Anti-islanding measures and frequency/voltage emergency control devices

(1) Inverter anti-islanding protection

Inverters must have anti-islanding protection functionality. The anti-islanding protection for inverters in photovoltaic power plants primarily employs detection methods such as frequency deviation, power variation, and voltage phase jumps, with response times ranging from 100ms to 1s. Islanding phenomenon protection is the most critical and highest-priority protection in grid-connected inverter systems. It requires that the photovoltaic system must cease supplying power to the grid within 2 seconds of grid voltage loss.

(2) Frequency/voltage emergency control device

During islanding incidents, frequency and voltage undergo abrupt changes. This phase requires the installation of a frequency/voltage emergency control device on the 10kV output side of the photovoltaic power plant. The device must feature slip differential blocking functionality and short-circuit judgment capability.

This frequency/voltage emergency control device is used for emergency grid frequency and voltage control during extreme situations. It is designed for scenarios requiring urgent control of abnormal grid frequency/voltage conditions, such as low-frequency/low-voltage separation or high-frequency generator tripping. Key functional requirements include:

1. Low-frequency/low-voltage separation function: When grid frequency drops to the set value, the device should execute separation to restore normal frequency. In cases where severe faults or separation in grids with significant active power deficits cause unrecoverable voltage collapse, low-frequency separation may fail to operate. Under such circumstances or during system reactive power imbalance, low-voltage separation functionality should be activated.

2. High-frequency/high-voltage generator tripping function: During system overfrequency or overvoltage conditions, the device should perform generator tripping, separation, or rapid steam valve control functions.

3. Out-of-step oscillation separation function: When power plants lose synchronization with the main system causing out-of-step oscillations, the device must simultaneously trip all parallel connections between generating units and the main grid, separating the primary power delivery interface of the plant (i.e., disconnecting both lines; during maintenance, only operational tie-lines are separated).

4. Measurement capability: The device should simultaneously measure three-phase voltage, three-phase current, frequency, active power, reactive power, and phase angle from two bus sections or tie-lines as decision-making criteria.

5. Remote functionality: The device requires reserved communication interfaces or remote trip contact inputs for executing remote tripping commands or load shedding orders; it should also transmit load reduction or separation commands remotely.

6. The device must record essential information (such as fault waveform data) and transmit it through interfaces; stored information should not be lost and should be reproducible. Recorded data primarily serves to verify normal operation and proper functioning of device components.

7. The device should feature automatic time synchronization capability.

Jiangsu Mangzhong Construction Co., Ltd. is a comprehensive energy service provider specializing in the photovoltaic field, dedicated to being a smart energy enterprise engaged in photovoltaic power plant investment, development, design, construction, intelligent operation and maintenance, professional consulting services, and photovoltaic equipment recycling.

Company Name: Jiangsu Mangzhong Construction Co., Ltd.

Business Scope: Photovoltaic power plant EPC and solar power station investment

Landline: 025-5888 3737

Mobile: 159 5163 4545

Official Website: http://www.mangz.cn