Operation Zone Analysis of the Voltage Source Converter Based on the Influence of Different Grid Strengths

With the increasing penetration of renewable energy into the power system, the voltage source converter (VSC) for integrating renewable energy has become the most common device in the electric network. However, the operating stability of the VSC is strongly dependent on its operating control strategy, which is also highly related to the strength of the AC system. Choosing the control strategy of VSC for different strengths of AC systems becomes an essential issue for maintaining the symmetry between high proportion of renewable energy integration and stable operation of AC system. In order to obtain the operation zones of the control strategies of the VSC under different strengths of AC system, in this paper, the two common VSC control strategies, vector current control (VCC) and power synchronization control (PSC), are compared. Firstly, the principle of VCC and PSC are introduced. Then, based on the short circuit ratio (SCR) and the power limit calculation under steady-state conditions of the VSC, the operation zones of the vector current control and power synchronization control are proposed. Finally, a medium voltage modular multilevel converter (MMC) system was built in PSCAD/EMTDC and the proposed operation zones of the VCC and PSC were tested by changing the SCR of the modified IEEE 33 bus system and analyzed via the critical short circuit ratio (CSCR) analysis, the small-signal stability analysis, and transient stability analysis. The results indicate that, as the SCR decreases, the VSC based on VCC is gradually worked into unstable conditions, while the stability of VSC based on PSC gradually increases. The analysis results provide a criterion for the converter operation strategy change that could significantly improve the operating stability of the VSC in the power system and realize the symmetry of the stability of the converter and the change of the strength of the AC system.

A nonlinear piezoelectric shunt absorber with 2:1 internal resonance: experimental proof of concept

An experimental proof of concept of a new semi-passive nonlinear piezoelectric shunt absorber, introduced theoretically in a companion article, is presented in this work. This absorber is obtained by connecting, through a piezoelectric transducer, an elastic structure to a resonant circuit that includes a quadratic nonlinearity. This nonlinearity is obtained by including in the circuit a voltage source proportional to the square of the voltage across the piezoelectric transducer, thanks to an analog multiplier circuit. Then, by tuning the electric resonance of the circuit to half the value of one of the resonances of the elastic structure, a two-to-one internal resonance is at hand. As a result, a strong energy transfer occurs from the mechanical mode to be attenuated to the electrical mode of the shunt, leading to two essential features: a nonlinear antiresonance in place of the mechanical resonance and an amplitude saturation. Namely, the amplitude of the elastic structure oscillations at the antiresonance becomes, above a given threshold, independent of the forcing level, contrary to a classical linear resonant shunt. This paper presents the experimental setup, the designed nonlinear shunt circuit and the main experimental results.

Multi-Terminal DC Grid with Wind Power Injection

With the development of offshore wind generation, the interest in cross-country connections is also increasing, which requires models to study their complex static and dynamic behaviors. This paper presents the mathematical modeling of an offshore wind farm integrated into a cross-country HVDC network forming a multi-terminal high-voltage DC (MTDC) network. The voltage source converter models were added with the control of active power, reactive power, frequency, and DC link voltages at appropriate nodes in the MTDC, resembling a typical cross-country multi-terminal type of HVDC scenario. The mathematical model for the network together with the controllers were simulated in MATLABTM and experimentally verified using a real-time digital simulator hardware setup. The resulting static and dynamic responses from the hardware setup agreed well with those from simulations of the developed models.

An Interaction Less Duo Control Strategy for Bi-polar Voltage Source Converter in Renewables Integrated Multi-Terminal HVDC (MTDC) Grids

The PVF or PV²Fdouble droop control is commended for its ability to regulate both the dc voltage and frequency in a decentralized approach. However, a convincing response is not achieved due to an interaction between the droop characteristics of dc voltage and frequency. This interaction affects the dc voltage and frequency support of the AC system surrounded Multi-Terminal HVDC (AC-MTDC) grid. To overcome this effect, a Duo control strategy is proposed in this paper, which takes advantage of a Bi-polar Voltage Source Converter (B-VSC) topology in the MTDC grid. The virtue of proposed control technique is emphasized by comparing it with the existing $ PV²F double droop control along with three case studies and two test systems. The validation of interaction less Duo control strategy is carried out on five terminal CIGRE DC grid benchmark model integrated into two area power system (AC-MTDC grid-1) and New England IEEE 39 bus system (AC-MTDC grid-2). These test systems are simulated in PSCAD/EMTDC software.

An Interaction Less Duo Control Strategy for Bi-polar Voltage Source Converter in Renewables Integrated Multi-Terminal HVDC (MTDC) Grids

The PVF or PV²Fdouble droop control is commended for its ability to regulate both the dc voltage and frequency in a decentralized approach. However, a convincing response is not achieved due to an interaction between the droop characteristics of dc voltage and frequency. This interaction affects the dc voltage and frequency support of the AC system surrounded Multi-Terminal HVDC (AC-MTDC) grid. To overcome this effect, a Duo control strategy is proposed in this paper, which takes advantage of a Bi-polar Voltage Source Converter (B-VSC) topology in the MTDC grid. The virtue of proposed control technique is emphasized by comparing it with the existing $ PV²F double droop control along with three case studies and two test systems. The validation of interaction less Duo control strategy is carried out on five terminal CIGRE DC grid benchmark model integrated into two area power system (AC-MTDC grid-1) and New England IEEE 39 bus system (AC-MTDC grid-2). These test systems are simulated in PSCAD/EMTDC software.

Development and testing of a light dimming control using arduino uno

Increasing population and human needs have an impact on increasing the need for electrical energy. One of them is for lighting needs. Therefore, it is necessary to save the lighting system so that energy consumption is minimum and the need for lighting is optimal, by controlling light dimming. This paper presents an implementation and testing of a dimming light control using an Arduino Uno microcontroller. The circuit used a 12-volt power supply, as a voltage source, to increase to 42 volts, to meet a lamp voltage, through a dc-dc converter. After obtaining the maximum voltage, a MOSFET cut off the voltage according to the desired light or performance level. The duty cycle was directly proportional to the output voltage, using a PWM coding to get the necessary light intensity. Some testing was conducted, including the measurement point shifting to the side. The testing results show that PMW and LDR decreased as the duty cycle increased. Nevertheless, both decreasing are different, the PWM decreased linearly with a gradient of -2.55 and the LDR decreased hyperbolically. While, the illuminance, current, and power rose as the duty cycle increased. The illuminance increased, tent to be saturated, as the power increased. However, the illuminance was reduced as the PWM and LDR increased. The illuminance decreased slightly as the measurement points shifted to the side.

Study on Stability of Hand-in-hand Structure of Multi-terminal DC Hydrogen Production System

Multi-terminal DC (MTDC) hydrogen production systems are becoming one of the important forms of power distribution systems with the increasing growth of distributed renewable energy sources (such as PV and wind turbines), energy storage devices, and DC loads. To explore the key factors in stability analysis, the circuit diagram of MTDC hydrogen production system in hand-in-hand structure composed of voltage source converters (VSCs), DC lines, renewable energy and DC hydrogen production load was established in this paper. The overall state space model of the system was put forward, taking the master-slave converter control strategy into consideration. Then, the small-signal stability analysis of the MTDC hydrogen production system was carried out by comparing and analyzing the moving trajectories of the dominant eigenvalues in different system parameters. The key factor affecting the stability of the system such as DC capacitance of the converter and the electrolyzer power in the DC bus are determined. On this basis, a simulation model of the low-voltage MTDC hydrogen production system was built based on MATLAB/Simulink to verify the correctness of the theoretical analysis.