Hierarchical Control of Paralleled Voltage Source Inverters in Islanded Single Phase Microgrids

Author(s):  
Ilyas Bennia ◽  
Yacine Daili ◽  
Abdelghani Harrag
2021 ◽  
Vol 2 (2) ◽  
pp. 44-53
Author(s):  
GENNADY S. MYTSYK ◽  
◽  
ZAW HTET HEIN ◽  

The recent interest of developers of new technology in studying a structural and algorithmic synthesis (SAS) of voltage source inverters (VSI) for solar power plants (SPP) is stemming from a growing need to solve problems in connection with the revealed new possibilities of converting energy flow (from DC to AC) with better energy efficiency by reducing the depth of its pulse modulation. This problem is solved by using more rational structural and algorithmic solutions. It is shown that for SPPs for a capacity of about 1 MW and more, it is more expedient to construct inverters based on the energy flow multichannel conversion principle. Given a limited power capacity of the transistor components, the application of this principle allows the problem to be solved in fact without using an output filter. The output voltage waveform is shaped using the energy flow pulse-amplitude modulation (PAM), and its M parts are summed in the output circuit by out using M winding transfilters (M-TF). The proposed method for carrying out combined SAS of single-phase voltage source inverters with multichannel conversion is considered, which consists in using an N-level single-phase VSI (N-SPVSI) in each of the M channels with the voltage levels optimized in terms of the minimum total harmonic distortion (THD). The resulting voltage of this class of single-phase inverters, designated as MxN-SPVSI, is formed by the corresponding phase shift of the channel voltages followed by summing the channel currents by M-TF. It is shown that the resulting output voltage levels are also close to their values optimized with respect to the minimum of the THD indicator. The results from a comparative analysis of two options — a single-channel 8-level inverter and a four-channel 8-level inverter are given. For the second option, only one intermediate voltage tap in the solar battery is required (instead of seven taps in the first option) along with modern transistor components that are available for practical implementation. In both options, the THD value less than 5% is obtained with almost no need of using an output filter. The presented results provide a certain information and methodological support for system designing of single-phase voltage source inverters as applied to the specific features of solar power plants. Three-phase inverters can be built on the basis of three single-phase inverters with galvanic isolation of the power sources for each phase.


Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1643
Author(s):  
Jorge El Mariachet ◽  
Yajuan Guan ◽  
Jose Matas ◽  
Helena Martín ◽  
Mingshen Li ◽  
...  

The dynamic performance of the local control of single-phase voltage source inverters (VSIs) can be degraded when supplying to nonlinear loads (NLLs) in microgrids. When this control is based on the droop principles, a proper calculation of the active and reactive averaged powers (P–Q) is essential for a proficient dynamic response against abrupt NLL changes. In this work, a VSI supplying to an NLL was studied, focusing the attention on the P–Q calculation stage. This stage first generated the direct and in-quadrature signals from the measured load current through a second-order generalized integrator (SOGI). Then, the instantaneous power quantities were obtained by multiplying each filtered current by the output voltage, and filtered later by utilizing a SOGI to acquire the averaged P–Q parameters. The proposed algorithm was compared with previous proposals, while keeping the active power steady-state ripple constant, which resulted in a faster calculation of the averaged active power. In this case, the steady-state averaged reactive power presented less ripple than the best proposal to which it was compared. When reducing the velocity of the proposed algorithm for the active power, it also showed a reduction in its steady-state ripple. Simulations, hardware-in-the-loop, and experimental tests were carried out to verify the effectiveness of the proposal.


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