In recent years, due to the development of contemporary science and technology, coupled with the impact of energy shortages and environmental protection, human beings are working to find renewable, inexhaustible and clean green energy, and water energy and Wind energy is the most promising and promising variety of green energy. At the same time, water and wind energy are easily transformed into a higher-level form of energy, electric energy, with significant economic benefits.
Due to the randomness and seasonality of wind resources, the output of wind power is not stable, and wind power does not have the ability of active regulation and reactive power regulation. The shortcoming of wind power is that there is no electricity without wind, which affects the continuity and stability of wind power. In order to solve the problem of continuity and stability of wind power, a complementary system is needed.
The journals of Xinjiang Institute of Technology are in the inland wind regions of Northwest China, North China, Northeast China, etc. The seasonal distribution of wind resources is mostly characterized by large winds in winter and spring, small winds in summer and autumn, and the formation of water in summer and autumn with water resources and the distribution of dry water in winter and spring. Complementary characteristics, which are the basic conditions for the construction of wind energy-water complementary systems. In the above-mentioned areas, relying on hydropower stations with water storage regulating reservoirs, wind farms with appropriate capacity will be built in wind-rich places. The two will be connected by grid to achieve seasonal energy complementation, and the reservoir will be used as an energy adjustment means. It can realize the marriage of the two best green energy sources of wind energy and water energy, give full play to the advantages of green energy, and replace the traditional water-fire joint power supply with wind-water joint power supply, which will be a historical breakthrough in the form of human energy utilization.
Due to the strong complementarity of wind resources and water resources in the Altay region, and because of the large hydropower installed capacity in the Altay region, and three of these power stations have a large reservoir of regulated reservoirs, they have broken through traditional restrictions in the region. It is technically and economically feasible to build a hydropower-wind power complementary system under the condition that the wind power installed capacity greatly exceeds the power grid capacity of 10. There are still many areas in China that have similar resource conditions as Altay. They can build a hydropower-wind power complementary system to solve the power supply problem. This will be an important breakthrough for the existing restricted area. It is possible to find a power supply for Altay and similar areas. The fastest way to save the province.
1Proposed problem In the power system, the traditional power generation methods are hydroelectric power and thermal power generation, which are generally synchronous motors. At present, the new member of wind power generation joins the power grid, and generally uses a capacitive excitation induction asynchronous generator. Complicate its analytical calculations. At the same time, the addition of wind power affects the stability of the power grid. In order to calculate and analyze the static and transient and dynamic stability of the power system, the power flow calculation must first be performed.
Power system power flow calculation is a calculation to study the steady state operation of the power system. It determines the operating state of each part of the entire power system according to the given operating conditions and system wiring conditions, the voltage of each bus, the power flowing through each component, Power loss of the system, etc. How to determine the operating conditions for wind turbines and how to determine the parameters is the key to calculating the power flow of power systems with wind power.
2 Wind Turbine Processing Power system is an energy production, transmission and use system consisting of three major parts: power plant, transmission network and power load.
According to the fan power generation principle, when the fan is connected to the grid, the amount of active power generated is only related to the wind speed, and has nothing to do with the load change. When the grid voltage and active power and reactive power change, it can only be adjusted by the excitation system and the speed regulation system of the synchronous generator of the grid. The pneumatic equipment and energy transfer device of the asynchronous generator are not involved in the adjustment. Therefore, the wind turbine as a whole is a disturbance source like a load, which interferes with the constant and power balance of the grid voltage as the wind speed changes, causing it to fluctuate. Therefore, in the power system, the water-fire synchronous generator, excitation system, speed control system, wind asynchronous generator, load and power network are combined into a whole mathematical model, as shown in Figure 1.
In the block diagram, the hydroelectric generator and the thermal power generator are the controlled objects. The excitation regulation system and the speed regulation system are controllers. The transmission lines and transformers are simulated by resistor, capacitor and inductor equivalent circuits. The wind turbine and the load are equivalent to the interference source. .
3 Power flow calculation principle In the power flow calculation, the generator and load are treated as nonlinear components and cannot be included in the linear network part. For the linear network part, the relationship between the node current and the voltage can be described by the node equation: the wind power-hydropower complementary power system power flow calculation in order to solve the power flow problem, using the relationship between the node power and the current in the power system current In the calculation, the parameters that characterize the operating state of each node are the voltage vector and complex power at that point. That is, each node has four quantities that characterize the operating state of the node: voltage V, phase angle θ, active power P, none. The power power Q, therefore, has 4n operating parameters in the power system of n nodes. In the general power system power flow calculation, two operating parameters are often given as known conditions for each node, and the other two are used as the required quantities. According to the way the original data is given, the nodes in the power system are divided into the following three types: (1) PQ nodes. The parameters given by such nodes are the active power and reactive power (P, Q) at that point, and the amount to be determined is the voltage vector (V, θ) at that point.
