In recent day’s power distribution system is distress from acute power quality issues. In this work, for compensating Power Quality (PQ) disturbances a seven level cascaded H-bridge inverter is implemented in distribution static compensator which protects power quality problems in currents. Distribution Static Compensator (DSTATCOM) aid to enhances power factor and removes total harmonic distortion which is drawn from non-linear load. The D–Q reference theory based hysteresis current controller is employed to generate reference current for compensation of harmonics and reactive power, additionally Probabilistic Neural Network (PNN) classifier is used which easily separates exact harmonics. In the meantime fuzzy logic controller is also used to maintain capacitor DC-link potential. When comparing to PI controller it decreases steady state time and reduces maximum peak overshoot. Cascaded H-bridge multilevel inverter converts direct current to Alternating current, through inductor opposite harmonics are injected in Power Control Centre reduces source current harmonics and reactive power. The implementation of CHBMLI in distribution STATic COMpensator simulation model is simulated by means of MATLAB.

By using DSTATCOM, harmonic relevant power quality issues are rectified. For enhancing power quality at distribution supply, a novel control system implemented on frequency adaptive disturbance observer is proposed. Furthermore, it also eliminates the harmonics from nonlinear load Power quality issues in this system are bad power factor due to loads and more neutral current due to non-linear load as well as unbalanced loads. These are overcome by notch filter based control algorithm for DSTATCOM and therefore it alleviates power quality A novel control scheme for DSTATCOM (Distribution Static Compensator) considers reactive flow control in transmission system.

It is discussed a hybrid multilevel topology based on a cascaded single phase H-bridge converter with unequal dc voltage. A diode clamped H-bridge with multi output boost rectifier performs a high voltage converter fed by DC supplies and a low voltage converter fed by DC capacitor in a high voltage inverter. The clamped diode and rectifier raise the overall cost of the system. For cascaded hybrid H-bridge converters, fundamental frequency modulation is used.

For hybrid modulation, the selective harmonic elimination method is used. For hybrid multilevel converters, a new DC voltage control strategy Delta-type cascaded hybrid single-phase H-bridge topology is preferred due to its modularity and simplicity. Probabilistic Neural Network is balancing control is accomplished by injecting zero sequence current into the delta loop, and individual voltage control is accomplished by trimming the fundamental component. Because Probabilistic Neural Network modulation does not automatically ensure that the amount of reactive power from the grid terminal is distributed uniformly among all cell capacitors, they will be charged and discharged at different rates. To avoid this undesirable situation, individual cell modulation indices must be modified from the set point provided by the outer control loop.

Because of its modularity, ability to remove the transformer in medium voltage applications, and ability to reduce switching loss, a Cascaded H-Bridge Multilevel Converter (CHB-MC) is one of the most popular converter systems in many industrial applications. Although the CHB-MC has these benefits, the requirement for isolated DC power sources, which makes the system heavy, complex, and adds cost to each HB cell, is a disadvantage to consider. In the static synchronous compensator application, however, the requirement for isolated DC power sources is no longer a significant disadvantage because floating capacitors on the HB cells can replace the isolated DC sources.

Each cell has an isolating electrolytic capacitor. An inductor is also used in each cluster to support the difference between the sinusoidal source voltage and the ac pulse width modulation voltage, as well as to filter out switch ripples caused by high frequency modulation. Switching frequencies are assigned to high voltage converters and low voltage converters, respectively. The STATCOM control scheme is tasked with generating the desired amount of reactive power at the grid terminal while keeping the mean value of the cell capacitors’ voltage at a constant level. The top-level control is made up of two loops, as shown in the diagram below.

