The invention discloses a global high-frequency oscillation suppression method of a weak grid-connected multi-inverter system, which can realize the high-frequency oscillation suppression of a multi-inverter system by introducing a common node PCC point voltage global variable and a grid-connected current high-frequency component into an inverter control link. Firstly, the virtual resistance of the shunt inverter at the PCC is constructed by introducing the feedforward of the point voltage of the PCC to suppress the harmonic resonance of the impedance network caused by the harmonic voltage ofthe inverter and the background harmonic voltage of the power network. Secondly, the high frequency component feedback of grid-connected current is introduced to construct the virtual impedance parallel to the output filter capacitor of the inverter, which increases the self-damping of the inverter and suppresses the parallel resonance of multi-inverter. The invention can effectively suppress theharmonic resonance phenomenon of a multi-inverter parallel system and fundamentally solve the problem of system stability caused by the increase of the number of inverters under a weak network.

A global high frequency oscillation suppression method for weak off-grid multi-inverter grid-connected system

The invention provides a mixed integer nonlinear programming model for solving the combination problem of a hydroelectric generating set, and belongs to the field of hydroelectric scheduling operation. The mixed integer nonlinear programming model for solving the combination problem of a hydroelectric generating set is characterized by utilizing a polynomial fitting technology to process the complicated power station nonlinear relation, providing a quartic equation polynomial fitting method of water level-capacity of reservoir-tailwater level-out flow, and based on a quadratic polynomial of head loss of the hydroelectric generating set, describing the generating head of the hydroelectric generating set as a multivariate quartic function of capacity of reservoir and flow; considering aboutthe influence of the head on the output, providing a binary quadratic polynomial method of accurately representing the output head and the generating flow of the hydroelectric generating set, introducing 0-1 variable, solving the startup-shutdown problem of the hydroelectric generating set, obtaining the head-flow-output relation three-dimensional fitting surface of the hydroelectric generating set, and satisfying the fine calculation demand of the output of the hydroelectric generating set under the variation head; and realizing calculation with high efficiency by means of a mature MINLP solver. The mixed integer nonlinear programming model for solving the combination problem of the hydroelectric generating set fully considers the complicated nonlinear relation of the hydroelectric systemand has the advantages of reducing the linear error and significantly improving the solution accuracy, compared with a classic MILP model. Besides, the obtained set combination and load distributionresult can preferably reflect the practical operation situation of the hydropower station.

Mixed integer nonlinear programming model for solving combination problem of hydroelectric generating set

The invention relates to a piecewise linearization-based power system optimal power flow calculation method, and belongs to the field of power system operation optimization. The method comprises the following steps: firstly, establishing a mixed integer nonlinear programming model of optimal power flow composed of an target function and constraint conditions; then carrying out piecewise linearization processing on a nonlinear part in the mixed integer nonlinear programming model, wherein the piecewise linearization processing includes secondary power generation cost equation constraints, capacitor adjustment constraints and tide equation constraints; sorting to obtain an optimal power flow model after piecewise linearization; and solving the optimal power flow model after piecewise linearization to obtain an optimal solution of the model, including optimal set reference values of all generators, continuous reactive equipment, capacitors and transformers, and realizing the optimal powerflow of the power system. The power flow model of the power system is accurately approximated through a piecewise linearization method, efficient and reliable solving of the optimal power flow problem is guaranteed, and then safe and efficient operation of the power system is achieved.

Piecewise linearization-based power system optimal power flow calculation method

The invention discloses a distributed control method and system for a hybrid power distribution network based on a consistency iteration algorithm, and the method comprises the steps that a local current converter performs information interaction with an adjacent current converter, and the active power Pg and reactive power Qg of a feed line connected with the local current converter are collected; the local current converter performs the consistency iteration algorithm calculation based on the interaction information through taking Pg as a state quantity, searching an active power consistencyvalue (shown in the description) of a global AC feed line, and setting a reactive power consistency value (shown in the description) of the global AC feed line as zero; generating an active power reference value P* of the local current converter through the regulation of the difference between the active power consistency value (shown in the description) and Pg, and generating a reactive power reference value Q* of the local current converter through the regulation of the difference between the reactive power consistency value (shown in the description) and Qg; enabling different current converter in the hybrid power distribution network to work in a coordinative manner in a specified working mode, and achieving the distributed control of the hybrid power distribution network. The methodenables a consistency algorithm to be introduced to the distributed control. The quick consistency convergence of the power of the feed line can inhibit the voltage fluctuation of a feed line node toavoid an out-of-limit condition when the new energy output changes, thereby improving the consumption capability of new energy.

