“Design a Simulation of Power Systems Stability in Presence of Photovoltaic Systems.”

Abstract

The use of renewable energy resources has gained so much attention and popularity in the world as alternative energy to the conventional thermal, hydro and nuclear energy. But the increasing use of fossil fuels like coal, gases and petroleum product will create a deficiency in future along with some other issues like increasing price, environmental pollutions. Again increasing demand of electrical energy for a luxurious society forces the power engineers to think of alternative energy sources in the form of wind, solar, biomass etc. Among these resources, solar energy is the most promising and emerging as popular source of electrical energy in society having potential utilization for remote rural communities. However, there are many potential use of solar photovoltaic (SPV) being a sustainable solution. There is a lot of opportunity for such technologies to provide a cost-effective solution to demand of electricity for the rural poor peoples of developing nations. In addition, development and increasing number of micro grids and standalone off grid and on grid challenges which needs to be addressed for effective and operation requires improvements in system design and control. However, installation of solar photovoltaic (PV) for electricity generation might be not a good mitigation for the problem whereby some internal issues to be rectified and to be stabilized for the better power quality to be generated. Therefore, in this paper we use one of the methods for the better power quality. This paper presents the design and simulation of an active power filter (APF) supported by a PV plant by using P-Q theory algorithm to control APF.

Introduction

I. INTRODUCTION

The weather exchange and the new technology may also initiate foremost changes in electricity technology and intake patterns. The gadget connected to the distribution network is turning into more diversified including the use renewable energy supply, like solar panels or wind turbines, amongst other technology. A photovoltaic (PV) System immediately converts sunlight into electricity. The obtained energy depends on solar radiation, temperature and the voltage produced within the voltage module. Also, one of the most common troubles while connecting small renewable energy systems to the electric grid is that PV can inject harmonic additives that may become worse the electricity high-quality.

Thus, it is crucial to investigate voltage stability within the grid when it is associated with PV generation. As far as voltage is concerned, it is one of the important parameters in a system which plays a major role in power plant and the voltage stability has to be taken care to avoid major problem occurrences. Due to the probabilistic in nature of PV generation and significant difference from conventional synchronous generators, a significant increase in solar generations in the grid may present technical challenges and major impacts on system stability. Various studies have been conducted to simulate and investigate the effects of solar power on power system stability.

In PV penetrating rate is one of the causes which can influence the voltage stability. The PV penetration will improve the stability performance of a power system. PV will increase the real power and improves the reactive power of a particular power system. Grid connected solar photovoltaic system is where the power system is being energized by the photovoltaic panels installed in particular buildings and the power source is supplied via utility grid.

In this the control algorithm proposed permits the implementation of APF with the three different stages, first, there is no APF and also no solar power is given to it. Second, there is system use available solar power to energize the DC link and the load fed from grid. Means available PV and APF. And third the system use all the PV power energize DC link to supply the load power, additionally, the excess PV energy is exported to the grid, means available PV with APF and the Excess PV energy to the grid.

II. ACTIVE POWER FILTER OPERATION.

Some equipment, generally known as active filters (AF) are also called active line conditioners (APLC), instantaneous reactive power compensator (IRPC), active power filters (APF) and active power quality conditioners (APQC) [4].

There are basically two types of active filters: the shunt type and the series type. It is possible to find active filters combined with passive filters as well as active filters of both types acting together. The most common and widespread filter is the shunt active power filter (APF). APF are suitable to act in three phase systems with three or four wires. The theory for four wire systems is demonstrated with detail. The principal objective of an APF is to compensate harmonic currents, to improve the power factor, to balance the phases in the system and to eliminate the power flowing through neutral wire. In order to achieve those goals shunt power filters has to be controlled in a way that acts as a current generator giving to the load the undesirable power components, thereby, the grid only has to provide the fundamental sinusoidal components. An APF is essentially a power converter with a DC side and AC side, the controller maintain the capacitors in DC side with an stable voltage, the APF has to drain active power from the source to work properly, In it is possible to provide active power from RES to the load through the APF, interfacing the intermittent nature of RES with the load and the grid in a secure way and incrementing the quality of the system.

A. Instantaneous Power Theory applied to Active Power Filter.

The P-Q theory or ”The Generalized Theory of the Instantaneous Reactive Power in three-Phase Circuit” was proposed by Akagi et al, the theory for four wires was developed later by Aredes and Watanabi et al. Allowing to do the neutral current compensation possible. The three phase p-q theory use the Clarke transform (alpha-beta) to put the three phase coordinates in –0 coordinates, equation. Thus, it is possible to calculate the instantaneous real power, imaginary power and the zero sequence power equations.

D. PV Array

DC bus is powered by a RES, in this case with a PV source; due the DC bus has to maintain a constant DC voltage of 400V the dc voltage out of PV has to be increased. A boost DC-DC converted is used to perform the voltage level increment. The IGBT acts as a switch, pulses can be obtained comparing a triangular signal with constant magnitude and a control signal. Due the varying nature of the RES as PV constant duty cycle is not suitable for the system, for this reason various control  switching techniques are present in the literature in [7-8] techniques of maximum power point tracking are described, including perturb and observe algorithm, in [9] Hill climbing method is perform. In this simulation a simple MPPT with Perturb and Observe method is developed for his simplicity and effectiveness as seen in [10].

IV. SIMULATION RESULT

The performance of the whole system was modeled and run under Matlab/Simulink with SimPowerSystems toolbox. The model and tools of SimPowerSystems runs in discrete mode with Ts of 5us, and the Low pass filters runs in continuous mode. From 0.0s to 0.1s APF is not connected. Current signals from non-lineal loads can be observed.

An FFT analysis is perform to obtain the THD for the fundamental F = 50Hz. Table 2.

From 0.1s to 0.3s only APF function is activated, from 0.3s to 0.5s APF with PV support is activated, and, from 0.5s to 0.7s the system is enabling to feed the load. Fig. 7 shows this simulation.

A. Current at PCC

Conclusion

This work shows the use of a Shunt Active Filters as an interface between renewable energy source and the electric grid. The shunt Active filter has the capability of injecting sinusoidal currents with low THD. Active filters are a solution to power quality problems. Shunt active filters allows the compensation of current harmonics and balanced phases, together with power factor correction, and can be a much better solution than the conventional approach (capacitors for power factor correction and passive filters to compensate for current harmonics). Phase DPF PF THD (%) Phase a 0.96 0.94 13.97 Phase b 0.94 0.99 51.43 Phase c 0.92 0.96 41.86 Table.2 Currents THD Values at Load before APF Connection. This work has shown that active filters can be implemented in the same installation of the load. Different scenarios of harmonics are injected into the network to demonstrate the robustness of the filter. APF consume power from the grid, renewable resources like solar PV could be used to supply that power need. In this propose, the algorithm allows the power generated from PV to feed the total active and reactive power demand and export the surplus energy to the grid. Phase DPF PF THD (%) Phase a 1 1 1.33 Phase b 1 1 1.15 Phase c 1 1 1.76 Table.3 Currents THD Values at Load after APF Connection.

References

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Copyright

Copyright © 2023 Nikita Somkuwar, Prof. Vaishali Malekar . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.