Overvoltage Problems Research Articles

Prescribed finite-time tracking control with input buffer for a manipulator system

The prescribed finite-time trajectory tracking control problem with input buffer is investigated for a linkage manipulator system. The backstepping method is used to design the prescribed finite-time trajectory tracking controller. A new prescribed finite-time performance function is proposed, which can more easily regulate control performance. With the help of this performance function, a constraint control law is designed for the tracking error, and a better transient performance than the existing prescribed finite-time performance function can be obtained under the same parameter conditions for the trajectory tracking process of the manipulator system. At the same time, a control input buffer function is designed, which solves both the overvoltage problem of control input caused by the overlarge position error of the manipulator and the problem that the manipulator system is difficult to start under heavy load. The simulation experiments verify the effectiveness and superiority of the proposed controller.

DC overvoltage suppression method of wind farm connected via MMC‐HVDC system

AbstractA new integration strategy of grid‐forming‐controlled wind farms connected to the bulk power systems through high‐voltage direct current transmission based on the modular multi‐level converter (MMC) is proposed to solve the problem of traditional uncontrollable DC overvoltage during the short circuit faults at the receiving end. However, a new DC overvoltage phenomenon appears after the fault is cleared, and the interaction between the wind farm and sending‐ and receiving‐end MMCs makes the DC overvoltage mechanism more complex; further exploration shows that DC overvoltage during the sending‐end fault recovery stage occurs under the new integration strategy. Therefore, the evolution process and mechanism of the new DC overvoltage are analysed. It is found that affected by the interaction between wind farms and MMCs, the alternate saturation of the integrators in the PI controller of MMCs is the main cause. Based on this understanding, additional controls are proposed to suppress this DC overvoltage during the fault recovery stage. Simulations are carried out on a test with MATLAB/Simulink, and the results verify the efficacy of the proposed methods in suppressing DC overvoltage.

The responsibility allocation method for overvoltage problem in distribution network with large-scale distributed photovoltaics integration based on the improved Shapley value

The responsibility allocation method for overvoltage problem in distribution network with large-scale distributed photovoltaics integration based on the improved Shapley value

Model Predictive Control on Transient Flux Linkage and Reactive Power Compensation of Doubly Fed Induction Wind Generator

For weak grid scenario with high new energy proportion, large fluctuations of load are prone to cause low-voltage ride through. Moreover, stator transient magnetic flux will cause overvoltage and overcurrent problems in the rotor of doubly fed induction generator. Based on model predictive control, a control strategy for transient flux linkage and reactive power compensation is proposed. Firstly, regarding the issue of reactive power allocation of grid side converters (GSC) and rotor side converters (RSC), an allocation strategy is derived under minimizing winding energy loss on case of low-voltage ride through, enabling the wind energy conversion system to provide reactive power support during grid voltage recovery process. Meanwhile, an improved mixed second- and third-order generalized integrator (MSTOGI) phase-locked loop (PLL) is used to extract the positive and negative sequence components of the power grid voltage, further for RSC control. Secondly, in response to power grid faults, considering the influence of stator DC transient flux and negative sequence flux components on rotor current, by injecting rotor transient compensation current and stator flux feedforward compensation into RSC, the rotor impulse voltage and loop current are reduced. Moreover, combined with model predictive control algorithm, a control strategy of rotor current is designed. Finally, a simulation platform is built to validate the effectiveness of the proposed method based on comparing with several traditional vector control low-voltage ride through methods.

An overvoltage adjustment strategy Based on Integrated Voltage Sensitivity in the Active Distribution Network

With the growing proportion of renewable energy resources represented by distributed photovoltaics in the distribution network, the overvoltage problem is becoming more and more serious owing to the photovoltaic reverse power flow in the active distribution network. This paper begins with the quantification and analysis of node voltage sensitivity, and the influence calculation formula of photovoltaic injection on the voltage sensitivity of the target node and other nodes is deduced; next, a general conclusion on the change of voltage sensitivity caused by active and reactive power of Photovoltaic is given. To solve the possible low control efficiency of control strategy simply depends on voltage sensitivity, a definition of so-called Integrated voltage sensitivity is proposed, and an optimized overvoltage control scheme is utilized under the distribution network structure. The effectiveness of the proposed control strategy is validated by a simulation example, namely, on the premise of not affecting the active power output of the photovoltaic as much as possible, the same overvoltage regulation effect can be obtained with smaller adjustments in reactive power output, further, rapid overvoltage regulation is achieved.

