A Parameter-Adaptive Method for Primary Frequency Regulation of Grid-Forming Direct-Drive Wind Turbines
Abstract
1. Introduction
2. The Basic Principle of Wind Turbines Participating in Primary Frequency Regulation and the Control Strategy of Grid-Forming Direct-Drive Wind Turbines
2.1. Dynamic Analysis of the Primary Frequency Regulation Process of Wind Turbines Based on the Rotational Kinetic Energy of a Wind Wheel
2.2. Basic Structure of Grid-Forming Direct-Drive Permanent Magnet Wind Turbines
2.3. VSG Control Principle
3. Design Principles for Key Parameters Considering FM Steady State and Dynamic Characteristics
4. Parameter-Adaptive VSG Control Strategy Design Approach
4.1. Influence of the Virtual Moment of Inertia and Damping Coefficient on the Stability of the System
4.2. System Frequency Comparison under Different Parameters
4.3. Transient Process Analysis of the D-DPMSG-VSG System under a Load Disturbance
5. System Simulation and Analysis
- (1)
- The simulation wind speed is set at 8 m/s, and the wind turbine works in the maximum power tracking area. The simulation waveforms under two different load disturbance conditions are illustrated in Figure 15 and Figure 16. The simulation waveform display includes: a comparison of system frequency, active power output, and rotor speed of the wind turbine; curves of and ; and the fluctuation of the DC bus voltage. Table 4 presents the system frequency data for the wind power system under various control strategies and different load disturbance conditions. To validate the effectiveness of the proposed VSG-PAC in enhancing the frequency regulation capability of wind turbines, a load disturbance of 0.1 pu and 0.15 pu is introduced at 10 s. The comparison control strategies are set as MPPT control and VSG-FPC.
- 1.
- When the load disturbance is 0.11 pu, the absence of an inertial response capability in MPPT control results in a rapid drop in the system frequency due to the load mutation. The lowest frequency observed is 49.3116 Hz, representing a significant drop. In comparison to the MPPT-controlled wind turbine, the wind turbine employing VSG-FPC exhibits some degree of inertial response and primary frequency modulation capabilities. VSG-FPC mitigates the rate of the system frequency change during the initial phase and offers frequency modulation power support during frequency drops, resulting in the lowest frequency drop point of 49.5967 Hz, an improvement of 0.2851 Hz. The enhanced VSG-PAC proposed in this paper further augments the frequency modulation capability of wind turbines, achieving the lowest frequency drop point of 49.6504 Hz. Compared to VSG-FPC, the maximum frequency deviation of the system increases by 13.3% with VSG-PAC. As illustrated in Figure 15a,b, with VSG-FPC and VSG-PAC, the frequency modulation active power output of the wind turbine rises from an initial value of 0.33 pu to peak values of 0.39 pu and 0.4 pu, respectively, while the rotor speed declines from an initial value of 0.9 pu to minimum values of 0.82 pu and 0.8 pu, respectively. Compared to VSG-FPC, VSG-PAC achieves a 2.6% increase in maximum active power output and a 2.5% reduction in the minimum rotor speed decrease. These results indicate that the improved VSG-PAC presented in this paper enables the wind turbine to release rotor kinetic energy more effectively, providing greater active support during frequency modulation and demonstrating clear advantages in frequency modulation performance. As illustrated in Figure 15f, the fluctuation in DC bus voltage is more pronounced with VSG-PAC compared to VSG-FPC. This is attributed to the fact that VSG-PAC enhances the wind turbines’ capacity to mitigate system frequency drops and increases the active power transmitted to the grid, resulting in greater instantaneous unbalanced power on the DC bus, thus widening the fluctuation range. However, the fluctuation range remains within permissible limits and will not adversely affect the DC bus equipment. The analysis under a 0.15 pu load disturbance condition yields similar results. For brevity, only a summary analysis is provided below.
- 2.
- Under a load disturbance of 0.15 pu, the lowest frequency drops of the system are 49.1102 Hz, 49.4689 Hz, and 49.5186 Hz, respectively, for MPPT, VSG-FPC, and VSG-PAC control. Compared to VSG-FPC, the maximum frequency deviation with VSG-PAC is increased by 9.4%. As illustrated in Figure 16a, compared to VSG-FPC, the output value of FM active power with VSG-PAC is improved only little. This occurs because, at this moment, the lowest rotor speed drop of the wind turbine is 0.719 pu, which is very close to 0.7 pu. The safety margin for the rotor speed is less than 0.02 pu, posing a risk of instability and turbine shutdown. In accordance with the established speed safety limits, the rotor speed cannot decrease further, thereby constraining the amount of released rotor kinetic energy. The improved VSG-PAC proposed in this paper offers substantial power support to the system while maintaining the safe operation of the wind turbine.
- (2)
- The simulated wind speed is set to 11 m/s, with the wind turbine operating in a constant speed region. The simulated waveforms under a load disturbance condition of 0.15 pu are illustrated in the Figure 17.The simulated wind speed is set to 13 m/s, with the wind turbine operating in the constant power region. Figure 18 presents the simulated waveforms under a load disturbance condition of 0.15 pu. Table 5 illustrates the impact of different wind speeds on the system’s frequency support effectiveness under a 0.15 pu load disturbance. An analysis of Figure 17 and Figure 18 and Table 5 is shown below:
- 1.
