This study presents the research and application of multiple static synchronous compensators (STATCOMs) in the China Southern Grid (CSG) to enhance the stability of its receiving-end power system. In this research, a practical methodology is developed for the optimal allocation of STATCOMs in a complex power system through both static and dynamic approaches. The allocation scheme for installing multiple STATCOMs in the CSG is determined using the proposed process. ±200 MVAr STATCOMs are developed based on cascaded H-bridge converters connected in the delta structure. A special system-level control strategy for fast voltage recovery applications is introduced in this study, and field test results and application effects are presented. Results of the real-time digital simulation are introduced to verify the application effects in the case where multiple STATCOMs are connected to the grid. Field test results and analysis of the recorded data for the system faults during actual operation also verify the application effects of multiple STATCOMs in the CSG.

Hybrid direct current circuit breakers (DCCBs) have great prospects for the isolation of dc faults in multi-terminal dc grids. Current commutation from the mechanical switch branch to the static DCCB branch is the precondition to interrupt fault currents successfully for the hybrid DCCBs. A current commutation drive circuit (CCDC) is presented in this study, and it has features of low cost, low operating losses and free maintenance. Experiments have been carried out on a unidirectional 44 kV hybrid DCCB prototype with CCDC. The results show the current of 3.4 kA can be commutated by CCDC within 130 μs, and be interrupted successfully within 2 ms. For a bidirectional 80 kV hybrid DCCB cell, the effectiveness of CCDC is validated with simulations carried out in PACAD. Then, an index is defined to represent the current commutation capability of CCDC and a mathematical model for CCDC is established to calculate the index. To reduce the cost of CCDC with certain current commutation capability, an optimisation method based on genetic algorithm is proposed in this study. According to the optimisation results of CCDC suitable for bidirectional 80 kV hybrid DCCB cell, the cost of CCDC has been reduced by optimisation.

Energy storage systems are expected as a near-term solution for renewable energy application in the residential energy hubs. Within this context, this study investigates the feasibility of using storage systems in improving the technical and financial performance of the residential renewable-based energy hub. A new approach has been proposed in this study in which economic dispatch problem has been formulated for an energy hub including both electrical and heat storage system. The proposed approach determines the optimal supply of energy demand and storage system operation to minimise the total energy cost of the hub. The economic benefit of storage system due to energy cost saving and emission reduction has been determined and the investment payback of the storage system have also evaluated in the proposed approach. The proposed approach has been applied to 12 different residential energy hubs and the impact of energy tariff and storage size has been analysed. The obtained simulation results demonstrate the importance of correctly modelling the hub elements in evaluating the storage system benefit in residential energy hub.

This study proposed a novel fault-location algorithm for a series capacitor (SC) compensated transmission lines under power oscillation conditions. Synchronous voltage and current phasors from both terminals of the transmission line are employed to estimate the fault location while considering the distributed parameter line model. An iterative method is proposed to obtain the voltage across the SC under power oscillation conditions. The fault-location algorithm includes three stages. Firstly, the distributed parameters of the transmission line are estimated by the dynamic parameters estimate method. Secondly, the voltage of the SC can be solved by the iterative method based on the phasor measurements and the transmission line parameters. Finally, the fault location can be attained via Newton iteration method. A 300 km/500 kV transmission compensated by SC simulated in PSCAD/EMTDC has been employed to evaluate the performance of the proposed algorithm under various power oscillation situations. The simulations have demonstrated that the proposed method independent of fault types, fault resistance and fault distances under power oscillation conditions. The accuracy of the proposed algorithm is far higher than that of the conventional fault location algorithms in most cases.

Incorrectness of simulation model parameters can lead to erroneous results in power system operation and planning studies. Therefore, model parameters should be verified according to measurements obtained from the actual system. Mismatches between simulation results and corresponding field measurements can be considered as a sign for the necessity of model verification. Inaccurate branch parameters in simulation models can lead to misguided results in protection, operation and planning studies. An efficient algorithm is proposed in this study for detection and correction of erroneous branch parameters. First, suspicious parameters are selected utilising a sensitivity-based probabilistic method. Applying learning automata theory, selection probabilities will be modified according to simulation responses. A novel formulation is proposed for calculating selection probabilities according to simulation responses. Afterwards, selected parameters are modified by utilising an iterative Newton–Raphson scheme. Unlike state estimation-based methods, required sensitivities are calculated numerically. Therefore, the explicit mathematical formulation of measurements dependency on model parameters is unnecessary. The procedure of erroneous parameter detection and correction will be continued until the value of sum of squared errors (SSE), the objective function in optimisation procedure, becomes sufficiently small. Simulation results demonstrate the high efficiency of the proposed method.

