Microgrid Performance Categories

Microgrid Performance Categories

First thing to consider when there are DERs 

• Applicable to Rule 21 and Microgrid.

• Decide DER performance criteria. Category A or B? Category I or II or III? 

Why? Accordingly to IEEE 1547

• Set up DER voltage/frequency ride through accurately 

• Follow PQ control requirements

Normal performance categories:

Category A:

• This represents the baseline or minimum level of performance capabilities necessary for voltage regulation in Area Electric Power Systems (Area EPS).

• It is adequate where the DER penetration (i.e., the proportion of energy produced by DERs) in the distribution system is lower and where the DER power output does not experience frequent or significant variations.

Category B:

• This category covers all the requirements specified in Category A and includes additional capabilities.

• Category B is more suitable for situations where the DER penetration is higher or where the DER power output is subject to frequent large variations.

Abnormal performance categories:

Category I:

• This category represents the minimal level of performance based on bulk power system (BPS) reliability needs.

• The requirements of this category align with the standard of the German Association of Energy and Water Industries (BDEW) for medium voltage synchronous generators, which is widely adopted in Europe.

• It should be noted that a high penetration of DERs with only Category I capabilities could impact BPS reliability negatively, although limited penetration would not have a substantial negative impact.

• Category I DERs are generally seen as a baseline level of capability and reliability.

Category II:

• Category II builds on Category I's requirements and is designed to meet all BPS reliability needs.

• The standards for Category II are coordinated with the existing BPS reliability standard, NERC PRC-024-2, which helps avoid the undesirable triggering of bulk system generators during system disturbances.

• This category specifies additional voltage ride-through capability for DERs, going beyond mandatory voltage ride-through defined by NERC PRC-024-2. This extra provision is to account for possible delayed voltage recovery on the distribution system due to specific load characteristics.

Category III:

• This is the highest level of abnormal performance, intended to handle the most serious disturbances. Category III DERs offer the greatest disturbance ride-through capabilities.

• The category addresses integration issues such as power quality and system overloads, particularly in local Area Electric Power Systems (Area EPS) that have very high levels of DER penetration.

• The standards for Category III are based on the California Rule 21 Smart Inverter requirements. The rules in this category also provide increased bulk power system security by reducing the potential for loss of DERs during major system events.