This article has been accepted for publication in a future issue of this journal, but has not been

fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TSTE.2017.2691279, IEEE
Transactions on Sustainable Energy
1

SSR Mitigation with a New Control of PV Solar

Farm as STATCOM (PV-STATCOM)
Rajiv K. Varma, Senior Member, IEEE, and Reza Salehi, Student Member, IEEE

utilized to alleviate subsynchronous resonance (SSR) since its

Abstract— This paper presents a novel control of a large scale first occurrence, including various filters, excitation system
PV solar farm as STATCOM, termed PV-STATCOM, for control and protection systems [8]. Flexible AC Transmission
alleviation of subsynchronous resonance (SSR) in a steam turbine System (FACTS) devices are known to be effective solutions
driven synchronous generator connected to a series compensated
transmission line. During nighttime, the PV solar farm can
for preventing SSR [9]-[24].
operate as a STATCOM with its entire inverter capacity for SSR The concept of damping SSR in turbine driven synchronous
mitigation. During daytime, if a system fault triggers SSR, the generators through reactive power modulation by shunt
solar farm autonomously discontinues its normal active power
generation and releases its entire inverter capacity to operate as
connected dynamic reactive power compensators is presented
PV-STATCOM for SSR prevention. Once the subsynchronous in [8], [11]-[15], and actually implemented in [16]. The
resonances are damped, the solar farm returns to its normal real concept has been further demonstrated for SSR mitigation by
power production. Electromagnetic transients studies using Static Var Compensators (SVC) in [13], [15] and by
EMTDC/PSCAD are performed to demonstrate that a solar farm
connected at the terminals of synchronous generator in the IEEE STATCOMs in [17], [18] in addition to several other
First SSR Benchmark system can damp all the four torsional publications. The essential concept is as follows. Reactive
modes at all the four critical levels of series compensation, and power from the dynamic reactive power compensator is
return to normal PV power production in less than half a minute.
This proposed PV-STATCOM technology can either obviate or
modulated in response to the turbine generator rotor
reduce the need of an expensive FACTS device to accomplish the oscillations causing a corresponding voltage modulation at the
same objective. Furthermore, this technology is more than an interconnecting bus. This modulation is performed in such a
order of magnitude cheaper than a conventional SVC or manner that subynchronous currents are made to flow into the
STATCOM of similar size.
armature of the turbine generator. These subsynchronous
Index Terms—PV solar system, Sub Synchronous Resonance currents are in phase opposition and tend to cancel the original
(SSR), series compensation, FACTS, STATCOM, PV- SSR causing subsynchronous currents caused by the
STATCOM, solar energy, smart inverter, power ramping interaction between series capacitors and transmission network
inductance.
I. INTRODUCTION
A Static Var Compensator (SVC) connected at the terminal
S ERIES capacitive compensation is an effective means for
increasing the power transfer capacity of transmission
lines. However, the potential of subsynchronous resonance
of the synchronous generator and utilizing a generator speed
based damping controller was shown to successfully damp
SSR for all the critical series compensation levels [13], [15]. A
(SSR) in such lines must be examined apriori and adequately generator bus connected STATCOM employing rotor speed
addressed [1]-[3]. SSR is an unstable electrical power system based auxiliary controller could successfully damp SSR [17].
condition that can manifest as steady state induction generator A nonlinear optimization based design of a subsynchronous
effect, torsional interaction or as transient torque amplification damping controller for STATCOM utilizing locally available
[2]-[3]. SSR resulted in damage to generator shaft in the steam STATCOM bus voltage and reactive current signals was
turbine driven synchronous generator in Mohave plant, proposed in [18] to suppress SSR in a system adapted from the
Nevada, USA, in 1970 and 1971 [1]. SSR was reported due to IEEE First SSR Benchmark System [25]. SSR alleviation has
adverse interaction between HVDC converter controls and also been proposed using other FACTS devices e.g., Thyristor
generator torsional system at Square Butte, North Dakota, Controlled Series Compensator [19], Static Synchronous
USA, in 1980 [4], [5]. Damaging over voltages due to Series Compensator SSSC [20-22] and Superconducting
subsynchronous interactions between Type 3 wind farms and Magnetic Energy Storage System (SMES) [23].
series compensated lines have also occurred in Texas [6], [7]. PV solar power systems are being increasingly employed
Several countermeasures have been investigated and worldwide to fulfil energy needs. Several large-scale PV solar
farms of rating in excess of 100 MW are operational and more
The financial support from NSERC, Canada, is gratefully acknowledged. are being planned. Most of these solar systems are connected
R. K. Varma and R. Salehi are with Department of Electrical and Computer to transmission systems. Some of the large PV solar farms are:
engineering, The University of Western Ontario, London, ON, Canada
Longyangxia Dam Solar Park (850 MW) in China, Solar Star I
N6G5B9 (e-mail: rkvarma@uwo.ca ; rsalehis@uwo.ca).

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2

and II (579 MW) in USA, Topaz Solar Farm and Desert 100

Sunlight Solar Farm (550 MW each) in California, USA; 90 Real Power

Huanghe Hydropower Golmud Solar Park (500 MW) in 80
Reactive Power

China, Charanka Solar Park (345 MW) in India, Agua Caliente 70

Solar Project (295 MW) in Arizona, USA; California Valley

Inverter output ( kW / kVar)

60
Solar Ranch (250 MW) in California, USA [26]-[29]. It is NIGHT NIGHT
50
important to note that the Agua Caliente Solar Project (290
40
MW) constructed by First Solar is connected to Hassayampa-
30
North Gila 500 kV transmission line that is series compensated
20
[29].
10
A new concept of using PV solar farms as a STATCOM
0
was proposed in 2009 [30], [31]. This concept termed PV- 12 AM 6 AM 12 PM 8 PM 12 AM

