Solution of the Optimal Reactive Power Flow Problem Using a Discrete-Continuous CBGA Implemented in the DigSILENT Programming Language

The problem of the optimal reactive power flow in transmission systems is addressed in this research from the point of view of combinatorial optimization. A discrete-continuous version of the Chu & Beasley genetic algorithm (CBGA) is proposed to model continuous variables such as voltage outputs in generators and reactive power injection in capacitor banks, as well as binary variables such as tap positions in transformers. The minimization of the total power losses is considered as the objective performance indicator. The main contribution in this research corresponds to the implementation of the CBGA in the DigSILENT Programming Language (DPL), which exploits the advantages of the power flow tool at a low computational effort. The solution of the optimal reactive power flow problem in power systems is a key task since the efficiency and secure operation of the whole electrical system depend on the adequate distribution of the reactive power in generators, transformers, shunt compensators, and transmission lines. To provide an efficient optimization tool for academics and power system operators, this paper selects the DigSILENT software, since this is widely used for power systems for industries and researchers. Numerical results in three IEEE test feeders composed of 6, 14, and 39 buses demonstrate the efficiency of the proposed CBGA in the DPL environment from DigSILENT to reduce the total grid power losses (between 21.17% to 37.62% of the benchmark case) considering four simulation scenarios regarding voltage regulation bounds and slack voltage outputs. In addition, the total processing times for the IEEE 6-, 14-, and 39-bus systems were 32.33 s, 49.45 s, and 138.88 s, which confirms the low computational effort of the optimization methods directly implemented in the DPL environment.

Minimizing Power Loss Using Modified Artificial Bee Colony Algorithm

Electrical energy losses are found in any part of the power system. In the power system, it is essential to minimize the real power loss in transmission lines. The voltage deviation at the load buses through controlling the reactive power flow is very important. This ensures the secured operation of power systems regarding voltage stability and the economics of the process due to loss minimization. In this paper, the Modified Artificial Bee Colony (MABC) algorithm is implemented to solve the power system's optimal reactive power flow problem. Generator bus voltages, transformer tap positions, and settings of switched shunt of compensators are used as decision variables to control the reactive power flow. These control variable values are adjusted for loss reduction. MABC algorithm is tested on the standard IEEE-30 bus test system. The results are compared with Firefly algorithm (FA) and Artificial Bee Colony (ABC) algorithm method to prove the effectiveness of the newest algorithm. The power loss results are quite productive, and the algorithm is the most efficient than the other methods such as ABC algorithm and FA algorithm. These results are produced by Matlab 2017b.

Impact of Changes in a Distribution Network Nature on the Capacitive Reactive Power Flow into the Transmission Network in Slovakia

The main emphasis in the operation of an electricity system is placed on its safe and reliable operation. The flow of reactive power in a network can affect voltage conditions in individual nodes of the transmission system. In recent years, there have been changes in the network that have resulted in increased capacitive reactive power flows from lower voltage levels to higher ones. These flows can cause the voltage to rise above the limit. This paper examines recent changes in the reactive power transmission in the network, especially at lower voltage levels. The possible impact of these changes on the flow of capacitive reactive power at higher voltage levels is analyzed. This paper also presents a description and the simulated impact of power lines at different voltage levels on reactive power flows. Real measurements of different types of consumers at the low-voltage (LV) level are analyzed. Finally, a simulation model was created to simulate the impact of a customer’s power contribution to the reactive power flows from the point of view of a 110 kV voltage node. This node is characterized as a supply point.

Review on Control Techniques for EV Bidirectional Wireless Chargers

Due to their flexibility, Electric Vehicles (EVs) constitute an important asset for the integration of renewable energy sources in the Smart Grid. In particular, they should have a dual role: as a controllable load and as a mobile generator with a low inertia. To perform these tasks, chargers must provide the electronics with a power flow from the grid to the vehicle and vice versa. This bidirectionality can also be implemented in wireless chargers. The power converters, the compensation networks and the coil misalignment must be considered when designing the control of these systems. This paper presents a review about the proposed algorithms to control the active and the reactive power flow in a bidirectional wireless charger.

State-of-the-Art of Optimal Active and Reactive Power Flow: A Comprehensive Review from Various Standpoints

Optimal power flow (OPF), a mathematical programming problem extending power flow relationships, is one of the essential tools in the operation and control of power grids. To name but a few, the primary goals of OPF are to meet system demand at minimum production cost, minimum emission, and minimum voltage deviation. Being at the heart of power system problems for half a century, the OPF can be split into two significant categories, namely optimal active power flow (OAPF) and optimal reactive power flow (ORPF). The OPF is spontaneously a complicated non-linear and non-convex problem; however, it becomes more complex by considering different constraints and restrictions having to do with real power grids. Furthermore, power system operators in the modern-day power networks implement new limitations to the problem. Consequently, the OPF problem becomes more and more complex which can exacerbate the situation from mathematical and computational standpoints. Thus, it is crucially important to decipher the most appropriate methods to solve different types of OPF problems. Although a copious number of mathematical-based methods have been employed to handle the problem over the years, there exist some counterpoints, which prevent them from being a universal solver for different versions of the OPF problem. To address such issues, innovative alternatives, namely heuristic algorithms, have been introduced by many researchers. Inasmuch as these state-of-the-art algorithms show a significant degree of convenience in dealing with a variety of optimization problems irrespective of their complexities, they have been under the spotlight for more than a decade. This paper provides an extensive review of the latest applications of heuristic-based optimization algorithms so as to solve different versions of the OPF problem. In addition, a comprehensive review of the available methods from various dimensions is presented. Reviewing about 200 works is the most significant characteristic of this paper that adds significant value to its exhaustiveness.

