Ultracapacitor + Lithium-Ion Hybrid Energy Storage System for Thermal Power Auxiliary Power Stabilization

1. Application Background

Thermal power plants rely heavily on large auxiliary equipment such as induced draft fans, forced draft fans, feed water pumps, coal mills and circulating water pumps. Frequent equipment startup and shutdown, fluctuating operating loads, unit switching, AGC frequency regulation and deep peak shaving often cause severe transient disturbances on auxiliary power buses. Common power quality issues include voltage sag, frequency drift, voltage flicker and three-phase unbalance, which continuously threaten the stability of on-site power consumption systems.

Traditional power regulation methods have obvious technical limitations. Mechanical speed regulation responds slowly and cannot handle fast fluctuations. Single lithium-ion energy storage struggles with high-frequency micro-cycle impacts and tends to degrade rapidly under frequent transient load changes. Conventional reactive power compensation devices only improve power factor and cannot resolve instantaneous power shortages or voltage instability. These shortcomings make traditional solutions insufficient for modern thermal power stability requirements.

Uncontrolled auxiliary power disturbances may lead to variable-frequency trip events, equipment shutdowns and unstable operating parameters. In severe cases, they cause boiler combustion fluctuations, unit instability and unplanned outages, resulting in reduced power generation efficiency, increased operational risks and higher maintenance costs.

To address the frequent, random and multi-timescale power fluctuations of thermal power auxiliary systems, our hybrid energy storage solution integrates ultracapacitor and lithium-ion technology. It combines fast transient response and long-duration steady-state power support to achieve full-condition power stabilization and reliable plant operation.

2. System Architecture and Working Principle

This hybrid energy storage system adopts a dual-storage architecture combining power-grade ultracapacitors and energy-grade lithium-ion batteries. The complete package includes bidirectional PCS converters, intelligent EMS energy management system, local measurement and protection units, and integrated cabinet equipment. Through real-time monitoring and hierarchical power distribution, the system precisely handles both transient and steady-state grid disturbances.

Ultracapacitor Module – Transient Disturbance SuppressionWith millisecond-level response, ultra-long cycle life and extremely low attenuation characteristics, ultracapacitors independently absorb high-frequency minor fluctuations, instantaneous startup shocks and millisecond-level voltage sags. They provide rapid power injection and absorption to stabilize transient deviations that conventional devices cannot handle.

Lithium-Ion Battery Module – Steady-State Power SupportLithium-ion batteries offer high energy density and continuous discharge capability. They provide sustained power compensation for medium and long-term load deviations, deep peak-shaving power gaps and steady voltage drift, making up for the limited energy capacity of ultracapacitors.

Intelligent EMS Cooperative Control StrategyThe self-developed EMS collects real-time bus voltage, frequency and load data to identify disturbance characteristics automatically. High-frequency transient fluctuations are smoothed by ultracapacitors to avoid unnecessary battery cycling, while continuous power deviations are handled by lithium batteries with fine ultracapacitor auxiliary regulation. This dual-layer control ensures high-precision dynamic stabilization and effectively reduces battery degradation, extending the overall system service life.

3. Core Functions

3.1 High-Precision Bus Stabilization and Voltage Sag Resistance

The system delivers millisecond-level power compensation during sudden load changes caused by frequent startup and shutdown of coal mills, fans and water pumps. It rapidly fills transient power gaps and maintains voltage and frequency within standard ranges, effectively preventing VFD tripping, equipment outage and parameter fluctuation, ensuring stable boiler combustion and consistent unit power output.

3.2 Full-Condition Power Quality Optimization

Adapted for deep peak shaving, AGC frequency regulation and large load fluctuation scenarios, the system suppresses voltage flicker, frequency offset and three-phase unbalance. It significantly improves overall power quality, reduces grid assessment errors and enhances unit regulation performance and auxiliary service benefits.

3.3 Service Life Extension and Low Operation Cost

By separating high-frequency transient impact loads and steady-state baseline loads, the system protects lithium-ion batteries from invalid micro-cycles and reduces internal polarization accumulation. This optimized operating strategy extends the effective battery service life by 2–3 times, lowers system failure rates and minimizes routine maintenance workload, meeting long-term low-maintenance operational requirements of thermal power plants.

3.4 Fault Ride-Through and Condition Transition Support

During sudden load mutations and short-term grid anomalies, the hybrid system provides fast power backup to buffer unit adjustment and protection action time. It effectively avoids unit oscillation and unplanned shutdown risks, improving overall power supply reliability and system fault tolerance.

4. Core Advantages

4.1 Dual-Energy Complementation for Full-Condition AdaptabilitySingle lithium storage lacks fast response and high-frequency impact resistance, while single ultracapacitor storage cannot support long-duration energy compensation. The hybrid solution integrates the strengths of both technologies, achieving millisecond-level dynamic response and steady-state power support to cover all transient, short-term and stable operating conditions of thermal power units.

4.2 Multi-Level Protection and High Operational SafetyUltracapacitors feature excellent thermal stability, zero thermal runaway risk and strong shock resistance for 24/7 continuous operation. Lithium-ion batteries are equipped with complete BMS monitoring, overcharge/over-discharge protection, short-circuit protection, temperature monitoring and fire suppression systems. The overall multi-protection design ensures high safety and stability for unattended industrial power scenarios.

4.3 Superior Full-Lifecycle EconomyUltracapacitors support millions of cycles and decade-level stable operation. Optimized battery operating conditions greatly reduce degradation and replacement frequency. Compared with single lithium energy storage solutions, the hybrid system delivers lower long-term maintenance costs and higher comprehensive economic benefits.

4.4 Compact Integration and Flexible DeploymentThe fully integrated cabinet design features compact structure, small footprint and convenient maintenance. It can be directly connected to 6kV/400V auxiliary buses without major modification of existing electrical systems, suitable for new plant construction and old plant upgrading projects.

5. Typical Application Scenarios

• Auxiliary bus voltage stabilization and anti-sag treatment for 6kV/400V power systems

• Power quality optimization during deep peak shaving and AGC frequency regulation

• Anti-disturbance protection for frequent startup and shutdown of large auxiliary equipment

• Comprehensive management of voltage flicker and frequency deviation caused by violent load fluctuations

• Reliability upgrading and power quality renovation for existing thermal power plants

6. Solution Value

Our ultracapacitor and lithium-ion hybrid energy storage system effectively solves the common problems of slow response, insufficient disturbance suppression, rapid equipment aging and high maintenance costs in traditional thermal power auxiliary power systems. Through dual-storage complementary coordination and intelligent hierarchical regulation, the system realizes fast transient stabilization, steady-state power optimization, equipment life extension and operational safety enhancement. It helps thermal power plants achieve stable power generation, operational efficiency improvement and lifecycle cost reduction, serving as an ideal high-performance power quality solution for modern thermal power enterprises.