Toward Fully-Automated Hardware-in-the-Loop Grid Code Compliance Certification of Inverter-Based Distributed Energy Resources

Inverter-based Distributed Energy Resources (DERs) third-party compliance testing has been widely required by most grid codes to guarantee interoperability with the electrical power system. However, most grid code certification procedures only accept the evaluation of the whole product under full-power environments. For high-power equipment, this procedure is costly, time-intensive, and complex to be performed. Due to this, many efforts have been made to make possible using Controller Hardware-in-the-Loop (CHIL) testing for validation of the inverter firmware from early product development through final certification, facilitating the identification of early issues and reducing debugging time and costs. On the other hand, since most CHIL tests are performed in environments distinct from full power laboratory testing, both approaches often follow different procedures and do not take into account the same metrics, which can result in low fidelity between CHIL and power laboratory results. In order to make possible to use CHIL for compliance testing, model validation has to be performed, guaranteeing that model fidelity is satisfactory. In this context, this paper presents a comprehensive methodology to validate CHIL models and to clearly identify, measure, and reduce differences between the results obtained with CHIL and with power laboratory testing environments. The methodology is based on standardized quantitative test procedures applied to both CHIL and power laboratory testing. The proposed methodology is extensively validated through experimental results carried out on a commercial single- phase photovoltaic inverter. Results demonstrate the validity of CHIL testing methodology and propose an alternative method for grid code compliance testing and certification.