Active Voltage Control Research Articles

Suppression of residual amplitude modulation of ADP electro-optical modulator in Pound-Drever-Hall laser frequency stabilization

We report a simple and robust approach to reduce the residual amplitude modulation (RAM) by employing an ammonium dihydrogen phosphate (ADP) crystal to provide optical phase modulation in the Pound-Drever-Hall frequency stabilization system. The birefringence-related amplitude modulation can be suppressed due to the insensitivity to the ambient temperature of the crystal. The proposed RAM can be significantly reduced to 20 ppm level, which is comparable with the electro-optic modulator (EOM) under critical active temperature and bias voltage control. The RAM-induced frequency instability is below 2 × 10−17 for integration times from 1 to 1000 s, which is lower than the fundamental thermal noise limit of the reference cavity and meets the requirements for realization of the ultra-stable laser and high-precision measurement.

A Loss Redistribution Technique for the Power Devices in the NPC Converter by PWM Zero-Sequence Injection

The neutral-point-clamped (NPC) converter suffers from uneven power loss distribution among semiconductor devices under the conventional modulation technique, which degrades its reliability. In this article, a zero-sequence voltage injection technique is proposed to address this issue. Its effectiveness of power loss redistribution is not restricted by operation conditions, and no extra devices are required. Its performance in reducing the power loss of the most stressed device in the NPC converter is verified by simulation and experiment tests under different power factors. A compatible active neutral-point voltage control strategy is designed and validated by laboratory tests. The output current quality and common-mode voltage are discussed as well.

A Mean-Field Voltage Control Approach for Active Distribution Networks With Uncertainties

A model-free distributed control scheme that implements active voltage control in low voltage distribution network (LVDN) is proposed. By solving an individual Hamilton-Jacobi-Bellman-Flemming function with public information, users can compute a good approximation to their optimal control trajectory and take uncertainties into account in a distributed manner. A detailed mathematical framework is given, accompanied by a discussion on the different entries of uncertainties. The proposed control scheme uses a broadcast signal to indicate the probability distribution in mean field theory, and to streamline the demand on Fokker-Planck-Kolmogorov PDE or Mc-Kean Vlasov SDE, which relieves the computational burden. A realistic semiurban distribution network is modified as the study case, with a benchmark of centralized ACOPF to study the performance of the proposed approach. Moreover, two special cases including communication latency and packet loss are given as well, in order to test the robustness of the proposed approach. The results prove that the proposed approach is able to deliver good approximation to the optimal control with uncertainty in a model-free and distributed manner.

Elimination of the Impact Produced by DG Units on the Voltage Profile of Distribution Networks

In this paper, an alternative strategy for real-time control of active distribution network voltage is developed, not by controlling the bus voltage as in the various centralized, decentralized, and local approaches presented in literature but rather by only eliminating the impact produced by active and reactive power of distributed generation (DG) units on the voltage of all network nodes and keeping the traditional voltage control systems dealing with the same constraints of passive systems. In literature, voltage deterioration introduced by DGs has been reported as one of the main obstacles for the interconnection of large amounts of DG units to the existing networks. In this paper, the novel control strategy is based on a sensitivity formula developed to calculate the compensation needed for additional distributed flexible AC transmission system (D-FACTS) devices to push and pull the exact reactive power and to eliminate the impact produced by DGs on the network voltage profile. The criteria of the allocation of the var devices and the required network reinforcement are developed in this paper, considering all possible topology structures, and an innovative codification method is introduced to reduce the needed computation time and communication data to actualize the sensitivity coefficients and get the proposed control approach flexible with network topology reconfiguration. The risk of the conflict of the proposed control system with the traditional voltage equipment is reduced due to the fast capability of D-FACTS devices to regulate their reactive power in finer granularity. A case study of two meshed IEEE 15-bus feeders is introduced to compare the voltage behavior with and without the presence of DG units and to evaluate the total system losses. The proposed method could be used for the interconnection of the first generation units in emerging networks, which does not yet have an active voltage control strategy, as it could be used for DG units not able to be connected to existing centralized control systems and it could also be used as the principal voltage control strategy, with the extension for several neighboring units and the preservation of the traditional voltage control systems.