STATCOM utilized the entire capacity of PV inverter during STATCOM Partial STATCOM Partial STATCOM STATCOM

nighttime and the inverter capacity remaining after real power

Full STATCOM
production during daytime for performing various grid support
Fig. 1. Power output of a PV solar farm for 24 hours duration
functions, such as voltage regulation [30], increasing the
mode is completely available during nighttime. During
connectivity of neighboring wind farms [32], and enhancing
daytime, as soon as any subsynchronous resonance is sensed in
the power transmission capacity by damping power
the generator or in the transmission system, the solar farm
oscillations [33]. A limitation of this concept was that it could
autonomously discontinues its real power generation function
not be applied during noon time or hours when the solar farm
and releases the entire inverter capacity to operate as a
was producing its rated power output.
STATCOM with the SSR damping control. As soon as the
A new patent pending technology [34] is used in this paper
SSR are damped out, the solar farm returns to its normal real
to propose a comprehensive PV-STATCOM control whereby,
power generation mode of operation [34]. This entire
a solar farm can function as a full STATCOM both during
operation typically takes place over a less than 1 minute
night and anytime during the day, for mitigating SSR.
period. This mode can be invoked at any time during day even
Electromagnetic transient studies using EMTDC/PSCAD are
when solar farm is producing its rated output.
conducted to demonstrate that a PV solar farm connected at
the generator terminals with the proposed PV-STATCOM
III. STUDY SYSTEM
control successfully mitigates SSR for all the critical levels of
series compensation in a study system adapted from the IEEE Fig. 2 illustrates the study system in which the IEEE First
First SSR Benchmark System [25]. This is for the first time to SSR benchmark system [25] is augmented with a PV solar
the best of authors’ knowledge that a PV solar farm control is farm at generator bus. The mechanical system is modeled fully
being proposed for preventing SSR. by its six mass-spring system: the high pressure turbine (HP),
This paper is organized as follows: Section II presents the the intermediate pressure turbine (IP), the low pressure
concept of PV-STATCOM while Section III describes the turbines (LPA and LPB), the Generator (GEN), and the exciter
study system. Section IV explains the PV-STATCOM inverter (EXC). The mechanical damping is considered zero in all
control system for damping the subsynchronous resonances. modes to represent the worst damping condition [15]. This
EMTDC/PSCAD software based studies to demonstrate SSR radial system produces subsynchronous resonances with four
mitigation at different series compensation levels are presented torsional modes: 15.71 Hz (Mode 1), 20.21 Hz (Mode 2),
in section V. In Section VI, the potential of applying the novel 25.55 Hz (Mode 3), and 32.28 Hz (Mode 4).
PV-STATCOM control on large scale PV solar farms The synchronous generator and the entire network are
connected to power transmission systems is discussed. modeled in EMTDC/PSCAD software according to parameters
Conclusions of this paper are presented in section VII. provided in [25]. No AVR is considered on the synchronous
generator [25]. The synchronous generator although rated at
II. CONCEPT OF PV-STATCOM 892.4 MVA [25] is operated at 500 MW. However, a 300
MVA PV solar inverter is connected at generator bus to make
Fig.1 depicts the typical pattern of the PV solar farm power
the total power generation at the generating end match with
generation on a sunny day and the remaining reactive power
that in [25]. The series capacitive reactance (XC) of the system
capacity over a 24-hour period. Two modes of PV-STATCOM
is changed to excite the different torsional modes. The values
operation are illustrated in Fig. 1:
of XC (p.u.) for which different torsional modes have their
i) Partial PV-STATCOM mode: In this mode, the real
largest destabilization are as follows: Mode 1 (0.47 p.u.),
power generation continues unabated based on available solar
Mode 2 (0.38 p.u.), Mode 3 (0.285 p.u.), and Mode 4 (0.185
radiation. The inverter capacity left after real power generation
p.u.) [15].
is used for STATCOM operation. This mode is used during
The PV solar system is modeled with an equivalent voltage
daytime typically during early morning and late afternoon [33].
source inverter (VSI) comprising six insulated gate bipolar
ii) Full STATCOM mode: This mode utilizes the entire
transistor (IGBT) switches, and a dc current source which
capacity of the solar inverter to operate as a STATCOM. This
follows the I-V characteristics of PV panels of the PV solar

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TSTE.2017.2691279, IEEE
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farm system [33], [35]. With the utilization of a maximum possible to mitigate SSR by damping controllers utilizing
power point tracking (MPPT) algorithm, the PV solar farm electrical signals from the PCC, such as, PCC voltage [18] and
operates at its maximum power point in normal operation [36- line current [21], [39]. However, in this paper rotor speed
37]. A large dc capacitor is employed to hold the dc voltage deviation is selected as the control signal for the auxiliary SSR
approximately constant at the dc side of the inverter [38]. damping controller for the PV-STATCOM. This is because
rotor speed contains information about all the torsional modes
IV. INVERTER CONTROL SYSTEM of oscillation [13], [15]. It has further been shown to be an
STATCOM is a shunt connected VSI with the ability to effective signal to mitigate SSR by SVCs and STATCOMs
dynamically control reactive power with a rapid response time connected at the terminals of the turbine generator
(typically, 1-2 cycles) [9]. The proposed control of the PV [8],[12],[13],[15-17].
solar farm as PV-STATCOM is illustrated in Fig. 2. It is The DC voltage controller block including the Maximum
known that a STATCOM with voltage control alone is unable Power Point Tracking (MPPT) subsystem adjusts the dc side
to damp the torsional SSR oscillations and hence an auxiliary voltage of inverter to the desired value. The PV inverter
damping controller is required [10],[13],[15],[17]. It is control is based on the dq-reference frame model of
HP IP LPA LPB GEN EXC

A B Infinite Bus
Xl=j0.14 Xl=j0.5 Rl=j0.02 XC Xl=j0.06
PCC

Generator ZF

VSI PV Solar Farm

I pv

LCL Filter V DC

vabc iabc
abc
dq

ρ
ω PLL 6
Damping Controller iq id
∆ω
Block
idref md
PWM and Gate
ρ
Current-Control Block Drive
iqref mq
I pv
MPPT
DC Voltage controller Block
V DC

Fig. 2. Study system involving a PV solar farm connected at the synchronous generator terminal in the IEEE First SSR Benchmark System

