Peter McLaren

Dynamic interactions between distribution network voltage regulators for large and distributed PV plants

This paper summarizes the initial investigation of dynamic interactions of voltage regulating equipment when allowed to act together with one or more large voltage-controlled solar photovoltaic (PV) generation plants. The study results are based on an existing large PV plant and distribution circuit in the service area of a major electric utility. The existing feeder does not have any voltage regulating equipment and the PV plant is not allowed to control voltage, hence injects real power only. However, in light of the growing interest in allowing PV plants to control voltage, several scenarios are considered by allowing PV plants to control the voltage at the Point of Common Coupling (PCC) along with the traditional voltage regulators. Further case studies are performed by distributing the large PV plant into six PV plants of equal power rating connected at different feeder locations. This configuration has been investigated to determine possible differences in interactions of voltage regulators between a large plant and distributed plants. The voltage regulating equipment considered are On-Load Tap-Changing Transformers (OLTC), Switched Capacitor Banks (SCB) and also PV plant inverters capable of controlling the voltage at the PCC. The 12.6 MW (peak a.c.) PV plant and its controls, the regulating equipment, and the distribution network are modeled using a Real Time Digital Simulator (RTDS). Initial study suggests that allowing PV plants to actively participate in the voltage control process requires a coordinated control to minimize the number of operations of traditional voltage regulators.

Implementation of a Ship-Wide Area Differential Protection Scheme

The philosophy, design, implementation, and evaluation of a ship-wide area differential protection scheme are described in this paper.

Impact of PV on distribution protection system

This paper investigates the impacts of PV interconnection on the protection systems of a distribution network, especially when power flow is reversed in high penetration scenarios. A Florida based substation and its six-feeders were selected for the study. The system was slightly modified to make it a notional system that still closely represents the actual system behavior from the point of view of system protection. The main modification is in the representations of loads, where all the loads were represented by fewer aggregated loads on each feeder. One of the feeders is 9 miles long and has a 12.6 MW (AC) PV plant connected to the primary side of the feeder at a distance of 4.8 miles from the substation. The feeder has an average load of approximately 11 MVA that makes it a contender for a high penetration (more than 100%) feeder when PV reaches its peak generation. The model of the entire substation, its feeders and protection system has been built using a high fidelity transient simulation tool RSCAD. Initial simulation results indicate that if protection devices are coordinated properly, a reverse power flow does not create any nuisance trip or malfunction of the protection system. However, based on the location of the PV plant with respect to the fault, slight change in the trip time of the time-overcurrent relays was observed.

Impact of Waveform Distorting Fault Current Limiters on Previously Installed Overcurrent Relays

This paper investigates in detail the impacts of distorted current waveforms, produced by certain types of fault current limiters on time-overcurrent protection relays. A thyristor-based solid-state fault current limiter is chosen as representative of such a device for a case study which investigates its effects on two coordinated protection relays. A detailed software model of the current limiter has been developed and implemented on the real-time digital simulator platform, modeling a typical distribution system. Relay models are used to obtain initial results, which are later validated by an actual protective relay connected in a hardware-in-the-loop simulation setup. The results illustrate the increase of relay tripping times due to severe current limitation caused by the fixed firing angle control of the current limiter. It is revealed that different current measurement principles employed by the relays, such as fundamental, peak, or true rms, can lead to miscoordination due to the distorted fault current waveform. It is demonstrated that these undesirable effects can be mitigated by employing appropriate control strategies for the firing angle in the current limiter.

New simulation tools for power systems

A brief history of analog simulators is given leading up to the development of the new types of digital simulator. Examples of the older analog simulators is followed by examples of their digital counterparts. Typical output waveforms from the new simulators are shown both in playback and interactive mode. Specific examples are given of the increase in testing efficiency using the new real time digital simulators with a batch testing feature.

Power hardware-in-the-loop: A value proposition for early stage prototype testing

This paper describes advanced power hardware-in-the-loop (PHIL) facilities and experience gained in testing laboratory prototypes. The benefits of subjecting equipment to simulated environments include increased flexibility in designing, implementing, and executing experiments that reflect situations as close as possible to real world conditions. Individual test scenarios can be quickly configured and adapted once the device under test is connected, as only changes in software models need to be accommodated. Consequently, the required time and financial expenses associated with experimentation and testing are reduced. Further, the risk of late and costly changes due to specifications and design choices can be avoided as thorough and realistic tests can be performed earlier in the development cycle and before actual installation and deployment in the field. And, PHIL testing reveals how equipment will interact with the system for which it is being targeted in a way that more conventional non-interactive testing approaches cannot. As an example, the described PHIL capabilities can be used to derisk technology envisioned for realizing smart(er) grids.

Hardware Implementation of a Ship-Wide Area Differential Protection Scheme

The philosophy, design, implementation and evaluation of a ship wide area differential protection scheme is described in this paper.

Testing the “smarts” in the smart T & D grid

The growing sophistication and complexity of power system control apparatus and systems plus the addition of new topological features such as distributed generation at the distribution level requires new test environments which can evaluate and optimise these systems prior to deployment in the real system. One such environment is described in this paper along with examples of its use in evaluating application scenarios involving both real and simulated parts of a controlled power system. Future developments in the capability of such environments is briefly described.

Modeling and validation of a utility feeder for study of voltage regulation in the presence of high PV penetration

A Florida utility feeder with a high penetration level of solar photovoltaic (PV) generation was modeled in RTDS/RSCAD. The feeder model was validated by comparing the results in different simulation tools, and using field measurements and short circuit data provided by the utility. The feeder has 2.6 MW of PV which is approximately 30% penetration (comparing with peak load). The feeder has a step voltage regulator (SVR) and 4 switched capacitor banks (SCBs) installed to regulate voltage. Studies were conducted to analyze feeder voltage characteristic for the existing circuit configuration and operating scenarios. Additional studies were conducted to determine the potential impact of additional PV penetration that might happen in the future. Validation results show full agreement with the software based validation and a reasonably acceptable match with the field data collected from different locations on the feeder.

Summary changes in 2013 IEEE/IEC Dual Logo COMTRADE standard

The globally used COMTRADE standard was initially developed by IEEE and later adopted by IEC. The first IEEE version was published in 1991 and was later revised in 1999. The IEC version was adopted in 2001. The 2013 revision of the COMTRADE standard is an IEEE/IEC Dual Logo standard planned for publication during the first quarter of 2013. The main motivations for the current revisions are: 1) to remove restrictions that were only relevant for computing technologies of the 1990s and 2) to satisfy the requirement of universal time information in COMTRADE files. The second need was identified during the 2003 Northeast Blackout analysis to time synchronize data from different substations. The working group has also addressed other issues, including the availability of a single file. Industry users feel very strongly about this need to easily exchange and manage COMTRADE files, and the working groups recommendations address these concerns.