JP6991233B2 - Harmonic analysis and maintenance method for dual power supply type wind power generator set grid interconnection - Google Patents

Description

The present invention claims the priority of the Chinese proprietary application No. 201810635901.6, the application number filed with the Chinese Bureau of Interest on June 20, 2018, and the entire contents of the application are incorporated into the present invention by reference. To.

The present invention relates to a technical field of power quality evaluation of a distribution network, for example, to a harmonic analysis and maintenance method of a dual power supply type wind power generator set grid interconnection.

Inner Mongolia Autonomous Region is a vast area, abundant in resources, and is an important energy source for China, a heavy chemical industry, metallurgy, building materials and other raw material production and export bases. Due to the abundance of energy resources and the unique characteristics of economic and social development, the Inner Mongolia Autonomous Region is in a period of rapid development of large-scale resource development and process conversion, and is a heavy-duty type that mainly focuses on new energy such as wind power generation and solar power generation. In addition to the fact that the chemical industrial structure is difficult to fundamentally change in a short period of time, due to the rapid development of new energies such as wind power generation and solar power generation, new energies such as wind power generation and solar power generation will be introduced to the national electric network-inside Mongolia. It is a typical non-linear harmonic source of Tobu Electric Power Co., Ltd. (hereinafter referred to as Monto Electric Network).

A wind power generation system is an energy conversion system that converts wind energy into electrical energy. The development and use of wind energy as a renewable energy has attracted attention in recent years, and a large number of wind power generation systems are already in operation, and various wind power generation technologies are becoming more and more mature. The eastern part of Inner Mongolia is one of the eight 10 million kW level wind power generation bases planned by China, and the technically developable amount of regional wind energy resources is about 110 million kW. In 2015, the cumulative amount of wind power generation in the power supply area of the MEPCO network reached 3.016 billion kWh, an increase of 2.1% from the same period of the previous year. By 2015, the installed capacity of wind power generation in the eastern part of Inner Mongolia reached 815 million kilowatts, an increase of 8.6% from the same period of the previous year, and the installed capacity of wind power generation accounted for 33% of the total installed capacity of the region.

The MEPCO network places a high priority on the development of clean energy, and has traditionally promoted the acceleration of distribution network construction, strengthened power demand side management, strengthened operation management of heat supply equipment, and uncovered sufficient system peaking potential. While continuously delving into the potential of countermeasures, it is promoting a series of innovative countermeasures to promote the consumption of wind power generation in the homeland. During the "Twelfth Five-Year Plan" period, the eastern part of Inner Mongolia overcame disadvantageous conditions such as the characteristics of "large power supply, small load" and the weakness of the self-grid grid frame, took various measures, and consumed wind power generation. Actively promoted and promoted the development of clean energy.

Within the power supply range of the MEPCO network, the distribution network structure is relatively weak. With the rapid construction of ultra-high voltage AC / DC mixed connection distribution networks, a large amount of new energy (wind power generation, solar power generation, etc.) is interconnected, and the power quality problem of the Monto Electric Network becomes more and more prominent. The Mondong Electric Network has a mission of "consecrating clean energy and building a harmonious society", and actively supports the development of the wind power generation industry with the provision of services for the development of new energy as an important political and social responsibility. In recent years, the power generation of new energy for wind power generation in the eastern part of Inner Mongolia has developed rapidly, and many wind farms are connected to the distribution network and are operating. It was the turn, and it was the fastest-developing provincial power distribution network. At the same time, the output power of the new energy grid interconnection power generation has large random fluctuations due to the dynamic fluctuations of the wind speed of the wind farm, and the intermittent power fluctuations adversely affect the power quality of the distribution network. Normally, new energy power generation systems mostly use electrical and electronic equipment grid interconnection, voltage and current harmonics due to electrical and electronic equipment are inevitable, and negative sequence voltage due to asymmetric failure of the distribution network and the distribution network itself. The voltage harmonics interact with the converters in the new energy power plant, where the converters generate additional harmonic currents, and the new energy connections have a significant impact on the power quality of the grid. Therefore, how to analyze the effect of wind farm grid interconnection on the power quality of the grid and determine the distribution of harmonic voltage and harmonic current in the system is still a face-to-face situation. ..

