Unified Power Quality Conditioner Upqc Matlab

Piotr Kuwałek

Institute of Electrical Engineering and Electronics

Poznań, Poland

Abstract—Low-frequency disturbances of power quality are one of the most common disturbances in the power grid. These disturbances are most often the result of the impact of power electronic and energy-saving devices, the number of which is increasing significantly in the power grid. Due to the simultaneous operation of various types of loads in the power grid, various types of simultaneous disturbances of power quality occur, such as voltage fluctuations and distortions.

Therefore, there is a need to analyze this type of simultaneous interaction. For this purpose, a special and complementary laboratory setup has been prepared, which allows for the examination of actual states occurring in modern power networks. Selected research results are presented for this laboratory setup, which determine its basic properties. Possible applications and possibilities of the laboratory setup are presented from the point of view of current challenges.

Keywords— power quality, power grid model, laboratory setup,

I. Introduction

Low-frequency disturbances of power quality are one of the most common disturbances in the power grid . Low-frequency power quality disturbances include: voltage fluctuations, voltage distortions caused by higher harmonics or sub-, inter- or supra-harmonics, frequency fluctuations, etc.

These disturbances occur most often as a result of the impact of electronic and energy-saving devices , the number of which in the power grid has been increasing significantly in recent years. Due to the simultaneous operation of various types of loads in the power grid, various types of simultaneous disturbances of power quality occur. One of the most common simultaneous disturbances in the low-voltage network are, for example, voltage fluctuations and voltage distortions caused by higher harmonics . The "clipped cosine" voltage distortion is common in low-voltage networks and is caused by the input stages of switching power supplies. If a load that periodically changes its operating state is connected to such a network, simultaneous voltage fluctuations and voltage distortions occur as a result . In recent years, simultaneous power quality disturbances have also been shown to cause negative effects that are unobservable for individual disturbances occurring separately . For example, for voltage fluctuations alone, a flicker can occur as a result of a change in the operating state at a frequency of 3fc, where fc is the power frequency . In turn, in the case of simultaneous voltage fluctuations and voltage distortions, a flicker can occur for the load that changes its operating state with a frequency whose limit value depends on the level of supply voltage distortion and can be greater than 3fc .

Therefore, it is a need to analyze this type of simultaneous interaction . It is worth noting that in the currently applicable normative documents in the field of methods for measurement and assessment of low-frequency disturbances (e.g. the standard

Standard

IEC 61000-4-7 in the field of voltage/current distortion measurements or the standard IEC 61000-4-15 in the field of flicker assessment (voltage fluctuations)), idealized states are considered or certain models are proposed that recreate the state of occurrence of a low-frequency disturbance of only one type. This analysis facilitates the testing of measuring instruments and simplifies the assessment of the propagation of disturbances in the power grid. It is worth noting, however, that such an analysis does not guarantee a small measurement error in the event of actual disturbance states typical of modern power networks.

Examples of discrepancies in measurement results in the research with the normative approach and in the research with the approach recreating actual disturbance states can be observed for AMI smart energy meters equipped with the

Power Quality Assessment Functionality . To Some

extent, the simultaneous occurrence of low-frequency disturbances can be recreated using a high-power broadband arbitrary generator. However, the assessment of the propagation of disturbances in the event of their simultaneous occurrence requires a specialized laboratory setup. Taking into account the indicated needs, a special and complementary laboratory setup was prepared, which allows for the examination of the actual conditions that occur in modern power networks. The paper discusses the construction of this unique laboratory setup. Selected research results are presented for this laboratory setup, which determine its basic properties. Possible applications and possibilities of the laboratory setup are presented from the point of view of current challenges.

Ii. Description Of The Laboratory Setup

The specialized laboratory setup is shown in the block diagram in Fig. 1. Fig. The block diagram of the laboratory setup for testing low-frequency

Disturbances Of Power Quality

This work was funded by National Science Centre, Poland – 2021/41/N/ST7/00397. For the purpose of Open Access, the author has applied a CC–BY public copyright licence to any Author Accepted Manuscript (AAM) version arising from this submission.

reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or In the diagram shown in Fig. 1, five blocks are indicated:



measurement section. The actual view of the laboratory setup is shown in Fig. 2. The presented laboratory setup can be used, for example, for:



research in the field of evaluating the propagation of



research on the identification and localization in sources of disturbances of power quality (including,



assessment of the interaction between power quality



post-factum examination of disturbance states in the



post-factum testing of voltage-supplied loads in the presence of various power quality disturbances .