Distributed control method and system for hybrid power distribution network based on consistency iteration algorithm

The invention provides a multi-photovoltaic-power-station cooperative frequency modulation system based on neighborhood communication and a control method. The system comprises photovoltaic power stations and a power grid. The multiple photovoltaic power stations are connected with the power grid, and each photovoltaic power station comprises a photovoltaic array and a grid-connected inverter. According to the method, the optimal distribution of the total frequency modulation reference power among a plurality of photovoltaic power stations with different irradiance is realized by utilizing anaverage consistency algorithm. Due to the fact that the geographic position distance between the photovoltaic power stations is long and communication resources are limited, all the photovoltaic powerstations are difficult to obtain global information and use the global information in centralized control. The invention provides the distributed control method. When the power grid frequency fluctuates, a power station is required to perform frequency response quickly.

Multi-photovoltaic-power-station cooperative frequency modulation system based on neighborhood communication and control method

The invention discloses a hydro-thermal generator set combination optimization scheduling method based on mixed integer programming. The method comprises a step of obtaining the basic data of a single hydropower station, wherein the basic data comprises a reservoir water amount, a limit value of the reservoir water amount and a limit value of power generation flow, a step of carrying out piecewise linearization on a nonlinear constraint condition in the constraint conditions of a single hydropower station optimization scheduling model, a step of solving the single hydropower station optimization scheduling model which allows a target function F to be minimal according to a constraint condition which is subjected to piecewise linearization, a linear constraint condition of the single hydropower station optimization scheduling model and the basic data of the single hydropower station, and a step of determining a hydro-thermal generator set combination optimization scheduling model according to the single hydropower station optimization scheduling model which allows the target function F to be minimal. According to the method, the direct solution of a non-convex nonlinear problem of the nonlinear coupling of variables in time and space is avoided, and the operation efficiency of a power system is improved.

Hydro-thermal generator set combination optimization scheduling method based on mixed integer programming

The invention discloses a frequency recovery method and system of a photovoltaic microgrid. The method comprises the steps of determining a virtual electric angular speed output from a virtual synchronous power generator, acquiring a set electric angular speed, and acquiring state quantity to be controlled, wherein the state quantity to be controlled is a specific value between an actual value of an active power output from the virtual synchronous power generator and maximum power value which can be output from the virtual synchronous power generator; determining a derivation formula of the state quantity to be controlled on time t according to a distribution consistency algorithm; calculating to obtain control quantity according to the derivation formula, the virtual electric angular speed output from the virtual synchronous power generator and the set electric angular speed of the virtual synchronous power generator; adjusting the actual value of the active power output from the virtual synchronous power generator by using the control quantity. The frequency modulation characteristic of a power system and the consistency algorithm are combined, thus, all photovoltaic power supplies with different properties can output according to proportions consistent with maximum available capacity, and moreover, a frequency of the system is adjusted and recovered to a set value.

Frequency recovery method and system of photovoltaic microgrid

The present invention discloses a method and a system of damping control for reduction of inverter parallel resonance. The method and the system employ a dual-layer control strategy, upper-layer control selects one appropriate enabling inverter from each inverter according to one charge state of one direct current side power supply of each inverter in a multi-inverter parallel system, and lower-layer control arranges a virtual resistance control ring in a working circuit of the enabling inverter so as to perform active damping control for the enabling inverter and achieve resonance inhibitionof the multi-inverter parallel system. The method and the system only need to perform active damping control for one inverter to achieve resonance inhibition of all the inverters, a current measurement link of a network system is employed to perform parameter calculation in the process of achieving damping control of the inverters, and therefore, the fewest circuit modules are introduced to achieve inhibition of multi-inverter parallel resonance and the system cost is greatly reduced.

Zheng Tianwen

Papers

Hydro-thermal generator set combination optimization scheduling method based on mixed integer programming

Frequency recovery method and system of photovoltaic microgrid

Method and system of damping control for reduction of inverter parallel resonance