1 Application of energy storage system

The power grid structure can be roughly divided into the power supply side, power grid side, and household side. On the power supply side, for traditional generator sets, the integration of the energy storage system can assist in improving the AGC performance of the generator set and increase the frequency adjustment capability of the generator set. At present, it has been widely used and promoted. On the grid side, the energy storage system is directly integrated into the grid side to intervene and control the main grid with abnormal frequency, which can become an effective means for grid frequency stability control. On the user side, the easiest application scenario for energy storage technology is based on the peak-to-valley price difference, using energy storage products “low charge, high discharge” to achieve profitability. With the integration of volatile and intermittent new energy power into the grid, the application of the energy storage system on the generation side of the new energy power generation system can significantly improve the acceptance capacity of the grid and effectively increase the transmission capacity of the line. This paper focuses on the application of energy storage on the power generation side of new energy power generation systems.

2 Typical structure of energy storage on the power generation side of a new energy power generation system

The output power of the new energy power generation system fluctuates randomly due to the external environment and other factors, and the load switching in the system is also uncertain. The main function of the energy storage device is to supplement the power shortage of the system and make the system run in a dynamic balance process. To ensure the stable operation of the system and restrain the fluctuation of the system voltage. The block diagrams of the DC side and AC side of the energy storage device connected to the system are shown in Figure 1 and Figure 2. To maintain the stability of the bus voltage of the system, the energy storage unit must achieve the balance of power generation and load consumption through the function of peak shaving and valley filling. Similarly, the stability of the system output voltage is the external manifestation of the system’s input and output power balance. Therefore, the power balance of the system is combined with the voltage stabilization, and the control of the energy storage system is realized by the algorithm of the energy storage unit’s charge and discharge tracking the DC side voltage.

Figure 1 The energy storage unit is connected to the DC side of the system

Figure 2 The energy storage unit is connected to the AC side of the system

3 Operational control of energy storage on the power generation side of new energy

3. 1 Control of stable DC side voltage of energy storage device

The control of the energy storage system is realized by the algorithm of the charging and discharging of the energy storage unit to track the DC side voltage. From this, the control topology of the energy storage device to stabilize the DC side voltage is shown in Figure 3.

Figure 3 The energy storage device is connected in parallel to the DC side topology of the system

4. 2 Control of stable AC voltage of energy storage device

The control of the energy storage system is realized by the algorithm of the charging and discharging of the energy storage unit to track the AC side voltage. From this, the control topology for stabilizing the DC side voltage of the energy storage device is shown in Figure 4.

Figure 4 The energy storage device is connected in parallel to the system AC bus topology

To prevent extreme weather conditions from affecting the system, operational protection control is assumed in the system. When it is detected that the voltage at both ends of the battery Ubat> Ubat max, the battery is in an overcharged state; when Ubat <Ubat max, the battery is in an over-discharged state. In these two cases, the battery stops charging and discharging control. When using a battery as the energy storage element of a photovoltaic power generation unit, try to choose a large-capacity battery, because a large-capacity battery can ensure the uninterrupted power supply of the system.

4 Typical applications of energy storage on the power generation side of a new energy power generation system

4. 1 Abandonment of wind and solar/planned power generation solutions

Due to the intermittent, fluctuating, and unpredictable characteristics of new energy power generation, large-scale access will inevitably increase grid regulation difficulties, and may cause a large number of solar and wind abandonment problems. Adding an energy storage system on the new energy generation side can solve these problems well. It can store the energy that cannot be consumed and release it when power generation is insufficient or peak power consumption. To smooth power generation and consumption, it can make up for new energy power generation. Unstable defects, avoid waste. The schematic diagram of the wind and solar curtailment/planned power generation solution is shown in Figure 5.

Figure 5 Schematic diagram of abandoning wind and light/planned power generation solutions

4.2 Application of smooth new energy power generation output

The output of new energy power generation such as photovoltaic and wind power has strong volatility. Large-scale grid connection will cause many adverse effects on the economic and safe operation of the power grid, which in turn limits the scale of new energy power generation and restricts the large-scale power generation of new energy. Large-scale development and utilization, and energy storage can effectively smooth the output curve of new energy power generation, which is of great significance for improving the operational performance of large-scale new energy power generation networks. Figure 6 shows the application diagram of smooth new energy power generation output.

Figure 6 Schematic diagram of an application of smooth new energy power generation output

4. 3 Multi-energy complementary energy storage solutions

Among the renewable energies, the use of wind, hydro, and solar power generation is the fastest growing and most promising renewable energy source. Each has its characteristics and is complementary in time and space. Its complementary power generation is more than a single power generation. Efficient and reliable way. It can smoothly generate electricity, make up for the instability of new energy generation, and avoid waste. The schematic diagram of the multi-energy complementary energy storage solution is shown in Figure 7.

Figure 7 Schematic diagram of multi-energy complementary energy storage solution

Concluding remarks

The installation of energy storage systems in wind farms and photovoltaic power plants will greatly enhance the friendly dispatching capabilities of the entire system. This paper analyzes the typical structure of the energy storage unit connected to the power generation side of the new energy power generation system and the corresponding operation control. The three typical solutions mentioned above have good application prospects.