- At a wind speed of 11 m/s, the minimum frequency drops of the system are 49.1722 Hz, 49.4957 Hz, and 49.555 Hz for MPPT, VSG-FPC, and VSG-PAC control, respectively. Compared to VSG-FPC, VSG-PAC exhibits an increase in the maximum frequency deviation of 11.8%. The enhanced control strategy proposed in this paper significantly improves the inertial support capability of VSG control and further reduces the maximum frequency deviation.
- 2.
- At a wind speed of 13 m/s, the minimum frequency drops of the system are 49.2552 Hz, 49.5761 Hz, and 49.6302 Hz for MPPT, VSG-FPC, and VSG-PAC control, respectively. Relative to VSG-FPC and MPPT control, VSG-PAC shows an increase in the maximum frequency deviation of 12.76% and 50%, respectively. As illustrated by the active power output and rotor speed waveforms of the wind turbine in Figure 18b,c, the enhanced control strategy presented in this paper effectively releases rotor kinetic energy during the inertia response phase and offers greater active support to the system.
- (3)
- Taking the average annual wind speed of the Kubuqi Desert in Inner Mongolia as an example, the average annual wind speed at a 120 m height in this area is 6–8 m/s, and the average wind speed at a 160 height is 6.5–8.5 m/s. In order to verify the effectiveness of the proposed method in the turbulent wind speed scenario, the following two experimental scenarios are set up. As shown in Figure 19, in Experiment 1, the average wind speed is 6 m/s, and the turbulence degree is 25.6%. When t = 10 s, a sudden increase of a 0.02 pu load occurs during the weakening gust period. In Experiment 2, the average wind speed is 8 m/s, the turbulence degree is 10.6%, and the sudden load is 0.07 pu. The sudden load disturbance event occurs during the gradual gust period.
6. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Indices | No Change, Increase | No Change, Increase |
---|---|---|
Diminish | Amplify | |
Faster | Slower | |
Faster | Slower | |
Diminish | Amplify |
Section | |||||
---|---|---|---|---|---|
① | >0 | >0 | >0 | Amplify | Amplify |
② | >0 | <0 | <0 | Diminish | Amplify |
③ | <0 | >0 | <0 | Amplify | Amplify |
④ | <0 | <0 | >0 | Diminish | Amplify |
Wind turbine parameters | |||
Parameters | Value | Parameters | Value |
Rating power | 2.5 MW | DC bus voltage | 1200 V |
Polar logarithm | 80 | Stator resistance | 0.006 |
Stator inductance | 0.395 H | Net-side filter inductor | 0.0003 H |
Net-side filter capacitors | 25 μF | Rated frequency | 50 Hz |
Synchronous generator parameters | |||
Parameters | Value | Parameters | Value |
Rated voltage | 16.5 kV | Rated frequency | 50 Hz |
Rating power | 100 MW | d-axis reactance | 0.146 pu |
q-axis reactance | 0.0969 pu | d-axis transient reactance | 0.0608 pu |
q-axis sub-transient reactance | 0.06 pu | q-axis sub-transient reactance | 0.04 pu |
Load Disturbances | Control Strategies | ||||
---|---|---|---|---|---|
MPPT control | 49.3116 | 49.7153 | −0.6884 | −0.2847 | |
VSG-FPC | 49.5967 | 49.721 | −0.4033 | −0.279 | |
VSG-PAC | 49.6504 | 49.718 | −0.3496 | −0.282 | |
MPPT control | 49.1102 | 49.623 | −0.8898 | −0.377 | |
VSG-FPC | 49.4689 | 49.6279 | −0.5311 | −0.3721 | |
VSG-PAC | 49.5186 | 49.6254 | −0.4814 | −0.3746 |
Wind Speed | Control Strategies | ||||
---|---|---|---|---|---|
MPPT control | 49.1102 | 49.623 | −0.8898 | −0.377 | |
VSG-FPC | 49.4689 | 49.6279 | −0.5311 | −0.3721 | |
VSG-PAC | 49.5186 | 49.6254 | −0.4814 | −0.3746 | |
MPPT control | 49.1722 | 49.661 | −0.8278 | −0.339 | |
VSG-FPC | 49.4957 | 49.6626 | −0.5043 | −0.3374 | |
VSG-PAC | 49.555 | 49.6615 | −0.445 | −0.3385 | |
MPPT control | 49.2552 | 49.7355 | −0.7448 | −0.2645 | |
VSG-FPC | 49.5761 | 49.7359 | −0.4239 | −0.2641 | |
VSG-PAC | 49.6302 | 49.7356 | −0.3698 | −0.2644 |
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Hu, S.; Meng, K.; Wu, Z. A Parameter-Adaptive Method for Primary Frequency Regulation of Grid-Forming Direct-Drive Wind Turbines. Sensors 2024, 24, 6651. https://doi.org/10.3390/s24206651
Hu S, Meng K, Wu Z. A Parameter-Adaptive Method for Primary Frequency Regulation of Grid-Forming Direct-Drive Wind Turbines. Sensors. 2024; 24(20):6651. https://doi.org/10.3390/s24206651
Chicago/Turabian StyleHu, Siqi, Keqilao Meng, and Zikai Wu. 2024. "A Parameter-Adaptive Method for Primary Frequency Regulation of Grid-Forming Direct-Drive Wind Turbines" Sensors 24, no. 20: 6651. https://doi.org/10.3390/s24206651
APA StyleHu, S., Meng, K., & Wu, Z. (2024). A Parameter-Adaptive Method for Primary Frequency Regulation of Grid-Forming Direct-Drive Wind Turbines. Sensors, 24(20), 6651. https://doi.org/10.3390/s24206651