FPGA-Based Permanent Magnet Synchronous Machine Emulator With SiC Power Amplifier

Europe’s electric power network is entering a period of extreme flux as we move to an era where it is dominated by non-linear, asynchronous generation such as wind power plants. The rapid rise of new technologies in this space has led to increasingly complex interactions within the power network that are difficult to cover through traditional test regimes. Existing facilities are not fully equipped to address these new system orientated challenges and while investing in new sites and facilities is one way forward, this is likely to be prohibitively expensive and runs the risk of only being applicable to niche applications. This work presents the first stage in an alternative approach which seeks to address these challenges through the pooling of existing resources. In this concept, geographically distributed test facilities are combined virtually to create new capabilities and perform complex system level validations. This can be done through a Geographically Distributed – Power Hardware in the Loop (GD-PHIL) setup. To achieve this, each site requires a PHIL setup allowing the Device Under Test (DUT) to interact in real time with a simulation. This work will present the outcome of the first step towards the development of such a network, developing and demonstrating the stable communications interfaces necessary to link geographically distributed real time simulators from two different manufacturers.

Testing power electronic converters of PMSM servo systems under realistic operating conditions usually comprise a costly and complicated process. Paper presents a power hardware in-the-loop (PHIL) emulation system to overcome the difficulties. The proposed PHIL emulation system consists of a real-time simulator to calculate the PMSM behaviors and a bidirectional AC/DC/AC converter to emulate the characteristics of machine interfaces and control power flow between the device under test (DUT) and the emulation system. Different loads and operating conditions can be readily simulated by changing the parameters of models in real-time simulator. Paper describes the concept of this system and presents the experimental results obtained using the prototype.

For the testing of 400-Hz inverters, a power hardware-in-the-loop (PHIL) platform is presented. However, the selections of power interface circuit parameters, such as filter of hardware interface (HI) and operating DC bus voltage of power amplifier (PA), remarkably affect the performance of the PHIL system. To solve this problem, an analytical and quantitative design method for power interface of PHIL is proposed. With the proposed design method, the relationships of the power interface circuit parameters and the PHIL system performances can be sufficiently taken into account and intuitively illustrated on a graph. Hence, the choices and optimizations of these parameters can be convenient and explicit. Moreover, a PHIL setup is built for testing a 400-Hz inverter to verify the effectiveness of the design method. Simulation and experimental results indicate that the setup achieves good performance.

Inverter testing using laboratory test benches with rotating machines can be bulky, complex, and maintenance intensive. One solution is to use machine emulator for laboratory testing of inverters. The emulator is controlled in such a way that currents and voltages at the terminals resemble a machine connected to a mechanical load. A machine emulator for a back-to-back power-hardware-in-the-loop (PHIL) test bench is proposed in this article. The PHIL test bench consists of two identical voltage source converters (VSCs) with three single-phase inductors as coupling network. The two VSCs are connected to the same direct current supply. One VSC acts as inverter under test (IUT), while the other is part of machine emulator. Aim of this article is to analyze the influence of coupling inductance on operating range of the emulator. An analytical method to dimension the coupling inductance is introduced and verified in experiments. The operating range of the emulator is also evaluated. The performance of the IUT when tested with an equivalent permanent magnet synchronous motor in simulations and that of a prototyped 60-kW rated machine emulator are compared. Sensitivity of emulator control on parameter estimation is discussed. The experimental results show good agreement with simulations in both steady-state and dynamic conditions.

In the absence of energy storage, photovoltaics (PV) also need to provide inertia support to the power electronic power system. Based on the DC bus voltage droop control to provide the inertia of the converter, two improved virtual inertia control strategies are proposed. From the perspective of DC bus voltage U dc and system virtual inertia coefficient H v under load disturbance, the advantages and disadvantages of three virtual inertia control strategies and the influence of control parameters on system inertia are analyzed. The conventional droop control is a full-band response load disturbance, and the inertia coefficient H dp increases with the droop coefficient $K$ dp increases, but the DC bus voltage cannot be restored to the initial set value. The improved low-pass filter control (ILPFC) only responds to the load disturbance in the low frequency band. In fact, a delay link is introduced on the basis of the conventional droop control to slow down the frequency response speed, and increasing the K1 or ω1 can also increase the system inertia effect. The improved high-pass filter control (IHPFC) only responds to load disturbances in the high frequency band, overcomes the problem that the conventional droop control cannot restore the DC bus voltage to the initial set value. Meanwhile, increasing Kh or decreasing ω $h$ can also improve the system inertia support. Finally, the effectiveness of the control strategy and the correctness of the analysis conclusion are verified by simulation.