The reactive power coordinated optimisation problem for distribution network (DN) with the integration of renewable distributed generation (DG) is investigated in this study. By actively participating in reactive power control together with an under-load tap changer and shunt capacitors, DG can operate more effectively in the DN. Non-dispatchable DG is considered in the coordinated optimisation method. The objective of the proposed reactive power coordinated optimisation method is to minimise active power loss and to decrease the number of switching device operations while maintaining the grid voltage within the allowable range. The optimisation problem is to solve a variable combination including integers and continuous variables, which will formulate a mixed integer non-linear programming (MINLP) problem. The control variable includes operations of traditional reactive power control devices and the reactive power adjustments of DGs. To solve the MINLP problem, a heuristic searching method, an improved harmony search algorithm is proposed with adaptive parameters process. Numerical tests on a standard 10-kV distribution system and a real distribution system demonstrate the applicability of the proposed reactive power coordinated optimisation method.

This study presents an improved voltage shift islanding detection method with the new control mode. The proposed method adopts the modulation index shift scheme based on the pulse-width modulation control principle, which can promote the detection performance in the multi-inverter grid-connected photovoltaic (PV) systems, compared with the conventional voltage positive feedback (VPF) method. The superposition algorithm of the proposed method can make the rapid reduction of voltage magnitude at the point of common coupling during the islanding condition, and minimise the non-detection zone. Through the self-varying positive feedback gain, the synchronisation of voltage shift rates from multiple PV inverters can be effectively improved under the varying active power conditions. According to the characteristic of maximum power point tracking control, the gain will be automatically changed along with the variable PV voltage. The advantage of the proposed method is analysed by the simulation results in comparison with the conventional VPF method. Moreover, the experimental results are provided to verify the effectiveness of the proposed method.

In this study, a new islanding detection technique based on the rate of change of superimposed negative sequence impedance (ROCSNSI) is proposed. Due to the presence of non-linear loads in microgrids, a considerable amount of inter harmonic components exist in power system signals. To compute the fundamental frequency component of voltage and current signals, phasors are calculated using a full-cycle least error square technique. The ROCSNSI is considered for the discrimination of islanding and non-islanding events (NIEs). The performance of the proposed technique is evaluated by simulating IEEE 13 and IEEE 34 bus microgrid systems in real-time digital simulator. Islanding and non-islanding scenarios for perfect power match condition, types of distributed generations (DGs) with various control strategies are simulated and the performance of the proposed approach is found to be accurate. It is found that, the technique identifies the islanding even under low active and reactive power mismatches and hence overcomes the non-detection zone problem. Different NIEs, like load switching, faults, tripping of DG, single-pole tripping and reconnection of the DG are considered and the technique discriminates islanding and NIEs within a full cycle from the inception point.

In this two-article set, a new multi-level framework is presented for coordination of generation and transmission expansion planning (G&TEP) in liberalised electricity markets. Part I is mainly dedicated to mathematical modelling of the G&TEP problem. The main aims of the proposed framework are not only to develop a holistic model for the G&TEP problem, but also to evaluate impacts of expansion plans on market participants’ strategic behaviours. To do so, the proposed methodology is decomposed into a planning master problem and an operating slave problem. In the slave problem, the first level indicates market participants’ strategic interactions and the second level represents a pool-based electricity market. In the master problem, an independent system operator model is described to coordinate decentralised generation expansion planning in the third level with centralised transmission expansion planning in the fourth level. In addition, the offered framework uses a well-founded information-gap decision theory to minimise risks of planning arising from severe uncertainties. The newly developed framework is formulated as a non-convex mixed-integer non-linear optimisation problem. Hence, a novel two-stage multi-dimensional melody search algorithm is widely employed to determine the best solution. The profitableness of the developed framework is illustrated in part II of this two-article set.

