Non-active Power Research Articles

Geometric Algebra in Nonsinusoidal Power Systems: A Case of Study for Passive Compensation

New-generation power networks, such as microgrids, are being affected by the proliferationof nonlinear electronic systems, resulting in harmonic disturbances both in voltage and current thataffect the symmetry of the system. This paper presents a method based on the application of geometricalgebra (GA) to the resolution of power flow in nonsinusoidal single-phase electrical systems for thecorrect determination of its components to achieve passive compensation of true quadrature current.It is demonstrated that traditional techniques based on the concepts of Budeanu, Fryze or IEEE1459fail to determine the interaction between voltage and current and therefore, are not suitable for beingused as a basis for the compensation of nonactive power components. An example is included thatdemonstrates the superiority of GA method and is compared to previous work where GA approachesand traditional methods have also been used.

Analysis of non-active power in non-sinusoidal circuits using geometric algebra

A new approach for the definition of non-active power in electrical systems is presented in this paper. Through the use of geometric algebra, it is possible to define a new term called geometric non-active power, which is applicable to both sinusoidal and non-sinusoidal systems, and to both linear and nonlinear loads. The classic definitions of distortion and reactive power are compared and discussed in our proposal. We verify how geometric non-active power can appear in both purely resistive and purely reactive systems. The superiority of geometric algebra is revealed through several examples of electrical circuits previously analysed in specialised literature. Furthermore, a new geometrical current decomposition is proposed, for the first time, to provide a greater physical sense to existing geometric power. The results obtained confirm that classic concepts based on apparent power S are based on a lack of physical meaning, which is why geometric algebra theory should be adopted instead.

Definition of distortion power in AC network and analysis of its reasons

This paper studies the conditions under which such non-active power components as reactive power and distortion power appear in the alternating current power network. By simulating with MatLab Simulink, the validity of formulas obtained by analytical way was tested. The formulas define the components of non-active power based on one of the most well-known theories. The results obtained will be useful for mode optimization in the alternating current networks and for developing effective non-active power compensating technologies.

Analysis of power flow under non-sinusoidal conditions in the presence of harmonics and interharmonics using geometric algebra

The calculation of power flow in power systems with the presence of harmonics has been properly studied in the scientific literature. However, power flow calculation considering interharmonic components is still an open question. Traditional methods based on the IEEE1459 standard have proven to be valid and accurate only for linear and sinusoidal systems, but have been criticized for non-linear and non-sinusoidal systems because they are not able to explain correctly the current and voltage interactions beyond the active power. This paper proposes the use of a novel mathematical framework called geometric algebra (GA) to study the power flow considering the interaction of current and voltage harmonics and interharmonics. The use of GA enables the precise determination of the direction and magnitude of the total and single active power flow for each component, as well as other power elements related to the non-active power due to cross interaction. Moreover, this paper makes a novel contribution to the definition of interharmonics in geometric algebra space that has not been done before. To test the validity of the method, both linear and non-linear circuits are proposed and solved by applying voltages and currents with harmonic and interharmonic components. The results obtained show that power flow can be analyzed under the prism of the principle of energy conservation (PoCoE) in a way that allows a better understanding of the power spectrum due to the interaction of harmonics and interharmonics of voltage and current.

Multifunctional Hybrid Structure of SVC and Capacitive Grid-Connected Inverter (SVC//CGCI) for Active Power Injection and Nonactive Power Compensation

In this paper, the structure, coordinate control method, and parameter design of a hybrid system are proposed for active power injection and nonactive power (reactive, harmonic, and unbalance power) compensation. The proposed hybrid system consists of a static var compensator (SVC) in parallel with a capacitive-coupling grid-connected inverter (CGCI) (SVC//CGCI). In SVC//CGCI, the SVC part is used to dynamic compensate the reactive power and unbalance power, while the low rating CGCI part is used to inject active power, provide harmonic power and a fixed amount of capacitive reactive power. Compared with conventional inductive-coupling grid-connected inverter (IGCI), the CGCI can provide active, reactive and harmonic power with low rating of active inverter part. The cost of the SVC part is much lower than that of active inverter part, thus the reduction of inverter rating can lead to a decrease in the total cost of the SVC//CGCI. Therefore, the SVC//CGCI can be a cost effective solution for active power injection and nonactive power compensation. Finally, simulation and experimental results are provided to show the advantages and validity of the proposed SVC//CGCI in compared with the conventional IGCI and SVC//IGCI.