Electrical energy storage systems for increasing technical and economical characteristics of gas engine power plants

Developing of new technologies such as electrical energy storage systems (EESS) opens new ways to increasing efficiency, decreasing exhaust waste and fuel consumption in traditional fossil fuels power station. This paper contains actual testing results of electrical energy storage system based on lithium-ion technology working with gas engine generator and altering load power. EESS parameters: rated power 100 kVA, rated capacity 153 kWh. As is known, gas generators are sensitive to changes in load power, obtained results show the effectiveness of the usage EESS to supply sustainability of generators in high amplitude and frequency altering load power environment. These results achieved through the ability of the developed converter and control strategy to compensate rapid deviations of the load power. In additional, in control system realized others common functionality: active power limitation, voltage and frequency control, reactive power control, power factor control and others. With the usage EESS, the nominal power of plane station should be lower than without EESS.

Low Frequency Harmonics Reduction Discontinuous PWM Strategy With Active Neutral Point Voltage Control for Neutral Point Clamped Three-Level Inverter

The traditional discontinuous pulse width modulation (DPWM) strategy is very suitable for reducing the switching losses of three-level inverter (TLI). However, large neutral point voltage (NPV) fluctuation is usually caused, which results in low frequency harmonics (LFHs) in the output line voltage. Therefore, a DPWM modulation strategy that can suppress LFHs is presented in this paper, and it is recorded as low frequency harmonic reduction DPWM (LFHRDPWM). The proposed LFHRDPWM can be seen as an improvement of traditional DPWM, which modifies the duty ratios according to voltages of the two DC-link capacitors. For LFHRDPWM, due to the suppressed LFHs, the self-balancing ability of NPV is thus lost, and gradually increased DC offset on NPV is caused. To overcome that, an active neutral point voltage control (ANPVC) method is also proposed. The proposed methods not only can achieve switching loss (SL) reduction almost as the same as traditional DPWM strategy, but also can realize NPV control and LFHs reduction. The effectiveness of the proposed method is verified by experiments.

Active and Reactive Voltage Control for DFIG Interface

Active and Reactive Voltage Control for DFIG Interface

Active Disturbance Rejection Voltage Control of a Floating Interleaved DC–DC Boost Converter With Switch Fault Consideration

To enhance the robustness and to deal with the switch fault uncertainty of a floating interleaved dc–dc boost converter (FIBC), an adaptive active disturbance rejection control (ADRC) is proposed in this paper. In particular, the controller parameter b 0 is adapted by obtaining approximately the system input control gain b in real time, based on the output duty cycles via digital filters. Compared with the conventional ADRC, the performance of the proposed controller is significantly improved, without the need of extra sensors. Moreover, the influence of the controller parameters on the system dynamical performance is analyzed theoretically, providing a practical guideline for controller tuning. The simulation and experimental results validate the effectiveness and the robustness of the proposed controller.

Active Voltage Control for DFIG-Based Wind Farm Integrated Power System by Coordinating Active and Reactive Powers Under Wind Speed Variations

Large-scale wind farms are generally integrated by long-distance transmissions, but power grids cannot sufficiently support the access point voltage of these wind farms. The access point voltage undergoes a stability problem under wind speed variations. However, the reactive power compensation device cannot reconcile the requirements of response speed and compensation capacity. Despite their fast power decoupling control, the reactive power capability of doubly fed induction generators is restricted by active power output. To satisfy the reactive power demand of system under wind speed variations, coordinating the reactive power capability and active power output of wind farm is the key solution, based on which a novel active control idea is proposed. The reactive power capability of wind farm and the reactive power demand of system are both studied, and the controllable conditions of access point voltage are analyzed. Active voltage control strategies, including active adjustment of reactive power reference, active speed control, and active pitch angle intervention according to wind speed ranges, are proposed. In the simulation, the method is verified to adequately consider the reactive power demand, and excavate the wind farm reactive power capability. The method also effectively suppresses the change of grid voltage under wind speed variations.