This paper presents a new hybrid method for solving the proposed multi-level optimisation problem, as described in Part I. The hybrid method employs a novel two-stage multi-dimensional melody search algorithm (MSA) with an innovative alternative improvisation procedure (AIP). This hybrid method handles the different levels of the proposed multi-level framework. The two-stage multi-dimensional MSA is a recently developed optimisation algorithm, which is derived from the harmony search algorithm (HSA). Unlike the HSA, the MSA uses different player memories and a group improvisation procedure for finding the best substitution of pitches within a melody. These two features can enhance the performance of the MSA in comparison with the HSA. In addition, to improve the efficiency of the proposed MSA, an innovative improvisation scheme based on the AIP is used for generating new melodies. The proposed methodology has been applied on the 46-bus south Brazilian electric power grid and the IEEE 118-bus test system under two different scenarios in order to demonstrate the feasibility and capabilities of the newly developed framework. The obtained results from case studies validate sufficiency and profitableness of the offered multi-level framework.

Microgrids have been recognised as essential components of the smart grid. However, recent advances on communication, control, and other intelligent techniques have also significantly increased the design complexity of the microgrids. This calls for attention for the microgrid community to be aware of the latest design challenges and develop visionary approaches to re-evaluate the legacy power system design concepts and analysis tools that are currently utilised for microgrid studies. This study proposes a novel model-based analysis and design framework tailored specifically for microgrids based on the concept of model-integrated computing. The proposed framework aims to provide a flexible and extensible integrated environment to facilitate rapid modelling and simulation of microgrids as well as the implementation of other control, analysis, and microgrid design applications. In this study, the authors focus on demonstrating and examining how the adoption of the proposed framework can effectively reduce the duration and costs of the design process, enhance the experience of the end-users, and improve the overall quality and efficiency of the microgrid study activities. Case studies under various microgrid operating scenarios are presented to validate the effectiveness of the proposed framework.

In this study, a three-phase harmonic power flow method using graph theory, injection current and sparse matrix techniques for unbalanced radial distribution systems is proposed. In the bus frame of reference, a direct iterative method is adopted. The proposed method can be used for both fundamental and harmonic power flow studies. Four three-phase IEEE test feeders are used to prove the accuracy and efficiency of the proposed method. The test results show that the proposed method is robust and reliable for passive power filter design, especially for full-scale distribution systems.

The accuracy of harmonic contribution assessment is severely affected by the fluctuation of utility harmonic. This study proposes an adaptive method for harmonic contribution assessment of the distribution system with multiple harmonic loads based on hierarchical clustering and regression analysis. First, the utility harmonic impedance is determined by the dominant fluctuation filtering. Then, the utility harmonic voltage data are automatically clustered into different segments based on the hierarchical K-means clustering, which does not require a given clustering number of harmonic data. Subsequently, the harmonic contribution of each data segment is calculated with the Bayesian partial least squares regression, hence providing an adaptive estimation of the optimal principal components. Finally, the total harmonic contribution of the concerned period is obtained by weighted summation according to the length of each harmonic data segment. Simulations are carried out on the IEEE 13-bus and 69-bus systems. The results confirm that the approach can adapt to the fluctuation of utility harmonic and produce assessment outcomes more accurately compared with some other methods.

Aeronautical ground lighting (AGL) systems are single-phase series circuits where constant current regulators supply transformers and luminaires. These systems provide visual reference to aircraft during airport operations. There is a lack of AGL system models and measurements in the literature to study AGL system behaviour and predict their response to electrical events and future technological changes. The study contributes to AGL system modelling with an equivalent circuit useful to study AGL system concerns by Matlab/Simulink simulations. It also presents field measurements taken at Reus airport (Catalonia, Spain) for the validation of the proposed model and understanding of AGL system behaviour in the event of luminaire failure.

The aim of this study is to discuss the challenges that will be faced by the designers of measuring instruments in future, in the wake of the proliferation of microgrids. In this context, the fluctuations in the angular frequency of the fundamental component of the voltage and the resulting changes in the duration of the measurement windows are considered. The main objective of this study is to consider this variation in the angular frequency from the point of view of the IEC Standard 61000-4-7, using real signals. Numerous results from the experiments conducted in 11 electric power networks, chiefly marine microgrids, are presented, and discussed. A comparative analysis of the behaviour of two measuring instruments is also provided. Both the instruments are based on different signal processing principles. One of them utilises the signal processing method recommended in the IEC 61000-4-7 standard, whereas, the other is based on the application of the chirp z-transform principle.