In distant region a number of distributed power generation systems are present. By using composite observer DSTATCOM is performed by means of induction generator based distributed power generation. The advantages of this scheme reduces cost, separate DC source is not required, when comparing to synchronous generator excitation current is less, maintenance is simple. This kind of scheme is only fit for portable isolated power generation system [

Under the state of light load, for maintaining constant DC potential needless potential stress occurs on switching devices. To overcome this drawback a dynamic DC potential regulation is suggested, it minimizes potential stress occurs on switching devices under the state of minimized load [

For improving transient behavior of Static Synchronous Compensator (STATCOM) a novel reactive current reference algorithm is proposed. The proposed algorithm improves transient behavior of closed-loop scheme among PI controller & reduces STATCOM reactive current ripples [

To compensate current relevant power quality problems Model Predictive Control (MPC) of Three-Phase Split Capacitor (TPSC) distribution static compensator with VIKOR technique is developed. The drawback of MPC is it has higher switching frequency. To mitigate this issue, one control is to repress potential divergence as well as another one minimizes switching frequency that involves cost function using weighting factors [

The output of DSTATCOM (Distribution Static Compensator) is Steady state which is obtained in reactive flow control. At distribution side power quality issues are harmonics, reactive power and unbalanced load. To overcome this drawback an immune feedback control algorithm for 3Φ DSTATCOM is proposed. This control algorithm proposed in DSTATCOM keeps load balanced and eliminates harmonics. Mitigation of power quality problems are instigated by using kernel incremental metal earning algorithm in DSTATCOM the drawbacks of DC-link potential overshoot and increase in time of DC-link potential is overcome by a double deadbeat-loop control scheme for DSTATCOM is presented. Advantages in this method are transient response is faster, design process is easy and less steady-state A novel application of Multiple Complex Coefficient Filter (MCCF) is presented. This filter removes harmonics and necessary elements on nonlinear load current A VFFRLS (Variable Forgetting Factor Recursive Least Square) based control scheme is suggested for distribution static compensator. The proposed control algorithm alleviates power quality issues namely harmonics, reactive power and unbalanced load by means of the proposed AVSF algorithm is instigated for distribution static compensator. This algorithm alleviates power quality problems are harmonics, enhances power factor under linear & non-linear load.

This work presents a seven level cascaded H-bridge inverter based DSTATCOM is employed to protect power quality problems in currents. DSTATCOM aid to enhance power factor and then it removes total harmonic distortion which is supplying from non-linear load. D–Q reference theory based hysteresis current controller is employed to generate reference current for the compensation of harmonics and reactive power, additionally Probabilistic Neural Network (PNN) classifier is used which easily separates exact harmonics. For keeping constant DC-link capacitor potential, Fuzzy logic control (FLC) is used. This controller decreases steady state time and reduces maximum peak overshoot. The Cascade H-Bridge Multilevel Inverter (CHBMLI) converts DC to AC, through inductor opposite harmonics are injected in PCC reduces source current harmonics and reactive power.

The block diagram of proposed 3Φ seven level cascaded H- bridge inverter is depicted in

A 3Φ AC supply is fed to linear and non-linear load. This non-linear load consists of inductance, capacitance as well as diode bridge rectifier. Due to these non-linear loads back

In DQ theory, the direct axis and quadrature axis component are determined by means of parks and clarks transformation. From this the exact harmonics are separated by means of PNN classifier. This classifier generates reference current and by using this classifier harmonics present component and pure component are determined. Meantime DC-link potential is connected in capacitor bank. For maintaining constant DC-link voltage, reference DC potential and actual DC potential are compared to fuzzy logic controller. Conventionally there is PI controller; drawbacks in PI (Proportional–Integral) Controller are it increases steady state time and maximum peak overshoot problems.

To overcome this issues fuzzy logic controller is used, this FLC decreases all problems. When comparing reference voltage,

The structure of cascaded H-bridge multilevel inverter contains (

The output voltage per phase for maximum value is represented as,

By presuming every H-bridge has an equal DC bus potential, i.e.,

The CHBMLI output potential is too represented as,

where,

Just like that the essential switching angles to be restricted are,

The following diagram represents shunt connected DSTATCOM which is implemented in 3Φ seven level cascaded H-bridge inverter as depicted in

A 3Φ seven level cascaded H- bridge inverter based distribution static compensator is implemented in this scheme. When comparing to previous inverter more gate signals are needed, however one of the most important benefit of proposed method is it reduces total harmonic distortion. The application of control scheme is this inverter produces VSI and therefore this voltage source inverter generates an AC which is in phase with supply potential. The waveform for potential in every phase of seven-level cascaded inverter contains seven leveled outputs with three H-bridges linked in cascade. Through coupling inductance every phase voltage is given to distribution lines, this form shunt connected distribution static compensator. From above diagram we know that

The design of DSTATCOM with dissimilar parameter analyzes the reactive power as well as harmonic compensation. From the source it draws lagging, leading, harmonic distortions as well as unbalancing load currents which are connected to linear, non-linear and unbalanced load. The performance of compensation in reactive power and harmonics are performed in shunt connected device and distribution static compensator provides current component also preventable.

