# Optimal Modeling for Dynamic Response of Energy Storage Systems
## 2 Introduction and Building of Models for Energy Storage Systems
### Universal Model of WECC Energy Storage System
#### 2.1.2 REEC Module  
The REEC module is known as the generic renewable electrical control model. The same as the REPC module, this module is divided into an active power control loop and a reactive power control loop; the module control block diagram is shown in Figure 3. All parameters and their meanings in the REEC module are listed in Table 2. The reactive power control loop of this module is more complex than the active power control loop as it contains multiple control flags that are linked with the REPC module and jointly determine the current function of the energy storage system.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Symbol** & **Description** \\ \hline
1 & \(T_{fltr}\) & Voltage or reactive power measurement filter time constant (s) \\
2 & \(K_{p}\) & Reactive power PI control proportional gain (pu) \\
3 & \(K_{i}\) & Reactive power PI control integral gain (pu) \\  
_{S}\) & Power controller lag time constant (s) \\
26 & \(D_{dn}\) & Droop for over-frequency conditions (pu) \\
27 & \(D_{up}\) & Droop for under-frequency conditions (pu) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameters of the REPC module.  
Figure 2: The REPC module control block diagram of a universal model of energy storage systems. Reprinted from Ref. [4] (Fig. 12), 2016, [PERSON].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Symbol** & **Description** \\ \hline
1 & \(V_{dip}\) & Voltage threshold to activate reactive current injection logic (pu) \\
2 & \(V_{up}\) & Voltage above which reactive current injection logic is activated (pu) \\
3 & \(T_{rp}\) & Voltage filter time constant (s) \\
4 & \(dbd1\) & Voltage error dead band lower threshold (\(\leq\)0) (pu) \\
5 & \(dbd2\) & Voltage error dead band upper threshold (\(\geq\)0) (pu) \\
6 & \(K_{qp}\) & Reactive current injection gain during over and undervoltage conditions (pu) \\
7 & \(Iqhl\) & Upper limit on reactive current injection Iqinj (pu) \\
8 & \(Iqll\) & Lower limit on reactive current injection Iqinj (pu) \\
9 & \(V_{ref0}\) & User defined reference (if 0, model initializes it to initial terminal voltage) (pu) \\
10 & \(T_{p}\) & Filter time constant for electrical power (s) \\
11 & \(Q_{max}\) & Limit for reactive power regulator (pu) \\
12 & \(Q_{min}\) & Limit for reactive power regulator (pu) \\
13 & \(V_{max}\) & Max. limit for voltage control (pu) \\
14 & \(V_{min}\) & Min. limit for voltage control (pu) \\
15 & \(K_{qp}\) & Reactive power regulator proportional gain (pu) \\
16 & \(K_{qi}\) & Reactive power regulator integral gain (pu) \\
17 & \(K_{qp}\) & Voltage regulator proportional gain (pu) \\
18 & \(K_{oi}\) & Voltage regulator integral gain (pu) \\
19 & \(T_{iq}\) & Time constant on delay s4 (s) \\
20 & \(dP_{max}\) & Power reference max. ramp rate (\(>\)0) (pu/s) \\
21 & \(dP_{min}\) & Power reference min. ramp rate (\(<\)0) (pu/s) \\
22 & \(P_{max}\) & Max. power limit (pu) \\
23 & \(P_{min}\) & Min. power limit (pu) \\
24 & \(I_{max}\) & Maximum limit on total converter current (pu) \\
25 & \(T_{pend}\) & Power filter time constant (s) \\
26 & \(V_{q1}\) & Reactive Power V–I pair, voltage (pu) \\
27 & \(I_{q1}\) & Reactive Power V–I pair, current (pu) \\
28 & \(V_{q2}\) & (Vq2 \(>\) Vq1), Reactive Power V–I pair, voltage (pu) \\
29 & \(I_{q2}\) & (Iq2 \(>\) Iq1), Reactive Power V–I pair, current (pu) \\
30 & \(V_{q3}\) & (Vq3 \(>\) Vq2), Reactive Power V–I pair, voltage (pu) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of the REEC module.  
Figure 3: The REEC module control block diagram of a universal model of energy storage systems. Reprinted from Ref. [4] (Fig. 12), 2016, [PERSON].