V system.

Three-phase I-NPC

Two-level and three-level switching principles

There are three advantages to using a three-level topology. First, switching losses are lower. Generally, switching losses are proportional to the square of the voltage applied to the switch and diode. In a three-level topology, only half of the total output voltage is applied to some switches or some diodes . Secondly, the current ripple in the boost inductor becomes smaller. For the same inductance value, the peak-to-peak voltage applied to the inductor is also half the total output voltage in a three-level topology. This makes the current ripple smaller and easier to filter with a smaller inductor, allowing for a more compact inductor design and lower cost. Finally, EMI is reduced, whereas conducted EMI is primarily related to current ripple. As just mentioned, the three-level topology reduces current ripple, making filtering easier and producing lower conducted EMI. At the same time, it also has benefits in terms of electromagnetic radiation.

As an upgraded version, the A-NPC system offers higher performance because the two clamping diodes are replaced by two active switches, with clear advantages in terms of losses. But drive pairing and latency matching are critical and can be seen as a drawback.

Three-phase A-NPC