The following is a summary of the subject matter detailed herein. This overview is not intended to limit the scope of the claims.

The present invention provides a method for harmonic analysis and maintenance of a dual power supply type wind power generator set grid interconnection, and is based on a mathematical model of a variable speed / variable pitch double power supply type wind power generator set. Wind farm simulation calculation and harmonic analysis of power system full digital real-time simulation system (Advanced Digital Power System Simulator, ADPSS), and harmonics exceeded the standard by constructing an electromagnetic transient model of a heavy-powered wind power generator set. Based on the electromagnetic transient model of the active filter designed for the case, a large wind farm in the eastern part of Inner Mongolia has important guidance in assessing the harmonic effects of the connection to the grid.

The technical proposal used in the present invention is a method for harmonic analysis and maintenance of a double-powered wind power generator set grid interconnection, which method is based on a mathematical model of a double-powered wind power generator set. , Building an electromagnetic transient model of a double-powered wind power generator set, and using the ADPSS simulation system, electromagnetic transients to the wind farm based on the electromagnetic transient model of the double-powered wind power generator set. A simulation calculation is performed to obtain the harmonic current and harmonic voltage injected from the wind farm into the power grid, and the harmonic current injected into the power grid from the wind farm is compared with the harmonic current threshold. Comparing the harmonic voltage injected into the grid from the farm with the harmonic voltage threshold to determine if the harmonic current or voltage injected into the grid from the wind farm exceeds the standard. When the harmonic current injected from the wind farm into the power grid exceeds the standard, design an active filter, build an electromagnetic transient model of the wind farm including the active filter, and verify the maintenance effect on the harmonic current. And include.

In one embodiment, the mathematical model of the double-powered wind power generator set is as follows.

However, the magnetic flux interlinking of the stator and rotor is expressed as follows.

The equation of motion of the electromagnetic torque of the generator and the rotor is as follows.

In the equation, p represents the differential operator, the subscripts s and r represent the generator stator and rotor, respectively, and L _s , L _r , and L _m represent the self-inductance and rotor of the stator, respectively. Represents the self-inductivity of and the mutual inductance between the stator and the rotor, the subscripts d and q represent the quantities on the d-axis and q-axis at the coordinates of dq0, respectively, and u, i, φ, R , Represents voltage, current, flux linkage and resistance, respectively, ω is the rotor angular velocity, s is the slip ratio, _Te is the electromagnetic torque, and T _m is the mechanical torque of the generator. Yes, T _J is the inertial time constant of the rotor.

In one embodiment, the electromagnetic transient model of the dual power supply type wind generator set includes a generator converter model, a wind power transmission axis control model, a pitch angle control model, and an electric control model, and the generator converter. The model includes an effective control channel and an invalid control channel, the effective control channel outputs an effective current signal with the excitation voltage control signal calculated by the electric control model as an input signal, and the invalid control channel is based on the electric control model. An invalid current signal is output using the calculated effective current control signal as an input signal, and the wind power transmission shaft control model includes two parts, an impeller inertial moment and a generator inertial moment, between the impeller and the generator. By connecting with a spring and using the air power from the impeller and the electromagnetic power from the generator as two inputs and adjusting the pitch angle, the speed deviation between the impeller and the generator rotor can be obtained. , The pitch angle control model includes a first part and a second part, and the first part is a proportional / integration (PI) control process using a generator rotation speed ω _g as an input signal. A pitch control signal is given by, and a pitch correction signal is given by a correction process using the power _source of the generator as an input signal. Finally, the pitch angle β is output by the control / integration process, and in the pitch angle control model, the power _Pord transmitted to the generator is larger than _PMX , or the rotation speed ω _g of the generator is the rotation speed. If greater than the reference value, the wind generator set increases the pitch angle using a fast variable pitch method to reduce the generator rotation speed, and the electrical control model is a wind power management system (Wind Power). The WPMS model includes a Management System (WPMS) model, an excitation controller, and a force factor controller, the WPMS model simulates a wind farm voltage invalidation control, the excitation controller mimics a converter / excitation system, and the force factor controller is a wind force. Monitor the power factor of the generator system interconnection point.