A. Power Grid Model

The most important element of the laboratory setup is a single-sided power supply model of branching 3-phase power grid with a radial topology. This is a typical model for low- voltage networks, where low-frequency disturbances of power quality occur most often. The diagram of the power grid model is shown in Fig. 3. The prepared power grid model consists of six sections, where sections III and IV are included in the first branch, and sections V and VI are included in the second branch. In the prepared power grid model, individual resistance values Ri and inductance Li were selected in such a way as to obtain typical conditions typical for an overhead line. The nominal values of the resistance RN of the resistors used and the inductance LN of the coils used are presented in Table I.

Fig. 3. The Diagram Of The Power Grid Model

The individual power supply points Pi of the power grid model



power connections allowing for the connection of a

Measurement Connection Allowing For The Recording

of voltage signals from individual points of the power

Measurement Connection Allowing For The Recording

of current signals using clamp current transformers

From Individual Points Of The Power Grid Model

[copper wire with a cross-section of 4 mm2].

6.8

The power grid model has lumped parameters corresponding to the distributed parameters of the real long line. Taking into account this fact and the fact that the connections for recording voltage signals are shielded, the prepared laboratory setup ensures effective suppression of external interferences that could affect the correctness of the analysis. Fig. 4 shows a photo of a part of the neutral line mounted on the radiator. It is also worth noting that it is possible to slightly modify the prepared power grid model by connecting capacitances to the power terminals in parallel (in the case of the designed model, the capacitances can be in the order of nF), which allow the model to be changed from an overhead line model to a cable line model.

Fig. 4. The view of a fragment of the neutral line mounted on the radiator

B. Power Supply Section

The power supply section ensures that the supply voltage is supplied to the power supply point P1 of the prepared power grid model. The prepared power grid model allows the free connection of various types of power supply according to

Supply Voltage Directly From The Fluke 5500A

calibrator [impact analysis for nominal conditions - functional test signals generated with an inaccuracy

Amplifier [Analysis Of Impacts For Conditions

recreating real disturbance states in modern power



supply voltage directly from the MV/LV transformer station with a power of 630 kVA [impact analysis for

Real Conditions - Study Of The Propagation Of

disturbances generated by the tested real loads, study

Voltage And The Operation Of The Selected Load In

controlled conditions in which the added loads are



supply voltage from any source that is not currently available in the laboratory and which allow testing of conditions specified by a specific user.

C. Control Section

The control section allows for independent switching of connected loads, synchronously or asynchronously. The control is implemented by an SSR system based on a MOSFET transistor, which allows for achievement of maximum switching at the kHz level. In addition, the use of an SSR system based on a MOSFET transistor allows the load to be switched on and off at any time, without delays of µs between the appropriate edge of the control signal and the change of the switch state. Fig. 5 shows a simplified diagram of a single switch. 6 shows the view of individual switches mounted on the radiator.

Fig. 5. The Simplified Diagram Of A Single Switch

Fig. 6. The view of individual switches mounted on the radiator The control system presented in Fig. 5, apart from the assessment of the propagation of disturbances after turning on or off a specific load, also allows for recreation of the operation of a group of loads or selected power electronic systems. In such a case, it is sufficient to use elements such as a resistor, coil, and capacitor in a series or parallel configuration as a load. The indicated elements allow for simulation of the nature of the load, and the switching frequency allows for recreation of the variability of the operating state of a specific device (e.g., inverter). The control

System Is Operated From A Computer Via The Esp32

microcontroller. The individual digital outputs of the ESP32 system are fed to a voltage driver, which appropriately amplifies the signal and has an appropriate current carrying capacity. Switching of the control system on the AC side is possible by using a Greatz bridge. Additionally, the Schottky diode to the SSR output provides additional protection of the switch against possible overvoltages that can arise as a result of switching.

