The traditional technical line loss prediction method of low voltage station area has some problems，such as relatively extensive calculation，requiring underlying physical topology，and relying on influence characteristic data. In recent years，a technical line loss and meter error joint estimation technical route based on the principle of conservation of electric energy in station area has been formed，but there are still some problems of difficult model solving and long data requirement period. In order to achieve accurate estimation of technical line loss in low voltage station area，the correlation between daily technical line loss and energy supply was further analyzed on the basis of the existing joint estimation route，and the original model was optimized considering those users with small energy consumption have little influence on the model，and the technical line loss was solved based on gradient descending convex optimization algorithm. Finally，6 759 stations in a certain area were used to calculate the technical line loss. Compared with the traditional algorithm，the assignment accuracy of the proposed method reaches 98%，and is significantly improved.

Under the large-scale renewable energy integrated with uncertain output characteristics，balancing the supply and demand within a local area becomes a new challenge.The long-distance transmission and consumption scheme is utilized for the sending-end grid to meet the requirements of renewable energy consumption.Within the constraints of thermal stability，dynamically improving the transmission lines' rating capacity has become a critical method for the sending-end power grid.However，due to the insufficient thermal stability calculation model，the existing improvement methods have the problems of significant evaluation deviation and narrow applicability in the practical application of the sending-end power system the improvement scheme usually needs to be customized and modified for specific line. In order to solve above issues，firstly，the influence of dust corona heating on the thermal stability transfer capacity at the sending end was analyzed，and an improved model of line thermal rating based on the dust effect was proposed. Furthermore，considering the uncertainty of the dust effect，a calculation method of dust effect control parameters based on fuzzy analysis was proposed，and the thermal rate capability calculation model was improved. Finally，combined with the meteorological forecast，a scheme for improving the thermal rating capacity of the renewable energy transmission power grid was constructed，which can be analyzed for multiple lines simultaneously. Via the practical engineering case of the Ningxia power grid and the power meteorological forecast data of China Electric Power Research Institute，the effectiveness and applicability of the improvement model of dust effect and the improvement scheme of multi-line thermal stability transmission capacity were verified.

Accurate topology and line parameter information is the basis of state estimation and security control of distribution network. Affected by the performance of collection terminals and environmental factors，the measurement error of metering equipment often deviates from Gaussian distribution. Higher requirements are put forward for the robustness of topology and parameter identification model under non-Gaussian noise measurements.The mathematical optimization model of distribution network parameter identification was firstly constructed with the goal of minimizing power estimation error. In order to improve the performance of identification algorithm in complex error scenarios，the correntropy induced loss function was established，and an improved correntropy matching pursuit （CMP） algorithm was proposed based on half-quadratic optimization and noise filtering. Finally，the simulation analysis was carried out on IEEE 33- and 85-bus distribution system，and the test results show that the proposed method can correctly identify the topology and effectively estimate the line parameters in both Gaussian and non-Gaussian data noise scenarios.

The permanent magnet synchronous generator （PMSG） is prone to current overstep in unbalanced grid，which affects the reliability of grid-connected system. To solve this problem，low-voltage ride-throgh control strategy based on direct power control was proposed. In this strategy，the direct power inner loop was used to control the grid-side inverter，and the active power and reactive power instructions were divided into DC components and double frequency AC components. The reference values of the DC components of active power and reactive power were calculated on the premise of the low voltage traverse reactive power support and the current amplitude of the inverter. The reference values of the AC components of active power and reactive power were calculated according to three different control objectives according to the voltage and current of the junction point. Then the control loop was designed by the quasi-proportional resonant controller. Finally，a simulation model was built based on Matlab/Simulink，and the simulation results show that the proposed control strategy can improve the dynamic performance of the inverter and improve the operation ability of the grid-connected system under the unbalanced grid.

In order to improve the compensation effect of LCL-type shunt active power filter，a frequency adaptive decimal delay repetitive control based on IIR filter was proposed. The resonance suppression loop of LCL was designed through root locus and the design result was used as a new control object for repetitive control. The IIR filter used could approximate the decimal delay caused by frequency changes，thereby matching the resonant frequency of repetitive control with the fundamental and harmonic frequencies of the power grid. The adaptive implementation diagram，the phase characteristics of the approximation part，and the design method of the compensator in sequence were presented. Finally，the stabilities of the system were analyzed. Simulation and experimental verification show that the proposed method can improve the steady-state tracking performance and THD of the system.

