7296results about "Power oscillations reduction/prevention" patented technology

Embodiments of the present invention include control methods employed in multiphase distributed energy storage systems that are located behind utility meters typically located at, but not limited to, medium and large commercial and industrial locations. These distributed energy storage systems can operate semi-autonomously, and can be configured to develop energy control solutions for an electric load location based on various data inputs and communicate these energy control solutions to the distributed energy storage systems. In some embodiments, one or more distributed energy storage systems may be used to absorb and/or deliver power to the electric grid in an effort to provide assistance to or correct for power transmission and distribution problems found on the electric grid outside of an electric load location. In some cases, two or more distributed energy storage systems are used to form a controlled and coordinated response to the problems seen on the electric grid.

The invention discloses an optimal virtual inertia control method based on a virtual synchronous generator in the distributed power generation control field. According to the method, a control strategy of a virtual synchronous generator is employed for a micro-grid inverter to organically combine three control degrees of freedom including a droop coefficient m, a virtual inertia J and a virtual damping D, and thus optimization of key parameters of the virtual synchronous generator is achieved. Through adoption of the method, the inertia advantage of a conventional synchronous generator is fully exhibited, and the stability and the inherent dynamic performance of an inverter are also taken into consideration. Moreover, the output power and frequency oscillation problems brought by virtual inertia are solved while the power and the capacity configuration of an energy storage apparatus are considered.

The invention provides a method and apparatus for an energy storage system to participate in power grid frequency control. The method comprises the steps of monitoring power grid frequency and charged states of an energy storage system in real time; if a power grid frequency offset exceeds a maximum frequency deviation, determining the energy storage system to participate into power grid primary frequency modulation according to deviation directions and the charged states; when a primary frequency modulation starting condition is satisfied, calculating virtual inertia response, a primary variable sagging control power adjustment value and a primary frequency modulation active control instruction; according to the primary frequency modulation active control instruction, carrying out primary adjusting of active power output of the energy storage system; starting secondary frequency modulation after time delay to determine a secondary frequency modulation instruction; according to the virtual inertia response, the primary variable sagging control power adjustment value and the secondary frequency modulation instruction, determining a secondary frequency modulation active control instruction; and according to the secondary frequency modulation active control instruction, carrying out secondary adjusting of the active output power of the energy storage system. Through adoption of the method and apparatus of the invention, coordination and cooperation between the energy storage system and other machine sets in aspects of primary frequency modulation and secondary frequency modulation can be well solved.

Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices are described. In one aspect, an electrical power distribution control method includes providing electrical energy from an electrical power distribution system, applying the electrical energy to a load, providing a plurality of different values for a threshold at a plurality of moments in time and corresponding to an electrical characteristic of the electrical energy, and adjusting an amount of the electrical energy applied to the load responsive to an electrical characteristic of the electrical energy triggering one of the values of the threshold at the respective moment in time.

In compensating for unbalanced voltages of three-phase AC, instantaneous values of wye-phase voltages 120° out of phase with each other are obtained from line voltages using a centroid vector operation, symmetrical component voltages of three-phase balanced system are obtained from the instantaneous values of wye-phase voltages, a compensation signal to compensate unbalanced voltages of three-phase AC is generated from zero-phase-sequence voltage of symmetrical component voltages is generated, wye-phase voltages 120° out of phase, the unbalanced voltages of which are compensated, are obtained from the compensation signal and the symmetrical component voltages, a control signal of a PWM conversion is generated based on the compensated wye-phase voltage compensated, and the unbalanced voltages of three-phase AC are compensated. The amount of time to compensate the three-phase unbalanced voltages required for detecting an unbalance of voltages and generating a control signal can be shortened.

A means for improving the dynamic and voltage stability of utility transmission systems is provided by the coordinated control of windfarms. Electrical measurements of the system, which may include synchronized phasors, are supplied to one or more windfarm controllers, which in turn perform a regulation function improving the damping of electromechanical oscillations or voltage performance in the utility system. The control structure is of a decentralized nature, which maintains operation in case of communication failures. The benefits are improved damping to electromechanical oscillations and better voltage performance and ultimately increased utilization of assets, reducing the install additional network assets.

