Vehicle-to-Home (V2H), Vehicle-to-Grid (V2G), at Scale, Today And Why The Smart Power Integrated Node

The EVs that people own today are capable of Vehicle to Home (V2H) and Vehicle to Grid (V2G) with a software change allowing for negative current.

The question of whether V2H/V2G can be provided at scale has been something that many have pondered. Flex Power Control (FPC) has developed the Smart Power Integrated Node (SPIN), since its inception, to address energy management, local system integration, grid integration, and coordination issues driven by the introduction of large energy sources/loads at home. SPIN addresses a full range of V2X use cases, along with the decision logic about when and how to deliver it, while providing consumers unprecedented value by maximizing the value-stacking opportunities, both locally, at the distribution grid level, as well as in the market context, either working as a unitary device, connected to a grid or a microgrid, as a fleet of devices or integrated with a third-party aggregator.

Several factors need to align for V2H/V2G to be at scale.

1. EVs must be made available with reverse power flow capability.

Many of the factors below are accelerating the EV capabilities to be bidirectional:

A: Export Power Functionality is built into today’s charging protocols: Most OEMs have implemented their production DC charging algorithms in such a way that they also allow reverse power flow for CCS1-based systems. We tested SPIN with two production EVs from two different OEMs. Both were able to export power by using their production DIN70121-compliant charging system. This, however, is a necessary but not a sufficient condition for scaling. SPIN was developed as a CCS-native device, so it has CCS (and, by extension, NACS) compliance built in from the beginning.

B: Incremental impact on battery life due to V2X operation is very low, allowing a significant amount of export power throughput over the life of the battery without appreciable degradation. The extent of degradation depends on several factors such as the battery chemistry, battery system design, battery control algorithms, and the OEM policies around warranty. This is why the OEM (and the EV owner) must (A) design the EVs for accommodating reverse power flow functionality, and (B) EV owner must authorize the use of the vehicle for operating in an export power mode, in addition to procuring and installing appropriate SPIN hardware and wiring that complies with applicable codes and standards.

C: Marginal cost to EVs to enable reverse power flow is low for DC V2X capability: Incremental cost to make an EV reverse power flow compliant, in the case of a DC off-board charger, is relatively small to provide for the software necessary. This on-vehicle software performs these functions: (a)manage the on-board battery energy for off-board use, both for V2H and V2G capabilities (b) manage the interaction with the customer and the local control system that create the V2H ecosystem behind the meter (V2H requires a Vehicle,  an electrical interface on the premises, a controller (most likely on-vehicle)) that allows the orderly transition between grid-tied and islanded modes, and its interaction with the transfer switch and (c) ensure that the core mobility application of the EV is not constrained by imposing the EV and EV owner limits on how much energy is allowed to be consumed by the off-board loads. SPIN has developed these requirements at the system level that can be transferred to any OEM. SPIN itself brings cloud and mobile interfaces to the customers so that the same functionality, at a minimum, can be achieved with the DC Charger as is with the vehicle.

The battery charge or discharge power limits of a vehicle are determined cooperatively by what the connected system (home, grid, etc.) needs versus what the vehicle battery can accept or provide. The vehicle battery management system sets the limits based on the battery’s state of charge, state of health, temperature, cell balance, and customer preferences.  V2H/V2G is operationally as simple as changing the direction of the battery current. The decision-making – when where, how much, for how long, and at what level – needs to factor in the number of Use Cases that a vehicle could support to maximize value-stacking. This depends on the variety of utility territories that have appropriate programs for participation with incentives and that define the participation conditions (availability, discharge rates, latency (response time), energy availability, and the days/times that the participation would be needed, as well as the signaling requirements).  SPIN control and communications software in the cloud and the embedded electronics has the controls and communications capabilities to communicate with the utility signaling systems, the vehicle on-board charger controller (and the BMS), as well as operate based on any constraints placed by the OEM, the utility, or the vehicle owner.  And SPIN manages the energy flow across all the DERs it’s connected to: the PV, optional local storage, and the EV.  SPIN works with the constraints of its resources and executes the objectives that a consumer and or the utility has set. The OEM can enable V2X capability today by continually limiting the power export, communicating over the same physical and control interfaces.

2. Open, Interoperable Standards-Based Design

The standards-based design lends to interoperability, multiple vendor availability, conformance-based qualification, uniform installation, and operational requirements. It also removes the burden on the customers of a forced lock-in with a particular manufacturer’s vertically integrated system. Therefore, V2H/V2G needs to be implemented using open standards, and systems need to have interoperability, CCS and or NACS connection, and finally, the protocols DIN70121 and/or ISO 15118-2 (followed by ISO15118-20 when appropriate) need to be implemented.  Flex Power Control designed the SPIN as a smart inverter, with its electrical, controls, and interface architecture with interoperability in mind and validated its operation with three different EVs from three different OEMs. The pioneering work of Flex Power Control (collaborating with EPRI) demonstrated how DIN70121 can be deployed as a bidirectional power flow protocol. This approach is now considered for the SAE standards as a pragmatic bridging solution until IEC/ISO15118-20 becomes fully available.

