Beyond aggregation: the engineering challenge behind Virtual Power Plants (VPPs)

In recent years, increasing replacement of synchronous generation with intermittent wind and solar has transformed the underlying dynamics of the power grid.

For modern energy systems, the primary challenge is to cost-effectively accommodate more renewables and maintain stability by making distributed energy resources (DERs) reliably dispatchable. At the same time, an increasing number of electricity consumers, especially large commercial and industrial clients, are seeking ways to optimize energy usage through various strategies, such as implementing distributed generators (e.g., roof-top solar arrays, battery energy storage, etc.) and smart energy management systems.

Virtual Power Plants (VPPs) can play a key role in solving this dilemma. By digitally aggregating and coordinating tens or even hundreds of DERs, a VPP acts as a unified resource capable of flexibly providing capacity to the grid and alleviating supply-demand imbalances, especially during periods of peak demand or when system inertia is low (i.e., when the grid is less stable and needs support to prevent disturbances from cascading).

VPPs also benefit asset owners and prosumers by creating a pathway to turn their behind-the-meter DERs into active and flexible sources of value. This enables commercial and industrial enterprises to reduce energy costs and earn additional revenue from grid services or electricity markets without sacrificing reliability or control.

In the U.S., upwards of 70 VPPs are already operating across 25 states, representing an estimated 30 - 60 GW of capacity. According to the U.S. Department of Energy (DoE), increasing VPP capacity to 80 – 160 GW by 2030 could help address 10 - 20% of peak demand while saving approximately $10 billion per year in grid costs¹.

Numerous VPPs are also operating across the European Union (EU) and China. India has emerged as a particularly important market, as the country is managing rapid DER growth, rising pressure on distribution companies to improve reliability, and the development of major digital infrastructure initiatives like the India Energy Stack (IES).

In many networks across the world, a sufficient DER base exists today to create functional and profitable VPPs. The difficulty lies not so much in aggregation, but in coordinating and optimizing assets to create a virtual plant that operates predictably and reliably under real grid constraints and market conditions. Ultimately, for VPPs to be effective, they must be called upon with the same level of confidence as conventional generation.

Hitachi Energy developed VirtuPlan for exactly this purpose, and with the introduction of VirtuPlan, Hitachi Energy further strengthens its broad portfolio of planning, operating, and trading software solutions.

How a VPP works

A VPP is not a power plant in the traditional sense. It does not depend on a single physical site, fuel source, or centralized generating source. Instead, it operates as a digital and operational layer that connects a collection of DERs, forecasts availability, optimizes use, and regulates output or consumption to achieve profits in the local energy market.

VPPs can comprise any number of behind-the-meter generating and/or energy storage assets, such as batteries, rooftop or commercial solar PV, wind farms or backup generators. They also include energy consumers which can be controlled to flexibly shed load.

The DERs are connected through communication interfaces, edge devices, and energy management software. The VPP platform continuously collects data on asset status, operating limits, energy availability, local conditions, price signals, and grid requirements. It then uses optimization algorithms to determine how each asset should operate, without violating its technological limits.

An example of a VPP is a collection of rooftop solar arrays, batteries, heat pumps, chillers, and EV chargers located at multiple commercial, industrial, and/or residential sites.

During peak demand or if there is a disturbance when system inertia is low, grid operators will send out requests for available resources to respond. The VPP does this by making small adjustments to various DERs and facilities, such as discharging batteries, changing temperature setpoints, shifting cooling cycles, or reducing non-critical loads. While the impact on each customer is minimal, the aggregated response from the VPP across all assets unlocks grid capacity, reducing the need for additional generators to come online and helping to maintain system balance.

VPPs can also participate in delivering ancillary grid services, including congestion management, spinning reserve, or frequency response at different time intervals, from seconds to even days ahead. 