A Novel Virtual Space Vector Modulation With Reduced Common-Mode Voltage and Eliminated Neutral Point Voltage Oscillation for Neutral Point Clamped Three-Level Inverter

This paper briefly reviews the common-mode voltage (CMV) and neutral point (NP) voltage for neutral point clamped three-level inverter (NPC TLI). Then, the space vector pulsewidth modulation (SVPWM) and traditional virtual SVPWM (VSVPWM) are discussed in terms of these two issues, revealing the drawbacks in reducing CMV or eliminating NP voltage oscillation. A novel virtual space vector modulation, named as RCMV_VSVPWM, is proposed in this paper to reduce CMV and eliminate NP voltage oscillation for NPC TLI. By selecting vectors with lower CMVs, a set of novel virtual voltage vectors are generated. The highlight of the method is zero average NP current in one control cycle and lower CMV. Furthermore, the active NP voltage control suitable for RCMV_VSVPWM is presented and evaluated. The corresponding experimental results are given, which are well-consistent with theoretical analysis.

A Simple Closed-Loop Active Gate Voltage Driver for Controlling diC/dt and dvCE/dt in IGBTs

The increase of the switching speed in power semiconductors leads to converters with better efficiency and high power density. On the other hand, fast switching generates some consequences like overshoots and higher switching transient, which provoke electromagnetic interference (EMI). This paper proposes a new closed-loop gate driver to improve switching trajectory in insulated gate bipolar transistors (IGBTs) at the hard switching condition. The proposed closed-loop gate driver is based on an active gate voltage control method, which deals with emitter voltage (VEe) for controlling diC/dt and gets feedback from the output voltage (vCE) in order to control dvCE/dt. The sampled voltage signals modify the profile of the applied gate voltage (vgg). As a result, the desired gate driver (GD) improves the switching transients with minimum switching loss. The operation principle and implementation of the controller in the GD are thoroughly described. It can be observed that the new GD controls both dvCE/dt and diC/dt accurately independent of the variable parameters. The new control method is verified by experimental results. As a current issue, the known trade-off between switching losses and EMI is improved by this simple and effective control method.

Discontinuous PWM Strategy for Neutral Point Clamped Three-Level Inverter to Achieve Multiple Control Objectives

In order to reduce switching loss of neutral-point clamped (NPC) three-level inverter (TLI), a switching loss minimized discontinuous PWM (SLMDPWM) strategy is proposed firstly. There are DC offset and AC ripple on the neutral-point (NP) voltage when SLMDPWM is used, which causes an appearance of low frequency harmonics (LFHs) in the output voltage. Aiming at this drawback, reduced LFHs (RLFHs) method is then proposed. While using RLFHs, the self-equilibrium ability of NP voltage is thus lost. So, active neutral-point voltage control (ANPVC) is also proposed. The performances of NPC TLI with the proposed DPWM and other DPWMs are compared by simulation and experimental results. The results show that switching loss, LFHs can be reduced significantly and the NP voltage can be controlled within an allowable range. Therefore, the multiple control objectives of reduced switching loss, no LFHs and allowable NP voltage are achieved.

A Carrier-Based PWM Strategy Providing Neutral-Point Voltage Oscillation Elimination for Multi-Phase Neutral Point Clamped 3-Level Inverter

General pulse width modulation (PWM) model for multi-phase neutral point (NP) clamped (NPC) 3-level inverter (3LI) is described. A novel PWM strategy for $N$ -phase NPC 3LI with unconditional NP voltage balance is proposed as well as its carrier-based realization, in which PWM sequences are generated by comparing a single carrier wave with double modulation waves. The proposed PWM strategy is consistent with the principle of virtual space vector PWM (VSVPWM). However, the mechanism of NP voltage balance under the proposed PWM strategy is based on precisely calculating and executing level 1 action time of each phase, which may be influenced by some non-ideal factors. To avoid that, an active NP voltage control for the proposed PWM strategy is put forward. Then 3-phase and 5-phase NPC 3LIs are built as examples to verify the correctness of the proposed PWM strategy. Finally, the experimental results indicate that the proposed PWM strategy has better NP voltage control abilities.

