[Paper Review] A System Model-Based Approach for the Control of Power Park Modules for Grid Voltage and Frequency Services

Bogdan Marinescu, Elkhatib Kamal+1 more|arXiv (Cornell University)|Jul 5, 2021

Microgrid Control and Optimization37 references4 citations

TL;DR

This paper proposes a system model-based control approach for Power Park Modules (PPMs) that unifies voltage and frequency dynamics into a single small-scale model, enabling full participation in grid ancillary services. By using H-infinity robust control and time-scale-based coordination, the method achieves superior performance over classical converter-level controls, enabling PPMs to match synchronous generators in frequency and voltage support with full market and regulatory compliance.

ABSTRACT

A new control approach is proposed for the grid insertion of Power Park Modules (PPMs). It allows full participation of these modules to ancillary services. This means that, not only their control have some positive impact on the grid frequency and voltage dynamics, but they can effectively participate to existing primary and secondary control loops together with the classic thermal/inertia synchronous generators and fulfill the same specifications both from the control and contractual points of view. To achieve such level of performances, a system approach based on an innovatory control model is proposed. The latter control model drops classic hypothesis for separation of voltage and frequency dynamics used till now in order to gather these dynamics into a small size model. From the system point of view, dynamics are grouped by time-scales of phenomena in the proposed control model. This results in more performant controls in comparison to classic approaches which orient controls to physical actuators (control of grid side converter and of generator side converter). Also, this allows coordination between control of converters and generator or, in case of multimachines specifications, among several PPMs. From the control synthesis point of view, classic robust approaches are used (like, e.g., H-infinity synthesis). Implementation and validation tests are presented for wind PPMs but the approach holds for any other type of PPM. These results will be further used to control the units of the new concept of Dynamic Virtual Power Plant introduced in the H2020 POSYTYF project.

Motivation & Objective

• Address the limited participation of renewable-based Power Park Modules (PPMs) in grid frequency and voltage ancillary services due to decoupled control of voltage and frequency dynamics.
• Overcome the limitations of classical control approaches that separate voltage and frequency control, leading to suboptimal performance and poor coordination.
• Enable PPMs to fully participate in secondary frequency and voltage regulation with the same contractual and operational responsibilities as synchronous generators.
• Develop a unified system-level control model that captures both voltage and frequency dynamics across multiple time scales for improved coordination and robustness.
• Ensure robust performance under grid disturbances and variable renewable conditions through advanced multivariable control synthesis (H-infinity).

Proposed method

• Propose a novel system model that integrates voltage and frequency dynamics of PPMs (including grid-side and machine-side converters and PMSG) into a single, small-scale representation, eliminating classical separation assumptions.
• Structure the control model around time-scale decomposition of system dynamics, enabling hierarchical and coordinated control actions across different physical phenomena.
• Implement H-infinity robust control synthesis to ensure stability and performance under uncertainties, using Linear Matrix Inequalities (LMIs) for controller design.
• Distribute control objectives based on time-scale dynamics rather than assigning them to individual actuators (e.g., grid-side or machine-side converters), improving coordination and performance.
• Integrate droop control, virtual inertia (hidden inertia), and MPPT strategies within the unified framework, with dynamic gain adaptation for frequency support.
• Use look-up tables and feedback relationships (e.g., between power reference and pitch angle) to enable fast, delay-free response in deloading and inertial control.

Experimental results

Research questions

• RQ1 How can voltage and frequency dynamics in PPMs be effectively unified in a control model to improve ancillary service performance?
• RQ2 To what extent can PPMs achieve full participation in secondary frequency and voltage regulation comparable to synchronous generators?
• RQ3 What control architecture enables robust, coordinated action across multiple PPMs and their internal converters under grid disturbances?
• RQ4 How does time-scale-based control distribution improve performance over classical actuator-level control allocation?
• RQ5 Can H-infinity synthesis ensure robustness and stability in the presence of grid uncertainties and renewable variability?

Key findings

• The proposed system model-based control approach successfully unifies voltage and frequency dynamics into a single, compact model, eliminating the need for classical separation of concerns.
• H-infinity control synthesis ensures robust performance and stability across a wide range of operating conditions and grid disturbances.
• The method enables PPMs to provide full primary and secondary frequency and voltage support, matching the capabilities of conventional synchronous generators.
• Time-scale-based control distribution results in superior dynamic response and coordination compared to classical actuator-level control strategies.
• The approach supports fast, delay-free implementation of droop and inertial control through feedback relationships between power reference and pitch angle.
• Simulation results demonstrate effective participation in grid support services, including RoCoF mitigation and voltage regulation, under large disturbances and variable wind conditions.