A Customer-Centric Distributed Data-Driven Stochastic Coordination Method for Residential PV and BESS

An aggregation scheme is an effective transactive manner of Distributed Energy Resources (DER) spreading across distribution networks. Distributed approach locally achieves cost minimization of an aggregator and customers. The uncertainties of wholesale market price and rooftop PV output will impact on aggregator's scheduling decision and each customer's cost, while solar energy fluctuation can cause an overvoltage problem in distribution networks. However, the probability distributions of these uncertainties always have errors, even in emerging data-based methods. There is no stochastic method using real data with an out-of-sample guarantee suitable for this distributed approach so far to help an aggregator avoid price risk and manage customers' energy against solar energy fluctuation. To address these unsolved issues, we propose a data-driven Wasserstein distributionally robust formulation of the aggregator's agent and customer's agent respectively. The Wasserstein metric is employed to construct the Wasserstein ambiguity set. The mathematical models are then reformulated equivalently to convex programming respectively so that the operating model can be solved by the off-the-shelf solver. To improve the efficiency of the distributed solving framework, an alternating optimization procedure (AOP) process is proposed to overcome the issue caused by binary variables in the alternating direction method of multipliers (ADMM). The proposed operation framework is verified on the modified IEEE 33-bus distribution network and realistic single-feeder LV network.

Effect of the drop out fuse connection scheme on the overvoltage and the surge arrester in a distribution system

Overvoltage is a critical problem of Thailand’ distribution system. The electrical protection device in the distribution system needs to be able to support this level of overvoltage. In the distribution system connecting the Chachoengsao2 substation and the Bang Khla substation, the overvoltage from a ferro resonance phenomenon affects the surge arrester directly. This research studies the effect of the drop-out fuse connection scheme on the voltage and surge arrester using the RMS/EMT Simulation mode in the DIgSILENT program. Normally, the surge arrester withstands a voltage of 1.9 p.u. of the phase voltage. If the overvoltage in the distribution system is higher than the voltage that the surge arrester can withstand, the surge arrester can be damaged. Therefore, it is necessary to study and analyze the drop out fuse insertion pattern that affects the overvoltage in the distribution system to understand the causes of overvoltage problems and their effects on each type of electrical protective equipment.

Optimization study of overvoltage problem in PV distribution network based on electrical energy router

Photovoltaic power generation has the advantages of being clean and efficient, but it poses a threat to the voltage quality of distribution networks due to unstable power output. In order to solve the overvoltage and power utilization problems of a high-penetration PV distribution network, this paper proposes a tidal current analysis model based on a four-port power router. First, the steady-state modeling of different ports of the electrical energy router is carried out, and the corresponding voltage control strategy is proposed. Then, by establishing a unified tidal current calculation model, a solution for the optimal operation of the distribution network is proposed. Finally, based on the overvoltage data of a regional power grid, the impact on the voltage level of the grid-connected PV system before and after the addition of the power router is compared. From the analyzed data, it is concluded that the introduction of a four-port power router for corresponding port control strategies can effectively improve overvoltage problems in high-permeability PV distribution networks.

Coordinated Frequency and Voltage Optimal Control of Wind Farm With Nonlinear Power Constraints

In the high-voltage direct current transmission system, if converter blocking occurs at the sending-end converter station, a serious power imbalance takes place in the sending-end grid, which causes severe over-frequency and over-voltage problems. To address this issue, a double-layer coordinated optimal control strategy based on model predictive control (MPC) is proposed in this article. By cooperatively regulating the active and reactive power of the wind farm at the sending end, it achieves coordinated frequency and voltage control. On the basis of MPC and moving horizon estimation, the upper-layer controller computes the optimal active and reactive power references of the wind farm. Subsequently, the optimized power references are fed into the lower-layer wind farm local controller for execution. A key feature of this strategy lies in its handling of nonlinear power constraints. Specifically, for a wind farm, coordinated frequency and voltage regulation faces a critical challenge of coupled nonlinear power constraints, which are formed by the coupled relationship between the active and reactive power outputs of the power converters. To overcome this challenge, the double description method is introduced to approximate and linearize the coupled nonlinear power constraints. Simulation results verify the effectiveness of the proposed strategy.