VSI [33], [36-37]. The phase-locked loop (PLL) block is side current of VSI by using sinusoidal pulse width modulation
utilized to estimate the angle of the grid voltage [37]. The (SPWM) strategy [36]. According to Fig. 3, the id and iq (d-
voltage vector for dq-frame modeling is aligned with the axis and q-axis component of ac side current, respectively) are
quadrature axis, and therefore Vd equals zero. Thus the first compared with their reference values id-ref and iq-ref. The
reactive and active powers of VSI are controlled through the d- error signals are then processed by proportional integral (PI)
axis and q-axis loops, respectively. The damping controller controllers, and their corresponding outputs are augmented
block utilizes the generator speed signal to produce the d-axis with the decoupled feed forward signals [37]. The PI
reference current id-ref for current controller. By employing the controller parameters are tuned by a systematic hit-and-trial
dc side voltage and current, the DC Voltage controller block method to achieve the fastest step response, least settling time,
provides the q-axis reference current iq-ref. The current control and an overshoot less than 10% [33]. A decoupled feed
block subsequently controls the output current of the inverter, forward technique is utilized to decouple dynamics of d-axis
as described below. and q-axes, and improve the disturbance rejection ability of the
closed-loop system [37]. The resulting signals are normalized
A. Current Controller to produce the modulating indices md and mq, where, md and
The current-control loop as an inner loop is shown in Fig. mq respectively, represent the d-axis and q-axis components of
3. The function of the current-control loop is to regulate the ac the three-phase PWM modulating signal (mabc). Finally, md and

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mq are converted to mabc and compared with a high-frequency this paper is to demonstrate a new concept of SSR mitigation
triangular wave to generate the proper IGBT switching signals. by PV solar farms control as STATCOM (PV-STATCOM), a
An LCL filter attenuates the VSI ac side switching ripple, and simpler controller parameter selection through systematic trial-
provides current and voltage with low distortion for the system and-error method was chosen.
through a coupling transformer [40], shown in Fig. 2.
Washout
sT ω ∆ω 180o phase
vsd ω K idref
1 + sT ω shift

id-ref K I1
K P1 + Fig. 4. Damping Controller Configuration.
s Vtd md
Decoupling Feed-Forward
id Ls
C. DC Voltage Controller
VDC Fig. 5 (a) illustrates the conceptual dc voltage controller. It
ω0
2 is comprised of the MPPT block, and a PI controller. The
iq Ls MPPT block is simulated in EMTDC/PSCAD software based
on an incremental conductance algorithm [43]. The MPPT
Vtq block produces Vdc-ref to control the active power generated by
KI2
mq PV solar farm. The measured dc voltage is compared with
iq-ref KP2 +
s Vdc-ref to create an error signal. The PI controller processes this
error signal and generates the q-axis reference iq-ref for the
vsq current loop controller. The PI controller parameters are tuned
Fig. 3. Current-Control block diagram by a systematic hit-and-trial method in the same manner as the
PI controller of the current-loop controller.
The flow chart of the proposed DC voltage controller for
B. Damping Controller PV-STATCOM operation is portrayed in Fig. 5(b). The DC
Fig. 4 illustrates the configuration of the proposed SSR voltage controller constantly monitors if the system is
damping controller of the PV-STATCOM. Since it is intended operating in a healthy manner and no SSR are initiated i.e., the
to utilize the entire STATCOM inverter capacity only for rotor speed deviation ∆ω is less than a pre-specified quantity
damping SSR, the voltage controller typically employed in the which is chosen to be 1 rad/sec. In this case, the Full PV-
STATCOM is not implemented. STATCOM mode is not activated and the system operates in
The damping controller utilizes generator speed signal for normal PV power generation mode with Vdc-ref set to VMP, the
damping SSR. The PV-STATCOM is connected at the maximum power point voltage. If SSR are caused due to any
terminals of the turbine driven synchronous generator. It is system disturbance or fault, and the rotor speed deviation ∆ω
therefore expected that the generator rotor speed signal will exceeds 1 rad/sec, the Full PV-STATCOM mode is initiated.
become available to the PV-STATCOM control without any This is accomplished by setting Vdc-ref to Voc which is the open
appreciable delay. This is the approach adopted by almost all circuit voltage of the solar panels. The active power generated
the papers dealing with SSR mitigation by Flexible AC by the solar panels is made to go to zero and the entire inverter
Transmission System (FACTS) devices connected at the capacity is released for STATCOM operation to damp SSR.
terminals of the turbine generators [13], [15-17], [23-24]. Once the SSR are mitigated, i.e., ∆ω<1 rad/s, the DC
Hence, the same approach has also been adopted in this paper.
voltage controller gradually resumes normal solar power
The generator speed is continuously measured and passed
generation by decreasing the dc voltage to its pre-fault value
through the washout block to obtain the generator speed
VMP in a ramped manner [44-46]. Simultaneously, the partial
deviation which reflects the SSR occurring in the generator. It
PV-STATCOM mode is enabled. In this mode while the real
is enhanced by a gain factor K and phase shifted by 180o to
power generation is being ramped up, damping of SSR is
produce the d-axis reference id-ref for the current loop
continued with the inverter capacity remaining after real power
controller. This controller produces id-ref in a manner that the
generation. This ensures that the PV power can be restored to
corresponding PV-STATCOM reactive power exchange can
its prefault value without causing resumption of SSR. This
damp the subsynchronous resonances.
ramp-up of power with SSR damping control in operation is
The best controller parameters are obtained through a
another novel contribution of this paper which has not been
systematic hit-and-trial method to result in a minimal settling
reported earlier. Once Vdc becomes equal to VMP, the partial
time and acceptable over shoot (less than 10%) in generator
PV-STATCOM operation is disabled and Full PV power
speed [31]. There are analytical approaches to design the
generation is resumed.
damping controllers by FACTS devices such as [17], [18],
[21], [41] and [42], which are more efficient than gain
selection through trial and error. However, as the objective of

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∆ω

I VDC-ref
pv
KI3
K P3 + iqref
+ s
V DC

(a)

Start

t=t0

No Is PV system in Yes
Full PV-STATCOM
mode?

