Page 122 - IJEEE-2022-Vol18-ISSUE-1

118 | Jasim & Jasim

signal (????????: produced by the droop controller) with the real The adjusted control parameters of the adopted M-grid

dq voltage components (Vd, Vq) at the input side [44]. are shown in Table I.

???? = (???????? + ????????/??) (???????? - ????) (21) TABLE I

???? = (???????? + ????????/??) (0 - ????) The adjusted control parameters.

(22) Description Symbol Nominal

A PI-based power control loop creates output d-q Sampling time value
Ts 40µsec.
reference current (Idref and Iqref) signals while comparing the
Nominal frequency Fnom 50Hz
active and reactive power with their reference values.
BESS Frequency droop (%) ?????? 0.5
?????????? = (???????? + ????????/??) (?? - ????????)
(23) BESS Voltage droop (%) ?????? 3
???????? 1.5
?????????? = (???????? + ????????/??) (?? - ????????) BESS power regulator proportional
(24) gain

Where ???????? and ???????? are the proportional and integral gains BESS power regulator integral gain ???????? 15
of the BESS voltage loop control, and for the power loop
control are ???????? and ????????. BESS current regulator proportional ???????? 0.2
gain
? Current Regulators
The Current Regulators are supplied with the Idref and BESS current regulator integral gain ???????? 15
Iqref reference currents. The regulators use the measured and BESS voltage regulator proportional ???????? 2
reference currents to generate the inverter's dq voltages (Vd
and Vq). It is worth noting that the regulators accomplish gain
high dynamical response by using feedforward computation.
On the control of grid-connected inverters, current control BESS voltage regulator integral gain ???????? 25
operates as an inner loop section. Both Id and Iq are regulated BESS PWM switching frequency Fsw 2700Hz
by separate PI controllers to track reference values Idref and
Iqref respectively. Proportional gain of synchronization ?????????? 0.015/2
The voltage references Vdrref and Vqrref are created by to distribution system
combining the output of the PI controller with the terminal
voltage in dq and the cross drop voltage in the inductor and Integral gain of synchronization to ?????????? 0.03/2
resistor Lff and Rff. These voltage references control the distribution system
Pulse Width Modulation (PWM), which generates the
appropriate command for the grid-connected inverter's Proportional gain of PV arrays ???????? 0.05
switches [44]. power regulator
???????????? = (???????? + ????????/??) (?????????? - ????) + ???? + ?????????? -
Integral gain of PV arrays power ???????? 2
regulator

PV current regulator proportional ?????????? 6
gain

PV current regulator integral gain ?????????? 30
?????????? 0.2
PV voltage regulator proportional
gain

PV voltage regulator integral gain ?????????? 15

PV PWM switching frequency Fsw 2340Hz

??????? ???? (25) 5) Faults Detection and Diagnostic Using DWT

???????????? = (???????? + ????????/??) (?????????? - ????) + ???? + ?????????? + Because of its ability to resolve high-frequency
components, the wavelet transform is one of the most
??????? ???? (26) preferred approaches for defect detection and classification.
[48–51].
Where ???????? and ???????? are the proportional and integral gains
Ingrid Daubechies (db), a Belgian mathematician,
of the BESS current loop control. developed the most widely used collection of discrete
wavelet transformations (DWT) in 1988. The utilization of
? Reference Voltage Generation recurrence relations to create increasingly smaller discrete
Vdrref and Vqrref are scaled and translated to a three- samplings of an implicit mother wavelet function underpins
phase reference signal Vref, which is sent into the PWM this concept.
modulator to generate pulses for the inverter.
A mathematical method for studying transitory signals
? Compensator for Imbalance is the wavelet transform. It is adopted here to detect and
When imbalance compensator activated, the imbalance classify the fault type. As shown in Fig. 12, DWT is a useful
compensator reduces the negative sequence voltage at the tool for analyzing time-varying, transient signal-like faults
PCC bus caused by grid load imbalance. It makes use of an by decomposing the signal into an Approximation (A) and
outer-loop dq voltage regulator as well as an inner-loop dq Detailed (D) coefficients using sequential high-pass and low-
current regulator. pass signal filtering [52].

4) Load The noise in the fault signal can be decreased as the
The 600V load is represented simply by a fixed three- number of decomposition levels grows. In this study, the
characteristics are extracted using a db4 mother wavelet with
phase load model (PQ) and a second switchable three-phase two layers.
load model (PQ).
By applying a signal (x) through a series of filters, the
DWT is determined. After passing the samples through a low