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Date: Mon Jan 04 2021 13:23:28 GMT-0800 (Pacific Standard Time)

This is the decision in the Rule 21 process which opens the door to distributed energy resources becoming a major part of the smart grid in California. It mandates 'smart inverters' that contain communication capability, so that DER's can be coordinated by utility companies. It mandates local energy storage so each DER can send/receive electricity as needed.

This Decision is a big document, and is one of those ground-breaking government decisions that should open the door to whole new businesses and options for all. The bottom line is to facilitate the transformation of California's energy grid to multi-way coordination of electricity resources. Where the electricity grid is currently controlled by a small group of large entities (electrical utility companies), this decision opens the grid to any entrepeneur with a business plan and equipment compatible with certain standards.

CPUC Commissioner Sandoval likened the recent Rule 21 decision in California to the Carterfone Decision that opened telephone infrastructure to necessary competition. In the USA the telephone system was controlled largely by AT&T, with General Telephone (a.k.a. Verizon) offering telephone service in some cities. By law no 3rd party equipment could be connected to telephone lines, resulting in stagnant telephone technology development. The Carterfone decision allowed 3rd parties to sell telephone equipment, so long as it adhered to agreed-upon standards meant to guarantee telephone system safety. Over time more and more services developed around the telephone system, the primary examples being The Internet and the Cell Phone system.

The Rule 21 decision mandates that "Distributed Energy Resources" must include inverters with smart communication capabilities. The communication runs over the Internet using SEP2 (a.k.a. IEEE 2030.5), a highly secure protocol running over encrypted HTTPS connections. The root of all this communication starts at the utility companies and ends up at the on-site inverters at each DER location. The purpose is to coordinate the actions of these smart inverters to support grid stability, and to absorb electrical power from the grid when needed, or to emit electrical power into the grid as needed.

In other words - any DER implementing the communication protocol (IEEE 2030.5) can connect to the electricity grid and participate in the energy services market, earning revenue for offering those services.

It mandates the creation of a new type of business entity -- DER Aggregators. Each DER Aggregator will manage a fleet of DER assets, taking commands from the utility companies and distributing those commands to the DER's under its control.

A typical DER is some rooftop solar panels on a home or factory, connected to the grid through an inverter. To satisfy the new requirements, the DER will also include a local energy storage system. (a.k.a. a big battery pack) This is so the DER can absorb or release energy as needed any time of the day.

IEEE 2030.5 defines these commands:

  • Immediate controls - a.k.a. “A fixed output setting”:
    • opModFixedW – Fixed real output power (soft floor)
    • opModFixedPF – Fixed power factor.
    • opModFixedVAr – Fixed reactive power.
  • Curves (DERCurve) - dynamically vary an output based on an input signal:
    • opModVoltVAr – Voltage-VAr curve
    • opModVoltWatt – Volt-Watt curve
    • opModFreqWatt – Frequency-Watt curve
    • opModWattPF – Watt-Power Factor curve
    • opModLVRT – Low Voltage Ride-Through curve
    • opModHVRT – High Voltage Ride-Through curve

The smart inverters are supposed to automatically engage in certain actions that support grid reliability. The commands shown here are used to configure the parameters under which each inverter takes those actions.

Until now, inverters were required to disconnect from the grid if conditions went out of whack. Under the new paradigm, the inverter is supposed to remain connected and to take actions that stabilize the grid.

DER's connect to the grid through a Point of Common Coupling. Generally speaking a DER is wired to the electrical system through its "Electrical Connection Point" (ECP). For a larger installation, such as a "Campus", the Campus is connected to the overall electrical grid at its Point of Common Coupling (PCC).

The Utility company commands to the inverters refer to its behavior at the PCC, and its ability to influence grid conditions near the PCC. The Utility companies will be (are) constantly monitoring grid conditions around the grid. With DER's under remote coordination/control, the Utilities will now have a mechanism to trigger support if conditions at a particular grid segment go bad.

The contents of The Ruling

This ruling is the result of several years of study by the Utility companies and certain stakeholders in the Solar and Energy Storage industry. The impact goes beyond California, because it necessitated changes in inverter standards (UL1741 and IEEE1815).

Attached to the Decision is a pair of documents spelling out (at a high level) the communication system requirements. The main body of the Decision is a timeline starting in June 2016, when the Decision was published, until late in 2017 when the mandated results go into effect.

The object model to be used in the communications is defined in an IEC technical report: TR 61850-90-7. IEC 61850 in general defines the object model and commands used in electrical utility system equipment. As an IEC standard, it has global impact. TR 61850-90-7 defines new object modeling and commands specifically for distributed coordination of smart inverters.

For California's implementation, it is required that IEEE 2030.5 be the transport protocol for the objects defined in IEC 61850.

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