Yes No No Yes
t=t0+∆t |∆ω|<1 rad/s t=t0+∆t |∆ω|<1 rad/s

Decrease VDC from VOC

Full PV-STATCOM to VMP with ramp;
Follow MPPT
mode initiated; Enable
VDC-ref = VMP
VDC-ref = VOC Partial PV-STATCOM
operation

Disable Partial t=t0+∆t

PV-STATCOM
operation; Return to Yes No
normal PV power VDC = VMP
generation

(b)
Fig. 5. (a) DC voltage controller (b) Flowchart of DC voltage controller
operation
Fig. 6. System response for Mode 1 SSR without PV-STATCOM controller.
V. ELECTROMAGNETIC TRANSIENTS STUDY OF SSR DAMPING
system response for the series compensation level when Mode
Studies for damping subsynchronous resonances using PV-
1 is critically excited. The responses of the PCC rms voltage,
STATCOM control are now performed using
PV-STATCOM reactive power; generator real and reactive
EMTDC/PSCAD software. These studies are reported for the
powers, rotor speed, and the torque in the LPB-GEN section
most stringent case when both the synchronous generator and
are depicted. It is evident from this study that the system
the PV solar system are producing their rated power
becomes highly unstable due to SSR.
representing a similar power flow as [25]. A three-line-to-
ground (3LG) fault for five cycles is initiated at bus B at t=5 According to the Voltage Ride Through criteria of existing
sec. These fault studies are performed for four critical levels of grid codes and Standards, the PV solar farm must be
series compensation when the four respective torsional disconnected due to its large voltage excursions.
oscillatory modes are most undamped, as described in [15], For instance, NERC standard “PRC-024-2” [47] requires
[25]. Due to space considerations, the detailed responses are the generating unit to have the capability of Voltage Ride-
reported only for the damping of Modes 1 and 4, which are Through (VRT). Based on voltage ride-through time duration
more destabilized as compared to Modes 2 and 3. curve and Table in Attachment 2 of this Standard, whenever
Fig. 6 depicts the postfault behaviour of the study system the PCC voltage goes under 0.65 pu for a duration more than
when the solar farm functions normally and is not controlled
0.3 sec the generating unit should be disconnected from the
as the proposed PV-STATCOM. This figure illustrates the
grid. Furthermore, whenever the voltage goes above 1.2 pu the

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generating unit should be tripped instantaneously. As evident

from Fig. 6 of the paper, the PCC voltage after the occurrence
of the fault goes under 0.65 pu for a duration of 0.8 second.
Therefore the PV solar farm should be disconnected at t=5.835
sec. In addition, the voltage goes above 1.2 pu at t=5.86 sec,
which is another criterion for the solar farm to be disconnected
at t=5.86 sec, although the previous criterion will take
precedence for disconnection.
ERCOT Nodal Operating Guides [48] needs all intermittent
renewable resources (IRR) to conform to Voltage Ride
Through requirements. Based on Figure 1 of Section 2 of this
operating guide, the IRR shall be disconnected whenever the
PCC voltage goes under 0.6 pu for 1.25 sec, or immediately
whenever it goes above 1.2 pu. Therefore, based on ERCOT
Nodal Operating Guides and Fig. 6, the PV solar farm shall be
disconnected at t= 5.86 sec when the PCC voltage goes above
1.2 pu.
It is therefore emphasized that the solar farm will anyway be
disconnected due to the VRT criterion of the grid codes, and
not because of the proposed PV-STATCOM control. The
issues of load frequency control will arise, but that will be
need to addressed by the system operator. This is outside the
scope of this paper.
It is shown in the next section that the novel proposed PV-
STATCOM control goes a step beyond, and instead of
remaining idle in the disconnected mode, utilizes its inverter
capacity to successfully damp SSR. This control further
returns the solar farm to its normal prefault power production Fig. 7. PV-STATCOM response for damping of Mode 1 SSR.
and restores the system frequency to its nominal value. It
of the involved controllers. The entire capacity of the
performs this function autonomously without any support from
inverter is thereby made available for the Full PV-STATCOM
the system operator. Without this proposed control, the system
operation for SSR damping. The rotor oscillations are
will become unstable and the system operator will have to take successfully damped to within 1 rad /sec at t= 9.68 sec. Once
due measures to restores system stability and frequency. this occurs, the PV solar farm restarts power generation by
A. Damping of Mode 1 (67% series compensation) decreasing the dc voltage in a ramped manner, while
continuing to damp SSR in the Partial PV-STATCOM mode
The stabilizing impact of SSR damping control of the PV-
of operation. The prefault level of power generation is
STATCOM is now investigated. Fig. 7 depicts the different
achieved without any voltage/power oscillations in about 5
PV-STATCOM variables which include Inverter active power
seconds at t=14.68 sec. The entire process of damping Mode 1
P, reactive power Q, apparent power S, dc side current IPV and
SSR takes only 9.68 sec utilizing a maximum of 200 Mvar
the dc side voltage VDC. Fig. 8 illustrates the different
STATCOM reactive power.
synchronous generator variables for this case, which include
It is observed from Fig. 8 that torsional oscillations occur
the active power, reactive power, generator speed ω, and in all the mechanical sections, however, the highest torque in
torques between HP-IP, IP-LPA, LPA-LPB, LPB-GEN, and excess of 4 pu is experienced in the LPA-LPB shaft section.
GEN-EXC sections, respectively. The corresponding The PV-STATCOM successfully damps the SSR in the entire
transmission system parameters for this case study are torsional system. It is noted from Fig. 9 that during the
portrayed in Fig. 9. These consist of rms voltage at PCC, damping operation of Mode 1 by PV-STATCOM operation,
active power flow and reactive power flow. the line active power reduces as the power output of the solar
As soon as the onset of SSR in rotor speed is sensed at t=5 farm is made to go to zero but subsequently returns to the
sec by the damping controller, the dc voltage controller prefault value. The PCC voltage rises slightly above 1 pu
increases the dc bus voltage to its open circuit value VOC to during the transient.
make the inverter active power P and the dc current IPV go to
zero, however, with a slight delay based on the time constant

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Fig. 9. Transmission system response for damping of Mode 1 SSR

The grid codes further specify a range for the rate at which
the power may be ramped up depending upon system
characteristics. A typical specification is that the increase in
active power supplied to the network by the power source must
not exceed a maximum gradient of 10% of the agreed active
connection power per minute [46]. The appropriate ramp-rate
for a specific system may be determined from off-line system
studies.
This paper has proposed a novel fast method of
reconnection of PV solar farm while keeping the PV-
STATCOM SSR damping function activated. It is
demonstrated from Figs. 7-9 that with this proposed technique
the active power can be ramped up from zero to 300 MW in
about 5 seconds without resumption of SSR.
To demonstrate the effectiveness of this proposed technique
a new study is performed. In this study, after SSR has been
mitigated and the generator rotor speed has stabilized to within
acceptable limits at t = 10 sec in Figs 7-8, the power ramping
up is performed without the PV-STATCOM damping function.
The ramp-up rate is slowed down three times, i.e. the power is
ramped up from zero to 300 MW over 15 sec instead of 5 sec
as in Figs.7-8 with PV-STATCOM damping control in
operation. Fig. 10 portrays the response of real power of the
synchronous generator, the active power of solar farm, and
generator rotor speed. The system is seen to become unstable
due to recurrence of SSR. This clearly shows the efficacy of
the proposed ramp up with PV-STATCOM damping control
Fig. 8. Synchronous generator response for damping of Mode 1 SSR
active.