Modular multilevel matrix converter （M3C） is a multilevel topology that can directly realize AC-AC conversion，which has good application prospects in high-voltage transmission systems and DC distribution systems，but the existence of bridge-arm circulating channels inside the M3C leads to a very complex control structure. For this reason，a hierarchical system control strategy was proposed. First，the mathematical model of the M3C was derived based on the conventional double αβ0 coordinate transformation. Then，a dual-loop control structure consisting of an outer-loop and an inner-loop controller was employed in the M3C，which is usually employed in voltage source converters. In addition，in order to suppress the loop current component inside the system，a bridge arm energy equalization control strategy based on double αβ0 transform decoupling was proposed，through which the capacitive voltage control between the bridge arm and the bridge arm was realized by this control and carrier phase shift modulation. Ultimately，the simulation model and physical prototype were constructed，and the outcomes validated the viability of the proposed control strategy for the M3C system.

Since the compressed air energy storage system grid-connected inverter voltage is always influenced by voltage fluctuations of the power grid with little problem，for the sake of ameliorating the dynamic and stable performance of the DC bus voltage of the inverter on the side of the grid and the actual output power of the system in the compressed air energy storage expansion power generation system and reducing the fluctuations，second-order linear active disturbance rejection control （LADRC） technique was used in the voltage outer loop control，a new-style double closed loop control construction was formed. The mathematical model of the grid-connected converter of expansion power generation system was established，the operating principle of LADRC was researched，and the conventional PI control was contrasted with the control methods studied. The simulation results indicate that when make a contrast with the conventional control methods，the control methods designed can make the DC voltage enter the stable state more quickly，the total harmonic distortion （THD） of the grid-connected current becomes smaller，and has better disturbance immunity.

The electricity power price setting mechanism will be fundamentally reformed with the continuous advancement of a new round of electricity market-oriented reform. Presently，some provincial and regional power grid enterprises are facing the problem of large fluctuations in electricity prices，which is not conducive to the in-depth promotion of electricity marketization reform. Firstly，based on the partial least squares method，the agency power purchase price formation model was established. Then，the main factors affecting the fluctuation of power purchase price were analyzed，and the mechanism of the influence of power supply and consumption balance on the price change of different types of electricity consumption was clarified. In order to reduce the fluctuation of electricity purchase price，a multi-objective optimization model of agent electricity purchase was established with the constraint of power supply and consumption balance. The actual example results show that the model can realize the reasonable distribution of power consumption among different types of power sources in the process of agent power purchase，and effectively reduce the fluctuation of agent power purchase price.

With the increasing penetration of new energy equipment，while alleviating the environmental problems caused by fossil energy，it also increases the frequency instability of the system. Photovoltaic （PV）and other new energy equipment to participate in the grid frequency regulation is an effective way to improve the frequency stability of the power system.First，the basic principle of frequency response of synchronous machine was analyzed，the correspondence was determined which is between active output of PV power generation and primary frequency regulation and inertia response，and the virtual synchronous control strategy of PV power generation was formed.Then，based on the power-frequency correspondence relationship of primary frequency regulation，it gave the parameter adjustment method that directly corresponds to the frequency and the load shedding rate，and realized the function of primary frequency regulation. Once again，based on the inertia response minus the frequency-power correspondence relationship，it gave the inertia response minus the frequency-power correspondence relationship，which is the most effective way to improve frequency stability of power system. Once again，based on the correspondence between inertia response frequency reduction and power，the parameter setting method of inertia response load shedding rate was given，and the negative influence of inertia in the process of frequency restoration was avoided through the determination of application conditions of inertia response. Finally，the PV grid-connected model was constructed，which verified that the PV load shedding operation has the ability to participate in the frequency regulation of the power grid.

In order to solve the problem that the time-of-use price is not taken into account in the calculation of the peaking cost in the case of a large number of renewable energy sources，a method of calculating the peaking cost of power system with time-of-use price was proposed. First，the key scenarios of power grid peak regulation were obtained，and the technical cost characteristic boundaries of various peak regulation resources were determined. Second，according to typical daily new energy and load characteristics，taking the minimum total peaking cost of the power system as the objective function，taking into account the technical output of thermal power units，charging and discharging characteristics of energy storage，capacity of pumped storage power station and other constraints，and taking into account the time-of-sale price factor，a quantitative model of the peaking cost of the power system was established. Finally，through solving the model，the peak load balancing cost and unit output under the optimal scheme were obtained. The actual data of Ningxia Power Grid，the first provincial power grid whose output of new energy generation exceeds the entire regional power load，was taken as an example to verify the model. The results show that the model can effectively evaluate the peaking cost and unit output in the key scenarios of power grid peak regulation.