The VPP opportunity and challenge

The benefits of VPPs in many regions today are compelling. They enable behind-the-meter DERs to actively participate in an optimized manner for cost saving, while at the same time supporting the balance between  power generation and demand. This helps defer or reduce investment in conventional generation, transmission, and distribution infrastructure and improve utilization of existing renewable assets, thereby reducing the grid’s carbon footprint.

A recent study found that the net cost of purchasing peaking capacity from a VPP is roughly 40-60% lower than alternative sources, such as a utility-scale battery installation or natural gas peaker plant². At the same time, they provide DER owners with new ways to monetize their assets. However, the same features that make VPPs effective also introduce technical challenges.

Unlike a centralized power plant, a VPP depends on different types of DERs, operating constraints, response times, communication protocols, and availability profiles. Simply aggregating assets into a single platform to control power injection or load shedding is only part of the solution. Much of the value is created through optimization (i.e., determining what each asset should do and when it should do it, while considering technical and market constraints).

Developing a VPP with these capabilities requires expertise in power systems, asset behavior, control logic, cybersecurity, grid codes, and operational risk. This is especially important when the plant is required to provide critical grid services, such as frequency response. The digital tool must have the underlying intelligence to understand what is both economical for the owner/aggregator and technically possible given the asset base.

Overall, for a VPP to be effective, it must meet three distinct gates:

1. Physical assets behavior – The VPP must dispatch assets in a way that respects technical constraints.
2. Market and settlement requirements - It must participate in markets with credible baselines, settlement integrity, and value-stream alignment, also contributing to revenue maximization.
3. Operational compliance - It must earn operational trust through resilience, work efficiency, and clear actionable recommendations to ensure stable operations and address sophisticated operational issues.

Many commercial VPP platforms today are built to address one of these gates in isolation. Far fewer are designed to accomplish all three at once. These dimensions are inherently coupled and must be delivered simultaneously. This is where flexibility translates into reliable system performance in practice.

VirtuPlan: Hitachi Energy’s digital solution for aggregating and optimizing DERs

In response to the growing need for VPP solutions capable of supporting today’s evolving grids, Hitachi Energy developed VirtuPlan.

VirtuPlan is a flexible and cybersecure digital tool designed to coordinate and optimize DERs across geographically dispersed assets. Its flexibility originates from DERs owned by commercial and industrial enterprises. VPP operators and/or energy retailers then aggregate and orchestrate those assets, turning them into reliable capacity that can participate in grid and market operations.

Delivered through Hitachi Energy's deep expertise in power systems and grid integration, VirtuPlan can be adapted in accordance with how each market's grid behaves in practice and customized to meet asset owners’ unique requirements.

Key differentiators of the solution include:

• Predictability - By leveraging intelligent energy management, advanced algorithms, and forecasting, VirtuPlan enables owners to participate in (energy) spot trading and grid ancillary services, such as frequency regulation or congestion management through demand response, peak shifting, and multi-energy carrier optimization. While nearly all VPP solutions today include forecasting capabilities to varying degrees, few adopt optimization strategies driven by mathematical models that fully account for DER operational constraints.
• Scalability - Another key advantage is scalability.  VPP portfolios often evolve over time as customer requirements change and market opportunities expand. As a result, platforms must be able to adapt and manage more complex operating scenarios. VirtuPlan’s modular architecture supports this growth, allowing aggregators to add DER capacity and incorporate new functionalities without disrupting ongoing operations.
• Customization and flexibility - VPPs are required to operate across heterogeneous environments. The DERs within them rarely consist of a single technology, vendor, or communication standard. They comprise legacy systems, new digital assets, customer-owned equipment, grid-facing infrastructure, and site-specific operational constraints.

VirtuPlan’s flexibility comes not only from its software layer, but from Hitachi Energy’s expertise in power systems, protocol assessment, and grid integration, which allows the solution to be tailored to meet the needs of both asset owners and the VPP operator. Depending on the application, VirtuPlan can be used as an automated decision making tool or a planning and advisory tool.

