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This paper presents a gross examination about Unified Power Quality Conditioner (UPQC) to invigorate the power issues at the distribution level of the electrical system. Nowadays power electronics research has added the importance of power quality studies, for concrete illustration, Custom Power Devices (CPD) and Flexible AC Transmission position (FACTS) devices. The approach offered in this paper utilizes the series and shunt compensator of Unified Power Quality Conditioner (UPQC) to inject a compensation voltage in-phase with the source current over voltage fluctuations. The execution of two structures of UPQC, left-shunt (L-UPQC) and right-shunt (R-UPQC) are investigated under diverse operating conditions based on the fuzzy logic controller to raise the value of power quality of a single feeder distribution system by MATLAB/Simulink programming. Various power quality issues have been analyzed in this study. Finally, the right shunt UPQC is outperformed in this proposed power system.

Power quality issues are getting increasingly massive in nowadays in the break of the expanding number of power electronic devices that hold on as nonlinear loads. A generous assorted status of answers for power quality issues is noticeable for distribution network operator and the end user [

UPQC is well known as the universal active power line conditioner, universal power quality conditioning system, and universal active filter [

With respect to the Custom Power necessities [

A standout amongst the most productive frameworks to take care of power quality issues is Unified Power Quality Conditioner (UPQC). It comprises of a Parallel and a Series-Active Filter together with a typical DC link [

In this way, the operation of the UPQC secludes the utility from current quality issues of load and in the meantime isolates the load from the voltage quality problems of utility.

The point of this work to present the power quality issues and to discuss the solutions of some of these problems is using power electronic controllers. The paper examines the power quality problems with UPQC with the execution of the left shunt and right shunt connection of the proposed power system fuzzy logic controller approach.

The general diagram of an UPQC distribution network is shown in _{s}) in phase with the terminal voltage (v_{t}). Therefore, the voltage of any bus upstream from the PCC will not be pretentious due to a nonlinear and unbalanced load. Though, it will be problematic to rectify the unbalance and distortion created by the source voltage using this device. In this manner, the upstream bus voltages will remain unbalanced and distorted [

The single-line diagrams of these two systems are shown in _{t}. The load voltage, load current, and source current are indicated by v_{l}, i_{l} and i_{s} respectively. V_{d} indicates the voltage and current injected by the UPQC and if respectively. The source voltage is indicated by v_{s}, while R and L constitute the feeder impedance.

The UPQC shall perform the following two functions, one is to change the feeder (source) current is to adjust sinusoids through the shunt compensator and the second is to change the load voltage (v_{l}) to balanced sinusoids through the series compensator besides control it to the desired value. Contingent upon the location of the shunt compensator on series compensator, the UPQC model

could be named as Right Shunt-UPQC or Left Shunt-UPQC. Both topologies of UPQC have similar features. The primary motivation behind UPQC and other similar custom power controllers is to detect voltage and current imperfections and after that give compensation or disconnection of custom power controllers from the distribution system.

The left-shunt UPQC schematic is appeared in _{t}, and the series inverter keeps up the voltage over the load V_{l} by following the voltage V_{d}. Hence, the two inverters track two quantities regardless of the possibility that they are independent. It is hence expected that the stability issue won’t emerge for left-shunt UPQC structure.

_{d}. The switched voltage, over the shunt and series inverter output terminals are then signified by V_{dc}u_{1} and V_{dc}u_{2} separately. The state space equation of this circuit

can likewise be composed with six state variables and two input variables. The state and input vectors are

x T = [ i 1 i 2 i 3 i 4 v t v d ] , u T = [ u c 1 u c 2 ] . (1)

Moreover, the state space equation of the system is then given by,

x ˙ = A x + B 1 u + B 2 v s .

where

A = [ − R L 0 0 0 − 1 L 0 0 − R f L f 0 0 − 1 L f 0 0 0 − R l L l 0 1 L l 1 L l 0 0 0 − R d L d 0 − 1 L d 1 C f − 1 C f − 1 C f 0 0 0 0 0 − 1 C d 1 C d 0 0 ] (2)

B 1 = [ 0 0 − V d c L f 0 0 0 0 V d c L d 0 0 0 0 ] (3)

B 2 = [ 1 L 0 0 0 0 0 ] (4)

The schematic diagram of the right shunt structure appears in

The single-phase equivalent circuit of the right shunt UPQC is appeared in _{l} and L_{l} mean the load. The LC filter over the series inverter is spoken to by L_{d} and C_{d} while the resistance R_{d} speaks to the inverter losses. The inductance L_{T} signifies the leakage

inductance of the transformers associated with the series. The leakage inductance of the shunt transformer is indicated by L_{f} while the resistance R_{f} speaks to losses. The shunt filter capacitor is meant by C_{f}, the voltage at the load terminal is the voltage over this filter capacitor. The series injected voltage V_{d} is appeared in _{sd} is the voltage over the capacitor C_{d}. A typical capacitor supplies the series and shunt inverters. V_{dc} signifies the voltage across this capacitor. The switched voltages over the series and shunt inverter yield terminals are then meant by V_{dc}u_{1} and V_{dc}u_{2} respectively.