This study investigates an optimal sizing strategy for substation-scale energy storage station (ESS) that is installed at substations of transmission grids to provide services of both wind power fluctuation smoothing and power supply for peak load simultaneously. The proposed strategy first involves an optimal charging and discharging scheme enabling ESS to offer both services, considering particularly seasonal output variations of surrounding wind farms connected at the substation. Consequently, an optimisation model of ESS capacity is formulated to achieve trade-off between various costs and benefits involved in offering services by ESS. Case studies based on historical wind power data are conducted to validate the performance of the proposed method, and the simulation results demonstrate that this method can significantly reduce the ESS size and achieve promising benefits from power supply for peak load.

Transient control performance of power systems is extremely important, especially during the recovery stage from a system temporary fault. A large power angle error or generator relative speed could result in unrecoverable failure or system damage. In this study, a class of novel excitation controllers is proposed for power systems to place user-defined time-varying constraints on the system errors. First, the direct feedback linearisation technique is employed to transfer the original non-linear system to a linear one. An error transformation method is introduced to generate a new non-linear system, whose stability ensures that the time-varying constraints on the original system are satisfied. Thus, a backstepping-based excitation control methodology is designed for ideal case by assuming all system parameters are known. Thereafter, the uncertainties of system dynamics are also considered and compensated by designing an adaptive excitation controller. By utilising the standard Lyapunov synthesis, the closed-loop system is proved to be asymptotically stable, and all the other signals are bounded for the two control schemes. Furthermore, the system transient performance can be shaped arbitrarily with predefined trajectories, in the sense that the system errors never cross certain boundaries during transient phase. Eventually, extensive simulation studies demonstrate the feasibility of the theoretical results.

Wide-area power system stabiliser (WAPSS) has been proved to be an effective method to damp inter-area low-frequency oscillations by using synchronised-phasor measurements. However, negative interactions among the WAPSSs may happen when they are designed separately. The conventional model-based coordination design methods are difficult to get good damping performance because model identification of the high-order, non-linear and time-varying power system is difficult. In this study, an improved model-free adaptive control (MFAC) algorithm is proposed for WAPSS coordination design. With the consideration of the interactions among the controllers and system noises, a novel decoupled multiple-input–multiple-output power system description for WAPSS coordination design are given. The MFAC control law and adaption law for each subsystem are improved to satisfy the controller coordination design requirements. The closed-loop system stability and parameter settings of the improved MFAC algorithm are also analysed from a global perspective. Compared with model-based methods, the proposed MFAC algorithm can ensure the controllers cooperate with each other and perform well under various operating conditions without tedious system modelling. The effectiveness of the proposed controllers is tested on an interconnected large-scale power system in China. An MFAC-WAPSS control system for field application is also presented in this study to validate its practicality.

Large scale wind power generation complicated with restrictions on the tie line plans may lead to significant wind power curtailment and deep cycling of coal units during the valley load periods. This study proposes a dispatch strategy for interconnected wind-coal intensive power systems (WCISs). Wind power curtailment and cycling of coal units are included in the economic dispatch analysis of regional systems. Based on the day-ahead dispatch results, a tie line power plan adjustment strategy is implemented in the event of wind power curtailment or deep cycling occurring in the economic dispatch model, with the objective of reducing such effects. The dispatch strategy is designed based on the distinctive operation characteristics of interconnected WCISs, and dispatch results for regional systems in China show that the proposed strategy is feasible and can improve the overall system operation performance.

In order to achieve a better economic dispatch decision of the electricity generation while guaranteeing system security, the optimal transmission switching (OTS) has been proposed with the well-known N-k contingency security criterion. However, the challenge for treating the OTS problem considering N-k contingencies lie in that it may lead to a conservative result, since the optimal solution should simultaneously satisfy all the sets of N-k constraints. To address this problem, the corrective control with respect to different contingencies is utilised during the period when the transmission topology remains unchanged, which can be formulated as a two-stage problem. Consequently, a two-stage robust optimisation is employed to optimise the objective value under the worst contingency, so as to hedge against the contingency uncertainties. Comparison of the traditional N-1 OTS and the proposed robust N-1 OTS models on IEEE 30-bus test system shows that the robust OTS model has less conservatism than the traditional OTS model with the help of corrective actions. Moreover, it illustrates that the proposed method can be fairly applicable to cases with even N-k contingencies, which can facilitate the complexity of contingency analysis.

