# A Low-Cost Evaluation Tool for Synchronization Methods in Three-Phase Power Systems
## 2 Evaluation Tool and Methodology of Use  
The evaluation tool has three elements: (i) the emulator, (ii) a digital controller, and (iii) the methodology of use (Figure 3):  
1. The emulator is a low-cost digital platform where the voltages of a three-phase grid are emulated and where reference signals such as amplitude, phase, and frequency are generated to evaluate the synchronization algorithms. These signals must be visualized with an oscilloscope. The emulator can generate disturbances such as voltage harmonics and frequency variations and, also, generate unbalance between phases. 2. The digital controller is a second digital platform that implements synchronization algorithms and, therefore, implements the controller for the power converter. The digital controller acquires the emulated grid voltages, processes them, and generates the estimated signals for the synchronization algorithms. 3. The methodology of use is the action to be executed for the correct connection between the emulator and the digital controller; it includes actions to evaluate and compare the performance of the synchronization algorithms. Additionally, the methodology indicates the configuration of an oscilloscope for applying the methods. The voltage grid generated by the emulator can be configured according to the test to be performed, allowing us to set the (i) amplitude, (ii) phase, (iii) frequency, and (iv) harmonic content of the grid. Different case studies can be predefined and selected through a simple interface built from switches. The algorithm implemented in the digital controller will estimate the frequency, phase, and amplitude of the acquired grid voltages. The digital controller must generate the following analog signals using the estimated values computed by the synchronization algorithm: (i) synchronized grid voltages, (ii) amplitude, (iii) phase, and (iv) frequency. In the event that several methods or configurations need to be evaluated, external switches allow for the selection of these methods or configurations, allowing different estimated signals to be shown with the limited digital-to-analog converters (DACs) that are typically available. The evaluation and validation of the synchronization algorithms are performed by comparing and analyzing the emulated grid voltages, the reference signals, and the signals estimated in the digital controller. A digital oscilloscope is required to display the signals and compute some numeric indicators. Moreover, the execution time (\(t_{ex}\)) of the algorithms is evaluated through a digital output on the digital controller. The emulator generates a synchronization signal to be used as a trigger for the correct visualization of the signals in the oscilloscope. For the performance analysis of the algorithms, the reference and the estimated signals are compared using the (i) overshoot (OS), (ii) settling time (\(t_{s}\)), (iii) root-mean-square  
Figure 3: Diagram of the proposed evaluation tool. error (RMSE), and (iv) mean error (ME). The performance evaluation also considers the (v) execution time of the algorithm in the digital controller. The implementation requires that the digital platform must have at least three (DACs) or pulse-width modulated (PWM) outputs with low-pass, which will be used for the three-phase signals. Furthermore, the digital platform requires at least one DAC to generate the fundamental voltage, amplitude, phase, or frequency references, which will be displayed in the oscilloscope and used as references for the evaluation. Finally, the digital controller requires three analog-to-digital converters (ADCs) and at least one DAC to display the estimated signals. The emulator and the digital controller require each one to have at least one digital output and two digital inputs. The following subsections present (i) the emulator's implementation using the Texas Instruments digital development platform and (ii) the methodology of use.