All the UL-certified systems in the market today are proprietary V2H systems. They limit consumers to a specific vehicle or vehicle manufacturer.  In contrast, open systems like SPIN can charge/discharge any EV. The vehicle only needs to permit to charge/discharge, with certain constraints. Interoperability will allow the consumer to lease or purchase the EV of their choice. SPIN compatibility with CCS1 (and emerging NACS, to be verified as soon as available) is a huge plus, essentially enabling the entire Plug-in Electric Vehicle (PEV) installed base operating with CCS1 or NACS plugs (including Tesla, beginning 2025) as a potential usable asset for V2H/V2G.

3. The Off-board Bidirectional Charger must be capable of grid-parallel and grid-forming functions, available cost-effectively, and comply with safety and regulatory requirements.

Safety and Regulatory Codes and Requirements The good news is that the safety and regulatory requirements are known to the providers of off-board chargers. Therefore, any products that meet these technical targets qualify. However, the know-how to design-in these requirements into the system is limited. So, the knowledge of topics like galvanic and high-voltage isolation, EMI/EMC, and product design practices that the automotive industry is familiar with are not widely known outside the automotive industry, and the automotive industry (OEMs and the supply chain) keeps these closely guarded as competitive information. This creates another barrier between the automotive manufacturers and product manufacturers, with little or no understanding of these principles of designing safety-critical systems. As to Flex Power Controls, automotive industry power electronics design practices and robust system engineering practices are in its design DNA.

Grid-parallel versus grid-forming operation is a new topic for most of the industry. Therefore, the design and operational know-how are even more limited. This is because the entire DER industry for intelligent inverters, stationary storage systems, PV inverters, and V2G equipment providers has only focused on grid-parallel operation, with little thought given to grid-forming inverters modes, let alone enabling a dynamic switching capability The reason for this was that the grid resources were only envisioned to support the grid dynamic imbalance between supply and demand by injecting active/reactive power, while the grid was operational. Smart inverters that are grid-tied cannot operate during the power outage. Most of the V2G bidirectional charging equipment that is UL certified is also based on this grid-tied operation, only capable of operating in grid-parallel mode. Therefore, these vendors were caught off guard when the landscape suddenly shifted to make V2H/V2B (Vehicle to Building) and the backup power operation to be the primary market entry use cases.  This meant that the vendors only certified to operate in grid-parallel modes have had to add significant componentry to their systems, and this has added parts and complexity. In the case of SPIN, Flex Power Controls designed it to be a home power system first, i.e., V2H mode was the primary mode of operation, with the capability to switch on the fly to grid-following, if the opportunity presents itself. This was based on the dominant logic that the primary opportunity for a large vehicle battery to provide guaranteed benefit to the vehicle owner is during power outages, while the infrequent use of the vehicle batteries not affecting their life or warranty much, if at all.

4. Resiliency, Automatic Mode Switching between Grid Parallel and Grid-Forming Modes:

Providing backup power without human intervention is needed in order for consumers to embrace V2H/V2G. SPIN automatically senses the power outage and works with the utility-side switch to convert itself into a grid-forming inverter with the help of an integrated, rechargeable, black-start battery, facilitating the control power supply during the transition. SPIN automatically reverts to the grid-parallel mode upon energy restoration from the utility. Furthermore, SPIN allows local solar PV to keep operating in the grid parallel mode against the SPIN grid-forming inverter, to provide power to the home and charge the EV battery at the same time. The logic as to how to manage the energy from the grid and from the solar array is contained within the SPIN master controller and in the cloud. So, it can continue to provide whole-home energy without so much as a glitch.

How does  SPIN work with EVs?

SPIN works with any EVs with CCS1 (or NACS, subject to verification), thereby making vehicle OEM’s job easier and delivering better value for consumers/utilities. The integration of SPIN with EVs revolutionizes how electric vehicles function within the realm of home energy management systems, including smart meters, smart panels, utility switches, and smart appliances, in addition to PV, optional storage, and EVs, and providing grid flexibility capabilities. By seamlessly incorporating EVs into the equation, SPIN redefines their role to align harmoniously with household energy needs. SPIN operates within the defined parameters the vehicle established, efficiently managing its charging and discharging processes. What sets SPIN apart is its comprehensive awareness of the home’s energy demands, production capacities, consumer preferences, and utility requirements. This level of situational awareness empowers SPIN to make decisions encompassing the entire household’s holistic energy ecosystem. Notably, this intelligence eliminates the vehicle’s need to navigate the complexities of various grid use cases. Instead, the vehicle needs only to possess fundamental awareness of its battery status and the allowances for charging and discharging. In this synergy between SPIN and EVs, energy management reaches new heights of efficiency and practicality.

