CN103986186A - A black-start control method for wind-solar-hydraulic complementary microgrid - Google Patents

Abstract

The invention relates to a black-start control method of a wind-solar-hydraulic complementary micro-grid, belonging to the technical field of power system micro-grid optimization control. The method includes: reading in the basic data of the micro-grid; Select the unit; sort the candidate units of the black start power supply according to the power size, and take one of the units in turn as the black start unit; each distributed power supply selects the control strategy and controller parameters according to whether it is a black start power supply and whether it participates in the frequency control of the isolated network , to obtain the alternative microgrid black start scheme; perform simulation calculations on the obtained alternative microgrid black start scheme, and judge whether the black start process of the alternative scheme and the isolated grid operation, whether the voltage of each node of the microgrid and the frequency of the microgrid satisfy Constraints such as stability and safety limits, and those that meet the constraints are regarded as feasible schemes, and the optimal scheme is selected among the feasible schemes. The method ensures that the wind-solar-water complementary microgrid has high reliability and economy.

Description

A black-start control method for wind-solar-hydraulic complementary microgrid

technical field

The invention belongs to the technical field of optimization control of electric power system micro-grids, and in particular relates to a black-start optimization control method of a micro-grid containing wind power, photovoltaics, and small hydropower.

Background technique

Black start means that after the power grid is completely shut down, without relying on external power supply, the units with self-starting ability in the system drive the units without self-starting ability, gradually expand the scope of system recovery, and finally realize the recovery of the entire system.

After the microgrid has a total shutdown accident in the large power grid or its own isolated grid operation and a total shutdown accident, the safe and rapid black start is of great practical significance to ensure the power supply of key loads. Microgrid black start control requires active and reactive power control of small hydropower, wind, solar and other new energy sources, and load regulation of microgrid, so as to realize automatic adjustment of voltage and frequency during microgrid black start preparation, grid recovery and load recovery process. Adapt to avoid the self-excitation problem in the early stage of black start, the overvoltage problem in the grid recovery period, and the frequency fluctuation problem in the load recovery period. Due to the intermittent and random characteristics of distributed power sources such as wind power, photovoltaics, and small hydropower, how to coordinate the output of small hydropower groups and new energy or adopt energy storage methods to meet the requirements of black start on the basis of ensuring the safe operation of the microgrid The required response speed and response capacity are the keys to the success of black start.

At present, there are many researches on the black start of the micro-grid including wind, photovoltaic and energy storage devices. For the black start of the regional small hydropower/wind and photovoltaic new energy micro-grid, especially the black start process and the isolated grid operation after the black start is successful, Coordinated control of active power control devices of various power sources, and less research on isolated grid frequency control.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the existing technology, and propose a black-start control method for the wind-solar-water complementary microgrid. High reliability and economy.

The technical solution of the present invention is to study the best micro-grid black start scheme and micro-grid control strategy under the condition of meeting the micro-grid voltage and frequency requirements on the basis of the established dynamic models of wind power generators, photovoltaics, and small hydropower stations. Make the entire microgrid black start process restore the load as soon as possible and as much as possible under the premise of ensuring safety.

A black-start control method for a wind-solar-hydro hybrid microgrid proposed by the present invention is characterized in that the method comprises the following steps:

(1) Read in the basic data of the microgrid, including the microgrid model, microgrid switch status, wind speed, solar radiation intensity data, water regime data of each small hydropower group, and load forecast data of each load node;

(2) The distributed power supply that meets the black start conditions is used as the black start power supply candidate unit, otherwise it is used as the activated power supply candidate unit;

(3) Sort the candidate units of the black start power supply according to the power, and take one of the units as the black start unit in turn; other distributed power sources in the microgrid are used as the activated units. Participate in isolated grid frequency control to select control strategies and controller parameters, and obtain alternative microgrid black start schemes;

(4) Perform simulation calculations on the alternative microgrid black start schemes obtained in step (3) one by one, and judge whether the voltage of each node of the microgrid and the frequency of the microgrid are stable during the black start process of the alternative scheme and the operation of the isolated grid , safety limits and other constraints, if the constraints are met, it will be regarded as a feasible solution, and the optimal solution will be selected among the feasible solutions.

