Park Transformation Research Articles

Optimization of efficiency for power system using three phase AC to AC matrix converter with the algorithm of fuzzy controller

This paper suggested a new contribution of three phase AC to AC matrix converter MC via fuzzy logic controller FLC to enhance the whole system. However, the weakness of matrix converter is that the input- output voltage transfer is control to 87% for input and output waveform. Also, matrix converter is more sensitive to the trouble of input voltage which deteriorates the system performance. To overcome these problems, and to improve the efficiency of system, FLC with matrix converter is proposed to minimize the sensitivity to the load, and to increase voltage transfer. In this paper the currents a,b,c are converted to alpha and beta current via Clarke transformation . In this method two FLC are used. The error (between alpha current and reference current) (e) and the change of this error (de) will apply to first FLC. The output of FLC is actual alpha current. In the other hand, the error of beta current and the change of error are also passes through the second FLC to produce the actual beta current. The actual alpha and beta current is converted to direct and quadrature d-q current by park transformation. The d-q current is converted to (a, b, c) out currents by inverse park transformation, the results of this method express that the matrix converter with FLC is more capable, high accuracy with better efficiency as compared with conventional matrix converter system.

Comparison and Analysis of Evaluation Indexes regarding China’s Eco-industrial Parks

The industrial park plays a significant role in fueling the economic growth, expanding the foreign trade and promoting the industry cluster. However, due to the blind investment attraction, and the poor perspectiveness and systematicness of the planning, the industrial park also becomes the centralized pollutant emission area. Chinese government has implemented many meaningful explorations in promoting the ecological development of the industrial parks, successively introduced the demonstration eco-industrial park, circular transformation of industrial park, and green park construction, and separately established the evaluation index system and policy guarantee system. This paper reviews the ecological greening development course of China’s industrial parks, thoroughly introduces the evaluation index system of demonstration eco-industrial park, circular transformation index system of the industrial park, and the green park evaluation index system, and compares and analyzes the commonalities and differences of such three sets of index systems from the theoretical basis, target positioning, index requirements, index universality, evaluation methods and many other dimensions, based on which this paper proposes the policy suggestions regarding the ecological greening development of China’s industrial parks.

Research on Test of Key Parameters of On-Load Tap-Changer in Transformer

There are two main testing methods for the key parameters of the transformer on-load tap changer. One is the DC test method and the other is the AC test method. Based on the AC test method for on-load tap changer key parameters, a new test scheme was proposed. The on-load tap changer switching operation of the transformer can be simulated by establishing a model. The waveforms of the transitional AC current and the testing AC voltage are stored and preprocessed. Then the transitional AC current is equivalent to DC components through the Park transformation. By using the off-line identification algorithm, the transient stage of the transformer on-load tap changers can be determined and the transition resistance value can be accurately calculated.

Large-Signal Impedance-Based Modeling and Mitigation of Resonance of Converter-Grid Systems

Large-signal impedance of grid-connected converters can be used to predict resonance-generated distortions in converter-grid systems. Note that the large-signal impedance of a network represents its impedance response for different magnitudes of perturbation injected at its terminals. This paper presents large-signal impedance-based modeling and mitigation of resonance of grid-connected voltage source converters. Challenges of large-signal modeling because of the inapplicability of the small-signal approximation are addressed by leveraging the dominating influence of hard nonlinearities (such as pulsewidth modulation saturation and limiters) over soft nonlinearities (such as Park's transformations and phase-locked loop (PLL)) in shaping the large-signal behavior of the converter. The paper develops large-signal gains of hard nonlinearities using different types of describing functions. The paper shows that the large-signal impedance of a voltage source converter (VSC) can be shaped to reduce resonance-generated distortions by inserting limiters in the control system of the VSC. Developed large-signal impedance models are validated using numerical simulations of a VSC with dq current control and PLL. Large-signal impedance measurements of a commercial 1 MW VSC-based inverter and a medium-voltage doubly-fed induction generator with approximate 4 MW rating are presented to experimentally demonstrate the influence of the injected perturbation magnitude on the impedance response.

Discrete-time PMSM Modeling Including Park Transformation and Decoupling Control Based on the Proposed Model

Discrete-time PMSM Modeling Including Park Transformation and Decoupling Control Based on the Proposed Model

Control of Grid-Connected Voltage-Source Converters: The Relationship Between Direct-Power Control and Vector-Current Control

This article discusses the mathematical relationship between gridvoltage-modulated (GVM) direct-power control (DPC) and vector-current control (VCC) for three-phase voltage-source converters (VSCs). GVM-DPC is equivalent to VCC at the steady state, and it presents a superior transient performance by removing the need for the phase-locked loop (PLL). This means that GVMDPC solves the disadvantage of conventional DPC, such as poor steady-state performance. Moreover, GVM-DPC will reduce the computational burden in comparison with VCC due to the absence of Park transformation and PLL. Consequently, we can expect that the GVM-DPC method will be capable of plug-and-play for VSCs. Finally, the experimental results match the theoretical expectations closely.

