We present a new magnetometry method integrating an ensemble of nitrogen-vacancy (NV) centers in a single-crystal diamond with an extended dynamic range for monitoring a fast changing magnetic-field. The NV-center spin resonance frequency is tracked using a closed-loop frequency locked technique with fast frequency hopping to achieve a 10 kHz measurement bandwidth, thus allowing for the detection of fast changing magnetic signals up to 0.723 T/s. This technique exhibits an extended dynamic range subjected to the working bandwidth of the microwave source. This extended dynamic range can reach up to 4.3 mT, which is 86 times broader than the intrinsic dynamic range. The essential components for NV spin control and signal processing, such as signal generation, microwave frequency control, data processing, and readout, are integrated in a board-level system. With this platform, we demonstrate a broadband magnetometry with an optimized sensitivity of 4.2 nT Hz^−1/2. This magnetometry method has the potential to be implemented in a multichannel frequency locked vector magnetometer suitable for a wide range of practical applications, such as magnetocardiography and high-precision current sensors.

Magnetic field sensors based on quantum effects have shown superior performance in sensitivity, wherein the nitrogen-vacancy center in diamond has emerged as a microfabrication compatible solid-state platform for measuring magnetic fields at room temperature. Here, a closed-loop current sensor based on a compact diamond sensor is presented. Adapting dual-frequency driving mode and magnetic balance approach, a magnetic-temperature dual-loop architecture is established to extend the dynamic range and suppress the temperature drift, simultaneously. The proposed current sensor demonstrates an accuracy of 0.061% at a measuring range of ±1000 A. An isolation factor of 30.3 dB for temperature against magnetic field is obtained via the dual-loop calibration. The closed-loop strategy permits rapid adjustment of the output signal to align with fluctuations in the primary current and the response speed is achieved up to 107.6 kA·s ^-1 . Our proposed closed-loop current sensor has potential applications in power grid and electric vehicle monitoring systems.

In power network systems, there is an urgent demand for highly accurate and miniaturized sensors, owing to their high safety level and limited installation space. Current sensors in high‐voltage grids are required to accommodate harsh environments and provide accurate measurements of several kiloamperes. Thus, this study proposed an integrated quantum diamond sensor to facilitate high‐accuracy, large‐dynamic‐range current measurements. The design incorporated optical fiber and directional microwave (MW) antennas to drive the diamond sensor, which significantly reduced the size and power consumption on the high‐voltage side. Remote‐control and demodulation systems are installed more than 10 m away from the low‐voltage side. The proposed approach achieved zero power consumption on the high‐voltage side and ensured efficient signal transmission. A passive diamond probe manufactured using microfabrication processes facilitated miniaturization and practical deployment. Through parameter optimization, a magnetic detection sensitivity of 4.86 nT·Hz^−1/2 is achieved at a safe distance of 11 m, which can be further optimized to 0.77 nT·Hz^−1/2 with enhanced MW power. This sensor achieved a current measurement error of ±0.4% in the 1000 A measurement range. Thus, this study provides a new solution for the application of diamond quantum sensors in power systems.

Diamond nitrogen-vacancy (NV) center has been widely studied as a high-sensitivity solid-state quantum sensor with a wide range of applications, including magnetometry, thermometry manometry, and chemical sensing. However, its application in practical scenarios remains challenging due to difficulties of component manufacturing, miniaturization, and integration for NV control and readout. Here, we demonstrate an all-electric driving diamond sensor fabricated using standard microfabrication processes and micro-assembly, achieving integration of five key components—laser diode, diamond, microwave antenna, long pass filter, and photodiode in a hermetically sealed package case, with dimensions of 2.72 cm3. The integrated diamond magnetometer achieved a magnetic sensitivity of 2.25 nT · Hz−1/2. Additionally, the inherent crystallographic axes of the diamond are used to simultaneously detect vector magnetic field signals. The design and fabrication process allows for wafer-level assembly, enabling low-cost mass-production and easy integration with peripheral circuits.

The connection between the doubly-fed wind power generators (WPGs) and the grid affects the security of the grid and generator. The maximum. wind power tracking (MWPT) affects the efficiency of the generators connected to the grid. This paper deals with two problems above. Based on a no-load model of doubly-fed induction generator (DFIG), and by applying a vector control technique called stator flux orientation vector control technique (SFOVCT), a grid-connection control strategy for doubly-fed WPGs is developed. According to the wind turbines (WTs) principles and DFIG power characteristics, the paper investigates the MWPT principles based on generator power control, and then introduces an algorithm for active power command of the DFIG. Based on SFOVCT and general-purpose model for DFIG, this novel algorithm enables decoupled output power of DFIG, and then an integrated control strategy for MWPT are developed The grid-connection and the MWPT for the DFIG are presented for a 15-kw laboratory set up, and the experiment results verified the validity and feasibility of the theoretic analysis, as well as the control strategy.