This paper focuses on the stability issue of power hardware-in-the-loop (PHIL) simulation of inductor coupled systems. Main factors which influence the stability of this type system are analyzed and verified through experiments. A method to resolve the instability problem of the PHIL simulation without decreasing the simulation accuracy is also proposed. Moreover, a PHIL simulation of a gas engine cogeneration system with a matrix converter is introduced and the application of proposed method to improve stability is demonstrated.

Power electronic-based components (PECs) such as solid state transformers (SSTs), fault isolation devices (FIDs), power electronic-based converters, and motor drives provide highly useful features such as, load regulation, high power factor injection, and improved transient performance for power electronic-based distribution systems (PEDS). In contemporary power systems, which have high penetrations of renewable energy resources, as well as the inclusion of PECs. However, the drawback of including PECs in the system is that they can operate as negative impedances while connected to the constant power loads (CPLs) in the PEDS and CPLs are prone to small-signal instability due to their high power factor and constant-power nature in the system. Therefore, small-signal stability of the PEDS plays a prominent role in the systems analysis. In this paper, a new small-signal stability analysis method, based on d-q impedance measurement and generalised Nyquist criterion (GNC), is developed, and the stability of an SST is comprehensively investigated under various loading conditions and through power hardware-in-the-loop (PHIL) experimentation.

The Nyquist stability criterion is a graphical technique for determining the stability of a dynamical system. It relates the stability of a closed‐loop system to the open‐loop frequency response and open‐loop pole location. The Nyquist technique is limited to linear, time‐invariant (LTI) systems and has been widely used for designing and analyzing systems with feedback. A practical advantage of the technique is that it can be applied directly to measured frequency response data, due to which the technique is widely used in power electronics systems, where the complexity of a mathematical model would make its widespread use unfeasible. In its first part, this article guides through the fundamentals of the Nyquist stability criterion applied to feedback systems with SISO and MIMO representations. The generalized Nyquist criterion for MIMO systems is then discussed to illustrate its application to the stability assessment of three‐phase power electronics systems. In the second part, four representative cases are introduced to illustrate the applicability of Nyquist criterion–based stability analysis for power electronics systems: a dc‐dc converter, an HVDC system, a three‐phase converter, and a wind farm–HVDC grid integrated system. In the last section of this article, some advanced topics related to large‐scale power electronics systems are introduced. Inherent aspects that are essential for the proper use of these stability techniques are elaborated and discussed in detail, for instance, impedance transformation and modified sequence impedance or the system‐level analysis.

An approach to diagnostics of the operability of frequency-controlled electrical machines (EM) based on the analysis of the distribution of external electromagnetic radiation (EEMR) is proposed. Damage in the EM causes a change in the distribution of the EEMR. Spectral analysis of changes in the temporal and spatial harmonics of EEMR of frequency-controlled EM expands the field of diagnostic signs of EM damage, the possibility of determining the technical state of EM.

The influences of stator winding resistance and dc bus voltage variations on the efficiency maps of permanent magnet machines for motoring and generating operations are discussed. A large-scale design optimization algorithm is presented in which the efficiency requirements are independently treated for motoring and generating operations over the entire torque-speed plane. The separate treatment of efficiency is especially important in machines with large per-unit stator winding resistances, or in machine-drive systems with unregulated dc bus voltage, as is the case for low-voltage hybrid vehicle systems.

An innovative distributed secondary control technique for balanced current sharing and voltage regulation for an off-grid DC microgrid setup is presented in this research. The droop control scheme is conventionally used for current sharing amongst distributed sources (DSs) in a microgrid. However, this method has two major drawbacks. Firstly, due to the line resistance of each DS, the output voltage is different for each DS, and the output current-sharing property deteriorates. Secondly, the droop action increases the DC bus voltage variation. To address these drawbacks, a fuzzy-based distributed secondary controller is proposed. The proposed controller in each DS simultaneously ensures balanced current sharing and sustains DC bus voltage at the reference value by using a communication network to interact with one another. The required circumstance to guarantee the proposed controller’s stability is provided. The stability analysis is beneficial to inform the choice of control parameters. The real-time simulation outputs demonstrate the proposed control scheme’s robustness in achieving the control objectives under varying operating conditions.