TCSC is one of the most appropriate devices to improve the transient stability of power systems. Since in today's competitive environment, investments in power systems need to be cost-effective, in this study, a procedure is presented to determine whether using TCSC for transient stability improvement is cost-effective or not. To this purpose, the transient instability risk is estimated both with and without TCSC. Afterwards, a comparison is made between the amount of improvement made in transient instability risk and the investment cost of TCSC. In the proposed procedure, the probabilities of transient instability and its cost are used to estimate the transient instability risk. To calculate the transient instability probability, a conditional method is used. This method is applied on the IEEE 9-bus as well as New England test systems. The simulation results demonstrate that the proposed procedure is capable of determining the cost–benefit size and number of TCSC units. Furthermore, results indicate that in some cases, installing TCSC to only improve transient stability is devoid of monetary value.

The distance protection of multi-terminal transmission lines need to be redesigned due to possible changes in the backup protection emanating from probable infeed currents produced from tapped transmission lines. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this study, an algorithm is presented based on synchrophasors. In this method, voltage and current signals of buses will be sent to system protection centre (SPC) and in SPC an algorithm based on active power calculation in buses is provided that is able to eliminate the effects of both mentioned factors. In this method, measurement or relay in tapped transmission line location are not required. The study includes analytical analysis and modelling and in modelling results a variety of faults with different fault resistances is considered. Two power systems including teed-feeder system and IEEE 14-bus power system are considered. The results show that in both power systems, and different types of faults, backup distance protection is improved. Simulations are conducted by Electro-Magnetic Transient Program works.

Power system security concerns due to significant wind generation could be twofold: first, the frequency response and second, the short-circuit performance. Continuous development of wind energy may cause economic replacement and retirement of existing synchronous generators. Modern wind turbine generators do not inherently offer inertia and governor response after a disturbance, which may result in declining frequency response behaviour. Besides, they have limited fault current contribution, which may cause unacceptable short-circuit ratio at the grid connection point of those wind power plants. Traditionally, frequency response and short-circuit performance are individually improved. However, both of them are concurrently affected by high wind penetration. Hence, a common approach to simultaneously enhance both indices is essential. Therefore, this study introduces an idea of operating some of the retired synchronous generators in the synchronous condenser mode, which is termed as ‘post-retirement scheme (PRS)’. Such a second use of the retired synchronous generators can jointly upgrade frequency response and short-circuit strength during high wind generation. This study also proposes a methodology to evaluate when and how much PRS should be deployed for ensuring an adequate security performance in a wind dominated power system.

Research of switching operation transient electromagnetic field in substations is fundamental to the protection of mine monitoring systems against electromagnetic interference. Three models, which are the equivalent circuit of switching on/off inductive load, transient radiation of short dipole, and transmission line of long cable, are built for numerical analysis. The results indicate that switching operation does not produce transient pulse when the breaking angle is close to 90°. Electric fields are the primary form of transient pulse radiation, and the effect of the magnetic field on the environment can be ignored. Long cables are naturally resistant to differential mode transient pulse propagation, but the effect of common mode transient pulse cannot be ignored. Energy distribution of transient pulse in different frequency ranges is calculated by using theParserval equation. Furthermore, the measurement frequencies and the instruments used in the coal mine are determined, and on-site data is then obtained. Measurement results show that switching operation may produce a series of transient pulses, causing the electric field to grow larger than before. Specifically, conducted emissions have large impacts on the monitoring circuitry of the mine equipment, causing the mine monitoring system to frequently record erroneous data and omit information.

This study presents a mathematical model to determine the optimal site and the size of plug-in hybrid electric vehicles charging stations (CSs) in the distribution networks. The presented optimal planning is done along with considering the rate of customers’ participation in demand response programs (DRPs) at the presence of some uncertainties associated with the load values and electricity market price. In order to model the load, time-of-use DRP is used. The proposed model involves distribution system manager (DSM) benefit maximising derived from the appropriate use of CS for charging and discharging vehicle batteries, reliability improvement and supplying network's load demand at peak times as the objective function, technical limitation as constraint and the siting and sizing of electric vehicles CS as optimisation variables. The genetic algorithm method with embedded Monte Carlo simulation is used in order to solve the optimisation problem and is applied to the 9-bus and 33-bus networks. The test results indicate that not only does the appropriate planning have an economic benefit for DSM, but also voltage profile and power supply reliability for customers can be improved and active power losses can also be reduced.

