• Dagong ESS

What Are the Differences Between Centralized and String-Type ESS in Parallel C&I Projects?

What Is a Centralized ESS Architecture?

A centralized C&I ESS integrates battery modules into one large DC bus and uses a single high-power PCS (power conversion system) to handle energy conversion. In parallel projects, multiple battery cabinets share the same PCS, and the control system manages charge/discharge tasks collectively.

Key Characteristics

• One PCS, multiple battery packs

• Unified BMS/EMS scheduling

• Lower PCS redundancy but higher power density

• Simplified grid connection point

• Typical in industrial peak-shaving projects

Centralized designs are commonly used in large-capacity C&I systems such as 215–241kWh air-cooled ESS or 372kWh liquid-cooled cabinets operating as part of a shared power block.

What Is a String-Type ESS Architecture?

A string-type ESS equips each battery module or cabinet with its own PCS or smaller PCS units, allowing each unit to run independently. When parallel operation is required, each string communicates with the EMS through distributed control logic.

Key Characteristics

• PCS per cabinet or per module

• High redundancy and high operational flexibility

• Independent MPPT-like operation for each string

• Easily scalable by adding more cabinets

• Lower fault impact on overall system

String-type designs are increasingly popular in distributed C&I projects and microgrids, especially with modular systems similar to 100–144kWh air-cooled ESS units.

Key Differences Between Centralized and String-Type ESS in Parallel Applications

1. System Architecture

Item	Centralized ESS	String-Type ESS
PCS Structure	One large PCS	Many smaller PCS units
Battery Topology	Shared DC bus	Independent DC strings
Redundancy	Low	High
Failure Impact	A single PCS fault affects whole system	Only one string affected

Best Use Case

• Centralized → large industrial power blocks

• String-type → flexible, modular deployments

2. Control Logic & EMS Interaction

Centralized ESS uses one centralized control unit, simplifying scheduling but reducing independence.

String-type ESS uses distributed PCS control, giving each cabinet autonomous decision-making for charging/discharging, similar to PV string inverters.

Result:

• Centralized → easier integration but lower adaptability

• String-type → higher precision and better balancing between strings

3. Parallel Operation Characteristics

Parallel operation in C&I ESS must consider current balancing, power sharing, and voltage stability.

Centralized Parallel

• Parallel only at the DC or battery cabinet level

• PCS handles all power balancing

• More sensitive to SOC and resistance differences

• Requires strict uniformity among battery packs

String-Type Parallel

• Each PCS controls its own current

• No risk of DC bus imbalance

• Compatible with different capacities or aging conditions

• Supports smoother expansion

This is why string-type ESS is often chosen for expansion projects or sites that expect gradual capacity increases.

4. Installation & Commissioning

Centralized ESS:

• Faster centralized wiring

• Requires heavy PCS installation

• Commissioning is more complex due to high-power PCS

String-type ESS:

• More cables but lighter equipment

• Each PCS auto-configures

• Faster commissioning for modular C&I ESS

5. Operation & Maintenance Costs

Centralized ESS O&M

• Lower PCS count = lower maintenance cost

• PCS failure causes large system downtime

• Requires more specialized technicians

String-Type ESS O&M

• Multiple PCS units require more inspection

• PCS failure is isolated—system keeps operating

• Easier troubleshooting and hot-swapping

6. Safety & Fault Isolation

Centralized:
A failure in PCS or DC bus can impact multiple battery groups.

String-type:
Each string can be fully isolated by contactors, improving safety performance. This is compatible with liquid-cooled systems like 215kWh or 372kWh systems where module-level protection is critical.

Application Scenarios in Real C&I Projects

Centralized ESS is ideal for:

• Industrial parks with stable load patterns

• Manufacturing peak shaving

• Utility-connected power blocks

• Sites requiring higher instantaneous power

String-Type ESS is ideal for:

• Retail & commercial buildings

• Industrial users requiring redundancy

• Southeast Asia microgrids

• European sites with strict grid compliance

• North American modular ESS projects requiring scalability

In many export markets, parallel string-type ESS is favored because of easier installation, better unit independence, and simpler compliance with local grid regulations.

Why Both Architectures Matter in Global ESS Export Projects?

Different markets show different trends:

Europe

• Strong preference for modular, string-type systems

• EU grid codes require high fault tolerance

North America

• Hybrid models common

• Liquid-cooled centralized blocks used for utility-scale systems

Southeast Asia

• Microgrids prefer string-type

• Rapid load growth makes scalable systems valuable

Manufacturers offering both air-cooled and liquid-cooled ESS solutions—such as 100–144kWh modular air-cooled units, 215–241kWh C&I systems, and 372kWh liquid-cooled modules—are well positioned to support these distinct market needs.

Price Factors for Centralized vs String-Type ESS

Price differences depend on:

• PCS quantity

• Cooling system (air vs liquid)

• Battery capacity and type (LFP preferred)

• Communication topology

• Installation labor

• Local grid certification requirements

For international projects, buyers typically request a full technical proposal before pricing because costs vary by country, certification, and configuration.

How Long Do These Systems Last?

Both centralized and string-type ESS using high-quality LFP batteries generally deliver:

• 8000+ cycles

• 15+ years service life

• Lower degradation in liquid-cooled designs

• Long-term reliability in high-temperature environments

Conclusion

In parallel C&I storage projects, centralized and string-type ESS architectures each offer unique advantages:

Centralized = high power density, unified management

String-type = strong redundancy, flexible deployment, easier expansion

As global demand rises in Europe, North America, and Southeast Asia, both structures will continue playing important roles in peak shaving, energy shifting, microgrids, and industrial energy optimization.

If you are interested in centralized or string-type ESS solutions, feel free to contact Dagong ESS at sales@dagongess.com.