Ryan Meng

Apparent Power-Based Anti-Islanding Protection for Distributed Cogeneration Systems

In this paper, the performance of a passive anti-islanding method is experimentally tested for three phase (3φ) cogeneration systems. The tested method is based on determining the wavelet packet transform (WPT) high-frequency subbands present in the d-q-axis components of instantaneous 3q apparent powers (sd and sq), when evaluated at the point of common coupling (PCC). This passive anti-islanding method is founded based on the nature of instantaneous 3φ apparent powers that have components continuously exchanged between both sides of the PCC. An islanding condition can be considered as a transient disturbance that creates nonperiodic and nonstationary high frequency components in sd and sq. These frequency components can be parameterized by WPT high-frequency subbands, which can provide accurate detection of the islanding condition. The d-q WPT-based anti-islanding method is tested for a 3φ cogeneration system under various loading and power delivery conditions. Performance results reveal accurate, fast, and reliable detection and response to the islanding condition.

The Performance of a Digital Interconnection Protection for Grid-Connected WECSs

This paper develops and experimentally tests the performance of a digital interconnection protection for grid-connected wind energy conversion systems (WECSs). The developed protection is constructed by two frequency frames to process voltages and currents measured at the point-of-common-coupling (PCC). The first frequency frame is set to process the d - q-axis components of the instantaneous 3φ apparent powers (sd and sq) determined at PCC. This processing of sd and sq aims to extract their high-frequency subband contents in order to detect the islanding condition. The second frequency frame is set to extract the high-frequency contents (magnitudes and phases) present in the 3φ currents flowing through PCC. These high-frequency contents provide signature information for detecting faults occurring on either side of PCC. The multiframe digital interconnection protection is implemented for performance evaluation on two different WECSs operated in grid connection. Performance results show accurate and reliable detection and identification of the islanding condition and faults occurring on either side of PCC. In addition, performance results show that the multiframe digital interconnection protection has minor sensitivity to the type, structure, ratings, and levels of power delivery to the host grid.

Digital modular protection for grid-connected PMG-based WECSs with battery storage systems

This paper develops and tests a modular digital protection for interconnected permanent magnet generator (PMG)-based wind energy conversion systems (WECSs) with battery storage. The developed protection is constructed from digital relays (modules), each of which provides protection for a specific location of the PMG-based WECS and battery storage. Moreover, each module is featured with phaselet-based fault detection. The outputs of the developed protection are trip signals to operate circuit breakers in the PMG-based WECS, battery storage, and point-of-common-coupling. The modular digital protection is implemented for experimental testing on a 5 kW PMG-based WECS that has a 2.3 kW battery storage. Test results show that the developed protection can offer fast, accurate, and reliable responses to faults occurring in different parts of the tested WECS and battery storage. In addition, test results show that the modular digital protection has minor sensitivity to the location of faults, charge/discharge cycles of the battery storage, and/or levels of power delivery to the host grid.

On the Experimental Performance of a Coordinated Antiislanding Protection for Systems With Multiple DGUs

This paper presents the implementation and performance evaluation of a coordinated antiislanding protection for systems with multiple distributed generation units (DGUs). The proposed coordinated antiislanding protection is structured to process the d - q-axis components of the instantaneous three phase apparent powers (sd and sq) determined at the point-of-common coupling for each DGU. The processing of sd and sq, for each DGU, is carried out by the wavelet packet transform (WPT) in order to extract their low-and high-frequency subband contents. The contents of WPT low-and high-frequency subbands offer signature information that can facilitate detecting the islanding condition and identifying the islanded DGU(s). The coordinated antiislanding protection is implemented in real time for experimental testing on a laboratory collector system that has three different DGUs. Experimental results reveal fast and accurate responses to islanding events, accurate identification of islanded DGUs, and negligible sensitivity to the type or ratings of protected DGUs. In addition, test results show that the d - q WPT-based coordinated antiislanding protection can accurately distinguish between islanding and nonislanding events, including faults, step changes in power delivery to the grid, unintentional loss of grid connection, low-voltage ride through, and sudden harmonic distortion on the grid side.

Developing and testing a digital interconnection protection for grid-connected WECSs

This paper develops and experimentally tests the performance of a digital interconnection protection for grid-connected wind energy conversion systems (WECSs). The developed protection is constructed by two frequency frames to process voltages and currents measured at the point-of-common-coupling (PCC). The first frequency frame is set to process the d - q-axis components of the instantaneous 3Φ apparent powers (sd and sq) determined at PCC. This processing of sd and sq aims to extract their high frequency sub-band contents in order to detect the islanding condition. The second frequency frame is set to extract the high frequency contents (magnitudes and phases) present in the 3Φ currents flowing through PCC. These high frequency contents provide signature information for detecting faults occurring on either side of PCC. The multi-frame digital interconnection protection is implemented for performance evaluation on two different WECSs operated in grid-connection. Performance results show accurate and reliable detection and identification of the islanding condition and faults occurring on either side of PCC. In addition, performance results show that the multi-frame digital interconnection protection has minor sensitivity to the type, structure, ratings, and levels of power delivery to the host grid.

