Frequency stability is the core indicator for ensuring power supply quality and system safety in the operation of the power system. With the increasing proportion of new energy generation and the increased volatility of the power grid, the traditional single frequency regulation mode of thermal power units is no longer able to meet the high-precision and fast response frequency regulation requirements. The combined frequency regulation technology of thermal power and energy storage, through the coordinated operation of thermal power units and energy storage systems, fully leverages the advantages of both and becomes an important means to improve the frequency regulation performance of the power system.
1 The principle of combined fire storage and frequency regulation
The core principle of combined frequency regulation of thermal power and energy storage is based on the regulation logic of "functional complementarity and energy synergy". By integrating the energy output stability of thermal power units with the fast response capability of energy storage systems, it achieves precise and efficient correction of grid frequency deviation.
1. Complementary response characteristics
Thermal power units have a large regulating capacity and sustained output capability, but are limited by mechanical inertia, resulting in a slow response speed (usually in the tens of seconds), and the regulating accuracy is easily affected by factors such as fuel supply and unit wear; The energy storage system has a fast response capability ranging from milliseconds to seconds, flexible charging and discharging switching, and can accurately track high-frequency and small amplitude frequency fluctuations. However, the energy storage capacity is limited, making it difficult to maintain high power output in the long run. When the two are combined, the energy storage system prioritizes responding to high-frequency and fast frequency regulation commands, while the thermal power unit undertakes low-frequency and continuous regulation tasks, forming a collaborative mechanism of "fast replenishment and slow stability".
2. Energy balance regulation
The frequency deviation of the power grid essentially stems from the imbalance between supply and demand of active power. The combined fire storage system receives real-time AGC (Automatic Generation Control) instructions from the power grid dispatch through the central control system, and dynamically allocates and adjusts power based on the current output status of the thermal power unit, SOC and response speed of the energy storage system. When the frequency deviation is small, the energy storage system quickly throughput power to suppress fluctuations; When the deviation continues or increases, the thermal power unit gradually adjusts its output, while supplementing energy to the energy storage system to ensure its availability in subsequent frequency regulation and achieve dynamic energy balance.
3. Economic optimization
Frequent deep regulation of a single thermal power unit can lead to increased coal consumption and accelerated equipment loss, while the high-frequency charging and discharging of energy storage systems also need to control costs. The joint system reduces the adjustment range and frequency of thermal power units and lowers their operating losses by optimizing power allocation strategies; At the same time, by reasonably planning the timing of energy storage charging and discharging, utilizing the peak valley electricity price difference or auxiliary service revenue to offset the operating costs of energy storage, the dual optimization of technical performance and economy can be achieved.
2 Main methods of combined frequency regulation for fire storage
According to the differences in control strategies and operating modes, the combined frequency regulation of fire storage can be divided into the following main methods:
1. Master slave control mode
This method uses thermal power units as the "main regulating body" and energy storage systems as the "secondary regulating body". The central controller first calculates the total regulation demand based on the frequency modulation command, and the thermal power unit undertakes the basic regulation power. The energy storage system compensates for the response delay and accuracy error of the thermal power unit in real time.
For example, when the AGC command requires an increase in output, the energy storage system immediately releases power to respond quickly, and the thermal power unit gradually increases output and charges the energy storage until the command target is reached. This method is suitable for scenarios where the regulating capacity of thermal power units is sufficient but the response speed is insufficient, which can reduce the demand for energy storage capacity while ensuring stability.
2. Peer to peer control method
Thermal power units and energy storage systems serve as equal regulating entities, with the central controller allocating regulating power in real-time based on their dynamic characteristics such as response speed, current capacity, and loss costs. By establishing a multi-objective optimization model, the regulation amount of thermal power units and energy storage systems is allocated in the optimal proportion while meeting the frequency regulation accuracy, achieving the maximization of overall regulation efficiency. This method is suitable for scenarios with a high proportion of new energy and severe fluctuations in frequency regulation commands, and can more flexibly cope with complex working conditions.
3. Prediction compensation control method
Combined with the prediction algorithm of power grid frequency fluctuation, the demand for frequency regulation is predicted in advance, and energy is stored or released in advance through the energy storage system. Thermal power units adjust the output trend in advance according to the prediction results. For example, using AI models to predict the frequency deviation trend within the next 10 minutes, if it is predicted to be a sustained negative deviation (low frequency), the energy storage system will charge and reserve energy in advance, and the thermal power unit will increase its basic output in advance. When the command is issued, it can quickly respond together. This method can further improve the timeliness of regulation and reduce the risk of frequency loss of control under extreme working conditions.
3 Summary
The combined frequency regulation technology of thermal power and energy storage effectively compensates for the shortcomings of a single regulation method by complementing and coordinating the characteristics of thermal power units and energy storage systems, and significantly improves the response speed, regulation accuracy, and economic efficiency of the power system to frequency fluctuations. With the advancement of the construction of new power systems, combined thermal storage and frequency regulation will play a key role in high proportion new energy grids.