Principle of Torque-Angle Approaching in a Hybrid Rotor Permanent-Magnet Motor

This paper reveals a torque-angle approaching principle in a hybrid rotor permanent-magnet (HRPM) motor. The key is to obtain the relationship between angles of shifted surface-inserted PMs (SPMs) as well as assisted airspace barriers and the current angles of maximum PM torque as well as maximum reluctance torque. In order to find out this relationship, the PM torque and reluctance torque are separated accurately and effectively by the proposed torque separation method. In this method, the parameters in an abc reference frame are transformed to a d- - q reference frame via Park transformation, and then the model considering cross-coupling and magnetic saturation effect is used to calculate four torque components. Moreover, the shifting of SPMs has been confirmed to have both influence on the current angles of maximum PM torque and maximum reluctance torque, while the assisted airspace barriers only affect the current angle of maximum reluctance torque. Thus, the total torque can be enhanced by optimal angles of shifted SPMs and assisted airspace barriers because of higher utilization of both PM torque and reluctance torque. In order to evaluate the presented principle in the HRPM motor, a prototype is manufactured for experiments. Through theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective.

Single stationary domain equivalent inverter admittance for three‐phase grid‐inverter system considering the interaction between grid and inverter

Admittance matrix has been used to represent the characteristics of three-phase inverter for grid-inverter system stability evaluation in both stationary, sequence, and dq domain. For the dq domain admittance matrix, the PLL and Park transformation introduce additional dynamics during the admittance measurement that may influence the application of dq model. For the stationary and sequence domain admittance matrix, the model measurement is not affected by the above additional parts but may also encounter other difficulties in actual measurement. First, current frequency response analyser (FRA) is not able to perform two-frequency measurement required by the admittance matrix. Second, practical limitations exist in the course of solving complex-valued admittance matrix equations. Here, a single stationary domain equivalent admittance of three-phase inverter for grid-inverter system with considering the interaction between grid and inverter is defined so that the above two difficulties can be avoided. Then, an equivalent admittance model of prototype inverter is constructed for stability analysis of the grid-inverter system using Nyquist stability criterion, instead of the generalised Nyquist criterion (GNC). The effectiveness of the proposed equivalent inverter admittance model is validated through simulation and experiment verification.

How the Winding Type Should Be Taken into Account in the Model of an Asynchronous Machine

Asynchronous electric drive with vector control is described by a system of nonlinear differential equations. The analysis of vector control uses a model of an ideal asynchronous machine (with a sinusoidal distribution of magnetic induction in the air gap), where the coefficients of mutual magnetic communication between the windings are calculated by means of the cos(θ) function. Simulation in MATLAB has shown that the processes significantly depend on the type of windings. The type of windings is taken into account in coefficients of the magnetic coupling between the windings kMA(θ). If the function of cos(θ) is replaced with the product of cos(θ)KAa(θ) = kMA(θ) in the equations of the model of an ideal asynchronous machine, then the type of windings of the asynchronous machine will be considered by a correction function KAa(θ). The coefficients of the magnetic coupling between the windings (the ratio of the magnetic flux connections of the windings) were calculated by a modified method of conducting the gear contours. Dimensionless correction functions allowed specifying the vector transformation of Clarke and Park.

Flux Observer Model for Sensorless Control of PM BLDC Motor With a Damper Cage

Sensorless control methods are commonly employed to derive the rotor position and speed information indirectly in permanent magnet (PM) brushless motor drives. Thereinto, the simple yet effective flux observer method is extensively applied in a wide range of applications. However, damper cage is sometimes employed in the rotor of certain PM brushless motor. Normally, high-order current harmonic components occur in such damper cage during operations. The introduction of these extra current contents can significantly hinder the performance of the conventional flux observer. By applying Park transformation, the fundamental harmonic components of stator phase currents, flux linkages, and voltages during steady-state operation, become constants under rotor synchronous reference frame, while the currents in the rotor damper cage are still alternating. In this paper, an improved flux observer method is proposed to filter the harmonic contents under the rotor synchronous reference frame for PM brushless motor with rotor damper cage. The validity and performance of the proposed flux observer are verified by both numerical analysis and experimental results.

