This method is further improved to detect the desired harmonic frequency for compensation [55]. If Vdc is greater than Vdcref, the battery converter stops delivering power from the battery side. For parallel operation, the output voltage of all inverters must be kept strictly in phase in order to guarantee equality of the output active power for the corresponding inverters. This is suitable when forming an ac power ring. It prevents the compensator from supplying DC load current.

Depending upon the switching condition, there are two possible modes of operation: Hence, a suitable control strategy has to be developed in UPQC, which has improved DC-link voltage regulation as well as tracking performance through load and grid perturbations. From the above equations, it is found that the active power is predominantly dependent on the power angle f , while the reactive power mostly depends on the output-voltage amplitude E. Hence, a suitable control strategy has to be developed in UPQC, which has improved DC-link voltage regulation as well as tracking performance through load and grid perturbations. For the proposed system, the required capacitor size will be; 5. Hence, careful attention should be given to system design and the control method of parallel operating inverters.

The performances of both current control techniques for SAPF are evaluated under different source voltage conditions such as balanced, unbalanced and non-sinusoidal. The control function has been performed with a hierarchical approach.

From the design perspective, some configurations involve the generators being directly connected to the grid through a dedicated transformer while others incorporate power electronic interfaces.

The number of DG systems such as Photovoltaic and Wind Energy Systems are now penetrating more into the grid or microgrid at the same time the number of non-linear loads are also increasing.

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Ogasawara, Implementation and performance of cooperative control tesis shunt active filters for harmonic damping throughout a power distribution system, IEEE Trans.

To detect the harmonic voltages, the active filter is characterized as behaving like a resistor for harmonic frequencies [ – ]. The detection of the fundamental positive-sequence component of vsa, vsb, and vsc is necessary in the sinusoidal current control strategy. New method for reconnection of islanded wind turbines to grid, PECon, pp. As a result, the proposed algorithm provides more robustness, flexibility and adaptability in all operating conditions of the power system network.

The control method for islanding detection and reconnection is placed in the secondary level. However it requires high speed communications. This is unlike the conventional over-current protection for radial systems with unidirectional flow of fault current. Centralized approach Multi-modular i. Therefore, DG inverter can remove the islanding detection technique from its control ohd.

upqc phd thesis

For all cases, the simulated system has been run for 1 sec. The connection topology and switching configuration of a 3-ph, 3- wire APFsh together with the chosen parameters range is shown in Fig 2. Upcq, the current harmonics are considered and are compensated by using the shunt active power filter SAPF.

Also there is no central control and no information sharing between thdsis APFs. Voltage unbalance could occur between the Converter based achieved different levels ii.

Islanding Detection IsD e. As an example, Fig 5. This novel method is proposed here for the D-UPQC system where the multiple thewis APF units are based on hysteresis current control and operated in a power sharing mode. It is also clear from Fig 6. The load sharing is also affected by the line impedance [, ]. The main purpose of the power electronic converters is to integrate the DG to the grid in compliance with PQ standards.

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Voltage at PCC is maintained constant.

The UPQC current sensor, for reactive and harmonic power compensation, measure only the load current. Therefore, primary control will be based on the functionality of the series and shunt part of the UPQC. Different controlling mechanism and topologies are available in phx the difficulties of parallel operation of inverters either in active load sharing or distributed mode. It inserts voltages so as to maintain the load voltages at a desired level; balanced and distortion free.

The value of Cse can be calculated using the Cut-off frequency fc equation of an LC filter; 2. Each progress in the research enhances the compensation capabilities of the previous UPQC control system. Conclusions are made in Section 3. This happens because of the moderate value of and h for A7 compared to that of A6 is too low and A8 is too high.

upqc phd thesis

Poor power quality severely affects on electrical equipment and finally results in significant economic losses. The main advantage of the proposed control algorithm is that upac online extraction is needed to perceive the UPQC parameters.

The waveform of the utility current contains fewer harmonics for A7 compared to A6 and A8.