The current equation is mathematically represents in

The basic block diagram of reference current generation is depicted in

The direct axis and quadrature axis current is needed for real and reactive power in this control scheme. The fundamental current component is obtained due to load current of low pass filter. Hence it requires only active power from the source otherwise it requires average DC component

The mathematical expression for transformation of current from

The inverse transformation from

Generally, the reference current for indirect control is evaluated by means of terminal voltage,

where, the terminal voltage of PCC is denoted as

The structure of PNN is depicted in

The features are removed by Trager Energy Operator (TEO) and OCSe compose of feature vector which is considered as PNN input. Transient features of Power Quality (PQ) disturbances are removed by OCSe. TEO reflects energy signals.

The compose of feature vector,

where,

Here, classification of window length is denoted as p this lays at 1/4 cycle, absolute amplitude of

The steps involved in PNN trained are,

A seven level cascaded H-bridge inverter is employed in DSTATCOM. It contains three H-bridges in every phase, three capacitors per phase and totally nine capacitors in seven level cascaded H-bridge inverter based DSTATCOM. For complete operation voltage across every capacitor is maintain balanced. Several methods are used to balance voltage across DC-link capacitors.

Conventionally PI controller is used, here steady state time increases. To overcome this limitation, FLC is used to keeps DC-link potential. In this method steady state time decreases. The equation for cascaded H-bridge DC capacitance is expressed as,

where,

This is the equation for proportional integral controller, this operates the system with capacitor potential will be equal to reference of DC link potential

Proportional integral controller has some drawback which is incapability to respond sudden changes in error signal (

The control signal output is obtained from inference engine by means of rule base fuzzy control having if-then rules. By means of rule base fuzzy control, error signal

Mathematical equation for error signal and change in error signal is expressed as,

Generally, the membership function presents one for every variable as three, five or seven sets. In this work seven sets are selected for representation of membership function in triangular form. Seven kinds of standard sizes in universe of speech are represented in

The value used in sets which depends on resolution and intervention of preferred modification. Generally, more than seven sets don’t have any improvement in dynamic performance of fuzzy logic.

This work clearly explains the working of proposed DSTATCOM topology using 3Φ seven level cascaded H-bridge inverter. This complete topology is developed in MATLAB simlink which is examined for linear as well as non-linear load. Here, cascaded H-bridge multilevel inverter based distribution static compensator operation as well as component design are presented. Different kinds of voltage and current waveforms are shown below representing total harmonic distortion.

A 3Φ source voltage AC waveform is depicted in

A 3Φ source current waveform is depicted in

The DC link capacitor potential waveform is depicted in

The DC link capacitor potential waveform using FLC is depicted in

A 3Φ AC current waveform in PCC is depicted in

The Source voltage and current total harmonic distortion waveform using proportional integral controller is depicted in

The Source voltage and current THD waveform using FLC is depicted in

The waveform of PCC potential and current is depicted in

The waveform of source voltage and current after compensation is depicted in

The

The

The shunt connected DSTATCOM based seven level cascaded H-bridge inverter is developed. The behavior of seven level cascaded H-bridge inverter using DSTATCOM is estimated for reactive power compensation, harmonic compensation under non-linear load. Distribution Static Compensator (DSTATCOM) aid to enhance power factor as well as it removes total harmonic distortion which is supplying from non-linear load. D–Q reference theory is employed to generate reference current for compensation of harmonics and reactive power, additionally Probabilistic Neural Network (PNN) classifier is used which easily separates exact harmonics. Conventionally proportional integral controller is employed to keeps DC-link capacitor potential, the drawbacks in PI controller is it increases steady state time and maximum peak overshoot. To overcome this drawback fuzzy logic controller is employed to maintain DC-link capacitor potential. Multilevel inverter converts DC to AC, through inductor opposite harmonics are injected to PCC and therefore in source current harmonics decreases, indirectly real power increases and reactive power decreases.