The invention discloses a power system low-frequency oscillation mechanism analysis method based on micro-disturbance signal oscillation mode recognition. The method comprises the following steps of: providing a basis for judgment of oscillation mechanism types of power grid low-frequency oscillation accidents by using oscillation components provided by micro-disturbance recognition result in the process of a low-frequency oscillation accident; timely discovering a system running weak link and a potential oscillation source by performing statistic analysis on an entire-grid low-frequency oscillation mode oscillation frequency and damping ratio result which is calculated by micro-disturbance recognition in the given running time period; and establishing a corresponding relation between entire-grid oscillation mode characteristic change and system running condition parameter change to provide a basis for system running adjustment by performing multi-variable association analysis on the entire-grid low-frequency oscillation mode oscillation frequency and damping ratio result which is calculated by micro-disturbance recognition in the given running time period and the system running condition parameter.

Provided is a co-scheduling strategy for multiple energy storage in a distributed light storage micro-gird system. The based multiple energy storage adopts a two-stage converter topology structure comprising a preceding-stage bidirectional DC/DC conversion unit and a back-stage DC/AC conversion unit. A bidirectional DC/DC conversion unit for a storage battery and a bidirectional DC/DC conversion unit for a super capacitor share a DC bus, and are connected with a load and a large power grid through the DC/AC conversion unit and via an LC filter. The co-scheduling method of a two-stage converter for multiple energy storage is characterized by when the distributed light storage micro-gird system is in a grid-connected mode, carrying out double filter control on the two-stage converter for multiple energy storage, controlling the energy-storage element to carry out smooth photovoltaic output power fluctuation, and carrying out adjustment on filtering parameters according to the charge state of the super capacitor and the charge state of a storage battery; and when the distributed light storage micro-gird system is in an off-grid state, controlling the energy-storage element to provide voltage and frequency support to the distributed light storage micro-gird system, the distributed light storage micro-gird system jointly providing power for the load, wherein the energy-storage element is the storage battery and the super capacitor.

In one embodiment, a power conversion system includes a controller to provide power control to a converter, and a distortion mitigation circuit. In another embodiment, a system includes a converter to transfer power between a power source and a load having fluctuating power demand, and a controller to provide power control, where the controller may selectively disable the power control. In another embodiment, a power conversion system includes a controller to generate a drive signal to provide power control to a power path in response to a sense signal from the power path, where the sense signal is taken from other than the input of the power path, or the drive signal is applied to the power path at other than a first power stage.

A method, device and computer program product for the prediction of the stability of an electric power network, where the method is executed after a fault or contingency has occurred, and comprises the steps of (a) during a time interval in which the network is in a transient condition, determining for at least one load connected to the electric power network, at least one parameter describing an estimated steady state behavior of the load, (b) executing a load flow calculation for the electric power network using the least one parameter describing the estimated steady state behavior the at least one load, (c) determining, if the load flow calculation indicates stability has a solution, that a future stability of the electrical power network exists, or, if the load flow calculation indicates instability does not have a solution, that a future stability of the electrical power network does not exist.

A power generation system having a wind turbine blade assembly, a generator mechanically coupled to the blade assembly, and a power converter coupled to the generator is provided. An energy storage device and a bidirectional converter coupling the energy storage device to the power converter are also provided in the system. An inertia controller is provided for generating a first transient signal to regulate active power from the wind turbine system when a power grid signal is outside of a respective signal range. The system further includes an energy storage controller for providing a second transient signal to the bidirectional converter to regulate a power to or from the energy storage device based upon the first transient signal, power generating system conditions or combinations thereof.

