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Guidelines for the implementation of power oscillation damping controllers in power converters
Javier Renedo, Macarena Martín Almenta, Sergio Martínez Villanueva, Agustín Díaz-García, Antonio Cordón, Davide Gotti
TL;DR
The paper addresses how to implement and evaluate POD controllers in GFL power converters when controller performance depends on settings and detailed system information may be unavailable. It proposes guidelines, synthetic-system compliance criteria, and simulation-based evaluation, finding that POD controllers met the stated robustness and effectiveness criteria and could damp oscillations in large-scale systems.
Problem
POD controller effectiveness depends strongly on settings, while owners and manufacturers may lack detailed large-scale power-system models for reliable tuning and assessment.
Method
The paper develops implementation guidelines and evaluates POD-P, POD-Q, and POD-PQ using a synthetic two-area system, Spanish NTS methodology, and RMS-based simulations.
Results
POD-P and POD-Q achieved damping ratios above 5% across the tested line-reactance range and damping-ratio increments above 5% at X_L=0.6 pu.
Takeaways & Limitations
Appropriate synthetic systems, methodologies, and compliance criteria could support effective damping of electromechanical oscillations by converter-based POD controllers in large-scale power systems.
Takeaways & Limitations
The proposed evaluation method and compliance criteria are guidelines for good practice and have no regulatory value; the study focuses on GFL converters.
Abstract
from arXiv · showhide
One of the most effective ways to damp electromechanical oscillations in power systems is by means of supplementary controllers attached to the different devices in the power system is by means of power system stabilizers (PSS) in synchronous machines or by means of power oscillation damping (POD) controllers in facilities with power converters. In the recent years, the use of POD controllers in voltage source converters (VSCs) with grid-following (GFL) control has been investigated. Although the potential of POD controllers to help to damp inter-area oscillations in power systems is enormous, their correct implementation is not trivial, because their effectiveness is strongly linked to their settings. This paper provides guidelines for the implementation of POD controllers in power converters for application in real-world power systems. The paper proposes compliance criteria for POD controllers using a synthetic test system and a systematic methodology used in Spanish technical standard for monitoring compliance (NTS), considering practical considerations. The paper also includes numerical examples to illustrate compliance criteria for POD controllers in a synthetic test system. A generic power converter with grid-following (GFL) control is used for the analysis by simulation and POD controllers using modulation of active-power injection (POD-P), reactive-power injection (POD-Q) or both simultaneously (POD-PQ) will be analysed. Results were validated in a large-scale power system. The paper concludes that by using appropriate synthetic systems, methodologies and compliance criteria, POD controllers in power converters could be effective to damp electromechanical oscillation in large-scale power systems.
SUMMARY
The paper addresses implementation of power oscillation damping controllers for power converters, focusing on electromechanical oscillations in power systems.
- POD controllers are supplementary controllers used with power converters to damp electromechanical oscillations.
- The paper is identified as a CIGRE Paris Session contribution on implementing POD controllers in power converters.
1 Introduction
The introduction motivates POD controllers for damping electromechanical oscillations, while emphasizing that their settings and evaluation are challenging when detailed power-system models are unavailable. The paper therefore develops guidelines and evaluates them using synthetic systems and large-scale validation.
- Electromechanical oscillations include local and inter-area modes involving groups of coherent generators.
- PSSs support damping in synchronous machines, while POD controllers serve facilities containing power converters.
- POD controller performance is strongly linked to settings, which complicates implementation when owners or manufacturers lack detailed large-scale system models.
- A Spanish TSO working group developed technical specifications, implementation guidelines, and compliance criteria for POD controllers.
- The paper studies POD-P, POD-Q, and POD-PQ using a synthetic two-area system and validates results in a large-scale power system.
- The paper focuses on POD controllers in GFL converters because GFL technology is mature, whereas GFM requirements are still being developed.
2 POD controllers in power converters
The paper represents converter facilities generically as GFL devices equipped with active- and reactive-power POD controllers. Their implementation can vary, but the controllers must provide reliable electromechanical-oscillation damping and systematic performance evaluation.
- GFL device and controller structure: The generic GFL device represents a PPM, PPM-type electricity storage module, or shunt power converter connected to the power system.
- GFL device and controller structure: POD-P and POD-Q modify total active- and reactive-power setpoints by adding supplementary POD references to constant setpoints.
- GFL device and controller structure: Each POD controller has an input signal, a generic block diagram, a saturator, and a supplementary active- or reactive-power output.
- Implementation choices: Implementations may differ in block diagrams, location, input signals, and fixed or adaptive parameters.
- Implementation choices: Stakeholders and manufacturers may choose the controller implementation and tuning method provided the controller reliably contributes to damping electromechanical oscillations.
3 Evaluation of the performance of POD controllers
The evaluation uses a synthetic two-area system and Spanish NTS methodology to assess POD robustness and effectiveness under limited system information. Compliance is tested through damping-ratio thresholds and can be evaluated with small-signal or RMS time-domain models.