Research on the overvoltage suppression strategy of single-phase photovoltaic grid-connected systems based on FCS-MPDPC

For the overvoltage problem brought by the access of high-penetration photovoltaic power plants to the low-voltage distribution network, this paper chooses to deal with it by using the reactive power regulation capability of photovoltaic power plant inverters, which reduces the equipment investment in distribution line voltage regulation. Based on the reactive power regulation theory of the inverter, a finite set model predictive direct power control method is proposed by constructing a virtual voltage vector, taking a single-phase cascaded 2H bridge grid-connected inverter as an example, to realize independent control of active and reactive power. By setting different power reference values, the inverter can be made to have two functions: grid-connected per-unit power factor and reactive power control during overvoltage. Finally, the two modes of inverter operation are verified by Simulink simulation, and the verification by example shows that the method can limit the grid-connected voltage deviation to within 7% and meet the requirements of grid-connected regulations.

A novel estimation method for maximum PV hosting capacity in radial distribution networks using bus voltage and electrical distance

Large-scale photovoltaics (PV) generation at the distribution network causes overvoltage problems. These large PV systems are generally connected to the distribution network in three-phase configurations to ensure that power is balanced across all phases. At the same time, radial distribution networks are a common configuration of power systems worldwide as it is simpler and more cost-effective than meshed networks. In such a context, this paper proposes a novel method to estimate PV hosting capacity (PHC) for connection points in a radial and three-phase balanced distribution network. Different from existing methods that normally require power flow solutions of the network, the proposed method only needs line parameters and the historical voltage at the connection point. In addition, the proposed method features conservative estimation for PHC and thus can ensure the safety of network voltage compared with existing methods. The accuracy is tested on the IEEE 33 bus system and the estimation error is within 6%. Furthermore, the proposed method can be easily extended to consider branch losses that can reduce the estimation error to be within 1%. The obtained results have confirmed the feasibility and effectiveness of the proposed method.

A study on transient overvoltage caused by HVDC tie blocking in multi-rectifier systems

In a multi-rectifier AC-DC system the blocking of a HVDC tie can cause severe transient overvoltage problems, which may trip off the renewable energy sources, endangering the safe operation of the system. This paper shows that the blocking of a HVDC tie can introduce two types of transient overvoltage. For Type I overvoltage, which is caused by the surplus reactive power injection immediately after the blocking, a simple estimation formula is proposed. Suppression strategies that can decrease the key matrix are examined using a matrix-theoretic approach. The formula is applicable for system integrated with renewable energy sources and it has reasonable accuracy for overvoltage level of interest. To study Type II overvoltage, a reduced-order mathematical model is first derived with singular perturbation method. Then it is demonstrated that this type of overvoltage is due to the increase of transient electromotive force of synchronous machines, and an analytical calculation procedure is suggested. In addition, it is found that the voltage subsystem of a multi-rectifier system is an input–output monotonic system with nice order-preserving properties. Increasing the proportional gain constant of excitation system or choosing generators with large open-circuit transient time constant can monotonically decrease this type of overvoltage. The simulations of an actual large-scale multi-rectifier system in China are described to validate the introduced results.

Voltage Management of Distributed Photovoltaic Cluster Connected to a Distribution Network

The proportion of distributed photovoltaic grid connection in the distribution network is gradually increasing, and its characteristics of high volatility and poor stability have brought new challenges to the overvoltage problem faced by the distribution network structure and safe and stable optimization operation. This paper mainly studies clustering and reactive power optimization control of distributed Photovoltaic. The system architecture of the cloud edge is constructed, and the voltage autonomy strategy within the region after partition is proposed. The model is established with the total voltage offset and the minimum line loss as targets. Adopting adaptive PSO-BP algorithm model for optimization solution. Finally, conduct simulation analysis on the MATLAB platform. We can see that the proposed method can not only reduce the uneven voltage distribution, network loss, but also reduce the calculation burden of the controller has a positive effect.