The advantages of the optimal operation control method for wind-solar-hydro hybrid microgrid proposed by the present invention are as follows:

1. The black start process utilizes the adjustment and power generation capabilities of small hydropower, complementing energy storage devices and photovoltaics.

2. Optimize the control strategies and parameters of the micro-grid photovoltaic/energy storage device inverter and the speed control system of small hydropower units to meet the needs of micro-grid frequency control during the black start process and isolated grid operation.

3. Considering the system security operation constraints, a variety of black start strategies are considered, which improves the flexibility and adaptability of the black start scheme.

Description of drawings

Fig. 1 is a flow chart of the optimal operation control method for a wind-solar-hydro hybrid microgrid proposed by the present invention.

Fig. 2 is a control block diagram of the grid-connected inverter in the present invention.

Detailed ways

A black-start control method for a wind-solar-water complementary microgrid proposed by the present invention is described in detail below with reference to the accompanying drawings and embodiments.

The process flow of a black-start control method for a wind-solar-water complementary microgrid of the present invention is shown in Figure 1, including the following steps:

(1) Read in the basic data of the microgrid, including the microgrid model, microgrid switch status, wind speed, solar radiation intensity data, water regime data of each small hydropower group, and load forecast data of each load node;

(2) The distributed power supply that meets the black start conditions is used as the black start power supply candidate unit, otherwise it is used as the activated power supply candidate unit;

(3) Sort the candidate units of the black-start power supply according to the power (small hydropower units and photovoltaic power stations take the current stable output power, and the energy storage device takes the stable output within 1 hour), and take one of the units as the black-start unit in turn; Other distributed power sources in the microgrid are used as the activated units, and each distributed power source is selected according to whether it is a black start power supply and whether it participates in the frequency control of the isolated grid, and the control strategy and controller parameters are obtained to obtain an alternative microgrid black start scheme;

(4) Perform simulation calculations on the alternative microgrid black start schemes obtained in step (3) one by one, and judge whether the voltage of each node of the microgrid and the frequency of the microgrid are stable during the black start process of the alternative scheme and the operation of the isolated grid , safety limits and other constraints, if the constraints are met, it is considered as a feasible solution, and the optimal solution is selected among the feasible solutions (during the black start process, the total power generation of the microgrid is the largest).

The specific implementation of the above-mentioned steps is described as follows:

Step (2) Use the distributed power supply that meets the black start conditions as the candidate unit for the black start power supply, otherwise as the candidate unit for the activated power supply; specifically includes:

(2-1) The black start conditions that the hydraulic turbine unit as the black start power supply candidate unit meet are: the power system of the factory works normally; the normal standby condition is available (that is, the unit is in the standby state); the oil level and oil quality of each part of the unit are qualified; The oil pressure and oil level of the oil pressure device of the governor are in the normal range; the DC control power supply of the outlet switch of the unit is normal; the corresponding high-voltage plant transformer and load switch of the unit are normal; the control of the unit and common parts is normal, and the signal DC power supply is normal; the unit does not affect the start Defects;

(2-2) The black start conditions that the energy storage device/photovoltaic power station meets as a black start power supply candidate unit are:

The grid-connected inverter of the energy storage device/photovoltaic power station has an islanding operation mode, the anti-islanding detection function exits, and the power station as a whole meets the requirements for commissioning and starting up according to regulations;

(2-3) The black start conditions that the wind turbine unit as the black start power supply candidate unit meet are:

The emergency power supply of the wind farm (such as diesel generator set) can meet the power supply requirements of the fan auxiliary system; the phase sequence of the power supply is correct, and the three-phase voltage is balanced; the steering system is in a normal state, and the anemometer and wind vane are in a normal operating state; The oil pressure and oil level of the hydraulic device of the system are within the specified range; the oil level and oil temperature of the gearbox are within the normal range; all protection devices are in the correct input position, and the protection settings are consistent with the approved settings; The control power supply is in the on position; the control computer shows that it is in normal operation; there is no ice on the impeller before manual start; in cold and humid areas, the insulation of wind turbines that have been out of service for a long time and are newly put into operation is qualified before being put into operation; Before the start-up of wind turbines, all safety measures established for maintenance have been dismantled.

