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Technical Solution for Energy Storage System

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Technical Solution for Energy Storage System

 

The application of various intermittent and unstable power sources (e.g. wind, PV power) on the generation side, especially those distributed small-capacity power sources, will lead to higher uncertainty of future electric power systems and intensified conflicts on the equilibrium between power generation and consumption. Therefore, feasible solutions to these issues become urgent needs. The Internet of Energy is an effective way to eliminate future conflicts on the equilibrium between power generation and consumption. Its principle is based on the complementation of multiple power sources as well as the coordinated development of power resources, grids, loads and storage. Nowadays, energy storage technology is suitable for all microgrids. More importance has been attached to the research on related technologies.
Through the construction of large-sized efficient energy storage units, a series of issues may be solved, such as the time difference between power generation and consumption, and the impact of intermittent renewable energy-based power generation and direct grid connection on a grid. As a result, the power quality can be regulated. Typical cases: i) the "Peak Power" may be stored in energy storage batteries and used for production and operation during peak hours to reduce grid loads and operating costs; ii) such energy storage system may be used in governments, hospitals, military commands and other critical departments as standby stations to ensure the stable and timely emergency power supply in emergency; and iii) the energy storage system may also support the optimal allocation of resources (fuel, solar and wind power), integration of resources (solar and wind power), grid stability (frequency and voltage) and workload management. These application modes are quite suitable for conventional grids and microgrids. Specific solutions are divided into three categories below:
 

2.1 Energy Storage Solution for Microgrids
As one of the indispensable parts in a microgrid that is a critical application for energy storage, such energy storage system plays an essential role in the microgrid.
With a typical structure shown in Fig. 1 below, the microgrid combines an energy flow of power lines with an information flow of communication lines. It mainly consists of: a distributed power generation unit, energy storage system, local customers' load, monitoring and protection system, and microgrid energy management system. Alternatively, all these systems may be increased or decreased as the case may be.

  
        
Technical Solution for Energy Storage System

  

Technical Solution for Energy Storage System

 

Technical Solution for Energy Storage System

  

2.2 Energy Storage Solutions for Industrial and Commercial Applications
Compared with the microgrid mentioned above, the solutions for industrial and commercial energy storage systems are simpler and focus on the design of such systems.The power conversion system (PCS) is the core of an energy storage system. By virtue of its years of experience in high-power electric and electronic converter technologies, Zhiguang Electric has developed the ZG-PCS series of energy storage converters of voltages from 0.4 kV to 35 kV to satisfy the specific needs on the energy storage market. With improved technologies and capacities, such converters meet most demands for industrial and commercial energy storage.

 

Technical Solution for Energy Storage System

 

Technical Solution for Energy Storage System

 

Technical Solution for Energy Storage System

 

Technical Solution for Energy Storage System

 

 

2.3 Mobile Solutions for Energy Storage

 

 Technical Solution for Energy Storage System

As for the mobile solution for energy storage systems, Li-ion batteries substitute for diesel generators as power units. The Li-ion batteries, PCS, and power distribution unit are integrated on a chassis. Multiple electrical interfaces (for AC output/DC output/fast charge) are available to form a mobile combination between battery system and vehicle. For safety measures, the battery and PCS status monitors, fire alarm and automatic extinguisher are provided. Such mobile system features mobility, large capacity, high-power, remote dispatching, low noise, energy saving, emission reduction, and environmental protection. With a broad range of application prospects, such mobile energy storage system provides reliable and quality power as quickly as possible where temporary power supply is required, such as emergency repair for power, communication equipment maintenance, handling of unexpected events, emergency rescue and disaster relief, military operations and exercises, logistical support, and expansion of distribution networks. It can meet customers' demands for AC power supply and offer solutions for timely recovery of equipment operation.

 

2.4 Core Technology
Zhiguang's energy storage solutions contain multiple core technologies and ensure perfect control and protections. Some of them are unique to Zhiguang's MV and HV direct-linked (transformer-free) energy storage systems.
1) Real-time four-quadrant decoupling and control for active and reactive power
This technology is helpful for the independent control and fast regulation of active and reactive power during the parallel operation of energy storage systems. It can also be utilized to stabilize active power fluctuations and improve power quality quickly and effectively during peak load shifting, peak load and frequency regulation.
2) Stability control of voltage and frequency
This technology is developed for black starts, independent power supply, microgrid voltage support and stable operation of an energy storage system connected to a microgrid in the off-grid mode.
3) Virtual synchronous generator (VSG) and "Droop Control"
This technology can make the coordinated control of multiple equipment possible and satisfy the application request for ultra-large capacity energy storage. It can also achieve the bidirectional, undisturbed and seamless switching between parallel and off-grid operation modes. It is indispensable in order to use an energy storage system as standby and emergency power supply unit.
4) Islanding detection and anti-islanding protection
This technology leads to the automatic rapid detection of grid faults or islanding effects (e.g. power failure) in an energy storage system. Once any islanding effect is detected, the switching of parallel/off-grid operation can be performed according to the settings. Alternatively, the power output of such energy storage system will be stopped for anti-islanding protection. As a result, such system can have more reliable and safer power supply.
5) High/low voltage ride through (HVRT/LVRT)
This technology can: i) improve the adaptability of an energy storage system to voltage fluctuations in its connected power network; ii) reduce potential islanding and decommission cases of such system due to transient voltage fluctuations in that network; and iii) improve the microgrid stability.
6) Phase and interphase SOC equalization of battery clusters
This technology is unique in an energy storage system with a cascaded topological structure. It is applied in MV and HV cascaded power conversion systems for energy storage (ZG-PCS). It solves the issues related to battery consistency to the maximum extent, extends the service life of batteries, and optimizes the operation of such energy storage system.
7) Link redundancy control of PCS
This technology is unique in an energy storage system with a cascaded topological structure. It is applied in MV and HV cascaded power conversion systems for energy storage (ZG-PCS). It can ensure the automatic quick removal of related links and the continuous operation of such energy storage system and improve the system robustness, in case of failure in a power link or the battery cluster connected to such link.
8) Online monitoring for HV/LV isolation and high-speed communication
This technology achieves electrical isolation among HV and LV equipment as well as high-speed communication among numerous equipment (especially with numerous batteries) with a large span of voltage grades (from several volts to over ten thousand volts). It is unique in a system with a cascaded topological structure. It is applicable to MV and HV cascaded power conversion systems for energy storage (ZG-PCS). It meets the demands for advanced applications and realizes the information interaction between the topmost system and lowest-level units.
9) Energy management
 As the superior dispatching and control system of an energy storage system, the energy management system (EMS) provides load and power generation forecasting, system stability control, energy dispatching, superior equalization of battery systems and safety protection.

2015 - 05 - 11
Shenzhen Baoqing Power Plant Project of China Southern Power Grid Company Limited (Energy Storage Project)   The Shenzhen Baoqing Power Plant Project of China Southern Power Grid Company Limited is the domestic first battery energy storage station of the megawatt level. It is located in Longgang District of Shenzhen. It is an industrial energy storage system for the distribution network,...
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