In one embodiment, the method for calculating the harmonic current injected from the wind farm into the distribution network is as follows. After the wind farm is connected, the harmonic current threshold that allows injection into the grid is calculated, and the simulation calculation is performed using the ADPSS simulation platform according to the electromagnetic transient model of the constructed dual power supply type wind generator set. , Obtain the current waveform flowing from the wind farm on the line to the grid interconnection point, perform discrete Fourier transform on the current waveform obtained by the simulation, obtain the harmonic current value injected from the wind farm into the distribution network, and wind. The harmonic current value injected from the farm into the distribution network is compared with the harmonic current threshold value, and if the harmonic current value injected from the wind farm into the distribution network is smaller than the harmonic current threshold value, a pass is shown. If the harmonic current value injected from the wind farm into the distribution network is equal to or greater than the harmonic current threshold value, it is considered that the standard has been exceeded.

In one embodiment, the calculation method of the harmonic voltage injected from the wind farm into the distribution network is as follows. Power Quality-Every time the harmonic voltage content and voltage total harmonic distortion of the grid where the harmonic current injected from the wind farm into the grid is generated at the grid interconnection point, according to the utility grid harmonic specifications. To calculate. However,
The harmonic voltage content of the hth time of the distribution network is as follows.

In the equation, UN is the nominal voltage of the distribution network, _Sk is the three-phase short-circuit capacitance of the common connection point, and I _h is the _hth harmonic current.
The voltage total harmonic distortion is as follows.

In the equation, NRU _h is the hth harmonic voltage content.

The harmonic voltage content of each distribution network induced by the harmonic current injected from the wind farm into the distribution network is compared with the harmonic voltage content threshold of each distribution network, and the distribution network from the wind farm. The harmonic current injected into the common point indicates a pass if the harmonic voltage content induced at the common point is smaller than the harmonic voltage content threshold, and the harmonic current injected from the wind farm into the distribution network has the common point. If the induced harmonic voltage content is greater than or equal to the harmonic voltage content threshold, it is considered to exceed the standard, and the harmonic voltage injected from the wind farm into the distribution network is the voltage total harmonic distortion induced at a common point. When the voltage total harmonic distortion rate induced at a common point is smaller than the voltage total harmonic distortion rate threshold, the harmonic voltage injected from the wind farm into the distribution network is compared with the voltage total harmonic distortion rate threshold. A pass is shown and the harmonic voltage injected from the wind farm into the distribution network is considered to exceed the standard if the voltage total harmonic distortion rate induced at the common point is greater than or equal to the voltage total harmonic distortion rate threshold.

In one embodiment, the method of designing the active filter and constructing an electromagnetic transient model of the wind farm including the active filter removes the harmonic currents in excess of the specifications generated by the wind power generator set and wind power generation. By designing an active filter based on the harmonic current generated by the machine set, installing the active filter on the booster station side of the wind farm, and constructing an electromagnetic transient model of the wind farm equipped with the active filter. be.

The present invention can also understand other aspects by reading and understanding the drawings and detailed description.

The accompanying drawings constituting a part of the present invention are provided to provide a further understanding of the present invention, and exemplary examples and explanations thereof of the present invention are for explaining the present invention. However, the present invention is not inappropriately limited.

It is a flow chart of the harmonic analysis and maintenance method of the dual power supply type wind power generator set grid interconnection. It is the whole block diagram of the electromagnetic transient model of a double power supply type wind power generator set. It is a block diagram of a generator converter control model. It is a block diagram of a pitch angle control model. It is a block diagram of an electric control model. A model of an electromagnetic transient model of a wind farm without an active filter It is a formula diagram. It is a schematic diagram of the current waveform at the common connection point (PCC) of the Karasukai wind farm. In the schematic diagram of the electromagnetic transient model of the wind farm equipped with the active filter be.

