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The Role of Smart Inverters in Distributed Energy Resource Management

(Joseph Gottlieb, CTO, Tuesday September 15, 2020)

For distributed energy resources (DERs) such as photovoltaic (PV) solar, or energy storage resources, smart inverters are a critical ingredient in the overall energy equation. Smart inverters provide two functions that are critical for DERs. The first function is rather obvious. Smart inverters, like all inverters, convert DC power to AC power. In the case of inverters for commercial applications, this typically involves converting high-voltage DC power (usually between 300 to 800 VDC) to intermediate-voltage AC power – 220 VAC or 480 VAC three-phase power. In addition to converting DC power to AC power, the inverter must provide phase matching and/or phase compensation to support reactive loads. If an inverter has multiple ports (one for AC, one for DC battery storage, and one for DC PV solar), it must be able to take power from the PV solar input and put it into the battery DC port or the AC port, and be able to go from the AC port to the DC battery port or vice-versa.

The power inversion function is in some ways the easiest, as communicating with the grid is arguably the harder function that a smart inverter must provide. A smart inverter must support communication interfaces and protocols such as MODBUS, CAN-bus, RS-232, RS-485, and Ethernet, and do so securely. Most importantly for the US market, a smart inverter must also be compliant with UL 1741 and UL 1741-SA, also known as the UL standard for “Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources”. This standard defines how smart inverters interact with the utility grid – when to put power onto and take power off of the grid. Most smart inverters also run applications that allow them to minimize overall energy costs such as peak shaving.

Rhombus has built high-power bi-directional inverters for renewable energy such as “behind the meter” grid energy storage systems for several years. We have applied that expertise to the design of our bi-directional electric vehicle (EV) charging systems, which are designed from the start for the needs of fleet operators. As a leader in the development and manufacturing of bi-directional, high-power systems for both vehicle charging and grid energy storage applications, Rhombus is unusually experienced in high-power charging systems for EVs, and  the area of V2G charging. Rhombus  also excels in the design and testing of high-power electrical equipment to meet the requirements of UL and other certification organizations. We have built hundreds of V2G-capable high-power, high-reliability chargers for a variety of different sizes and classes of EVs. Find out how we can help you by contacting us at, by reading our Vehicle to Grid Solution Brief, or by viewing our video or webinar on Vehicle-To-Grid technology.

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