- Evaluation framework: Synthetic test systems provide a practical way to evaluate POD performance when detailed large-scale power-system models are unavailable.
- Synthetic test system: The NTS synthetic two-area system normalizes the evaluated GFL device to 1500 MVA and varies line reactance to reproduce electromechanical oscillations.
- Evaluation cases: The evaluation compares a base system, a GFL device without POD, POD-P, POD-Q, and POD-PQ cases.
- Acceptance criteria: Effectiveness requires a damping-ratio increment of at least 5% over base case B1 at X_L=0.6 pu.
- Evaluation framework: The criteria can be evaluated using small-signal stability analysis or nonlinear time-domain simulation with RMS models.
- Scope and status: The proposed evaluation method and criteria are guidelines for good practice and have no regulatory value.
4 Results: Synthetic two-area system and compliance criteria
The synthetic two-area system evaluates POD-P and POD-Q controllers under compliance scenarios. Both controllers improve electromechanical-mode damping and satisfy the stated robustness and effectiveness criteria, while Scenario 2 examines low- or negative-damping conditions.
- Test system: VSC-5 uses grid-following control with constant active- and reactive-power injections and is equipped with POD-P and POD-Q controllers.The converter is rated at 1500 MVA for normalization, and generic VSC models are used.
- Scenario 1: In Scenario 1, generator G1 operates with its PSS activated while POD-controller performance is evaluated against compliance criteria.This is the scenario used to assess the guide’s compliance criteria.
- Small-signal stability analysis: POD-P and POD-Q improve the electromechanical-mode damping ratio relative to base case B1 as line 2–3 reactance changes.The electromechanical mode shifts left in the complex plane for cases B2, B3, and B4.
- Compliance criteria: Damping ratios remain higher than 5% across all line-reactance values in the 0.1–1 Hz oscillation range, satisfying the robustness criterion.The criterion is assessed using the electromechanical mode under the four analyzed operating cases.
- Compliance criteria: For X_L = 0.6 pu, the damping-ratio increment exceeds 5%, satisfying the effectiveness criterion for POD-P and POD-Q.Table 3 quantifies the increment for each analyzed case.
- Scenario 2: Scenario 2 deactivates generator G1’s PSS to examine POD performance when electromechanical oscillations have low or negative damping.The scenario is intended for more detailed analysis rather than compliance-criterion quantification.
5 Case Study: Large-scale power system
The study validates POD-P/POD-Q controllers tuned with a synthetic system and compliance criteria in a calibrated large-scale European power-system model. The controllers contribute to damping the critical inter-area oscillation.
- 5 Case Study: Large-scale power system: The large-scale case uses detailed Iberian Peninsula and Continental Europe models calibrated to produce a low-damping East-Centre-West inter-area oscillation.The scenario is explicitly non-realistic and was calibrated for this study.
- 5 Case Study: Large-scale power system: Two 200 MVA grid-following VSCs are placed at arbitrary southern and central Iberian Peninsula buses for illustration.Their locations were selected because frequencies are monitored by PMUs.
- 5 Case Study: Large-scale power system: POD-P/POD-Q controllers contribute to damping the East-Centre-West inter-area oscillation in the large-scale system.Table 5 reports the damping ratio and frequency of the critical mode.
- 5 Case Study: Large-scale power system: POD-P/POD-Q controllers for VSC-1 and VSC-2 are tuned using the synthetic system and the compliance criteria described earlier.The same generic converter models and POD parameters are used, with only converter ratings changed.
- 5 Case Study: Large-scale power system: Non-linear time-domain simulations compare POD-PQ OFF with both POD-PQ controllers ON after a 594 MW / 229 MVAr load disconnection.The disturbance occurs at t = 1 s and is evaluated through generator-speed and VSC-frequency differences.
- 5 Case Study: Large-scale power system: The results support using appropriate synthetic systems, methodologies, and compliance criteria to damp electromechanical oscillations in large-scale power systems.This conclusion is presented as evidence from the large-scale validation.
6 Conclusions
The paper provides practical guidelines for implementing POD controllers in power converters. It proposes compliance criteria and validates the approach through synthetic-system simulations and a large-scale power-system study.
- 6 Conclusions: The paper proposes implementation guidelines and compliance criteria for POD controllers in power converters.The criteria use a synthetic test system and a systematic methodology from the Spanish technical standard for monitoring compliance.
- 6 Conclusions: Simulations analyze POD-P, POD-Q, and combined POD-PQ control using a generic grid-following power converter.The numerical examples illustrate the proposed compliance criteria in a synthetic test system.
- 6 Conclusions: Results are validated in a large-scale power system, supporting the practical application of the proposed approach.The validation complements the synthetic-system analysis.
- 6 Conclusions: With appropriate synthetic systems, methodologies, and compliance criteria, POD controllers could effectively damp electromechanical oscillations in large-scale power systems.The paper highlights practical interest when limited power-system information is available.