Active Hybrid Solid State Transformer Based on Multi-Level Converter Using SiC MOSFET

As the types of loads have been diversified and demand has increased, conventional distribution transformers are difficult to maintain the constant voltage against voltage drop along with distance, grid voltage swell/sag, and various loads. Also, it is hard to control the power flow when connecting renewable energy sources. Active hybrid solid state transformer (AHSST) is application to keep the voltage and power quality. AHSST is a system that combines conventional distribution transformer and converter. Accordingly, it can be applied directly to distribution infrastructure and it has both the advantages of solid state transformer (SST) and conventional transformer. AHSST is capable of active voltage and current control and power factor control. It has a simpler structure than SST and it can perform the same performance with the lower rating converter. This paper presents two stage AHSST system based on multi-level converter. The converter is composed of the back-to-back converter using silicon carbide (SiC) metal-oxide semiconductor field effect transistor (MOSFET). Proposed system has a wider voltage and power flow control range, lower filter size, and simpler control sequence than existing AHSST systems. The performance of the proposed system was verified by prototype system experiments.

A Carrier-Based Virtual Space Vector Modulation With Active Neutral-Point Voltage Control for a Neutral-Point-Clamped Three-Level Inverter

Virtual space vector pulsewidth modulation (VSVPWM) for the neutral-point (NP)-clamped three-level inverter is briefly reviewed in this paper, as well as its carrier-based realization. The carrier-based VSVPWM (CB_VSVPWM) is featured with dual modulation waves and a single carrier. Although CB_VSVPWM can make NP voltage unfluctuating in theory, it does not have the NP voltage recovery ability. In practice, due to the effect of nonidea factor effects, NP voltage may shift. Thus, active NP voltage control (ANPVC) is necessary. To achieve that, three ANPVC approaches are proposed based on CB_VSVPWM in this paper. The NP voltage control ability of CB_VSVPWM with ANPVC is analyzed. Finally, comprehensive experiments are carried out to verify the feasibility of the proposed method.

Coordinated Control for Large-Scale Wind Farms with LCC-HVDC Integration

Wind farms (WFs) controlled with conventional vector control (VC) algorithms cannot be directly integrated to the power grid through line commutated rectifier (LCR)-based high voltage direct current (HVDC) transmission due to the lack of voltage support at its sending-end bus. This paper proposes a novel coordinated control scheme for WFs with LCC-HVDC integration. The scheme comprises two key sub-control loops, referred to as the reactive power-based frequency (Q-f) control loop and the active power-based voltage (P-V) control loop, respectively. The Q-f control, applied to the voltage sources inverters in the WFs, maintains the system frequency and compensates the reactive power for the LCR of HVDC, whereas the P-V control, applied to the LCR, maintains the sending-end bus voltage and achieves the active power balance of the system. Phase-plane analysis and small-signal analysis are performed to evaluate the stability of the system and facilitate the controller parameter design. Simulations performed on PSCAD/EMTDC verify the proposed control scheme.

Distributed PLL-Based Control of Offshore Wind Turbines Connected With Diode-Rectifier-Based HVDC Systems

Distributed phase-locked loop-based frequency control is proposed in this paper for offshore wind turbine converters connected with diode-rectifier-based high-voltage-direct-current systems. The proposed control enables a large number of wind turbines to work autonomously to contribute to the offshore ac frequency and voltage regulation. The proposed control also provides automatic synchronization of the offline wind turbines to the offshore ac grid. Stability of the proposed frequency control is analyzed using the root locus method. Moreover, active dc voltage control of the onshore modular multilevel converter (MMC) is proposed to ride-through an onshore ac fault, where the onshore MMC converter quickly increases the dc voltage by adding additional submodules in each phase, in order to rapidly reduce wind farm active power generation so as to achieve quick active power rebalance between the offshore and onshore sides. Thus, the overvoltage of the submodule capacitor is alleviated during the onshore fault, reducing the possibility of system disconnection. Simulation results in PSCAD verify the proposed control strategy during startup, synchronization, and under onshore and offshore fault conditions.