(2-4) Black start power selection

In the absence of external power grid support, the self-starting capability of the black start power supply is the key to the successful completion of the black start of the system. Traditional power systems use hydroelectric generators or large gas turbines as black start power sources. By analogy, it can be concluded that the principle of the micro-grid system in the selection of black start power supply (power plant operators can judge according to the operating procedures of the station):

a) With energy storage unit: (Because the power generation capacity of renewable energy such as photovoltaics and wind power fluctuates significantly when natural conditions change, it is difficult to maintain a constant isolated grid frequency.) The black start power supply of the microgrid system is the first choice for energy storage devices without intermittent problems , (such as battery energy storage micro-sources, flywheel energy storage micro-sources, etc.), these micro-sources also have all-weather start-up capabilities and are not affected by external factors such as weather.

b) Capable of voltage regulation and frequency regulation: (in order to ensure the voltage and frequency stability of the micro-grid system in the off-grid state,) the black start power supply has voltage source output characteristics, and also has voltage regulation and frequency regulation functions, which can ensure power distribution The excitation loss of the transformer and the no-load loss of the AC bus of the micro-grid system can withstand the short-term power impact when other non-black start power supplies are started.

c) Sufficient reserve capacity: the black-start power supply itself has sufficient power generation capacity to provide start-up power for other power sources without black-start capability in the area, restore other generators, and supply power to key loads.

(2-5) Non-black start power supply start sequence

The micro-grid system adopts a serial recovery strategy, that is, each micro-source is started and merged into the micro-grid one by one in the no-load state, so as to avoid the grid-connected operation of two isolated micro-grids. In order to reduce the voltage and frequency fluctuations during the micro-grid black start process, the starting sequence of the non-black start power supply is: when the micro-grid system is no-load, first start the voltage source type micro-source with voltage regulation and frequency modulation capability, and then gradually start the non-frequency regulation Voltage-capable current-source microsources.

Control strategies include in step (3):

(3-1) Grid-connected inverter control mode

Wind power, photovoltaic and energy storage devices are integrated into the AC synchronous grid through grid-connected inverters. The inverter control modes can be divided into three categories:

1) Inverter PQ control mode, used for double-fed wind turbines and photovoltaic grid-connected state, at this time the power output of the inverter follows the wind/light conditions to achieve the maximum active power output;

2) Inverter V/f control mode, at this time, the micro source is used as the frequency modulation/voltage regulation power supply in the isolated grid to maintain the voltage/frequency stability of the isolated grid;

3) The inverter has a Pf/VQ control mode with drooping characteristics. At this time, the micro-source can have the regulation characteristics of a conventional power supply. The active output varies with the frequency, and the reactive output varies with the voltage amplitude. It has good positive regulation characteristics. It is very beneficial to the power distribution between micro power sources in the case of an isolated network, and no communication is required.

(a) PQ control, the inverter control process is shown in Figure 2.

According to Figure 2, the relationship between the current and voltage of the controller is obtained:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gk</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; ik</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gk</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; gk</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Carry out Park transformation on formula (1), and get:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\\ {\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; iq</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

ω _n is the system frequency.

V _gd , V _gq micro-source grid-connected point d, q axis voltage; V _id , V _iq inverter output d, q axis voltage;

i _gd , i _gq micro-source grid-connected point d, q-axis current;

Set the reference axis as the grid voltage, then v _gq (t) = 0, so the output power of the inverter is: P _mt = v _gd i _gd ; Q _mt = -v _gd i _gq , d, q axis currents are:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; mt</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; mt</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

definition:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}\\ {\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; iq</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The PQ control strategy of the system can be expressed as:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}\\ {\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The reference voltage for PWM pulse width modulation is:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; gd</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}\\ {\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; iq</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; id</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ref</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; gq</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

(b) v/f control

It is used in the island operation mode. At this time, the output voltage amplitude is set to a constant value. The control method is to decompose the voltage vector into d and q axis components, compare their deviations from the set value, and use the PI control link to control the deviation to 0. . The frequency signal is generated by the inverter unit itself.

(c) Pf/VQ control with droop characteristic

The control method is basically the same as PQ. The given Pset and Qset values used to calculate the control reference current and voltage values are included in the deviation between the system frequency and the standard frequency, and the deviation between the output voltage and the given voltage.

