Category Modeling and Control of Sustainable Power Systems

Steady State Assessment

It goes without saying that all aspects outlined in Section 3 with respect to detailed and accurate steady state modeling of WGRs is a key requirement to performing such assessments. Following the development of a detailed WGR steady state model taking into account all aspects outlined in Section 3, the following aspects need to be accounted for in the steady state reactive capability and/or power factor assessment of WGRs:

• Assessment of reactive capability of the WGR campus at varying ac­tive power output levels

• Accurate modeling of turbine reactive capability and variation in reac­tive power capability owing to:

o Terminal Voltage

o Active Power Output

o A combination of the two factors above

• Adequate and accurate modeling of detailed collection system to ac­count for the VAR...

Read More

Parallelization of Iterative Methods

In this section, we discuss the parallelization of iterative methods using multi-core and many-core computation architectures. CGNR + Jacobi pre-conditioning and CG + Jacobi pre-conditioning are selected for the parallelization evaluation based on the test results in the former section.

2.1.1 The Parallelization Strategy

As previously discussed, both the CG + Jacobi and the CGNR + Jacobi pre­conditioner (Figure 17) have a common framework that includes an initialization part and an iterative part constructed by several common operations (e. g., matrix vector multiplication, vector inner products, and vector updates). Here, the vector update op­eration is defined as Ui=Vi+awb where u, v, w are n x 1 vectors, and a is a scalar.

Table 5 illustrates the time spent by the common operations of...

Read More

Coordinated On-Load Tap-Changer Voltage Control

Traditional control strategies of on-load tap-changers (OLTCs) are either based on the voltage regulation at a single busbar or voltage drop compensation on a partic­ular line [24]. Such voltage control strategies are based on local measurements and are suitable for traditional distribution systems with unidirectional power flow. However, these strategies may cause problems in distribution networks with bi­directional power flows. On the other hand, the area-based control strategy of OLTCs is based on measurements from various locations of the network. In this way, the voltage regulation of OLTCs can be based on the voltage information of the bus that has the most severe over voltage problem [24]...

Read More

Level-Shifted SPWM

Level-shifted SPWM (LS-SPWM) is a natural extension of unipolar SPWM tech­nique for multilevel converters [35]. Similar to the phase-shifted modulation, an m-level CM converter using level-shifted multicarrier modulation algorithm re­quires (m-1) triangular carriers, all having the same frequency and amplitude. The (m-1) triangular carriers are arranged in vertical shifts, instead of the phase-shift used in PS-PWM, so that the bands they occupy are contiguous and each carrier is set between two voltage levels. Since each carrier is set to two levels, the same principle of unipolar SPWM can be applied.

To generate the corresponding levels, the control signal should be directed to the appropriate switches. The carriers span the whole amplitude range that can be generated by the converter...

Read More

Battery Constraints

The BESS or generally any storage system can be defined with three important pa­rameters named the nominal energy capacity, the nominal power capacity, and the round-trip efficiency of the battery. These parameters are respectively shown by Es, Ps, and J] in this section. The round-trip efficiency of the BESS is the product of charging and discharging efficiencies as follow:

where, r/c and r/d are respectively the charging and the discharging efficiencies. The introduced parameters of the BESS and their values set different constraints on the battery operation.

Regarding the energy capacity, this value limits the energy that can be stored in the battery...

Read More


With the wind generation technology maturing over the last decade or so, the pe­netration of wind generation resources (WGR) in transmission system networks across the world has been on the rise consistently. With close to 76,000 MW of in­stalled capacity as of 2006, wind generation can now be effectively termed as “utility scale”. With the large amounts of wind penetration comes the ability of wind to impact generation and transmission planning for regional reliability and/or utility organizations across the world. Figure 1 depicts the United States’ national fuel mix as of 2009 as per Edison Electric Institute (EEI) [1]. Figure 2 depicts the growth of installed wind capacity in the U. S over the last decade or so [2]...

Read More

Robust Control Methods

MGs may have different levels of uncertainties. Linear Controllers are model- dependent methods; hence, these methods cannot have proper performance in MGs with high uncertainty. Nonlinear control methods have been developed in order to improve the performance of VSIs in such applications. However, linear control methods can be used in MGs whose characteristics fit these methods. These methods are as follows: 1) H “, 2) Repetitive, 3) Robust servo-mechanism problem and 4) Two nonlinear robust controls: sliding mode and hysteresis control.

Read More

Incorporation of Short-Term Load Forecasting

As discussed earlier, the process of evaluating whether an alternate source is capa­ble of supplying the unserved load requires knowledge about the current or power of the load. A straightforward approach to obtaining this information is to use the rated value of the load in the evaluation process, as done in the example in Figure 1. The advantage of this procedure is that it can be programmed offline as the load rating is known from the network configuration data. In many instances, however, this procedure may not be sufficient because the actual load typically varies with time, and it may deviate considerably from its rated value. The load rating itself may also vary from season to season and even from hour to hour...

Read More