SPIN, as a unitary device or as a fleet, can also integrate with the utility DERMS (it’s already been tested and operational with IEEE2030.5) to provide situational awareness, wide area visibility, and operational data for planning and operational purposes, including flexible interconnection.

How does SPIN work with consumers?

SPIN utilizes consumers’ input parameters and utility priorities (in the form of open standards-based signaling such as DERMS requests or Flexibility Management Systems through dynamic pricing) to establish a Recommended Operating Profile (ROP), which is the time-dependent dispatch of individual connected resources (PV, optional storage, and EV). This ROP serves as a guideline for SPIN to conduct its operations, considering the conditions of Distributed Energy Resources (DERs) like EVs, Stationary Batteries, and PV systems, alongside real-time forecasts of energy consumption and production at the residence. The ROP is updated every five minutes but can be updated as frequently as necessary. The ROP consists of a hierarchy of prioritized operational modes. Should conditions change between ROP calculations, SPIN seamlessly transitions to executing the next prioritized strategy. For instance, if a DER becomes unavailable after the ROP is generated, SPIN swiftly switches to the subsequent best-fit ROP in a seamless progression.

How does the SPIN work with existing utility tariffs/energy pricing?

SPIN considers energy cost and pricing (i.e., tariffs, kWh cost, sales price, etc.) along with the household’s energy needs in determining the ROP. This information is provided through various means dependent on the utility territory in which the household is located.

How can SPIN enable market acceleration at scale today for V2H/V2G?

There are four reasons SPIN will accelerate V2H/V2G:

1. SPIN (EVO and MAX) enables the existing fleet of PEVs to be V2H/V2G

2. SPIN is an integrative device that creates a behind-the-meter residential (or small commercial) microgrid using only PV and EV batteries. It is open standards-based and has been tested to be interoperable in grid-tied and islanded modes.

3. SPIN is available in both a greenfield application (3-in-1 device that integrates local PV, EV, and optional Storage) or a brownfield/retrofit application (EV-V2X-capable grid-connected inverter that auto-islands), still enabling the local rooftop PV to send power to the home. This allows its easy integration into any existing or newly built homes as a part of the home electrical system configuration. Just plug in any CCS/NACS capable EV, and SPIN will automatically supply power locally during outages. SPIN can operate with smart panels to optimize energy delivery in the home or small commercial settings (for power levels from 10kW to 30kW), as a single unit or operating as a fleet across the campus.

4. SPIN provides three elements of value: better backup power, operational cost savings, and incentive revenue at a lower system cost. SPIN’s one-box systems are projected to have an initial cost of < $8K. This is compared to an existing whole home backup power system’s worth of a minimum of $15K, along with fuel and maintenance costs.  Alternatively, today’s backup systems based on EVs, stationary batteries, and solar need multiple boxes to achieve partial home backup power, costing approximately $20K installed.

For SPIN, in addition to unit and installation savings, the device can synergize the operation of the DERs it manages to provide maximal value stacking to the owner. For example, a study by the University of Kentucky showed an annual cost savings of $2,477, avoiding demand charges. Revenue for grid services has been estimated at $1,200 per year.  The hardware life is 20 years compared to current inverter systems of 7 to 9 years. Finally, an analysis has also been done by EPRI. The report Value Assessment of DC Vehicle-to-Grid Capable Electric Vehicles: Analytical Framework and Results (epri.com) provides an assessment of value that shows even more significant benefits than above. This demonstrates that the initial outlay of dollars is lower, household energy costs are reduced, revenue can be generated, and operating costs are lower. This provides real incentives to deploy SPIN in residences across the globe.

What has the Flex Power Control team accomplished so far, and what are the additional enhancements planned?

This generation of SPIN establishes a new product, the home energy center, which is a platform for new services. SPIN controls power flow, securing and managing energy for the home. SPIN is unlike energy management systems of today that ration the power provided. Because SPIN controls power flow it is, in a sense, a creator of power. This seamless power flow control makes it unique and provides for endless possibilities. These possibilities extend beyond the home, to the power distribution network and the actual supply of power (i.e. Virtual Power Plants) itself. SPIN has demonstrated this functionality to #DOE, #EPRI, #CEC and three vehicle OEMs. The production design is complete and UL certification is the next step.

SPIN will become an integral part of the grid, allowing for improved asset management. Enhancements will be made to increase the value proposition for the consumer and utilities by taking advantage of the awareness created by SPIN.

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