Coordinated Primary and Secondary Frequency Support Between Microgrid and Weak Grid

Abstract

Dispersed wind power connected to the weak grid may cause the frequency instability. In this paper, a hierarchical controller applied to a microgrid (MG), including wind turbines (WT) and battery units (BU), is proposed to provide in a coordinated frequency support to a weak grid by adjusting the tieline active power flow according to the frequency-grid requirements. The coordination between MG local and central controllers provides the following features. (i) In case of required grid-frequency, the MG tie-line power flow will be controlled to be constant in each dispatching time interval. (ii) In case of underfrequency, the coordination between WT virtual inertia and BU controllers will be used to participate in primary frequency regulation (PFR). Then, BU supplies power according to the secondary frequency regulation (SFR) commanded by the maingrid dispatch center. (iii) In case of over-frequency, BU absorbs power to reduce the tie-line active power for PFR purposes. After that, the SFR uses pitch control coordinated with the battery charge control. A stability analysis model is established to deal with several transitions among different operation modes and the interaction between the weak grid impedance and the MG output impedance. Simulation results are presented to validate the proposed approach. Index Terms-Wind/battery microgrids, primary frequency regulation (PFR), secondary frequency regulation (SFR), hierarchical control, central controller, local controller NOMENCLATURE Parameter DescriptionWW Generated wind energy [J] T Scheduling period [min] PWf Forecast output power of WT [W] PT Average wind power [W] B * Reference power of the BU inverter [W] PWT Actual WT output power [W] PWT * WT expected output power [W] Pinertia WT virtual power inertia [W] f Difference between the grid frequency and the rated one [Hz] k PFR factor [-] kd Differential coefficient of the frequency deviation [-] PAGC_MG AGC power scheduling of MG [W] PAGC_g AGC power scheduling of grid[W] CMG Frequency-regulation capacity of the MG [W] are with Tianjin Key Laboratory of Advanced Electrical Engineering and Energy Technology, Tianjin Cg Frequency-regulation capacity of the grid [W] fmin Minimum value of the normal frequency [Hz] fmax Maximum value of the normal frequency[Hz]  WT rotor angle speed [rad/s] rated WT rotor rated angle speed [rad/s]  PMSG rotor position angle[] p Pole pairs number of PMSG[-] Psloss PMSG stator losses[W] isabc PMSG stator current[A] Udc Back-to-back converter dc bus voltage[V] Air density [kg/m 3 ] WT radius[m] Wind energy utilization factor [W‧s 3 /kg‧m 2 ] β * Pitch angle reference of the WT [] β Pitch angle of the WT [] λ Tip speed ratio[-] maximum wind energy utilization factor [W‧s 3 /kg‧m 2 ] Popt WT maximum power [W] sd , sq d-q stator inductances [mH] s Stator resistance [Ω] sd , sq d-q stator voltages [V] Synchronous angular velocity[rad/s] φ Permanent magnet flux of the PMSG [Wb] Te Electromagnetic torque of the PMSG [N‧m] E Kinetic energy stored in the WT [J] J Inertia of the WT and i...

A Quadratic Programming-Based Power Dispatch Method for a DC-Microgrid

“…One very important feature of the MG is the ancillary support capability. Among them, the frequency support [31] that Power [kW] P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P Accumulated rate/day: 377.51 USD P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P B SoC Battery SoC [%] P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P Battery SoC [%] P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P…”

2019 Index IEEE Transactions on Sustainable Energy Vol. 10

“…Quality Disturbances Using Unscented Kalman Filtering; TSTE July 2019 1240-1247 Symko-Davies, M., see Baggu, M.M., TSTE April 2019 886-894 T Takahashi, Y., see Fujimoto, Y., TSTE Jan. 2019 55-65 Talari, S., see Hajibandeh, N., TSTE April 2019 918-930 Talari, S., Shafie-khah, M., Chen, Y., Wei, W., Gaspar, P.D., and Catalao, J.P.S., Real-Time Scheduling of Demand Response Options Considering the Volatility of Wind Power Generation; TSTE Oct. 2019 1633-1643 Tan, J., see You, S., TSTE April 2019 718-728 Tang, C., Kao, L., Chen, Y., and Ou, S., Dynamic Power Decoupling Strategy for Three-Phase PV Power Systems Under Unbalanced Grid Voltages; TSTE April 2019 540-548 Tang, X., Yin, M., Shen, C., Xu, Y., Dong, Z.Y., and Zou, Y., Active Power Con-trol of Wind Turbine Generators via Coordinated Rotor Speed and Pitch Angle Regulation; TSTE April 2019 822-832 Tascikaraoglu, A., Paterakis, N.G., Erdinc, O., and Catalao, J.P.S., Combining the Flexibility From Shared Energy Storage Systems and DLC-Based Demand Response of HVAC Units for Distribution System Operation Enhancement; TSTE Jan. 2019 137-148 Tascikaraoglu, A., see Sengor, I., TSTE July 20191034-1043 Terreros, O., see Jacobs, T., TSTE July 2019 1362-1369 Terzija, V., see Zhao, J., TSTE April 2019 706-717 Teshome, D.F., Xu, W., Bagheri, P., Nassif, A., and Zhou, Y., A Reactive Power Control Scheme for DER-Caused Voltage Rise Mitigation in Secondary Systems; TSTE Oct. 2019 1684-1695 Thomas, R.J., see 1280-1289 Thorp, J.S., see 1523-1533 Todeschini, G., Balasubramaniam, S., and Igic, P., Time-Domain Modeling of a Distribution System to Predict Harmonic Interaction Between PV Converters; TSTE July 2019 1450-1458 Tor, O.B., see Cebeci, M.E., 2152-2162 Torres, J., see Blanco, M., TSTE July 20191076-1085 Tremblay, M., see Rezkallah, M., TSTE Jan. 2019 181-191 Tricarico, T.C., see 1380-1392 U Ukil, A., see Wang, B., TSTE Oct. 20191867-1877 Ukil, A., see Gupta, P., TSTE July 2019 1120-1128 V Valverde, G., Shchetinin, D., and Hug-Glanzmann, G., Coordination of Distributed Zhao-xia, X., TSTE Oct. 20191718…”

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Load frequency control assessment of tidal power plant and capacitive energy storage systems supported microgrid

“…Therefore, proper inertia support from units like WPP and TPP is important to enhance the performance of LFC [5]. A study on different inertia control strategies (considering the case of constant and variable inertia support) on WPP to improve ROCOFD is presented in [6,7]. These works conclude that the inertia control strategy improves the ROCOFD, but, it fails to offer better control over the maximum frequency deviation.…”