An Improved Harmonic Energy Measurement Algorithm Based on Instantaneous Reactive Power Theory

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal, balanced or unbalanced, three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

A generalized theory of instantaneous reactive power for three-phase power systems is proposed in this paper. This theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal, balanced or unbalanced, three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A three-phase harmonic distorted power system with zero-sequence components is then used as an example to show reactive power measurement and compensation using the proposed theory.

The paper presents the structure of an active parallel filter for reducing harmonic pollution and reactive power. The active power filter control is based on instantaneous reactive power theory. The authors present the modelling of parallel active filter based on this theory and the simulation results in MATLAB-SIMULINK. The method is based on instantaneous reactive power (TPRI_P).

In this paper the response of a microgrid to the interfaced harmonic distorted load is analyzed. A new control algorithm to mitigate harmonic distortion is considered for distributed generators (DGs) and the effect of this control scheme is shown in the currents of DGs and other loads. The proposed control algorithm is compared with the conventional control strategy for harmonic distorted loads that is sinusoidal source current strategy based on the instantaneous reactive power (IRP) theory. PSCAD simulation results for IRP theory control show high total harmonic distortion (THD) and 3rd harmonic percent. In comparison inner voltage and current controllers of the proposed control scheme with their disturbance rejection capability, mitigate THD and 3rd harmonic percent. For this control system MATLAB simulation results are shown. By demonstrating the traditional sinusoidal source current control strategy based on IRP theory, it is concluded that ignoring the distortion power (D) in compensating process and also sub-harmonics of P
. crossing from the controller interior high pass filter cause the presence of some harmonic components and high THD. Keywords: distributed generation, instantaneous reactive power theory, harmonic distortion, microgrid.

This paper deals with the presentation of different terms of the powers presented in the Instantaneous Reactive Power Theory (IRPT) in the general case of a generic power system voltage. This presentation is based on the use of the symmetric components in the E. Clarke stationary frame, where the instantaneous real active power, the instantaneous imaginary reactive power and the instantaneous zero sequence power are divided into their DC components and AC components function of the symmetric components. The contributions of these terms in the transfer of the energy from the power supply to the load in four wire system are explained, hence, a good choice of the power to be compensated using shunt active power filter can be obtained. Finally, simulation results are presented under unbalanced and distorted generic power system voltages, where different terms of the instantaneous reactive power theory are clarified and presented based on symmetrical components.

Purpose. Based on the instantaneous electrical power of a three-phase asymmetric system of sinusoidal periodic current, to determine positive, negative, zero-sequences active and reactive power, as well as invariance power factor. Methodology. In the unbalance case in three-phase electrical system, the electrical energy quality is evaluated by means on voltage and current positive, negative, zero-sequences. At the same time, similar components of active and reactive power have not received practical distribution. But it is precisely in terms of power that electricity is accounted for. The instantaneous power orthogonal components in the time domain are determined using the symmetrical components of voltage and current. Active, reactive powers of positive, negative and zero-sequences are allocated. The result obtained has the property of representativeness, which most of the known results lack. Findings. The three-phase system’s instantaneous power components are analytically determined, including the amplitudes of the oscillating power components. The need to take into account the oscillating instantaneous power components has been proven by means of a graphical interpretation of a special case of the three-phase system mode. As an integral indicator that takes into account the oscillating components of the three-phase system instantaneous power, its root-mean-square value over the repetition period is used. Originality. By calculating the transformer efficiency of the studied model according to the active power positive sequence and the same indicator according to the active power as a whole, it was established, that the component sequence separation affects the results of calculating the generalized indicators, including the power transmission system objects. This can lead to erroneous judgments about the efficiency of the specified facilities functioning. Practical value. The invariance power factor was used to characterize the electrical energy quality level of a three-phase sinusoidal current system in an unbalanced mode.

Distributed power generation has got its importance with the day to day increase of power generation from renewable energy sources and from domestic customers with small generation units connected to the grid.Distributed power generation systems mostly use Power electronic converters for the interface with power grid.Here in this paper a single-phase inverter for DG systems requiring power quality features, such as harmonic and reactive power compensation for grid-connected operation are discussed.The idea is to integrate the DG unit functions with shunt active power filter capabilities.With this approach, the inverter controls the active power flow from the renewable energy source to the grid and also performs the nonlinear load current harmonic compensation by keeping the grid current almost sinusoidal.The control scheme employs a current reference generator based on sinusoidal signal integrator and instantaneous reactive power (IRP) theory together with a dedicated repetitive current controller.Simulation results obtained with PI and fuzzy controllers demonstrate the feasibility of the proposed solution.