Step (4) The voltage of each node of the microgrid and the frequency of the microgrid meet the frequency of the grid, and the voltage stability specifically includes:

(4-1) Voltage stability requirements

Generally speaking, when the generators are running in the large grid, the automatic regulation excitation system (AVR) of each generator will adjust the excitation current output according to the reactive power required by the system, so as to meet the changing demand of reactive power of the grid . The reactive load current is the main reason for the voltage drop at the generator terminal; when the excitation current remains unchanged, the terminal voltage of the generator will decrease with the increase of the reactive current; In order to meet the requirements of power quality and the requirements of power system for voltage stability, the terminal voltage of the generator should basically remain unchanged. This requires that the generator set should be put into the automatic voltage control function of the excitation system AVR when the generator set is running in an isolated grid, so that the excitation current of the generator can be adjusted with the change of the reactive current of the system, so as to maintain the relative stability of the terminal voltage of the generator.

It should be pointed out that: when the unit is running in an isolated grid, the change of grid reactive current must be smaller than the adjustment range of the generator excitation system AVR, otherwise the grid voltage will not be maintained, and may cause tripping or damage to the generator.

(4-2) Requirements for stable operation frequency of isolated microgrid

For non-frequency-regulated units operating in large power grids, the secondary frequency regulation method is generally adopted, that is, after changing the power given value P, the purpose of maintaining system frequency stability is achieved through the regulation characteristics of the governor. When the generator is running in an isolated grid, it is generally necessary to adopt a constant frequency control method, that is, to adjust according to the frequency deviation Δf; when Δf=0, the adjustment ends, that is, the so-called primary frequency regulation method is adopted. Due to the small capacity of the isolated grid, the kinetic energy stored in the rotational inertia is small, so the power grid usually requires the speed regulation system of the main unit to have higher sensitivity, smaller sluggish rate and faster dynamic response, so as to ensure In the case of changing conditions, the system frequency regulation unit can automatically maintain the stability of the grid frequency. The frequency and voltage control functions of the power grid running in isolation are mainly undertaken by the main power generators in the power grid. During the operation of the isolated network, it is necessary to analyze and calculate the power flow and stability of the entire isolated network, formulate a complete isolated network operation plan, implement unified scheduling, and cooperate with all nodes. Only when the stability conditions are met can the isolated network start-up test be successfully carried out , and realize the stable operation of the isolated grid; for the units operating in the isolated grid, their speed regulation, excitation, control, and protection systems should meet the requirements of isolated grid operation.

Claims (4)