D. Load Section

The load section available at the laboratory setup includes:



resistors in the form of convection heating systems with an active power of 0.75 kW, 1.25 kW, or 2 kW;



capacitors with a capacity of 9.6 µF and a reactive



chokes with an inductance of 1.123 H and a reactive



selected specific loads, such as UPS with an apparent power of 1.8 kVA, electric vehicle charger, selected

Led Or Fluorescent Light Sources, Switching Power

supplies, etc. The laboratory station is configured in such a way that it is also possible to connect any other real load supplied from the low-voltage network to analyze the disturbances emitted by it and the impact of other disturbances of power quality on the operation of this device.

The Measurement Section Allows For Synchronous

(simultaneous) or asynchronous recording of low-voltage signals with a value not exceeding 20 V. PicoScope 5444D PC oscilloscopes are used as recorders. The PicoScope 5444D PC oscilloscope provides recording with a sampling rate of 1GSa/s at 8-bit resolution or 62.5 MSa/s at 16-bit resolution.

The bandwidth of this recorder is 200 MHz. The following are used to acquire voltage signals from the laboratory setup:

Deployment In Out-Of-Position Situations

D. Bendjaballah1, A. Bouchoucha1, M. L. Sahli1,2* and J-C. Gelin2

Abstract

Side-impact collisions represent the second greatest cause of fatality in motor vehicle accidents. Side-impact airbags have been installed in recent model year vehicle due to its effectiveness in reducing passengers’ injuries and fatality rates. In meeting these requirements, simulations of folding and deploying airbags are very useful and are widely used. The paper presents a simulation method for the deploying airbags using three materials in different working conditions. Finite element analysis is primarily used to evaluate this concept. In these simulations, the gas flow is described by the conservation laws of mass, momentum, and energy. The numerical results indicate that the FE method in this paper is capable of capturing airbag deploying process accurately.

Keywords: Airbag simulations, Out-of-position, Crash, Modeling, Out-of-position

Background

The passive safety of cars has become a very high prior- ity issue for the automotive industry. Today, there are not only one or two airbags in a car; certain models have ten times more than that. With the increasing usage of airbags, the number of accidents where the airbag itself can cause an injury to the occupant also increases

(Augenstein Et Al. 2003; Gabauer And Gabler 2010;

Audrey et al. 2011). As is well known, safety belts are also now devices designed to provide protection to the users of vehicles during crash events, minimizing the loads necessary to adapt their movement to the move- ment of the car (Freesmeier and Butler 1999; Schmitt et al. 1997). In general, the seat belt is designed to restrain the occupant in the vehicle and prevent the

Occupant From Having Harsh Contacts With Interior

surfaces of the vehicles. The airbag acts to cushion any impact with vehicle structure and has positive internal pressure, which can exert distributed restraining forces over the head and face. As a safety component of auto- mobile, an airbag decreases occupants’ injury likelihood effectively in case of an accident (Ruff et al. 2007). These safety elements can reduce the death rates on the roads, and its protection effects have been widely approved (Crandall et al. 2001; Teru and Ishikawa 2003). With computational tools such as finite element methods designed for dynamic contact problems, crashworthiness simulations can now be used with reliable accuracy to evaluate occupant protection in various collision condi- tions with safety metric/parameters such as acceleration, head injury criteria, intrusion distance, intrusion vel- ocity, and neck forces (neck injury risk or whiplash).

Thus, new types of airbag products are being developed to handle different collision scenarios.

Become Standard Equipment On Most New Passenger

vehicles (Braver and Kyrychenko 2004; Teng et al. 2007; Yoganandan et al. 2007). The airbag cushion is com- posed of a woven fabric which is rapidly inflated during a car crash. The airbag dissipates the passenger’s kinetic energy thereby reducing injury through biaxial stretching of the fabric bag and escaping gas through vents. There- fore, the performance of the airbag is greatly influenced by the mechanical properties of the fabric. Generally, air bags are designed to deploy in a crash that is equivalent to a vehicle crashing into a solid wall at 8 to 14 mph.