An underfrequency load shedding protection system for stably managing a power system by recovering a power system frequency to within a predetermined range when the power system frequency drops. An underfrequency level detection unit judges an underfrequency level of the power system frequency when the power system frequency drops resulting from power generation shortage in the power system and a load shedding unit sequentially sheds loads determined in advance based on a staying time when the power system frequency stays at any one of the underfrequency levels judged by the underfrequency level detection unit and sheds on this occasion more loads quickly when the underfrequency level at which the power system frequency stays is large.

The invention relates to an energy storage system control strategy oriented to power grid AGC frequency modulation, characterized by comprising the following steps of battery energy storage involving in AGC frequency modulation structure design and of SOC layered control strategy. According to the invention, starting from the perspective of power grid AGC frequency modulation control, safety factors are designed for the battery energy storage operation cycle; the energy storage system's capacity and power restriction are fully considered; through the energy management to the energy storage system and based on the SOC layered control strategy, the power charging and discharging frequency modulation power for the energy storage system is determined, which means that while the power grid frequency becomes more stable, the energy storage system is steered clear of excessively charging and discharging. The method of the invention is scientific and reasonable. With strong practicability, the method can also achieve good performances.

A wind turbine (8) for controlling power oscillations on a grid of a power system (28). The wind turbine (8) comprises rotor blades (12) for turning by the wind, an electric generator (20) rotatably coupled to the rotor blades (12), a power converter (24) responsive to electricity generated by the electric generator (20), the power converter (24) for converting the generated electricity to a frequency and voltage suitable for supply to the power grid (28), and the power converter for regulating voltage on the grid supplemented by modulating real power for damping the power oscillations.

A new method for predicting the rotor angle stability status of a power system immediately after a large disturbance is presented. The proposed two stage method involves estimation of the similarity of post-fault voltage trajectories of the generator buses after the disturbance to some pre-identified templates and then prediction of the stability status using a classifier which takes the similarity values calculated at the different generator buses as inputs. The typical bus voltage variation patterns after a disturbance for both stable and unstable situations are identified from a database of simulations using fuzzy C-means clustering algorithm. The same database is used to train a support vector machine classifier which takes proximity of the actual voltage variations to the identified templates as features.

A harmonic-characteristics based current pattern matching method for the non-intrusive power load monitoring and disaggregation is provided in this present invention, on the basis of establishing the load signature database, which comprises electrical appliance registration and load state word space initialization, data acquisition and data preprocessing, feasible state word space search based on table looking-up, the optimal matching of current pattern, and display and output of the monitoring and disaggregation results. The method improves the accuracy of disaggregation, and can achieves exact identification of operating states of appliances, and also can reduce the cost.

A power grid stabilizing system may include a processor and a network interface executable by the processor to monitor for new event data from power consumption devices over a network. The new event data may include information such as device location, operating information, and sensor data. The system may include an estimation engine operable to analyze the new event data to determine power consumption behavior of a consumption device, and a predictor operable to anticipate an occurrence of a future event responsive to the analysis. The predictor may also predict the outcome of the future event based on analysis of the new event data in relation to past behavior data of the consumption device. The network interface may further communicate the anticipated future event and the predicted outcome to one or more of the other consumption devices.

The invention provides a virtual synchronous generator virtual inertia and virtual damping coefficient adaptive control method, which relates to the technical field of smart grid and intelligent algorithms. Firstly, the inverter based on the virtual synchronous generator is modeled, and the correlation between the output frequency of the inverter and the virtual inertia J and the virtual damping coefficient D is obtained. Then the fitness function of the adaptive control method of virtual inertia J and virtual damping coefficient D based on the improved particle swarm optimization algorithm isdetermined. Finally, the improved particle swarm optimization algorithm is applied to the active power. In the frequency control part, the real-time adaptive control of virtual inertia J and virtualdamping coefficient D is realized in order to minimize the frequency deviation and stabilize the system. The invention provides a virtual synchronous generator virtual inertia and virtual damping coefficient real-time adaptive control method, which fully utilizes the characteristics of the virtual inertia and introduces the virtual damping coefficient, so that the inverter is more stable and the frequency offset is smaller.