The increase and decrease of non-linear load and impact load of power grid lead to lower and lower power quality, which has become a hot issue in reactive power compensation and harmonic suppression technology research. As one of the AC output equipments, the static synchronous compensator has strong compensation performance and can provide technical support for no power compensation. Therefore, based on the theory of instantaneous reactive power, the current detection method and related control technology of the static synchronous compensator are proposed, and finally the experimental simulation is carried out. The simulation results show that the improved detection algorithm can detect the reactive current of the system efficiently and accurately. Using STATCOM current detection method and control technology, it can adjust reactive power in time, compensate for actual power demand, further suppress system voltage fluctuations and improve system performance.

With the continuous development of water-saving irrigation, agricultural product's deep process, greenhouse control in the agriculture, more and more variable frequency equipments, rectifier devices and other power electronic equipments have been used. But owing to the use of these equipments, harmonic pollution problem in power grid is more serious. Active filter is an effective method to the pollution now. Based on the instantaneous reactive power theory, a new way to detect both instantaneous reactive current and high-order harmonic current is proposed. By this way the high-order harmonic and fundamental reactive power are synthetically compensated. Our studying group has developed a synthetical active filter system, which uses the large power transistor as the main circuit, TMS320F240 processor as controller, and connects possible LC power filter and active power filter in series. The experiment results show that the system can effectively filter 5,7,11 degree-order current harmonics and prove that the way is correct and feasible.

This paper deals with the problem of the early stator (the short-circuits) and rotor (broken bars) faults detection of the induction motors supplied from the frequency converter. The method basing on the FFT algorithm is used for the spectral analysis of the instantaneous active power, the instantaneous reactive power and the estimated electromagnetic torque. These signals are on-line calculated, basing on the measured currents and voltages of the motor. Computations of the instantaneous active and reactive power use the theory of the electric power for non-sinusoidal power systems. In this paper results of laboratory investigations for low power motor with modeled stator short-circuit and broken rotor bars are demonstrated. Tests were realized for different supply frequencies, what enabled the evaluating of the usefulness of the proposed analysis in the diagnostics of the stator and rotor faults in the converter-fed induction motor drives.

In this paper, grid connected DSTATCOM with three phase three wire has been proposed for harmonics elimination, reactive power compensation and active power injection into the grid. An improved instantaneous reactive power theory based on the least mean square is computed. The least mean square (LMS) algorithm is combined with instantaneous reactive power theory (IRPT) to improve its dynamics performance and eliminates the use of low pass filter requirement for computation of reference current. The harmonics component of the active power is estimated from LMS algorithm generated load harmonics currents. The performance characteristic of DSTATCOM is estimated with control scheme using computer simulation. The technique is based on the instantaneous transformation of instantaneous signals and taking advantage of the subsequent calculation of power from supply side to the loads. The neural network based method to estimate the harmonic online, DSTATCOM can compensate the harmonics. The computer simulation is carried out with MATLAB Simulink power system block sets.

In this paper, a photovoltaic (P/V) system, with maximum power point tracking (MPPT), connected to a three phase grid is presented. The connection of photovoltaic system on the grid takes place in one stage using voltage source inverter (VSI). For a better utilization of the photovoltaic system, the control strategy applied is based on p-q theory.According to this strategy during sunlight the system sends active power to the grid and at the same time compensates the reactive power of the load. In case there is no sunlight (during the night for instance), the inverter only compensates the reactive power of the load. The advantage of this strategy is the operation of the photovoltaic system the whole day. In this paper the p-q theory is proposed, which does not demand the use of PLL and introduces simple algebraic calculations.

Statcom behaviour under unbalanced power system condition is examined. State observer based control strategy is used to estimate the voltages at the point of common coupling from the measured injected current so that hardware requirement gets reduced and hence cost gets reduced. Feedback linearization control strategy has been used to linearize the system and to decouple the positive and negative sequence component of ac side current to evade the possibility of over current to statcom under unbalanced power system condition. The instantaneous active and reactive power theory is used for calculating the positive sequence component of current in α-β reference frame with the help of desired active and reactive power reference. The sinusoidal pulse width modulation control technique has been implemented for voltage source inverter to produce the gating pulses. Two level statcom is used for realization the above mentioned control scheme.

This paper includes assay and correlation of three phase shunt active to extricate its reference currents with distinct control strategies to evaluate their dynamic performance under different load conditions for both Shunt Active Power Filter (SAPF) and Hybrid Shunt Active Power Filter (HSAPF). The instantaneous active and reactive power (p-q) theory and synchronous reference frame theory (SRF) are compared. Extensive simulations are carried out for p-q and d-q theory’s for both shunt APF and hybrid shunt APF with PI controller. The compensation capability of Hybrid shunt APF is greater than SAPF for harmonics, reactive power compensation and dynamic performances capability. Performances comparison is analyzed using Matlab/Simulink. Simulation outcome is given to compare and validate the control techniques for SAPF and HSAPF during load changing condition.