Air bags most often deploy when a vehicle collides with another vehicle or with a solid object like a tree. There are various types of airbags: frontal, side-impact, and curtain airbags. In general, the passenger side airbags are usually larger than the driver airbags (see Fig. 1).

Besançon, France

© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Bendjaballah et al. International Journal of Mechanical

Doi 10.1186/S40712-016-0070-2

Extensive studies have shown that the airbag deploy- ment in load cases consists of two occupant loading phases: a punch-out effect where the airbag bursts out of its container with the airbag and airbag module cover accelerating towards the occupant and a second loading phase during which the airbag is taking on its deployed shape and volume (membrane-loading effect). Bankdak et al. (2002) developed an experimental airbag test system to study airbag-occupant interactions during close proximity deployment. The results provided insight for simulating the effect of inflation energy and mass flow on target response. Bedard et al. (2002) found that while left-side (driver-side) impacts accounted for only 13.5% of all crashes, the fatality rate among these

Crashes Was 68.3% In Comparison To Front Impact

(48.3%), right-side impact (31.3%), and rear impact (38.4%). These studies underscore the importance of oc- cupant safety during side-impact collisions. In the last years, the current market requested to reduce the time and cost airbag development. In order to achieve this result, virtual simulations play an important role since they allow to minimize the number of experimental tests (Pei et al. 2013; Cao et al. 2014). Several simulation models of airbag were established (Wang et al. 2007). It is feasible to optimize the parameters of airbag deploy- ment using simulation technology. Experimental and numerical studies have quantified injury risks to close- proximity occupants from deploying side airbags. These studies have focused on the prevention of the most ad- verse effects of airbag deployment (Duma et al. 2003).

Other studies have proposed airbag characteristics to minimize particular biomechanical responses (Haland and Pipkorn 1996). In a more recent study, Marklund and Nilsson (2003) compared deformation patterns with experimental data as well as the computational costs associated with three different airbag deployment simu- lation methods; they concluded that the SPH method is relatively inexpensive and produces incremental deform- ation patterns that compare most closely to the experi- mental results. The process of inflation of an airbag is one of the determining factors in saving lives. The duration from the initial impact of the crash to the full inflation of an airbag is about 40 ms, and during this time, the airbag goes from being in a folded state to a fully inflated state, with a high internal pressure. After achieving this state, the airbag begins to deflate, thus providing a nice cushion for the body impacting it.

Ideally, the person in the crash should come into contact with the airbag at this time. In the present study, a large volume passenger side airbag model is developed to handle different collision scenarios. The main aim is evaluate the performance of deploying of passenger side airbag using finite element methods (FEM).

Materials

The tensile specimens were made in different airbags (P: Peugeot, R: Renault, and VW: Volkswagen) with a length of 200 mm long and a width of 40 mm. Table 1 shows the mechanical properties of the airbag.

Tensile Tests

To determine the mechanical properties of the material of airbag used in the test pieces, tensile tests were performed on Lloyd EZ20 universal testing machine in Constantine. These tests were conducted using rect- angular samples. The axial force and axial displacement acquired during a test are converted into stress and the strain in order to be used for the fabric material model.

The continuous recording of the stress-strain data was performed during both the load and unload phases. A minimum of five samples were made in order to check the repeatability of the measurements. All the data was collected by using a PC-based data acquisition system and analyzed by commercial software. The picture frame test device that is made for this study is shown in Fig. 2.

Fig. 1 a Frontal and side airbags. b Oblique view of facet occupant model in sitting posture following airbag deployment (Lim et al. 2014)

0.150

Bendjaballah et al. International Journal of Mechanical and Materials Engineering (2017) 12:12

Page 2 Of 9

Figure 3 shows the stress-strain relationship of the airbag sample under axial tensile loads. The results are showing a linear increase in extension with the increas- ing stresses. This is an expected output and it confirms with the theoretical behavior of a sample subjected to tensile stress. The rupture strain values for different airbags (R/P/VW) were 0.322, 0.441, and 0.472, respect- ively. The measured elastic parameters (i.e., Young’s modulus E and initial yield strength) and Poisson’s ratio are summarized in Table 2. The tensile tests of the woven fabrics can show differences on mechanical prop- erties because woven fabrics can resist in-plane shear loads once the yarn lock-up angle has been reached. The differences of material property on material direction can affect the shape of fully deployed bag (see Fig. 3b).

