Energy emulator is a specific type of power electronic system to mimic the electrical behavior of an energy source and facilitate the testing of energy system. This paper presents a study of a photovoltaic (PV) emulator which is formed by a current source, a diode string and some resistors. It is constructed according to the one-diode photovoltaic model. Unlike the previous study, this paper focuses on using the model equations to

Photovoltaic (PV) Emulators: Design, Performance, and Applications

Introduction:
A Photovoltaic (PV) emulator is an electrical device designed to replicate the behavior of a real photovoltaic system under controlled laboratory conditions. PV emulators are a specialized type of power electronic system that can mimic the current-voltage (I–V) characteristics, dynamic responses, and thermal behavior of solar panels. By reproducing these characteristics, PV emulators provide a reliable and safe platform for testing, development, and validation of photovoltaic systems, energy storage integration, and power converters without relying on actual solar irradiation. These devices are crucial in research, engineering education, and industrial applications, where precise and repeatable conditions are needed for experimental validation.

Historical Development:
The concept of energy emulation in electrical engineering has evolved alongside the growth of renewable energy technologies. Initially, testing photovoltaic systems relied on natural sunlight, which introduced variability and limited repeatability. Early laboratory setups used resistive loads and basic current sources to approximate solar panels, but these methods could not accurately reproduce the nonlinear behavior of PV cells.

With the advent of power electronics and the growing demand for renewable energy systems, the need for programmable PV emulators became apparent. Researchers began to design circuits based on mathematical models of photovoltaic cells, such as the one-diode and two-diode models, to accurately reproduce the electrical characteristics of solar panels. These emulators allow engineers to test maximum power point tracking (MPPT) algorithms, inverters, and energy management systems under controlled and repeatable conditions.

Technical Principles and Operation:
A PV emulator aims to replicate the current-voltage characteristics of a solar panel. The most widely used model in PV emulators is the one-diode equivalent circuit, which consists of:

1. A current source representing the photogenerated current.

2. A diode string modeling the nonlinear behavior of the PV cell’s p-n junction.

3. Series and parallel resistors to account for internal resistive losses.

By adjusting the parameters of the current source, diode, and resistors, the emulator can replicate the I–V and power-voltage (P–V) curves of a selected PV panel. Unlike actual solar panels, the emulator can operate under any predefined conditions, including variable irradiance, temperature, and load, providing a flexible platform for experimental studies.

Design and Performance Investigation:
In recent research, PV emulators were designed using model equations of the one-diode photovoltaic model to determine the optimal circuit parameters. The design process involved:

• Selecting a target PV panel for emulation.

• Calculating the current source magnitude based on the panel’s short-circuit current and irradiance.

• Determining diode parameters to replicate the panel’s nonlinear I–V curve.

• Including resistors to accurately model series and shunt resistance effects.

The resulting emulator was tested under laboratory conditions to evaluate both electrical and thermal performance. The experiments demonstrated that the emulator achieves high power efficiency at the maximum power point (MPP). Thermal analysis revealed that the highest power dissipation occurs at the open-circuit voltage (Voc) operating point, which is critical for designing cooling solutions and ensuring component reliability.

Applications:
PV emulators are versatile tools with applications in research, education, and industry:

1. Testing and Validation of PV Systems: Engineers use PV emulators to test inverters, charge controllers, and MPPT algorithms without relying on unpredictable sunlight conditions.

2. Design of Hybrid Energy Systems: PV emulators allow integration testing of solar systems with batteries, supercapacitors, or fuel cells under controlled load conditions.

3. Educational Laboratories: Universities and technical institutes use PV emulators to teach students about photovoltaic behavior, power electronics, and renewable energy integration.

4. Accelerated Reliability Testing: By simulating extreme conditions, PV emulators can help identify design weaknesses and improve system durability before deployment.

Influence on Renewable Energy Research:
PV emulators have transformed research in renewable energy and power electronics. Their ability to replicate real PV system behavior enables engineers to optimize performance, reduce experimental risks, and accelerate product development. The use of PV emulators has led to:

• Improved MPPT algorithms, ensuring PV systems consistently operate at maximum efficiency.

• Enhanced energy management strategies in hybrid renewable systems.

• Safer and more repeatable laboratory experiments, enabling innovation in small-scale and large-scale PV integration.

New Progress and Innovations:
Recent advances in PV emulation include:

1. Programmable PV Emulators: Modern emulators use microcontrollers or digital signal processors (DSPs) to dynamically adjust output voltage and current, simulating irradiance and temperature changes in real time.

2. High-Fidelity Emulation: New circuits improve accuracy by implementing multi-diode models, temperature-dependent parameters, and dynamic response features to better replicate real PV cells.

3. Integration with Simulation Tools: PV emulators can now interface with software simulation platforms, enabling hybrid hardware-in-the-loop (HIL) experiments and predictive testing.

4. Compact and Modular Designs: Advances in power electronics allow the development of portable, modular emulators, which are convenient for classroom demonstrations, research, and field testing.

Challenges and Considerations:
While PV emulators are valuable, certain challenges must be addressed:

• Thermal Management: High power dissipation at open-circuit voltage requires careful cooling design.

• Component Nonlinearity: Accurate emulation depends on high-quality diodes and current sources that closely follow the theoretical model.

• Dynamic Response: Rapid changes in simulated irradiance or load can stress the emulator components and affect accuracy.

Conclusion:
Photovoltaic emulators are essential tools for renewable energy research, providing a controlled, repeatable, and safe platform for testing and validation of solar energy systems. By accurately replicating the electrical and thermal characteristics of real PV panels, emulators enhance the development of efficient PV systems, MPPT algorithms, and hybrid renewable energy solutions. Ongoing innovations in programmable, high-fidelity PV emulators continue to expand their applicability in academic, industrial, and educational contexts, contributing to the broader adoption of solar energy technologies.

Keywords: Photovoltaic emulator, PV system, renewable energy, one-diode model, maximum power point, power electronics, hybrid energy systems, laboratory testing.

design the circuit parameters of the emulator to mimic a selected PV panel and evaluate the circuit performance from both electrical and thermal perspectives. A laboratory experimental setup is built and tested to verify the design. The emulator is power efficient at the maximum power point. The highest power dissipation of the circuit occurs at the open-circuit voltage operating point.

This entry is adapted from: https://ieeexplore.ieee.org/document/8638207