Search

Active and reactive power control using smart inverters (SI) is highly effective in mitigating voltage rise in distribution systems, which is caused by the high penetration of photovoltaic (PV) power generation. However, the voltage control performance depends on the SI settings. We propose a new approach that uniquely determines the parameter settings for volt-VAR-watt control based on the active and reactive power-voltage sensitivity matrix of SIs. Because the voltage sensitivity matrix is calculated based solely on the impedance of the distribution system and it does not vary with time or the number of SIs, the proposed method can determine the individual SI parameter settings theoretically and efficiently without the need for optimization problem formulation, power flow calculation, or communication between the SIs. To evaluate the proposed method, the voltage control performance in a real distribution system model with a large number of PV installations is compared with that of volt-VAR-watt control using default parameters and optimized parameters in case that the load demand and PV generation are given in advance. The results show that the proposed method achieves better control performance than other conventional methods in terms of all the evaluation indices; in particular, it realizes effective control in the case of voltage rise. Furthermore, the proposed method can also achieve the same level of voltage control performance as the optimization results, even though it uses only the voltage sensitivity matrix and SI rating capacities for parameters determination, and the accuracy of the proposed voltage control can be ensured.

The power hardware-in-the-loop (PHIL) simulation has become a popular testing approach due to the flexibility it provides and the high-fidelity of its results. It is expected to be utilized as an advanced laboratory testing scheme to validate the grid support functions of distributed energy resources (DERs) because it can evaluate the interaction between the power system and DERs. Despite the strong demand to utilize the PHIL simulation for such testing, the literature that elaborates on the practical design of PHIL simulation based testing (hereafter called “PHIL testing”) environment including laboratory device setup, power system models, and test procedures is very limited. The simulation models, interfacing with the tested equipment, and data collection approaches are all different parameters that need to be fine-tuned for the successful execution of PHIL testing. It is vital for such successful test experiences to be shared to build universal knowledge around PHIL testing. In order to fill this knowledge gap, this paper presents such practical and essential techniques for the PHIL testing to share the knowledge for promotion of the PHIL simulation utilization. The development of PHIL testing environment to validate the smart inverter functions, i.e., volt-var function and frequency-watt function, is focused on in terms of laboratory setup, power system modeling, interfacing, and test procedure. The volt-var and frequency-watt functions of a 500 kW smart inverter of photovoltaic are validated on the basis of the presented techniques. Detailed test configurations, test procedures, and simulation models are presented along with obtained test results.

Inertia reduction due to inverter-based resource (IBR) penetration deteriorates power system stability, which can be addressed using virtual inertia (VI) control. There are two types of implementation methods for VI control: grid-following (GFL) and grid-forming (GFM). There is an apparent difference among them for the voltage regulation capability, because the GFM controls IBR to act as a voltage source and GFL controls it to act as a current source. The difference affects the performance of the VI control function, because stable voltage conditions help the inertial response to contribute to system stability. However, GFL can provide the voltage control function with reactive power controllability, and it can be activated simultaneously with the VI control function. This study analyzes the performance of GFL-type VI control with a voltage control function for frequency stability improvement. The results show that the voltage control function decreases the voltage variation caused by the fault, improving the responsivity of the VI function. In addition, it is found that the voltage control is effective in suppressing the power swing among synchronous generators. The clarification of the contribution of the voltage control function to the performance of the VI control is novelty of this paper.