Hereinafter, the present invention will be further described with reference to the drawings and examples.

It is clear that the following detailed description is exemplary and is intended to provide further description for the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

It should be noted that the terms used herein are merely for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the invention. The singular form used herein is intended to include the plural unless the context explicitly indicates, and when the terms "included" and / or "included" are used herein. It should be further understood to indicate that there are features, steps, operations, parts, assemblies and / or combinations thereof.

As introduced in Background Technology, there are relatively few studies that fully systematically analyze and verify modeling, simulation, evaluation and maintenance of the harmonic effects of wind power generator sets on distribution networks in related technologies. However, the present invention is to grasp the harmonic effect on the distribution network of the dual power supply type wind power generator set in the eastern part of Inner Mongolia, and to systematically study the verification of modeling, simulation, evaluation and maintenance. Submit the harmonic analysis and maintenance method of the power supply type wind power generator set grid interconnection.

As shown in FIG. 1, embodiments of the present invention provide a method for harmonic analysis and maintenance of a dual powered wind turbine set grid interconnection, which method comprises the following steps.

Step 1 is to build an electromagnetic transient model of the double powered wind turbine set based on the mathematical model of the double powered wind turbine set.

The mathematical model of the double-powered wind power generator set is as follows.

However, the magnetic flux interlinking of the stator and rotor is expressed as follows.

The equation of motion of the electromagnetic torque of the generator and the rotor is as follows.

In the equation, p represents the differential operator, the subscripts s and r represent the generator stator and rotor, respectively, and L _s , L _r , and L _m represent the self-inductance of the stator and rotor, respectively. And the mutual inductance between the stator and the rotor, the subscripts d and q represent the quantities on the d-axis and q-axis at the coordinates of dq0, respectively, and u, i, φ, and R are voltages, respectively. , Current, magnetic flux interlinking and resistance, ω is the rotor angular velocity, s is the slip ratio, _Te is the electromagnetic torque, T _m is the mechanical torque of the generator, and T. _J is the inertial time constant of the rotor.

The steps of electromagnetic transient modeling for the dual powered wind turbine set using the ADPSS platform include engineering data input, network partitioning, task assignment and submission, calculation execution and result output. It is a part. In electromagnetic transient modeling, a schematic method is used to create a schematic of a system model, system graphics are controlled, and parameters are input using a dialog method. The element can be displayed as a single-line diagram or a multi-line diagram, and the display style of the element can be customized by the user. The circuit diagram can be displayed hierarchically and has a "multilayer fitting" structure with a clear structure.

As shown in FIG. 2, the electromagnetic transient model of the double-powered wind power generator set includes a generator converter model, a wind power transmission axis control model, a pitch angle control model, and an electric control model.

As shown in FIG. 3, the generator converter model includes an effective control channel and an invalid control channel, and the effective control channel outputs an effective signal using an effective current control signal calculated by the electric control model as an input signal. , The invalid control channel outputs the invalid signal by using the excitation voltage control signal calculated by the electric control model as an input signal.

The wind power transmission shaft control model includes two parts, an impeller inertial moment and a generator inertial moment, and is connected between the impeller and the generator by using a spring, and the air power from the impeller and the generator. By using the electromagnetic power from the source as two inputs and adjusting the pitch angle, the speed deviation between the impeller and the generator rotor is obtained.

As shown in FIG. 4 , the pitch angle control model includes a first portion and a second portion, and the first portion uses a generator rotation speed ωg as an input signal and a pitch control signal by a PI control process. Further, a pitch correction signal is given by the correction process using the power Pord of the generator as an input signal, and the second part is a PI control / integration process using the sum of the pitch control signal and the pitch correction signal as an input. Finally, the pitch angle β is output.

