Photovoltaic Power Profile Emulation Software PPPE

Introduction

The Photovoltaic Power Profile Emulation (PPPE) software automatically calculates solar array voltage and current profiles based on user-defined parameters. These profiles can be sequentially sent to a Magna-Power Electronics power supply, which will emulate defined characteristics. The user can define a limitless number of profiles to be emulated and sequenced over a given time period.

Design and production validation for photovoltaic connected electronics requires a photovoltaic emulating power source with flexible output characteristics. Inverters and specialized DC-DC converters employ maximum power point tracking (MPPT) control algorithms to maximize utilization of nonlinear energy sources, such as solar panels and wind turbines. For development and manufacturing, using photovoltaic arrays for validation is costly with uncontrolled source characteristics. By utilizing a power supply with user-programmable output characteristics, the user can evaluate the full range of power conditions.

After the profile is defined, it can be transferred to the power supply for either static or dynamic emulation. A time dependent parameter defines how long the power supply should emulate that profile before loading the next profile in the sequence.

Video Overview

The following video provides a demonstration of the various functions and programming modes within the PPPE Software:

Modeling and Operation

A profile is a voltage/current curve that the power supply’s output should emulate. There are three methods to generate a power profile in the PPPE software:

Automatic, based on solar array parameters
The user selects the desired solar panel technology, nominal temperture, irradiance, voltage and current values. Each V-I profile is then defined only by new temperature and irradiance values. The rest of the parameters: maximum power point (Vmp, Imp), open circuit voltage (Voc), and short circuit current (Isc); are all calculated automatically in accordance with the EN50530 standard.
Automatic, based on 4-parameters
The user defines the maximum power point (Vmp, Imp), open circuit voltage (Voc), and short circuit current (Isc). The profile is then generated based on these parameters.
Manual
The user defines up to 50 current and voltage points for the power supply to emulate. The power supply performs a piecewise linear approximation between points to provide a smooth output curve.

Advanced Feature Set

Magna-Power Electronics worked closely with solar inverter manufacturers to refine the PPPE feature-set. Some of the key advanced PPPE features are as follows:

EN50530 Modeling
The European EN50530 standard provides a new algorithm for proper solar array modeling. PPPE 2.0 incorporates this model, furthermore allowing the selection of thin film or polycrystalline silicon parameters. Defining a curve is as simple as specifying desired open-circuit voltage, short-circuit current, and maximum power point. Alternatively, manual parameters can be entered for more customized modeling or profile importing from an external file.

Live Output Viewer
A new live output viewer provides six graphs of instantaneous output parameters versus time. This data allows the user to visualize fluctuations in voltage, current, and power over time.

Curve Interpolation
An interpolation function was added to automatically generate transitional curves. This functionality enables smooth transitions from one curve to another over a user-defined period of time.

Data Logging
Customizable data logging functionality was added, allowing for report generation and data analysis using external tools. Data is exported to a comma-delimited (.csv) file.

Command Export
Leverage the ease of profile generation in PPPE and export the generated SCPI commands for integration into a separate programming environment, such as LabVIEW/LabWindows.

Specifications

General Specifications
Cutoff Frequency (-3dB) With High-Slew Rate option: 15 Hz
Standard models: 2 Hz
Communication Protocols Supported RS-232, LXI TCP/IP Ethernet, GPIB, USB
Minimum Time Between Profiles 2 sec
Number of Profiles Per Sequence Unlimited
Minimum Voc and Isc 10% of power supply's rated voltage and current
Maximum Profile Slope (ΔI/ΔV) × (Imax /Vmax) ≤ -0.05
Instantaneous Load Change to Short-circuit With High-Slew Rate option only

Solar Emulation Performance Characteristics

High Slew Rate: Equivalent Output Impedance During Solar Emulation:

High-Slew Rate: Voltage Error During Solar Emulation:

High-Slew Rate: Frequency Response During Solar Emulation