Integrating battery banks to wind farms for frequency support provision–capacity sizing and support algorithms

Abstract

The expected high penetration levels of wind energy in power systems require robust and practical solutions to maintain typical conventional systems performance. Wind farms (WFs) positive contribution in eliminating grid frequency deviations still a grey area, especially when they replace considerable conventional generation capacities. This paper offers a sizing algorithm to integrate storage battery banks (SBs) in WFs to provide feasible power support during frequency events. This algorithm determines the required rated power and capacity of each SB inside a WF according to several constrains, including wind speed characteristics at WF location. The size of the SB is based on a statistical study for the amounts of rejected wind power, and the events of low wind production. The offered operation algorithm controls the SB charging, discharging, and standby modes based on the acquisition of different dynamic variables, for example, WF output, load demand and storage cells' state of charge. The operation algorithm aims to mitigate frequency drops, rejected wind power and maintain the battery lifetime. Both algorithms are applied on a defined sector from a genuine conventional system merged with real WS chronological records at certain locations which are candidates to host WFs. Results reveal the positive influence of SB involvement on frequency excursions clearance, in addition, wasted wind energy is mitigated since wind turbines de-loading techniques are avoided and some rejected wind power is utilized to charge the installed SBs. Precise models are integrated through MATLAB and Simulink simulation environment.

Enhancing frequency stability by integrating non-conventional power sources through multi-terminal HVDC grid

“…The control method applied is a developed version of the control proposed in [20], implementing a rate-of-change-of-frequency (RoCoF) and droop based frequency control and an export power deviation balancing support, as shown in to avoid negative impacts on battery lifetime (cycling). Moreover, when the BESS reaches a certain threshold (close to SOC min ), the provided power starts to decay with a fixed rate, such that no support is provided after few seconds.…”

“…inertia response) [14][15][16]. On the other hand, supporting slow primary response by either maintaining certain power reserves on wind turbines through de-loading or over-speeding control techniques [17][18][19], or coordinating wind farm response with energy storage systems [20,21]. In the HVDC based systems, the transmission network may contribute to frequency support through modifying the power sharing among the different stations [22][23][24] or by trying to take advantage of the existing energy stored within the capacitors of the DC side, which could act as DC grid inertia [25,26].…”

Novel metrics to quantify the impacts of frequency support provision methods by wind power

“…However, according to the applied sizing method that counts mainly on the WS and load-demand variations, the SBs of the two locations are not equal. The rated power of the SBs assigned to Ghareb and Nabq are 42 and 28 MW respectively [5]. The share of a single GE-77 is estimated proportional to its rated power compared to the aggregate rated power of the WF, so that the 'indirect' power step provided by the WTG is evaluated, thus ES/Pr is obtained using (4), where ∆Pdisch is the rated power of the SB (The SB provides its rated power as soon as frequency violates the safe dead-band to mitigate the dependence on frequency measurements and maximize the impact of the provided support).…”

“…The two locations selected for the assessment of Method 2 are also investigated, so that the results are comparable. According to [5], Ghareb and Nabq sites have the same number and types of WTGs (65*GE-77 1.5MW, and 65*G-90 2MW). However, according to the applied sizing method that counts mainly on the WS and load-demand variations, the SBs of the two locations are not equal.…”

“…These two methods provide frequency support directly through the WTG. Energy storage mediums, namely battery banks were implemented in [5] to provide indirect support (Method 3). This paper proposes a simple generalized approach to evaluate the inertial response provided by a generation unit/plant.…”