A Distribution Static Synchronous Compensator Application to Mitigate Voltage Variation for Distribution Feeders

With the growing penetration of distributed energy resources (DER), the accompanying challenges have led utilities to limit the hosting capacities of DER installations on distribution feeders. A distribution static synchronous compensator (DSTATCOM) is a power electronic device to provide dynamic injections and absorption of reactive power into the distribution grid with more flexible and reliable voltage control and power quality improvement. A distributed energy resources management system (DERMS) is developed to provide more effective control of a DSTATCOM that can help substantially increase hosting capacity and mitigate overvoltage problems with the existing feeder. A Taiwan power company’s (Taipower) feeder is selected for computer simulation, and the DSTATCOM is employed in the test feeder to demonstrate the effectiveness of the DSTATCOM in improving the overvoltage problems. The voltage/reactive power (Volt/VAR) control of the DSTATCOM helps reduce overvoltage/voltage fluctuations as the DER output increases.

Fairness-Aware Distributed Energy Coordination for Voltage Regulation in Power Distribution Systems

The accelerating deployment of solar photovoltaics into low-voltage distribution networks can cause reverse power flow and overvoltage problems. However, if coordinated properly, the real and reactive power flexibility of these resources enables distribution operators to manage their networks more efficiently. Existing literature is rich in droop-based control (Volt-Watt and Volt-VAr) and optimization-based distributed energy coordination for four-quadrant control of photovoltaics to prevent overvoltage issues. While optimal coordination can effectively mitigate overvoltage, it treats resources at sensitive parts of the grid unfairly. To address this concern, we propose a distributed optimal power flow formulation that incorporates fairness in curtailing photovoltaic generation and utilizes the reactive power capability of smart inverters. Fair curtailment of photovoltaic systems is studied with aggregation at each of two layers in a distribution network: 1) area-level fairness and 2) feeder-level fairness to demonstrate the flexibility of the proposed approach in resource aggregation. To explore the trade-off, the fairness-aware control actions are compared against the performance of a centralized controller that aims to maximize the aggregate PV generation without incorporating fairness. Simulation results show that introducing area-level fairness increased curtailment by 1.11 percentage points, and feeder-level fairness increased curtailment by 4.7 percentage points compared to a fairness-agnostic control.

A Hierarchical Multi-Stage Coordination of Inverters for Voltage Control in Active Distribution Networks with a µPMU-PDC

This paper proposes a hierarchical multi-stage approach based on a distributed level phasor measurement unit (µPMU) at local controllers and a phasor data concentrator (PDC) at the central control unit to restore system voltage when it exceeds the limits recommended by the IEEE 1547-2018 standard. The proposed algorithm does not need an accurate system model or employ optimization solutions. Therefore, it has less implementation complexity and would be popular among distribution network service providers (DNSPs) and distribution network operators (DNOs) as it does not suffer from cost and computational complexity limitations. A PMU-PDC-based communication platform has been developed as a more efficient alternative to the supervisory control and data acquisition (SCADA) system, and provides superior characteristics, including a higher sample rate, higher data resolutions, and faster communication. The proposed coordinated algorithm aims to postpone power generation curtailment in distributed energy resources (DERs) with overvoltage problems (local DERs) by incorporating all the DERs that are not subjected to voltage violation (remote DERs) by absorbing their maximum reactive power capacity. If the system voltage has not recovered after absorbing all of the reactive power capacity of all the DERs, a reduced active power curtailment proposed by the algorithm is then applied to the system to control the voltage. The proposed strategy has been simulated in MATLAB and applied to IEEE 13-bus and IEEE 33-bus radial distribution benchmark systems to validate the performance of the system, in terms of its ability to coordinate voltage control and the accuracy of the PMU-PDC-based communication interface.