Evaluation of Power Processing in Series-Connected Partial-Power Converters

This paper proposes an analytical methodology to evaluate the power processed by dc–dc converters operating as series voltage regulators, which provide an alternative to increase efficiency in photovoltaic systems. Via the analysis of both active and nonactive power processing, the proposed methodology allows to clearly distinguish among circuit topologies as truly partial-power processing (PPP) or just partial active power processing topologies. When an isolated dc–dc topology is connected in series as a voltage regulator, the overall processed power can be reduced, which reduces power losses and improves efficiency. Conversely, this paper also demonstrates that some series-regulator topologies may not actually reduce the proportion of nonactive processed power. To demonstrate the applications of the proposed methodology and to emphasize its significance, two well-known series-connected voltage regulators (flyback and full-bridge phase shift) and a full-power regulator (boost) were evaluated. The results indicate that the full-bridge series regulator can perform a true PPP, whereas the flyback series-regulator processes the same amount of power as that processed by conventional nonisolated boost converters and cannot be considered a partial-power topology. This study finding contradicts assertions in the literature that this topology achieves high-efficiency dc–dc conversion through PPP. To confirm the theoretical analysis, experimental results from three 750-W prototypes are presented alongside its simulations.

Implications of the Large-Scale Deployment of Non-linear Loads

Compared to yesteryear, non-linear loads now proliferate in homes, offices and the industrial environment. Non-linear loads now form a major component of the total loading in the typical electrical network. The Compact Fluorescent Lamp is but one example of a non-linear load that inherently produces and injects distorted currents into the electrical power network, which could create adverse consequences if appropriate and adequate harmonic mitigation techniques are not employed. CFLs are now a major component of the luminaires market around the world because consideration is being given worldwide to the phasing out of incandescent lamps. However, there are legitimate concerns over the quality of some CFLs. This paper investigates and compares the quality of some major brands of CFLs, in terms of parameters such as harmonic content, power factor, fundamental power factor, nonactive power, and apparent power. The wider implication of these results is ascertained by investigating the effects large scale installation of CFLs would have on a generalized electrical network. This work shows that CFLs with high harmonic currents increase the requirements of the source and other network components, as well as place a significant strain on them, since they draw a higher current and also consume a higher apparent power and nonactive power than is necessary for power delivery. Also, it is found that voltage harmonic limits can approach or exceed the IEEE limit of 5% as the number of CFLs deployed is increased. This situation is more pronounced if CFLs with higher current harmonic content are installed.

Series-Connected Partial-Power Converters Applied to PV Systems: A Design Approach Based on Step-Up/Down Voltage Regulation Range

This paper proposes a novel approach to reduce the power processed by series-connected partial-power converters (S-PPC) applied to string/multistring level maximum power point tracking photovoltaic systems. A design procedure based on the definition of the voltage regulation range is presented. It introduces an additional degree of freedom that allows a proper design of the converter in order to reduce not only the active power but also the nonactive power, reducing losses and increasing power density. By means of the proposed approach, it is also demonstrated that by replacing the conventional step-up partial-power converter by a step-up/down partial-power converter, the active and nonactive power can be further reduced, allowing to better explore the benefits of the partial-power concept. In order to validate the proposed approach, two 750-W prototypes of full-bridge S-PPC and full-bridge/push–pull S-PPC were implemented and experimentally evaluated. The step-up/down prototype presented a reduction of 46.9% in nonactive power and 23.4% of its volume, resulting in a higher efficiency and power density in comparison to the voltage step-up prototype counterpart.

Dynamic Voltage Conditioner: A New Concept for Smart Low-Voltage Distribution Systems

Power Quality (PQ) improvement in distribution level is an increasing concern in modern electrical power systems. One of the main problems in low voltage (LV) networks is related to load voltage stabilization close to the nominal value. Usually this problem is solved by smart distribution transformers, hybrid transformers and solid-state transformers, but also dynamic voltage conditioners (DVC) can be an innovative and a cost effective solution. The paper introduces a new control method of a single-phase DVC system able to compensate these long duration voltage drifts. For these events, it is mandatory to avoid active power exchanges so, the controller is designed to work with nonactive power only. Operation limits for quadrature voltage injection control is formulated and reference voltage update procedure is proposed to guarantee its continuous operating. DVC performance for main voltage and load variation is examined. Proposed solution is validated with simulation study and experimental laboratory tests. Some simulation and experimental results are illustrated to show the prototype device's performance.