RETRACTED ARTICLE: Internet of Things Based Industrial Automation Using Brushless DC Motor Application with Resilient Directed Neural Network Control FED Virtual Z-Source Multilevel Inverter Topology

Internet of Things (IoT) is a high-speed communication technology which has carnal substances or devices entrenched with sensors, system connectivity, which allows to receive and interchange data. Industrial Monitoring and Control is required to assemble all the material information, statistics, and data related to the various industrial processes, motors, machines and devices employed in industrial premises. The technological improvements, remote control and monitoring via communication techniques such as wireless sensor network techniques have been widely used in Industries. Competitive advantages over AC motors make for DC motors to replace other electrical engines in applications stretching from high-speed automation to electric motorbikes. BLDC drives are very popular in many industries, at present automation are added standard, Virtual Z-source multilevel is a respectable optimal that can boost the output voltage of the drive. A novel soft computing based Resilient Directed Neural network (RDNN) found Virtual Z-source multilevel inverter, for BLDC motor drive control to make the system balanced when the load is unbalanced and to reduce the electrical torque pulsation. In this work, the utilization of the RDNN to tackle the reduced harmonics issue in VZS-MLI converters is proposed. This strategy permits active voltage control of the crucial and besides concealment of a particular set of harmonics. The performance is evaluated in various emphasis levels of the different control models. The sensors monitor the technical motor parameters like greatest rise and fall time, topmost overextend and inaccuracy value of load current and voltage in BLDC machine. Then the measured values are sent to the processing unit, which will analyze and display the parameters, where the processing unit also communicates with Gateway module to send information to cloud database for remote monitoring. The system also presents the Automatic and manual control methods to stop or start the BLDC machine to avoid system failures.

Development of 170 GHz, 1 MW gyrotron with high-order TE31,11 mode oscillation for ITER EC system

A TE31,11 mode gyrotron has being developed to improve the output power for the ITER electron cyclotron (EC) system. Strong mode competition having counter-rotating modes in both the high and/or low field sides is, in general, the typical issue for high order mode oscillations. Active anode voltage control and beam radius control were introduced to overcome this issue and obtain stable 1 MW oscillation. The TE31,11 mode was oscillated in a hard-self excitation region and the efficiency was improved up to 50%. Long pulse operation of output power of 1 MW with total efficiency of 46% for 230 s was also performed. Oscillations of over–1 MW power of 1.1 MW and 1.2 MW for 2 s pulse were achieved.

Physical Investigation Into Effective Voltage Balancing by Temporary Clamp Technique for the Series Connection of IGBTs

The series connection of IGBTs is essential for high-voltage applications where fast switching performances need to be maintained. However, unbalanced voltage sharing is a major resistance to the converter application of this structure. There are a number of causes leading to voltage unbalance, such as different signal delays, parasitic parameters, tail currents, and so on. A temporary clamp scheme performed by active voltage control (AVC) has been proven to be effective in solving the unbalanced voltage-sharing issue. However, the basic physics has not been investigated. In this paper, the physical principle of voltage unbalance within IGBTs series operation is discussed. The carrier storage region differences are concluded to be the intrinsic cause of unbalanced voltage sharing. By using an accurate Fourier-series-based IGBT simulation model with appropriate assumptions, a physical explanation for temporary clamp is provided in detail. At the end of the tail current period when the excess carrier concentration becomes close to the intrinsic doping density, the temporary clamp is able to achieve satisfactory equal voltage sharing.