Separation and comparison of average torque in five‐phase IPM machines with distributed and fractional slot concentrated windings

This study proposes a method to separate average permanent magnet (PM) torque and average reluctance torque of five-phase interior permanent magnet (IPM) machine based on transient finite element method (FEM). The key of this method is to count total torque as four torque components by considering the saturation and cross-magnetisation between d – q axes, and every torque components are calculated from d–q axes parameters directly. The parameters in d–q axes reference frame are transformed from ABCDE reference frame via five-phase Park transformation. Comparing with the existing methods, the proposed method maintains the same accuracy while time saving because d–q axes parameters can be obtained directly by one-time FEM simulation. Meanwhile, the proposed method is adopted to separate the PM torque and reluctance torque from two five-phase IPM machines with fractional-slot concentrated winding (FSCW) and integral-slot distributed winding (ISDW). Finally, the FEM and experimental results show that the IPM machine with FSCW produces lower reluctance torque ratio than that of IPM machine with ISDW. Besides, the results demonstrate that the flux-weakening performance connects with characteristic current (Ψ PM d / Ldd ) strongly.

On the Existence of Lagrangians for Clarke and Park Transformed Switched-Mode Electrical Networks

It is well-known that the classical passivity-based control (PBC) design is founded on the existence of the Euler-Lagrange (EL) equations. For a large class of systems, including mechanical, electrical, and electro-mechanical systems, its application is usually rather straightforward and requires a standard Lagrangian formulation. For three-phase electrical networks, with or without switches, it is often desirable to reformulate the resulting equations of motion into an orthogonal reference frame using the Clarke or Park transformation, or a combination of both. However, such transformations are always performed after the EL equations have been set up and a formal procedure to obtain the transformed equations directly from a Lagrangian thus far lacks in the literature. The contribution of this paper is to show that, by invoking the Helmholtz conditions and the concept of the traditor, such Lagrangians do exist, but require the inclusion of certain non-energetic cross terms.

Research on the Switching Arc Loss of on-Load Tap Changer

The on-load tap changer (OLTC) switching arc will affect the life of the contact, so it is necessary to test its working condition. Based on DQ coordinate transformation, fundamental wave component extraction, and wavelet algorithm, proposed an OLTC arc detection method based on energy conservation theory in this paper. Used the fundamental wave component extraction algorithm extracted the transformer excitation parameters, and established the OLTC equivalent circuit by combining the Habedank arc model. Compared the differences between the follow effect and frequency calculation of simulated and measured waveforms, which were caused by the five orthogonal transformation algorithms, including Transport-Delay, Hilbert Transformation, Inverse Park Transformation, SOGI and Improved SOGI. The DQ coordinate transformation based on the Transport-Delay orthogonal converter is determined to calculate the active power of each part of the circuit. According to the principle of energy conservation, obtained the data of arcing loss under nine simulated conditions. Based on the simulation circuit, built the OLTC prototype and dSPACE hardware in loop simulation platform, and measured three load conditions. The sampling signal was filtered by the wavelet algorithm. Considering the measurement and calculation errors, the simulation and measured results show that the actual arcing power has a consistent change with the calculated value between different working conditions, and the maximum difference between simulation results and measured results is thirty times and ten times. It can distinguish the difference of arcing energy of diverter switch under different working conditions and has the measurability. Meanwhile, it verifies the effectiveness of this study, hoping to provide a theoretical basis for developing OLTC on-line contact detection system.

New Fault Tolerance Method for Open-Phase PMSM

Once the motor stator winding is opened, balanced three-phase windings turn into unbalanced two-phases windings. Unfortunately, by conducting Clarke and Park transformation for open-phase PMSM, complete decoupling of the torque and flux cannot achieve. To maintain the rated torque, the two remained phase currents have to be modified as sinusoidal currents with 60° phase difference (not 120°). As a result, the current controller design becomes complicated. In order to solve this problem, a new fault tolerance method for the open-phase PMSM is proposed in this paper. It is designed based on a novel reference frame transformation. Through proposed frame transformation, the modified sinusoidal time-varying current commands are turned into dc variables in the redefined synchronous rotating frame. Hence, the design of the open-phase PMSM current controller can be simplified. This method can deal with different phase open fault and different current control mode ( $i_{d}=0$ or $i_{d}\ne 0$ mode). In addition, considering that the neutral current ripple at usual switching frequencies may be very high, an optimal additional inductance that inserted into the neutral wire is designed. With the designed additional inductance, complete decoupling can be achieved. Experimental results confirm that the reliability and the performance of the PMSM drive can be improved distinctly with the proposed open-phase fault tolerance strategy.

Fault Analysis of Grid Connected MPPT Based Photovoltaic System

This paper presents the simulation model of a 158kW PV array followed by a boost converter, which boost up the output voltage of the PV array. Maximum power point tracking (MPPT) can effectively improve the solar energy conversion efficiency of PV array, in this paper perturb- and – observe (P&O) algorithm has been used to achieve this function. Grid connected PV system needs a three phase inverter for synchronization. The inverter control system modeling has been carried out in Matlab/Simulink 2010 environment with the aids of the proportional-integral controllers, sinusoidal vectored pulse width modulation technique and park transformation. Phase locked loop (PLL) is used to lock the grid frequency and phase. Finally different types of AC faults are created on the grid side and total harmonic distortion (THD) is calculated in each of the case.

