However, the DPP system has various structures, and the design method suitable for each structure should be considered. The experimental results show the comparison of the output power between the series connection system and the DPP system under various partial shading conditions. As further work, an on/off algorithm suitable for the DPP system using multiple string diode PV modules is proposed and verified by simulation.
Introduction
System Description of Differential Power Processing
- Advantages of DPP System
- DPP Algorithm
Therefore, the DPP algorithm controls the DPP converter so that the voltage of each PV module is constant. Therefore, the MPPT of the DPP system and the MPPT of the PV inverter are performed simultaneously. In this thesis, the DPP system is configured using the proposed combination of voltage balancing algorithm and MPPT total voltage maximization algorithm.
Design Methodology of Bidirectional Flyback Converter for DPP
- Bidirectional Flyback Converter Topology
- Proposed Design Methodology
- Experimental Verifications
In a flyback converter, the energy conversion efficiency is affected by the magnetizing induction of the transformer. Therefore, the efficiency of the converter is analyzed by calculating the loss components according to the magnetizing induction in the discontinuous conduction mode under the. Each power dissipation component of a bidirectional flyback converter can be expressed as a function of the maximum and rms values of the input switch current that changes as the magnetizing inductance changes.
The comparison of the maximum value and the effective value of the input switch current is as follows. Each power loss component is described as a function of the magnetizing inductance in the form of the rms and maximum values of the current. 3.3, as the magnetizing inductance value increases, the maximum value and the effective value of the input switch current decrease, and the loss of the converter decreases.
Therefore, the magnetizing inductance of the bidirectional flyback converter is designed to operate in the boundary conduction mode (BCM) with the largest magnetizing inductance in the DCM section [24]. The loss according to the magnetizing inductance of the two-way flyback converter under the nominal load in the experimental conditions of Table I as in Fig. However, it can be adjusted according to the design requirements of the DPP system to be applied.
According to the characteristics and design considerations of the proposed bidirectional flyback converter, the design methodology for selecting the magnetizing inductance value with minimum loss is proposed by calculating the loss in the boundary conduction mode.
In-Laboratory Test Method of Power Generation from PV Module
- Conventional Test Method
- Proposed Test Method
- Experimental Verifications
- Experimental Results of the DPP Operations under Various Shading Conditions
Thus, the PV characteristics of the higher output voltage are obtained as shown in Fig. Since the error of the equivalent diode voltage at the MPP can be compensated using the proposed method, the. 4.7, the current-voltage characteristic curve of the proposed emulation method shows improved accuracy at the MPP.
It is assumed that the equivalent diode voltage of the actual PV module and the proposed emulation method are almost the same at MPP. When the conventional PV emulator is used to test the DPP system, the PV module voltage increases. Therefore, the performance of the DPP system can be accurately confirmed by the proposed emulation method.
This section experimentally demonstrates the performance and accuracy of the proposed PV emulation method running on MPP. It shows that the proposed PV emulation method can provide higher accuracy in MPP than the conventional one. In addition, the accuracy in MPP can be increased regardless of the change in the amount of radiation.
The MPPs of sunlight, the conventional method, and the proposed method are listed in Table Ⅱ. The MPP of the conventional emulation method has a higher voltage than the MPP of sunlight. The power error of the proposed emulation method in MPP is smaller than that of the conventional emulation method.
Protection Algorithm Development of DPP using PHIL Simulations
- Concept of the PHIL Simulations
- Configuration of Real-time DPP Model
- Protection Algorithm Development
- PHIL Simulations Results of the DPP Protection Algorithm
Since the implemented controller of the DPP system operates with a period of 20 μs, the time step of the real-time simulation model is also chosen to be 20 μs. In conclusion, a lookup table PV model with high accuracy and low model calculation was selected as the real-time simulation PV model of the DPP system. As with the PV model, the real-time simulation of the DPP system takes into account the calculation time of the flyback, differential DPP converter.
Since the feedback converter of the implemented DPP system is designed in DCM, the average modeling is performed in the DCM domain. In the real-time simulation of the DPP system, the PV converter model is built using the P&O algorithm blocks for the MPPT. In the case of open primary and secondary sides of the flyback converter, the voltage is normal, but the current at the input of the DPP converter is recognized as zero.
In the case of the primary and secondary shorts of the flyback converter, a high current is generated at the input of the DPP converter. The verification simulation of the DPP system protection algorithm was carried out using the real-time simulation model and the protection algorithm developed in chapter 5. In conclusion, the operation of the developed DPP system fault protection algorithm was verified using the simulation PHIL.
The use of PHIL simulation-verified protection algorithms can increase the reliability of the DPP system.
![Fig. 5.2. Step size calculation of the PHIL simulation [27]](https://thumb-ap.123doks.com/thumbv2/123dokinfo/10486813.0/46.892.237.654.139.312/fig-5-step-size-calculation-phil-simulation-27.webp)
Further Works: DPP for Multiple String Diode PV Modules
DPP On/Off Algorithm for Multiple String PV Modules
Therefore, in this chapter, this thesis proposes an on/off algorithm that can select higher generation power according to the shadow condition by switching on/off DPP operation while checking the generation amount of PV system. First, the DPP operation is cycled on/off periodically to compare the power before and after to determine the operation of higher power. It can determine the DPP operation on/off even in the case where the change in the solar irradiance changes slowly.
However, if the on/off cycle period is set too short, the total power generated will be reduced. So it is necessary to set the correct period. Another method is to enable or disable DPP operation when the output power changes abruptly within a short time, and determine the higher power after comparing the power before and after. This can determine the DPP on/off operation in a situation where the solar radiation changes drastically.
For each periodic time step and power change event, it determines whether to operate through DPP operation enable/disable. Because the on/off algorithm requires measuring the power of the DPP system, the sensor configuration in Fig. Thus, the DPP system is built that maximizes the power of the PV modules and limits the operation of unnecessary converters.
The proposed on/off algorithm is applied to this system to compare the simulation results with the conventional maximum voltage DPP system.
Simulation Results
The simulation waveform on the left is the result of the conventional DPP system, and the simulation waveform on the right is the result of the DPP system with the proposed on/off algorithm. In the conventional DPP system, the DPP operation is always performed, while the proposed system determines whether the operation is. In case 1, where the amount of power generated by the DPP system is higher, the power generated by the conventional DPP system without operation discrimination is greater.
However, since the power generation difference is not large and simulation takes a long time, the determination cycle is set to a short time of 5 seconds, so the difference will be further reduced if a more appropriate period is set in the experiment itself. In case 1 and case 2, where the generation amount of the serial connection system is larger, since the DPP operation is turned off, after the DPP operation is determined, it can be seen that the generation effect of the DPP system using the proposed on/ off the algorithm is greater. In the simulation waveform on the left, the on/off determination process is not performed immediately upon the large power change.
However, in the simulation waveform on the right, higher generation power can be obtained by on/off discrimination at the time of large power change. With the help of these current change events it is possible to respond to an instantaneous change in solar radiation. As a result, the effectiveness of the proposed DPP on/off algorithm is verified through simulation results.
Conclusion
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![Fig. 1.2. PV-to-Bus structure differential power processing system [14]](https://thumb-ap.123doks.com/thumbv2/123dokinfo/10486813.0/13.892.256.641.120.603/fig-pv-bus-structure-differential-power-processing-14.webp)
