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Real-time simulation is an important tool of validating the performance of the modular multilevel converter (MMC). By using the field programmable gates array (FPGA), MMC valves with hundreds of sub-modules and the large number of inputs and outputs can be simulated in real-time. In the traditional FPGA based real-time simulation, only the MMC valves are implemented on FPGA, while the rest parts including...
DC microgrid cluster serves for efficient operation and mutual power support between DC microgrids. Classification and comparison of DC microgrid cluster are carried out based on location and operation of the interlinking power route. Effect of parasitic resistance on voltage regulation in directly DC linked type of DC microgrid cluster is revealed. To compensate the effect and achieve controlled...
A series distributed generation (DG) units based islanding microgrid configuration and the corresponding power sharing method are proposed in this paper. Unlike a conventional islanding microgrid where parallel DG units are connected to the point of common coupling (PCC) to supply electricity to loads in a cooperative manner, this paper discusses the possibility of using series connected low voltage...
Industrial modular multilevel converter (MMC) controllers usually implement the sub-module (SM) capacitor voltage balance control (VBC) in field-programmable gate array (FPGA) boards. Conventional VBC methods need to sort out the capacitor voltages, where the sorting algorithm would become too complex to be accommodated in FPGA if the SM number is large. A sorting-less VBC optimized for FPGA implementation...
In order to enhance the redundancy and reliability for distributed generation, a grid-tied photovoltaic (PV) generation system based on series-connected module integrated inverters (SC-MIIs) is proposed in this paper. In the proposed system, each MII is interfaced with a PV panel with independent maximum power point tracking (MPPT) to harvest maximum solar energy. The outputs of MIIs are at AC-line...
The increase of grid-tied distributed generators (DGs) and nonlinear loads may generate harmful low order harmonics, polluting the grid and deteriorating the operation of other power electronics based loads and DGs. In order to improve the output current of the voltage source inverter (VSI) in grid-tied DG system, two methods are proposed in this paper to compensate the output harmonic under distorted...
Being the first five-terminal Modular Multilevel Converter (MMC)-based HVDC project in the world, the control and protection system must be validated under various operation modes as well as contingency at the factory acceptance test. This paper presents the configuration and performance of a hardware-in-the-loop (HIL) test platform that is based on a multi-rate real-time simulator using commercial-off-the-shelf...
This paper presents results from the KIC InnoEnergy project: Generic DC grid off-line and real-time simulation models and tools (Action 2.1, Subtask 2.1.1). The work reported here is focused on the development of a generic voltage source converter (VSC) model and its control schemes. Different test systems were designed and implemented in simulation tools and an experimental platform to verify the...
Despite the rapid development of VSC-HVDC technology, the practical experience to operate modular multi-level converter (MMC) has not yet been sufficiently accumulated. Real-time simulation is one of the most efficient approaches to verify the control and protection (C & P) scheme under various contingencies. With the increasing number of sub-modules, the accurate simulation of the MMC-HVDC becomes...
In this paper, the design of the 0°∼360° FET analog phase shifter is presented. By changing the gate voltages of the FET transistors, the output amplitudes of the four orthometric vector signals of the phase shifter can be independently adjusted. In this way, any phase shift over the range of 0° to 360° can be achieved. Due to the amplification characteristic of the FET transistors, the designed phase...
This paper presents the dynamic performance test of a complete control and protection system for a Multi-terminal MMC HVDC system using hardware-in-the-loop (HIL) simulation. A novel HIL bench with a cost-effective input and output interface between the control system under test and the real-time simulator is introduced. Two critical test cases, namely the start-up of the MMC connected to islanded...
In this paper a Nearest Level Control with open loop approach for modular multilevel converter (MMC) is proposed. By using open loop approach it is possible to suppress circulating currents without using feedback controllers. Moreover, with this method, both N+1 and 2N+1 levels (N=number of sub-modules) can be obtained at the output voltage. In addition, the voltage quality is improved and the total...
In recent years, embedding ancillary functions of distributed generation (DG) have drawn great attention due to the increasing penetration of renewable energy based DG such as photovoltaic, wind turbines and fuel cells. Among these ancillary functions, harmonics compensation is becoming more interesting and important with the growth of nonlinear loads in today's power distribution system. When controlled...
This paper proposes an improved power control approach to address the load sharing problems in islanded microgrids. The proposed method first estimates distributed generation (DG) unit feeder impedances through measuring low order point of common coupling (PCC) harmonic voltages and DG unit line harmonic currents. With the knowledge of feeder impedances, reactive power sharing performance can be enhanced...
Power transformer applied voltage test is one of the most effective and direct way to identify power transformer insulation strength and it is also an important part of preventive test. The methodology of diagnosing the transformer winding insulation defect using the transient voltage and current in voltage regulation process is put forward in this paper. In this methodology, the transient voltage...
This paper uses the grid-connected photovoltaic (PV) power plant electromechanical transient simulation model on FASTEST (Fast Analysis of Stability using the Extended equal area criterion and Simulation Technologies) to do the simulation of PV power plant integrated to the grid. The simulation includes the largest installed capacity of PV power plant and the response of PV power plant when solar...
This paper presents the control strategies and output (virtual) impedance design approach for parallel operated distributed generation (DG) units in a low voltage (LV) microgrid system. To achieve communicationless control among DG interfacing converters, virtual impedances are placed between the interfacing converter outputs and the grid to improve system stability and mitigate coupling between real...
In this paper, according to the characteristic of AC-excited variable speed constant frequency wind turbine generation, stator voltage orientation vector control strategy is adopted in double-fed induction generator (DFIG). Firstly, the paper studies the running characters of DFIG, and the principle of DFIG under no-load cutting-in condition. Then according to the mathematical model of DFIG under...
Power electronics technology is becoming an increasingly important aspect of today's power distribution system. It is the key interface to connect distributed energy resource (DER) to the utility and the local loads. With the increased penetration of power electronics based distributed generation (DG) systems, the power quality requirements are becoming more stringent. On the other hand, if controlled...
Based on the principle of the asymmetric control of the resistance welding machine, this paper adopted embedded system as the controlling core and carried out the simulation experiment to verify this principle. On the basis of the applying circuit of transformer resistance experiments, the transformer primary voltage experiment has been priority carried out. The results indicate that the primary equivalent...
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