Keywords

1 Introduction

Voltage drop is the main problem of power quality, which leads the loss of quality in power and which causes the problems in modern power systems. The main cause of this problem is the control equipment which connected to the system for controlling and protection of power system network like PLC and AC contactors which were very sensitive for load variations. Some voltage drop problems may not be affected by few equipments such as high potential drives. Usually they have the ability to withstand these small variations in voltage. But these voltage sag would create the problem for control equipment like PLC, converters and AC contactors which leads to malfunction. Because of this reason which leads to potentially shutting down the entire power system.

One of the best way to improve the power quality by reducing the voltage drop is using compensators for voltage improvement which are connected in series with line. These devices are also called as dynamic voltage restorer (DVR) [4]. DVR is a solid-state technology-based power electronic converter which used as compensator connected between load to be protected and source in series. During the voltage sag, it injects a series voltage in to line which restores the load voltage to its considered values. The most well-known strategy makes use of a series converter, supply voltage and frequency and a voltage-source inverter (VSI) connected by either a capacitor bank or a capacity structure (i.e., batteries, flywheel and so on) [5, 6]. Another method is utilization of series ac–ac converter-based AC link chopper [7]. A pulse wave voltage can be injected to the line with the help of this series converter which is a viable option [8]. This configuration has not included any sinusoidal channel and no pulse width modulation, which reduces power mismatches on VSI.

2 Previous Study

To protect the power system against three-phase voltage drops in general, three-phase compensators were recommended. This paper proposed a strategy of single-phase compensators instead of three-phase compensators to reduce the incident of three-phase voltage sags. Proposed strategy does not nullify the voltage sags which belongs to three-phase completely but converts them in to voltage sags of double phase, which can have high withstand capability for various electrical loads [9, 10].

The most effective method for coordinating voltage sags is to use series voltage compensators, also known as dynamic voltage restorers (DVR). DVR is a solid-state technology-based power electronic converter which used as compensator connected between load to be protected and source in series. It is having the capability of restoring the voltage within the specified voltage levels. The most well-known strategy is makes use of a series converter, supply voltage and frequency and a voltage-source inverter (VSI) connected by either a capacitor bank. Another thought is to use a quick strategy ac–cooling converter in conjunction with an environment control framework chopper. A strategy converter that permeates a square-wave voltage could be a best choice. This method has not included any sinusoidal channel and no pulse width control, which reduces the impact on VSI. Almost half of the shot voltage is limited by the DVR structure. This enables DVRs to provide adequate security against hangs for seasons of up to 0.1 s. Similarly, different voltage wraps a few seconds ago and gets to liberally less stood apart from half again. The excitation control voltage converters are also used to limit the destructive effects of voltage sags, unbalance in system voltage unbalance, and various other voltage drop problems.

3 Proposed System

In this proposed strategy developed based on utilization of 1-Φ voltage drop compensators in 3-Φ system, instead of 3-Φ compensators which pointing to a cost-effective game-plan. The voltage hang repeat would not be so badly harmed by this structure. A square-wave-based strategy compensator is precisely suggested in stage A for reduction in cost further more. This development stage has the most voltage records occasion and, besides the most extraordinary ones concerning extra voltage, showed up in different ways compared with stages B and C. The most sensitive loads should be introduced in this stage, with coordinates secured. This proposal replaces the use of a three-piece strategy voltage compensator with a single-orchestrate one. This proposed strategy does not completely nullify the occurrence of voltage sags but lit will reduce the consequence of occurrence of voltage sags significantly. Single-phase burdens related from stage to neutral: for this type of sensitive power loads, however long this compensator is connected before load, this strategy would completely reduce voltage hangs. Single-stage burdens linked from stage to stage: if voltage drop occurs, the proposed potential compensator will recover individual phase voltage drop, resulting in less true voltage sag.

This will deduct the effect voltage sag of sensitive loads which causes malfunction operation of control and terminal equipment of power system connected. By utilizing single-phase compensators strategy for three-stage loads will recover single-phase voltage sag problems by splitting the three-phase voltage drops in to two segment voltage drops. Regardless of the fact that it does not immediately address the difficult, the better one is less fundamental. Generally, three-phase loads are less vulnerable to 2-Φ voltage records than 3-Φ-phase ones.

4 Voltage Compensation Methods

Some relief ideas are proposed based on the examinations of the acquired estimations. The single-phase series voltage compensators can be protected in various electrical sensitive loads. It should be noted that the electrical burdens to be protected by potential compensators connected in series can be of any type.

