What is Power energy storage system converter PCS?

PCS Energy storage converters, also known as bidirectional energy storage inverters or PCS (Power Conversion System), are crucial components in AC-coupled energy storage systems such as grid-connected and microgrid energy storage. They bridge the gap between battery banks and the power grid (or load), enabling the bidirectional conversion of electrical energy. These versatile devices can both convert direct current (DC) power from batteries into alternating current (AC) power for use by the grid or AC loads, and also rectify AC power from the grid into DC power for charging batteries.

PCS energy storage converter

Working picture of PCS energy storage

What is the function of PCS energy storage in battery?

PCS, or Power Conditioning Systems, are the intelligent devices that make energy storage systems possible. They are composed of various hardware and software components, including power management, control systems, protection mechanisms, and monitoring functions. These components work together seamlessly to ensure the safe, efficient, and reliable operation of energy storage systems.

PCS energy storage come in two main categories: single-phase and three-phase. Single-phase PCS are typically used in smaller applications, while three-phase PCS are employed in larger, more demanding systems. Both types of PCS play a crucial role in converting direct current (DC) electricity from batteries into usable alternating current (AC) electricity that can power our homes and businesses.

Within the three-phase PCS category, there are two further distinctions: small-power three-phase PCS and large-power three-phase PCS. Small-power PCS utilize a two-stage conversion process, employing both DC-DC and DC-AC conversion stages. On the other hand, large-power three-phase PCS employ a single-stage DC-AC conversion process.

PCS also differ in their isolation methods. High-frequency isolation is commonly used for single-phase and small-power three-phase PCS, while medium-frequency isolation is preferred for PCS between 50kW and 250kW. For PCS exceeding 500kW, non-isolated topologies are typically employed.

These technical details may seem a bit daunting, but they underscore the sophistication and versatility of PCS energy storage system. They are the unsung heroes of energy storage systems, working tirelessly to ensure that we have access to clean, reliable, and sustainable energy.

What are the differences in PCS energy storage features for different application scenes?

Beyond the standard active power regulation capability, PCS energy storage on both the new energy and grid sides typically require additional functionalities. These include inertia support, primary frequency modulation active power support, and reactive power regulation. The latter helps maintain the station's own reactive power balance and provides grid support. As new power systems are built, grid-forming energy storage is gaining traction, with PCS acting as its core equipment. On the user side, integrated photovoltaic and energy storage systems find applications in distributed photovoltaic and storage coupling. Additionally, some user-side energy storage PCS energy storage offer off-grid and on-grid switching functionality, providing emergency support for critical loads.

How to choose the Right Power Converter System (PCS) for Your Energy Storage Needs

Power Conditioning Systems (PCS) play a crucial role in energy storage systems, ensuring the safe, efficient, and reliable conversion of electricity from batteries to usable power. With the wide range of PCS energy storage options available, selecting the right one for your specific needs can seem daunting. However, by understanding the key technical parameters, you can make an informed decision that optimizes your energy storage system's performance.

System Voltage in PCS Energy Storage Systems

System voltage is a crucial aspect of energy storage systems, as it determines the compatibility between batteries and power conditioning systems (PCS). Different PCS technologies employ varying system voltages, ranging from around 50V for single-phase two-stage PCS energy storage to a wider range of 150V to 550V for three-phase two-stage PCS. Three-phase PCS with a high-frequency isolation transformer typically operate at system voltages between 500V and 800V, while those without the transformer operate in the range of 600V to 900V.

Power factor

Power factor represents the ratio of real power (the power that actually does work) to apparent power (the total power drawn from the grid). A high power factor indicates that the PCS energy storage is efficiently converting electricity, minimizing energy losses and reducing electricity bills.

For optimal performance, a power conditioning system (PCS) should maintain a power factor of at least 0.99 during normal operation. When the system is involved in power factor regulation, it should have a wide power factor range to effectively manage and optimize energy consumption.

Switching time

Switching time is a critical aspect of power conditioning systems (PCS) in energy storage systems, as it determines the speed at which the system can switch between different operating modes. Large energy storage systems should have fast switching times to ensure seamless transitions and maintain system stability.

Types of Switching Times:

  1. Charge-Discharge Switching: This refers to the time it takes for the PCS to switch between charging and discharging the batteries. For large energy storage systems, the switching time between 90% rated power grid-connected charging and 90% rated power grid-connected discharging should be no more than 200 milliseconds.

  2. Grid-Connected and Off-Grid Switching: This refers to the time it takes for the PCS energy storage to switch between grid-connected and off-grid modes. The switching time between these modes should be no more than 100 milliseconds.

PCS energy storage converter is like a power housekeeper, it can flexibly switch between two working modes, on-grid mode and off-grid mode, to meet your various needs.

In grid-connected mode:

  • It acts as a bridge between the battery and the power grid, allowing for a seamless flow of energy in both directions.
  • Just like a smart battery charger, it efficiently charges the battery during low-demand periods, storing energy for later use.
  • When the power grid is under stress, it steps up to the plate, converting the stored DC power from the battery back into AC power and feeding it back into the grid, supporting the network.
  • It also acts as a power conditioner, ensuring that the power supplied to the grid meets the required quality standards.