In this paper, a system consisting of two cascaded dc-dc boost converters under sliding-mode control, working as loss free resistors, connected to a PV panel is studied. The modeling, simulation and design of the system are addressed. First, an ideal reduced-order sliding-mode dynamics model is derived from the full-order switched model taking into account the sliding constraints and stability analysis is carried out. It is shown that the cascade connection of boost-based loss free resistors can be a good solution for the impedance matching in PV systems with the standard 380 V dc bus voltage.

DC microgrids are well known as a proper solution to link different DC sources, such as photovoltaic panels and wind turbines, directly to DC loads. Along with their advantages, they suffer from an imbalance state of charge (SOC) in their energy storage units (ESUs), improper current‐sharing between ESUs, and DC bus voltage deviation. This study proposes a novel control strategy for DC microgrids, which not only balances ESUs SOC and shares current between ESUs proportional to their capacity but also, reduces DC bus voltage deviation significantly. In this way, the same droop curve is defined. Then, three virtual resistances are considered. The first one is set based on the lines resistance and ESUs capacity to share current among the ESUs properly. As the lines resistance changes affect the proportional current‐sharing, the second virtual resistance is intended to relieve this effect. The third one is suggested to balance the ESUs SOC. The small‐signal stability analysis is performed, which demonstrates that the proposed method has stability in all operating conditions. Simulation results in MATLAB/Simulink confirm that with the aid of the proposed control method, not only proper current‐sharing and ESUs SOC balancing are obtained, but also DC bus voltage deviation is effectively diminished.

Multiphase machines are AC machines characterized by a stator winding composed of a generic number n of phases. In today’s electric drive and power generation technology, multiphase machines play an important role for the benefits they bring compared to traditional three-phase ones (Levi, 2008; Levi et al., 2007). Such benefits have been widely highlighted by existing literature (Levi et al., 2007) and are mainly related to: an increased fault tolerance; higher power ratings achieved through power segmentation; enhanced performance in terms of efficiency and torque ripple. The use of multiphase machines is spreading both in small-power safety-critical applications as well as in very high-power industrial drives (Tessarolo et al., 2010), in electric-propulsion drives (Castellan et al., 2007) and power generation systems (Sulligoi et al., 2010). Regardless of whether they are used as motors or generators, multiphase electrical machines are almost always connected to power electronics systems (inverters for motors, rectifiers for generators), which interface them to the electric grid (Sulligoi et al., 2010; Castellan et al. 2008). Therefore, if the dynamic behaviour of a multiphase machine is to be predicted through simulations in the design and development stage, it is essential to do this by means of system-level simulations, where not only the electric machine is included, but also the power electronics and control systems that interact with it. Such a system-level simulation approach makes it difficult to use Finite-Element (FE) methods due to the complexity of the domain to be modelled and to the well-known computational heaviness of time-stepping FE simulations. Conversely, lumped-parameter models, to be implemented in the Matlab/Simulink environment, may provide designers with a powerful mean of analysis and investigation, provided that all the system components to be studied are modelled with an adequate level of accuracy and completeness. As concerns power electronics systems usually interfaced to multiphase machines, whether operating as motors or generators, the Matlab/Simulink environment offers wide and complete libraries where the designer can find reliable pre-defined blocks (for electronic switches, snubbers, diodes, etc.) to be used in building the application-related apparatus models. The same pertains to control and regulation blocks, which can be built up directly based on their transfer functions and logics. A possible criticality can be encountered when it comes to build the multiphase machine model. In fact, no predefined blocks are presently available in the Matlab/Simulink environment for this purpose. On the other side, building a dedicated user-defined machine

Analysis of new converter topologies, large converters, multi-converter systems, line commutated converters and electrical drive systems requires an appropriate global simulation tool. Because the dynamic model of AC machines is very complex due to the nonlinearities of the system, it is necessary to simulate the whole system containing an AC machine. A user friendly simulator must be able to handle complex systems as such electrical drives by dividing them in small interconnected sub-systems (converter-machine-regulator) assembled in a modular structure. The interconnection of these sub-systems must be done in a simple manner, without additional programming, using a graphic interface. The aim of this paper is to present a new interactive power electronic systems simulation package SIMUSEC "SIMUlation des Systemes Electrotechniques en Commutation", developed in the SIMULINK environment. This package permits simulation of power converters feeding passive loads or electrical machines either in open loop or in closed loop configurations. It also permits simulation of interaction between the converter-machine setups and between converters in a multiconverter system in order to study the conducted emissions. The built-in functions and tool boxes of SIMULINK facilitate the design and the analysis of high performance AC drive systems using this package.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>