C. Damping of Mode 2 (54% series compensation)

B. Ramp up without the Proposed PV-STATCOM control
In this case study, the fault is initiated as before at t=5 sec.
Grid codes such as [44-46] stipulate that active power
The PV-STATCOM damps the torsional oscillations (∆ω<1
sources including PV solar farms should ramp up their power
rad/s) at t=7.96 sec, and the solar power output is restored to
output slowly during the connection process in order to avoid
its prefault value without any SSR at t=12.96 sec. Thus the
voltage or power oscillations due to the sudden injection of a
total time required for SSR alleviation is 7.96 sec.
large amount of active power into the grid.

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Fig. 10. System response for Mode 1 SSR without damping controller
during ramp up

The maximum PV-STATCOM reactive power needed for

this purpose is about 200 Mvar.

D. Damping of Mode 3 (41% series compensation)

In this case study, the fault is initiated as before at t=5 sec.
The PV-STATCOM damps the torsional oscillations (∆ω<1
rad/s) at t=6.81 sec, and the solar power output is reinstated to
its prefault value without any SSR at t=11.81 sec. Thus the
total time required for SSR alleviation is 6.81 sec. The
maximum PV-STATCOM reactive power needed for this
purpose is also about 200 Mvar.
E. Damping of Mode 4 (26% series compensation)
For this case, Fig. 11 illustrates the PCC rms voltage, PV-
STATCOM reactive power; generator real and reactive Fig. 11. System response for damping of Mode 4 SSR
powers, rotor speed, and the torque in the LPB-GEN section.
The PCC bus voltage is about 1.05 pu, which is higher than in
the case of Mode 1 damping (Fig. 8). This is because during VI. DISCUSSIONS
the PV-STATCOM operation, when PV solar system does not
generate any real power, the synchronous generator reactive A. Impact of PV Solar Farm Shutdown and Ramp up on Grid
power is largely capacitive, as opposed to being largely Frequency during PV-STATCOM operation
inductive as in case of Mode 1 damping (Fig. 8). In general, both the outage and ramping up of a large
The maximum subsynchronous torque of about 3 pu is amount of PV solar power may potentially impact the
experienced in the LPB-GEN section. The PV-STATCOM frequency of the grid. However, these impacts will depend
successfully mitigates all the torsional oscillations (∆ω<1 upon the size of the PV solar system in comparison to the
rad/s) at t= 6.77 sec, and the solar power output is restored to overall power generation in the grid, the duration of the outage
its prefault value without any SSR at t=11.77 sec. Thus the of solar power, and the rate of ramping up (in case of
total time required for SSR alleviation is 6.77 sec. The reconnection). These impacts can only be determined after due
maximum PV-STATCOM reactive power needed for this studies are performed for the concerned power system.
purpose is about 200 Mvar. A significant number of research studies on SSR mitigation
including [15, 17] have been conducted on the IEEE First SSR
Benchmark system [25]. In this paper also, the effectiveness of
the proposed PV-STATCOM for SSR alleviation has been
examined on a system similar to the IEEE First SSR

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TSTE.2017.2691279, IEEE
Transactions on Sustainable Energy
9

