Zengping Wang

Adaptive Damping Control of Inter-Area Oscillations Based on Federated Kalman Filter Using Wide Area Signals

The application of phasor measurement unit (PMU) measurements and adaptive wide-area damping control based on federated Kalman filters are investigated. The Kalman filters used for estimating the operating conditions are federated using chi-square variables and a confidence interval. When the power system is operating precisely at a preselected operating point, only the corresponding controller is active. When the power system is not exactly at the operating point, a combined controller is formed. A 68-bus, 16-generator system is used as a test system. Three DC lines, three ESDs, and remote PMU frequencies as added inputs are used as the example control. The simulation results demonstrated the good performances for adaptive damping the inter-area oscillation modes.

A Two Terminal Network-Based Method for Discrimination Between Internal Faults and Inrush Currents

A novel scheme based on two-terminal network to distinguish the inrush current from the internal fault current in the power transformer is proposed. By eliminating the mutual flux linkage in the transformer loop equation, a two-terminal network containing only the winding resistance and the leakage inductance is generated. According to the absolute difference of active power (ADOAP) flowing into and consumed by the two-terminal network, the criterion to identify the internal fault is developed. A total of 162 experimental cases have been tested and the proposed method is able to reliably and accurately discriminate internal faults from inrush currents with easy implementation.

Identifying Transformer Inrush Current Based on Normalized Grille Curve

A novel algorithm for discrimination between inrush currents and internal fault currents by utilizing the normalized grille curve is proposed. First, the calculation method of the normalized grille curve is presented. Then, two schemes to discriminate the inrush currents from the internal faults in the time and frequency domains are, respectively, developed. A total of 268 experimental measurements have been tested on an YNd11-connected transformer. The results indicate that the proposed technique is able to reliably and accurately distinguish inrush currents from internal faults with easy implementation. Furthermore, the new method is not affected by the saturation of current transformers.

Application of Dual Youla Parameterization Based Adaptive Wide-Area Damping Control for Power System Oscillations

An adaptive damping control scheme based on the dual Youla parameterization is proposed in this paper for inter-area low frequency oscillations. First, a set of observer-based feedback controllers are pre-designed using H2 /H∞ robust control method for a set of nominal operating conditions. Second, the power system and controllers are parameterized using Youla method, respectively. Finally, online measurements are utilized to identify the changing dynamics and adjust the parameterized controllers to adapt to changing operating conditions through the updated Youla parameters. A 127-bus equivalent of the Western Electricity Coordinating Council (WECC) system with three additional controllers of energy storage system is employed as a test system. The results of frequency domain and time domain of different contingences demonstrate the effectiveness and robustness of the Youla based adaptive control scheme.

An adaptive distance protection scheme for distribution system with distributed generation

The value setting of the traditional distance protection has become very difficult for the distribution system with distributed generators (DGs) owing to the randomness of the DG output power. This paper proposes a new adaptive distance protection scheme to solve this problem. Firstly, on the basis of the connected point of DGs, the protected feeders are divided into different zones, with adaptive distance protection configured at the upstream side of DG. Then, based on a fault characteristic analysis of the distribution system with DG, the adaptive distance protection scheme for the distribution system with DG is studied to solve this problem. The results show that this scheme can automatically calculate the settings according to the operation mode and the output power of DG with no need for communication. Compared with the traditional adaptive protection scheme, the performance of this method is greatly improved. Simulation results on a 10 kV distribution system have verified the validity of the scheme proposed.

Multi-Polytope-Based Adaptive Robust Damping Control in Power Systems Using CART

An adaptive damping control scheme based on classification and regression tree (CART) using wide-area signals is proposed in this paper. Different polytopes are chosen using classification trees. Next, a family of robust polytopic controllers is designed off-line. Finally, using regression trees and PMU data, the desired polytopic controller is identified in real time. A 16-generator, 68-bus system is used as the test system. Remote signals obtained from PMUs are employed for control purposes. The simulation results demonstrate that the proposed adaptive control scheme is able to provide adequate damping for the oscillation modes of interest with respect to varying operating conditions without any prior knowledge of the post-disturbance state.

An adaptive protection scheme for distributed systems with distributed generation

An adaptive protection scheme using digital relays with a communication network is proposed for the protection of the distributed systems. The impact of distributed generators on protection coordination is first discussed. Then, an adaptive protection scheme is proposed for distributed systems with distributed generation (DG). Simulated results on an actual distribution system show that the proposed approach can perform adaptive primary and backup protection functions under both balanced and unbalanced fault conditions. Also, the proposed approach is adaptive to the fault types as well as capacities of DG. Compared with the traditional current protection scheme, the primary and backup protection regions have been extended considerably.

Application of Wide-area Collocated Control Technique for Damping Inter-area Oscillations Using Flexible AC Transmission Systems Devices

Abstract A wide-area collocated control scheme for damping inter-area oscillations employing multiple flexible AC transmission systems devices is presented. At first, the most effective stabilizing signals are selected by participation factors of a control matrix. Also, these signals are coordinated in a wide-area damping controller to achieve multi-objective collocated control. Then, a systematic procedure for selecting the feedback gain of control design is suggested. A 16-machine, 68-bus study system with a static var compensator, a thyristor controllable series capacitor, and a thyristor controllable phase-shifting transformer at different locations is considered. The damping performance of the controllers is examined in the frequency and time domains for various operating scenarios. The simulation results also show that the collocated control scheme is able to effectively damp out inter-area oscillations following possible disturbances without any prior knowledge about the specific post-disturbance dynamics. The robustness with respect to uncertainty of system models, variations of time delays, and the loss of communication links is evaluated.

A New Adaptive Voltage Protection Scheme for Distribution Network With Distributed Generations

A new adaptive voltage protection scheme suitable for distribution networks with potential distributed generation (DG) inserts is proposed in this paper. Firstly, the intelligent electronic devices (IEDs) are utilized to store relevant line parameters, obtain real-time voltage and current data, and facilitate communication among the IEDs. On this basis, the adaptive voltage primary and backup protection scheme are put forward according to the relationship between the before-and-after-fault phase voltage difference and the phase current. Simulation results show the automatically adaptive relaying by the proposed protection scheme under different system operation conditions and fault types, and verify the immunity of the proposed method to the introduction and output variation of DG. Furthermore, compared with traditional voltage protection, the proposed protection scheme extends the protection range to a considerable degree.

Location Method for Interline and Grounded Faults of Double-Circuit Transmission Lines Based on Distributed Parameters

This paper presents a one-terminal fault-location method for interline and grounded faults of double-circuit transmission lines considering the distributed parameter. The influence of mutual inductances is taken into account in a six-sequence network of a distributed parameter model. And the compensation voltage with the help of a co-rotating zero-sequence compensation coefficient and reverse zero-sequence compensation coefficient is defined. Then, the phase and the amplitude of fault voltage are calculated by utilizing the relationship between measured reverse sequence current and fault reverse sequence current. Then, fault-location function is constructed by utilizing the measured voltage, measured current, and estimated fault voltage. Finally, the fault location is identified by solving the phase mutation point of fault-location function. The simulation results show that the method can be widely used for interline and grounded faults without the information of other substations. In addition, this method is merely influenced by fault location, transition resistance, source impedance, and is able to locate the fault accurately and is easy to implement.