Review on grid-forming converter control methods in high-proportion renewable energy power systems

Grid-forming(GFM)converters can provide inertia support for power grids through control technology,stabilize voltage and frequency,and improve system stability,unlike traditional grid-following(GFL)converters.Therefore,in future“double high”power systems,research on the control technology of GFM converters will become an urgent demand.In this paper,we first introduce the basic principle of GFM control and then present five currently used control strategies for GFM converters:droop control,power synchronization control(PSC),virtual synchronous machine control(VSM),direct power control(DPC),and virtual oscillator control(VOC).These five strategies can independently establish voltage phasors to provide inertia to the system.Among these,droop control is the most widely used strategy.PSC and VSM are strategies that simulate the mechanical characteristics of synchronous generators;thus,they are more accurate than droop control.DPC regulates the active power and reactive power directly,with no inner current controller,and VOC is a novel method under study using an oscillator circuit to realize synchronization.Finally,we highlight key technologies and research directions to be addressed in the future.

Vehicles PEMFC Power System Mathematical Model for Integrated Design

In this paper, the mathematical dynamical model of a PEMFC （proton exchange membrane fuel cells） stack, integrated with an automotive synchronous electrical power drive, developed in Matlab environment, is shown. Lots of simulations have been executed in many load conditions. In this paper, the load conditions regarding an electrical vehicle for disabled people is reported. The innovation in this field concerns the integration, in the PEMFC stack mathematical dynamic model, of a synchronous electrical power drive for automotive purposes. Goal of the simulator design has been to create an useful tool which is able to evaluate the behaviour of the whole system so as to optimize the components choose. As regards the simulations with a synchronous electrical power drive, the complete mathematical model allows to evaluate the PEMFC stack performances and electrochemical efficiency.

A Low Power Non-Volatile LR-WPAN Baseband Processor with Wake-Up Identification Receiver

The paper proposes a low power non-volatile baseband processor with wake-up identification(WUI) receiver for LR-WPAN transceiver.It consists of WUI receiver,main receiver,transmitter,non-volatile memory(NVM) and power management module.The main receiver adopts a unified simplified synchronization method and channel codec with proactive Reed-Solomon Bypass technique,which increases the robustness and energy efficiency of receiver.The WUI receiver specifies the communication node and wakes up the transceiver to reduce average power consumption of the transceiver.The embedded NVM can backup/restore the states information of processor that avoids the loss of the state information caused by power failure and reduces the unnecessary power of repetitive computation when the processor is waked up from power down mode.The baseband processor is designed and verified on a FPGA board.The simulated power consumption of processor is 5.1uW for transmitting and 28.2μW for receiving.The WUI receiver technique reduces the average power consumption of transceiver remarkably.If the transceiver operates 30 seconds in every 15 minutes,the average power consumption of the transceiver can be reduced by two orders of magnitude.The NVM avoids the loss of the state information caused by power failure and energy waste caused by repetitive computation.

同步电动机的励磁调节在工业生产中的应用

详细论述了调步同步电动机励磁电流而使功率因数提高的原理和意义。

Power Synchronization Compensation Strategy Based on Second-order Compensation Links for Voltage-controlled Inverters in Microgrids

A second-order compensation link is adopted to control voltage-controlled inverters(VCIs) in microgrid systems to enhance the performance of the power synchronization process of the inverter. The second-order compensation link is classified as both a real pole compensator(RPC) and a complex pole compensator(CPC) according to the pole position. Given a model for the VCI power output, the design process for the second-order compensation link, which is equipped with an RPC and a CPC, is detailed. Moreover, the frequency-domain compensation effects of the RPC and CPC are analyzed using the root locus and Bode diagrams of the system before and after compensation. Finally, the compensation effects of the two types of second-order compensators are compared with the commonly used high-pass filter using MATLAB/Simulink, which verifies the RPC and CPC strategies. Simulation results show that the two types of compensators designed in this study can effectively increase the system cutting frequency and improve the phase margin in the frequency domain while accelerating the power synchronization process, simultaneously making it smoother and reducing overshoot in the time domain. The RPC has better gain robustness, whereas the CPC has better time constant robustness. By implementing an RPC or a CPC, the dynamic time of the power synchronization compensation strategy is reduced within 0.5 s, and the overshoot is reduced within 10% in the experiments with two inverters.

Synchronous Construction and Operation of Coal Mine and Power Plant in Mining Area

In accordance with the experience withSynchronous construction of coal mine andpower plant in Yongxia mining area, thispaper discusses the existing issues regardingmine mouth power plant including capital,power grid connection, electricity price for gridconnection, installed capacity generation setselection as well as self- protection of coalindustry. It is regarded that under marketeconomy as long as the benefits of the threesectors of coal, electricity and the local arecomprehensively considered, a suitable waycan be arrived for conl industry to operate electricity business.

Active Power Reserve Photovoltaic Virtual Synchronization Control Technology

The photovoltaic virtual synchronous generator(PV-VSG)solves the problem of lack of inertia in the PV power-generation system.The existing PV plants without energy storage are required to participate in the power grid’s frequency modulation(FM),but existing PV-VSGs with energy storage have high requirements for coordinated control.Therefore,the active power reserve PV-VSG(APR-PV-VSG)is studied.Based on the different methods to obtain the maximum power point(MPP),the peer-to-peer and master-slave APR-PV-VSG strategies are proposed.The PV inverters are deviated from the MPP to reserve active power,which is used as the virtual inertia and primary FM power.These methods equip the PV power station with FM capability.The effectiveness of the proposed control strategies is verified by simulation results.

Grid-connected Converters with Virtual Electromechanical Characteristics:Experimental Verification

Grid-connected power converters,which are frequently used to link renewable generation plants with the grid,are required to provide a better functionality for large scale integration of renewables.They are expected to be gridfriendly,or even grid-supportive,instead of simply grid-feeding or grid-demanding.This paper designs a synchronous power controller for grid-connected converters in detail,emulating the electromechanical characteristics of synchronous machines and improving even its actual performance,as it is based on a virtual approach.Based on this design,the grid-interfacing units are capable of showing inertia,damping,and droop characteristics as synchronous machines and presenting thus a grid-supporting behavior.The detailed control design and experimental validation on a 10 kW laboratory setup acts as the main contribution of this paper,compared with the existing studies on generator emulation controls.