Benchmark system. For this system, the size of PV solar farm may be in close vicinity of synchronous generators that may be
(300 MW) is about a third in comparison to the rating of SSR prone. For instance, the 290 MW Agua Caliente Solar
synchronous generator (892 MVA). With the large voltage Project constructed by First Solar is connected to Hassayampa-
deviations experienced during the onset of SSR, the PV solar North Gila 500 kV transmission line that is series compensated
farm will need to be shut down in accordance with the
[29].
transmission grid codes such as [46] and wait for reconnection
Considering the above growing developments of large solar
till the SSR has been mitigated by other mechanisms. This
farms and their possible connection in series compensated
paper proposes a novel concept that instead of being shut
lines, such large solar farms can potentially become candidates
down the solar farm performs SSR mitigation and returns to its
for implementation of PV-STATCOM SSR damping function.
full prefault solar power production within a period of less
While synchronous generator based devices and other
than 10 sec.
mechanisms for damping SSR do exist, FACTS device based
It is clearly seen that the shutdown of the PV solar farm to
SSR mitigation measures have been widely utilized and
transform into a PV-STATCOM does not have any significant
reported in literature [9-24]. Therefore in cases where
effect on the grid frequency. It is evident from Fig. 8 that the
generator-based SSR damping devices are not considered or
maximum deviation of the generator speed (representative of
found to be inadequate, the PV-STATCOM technology can
the system frequency) caused by the combined effect of SSR in
become both economic and feasible solution for SSR
synchronous generator and outage of 300 MW solar power
mitigation.
output for a duration of 10 seconds is just about 7 rad/s.
An important aspect to consider is that the proposed PV-
It is however recommended to check that the PV-
STATCOM is expected to be more than an order of magnitude
STATCOM control while damping SSR does not cause any
cheaper than a conventional STATCOM. This is because only
adverse impact on system frequency if implemented in any
an incremental PV-STATCOM SSR damping controller with
other large power system.
its associated measurement circuitry needs to be installed on
Another novel contribution of this paper is performing
the existing infrastructure (the substation, bus-work,
active power ramping from zero to 300 MW in 5 seconds
transformers, circuit breakers, protection systems, etc.) of a PV
while keeping the PV-STATCOM damping function activated
solar farm to transform it into a full scale STATCOM of
without the recurrence of SSR. This rate of ramping up is
similar size.
significantly faster than that specified in grid codes such as
It is understood that a simplistic approach has been adopted
[46] to prevent system oscillations in which any kind of
in this paper by considering an equivalent 300 MVA inverter
damping function during ramp up is not envisaged.
While it is recommended that adequate studies be conducted instead of possibly hundreds of inverters in an actual solar
to determine frequency deviations in study systems in farm of such size with their associated controls,
question, it is concluded based on this study that a PV solar communication and protection systems. However, the
farm equipped with PV-STATCOM control can provide a objective of this paper is to demonstrate the concept of a novel
valuable service of SSR mitigation without causing any technology of alleviating SSR with PV solar systems, which to
appreciable impact on the system frequency in the IEEE First the best of authors’ knowledge has not been reported before.
SSR Benchmark system. The significant potential financial saving in adoption of PV-
STATCOM in lieu of an actual STATCOM can certainly be a
motivation to overcome the intricacies involved in
B. Potential of Utilizing Large Scale PV Solar Farms for
implementation of this novel technology in a coordinated
Damping Subsynchronous Resonance
manner on the multiples of inverters in an actual solar farm of
With increasing electrical power generation to meet the load similar size.
demand, series compensation of lines is expected to be
increasingly considered as an economical alternative to VII. CONCLUSION
construction of new transmission lines, worldwide. This is
Rapidly emerging, large utility scale PV solar farms are
likely to make the associated generation systems more prone to
likely to find themselves being connected in transmission
SSR issues. On the other hand, due to the rapid adoption of
systems that are series compensated. This paper presents a
renewable energy systems coupled with the drop in PV panel
novel patent-pending concept of autonomously controlling
prices, large scale PV solar farms with rating in excess of 100
such large utility scale PV solar farms as STATCOM, termed
MW are increasingly being deployed in transmission systems
PV-STATCOM, for mitigating subsynchronous resonance
worldwide [26]-[29]. Furthermore, these sizes of large utility
(SSR) in steam turbine driven synchronous generators
scale solar farms are becoming comparable to transmission
connected to series compensated transmission lines. The
level shunt connected FACTS devices such as, Static Var
proposed PV-STATCOM control provides solar farm the
Compensators and STATCOMs. It is understood that large
capability to mitigate SSR both in the night and anytime
scale PV solar farms may be installed at locations which will
during the day. In the night, since the solar farm is idle, the
be determined from non-technical considerations, such as
entire inverter capacity is utilized for PV-STATCOM
availability of cheap land, etc. However, it is quite a possibility
operation. During the day, at any time, if SSR is triggered due
that such transmission connected solar farms may be
to any system disturbance, the solar farm autonomously
connected in networks that are series compensated and also

1949-3029 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TSTE.2017.2691279, IEEE
Transactions on Sustainable Energy
10

discontinues its normal real power generation function and its rotor oscillation information with the PV solar farm. It is
