With the increasing integration of renewable energy sources like wind and solar into power grids, energy storage systems have become critical for stabilizing grid operations. As the interface between energy storage batteries and the grid, the energy storage inverter plays a pivotal role in bidirectional power conversion. This paper presents the design and validation of a Rapid Control Prototype (RCP) experimental platform for energy storage inverters using the RT-LAB real-time simulation system. The platform enables rapid testing and optimization of control strategies, significantly accelerating development cycles compared to traditional embedded controller-based approaches.
Topology and Mathematical Model
The energy storage inverter employs a three-phase two-level voltage source converter (VSC) topology. The mathematical model in the synchronous d-q reference frame is expressed as:
$$
L \frac{d}{dt} \begin{bmatrix} i_d \\ i_q \end{bmatrix} = \begin{bmatrix} u_{sd} \\ u_{sq} \end{bmatrix} – R \begin{bmatrix} i_d \\ i_q \end{bmatrix} + \omega L \begin{bmatrix} i_q \\ -i_d \end{bmatrix} – \begin{bmatrix} u_{cd} \\ u_{cq} \end{bmatrix}
$$
where:
– $L$ and $R$: Filter inductance and resistance
– $i_d$, $i_q$: d-q axis current components
– $u_{sd}$, $u_{sq}$: Grid voltage components
– $u_{cd}$, $u_{cq}$: Inverter output voltage components
The active and reactive power equations are:
$$
P = 1.5u_{sd}i_d, \quad Q = -1.5u_{sd}i_q
$$
Control Strategy Implementation
A dual-loop vector control strategy with d-q decoupling was implemented:
| Control Loop | Function | Parameters |
|---|---|---|
| Outer Loop | Power regulation | $K_p=0.8$, $K_i=120$ |
| Inner Loop | Current tracking | $K_p=1.2$, $K_i=300$ |
The PWM generation method employs RT-Events technology with timestamping for enhanced precision:
$$
t_{edge} = t_n + \delta \cdot T_s
$$
where $t_n$ is the step start time, $\delta$ the duty ratio, and $T_s$ the switching period (200 μs).
RCP Platform Architecture
The developed platform integrates three main components:
| Component | Specification | Interface Type |
|---|---|---|
| RT-LAB OP5600 | 4-core CPU, 2 GHz | FPGA I/O boards |
| Inverter Prototype | 20 kVA, 380 VAC | Optical isolation |
| Battery Emulator | 200-800 VDC, 50 kW | CAN & analog I/O |
Experimental Validation
Test conditions included:
– DC link voltage: 200 V
– Grid voltage: 380 VLL
– Switching frequency: 5 kHz
Key performance metrics:
$$
\begin{aligned}
\text{THD} & \leq 3\% \\
\text{Response time} & < 2 \text{ ms} \\
\text{Power tracking error} & < 1.5\%
\end{aligned}
$$
The results demonstrate effective power regulation and stable operation under various load conditions, validating the energy storage inverter control strategy and RCP platform effectiveness.
Conclusion
This work successfully developed an RT-LAB-based RCP platform for energy storage inverters, featuring:
- High-fidelity real-time simulation (100 μs step)
- Precision PWM generation with <1 μs resolution
- Comprehensive hardware-in-loop validation
The platform significantly reduces development time while improving control strategy robustness, providing an effective solution for modern energy storage inverter development challenges.