In off-grid mode:

  • It operates independently, becoming an island of power, providing reliable and high-quality AC electricity to your local loads, even when the main grid is unavailable.

What are the 3 types of energy storage systems that work with PCS?

pcs energy storage
  • Energy-type Energy Storage Systems:

Electrochemical energy storage systems, due to their strong ability to store electrical energy, are widely used in fields such as wind and solar energy storage, and independent energy storage. The product characteristics of electrochemical energy storage systems mainly include high energy density, long life, etc., suitable for applications requiring long-term energy storage and release. The main customers are power generation groups, grid groups, and their subsidiaries.

  • Power-type Energy Storage Systems:

Power-type energy storage systems achieve grid frequency stability through rapid power response, which can be combined with conventional power plants such as thermal and hydroelectric power plants to achieve rapid power regulation, thereby improving the frequency regulation performance of power plants. The product characteristics of electrochemical power-type energy storage systems mainly include high power output, rapid response capability, suitable for applications requiring instantaneous high power demand. The main customers are usually investment and operation entities engaged in contract energy management business.

  • User-side Energy Storage Systems:

User-side energy storage systems provide 2-4 hours of energy storage and release ranging from tens to thousands of kilowatt-hours, providing value to customers through peak shaving, emergency backup, dynamic capacity addition, etc. They are used to provide energy storage and regulation on the user side, allowing for flexible energy storage and release according to user needs to balance loads, improve energy utilization efficiency, and enhance power supply reliability. The main customers are usually third-party investment entities or commercial and industrial enterprises.

  • Application Scenarios:

The downstream applications of the energy storage industry can be divided into three main areas: power source side, grid side, and user side. Power source side applications include scenarios such as joint frequency regulation of thermal power units and renewable energy grid integration (i.e., new energy storage with renewable energy); grid-side applications include independent energy storage, substation energy storage, etc., where energy storage systems are used to optimize grid structure, participate in peak shaving and frequency regulation, and improve power quality; user-side applications are mainly used for self-generated electricity, peak-valley price arbitrage, capacity tariff management, and improving power supply reliability.

The three types of energy storage products generally use lithium iron phosphate batteries as energy storage devices, and their thermal management can employ either air cooling or liquid cooling technology. They all achieve energy storage and release through bidirectional power conversion systems (PCS).

The technological paths of the three energy storage products are essentially similar. Initially, all three types used PCS and battery grouping technology with 400Vac on the AC side and no more than 1000Vdc on the DC side, primarily employing air cooling for thermal management.

With technological and industry developments, apart from user-side energy storage, which still mainly utilizes PCS and battery grouping technology with 400Vac on the AC side and no more than 1000Vdc on the DC side, the development of energy-type and power-type energy storage products has transitioned to PCS and battery grouping technology with 690Vac on the AC side and 1500Vdc or lower on the DC side, with a gradual shift towards liquid cooling for thermal management.

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In new power systems dominated by renewable energy, power electronic devices like inverters and PCS energy storage exhibit current source characteristics, meaning they offer fast control but have limited self-protection margins. This significantly impacts the system's fundamental characteristics, including inertia, voltage, frequency, and damping control. Grid-forming technology addresses these challenges by providing short-term overload capacity (e.g., 3 times overload for 10 seconds) and shaping the PCS energy storage port to mimic the voltage source characteristics of a synchronous machine. This ultimately enhances the strength, stability, and controllability of the power grid.

Growing Integrated Energy Storage Density and Matching PCS Power

As the integrated energy density of energy storage systems increases, the power of PCS energy storage is also being boosted to match the capabilities of the battery system. For example, in centralized energy storage, 5MWh+ integrated devices are undergoing iterative upgrades this year. Centralized PCS energy storage will be upgraded from the current mainstream 1.735MW to 2.5MW, and the power of string and cascaded PCS will also see gradual increases.

Rise of Liquid-Cooled PCS Energy Storage

Driven by the growing popularity of liquid-cooled energy storage integrated devices, liquid-cooled PCS energy storage is also experiencing significant development. By sharing liquid cooling units with the battery system while conducting independent heat exchange, this technology can enhance the power and energy density (PCS) of the energy storage system, improve overall efficiency, and provide adaptability to challenging environments like high altitudes, extreme temperatures and humidity, salt fog, and sand dust.

Overview of pcs energy storage

Imagine a microgrid system powered by a mix of energy sources, like solar and wind. These renewable sources, while environmentally friendly, can be unpredictable, and so can the energy demands of the system. Traditional fuel generators can only produce electricity, not store it. This can lead to imbalances if only solar, wind, and fuel generators are used. For instance, if renewable energy output exceeds demand, the system could malfunction. This is where the PCS energy storage converter comes in as a game-changer. Unlike traditional generators, it can both absorb and release energy, and it does so swiftly, ensuring a harmonious balance within the microgrid.

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