Impacts of grounding configurations on responses of ground protective relays for DFIG-based WECSs

One of the requirements for safe, stable, sustainable, and profitable operation of doubly-fed induction generators (DFIGs)-based wind energy conversion systems (WECSs) is the accurate and reliable protection against electrical faults, in particular ground faults. The performance of protective devices employed to achieve this requirement is highly dependent on the grounding configuration of the DFIG-based WECS. This paper investigates impacts of the grounding configuration on the performance of protective devices used to protect DFIGs-based WECSs from electrical ground faults. Investigated grounding configurations include solid-grounding, low-resistance grounding, high-resistance grounding, and no-grounding. The impacts of the grounding configurations on protective devices are observed through their ability to identify faults, as well as their speed to respond to identified faults. Simulation and experimental results reveal that adequately designed low-resistance grounding offers the minimum impacts on protective devices used for ground protection of DFIG-based WECSs.

Power controller for PMG-based WECSs with battery storage systems

This paper presents the development and performance evaluation of a new controller for permanent magnet generator (PMG)-based wind energy conversion systems (WECSs) that are equipped with battery storage units. The proposed controller is developed to ensure the voltage and frequency stability under changes in the grid demands for active and reactive powers, and under under variations in the wind speed. This objective can be met by adjusting the command active and reactive powers for all controllers operating power electronic converters in the PMG-based WECS and the battery storage units. The developed power based controller has been implemented for performance evaluation on interconnected PMG-based WECSs with battery storage units. The performance evaluation is carried out changes changes in the active and reactive power demands of the host grid, as well as changes in the wind speed. Performance evaluation results show that the power based controller is capable of initiating accurate, reliable, and fast adjustments in the command active and reactive powers to operate all PECs, and maintain the voltage and frequency stability. These performance features are impacted by the changes in grid power demands and/or wind speed.

Evaluating the Performance of Digital Modular Protection for Grid-Connected Permanent-Magnet-Generator-Based Wind Energy Conversion Systems With Battery Storage Systems

This paper develops and tests a new method for managing the responses of multiple digital relays employed in interconnected permanent-magnet generator (PMG)-based wind energy conversion systems (WECSs) with battery storage. The developed method utilizes digital relays (modules), each of which provides protection for a specific location of the PMG-based WECS and battery storage. The outputs of the developed digital protection scheme are trip signals to operate circuit breakers in PMG-based WECS, battery storage, and point-of-common-coupling. The modular digital protection is implemented for experimental testing on a 5-kW PMG-based WECS that has a 2.3-kW battery storage. Test results show that the developed protection can offer fast, accurate, and reliable responses to faults occurring in different parts of the tested WECS and battery storage. In addition, test results show that the modular digital protection has minor sensitivity to the location of faults, charge/discharge cycles of the battery storage, and/or levels of power delivery to the host grid.

A new digital protection for grid-connected battery storage systems

In this paper, a new digital protection is developed and tested for grid-connected battery storage systems (BSSs). The proposed protection is designed using multiple digital relays that are located in different parts of the protected BSS. Each digital relay is featured with a phaselet-based fault detection. The outputs of the developed protection are trip signals to operate circuit breakers in the charging and discharging circuits, battery units, and point-of-common-coupling. The developed modular digital protection is implemented for simulation testing on a 250 kW grid-connected BSS that is charged through a 3φ ac-dc power electronic converter (PEC), and discharged through a 3φ dc-ac PEC. Simulation results show that the developed protection can initiate fast, accurate, and reliable responses to faults occurring in different parts of the protected BSS. These response features have negligible sensitivity to the type and/or location of faults, charge/discharge cycles of the BSS, and/or levels of power exchange with the host power system.

A new interconnection protection for co-generation systems

This paper presents the application of the multi-frame digital interconnection protection for co-generation systems. The multi-frame digital interconnection protection is constructed from two frequency frames, one frame to detect islanding events and the other frame to detect faults on either side of the point-of-common-coupling (PCC). Islanding events are detected based on the wavelet packet transform high frequency sub-band, which is extracted from the d-q-axis components of the instantaneous 3φ apparent powers determined at PCC. The detection of faults, on either side of PCC, is achieved by extracting the magnitudes and phases of the high frequency contents present in PCC currents. The high frequency contents present in PCC currents are extracted by a phaselet filter bank that is composed of 6 digital high pass filters. The multi-frame digital interconnection protection is experimentally tested on a 3.6 kVA co-generation system for islanding events, different faults on both sides of PCC, and non-transient conditions. Test results demonstrate the ability of the proposed interconnection protection to initiate accurate, fast, and reliable responses to various types of transient disturbances.