Motivated by recent advances in industrial data communications, MW-class PV parks are increasingly utilizing communication-based coordination among different power converters to achieve accurate voltage regulation and stability, particularly during grid events. However, communication delays present in data transfer networks reduce coordination quality and deteriorate the ability of the PV park to respond in a timely manner. This paper investigates the impact of such delays on the voltage recovery performance of grid-tied converters in a PV park, coordinated by a centralized secondary voltage controller (SecVC), under different grid and delay conditions. In addition, to enhance the coordination quality, a local strategy for the converter-level controller is proposed to reduce the control sensitivity to the communication delays. The theoretical results obtained from nonlinear model and Monte-Carlo analysis are validated using a real communication setup between two Hardware-in-the-Loop devices (HIL), interfaced through a communication network emulator using the Modbus-TCP protocol.

The energy systems are evolving toward the comprehensive and massive integration of power electronics-based technologies, such as photovoltaic, wind turbines, and electric vehicles. All these emerging and promising power converters technologies must be tested to comply with the grid codes, especially during severe grid fault events, before their commercialization. Low-Voltage Ride-Through (LVRT) field tests are usually conducted to prove the ability of the converter to ride through faults. These field tests are expensive and require bulky equipment, while Power-Hardware-in-the-Loop (P-HIL) offers a more cost-effective and flexible alternative. However, the P-HIL must be stable and accurate to get reliable results. The accuracy of a P-HIL test is directly influenced by its interface algorithm. This paper proposes a frequency domain approach, based on the concept of singular values in Multi-Input Multi-Output systems, to study the P-HIL accuracy and stability in grid connected converter testing under asymmetrical line-to-line fault conditions. Accuracy and stability analysis have been performed analytically and validated by Matlab/Simulink simulations and by experimental P-HIL tests. This paper demonstrates that correct fault modeling leads to correct assessment of the reactive power injected under faults and of avoiding resonances.