transforms into a STATCOM with the full inverter capacity for expected and also proposed that appropriate agreements
SSR mitigation. Once the subsynchronous resonances are among the synchronous generator owner, concerned utility,
reduced below an acceptable level, the solar farm system operator, solar farm owner and the inverter
autonomously returns to its prefault real power generation manufacturer may be made to implement such a cost-effective
level in a ramped manner. solution.
Studies are conducted on the IEEE First SSR Benchmark The grid codes are presently being revised to accommodate
system [25] having a large 300 MVA solar farm connected at smart inverter functions. It is recommended that this smart
the generator terminals producing its rated power, to simulate SSR alleviation function with PV solar farms controlled as
similar study conditions as in [25]. The PV-STATCOM SSR PV-STATCOM be incorporated in the emerging grid codes.
damping control utilizing generator rotor speed as the control Mechanisms should also be evolved for compensating the PV
signal is developed in d-q frame of reference. solar farms financially for this very important service of SSR
PSCAD/EMTDC based electromagnetic transients simulation mitigation.
studies are conducted for all the four critical levels of series
compensation [25]. The following conclusions are drawn: APPENDIX
1) The PV-STATCOM successfully mitigates all the four Parameters of different controllers:
torsional modes at all the four critical levels of series Current Controller: KP1=1, TI1= KP1/KI1=0.0015, KP2=1, TI2=
compensation. KP2/KI2= 0.001; Damping controller: Tω= 0.006631, K=150;
2) The total time taken by the PV-STATCOM from the DC voltage controller: KP3=2, TI3= KP3/KI3= 0.05
autonomous initiation of damping control to mitigate the
different subsynchronous mode oscillations and return to pre- REFERENCES
fault normal solar power production is: 9.68 sec for Mode 1, [1] D. N. Walker, C. E. J. Bowler, R. L. Jackson, and D. A. Hodges, "Results
7.96 sec for Mode 2, 6.81 sec for Mode 3 and 6.77 sec for of subsynchronous resonance test at Mohave," IEEE Trans. Power
Mode 4, oscillations respectively. Apparatus and Systems, vol. 94, pp. 1878-1889, 1975.
[2] P. M. Anderson, B. L. Agrawal, and J. E. Van Ness, Subsynchronous
This time of interruption of PV solar power generation is
resonance in power systems: Piscataway, NJ, USA: IEEE Press, 1990.
comparable to a cloud passing event. [3] K. R. Padiyar, Analysis of subsynchronous resonance in power systems:
3) The PV-STATCOM reactive power required to damp SSR Norwell, MA, USA: Kluwer, 1999.
for all the critical series compensation levels in this study is [4] M. Bahrman, E. V. Larsen, R. J. Piwko, and H. S. Patel, "Experience
with HVDC - Turbine-Generator Torsional Interaction at Square Butte,"
less than 200 Mvar. IEEE Trans. Power Apparatus and Systems, vol. PAS-99, pp. 966-975,
4) The novel concept of ramping up keeping the SSR damping 1980.
function of PV-STATCOM activated allows a ramp-up rate [5] K. Mortensen, E. V. Larsen, and R. J. Piwko, "Field Tests and Analysis
of Torsional Interaction Between the Coal Creek Turbine-Generators and
much faster than that specified in grid codes without the CU HVdc System," IEEE Trans. Power Apparatus and Systems, vol.
resurgence of SSR. PAS-100, pp. 336-344, 1981.
The studies demonstrate that the proposed PV-STATCOM [6] “Sub-synchronous interaction between series-compensated transmission
lines and generation,” [Online]. Available:
control on large utility scale PV solar farms can successfully http://www.nerc.com/files/LL_45_Sub-Synchronous Interaction.pdf
mitigate potentially dangerous subsynchronous resonances in [7] M. Sahni, D. Muthumuni, B. Badrzadeh, A. Gole, and A. Kulkarni,
synchronous generators connected to series compensated lines. "Advanced screening techniques for Sub-Synchronous Interaction in
The PV-STATCOM control can potentially obviate the need wind farms," in Proc. 2012 IEEE PES Transmission and Distribution
Conference and Exposition, 2012, pp. 1-9.
for installation of an expensive SVC or STATCOM connected [8] IEEE Subsynchronous Resonance Working Group, “Countermeasures to
to the generator terminals for the same purpose. Subsynchronous Resonance Problems”, IEEE Trans. Power Apparatus
Under the current power market situation, the owner of and Systems, Vol. PAS-99, No.5, pp. 1810 - 1818, 1980
[9] N. G. Hingorani and L. Gyugi, Understanding FACTS: Piscataway, NJ,
synchronous generator normally may not want to share such USA: IEEE Press, 2000.
confidential information about rotor oscillations to other [10] R. M. Mathur and R. K. Varma, Thyristor-based FACTS controllers for
generation owner such as the PV solar farm which is a electrical transmission systems: John Wiley & Sons, 2002.
[11] O. Wasynczuk, "Damping Subsynchronous Resonance Using Reactive
competitor in the market. Power Control," IEEE Trans. Power Apparatus and Systems, vol. PAS-
However, this paper proposes a new concept by which the 100, pp. 1096-1104, 1981.
PV solar farm can provide SSR mitigation for the synchronous [12] T.H. Putman and D.G. Ramey, “Theory of the Modulated Reactance
Solution for Subsynchronous Resonance”, IEEE Trans. Power
generator in a highly cost effective manner as compared to the
Apparatus and Systems, Vol. 101, No.6, pp 1527-1535, Jun. 1982
installation of a FACTS device exclusively for the purpose of [13] N. C. Abi-Samra, R. F. Smith, T. E. McDermott, and M. B. Chidester,
SSR alleviation, assuming both are connected close to the "Analysis of Thyristor-Controlled Shunt SSR Countermeasures," IEEE
terminals of the synchronous generator. Trans. Power Apparatus and Systems, vol. PAS-104, pp. 583-597, 1985.
[14] L. Gyugyi, “Fundamentals of Thyristor-Controlled Static Var
In the proposed concept, the solar farm is not acting as a Compensators in Electric Power System Applications”, IEEE Special
competitor to the synchronous generator. Instead it is Publication 87TH0187-5-PWR, ‘Application of Static Var Systems for
providing a very valuable service in form of protection against System Dynamic Performance’, 1987, pp.8-27
[15] A. E. Hammad and M. El-Sadek, "Application of a Thyristor Controlled
shaft damages in the synchronous generator due to SSR. The Var Compensator for Damping Subsynchronous Oscillations in Power
synchronous generator will therefore not be averse to sharing

