## 3 The Measurement Setup  
Laboratory measurements for this research were conducted on a prototype microgrid that emulates DER, utilizing several single-phase commercial grid inverters. The PV inverters are powered by a programmable DC source (specifically, the ITECH model IT6000C [30]), which can simulate the characteristics of PV modules and energy storage batteries. This testing system was initially designed to validate the steady-state performance of new grid inverter control algorithms.  
The laboratory microgrid setup for testing PV inverters includes several main components: PV inverters under test, a programmable bidirectional DC supply to emulate PV arrays, local inductive and resistive loads, and instrumentation for measuring current harmonics. This setup includes a programmable logic controller (PLC) for managing grid topology, complemented by a suitable supervisory control and data acquisition (SCADA) to synchronize testing procedures and collect measurement results.  
Figure 1 shows a photo and schematic representation of the microgrid setup's main components. The microgrid can operate in two modes: a grid-connected mode with contactor Q1 closed or a grid-isolated mode with this contactor open. Local loads can be switched on and off using individual contacts in six different combinations.  
A programmable DC source emulates the characteristics of a PV array comprising several connected modules to test the PV inverters. The output current of the DC source (\(I_{\text{DC}}\)) is injected into the PV inverter.  
The DC source is programmed using the Solar Array Simulation software SAS1000L version 2.2.0, which provides numerous features, including the option to generate current-voltage (I-V) characteristics of the modules based on various technological and environmental parameters [31]. For the purpose of this research, a built-in EN 50530 test program was used to provide static and dynamic MPP efficiency tests in compliance with the given standard [28]. Specifically, static tests with predefined power and voltages are performed.  
The inverter output current (IAC), DC component, and harmonic distortion are measured using a precise LMG450 power analyzer and LabVIEW virtual instrumentation designed to validate DERs in compliance with the IEEE 1547-2018 standard [32]. LMG450 power analyzer is a reference device for LabVIEW virtual instrument verification. This LabVIEW testing environment uses the virtual instrumentation approach, utilizing NI USB-9264 acquisition module and USM-3 IV isolated voltage and current sensor module  
Figure 1: Photo of laboratory microgrid site **(left)**: 1—device under test, 2—LMG450, 3—local load, 4—DC source, 5—grid connection. A schematic of a test setup with three PV inverters, powered by a programmable DC power source **(right)**. On-grid mode is achieved by closing contactor Q1.  
to measure electrical quantities. The current harmonics and TRD factor calculations are processed on a computer. A crucial part of the testing environment is the software operating on a computer, performing real-time calculations and analyses based on the data collected from the acquisition modules. The DER testing environment can simultaneously perform all measurements required by the IEEE 1547-2018 standard using a single measurement setup. Additionally, it generates a comprehensive validation assessment report detailing the measured parameters.