20160430-IRENA-Scaling_up_Variable_Renewable_Power_The_Role_of_Grid_Codes_106页_14mb

Grid codes are technical regulations essential for integrating variable renewable energy (VRE) like wind and solar power into electricity systems. This report, by IRENA (2016), examines their role, development, implementation, and evolution in response to increasing VRE penetration. Grid codes ensure power system stability, security, and reliable electricity supply by setting technical requirements for VRE generators, which differ from conventional sources due to their variability and technology-based controls.

Key areas covered include:

Definition, Purpose, and Function

Grid codes set rules for power system and energy market operations, maintaining operational stability, security, and efficient wholesale markets. They encompass various types, including grid connection codes for VRE, which focus on technical and design standards for wind and solar generators to ensure compatibility with system dynamics such as voltage, frequency, and fault ride-through behaviors.

Development and Implementation

Grid codes are developed through a process involving policymakers, regulators, system operators, manufacturers, and other stakeholders. This includes technical studies, data collection, expert drafting, stakeholder consultation, certification mechanisms, and enforcement, often through legal frameworks. Effective implementation requires mechanisms like compliance verification, on-site inspections, or performance testing, adapted to country-specific contexts.

Technical Requirements Relevant to VRE Integration

Technical requirements address challenges from VRE variability, including operation ranges and tolerances for voltage (typically ±10% ± nominal) and frequency (e.g., ±2% in large systems). This includes power quality (minimizing flicker and harmonics), reactive power capability for voltage control, grid code verification processes, frequency support or frequency control reserves (notable for synthetic inertia applications), and fault ride-through behavior (requiring VRE to remain connected during faults). These requirements evolve with system characteristics and VRE share.

Case Studies from Various Countries

Experiences from countries like Germany, Ireland, Australia, Barbados, and the Philippines demonstrate how grid codes adapt to local conditions. High-VRE systems (e.g., Ireland) demand stricter control capabilities for frequency and reactive power, while low-penetration systems like Barbados are revising codes for increased FRT and frequency support. Lessons learned, such as the German 50.2 Hz problem from overly strict early requirements, underscore the need for foresight and the value of leveraging previous R&D to simplify requirements.

Relationship Between Regional and National Grid Codes

The introduction of regional grid codes (e.g., the ENTSO-E Network Codes) aids harmonization across countries, reducing costs through standardized requirements without eliminating national specifics. Harmonization occurs through international standards and regional initiatives, enabling more efficient cross-border energy trade and grid operation.

Additional Considerations and Recommendations

Challenges include ancillary services provision (formerly handled mainly by conventional generators), technical requirements for different generator types and sizes, and the need for regular grid code revisions to align with technological advancements. Recommendations emphasize local needs assessment, explicit stakeholder engagement in the grid code process, harmonization efforts, ongoing compliance verification and consistent reinforcement of grid code documentation for efficient updates.

Grid code implementation allows countries to pool resources and benefit from global knowledge, facilitating reliable VRE integration while ensuring power system security and efficiency.