Dynamic Response Improvements of Parallel-Connected Bidirectional DC–DC Converters for Electrical Drive Powered by Low-Voltage Battery Employing Optimized Feedforward Control

Parallel-connected modular current-fed bidirectional dc–dc converters are used for the AC motor drive system powered by batteries with low voltage and wide voltage range. The input current ripple can be reduced significantly by employing interleaving technology not only for individual module but also for all the modules. A current sharing control strategy is applied for the constituent modules. Double pulse width modulation plus double phase shifted control with equal duty cycles for one module can minimize the circulation loss and avoid nonactive power issue. Factors affecting dynamic performance are investigated based on the small-signal modeling. The leakage inductance value is optimized in view of system reliability and better dynamic performance. Besides, to improve the dynamic performance further, feedforward control employing optimized feedforward coefficient based on the small-signal analysis is implemented. A 4-kw prototype composed of two bidirectional dc–dc converters is built to verify the effectiveness for the proposed control strategy in AC motor drive application with fast regenerative braking.

Backflow Power Optimization Control for Dual Active Bridge DC-DC Converters

This paper proposes optimized control methods for global minimum backflow power based on a triple-phase-shift (TPS) control strategy. Three global optimized methods are derived to minimize the backflow power on the primary side, on the secondary side and on both sides, respectively. Backflow power transmission is just a portion of non-active power transmission in a dual active bridge (DAB) converter. Non-active power transmission time is proposed in this paper, which unifies zero power transmission and backflow power transmission. Based on the proposed index, an optimized control method is derived to achieve both the maximum effective power transmission time and minimum current stress of DAB at the same time. A comparative analysis is performed to show the limitations of the minimum backflow power optimization method. Finally, a prototype is built to verify the effectiveness of our theoretical analysis and the proposed control methods by experimental results.

Improved Boundary Operation for Voltage-Fed Semi-DAB With ZVS Achievement and Nonactive Power Reduction

An improved boundary operation is proposed for the voltage-fed semi dual active bridge converter for applications needing only unidirectional power flow capability. The leakage inductor current works in boundary mode under most operating conditions. The operating principle and comparison with conventional single-phase-shifted control are presented in detail. The nonactive power can be suppressed under most working conditions and the conduction loss for output MOSFETs can be reduced significantly. All the power switches can achieve zero-voltage switching (ZVS) while the output side rectifying diodes can obtain zero-current switching in most operating conditions. The parameter design including the compensated value and the dead-time selection is given. The ZVS achievement can be obtained with reduced nonactive power and the closed loop implementation can be simplified. The effectiveness of the control strategy has been validated by the experimental results of 1-KW hardware prototype.

Reactive Power Billing Under Nonsinusoidal Conditions for Low-Voltage Systems

This paper analyzes reactive power definitions for billing purposes in low-voltage installations with high harmonic distortion levels. First, the theoretical definitions of power under nonsinusoidal conditions and their outcomes are presented and two of them are chosen as the focus to determine which one is the most appropriate for billing: nonactive power and fundamental reactive power. The regulatory framework of different countries is then analyzed and compared with the theoretical definitions. Subsequently, different reactive power measurement methods are analyzed and their outputs are again compared with the definitions. Simulations performed with typical nonsinusoidal voltage and current signals show that several measurement techniques can easily be used for fundamental reactive power measurement, whereas the measurement of nonactive power requires more effort. Finally, a regulatory comparison of the pros and cons of each reactive power quantity is conducted. It is concluded that the surplus of reactive power in electricity grids should be controlled via fundamental reactive power (or displacement power factor), since it is independent of the harmonic distortion, the responsibility for it can be easily assigned, and it is easy to be measured with the use of several simple electronic measurement techniques.

Survey about Classical and Innovative Definitions of the Power Quantities Under Nonsinusoidal Conditions

AbstractToday, electric power and energy measurements are widely required, practically in all the research, industrial and consumer applications. Power measurements are of importance primarily for the test, monitoring and maintenance of energy supply networks and electric equipment. The measurement of both electric power and energy is a still open research problem in the electrical engineering community. Phenomena like harmonic distortion, noise, transients, over-voltages and voltage dips have increased the difficulty in achieving accurate measurements, compared with the case of sinusoidal signals. Many of the non-active power component definitions that have been proposed cannot be implemented in the traditional electro-mechanical or solid-state meters, but require the adoption of more expensive and time-consuming digital techniques; recently, some new approaches for the definition of power quantities have been investigated. In this paper, a survey of the classical and innovative definitions is proposed, with the aim of summarize the different points of view outlined by the researchers. A case study of power factor correction in nonsinusoidal conditions is also presented, to give a numerical comparison about the power quantities measured according to the various approaches.