4.1 Single-Phase Loads: Phase Substitution

A less cost supply method is to be replaced by the delicate 1-Φ loads introduced at phase A and with loads introduced at phase C. This simple transfer of load can reduce the possibility of voltage drop aggravation by 45% (Fig. 1).

Fig. 1
A schematic of the single-phase loads. It comprises V a, V b, and V c connected with former load phase C, load phase B, and former load phase A, respectively.

Scheme A: Substitute phase A sensitive loads for phase C loads

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4.2 At Phase C, a 1-Φ Voltage Compensator Connected in Series Is Used

Another method is utilization of AC to AC converter connected in series which is called as AC link chopper [7]. A pulse wave voltage can be injected to the line with the help of this series converter which is a viable option [8]. This configuration has not included any sinusoidal channel and no control strategy for modulation, which reduces power mismatches on VSI (Fig. 2).

Fig. 2
A schematic of the single-phase loads. It comprises V a, V b, and V c connected with load phases A, B, and C, respectively. In between V c and load phase C, a voltage compensator is connected.

Scheme B: A square-wave series voltage compensator is used to protect phase C. In this protected phase, delicate loads should be connected

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4.3 Three-Phase Compensation: On Phase A, a Single-Phase Series Voltage Compensator Is Used

1-Φ loads with nonpartisan and Φ-to-Φ associations, as well as three-phase loads, would frequently be found in a real establishment, and three-phase loads would frequently be found in a modern framework. In order to have a knowledgeable response for voltage lists, it is proposed to introduce a square-wave series voltage compensator only at phase A. When compared with phases B and C, this phase has the most voltage lists events as well as the most serious ones in terms of lingering voltage. After phase A has been secured, the most delicate burdens should be introduced in this phase (Fig. 3).

Fig. 3
A schematic of the three-phase compensation. It comprises V a, V b, and V c connected with load phases A, B, and C, respectively. In between V a and load phase A, a voltage compensator is connected.

Scheme C: Utilization of a voltage compensator for phase A used as square-wave potential compensator connected in series. In this protected phase, delicate loads should be connected

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5 Simulation Results

Figure 4 shows the Simulink model of proposed strategy and introduced the series compensator of three-phase compensators using MATLAB/Simulink environment. The voltage sag condition has been created by connecting nonlinear load to the system (Fig. 5). The output using normal three-phase compensators has been shown in Fig. 6. The load voltage shows that there is a voltage sag in the time period of 05–07 s because of nonlinear load connected in the system without three-phase compensator.

Fig. 4
A model of the system with three-phase compensators working in M A T L A B or Simulink environment.

Simulink model of proposed system

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Fig. 5
Three graphs plot voltage versus time. Values are estimated. A, sinusoidal curve (01, 0), (06, negative 150), (13, 350). B, sinusoidal curve (01, 0), (06, negative 70), (13, 0). C, line graph from (01, 0) to (05, 0) and (07, 0) to (13, 0). Sinusoidal curve from (05, 0) to (07, 0).

Voltage sag condition using three-phase compensator

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Fig. 6
3 graphs plot voltage versus time. Values are estimated. A plots sinusoidal curve from (0, 0), (1.5, negative 175), (2.5, 0). B plots line from (0, 0) to (0.5, 0), and (0.7, 0) to (2.5, 0), and a sinusoidal curve from (0.5, 0) to (0.7, 0). C, depicts a horizontal line between (0, 0), and (2.5, 0).

Voltage sag condition using single phase

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Voltage sag which generated has been compensated using three-phase compensators has been shown. Figure 6c shows the injected voltage in the system to compensate load voltage. Figure 6 shows the introduced single-phase series compensator instead of three-phase compensators using MATLAB/Simulink environment. The voltage sag condition has been created by connecting nonlinear load to the system at single phase. The single-phase compensators have been shown in Fig. 6. The load voltage shows that there is a voltage sag in the time period of 05–07 s because of nonlinear load connected in the system without three-phase compensator. Voltage sag which generated has been compensated using single-phase compensator has been shown. Figure 6c shows the DC capacitor voltage of voltage source inverter which is used as a single-phase compensator.

6 Conclusion

Three compensation ideas were proposed based on the estimated results: reconfigure light loads introduced on phase A to phase C; utilization of a 1-Φ series voltage compensators instead of three phase compensators. The single phase at phase C, resulting in a great accessibility of the modern power system and use of a 1-Φ potential compensator connected in cascaded on phase A for three-phase supply. This proposed strategy would convert 1-Φ voltage drops into 2-Φ voltage drops, which are less than three-phase voltage drops. This method may ensure the withstand of a few three-phase loads, despite the fact that there is occurrence of some voltage sag.