Design and Realization of Controller for Static Switch in Microgrid Using Wavelet-Based TSK Reasoning

A microgrid may comprise several zones with local loads and distributed generation resources. If a fault occurs in a zone, then a static switch between the faulty and fault-free zones must be activated to detect/classify the faults and enable the breaker to open the circuit immediately. This paper presents a new method for designing a detection/classification module in a static switch using the Park Transform (PT), Multiresolution Analysis (MRA) and Takagi–Sugeno–Kang (TSK) fuzzy rules. Both wavelet coefficients/energies of the d -axis component, within 0.96–1.92 kHz, obtained by MRA and PT are employed to effectively detect and classify the fault types using the local fault signals near the static switch without a complicated communication system. The proposed TSK fuzzy rules, defined by the scenario data only, successfully classify the faults. The proposed method is verified by hardware-in-the-loop simulation using a real-time digital simulator and a realistic 5 kVA static switch. The proposed method is implemented in a Xilinx field-programmable gate array. Test results show that the proposed method is efficient in the real-time control environment of a microgrid.

The development of a diagnosis and risk assessment model for the industrial chain of industrial park and its verification through case study

Supplement chain diagnosis is the premise for the transformation of industrial park into more sustainable and circular-economy system. This paper proposed diagnosis model for the supplement chain which can help to identify the risk factors and calculate the risk coefficient. The Kalundborg industrial park and its experience, as well as the changes, in the times span from 1975 to 2000 were taken as a case study to verificate the proposed model, which showed that the risk coefficients calculated by this model can reflect the risk changes along with the formation of the industrial symbiotic network and provide some insights for the decision-making in the course of circular transformation.

An Exploration of Psychosocial Pathways of Parks' Effects on Health: A Qualitative Study.

Urban green space has been positively associated with psychological and physical health. However, the linkage between exposure to parks and health outcomes remains unclear. The current study examined the meanings that people assign to city parks, as a way to understand the pathways by which parks exert their effects on health. We conducted qualitative interviews with twenty culturally diverse residents in New York City. Thematic analysis was performed on the qualitative data. Results showed that all themes identified were related to parks fulfilling a basic human need for connection to (1) family, loved ones, and friends; (2) community and neighborhood; (3) self; and (4) nature. Based on these data, we proposed a human-centered framework for future research and interventions aimed at catalyzing parks as a vehicle to improve health and wellbeing. A human-centered approach emphasizes targeting the deep-seated needs and values of those we seek to engage and for whom health promotion and disease prevention efforts are designed. Our study shows that park transformations need to incorporate careful considerations of the human need for connection on multiple levels, so that park usage and its consequent health benefits may be optimized.

Control with Sliding Mode of a Five-Phase Series-Connected Two-asynchronous Motor Drive

In this paper, we study sliding mode control of series-connected five-phase two asynchronous machines supplied with a three levels inverter. After presentation of multiphase machines, we worked out the mathematical model of five phase asynchronous machine supplied with voltage inverter. Application of Park transformation reduces considerably the mathematical model of machine. After, we applied vector control and sliding mode control to the five-phase induction machine. After that, we study a multi-machine system, which comport five-phase two asynchronous machines supplied with a single voltage inverter.In the last, we had the sliding mode control of series-connected five-phase two asynchronous machines. Simulations are presented to show the effectiveness of the control strategy. We observe that an appropriate transposition of phase’s order permits an independent control of two machines.

Analysis of Tan-Sun Coordinate Transformation System for Three-Phase Unbalanced Power System

This paper mainly analyzes the characteristics of Tan-Sun coordinate transformation system, which is an extended version of Clarke coordinate transformation system suitable to be applied in three-phase unbalanced power system. The main purpose of Tan-Sun coordinate transformation system is to convert three-phase unbalanced alternating-current quantities into two orthogonal alternating-current quantities with the same amplitude, and these two quantities can be further converted into two direct-current quantities without second harmonic components through Park transformation. Tan-Sun coordinate transformation system can realize the direct-current decoupling of three-phase unbalanced currents, and the strict decoupling of the model of three-phase unbalanced power system, so the control methods developed for three-phase balanced power system can be migrated into three-phase unbalanced power system perfectly. In this paper, Tan-Sun and inverse Tan-Sun coordinate transformation matrices are illustrated at first. The essence of Tan-Sun coordinate transformation system is then presented, which can be divided into two coordinate transformation processes, and the corresponding coordinate transformation matrices are provided by detailed analysis. The relationship between Tan-Sun and Clarke coordinate transformation systems is also discussed. Finally, the simulation and experimental results are provided to validate the effectiveness of the adaptive Tan-Sun phase-locked loop method and the superiority of Tan-Sun coordinate transformation system.