This study considers a novel application of electric vehicles (EVs) to quickly help reheated thermal turbine units to provide the stability fluctuated by load demands. A mathematical model of a power system with EVs is first derived. This model contains the dynamic interactions of EVs and multiple network-induced time delays. Then, a dynamic output feedback H _∞ controller for load frequency control of power systems with multiple time delays in the control input is proposed. To address the multiple time delays issue, a refined Jensen-based inequality, which encompasses the Jensen inequality, is used to derive less conservative synthesis conditions in terms of tractable linear matrix inequalities. A procedure is given to parameterise an output feedback controller to guarantee stability and H _∞ performance of the closed-loop system. Extensive simulations are conducted to validate the proposed control method.

Based on an adaptive backstepping approach, this study proposes a new coordinated control design where the coordination is done between the excitation controller of synchronous generators and steam-valve controller of turbine-governor systems in a multimachine power system by considering the critical parameters of both systems as unknown. This new coordinated control scheme can ensure the stability of multimachine power systems through the formulation of control Lyapunov functions (CLFs) and derive the adaptation laws to estimate the unknown parameters in the design process to prove the convergence of power systems using CLFs. The performances of the proposed control scheme are evaluated on a two-area four-machine 11-bus power system under different operating conditions such as three-phase short-circuit faults along with changes in loads. Simulation results are then compared with those of a similar controller where there is no coordination between the excitation and steam-valve controllers as well as with a coordinated sliding-mode controller. The results clearly show the effectiveness and superiority of the proposed control scheme.

Electric arc furnace (EAF) is one of the largest loads in the power systems. Unfortunately, it is highly non-linear and time varying which causes power quality problems such as harmonics and flicker. Therefore, having an accurate EAF model is necessary. Cassie model is one of the most utilised EAF models in the related fields. However, actual data from electrical system of Mobarakeh Steel Company in Isfahan/Iran show that this model is unable to take into account some important quantities such as the active power and harmonics. Hence, as the first step in this study, different Cassie–Mayr model variants (include the Cassie model) are investigated and the best variant is attained. A novel procedure using large number of recorded actual data is utilised for the models assessment. In the second step, two generalised types of the original Cassie–Mayr model are proposed. Both the generalised types are more accurate than the best-selected Cassie–Mayr variant. All the proposed models have time-varying parameters. Their time-varying nature is studied and by analysing the time series, the proper auto regressive moving average models are attained for every parameter.

The transient analysis of multi-conductor transmission lines should consider the frequency-dependent characteristics due to the skin effect. Fully considering the inherent fractional order characteristics of the frequency-dependent effect, a general wide-band modelling method is proposed. The fractional order vector fitting method is adopted to approximate the frequency-dependent parameters and the corresponding fractional differential equations can be obtained by the inverse Laplace transformation. The backward difference is a practical method to solve the fractional differential equations; however, a linear convolution must be calculated, which will lead to a heavy computation complexity. To address this issue, a new recursive convolution method for the fractional differential equations is proposed and an efficient solution is achieved. Furthermore, considering the indispensability of the passivity verification of a system for the transient simulation, the passivity verification by extending the Hamiltonian matrix for the fractional order systems is studied and a practical criterion is proposed. Three examples are considered to validate the proposed method: (i) a single underground cable, (ii) three-phase underground cable, and (iii) an experimental transformer under very fast transient voltage. The simulation results are compared with the results obtained by power systems computer-aided design or measurements and good agreements are achieved.

Microgrid technologies have been studied for various goals including enabling renewable energy penetration. Traditional droop control is important for microgrids to achieve plug and play characteristics, but it may not be suitable for storage units with time-varying capacity levels due to the constant slope in droop control. In order to address the potential challenges of dynamic adjustment in linear droop control applied to microgrid inverters powered by limited energy sources, this study presents an S-shaped droop control. This control method tends to make the inverter to output more power when the frequency is close to the nominal operating point, while outputting less power when the frequency is away from the nominal operating point such that the other generators will pick up more load. Also, power quality problems can be addressed with the improvement provided by the characteristic similar to the secondary frequency control which brings the frequency closer to the rated frequency. The proposed mathematical model is built by curve fitting and theoretic analysis, and is simulated in Matlab/Simulink. The results verified the ability to improve power quality and adjust the load share among inverters as opposed to conventional droop control.