1. A black-start control method for a wind-solar-water complementary microgrid, characterized in that the method may further comprise the steps: (1) Read in the basic data of the microgrid, including the microgrid model, microgrid switch status, wind speed, solar radiation intensity data, water regime data of each small hydropower group, and load forecast data of each load node; (2) The distributed power supply that meets the black start conditions is used as the black start power supply candidate unit, otherwise it is used as the activated power supply candidate unit; (3) Sort the candidate units of the black start power supply according to the power, and take one of the units as the black start unit in turn; other distributed power sources in the microgrid are used as the activated units. Participate in isolated grid frequency control to select control strategies and controller parameters, and obtain alternative microgrid black start schemes; (4) Perform simulation calculations on the alternative microgrid black start schemes obtained in step (3) one by one, and judge whether the voltage of each node of the microgrid and the frequency of the microgrid are stable during the black start process of the alternative scheme and the operation of the isolated grid , safety limits and other constraints, if the constraints are met, it will be regarded as a feasible solution, and the optimal solution will be selected among the feasible solutions. 2. method as claimed in claim 1, is characterized in that, described step (2) uses the distributed power supply that satisfies black start condition as black start power supply candidate unit, otherwise as the activated power supply candidate unit; specifically includes: (2-1) The black start conditions that the water turbine unit can meet as the black start power supply unit are: the plant power system is working normally; normal standby conditions are available; the oil level and oil quality of each part of the unit are qualified; The voltage and oil level are within the normal range; the DC control power supply of the outlet switch of the unit is normal; the corresponding high-voltage plant transformer and load switch of the unit are normal; the control of the unit and common parts is normal, and the signal DC power supply is normal; the unit has no defects that affect the start; (2-2) The black start conditions that the energy storage device/photovoltaic power station meets as a black start power supply candidate unit are: The grid-connected inverter of the energy storage device/photovoltaic power station has an islanding operation mode, the anti-islanding detection function exits, and the power station as a whole meets the requirements for commissioning and starting up according to regulations; (2-3) The black start conditions that the wind turbine unit as the black start power supply candidate unit meet are: The emergency power supply of the wind farm can meet the power supply requirements of the fan auxiliary system; the phase sequence of the power supply is correct, and the three-phase voltage is balanced; the steering system is in a normal state, and the anemometer and wind vane are in a normal operating state; The oil pressure and oil level are within the specified range; the oil level and oil temperature of the gearbox are within the normal range; all protection devices are in the correct input position, and the protection settings are in line with the approved setting values; the control power supply is in the on position ; The control computer shows that it is in normal operation; there is no ice on the impeller before manual start; , all the various safety measures established for maintenance have been dismantled. (2-4) Black start power selection a) With energy storage unit: The black start-up power supply of the micro-grid system is the first choice for energy storage devices without intermittent problems. These micro-sources also have all-weather start-up capabilities and are not affected by external factors such as weather. b) Capable of voltage regulation and frequency regulation: the black start power supply not only has voltage source output characteristics, but also has voltage regulation and frequency regulation functions, which can ensure the excitation loss of the distribution transformer and the no-load loss of the AC bus of the microgrid system, and can withstand other non- The short-term power shock when the black starter power supply is started. c) Sufficient reserve capacity: the black-start power supply itself has sufficient power generation capacity to provide start-up power for other power sources without black-start capability in the area, restore other generators, and supply power to key loads. (2-5) Non-black start power supply start sequence Each micro-source is started one by one in the no-load state and merged into the micro-grid to avoid the grid-connected operation of two isolated micro-grids; in order to reduce the voltage and frequency fluctuations in the micro-grid black start process, the start-up sequence of the non-black start power supply is : When the micro-grid system is no-load, first start the voltage source type micro-source with voltage regulation and frequency regulation capability, and then gradually start the current source type micro-source without frequency regulation and voltage regulation capability. 3. as claimed in claim 1 step (3), control strategy specifically comprises: (3-1) Grid-connected inverter control mode Wind power, photovoltaic and energy storage devices are integrated into the AC synchronous grid through grid-connected inverters. The inverter control modes are divided into three categories: 1) Inverter PQ control mode, used for double-fed wind turbines and photovoltaic grid-connected state, at this time the power output of the inverter follows the wind/light conditions to achieve the maximum active power output; 2) Inverter V/f control mode, at this time, the micro source is used as the frequency modulation/voltage regulation power supply in the isolated grid to maintain the voltage/frequency stability of the isolated grid; 3) The inverter has a Pf/VQ control mode with drooping characteristics. At this time, the micro-source can have the regulation characteristics of a conventional power supply. The active output varies with the frequency, and the reactive output varies with the voltage amplitude. It has good positive regulation characteristics. It is very beneficial to the power distribution between micro power sources in the case of an isolated network, and no communication is required. 4. method as claimed in claim 1, is characterized in that, each node voltage of described step (4) microgrid and microgrid frequency meet grid frequency, voltage stability condition, specifically comprise: (4-1) Voltage stability requirements When the isolated grid is running, the automatic voltage control function of the excitation system AVR is used to adjust the excitation current of the generator with the change of the reactive current of the system, so as to maintain the relative stability of the terminal voltage of the generator; (4-2) Requirements for stable operation frequency of isolated microgrid The non-frequency regulation unit running in the large power grid adopts the secondary frequency regulation method, that is, after changing the power given value P, the purpose of maintaining the system frequency stability is achieved through the adjustment characteristics of the governor; when the generator is running in an isolated grid, adopt The constant frequency control method, that is, the one-time frequency modulation method; when the isolated network is running, analyze and calculate the power flow and stability of the entire isolated network, formulate a complete isolated network operation plan, implement unified scheduling, and cooperate with each node to realize the isolated network Stable operation; the unit running in the isolated grid, its speed regulation, excitation, control and protection systems all meet the requirements of isolated grid operation.