Power Flow Management by Active Nodes: A Case Study in Real Operating Conditions

The role of distributor system operators is experiencing a gradual but relevant change to include enhanced ancillary and energy dispatch services needed to manage the increased power provided by intermittent distributed generations in medium voltage networks. In this context, the paper proposes the insertion, in strategic points of the network, of specific power electronic systems, denoted as active nodes, which permit the remote controllability of the active and reactive power flow. Such capabilities, as a further benefit, enable the distributor system operators to provide ancillary network services without requiring any procurement with distributed generation systems owners. In particular, the paper highlights the benefits of active nodes, demonstrating their capabilities in reducing the inverse power flow issues from medium to high voltage lines focusing on a network cluster including renewable energy resources. As a further novelty, this study has accounted for a real cluster operated by the Italian distributor system operator Areti. A specific simulation model of the electrical lines has been implemented in DigSilent PowerFactory (DIgSILENT GmbH–Germany) software using real operating data obtained during a 1-year measurement campaign. A detailed cost-benefit analysis has been provided, accounting for different load flow scenarios. The results have demonstrated that the inclusion of active nodes can significantly reduce the drawbacks related to the reverse power flow.

Green energy transaction assessment on individual customer based on power factor correction coefficient

In this paper Power factor correction coefficient based transmission pricing is proposed to analyze an individual customer’s effect due to green energy transactions in existing power system. In this novel approach power factor correction coefficient is calculated for each customer under every transaction. This power factor correction coefficient is then added in conventional embedded cost distance based MW-mile and MVA-mile method for transmission pricing calculation for both active and reactive power flow through transmission line. This new proposed transmission pricing method calculate transmission charges for each customer and also help an ISO (independent system operator) to decide whether transaction increases or decreases the transmission cost. On the basis of performance of transaction an ISO can penalize or reward them. Proposed analysis is implemented on a 3-area IEEE-30 bus system with seven tie-lines in MATLAB environment. To show the effectiveness of the proposed method the results are compared with and without power factor correction based transmission pricing for each customer.

UHVDC-Technology Future of India Electricity Transmission

it's proposed to use highly complex grid controllers to include power grids into one super- grid that may acquire large penetration of inexhaustible powers, without compromising power quality, active and reactive power flow, and voltage and facility stability. The super-grid constructed with ultra- high voltage DC (UHVDC) and flexible ac transmission systems (FACTS) together with dedicated ac and dc interconnectors with intelligent systems applications to supply a wise Integrated Super-Grid. DC interconnectors will segment the whole continent's power systems into five large asynchronous segments (regions). Noncontemporary divisions will prevent ac fault propagation between sections while allowing power exchange between different parts of the super-grid, with minimum difficulty for grid code unification or harmonization of regulatory regimes across the mainland as each segment maintains its accord . a sensible Integrated wattage Super-Grid powered by these technologies is critical in supporting sustained economic process and development; established on the keystone of renewable energy and utilizing over 600GW immeasurable potential of Africa's clean and renewable hydroelectric, photovoltaic and alternative energy as a little of a extensive energy comingle of traditional and complementary energy resources.

Reliability Evaluation of Bulk Power Systems Incorporating UPFC

Unified power flow controller (UPFC) is one of the most advanced flexible AC transmission system (FACTS) devices that can simultaneously and independently control both the real and reactive power flow in a transmission line. The utilization of UPFC can result in significant reliability benefits in modern power systems. This paper proposes a novel reliability network model for a UPFC, which incorporates the logical structure and the distinct operating modes of a UPFC. Two-state or three-state models have been used for UPFC by previous researchers. The proposed model divides the UPFC operating modes into four states, namely the UPFC up state, STATCOM state, SSSC state and UPFC down state, in order to improve the accuracy of the model by recognizing the practical operating states of a UPFC. The new model also incorporates an AC flow-based optimal load shedding approach to assess the impact of bus voltages and reactive power flow on UPFC in order to decide appropriate load curtailment in the reliability evaluation process. The performance of the proposed model is verified using a test system, and compared with different reliability models of UPFC. Various operating schemes, such as different placement locations of UPFC, and different capacities of UPFC are used to illustrate the advantages of the developed models, and to examine the impacts of UPFC on the system reliability.

A Practical GERI-Based Method for Identifying Multiple Erroneous Parameters and Measurements Simultaneously

Even with modern smart metering systems, erroneous measurements of the real and reactive power in the power system are unavoidable. Multiple erroneous parameters and measurements may occur simultaneously in the state estimation of a bulk power system. This paper proposes a gross error reduction index (GERI)-based method as an additional module for existing state estimators in order to identify multiple erroneous parameters and measurements simultaneously. The measurements are acquired from a supervisory control and data acquisition system and mainly include voltage amplitudes, branch current amplitudes, active power flow, and reactive power flow. This method uses a structure consisting of nested two loops. First, gross errors and the GERI indexes are calculated in the inner loop. Second, the GERI indexes are compared and the maximum GERI in each inner loop is associated with the most suspicious parameter or measurement. Third, when the maximum GERI is less than a given threshold in the outer loop, its corresponding erroneous parameter or measurement is identified. Multiple measurement scans are also adopted in order to increase the redundancy of measurements and the observability of parameters. It should be noted that the proposed algorithm can be directly integrated into the Weighted Least Square estimator. Furthermore, using a faster simplified calculation technique with Givens rotations reduces the required computer memory and increases the computation speed. This method has been demonstrated in the IEEE 14-bus test system and several matpower cases. Due to its outstanding practical performance, it is now used at six provincial power control centers in the Eastern Grid of China.