(2) PV node. The operating parameters given by such nodes are the active power P and the voltage amplitude V at that point, and the amount to be determined is the reactive power of the point and the angle θ of the voltage vector.
(3) Balance node (Vθ node). In power flow calculation, such nodes are generally only one in the system. For this node, the voltage amplitude V of the point is given, and the direction of the voltage vector of the point is taken as the reference axis in the calculation, which is equivalent to the angle θ of the voltage vector given the point is zero degree, therefore, given to this node The operating parameters are V and θ and therefore may also be referred to as Vθ nodes. For the balanced node, the amount to be determined is the active power P and the reactive power Q at that point, and the power balance of the entire system is completed by this node.
The Newton-Raphson method (hereinafter referred to as the Newton method) is an effective method for solving nonlinear equations. This method turns the solution process of the nonlinear equation into a process of solving the corresponding linear equation repeatedly, which is usually called the successive linearization process, which is the core of the Newton method.
The power system power flow calculation can be roughly reduced to the problem of solving the voltage vector of each node by the complex power given by each node of the system. Therefore, if the complex power can be expressed as the equation of the voltage vector of each node, the Newton solving nonlinear equation can be utilized. The method solves the voltage vector of each node of the system.
In the power flow problem, the equation of the node power: the amount to be determined is the two components n of the real and imaginary parts of the voltage of each node. Since the equilibrium node voltage vector is given, the power equation except the equilibrium node is in the iterative process. In addition to the constraint, each of the other nodes can list two equations. For PQ nodes, P is given and can be listed in (3).
For the node, the given amount is P is, therefore, it can be listed: the above equation is developed according to the Taylor's series, and after the high-order term is omitted, the modified equation can be obtained. The matrix form corrects the expressions of the elements in the Jacobian matrix in the equations and equations.
The modified equation in the Cartesian coordinate system is the basic equation that needs to be solved repeatedly in the Newtonian power flow program.
In the Newtonian trend program, the power network is described by an admittance matrix, so the admittance matrix should be formed first in the calculation. The Newton method power flow calculation process is roughly divided into the following steps: (1) Given the initial value of each node voltage e(2), the initial voltage value e is substituted into the node power equation, and the constant term ΔP(3) of the modified equation is obtained. The initial value e is substituted into the expression of the element in the Jacobian matrix to find the elements of the coefficient matrix of the modified equation. (4) Solution correction equation to obtain the correction amount △e (5) Correct the voltage vector of each node: e Substituting the power equation to find ΔP ( 7) Check whether the convergence is convergent.
If it converges, then the current trend of each branch is obtained and the calculation result is printed out. Otherwise, e is the initial value, and the third step is returned to the next iteration. The process of Newton's method for solving the power flow problem is actually the process of continuously forming and solving the modified equation.
A block diagram of the Newton's power flow program.
4 Wind power system power flow calculation of power system with wind power generator Because the wind power generator is an asynchronous generator, it absorbs reactive power and emits active power. Its characteristics are similar to the load, and the node power is not adjustable with voltage and frequency. The difference is that the load absorbs both reactive power and active power, S= P jQ. Therefore, the node containing the wind turbine is equivalent to the PQ node, and the PQ node processing according to the power flow calculation participates in the iterative calculation, but it is necessary to pay attention to the input computer P, Q. When the parameter value, P should take a positive value, Q should take a negative value, and the symbol should also be considered in the iterative calculation. For the convenience of the user, the power flow calculation program we compiled only needs the user to input the positive value P and Q, which is automatically added by the computer. negative.
Based on the above analysis principle, we applied the advanced computer language program to calculate the power flow of the wind power hydropower network system in Burqin County, Altay Prefecture, Xinjiang. The Burqin Power Grid is currently mainly powered by the Tohongtai Hydropower Station and the wind farm, with installed capacity 2 and adjustable storage capacity. At the same time, the wind farm installed on the grid is installed with a total of 18 nodes and 19 branches in the 7×150=1 050kW grid. The specific parameters are omitted.
For the PQ node of the wind turbine, P is given, and the power equation can be listed as logistics: etc.: The wind power-hydropower complementary power system power flow calculation is calculated by (5) participating in the power flow iteration calculation. In the output of the power flow calculation result, for the sake of intuition, the active power output value is listed in the generator power output column, and the reactive power output value is listed in the load absorption power column. Node 4 is a wind turbine node. Its active power is in the power generation column, and the reactive power is in the load power column. Table 1 and Table 2 show the output calculation results of the power flow calculation results of some nodes in the Fengshui Complementary Power Grid.
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