1949-3029 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TSTE.2017.2691279, IEEE
Transactions on Sustainable Energy
11

Systems," IEEE Trans. Power Apparatus and Systems, vol. PAS-103, pp. [39] C. Chen, O. Wasynczuk, and N. A. Anwah, "Stabilizing subsynchronous
198-212, 1984. resonance using transmission current feedback," IEEE Transactions on
[16] D.G. Ramey, D.S. Kimmel, J.W. Dorney and F.H. Kroening, “Dynamic Power Systems, vol. 1, pp. 34-41, 1986.
Stabilizer Verification Tests at the San Juan Station”, IEEE Trans. [40] J. L. Agorreta, M. Borrega, Lo, x, J. pez, and L. Marroyo, "Modeling and
Power Apparatus and Systems, Vol.100, pp. 5011-5019, Dec. 1981 Control of N-Paralleled Grid-Connected Inverters with LCL Filter
[17] K. V. Patil, J. Senthil, J. Jiang, and R. M. Mathur, "Application of Coupled Due to Grid Impedance in PV Plants," IEEE Trans. Power
STATCOM for damping torsional oscillations in series compensated AC Electronics, vol. 26, pp. 770-785, 2011.
systems," IEEE Trans. Energy Conversion, vol. 13, pp. 237-243, 1998. [41] E. V. Larsen, J. J. Sanchez-Gasca, and J. H. Chow, "Concepts for design
[18] K. R. Padiyar and N. Prabhu, "Design and performance evaluation of of FACTS controllers to damp power swings," IEEE Trans. Power
subsynchronous damping controller with STATCOM," IEEE Trans. Systems, vol. 10, pp. 948-956, 1995.
Power Delivery, vol. 21, pp. 1398-1405, 2006. [42] C. C. Yu, Z.; Ni, Y.; Zhong, J., "Generalised eigenvalue and complex-
[19] W. Zhu, R. Spee, R. R. Mohler, G. C. Alexander, W. A. Mittelstadt, and torque-coefficient analysis for SSR study based on LDAE model," IEE
D. Maratukulam, "An EMTP study of SSR mitigation using the thyristor Proceedings: Generation, Transmission and Distribution, vol. 153, pp.
controlled series capacitor," IEEE Trans. Power Delivery, vol. 10, pp. 25-34, 2006.
1479-1485, 1995. [43] K. H. Hussein, I. Muta, T. Hoshino, and M. Osakada, "Maximum
[20] G. N. Pillai, A. Ghosh, and A. Joshi, "Torsional interaction studies on a photovoltaic power tracking: an algorithm for rapidly changing
power system compensated by SSSC and fixed capacitor," IEEE Trans. atmospheric conditions," IEE Proceedings Generation, Transmission
Power Delivery, vol. 18, pp. 988-993, 2003. and Distribution, vol. 142, pp. 59-64, 1995.
[21] R. Thirumalaivasan, M. Janaki, and N. Prabhu, "Damping of SSR Using [44] “Common Functions for Smart Inverters, Version 3”, EPRI Palo Alto,
Subsynchronous Current Suppressor With SSSC," IEEE Trans. Power CA, Report No. 3002002233, Feb. 2014
Systems, vol. 28, pp. 64-74, 2013. [45] “Recommendations for Updating the Technical Requirements for
[22] M. Bongiorno, L. Angquist, and J. Svensson, "A Novel Control Strategy Inverters in Distributed Energy Resources”, Smart Inverter Working
for Subsynchronous Resonance Mitigation Using SSSC," IEEE Trans. Group Recommendations, California, January 2014
Power Delivery, vol. 23, pp. 1033-1041, 2008. [46] Technical Guideline: Generating Plants Connected to the Medium
[23] W. Chi-Jui and Y. S. Lee, "Application of simultaneous active and Voltage Network”, BDEW, 2008, available online:
reactive power modulation of superconducting magnetic energy storage https://www.bdew.de/internet.nsf/id/A2A0475F2FAE8F44C125783000
unit to damp turbine-generator subsynchronous oscillations," IEEE 47C92F/$file/BDEW_RL_EA-am-MS-Netz_engl.pdf
Trans. Energy Conversion, vol. 8, pp. 63-70, 1993. [47] “Reliability Standards for the Bulk Electric Systems of North America”,
[24] R. M. I. Hamouda, M. R.; Hackam, R., "Torsional oscillations of series North American Electric Reliability Corporation, 2017. available online:
capacitor compensated AC/DC systems," IEEE Trans. Power Systems, http://www.nerc.com/pa/Stand/Reliability%20Standards%20Complete
vol. 4, pp. 889-896, 1989. %20Set/RSCompleteSet.pdf
[25] IEEE Committee Report, “First benchmark model for computer [48] “ERCOT Nodal Operating Guides”, Electric Reliability Council of
simulation of subsynchronous resonance,” IEEE Trans. on Power Texas, 2015, available online:
Apparatus and Systems, vol.96, no.5, pp. 1565-1572, Sept. 1977. http://www.ercot.com/mktrules/guides/noperating/cur
[26] PV Resources, Large scale photovoltaic power plants ranking 1-50.
[Online]. Available:
BIOGRAPHY
http://www.pvresources.com/en/pvpowerplants/top50pv.php#notes
[27] Sunpower, Solar Projects, Solar Star Projects.[Online]. Available: Rajiv K. Varma (M'90-SM'09) obtained B.Tech.
http://us.sunpower.com/utility-scale-solar-power-plants/solar-energy- and Ph.D. degrees in Electrical Engineering from
projects/solar-star-projects/ Indian Institute of Technology (IIT), Kanpur,
[28] First Solar Projects. [Online]. Available: India, in 1980 and 1988, respectively. He is
http://www.firstsolar.com/About-Us/Projects.aspx currently a Professor with The University of
[29] First Solar Projects, Agua Caliente Solar Project . [Online]. Available: Western Ontario, London, ON, Canada. He was
http://www.firstsolar.com/About-Us/Projects/Agua-Caliente-Solar- the Hydro One Chair in power systems
Project engineering with The University of Western
[30] R. K. Varma, V. Khadkikar, and R. Seethapathy, “Nighttime application Ontario from 2012 to 2015. Prior to this position,
of PV solar farm as STATCOM to regulate grid voltage,” IEEE he was a faculty member in the Electrical
Transactions Energy Conversion, vol. 24, no. 4, pp. 983–985, 2009. Engineering Department at IIT Kanpur, India, from 1989-2001. He has co-
[31] Rajiv K. Varma, Vinod Khadkikar and Shah Arifur Rahman, “Utilization authored an IEEE Press/Wiley book on Thyristor Based FACTS Controllers.
of Distributed Generator Inverters as STATCOM” PCT Patent He has co-delivered several Tutorials (IEEE sponsored), Courses and
application PCT/CA2010/001419 filed on 15 September, 2010. Workshops on Smart Inverters, FACTS, SVC and HVDC in different
[32] Rajiv K. Varma, Shah Arifur Rahman, Mahendra A.C., Ravi Seethapathy countries. His research interests include FACTS, power systems stability, and
and Tim Vanderheide, “'Novel Nighttime Application of PV Solar Farms grid integration of photovoltaic solar and wind power systems. He is active on
as STATCOM (PV-STATCOM)'”, Proc. 2012 IEEE PES General several IEEE Working Groups. He is the Secretary of the IEEE “HVDC and
Meeting at San Diego, USA, July 2012 FACTS Subcommittee” since 2015 and Chair of IEEE Working Group
[33] Rajiv K. Varma, Shah Arifur Rahman, and Tim Vanderheide, "Novel 15.05.17 on “HVDC and FACTS Bibliography,” since 2004.
Control of PV Solar Farm as STATCOM (PV-STATCOM) for
Enhancing Grid Power Transmission Limits During Night and Day",
IEEE Trans. on Power Delivery, Vol. 30, No. 2, pp 755-763, April 2015 R. Salehi (S’15) received the B.Sc. degree in
[34] Rajiv K. Varma, "Multivariable Modulator Controller for Power electrical engineering from Iran University of
Generation Facility", PCT Application (PCT/CA2014/051174) filed on Science and Technology (IUST), Tehran, Iran, in
December 6, 2014 2008; the M.Sc. degree in electrical engineering from
[35] Shah Arifur Rahman, Rajiv K. Varma, and Tim Vanderheide, Amirkabir University of Technology (AUT), Tehran,
“Generalized Model of a Photovoltaic Panel”, IET Renewable Power Iran, in 2011. He is currently pursuing the Ph.D.
Generation, Vol. 8, No. 3, pp. 217-229, 2014 degree in electrical engineering at University of
[36] M. H. Rashid, Power Electronics Handbook: London, U.K.: Academic, Western Ontario (UWO), London, ON, Canada.
2001. From 2009 to 2014, he worked in the field of power
[37] A. Yazdani and R. Iravani, Voltage-sourced converters in power electrical engineering in industry as a Senior
systems: modeling, control, and applications: John Wiley & Sons, 2010. Engineer. His research interests include FACTS, power system stability and
[38] P. A. Dahono, Y. Sato, and T. Kataoka, "Analysis and minimization of control, grid integration of inverter-based distributed-generation (DG)
ripple components of input current and voltage of PWM inverters," IEEE sources, renewable energy systems, and harmonic elimination of Multilevel
Trans. Industry Applications, vol. 32, pp. 945-950, 1996. Inverter.

1949-3029 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.