Thyristor-Based DCCB With Reliable Fast Reclosing Protection Ability by Restoring Capacitor Polarity

Lots of dc circuit breakers have been proposed for protecting medium voltage dc (MVDC) systems. However, they normally have one or more following limitations: low operational reliability, lack of controllability, lack of reclosing protection ability, power supply required, and high construction cost. To overcome these problems, a novel thyristor-based dc circuit breaker (TCB) is proposed in this paper. The proposed TCB could break the bi-directional current actively and reliably. In the reclosing process, the polarity of capacitor in the counter current loop could restore automatically to the initial state, and the auxiliary thyristor could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> naturally. As a result, the proposed TCB guarantees reliable fast reclosing protection ability on the premise of no additional pre-charge power supply. Moreover, all thyristors of the proposed TCB could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> by voltage drop of the anti-parallel diodes, and the overvoltage problem caused by reverse recovery process of thyristors is eliminated, which further enhances the reliability of TCB. The detailed topology introduction, parameters designing guidelines, scaled-down experimental results, and comparative study of the proposed TCB are all presented.

Model Predictive Control of Grid-Connected Battery Systems to avoid PV-induced Overvoltage

Photovoltaic (PV) power plants are currently built at a high rate, both small ones for single family houses and large-scale plants with a power output in the MW range. This development accelerated even more since the beginning of the energy crisis in 2021. Due to intermittent energy production, large voltage swings may result in the electrical grid, which are challenging for grid and operators. We are considering the problem of overvoltage in times of excessive PV production, which is well documented in the literature. To avoid overvoltage, without PV-curtailment or grid expansion, grid-connected battery systems are proposed. The research focus is on advanced control strategies for such systems which charge and discharge at appropriate times to reduce the overvoltage in the grid while simultaneously minimizing the required battery capacity. The work presented extends a previous contribution of the authors. The analysis was done in a simulation environment (MATLAB/Simulink).

Analysis of temporary overvoltage due to inverter-based distributed generation in networked distribution systems

This paper analyzed the temporary overvoltage (TOV) problem in the network distribution system. The TOV shows different patterns depending on the type of distributed energy resources (DERs) and the grounding method. In particular, the inverter-based distributed generations (IBDGs) also show different patterns as inverter’s dynamic characteristics depending on the classification of grid forming (GFM) and grid following (GFL). The paper reviewed existing factors affecting TOV according to the inverter type. In addition, the TOV was simulated in various topologies of distribution systems, indicating that distribution system topology can solve the TOV problem regardless of the inverter type. This paper compared the TOV in the radial distribution system and the networked distribution system (NDS), and as a result, the operation through NDS can be a solution to the TOV problem. In addition, TOV in the NDS is analyzed through simulation, considering various elements of the distribution system to prove a more robust solution.

Sequentially Coordinated and Cooperative Volt/Var Control of PV Inverters in Distribution Networks

Electric distribution grids are seeing an increased penetration of photovoltaic (PV) generation. High PV generation exceeding the grid load demand results in a reverse active power flow in the grid, which raises the voltage level. This paper presents a reactive power controller to overcome the overvoltage problem in the distribution system. A sequentially coordinated and cooperative volt/var control technique is presented. The proposed controller aims to use as low reactive power as possible while mitigating the voltage issues. Accordingly, it reduces the active power loss associated with reactive power flow and reduces the probability for active power curtailment of the PV system. The controller is developed for each lateral and is replicated for all laterals. The lateral controller coordinates the operation of the smart PV inverters in a sequential manner. Cooperative control is proposed between the laterals’ controllers as well and is engaged when the individual laterals’ controllers are unable to solve their overvoltage issues. The performance of the proposed controller is evaluated by comparing it to two other volt/var controllers, and it demonstrates better performance in terms of reactive power requirement. To conduct the simulation study, a modified version of the unbalanced IEEE 13-bus system is utilized, which includes an additional 44 low-voltage bus. The study involves simulating 720 operating points across daily time series. The results indicate that the proposed controller effectively addresses overvoltage problems that occur during periods of high PV generation.