In today's rapidly increasing proportion of new energy generation, the power system is facing challenges brought by the "dual high" (high proportion of renewable energy and high proportion of power electronic equipment), such as low inertia, low damping, weak voltage support, and other issues. The emergence of grid based energy storage technology provides new ideas for solving these problems. So, what exactly is grid based energy storage technology? What are the differences between it and traditional grid based energy storage technology?
1 Definition of grid based energy storage technology and grid following energy storage technology
1. Network construction technology
Grid construction technology is an advanced energy storage technology that enables energy storage systems to actively support the power grid through specific control strategies. The core lies in embedding the control principle of synchronous generators into energy storage inverters, allowing the inverters to autonomously generate stable voltage and frequency signals like traditional synchronous generators, thus building a stable power grid even without an external power grid. This energy storage system is essentially a voltage source that can internally set voltage parameters and output stable voltage and frequency. It can operate both grid connected and off grid, and has strong support for the power grid.
2. Network based technology
Grid based energy storage is currently a widely used energy storage technology, which is essentially a current source and cannot provide voltage and frequency support on its own. It must rely on the voltage and frequency of the power grid to operate. During operation, the inverter of the grid connected energy storage system will follow the phase information of the grid and measure the phase of the grid connection point through a phase-locked loop, thereby achieving synchronization with the grid. This energy storage system can only operate in the presence of the power grid and cannot independently support the power grid system.
2 Principles of grid based energy storage and grid following energy storage
1. Network construction technology
The principle of the grid type energy storage system is to embed core algorithms such as the rotor motion equation and reactive power droop control of the synchronous generator into the inverter control system. The system calculates port power by collecting voltage and current, uses these core algorithms to generate reference values for voltage amplitude and phase, and shapes the inverter port to have voltage source external characteristics similar to synchronous generators, thereby achieving active support for grid frequency and voltage. This technology can effectively avoid the instability problem of phase-locked loops in weak power grids, enabling the inverter to have external voltage source characteristics and quickly output active/reactive power.
2. Network based technology
The working principle of a grid connected energy storage system is relatively simple. It mainly controls the AC side current, tracks the phase angle of the existing grid voltage through a phase-locked loop, and then forms a control signal through coordinate transformation and PWM modulation, which is fed back to the switching tube. Under this control mode, the energy storage system cannot independently provide voltage and frequency support and must rely on the stable operation of the power grid.
3 The difference between grid type energy storage and grid type energy storage
(1) Different power attributes
Grid based energy storage systems are voltage sources that can autonomously set and output voltage and frequency, while grid based energy storage systems are current sources that cannot provide voltage and frequency support independently.
(2) Different control methods
Grid type energy storage adopts a power synchronization strategy similar to synchronous generators, which can achieve synchronization without the need for phase-locked loops. And grid connected energy storage relies on phase-locked loop technology to track the phase angle of the grid voltage and achieve synchronization with the grid.
(3) Different support capabilities for the power grid
The grid based energy storage system has a strong support capability for the power grid. It can not only operate in grid connected mode, but also independently operate in islanding mode, providing multiple functions such as frequency/inertia support and voltage support for the power grid. In weak power grids, grid type energy storage can provide stable frequency support and help improve the stability of the power grid. However, grid connected energy storage systems have stability issues in weak power grids and cannot actively support the power grid system.
(4) Different application scenarios
The grid connected energy storage system is suitable for situations where the power grid has good stability and does not require additional voltage and frequency support. It is mainly used to supplement the instantaneous power demand of the power grid, improve the stability and reliability of the power grid. Grid based energy storage systems are more suitable for new power systems, especially in areas with a high proportion of new energy and poor grid stability.
4 Summary
As a rising star in the field of energy storage, grid based energy storage technology is gradually changing the development pattern of the energy storage industry with its strong grid support capability and adaptability. It can not only effectively solve problems such as low inertia, low damping, and weak voltage support in new power systems, but also provide stable and reliable power support for the power grid in various complex scenarios. Compared with traditional grid based energy storage technology, grid based energy storage technology has demonstrated significant advantages in terms of technical principles, power attributes, control methods, and application scenarios. With the continuous development of new energy generation and the increasing demand for stability in the power system, grid based energy storage technology will play a more important role in the future energy field, providing strong technical support for building a more intelligent, efficient, and reliable new power system.
The emergence of grid based energy storage technology provides new ideas and methods for solving stability problems in new power systems. It can not only effectively improve the operational efficiency and reliability of the power grid, but also better adapt to the intermittent and fluctuating characteristics of new energy generation, laying the foundation for building a more intelligent, flexible, and efficient energy system. In the future, with the continuous advancement of technology and the reduction of costs, grid based energy storage is expected to be widely applied in more fields, contributing to the promotion of energy transformation and sustainable development.