Business models: from strategy to deployment

Importantly, VirtuPlan is more than a digital aggregation platform. It is delivered through a broader lifecycle approach that covers:

• Grid requirements and electricity market analyses
• Customized solution design
• Engineering (deployment, testing, and commissioning)
• Operational support and upgrades

In essence, VirtuPlan serves as the “brain” of the VPP, while automation and/or SCADA systems provide real-time control and execution. The interaction between these layers is essential to translating optimization decisions into operational outcomes.

The value provided by VirtuPlan can take multiple forms, including improved energy cost management, access to new market revenues, provision of grid services, and the ability to scale and operate distributed assets as a coordinated, flexible resource.

Deployment begins with a structured assessment phase: evaluating the DER portfolio, reviewing existing automation and system capabilities, analyzing relevant energy markets, and defining KPIs and objectives. Based on this foundation, the system architecture is configured and adapted using asset modelling, strategy definition, and interface design, followed by integration, testing, and validation of the end-to-end system.

A flexible delivery approach is crucial because VPP operators do not all start from the same point. Creating a scalable and robust VPP requires a business model that is consulting-led and modular. The goal is not simply to aggregate DERs, but to ensure they can operate reliably and economically — both individually and collectively — today and into the future.

VPPs in practice

Hitachi Energy has a proven track record of deploying VPPs in real-world grid environments.

One example is in China, where the company provided a digital solution and advisory services for the smart settlement business of a VPP operated by Zhejiang Energy Group, an energy provider in Southeast China’s Zhejiang Province.

Zhejiang ranks among the top regions in the country in terms of electricity consumption. In the summer months, high temperatures strain local power supplies. The VPP helps alleviate grid stress by providing various auxiliary services, such as peak load regulation, frequency response, and backup generation through intelligent power supply, grid, load, and energy storage interaction.

The platform connects 200+ DERs with a total capacity of 175MW, including energy storage and adjustable loads. Relying on digital coordinated control technology, it provides 24-hour continuous, real-time MW-level response and optimization to dispatch commands, aiding in managing the tension on electricity supply and demand.

The average load regulation rate exceeds 20 MW per minute, with a regulation accuracy of up to 99%. Frequency response performance is superior to that of traditional coal-fired power plants. Additionally, the VPP helps with peak shaving. On a hot summer day in July, the VPP coordinated the flexible energy of 26 enterprise customers, resulting in a 33,000 kWh increase in the electricity supply.

On a separate project, an operator was seeking to utilize the adjustable capacity of geographically dispersed energy resources to provide auxiliary services for the power grid to enhance its regulation capacity.

Hitachi Energy implemented a VPP to connect over 40 DERs from various regions, optimizing resource allocation and enhancing the consumption level of new energy. The project saved an estimated $12 million in investment costs for grid modernization projects. Compared with an equivalent capacity of coal-fired generation, the VPP reduces CO2 emissions by nearly 80,000 tons annually.

Looking ahead: why capacity is not the only success factor

As DER penetration increases and conventional generation plays a smaller role in balancing the grid, operators need new ways to access flexibility, maintain reliability, and manage peak demand. VPPs provide a means to achieve these goals by transforming tens or hundreds of individual BTM assets into a singular, coordinated resource.

Realizing the full potential of VPPs, however, requires more than asset aggregation. It demands accurate forecasting, optimized dispatch, and a deep understanding of how DERs interact with the broader power system.

In the end, what will differentiate successful VPPs is not the amount of distributed capacity they aggregate; it will be their ability to make that capacity interoperable, reliably dispatchable, and seamlessly integrated across diverse grid environments, legacy systems, and digital infrastructures. The ability to harness advanced data analytics through artificial intelligence (AI) is also becoming increasingly important.

That is precisely what VirtuPlan was designed for. By combining digital intelligence, consulting-led customization, and grid integration expertise, the platform helps bridge the gap between distributed asset potential and real operational value, enabling the deployment of reliable, profitable, and future-proof VPPs.