From right-shunt UPQC structure, the tracking control, stability issue is staying away from through the choice of LC filter for the series inverter and capacitor filter for the shunt inverter. Consider the equivalent circuit; the inductance L_{T} will be zero as the transformer leakage inductance will then be in series with the series inverter. However, a feedback control is required to track the voltages crosswise over both the capacitors and the absence of L_{T} tracking voltage V_{l} by the shunt compensator will make the tracking voltage V_{d} over the series compensator repetitive and vice versa.

By driving the two inverters to track the voltages over their respective capacitors, the stability issue will emerge as one controller will meddle with the tracking execution of the other. Hence, to maintain a strategic distance from the tracking issue the LC filter structure for the series inverter is more appropriate for the right shunt UPQC. Likewise, the LC filter limits the switching frequency harmonics in the primary of the transformer associated with it.

To infer a state-space model of the system, that the circuit of contains six state variables - four loop currents and two capacitor voltages. It can be,

x T = [ i 1 i 2 i 3 i 4 v s d v l ] . (5)

The circuit of _{1} and u_{2}. Give us a chance to supplant u_{1} and u_{2} by the continuous time variables uc_{1} and uc_{2} individually and characterize the accompanying control vector.

u T = [ u c 1 u c 2 ] . (6)

The state space equation of the framework is then given by

x ˙ = A x + B 1 u + B 2 v s . (7)

where the A, B_{1} and B_{2} are given by

A = [ − R L + L r 0 0 0 1 L + L r − 1 L + L r 0 − R d L d 0 0 − 1 L d 0 0 0 − R f L f 0 0 1 L f 0 0 0 − R l L l 0 1 L l − 1 C d 1 C d 0 0 0 0 1 C f 0 − 1 C f − 1 C f 0 0 ] . (8)

B t = [ 0 0 V d c L d 0 0 − V d c L f 0 0 0 0 0 0 ] . (9)

B 2 = [ 1 L + L T 0 0 0 0 0 ] . (10)

The fuzzy control gives a formal technique to speaking to, controlling, and executing a human’s heuristic information about how to control a framework. Fuzzy memberships NL, NM, NS, ZE, PS, PM, PL is characterized as negative large, negative medium, negative small, zero, positive small, positive medium and positive significant.

The “fuzzy inference system” is a popular computing framework based on the ideas of fuzzy set theory, fuzzy if-then rules, and fuzzy reasoning [

_{sh} is utilized to interface the shunt inverter to the system. It also helps in smoothing the current wave shape. Sometimes an isolation transformer is used to electrically isolate the inverter from the system. A typical dc link can be framed by using a capacitor or an inductor. In

This circuit is operated under two operating modes, one is Left shunt associated UPQC, and another is right shunt associated UPQC. During left shunt

UPQC, the shunt converter is attached to the load side, and the series converter is associated with source side through series injection transformer. Similarly, the right shunt associated system; the converter association is turned around. The proposed UPQC system compensates the load voltage on the source voltage associated with series converter. The control groupings of left and right shunt compensation of UPQC system are done through the series and shunt regulator by providing legitimate gate pulse generation to the UPQC.

System | %THD (Harmonic order) | %THD (Frequency order) |
---|---|---|

Without UPQC | 45.10 | 45.10 |

Left Shunt UPQC | 2.51 | 29.35 |

Right Shunt UPQC | 2.15 | 26.93 |

system. Both left shunt and right shunt evacuate the harmonic part introduce into the system.

Harmonic analysis reaction for uncompensated and compensated (left shunt and right shunt) are introduced in

A broad simulation study has been displayed in the paper to demonstrate the presence of the left shunt and right UPQC. The load voltage and current are compensated by the implementation of UPQC in left shunt and right shunt of the power system. Also, the reactive power compensation with the magnificent transient reaction is necessary. From the system point of perspective, the performance of the right shunt UPQC and left shunt UPQC applications don’t differ all the more, however the right shunt UPQC is performed superior to anything left shunt. In any case, if 100% terminal voltage compensation has to be given from the UPQC under a voltage sag condition, the right shunt configuration of the UPQC is found to be more economical. In this way, the fuzzy control strategy can lessen the rating of the installed UPQC significantly without compromising on the wanted performance objectives as identified by the network codes. With the implementation of the fuzzy controller, both left, and right shunt UPQC configurations are performed well to expel the harmonics and real and reactive power compensation. Nonetheless, from the overall performance, it is observed that the right shunt UPQC is performed better than left shunt UPQC configuration as appeared in the outcome

Balaslubramaniyan, S. and Sivakumaran, T.S. (2017) Fuzzy Logic Controller Implementation of Power Quality Improvement Using UPQC. Circuits and Systems, 8, 202-226. https://doi.org/10.4236/cs.2017.88014