During the out-of-step oscillation process, the frequency of voltage at every point in power system changes continuously. In this paper, the voltage frequency variation regulation is analyzed in an equivalent two-terminal system whose two terminal potential amplitudes are not equal and all electrical component impedance angles are different. It is found that the bus voltages frequencies at different sides of out-of-step center own different characteristics. In order to use the frequency variation characteristics to construct the criterion of power system out-of-step protection, a fast frequency calculation algorithm is proposed, in which the frequency is calculated by toggling different formulas at different sampling points and the calculation accuracy are improved by the aid of CORDIC algorithm. The algorithm is easy to implement and the measurement errors can keep under a low level. Finally, a novel frequency based out-of-step protection with the wide area information is described. It can judge the occurrence of out-of-step oscillation in the first out-of-step oscillation cycle and determine the electrical component where the out-of-step center locates, which lays the foundation for the determination of out-of-step splitting section for complex power systems. The test results with IEEE39 system in PSCAD verify the correctness of the proposed protection.

Using the wide area information obtained from phasor measurement units, a novel out-of-step splitting protection is proposed. In order to analyze the different characteristic of bus voltage phase angles, a new coordinate system is introduced. In this coordinate system, all of the converted bus voltage phasor ends are stable, while only the common beginning is moving during the out-of-step oscillation process. Its conformal property guarantees the voltage phase angle differences in the old and new coordinate systems are equal. After the coordinate transformation, the formula about the converted power network neutral point trajectory is derived. The intersection of the trajectory and the broken line which connects the bus voltage phasor ends is the out-of-step center. All of the buses are divided into two parts by the out-of-step center. Through a series of proofs, it is found that the absolute values of the bus voltage phase angles in one part are always smaller than 110°, while the voltage phase angles of the rest buses vary from -180° to 180°. These different characteristics could be used to group these buses and locate the out-of-step center. It is very simple because only the voltage phase angle information is applied, and there are no complex mathematical operations. Finally, a novel out-of-step splitting protection scheme is given. The digital simulation results prove the proposed scheme is efficient.

The dynamic model for a bidirectional driven float-type wave power generation system design is presented in this paper. The gravity, buoyancy and drag force acting on the wave energy converter (WEC) are all analyzed. The analytical expression of the torque applied on the rotor is given based on a linear model of the switched reluctance generator (SRG). The SRG usually rotates with low velocity in the WEC system. In this situation, current chopping control (CCC) is adopted with fixed turn-on angle and turn-off angle control mode to have a quick response for SRG. Further, in order to make the float keep in phase with the wave so as to improve the power generation efficiency, the reference current is dynamically adjusted according to the wave motion at all working stages. Then maximum power point tracking (MPPT) of system is achieved. A simulation model is developed in MATLAB for the bidirectional driven float-type wave power generation system with real wave statistical characteristics taken into account. Simulation results show that the WEC can output desired torque periodically with high efficiency and good adaptability. Therefore, the feasibility of applying a SRG in a WEC is also verified.

This paper aims to assess the efficacy of the Harris Hawk Optimization (HHO) algorithm within the domain of photovoltaic (PV) power-generation systems. The focus lies in elucidating how the HHO algorithm optimizes maximum-power-point tracking (MPPT) and augments the performance of grid-connected PV systems. Initially, in the MATLAB/Simulink environment, a comparison is made between the HHO algorithm and two other extensively utilized methods for maximum-power-point tracking (MPPT): Perturb and Observe (P&O) and Particle Swarm Optimization (PSO). Preliminary findings indicate the HHO algorithm’s notable advantages in efficiency and speed over the other algorithms. Furthermore, by establishing a practical experimental platform and synchronously verifying outcomes through simulation, we conducted a comprehensive assessment of the HHO algorithm on a single-phase full-bridge-inverter grid-connected system. Results show the HHO algorithm’s exceptional optimization capabilities, which displays superior adaptability and ability to adjust to varying external conditions.