Flexibility of the power system

Distribution system operators are presently confronted with a challenging mission: not only must they cater to the ever-increasing energy needs of consumers, but they must also facilitate the integration of a rising number of dispersed energy sources. This integration forms a pivotal component of the ongoing energy transformation, which is rapidly advancing to augment the role of renewable energy sources within the national energy composition. Consequently, the imperative of assuring the adaptability of the electricity system has assumed unprecedented significance.

What is the flexibility of the power system?

Flexibility represents a fundamental attribute inherent to every power system. It governs the system’s capacity to adapt in response to fluctuations in energy generation and consumption. A system endowed with heightened flexibility is better equipped to efficiently address the requirements of customers and leverage various electricity sources. Thus, this characteristic carries significance not only for upholding energy security but also for adept energy management, thereby minimizing losses.

The concept of power system flexibility can be categorized into primary and secondary forms. Primary flexibility pertains to the inherent characteristics of the power system itself, while secondary flexibility hinges on user behavior. The latter can be influenced by signals communicated to consumers, such as fluctuating energy prices that encourage adjustments in device usage hours.

How do operators maintain the flexibility of the power system?

Maintaining the correct grid frequency is crucial to ensure consumers receive the necessary voltage. In Europe, the standard frequency is 50 Hz with a permissible range of 1.5 Hz. Having not just frequency but also phase alignment of generated current across a large compatibility area allows for the existence of expansive synchronous networks. These networks promote cost-effective electricity distribution and enhance overall energy security.

Energy generation typically exhibits a slightly higher frequency than the specified one, owing to losses sustained during transmission. Conversely, the energy reaching consumers often displays a frequency slightly lower than the standard. Higher power consumption contributes to a decline in this frequency. To rectify this discrepancy, additional power from generation sources might be required to restore equilibrium.

Frequency and power regulation then and now

The existing power systems were predominantly constructed during the previous century and are presently undergoing modernization and expansion efforts. However, this presents a challenge due to their core components being tailored to the outdated model of system services. This model assumes energy generation from centrally managed units (traditional power plants like coal-fired ones), which then flows through transmission system operators (TSOs), and distribution system operators (DSOs), and finally reaches consumers. The system’s flexibility is maintained by Automatic Frequency and Power Control (ARCM) systems, where generating units adjust their power output according to momentary consumption. Predictions based on statistical data are employed to enhance regulation processes.

During the power system’s inception, there were few distributed generation sources to consider within the power balance. However, with technological advancements, heightened ecological consciousness, shifts in fossil fuel markets, and the pursuit of energy autonomy, the landscape has transformed. A variety of such sources, including solar and wind farms, along with diverse forms of cogeneration, have emerged. In a decentralized power system, flexibility becomes even more critical, albeit challenging to achieve. This demands intricate, intelligent automation systems, consumer participation, and efficient energy storage mechanisms.

Dispersed energy sources

Presently, the dominant share of distributed energy sources in Poland comprises renewable energy sources (RES), particularly photovoltaic setups. A defining trait of these sources lies in their uncontrollable nature, as well as the challenge of accurately predicting their energy generation patterns. The presence of distributed generation also translates to a two-way energy flow within the distribution network. In power systems heavily reliant on RES for energy production, accurate weather forecasts become indispensable, alongside consumption predictions. However, the reliability of weather forecasts isn’t always consistent. All of these factors underscore the critical need for precise responses to local shifts in power flow. Neglecting such shifts can lead to excessive voltage and frequency fluctuations, potentially causing RES installations to shut down temporarily precisely when their energy generation potential is at its peak. These circumstances prove unfavorable for prosumers due to incurred losses and for local consumers grappling with voltage instability.

Given the widespread adoption of RES installations, maintaining pace with network modernization to accommodate diverse connection requirements becomes a formidable challenge. Consequently, prospective prosumers frequently encounter demanding prerequisites based on their installation’s location and connected power capacity. An alternative approach to encourage high levels of self-consumption of generated energy among distributed generation installation owners involves recent alterations in energy billing methods. This shift results in considerably lower compensation for energy supplied to the grid.

The impact of energy storage on the flexibility of the power system

Energy storage has emerged as an increasingly prevalent method to uphold the stability of electricity parameters delivered to consumers and to efficiently manage generated power. In the era of significant distributed generation, energy storage has become an indispensable component of the power grid.

These storage systems accumulate surplus energy when generation surpasses demand and release it when the situation reverses. Additionally, they can be harnessed to take advantage of variable energy prices, charging during cheaper periods and discharging during more expensive times. As a result, energy storage significantly enhances the flexibility of the power system. When prosumers, who both produce and consume energy, employ energy storage to store excess energy from their RES installations, the need to shut down these installations due to excessive generation diminishes. Furthermore, energy storage can postpone the necessity for expanding and modernizing the power system to accommodate new installations.