Theoretical Background

Numerical simulations of airbags use very complex and techniques such as an orthotropic model to identify the mechanical behaviors during the airbag inflation and the fluid mechanics (gas flow) to describe the inflator gas flow (pressure gradient) and improve the representation of the pressures within the airbag. To model the airbag as an orthotropic model, three material constants have to be provided. Assuming a plane stress condition, the

Ð1Þ

where σ is the normal stress and τ is the shear stress, the subscript refers to the principal material directions, i.e., the fill and warp directions. Also, ε and γ are the strain components. The material elastic constants Qij are

Ð2Þ

where E1 and E2 are the Young’s modulus in the fill and wrap directions and G12 is the shear modulus of the fabric material. νij is the Poisson ratio of the material.

The gas exerts a pressure load on the airbag causing it to expand. This expansion puts the airbag under tensile stress lowering the expansion rate. In this study, heat conduction and heat transfer is not taken into account.

Fig. 2 A photograph of Lloyd EZ20 universal testing Fig. 3 Stress versus strain using Lloyd EZ20 machine for a three different airbags at 0° and 90° and b VW airbag test specimens at

Different Angles

Table 2 Physical and mechanical properties of the airbag

Page 3 Of 9

In the deployment of an airbag, an inflator supplies high velocity gas into an airbag causing it to expand rapidly. The gas inside the airbag is assumed to be ideal, to be of constant entropy, and to satisfy the equation of state:

Ð3Þ

Here p, ρ, and e are respectively the pressure, density, and specific internal energy, and γ is the ratio of the heat capacities of the gas. The gas flow is described by the conservation laws for mass, momentum, and energy that

Ð4Þ

here, V is a volume, A is the boundary of this volume,

N Is The Normal Vector Along The Surface A, And U

denotes the velocity vector in the volume. Applying Bernoulli’s equation in the case of an ideal gas with

Ð5Þ

Here, the subscript ex denotes quantities at the throat of the tube. Furthermore u, p, and ρ denote the quan- tities inside that part of the tube that is supplying mass.

Materials And Boundary Conditions

The airbag system mainly consists of three parts: the airbag itself, the inflator unit, and the crash sensor or diagnostic unit. Thus, to study the behavior of the airbag using FE simulations, we need to have an FE model of the airbag in the folded position. A FE model of the airbag was used to simulate the test condition as shown in Fig. 5. LS-DYNA® material model FABRIC (MAT_34) is used to simulate the airbag material. It is a variation of the layered orthotropic material model. Additionally, in the LS-DYNA® material model, fabric leakage can be accounted for. However, for this CAB material, the leak- age is almost negligible and therefore no leakage is specified. The mechanical properties can be determined from the physical test. Typical material properties for airbag fabrics are taken as given in Chawla et al. (2004a) (Table 3). These properties are used to simulate inflation process of airbag (see Table 1). The car dashboard is modeled as the rectangular thin plate using a MAT_RI-

Gid Material, And The Degrees Of Freedom Are Con-

strained in all the directions. The similar properties of thermoplastic polymer are assigned for contact purposes. The porosity of the fabric is assumed zero. The nitro- gen gas is taken for inflating the airbag. Properties of nitrogen gas and initial bag conditions are shown in Table 4. The example on which we perform the study is a typical passenger side airbag. The geometric de- tails have been measured from a commercially avail- able airbag. The initial state of the airbag is a closed rectangular whose sides are to be finished to 482 × 635 mm2 and is shown in Fig. 4.

Table 3 Material properties of airbag and rigid plate used in FE

–

Table 4 Initial values used for FE simulation of the swelling of

3.33 × 10−4

Fig. 4 The initial airbag geometry in the form of a rectangular Bendjaballah et al. International Journal of Mechanical and Materials Engineering (2017) 12:12

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