Load Sharing in Ship Microgrids Under Nonsinusoidal Conditions—Case Study

The paper is focused on the problem of load sharing between generators running in parallel in ship microgrids loaded by variable-speed drives with power converters. It is based on an experimental study of a number of real cases recorded on three ships. Chosen power quantities defined in the IEEE 1459-2010 standard are calculated, and their sharing between generators working in parallel in ship systems are assessed. Particularly, sharing of active, nonactive, and apparent power as well as active, reactive, and apparent power of voltage and current fundamental components is determined for various loads. The levels of voltage and current distortions as well as harmonic power flow are also assessed. The results are commented on in the wake of related provisions of ship classification societies rules. Finally, it has been determined that there are differences between sharing of various power components, which must not be neglected, particularly in the case of nonactive power and fundamental reactive power. Therefore, amendments to related ship classification societies rules are necessary.

Active power measurement in arc welding and its role in heat transfer to the plate

A contemporary paper claimed that a method using the resistance of impedance (active power) for arc power calculation is more accurate than the conventional approach, with consequences on the actual heat transfer to the plate. However, despite the comprehensive reasoning, no heat-related results are shown in this intriguing paper to support the claim. Thus, the aim of this work was to apply the proposed method for determining the weight of active power in the total arc power. A series of weldments was carried out, by using GTAW in constant and pulsed current modes and short-circuiting GMAW with different inductance settings. The effect of the active power on the heat transfers to the plate was assessed by both bead cross-section geometries and calorimetry. The results showed that even a significant fraction of active power of the total power was reached, no changes in bead geometry or heat input were found. A review of the assumptions used in the primal paper showed that an arc is better represented by an ER circuit than by an RLC circuit. As a conclusion, the arc as a reactance-free load presents no component such as non-active power and the conventional approaches are accurate methods to measure arc power, representing the actual active power.

Real-Time Power Measurement Using the Maximal Overlap Discrete Wavelet-Packet Transform

This paper proposes the real-time estimation of the root-mean-square (rms) values, primary power quantities (active, total apparent, nonactive power, and power factor), and distortion power using the maximal overlap wavelet packet transform (MODWPT). The MODWPT provides a uniform frequency band and possesses the time-invariance property, which is ideal for the real-time power estimation. The performance of the proposed wavelet-based power measurement was assessed and compared to the IEEE Standard 1459-2010 in different case studies including stationary synthetic waveforms and power quality disturbances in experimental setup. The proposed method presented good results in the estimation of rms values and primary power quantities by using compact mother wavelets, whereas the estimation of distortion power was better with long mother wavelets.

Unified Boundary Trapezoidal Modulation Control Utilizing Fixed Duty Cycle Compensation and Magnetizing Current Design for Dual Active Bridge DC–DC Converter

The unified boundary trapezoidal modulation (TZM) control utilizing fixed duty cycle compensation and magnetizing current design for dual active bridge dc-dc converter is proposed in this paper. The fixed duty cycle compensation and magnetizing current design are first introduced to achieve the zero voltage switching (ZVS) of the power switches, which cannot be ensured with the conventional TZM control. As a result, all the power switches of dual active dc-dc converter can achieve ZVS and four switches can be turned off with very low current. Besides, based on the revealed power transfer characteristic, the power control variables including the duty cycles and phase-shift ratio can be unified without lookup tables or operation region division. With the proposed boundary TZM control, circulating current losses can be reduced and nonactive power is significantly suppressed according to the mathematic analysis, resulting in decrease of the conduction loss. A 1.6-kW laboratory prototype is built to verify the theoretical analysis and effectiveness of the proposed control.

Harmonic source identification in distribution system using non-active power quantities

A new method to identify the location of the harmonic generating sources in a distribution network has been proposed in this paper. The method is based on the wavelet decomposition of voltage and current signals at the point of measurement. Three non-active power quantities have been chosen which can represent only the harmonic components present in the system. The exact location of the dominant harmonic generating source can be found out with the help of the chosen non-active powers. The effectiveness of this method is studied on a three phase radial distribution system. It has been shown through different case studies that the proposed strategy is very effective in locating harmonic source present either in upstream or downstream of the metering section.

Harmonic source identification in distribution system using non-active power quantities

Harmonic source identification in distribution system using non-active power quantities