In the pitch angle control model, if the power _Pord transmitted to the generator is greater than _PMX or the generator rotational speed _ωg is greater than the rotational speed reference value, the wind turbine set is a generator. The pitch angle is increased by using the method of rapid variable pitch so as to decrease the rotation speed of.

As shown in FIG. 5 , the electrical control model includes a WPMS model, an excitation controller, and a power factor controller, the WPMS model simulates wind farm voltage invalidation control, and the excitation controller is a converter / excitation system. Simulating, the power factor controller monitors the power factor at the interconnection point of the wind turbine system.

In step 2, an electromagnetic transient simulation calculation is performed on the wind farm using the ADPSS simulation system to obtain the harmonic current injected into the distribution network from the wind farm and the generated harmonic voltage.

The calculation method of the harmonic current injected from the wind farm into the distribution network is as follows. Based on the Chinese standard GB / T14549-1993 << Power Quality-Utility Grid Harmony >>, the principle of harmonic current allocation at the common connection point PCC is injected into the distribution network from each user at the same common connection point. The harmonic current allowance is assigned by this user as a percentage of the contracted capacity at that point to the capacity of the power supply facility at its common connection point, allowing injection into the grid after the wind farm is connected. The harmonic current threshold to be calculated is calculated using the ADPSS simulation platform according to the electromagnetic transient model of the constructed double power supply type wind generator set, and the current waveform flowing from the wind farm on the line to the grid interconnection point is calculated. The obtained line is a line between the wind farm and the substation to which the wind farm is connected, and the current waveform obtained by the simulation is subjected to discrete Fourier transform (DFT) and injected from the wind farm into the distribution network. The discrete Fourier transform (DFT) of the N-point sequence obtained by obtaining the harmonic current value is as follows.

The calculation method of the harmonic voltage generated after the distribution network is connected to the wind farm is as follows. Based on the Chinese standard GB / T14549-1993 << Power Quality-Utility Grid Harmonics >>, the harmonic current injected into the distribution network from the wind farm contains the hth harmonic voltage of the distribution network generated at the grid interconnection point. The rate is calculated and the result is as follows.

In the equation, UN is the nominal voltage of the distribution network, _Sk is the three-phase short-circuit capacitance of the common connection point, and I _h is the _hth harmonic current.
The voltage total harmonic distortion is as follows.

In step 3, the harmonic current and the harmonic current threshold are compared, the harmonic voltage injected into the grid from the wind farm and the harmonic voltage threshold are compared, and the harmonic injected from the wind farm into the grid. It is to determine whether the wave current or harmonic voltage exceeds the standard.

In the step of comparing the obtained harmonic current and the threshold value, the harmonic current value injected into the distribution network from the wind farm and the harmonic current threshold value are compared, and the harmonics injected from the wind farm into the distribution network are compared. If the current value is smaller than the harmonic current threshold, it indicates a pass, and if the harmonic current value injected into the distribution network from the wind farm is equal to or higher than the harmonic current threshold, it is considered to exceed the standard. include.

The step of comparing the obtained harmonic voltage with the threshold is the harmonic voltage content and each harmonic of the grid where the harmonic current injected from the wind farm into the grid is generated at the grid interconnection point. Compared with the voltage content threshold, the harmonic current injected from the wind farm into the distribution network indicates a pass if the harmonic voltage content induced at the common point is smaller than the harmonic voltage content threshold. The harmonic current injected from the wind farm into the distribution network is considered to exceed the standard if the harmonic voltage content induced at the common point is equal to or higher than the harmonic voltage content threshold, and is injected from the wind farm into the distribution network. The harmonic voltage is the voltage induced at the common point. The total harmonic distortion rate and the voltage total harmonic distortion rate threshold are compared, and the harmonic voltage injected from the wind farm into the distribution network is the total voltage induced at the common point. If the harmonic distortion rate is smaller than the voltage total harmonic distortion rate threshold, it indicates a pass, and the harmonic voltage injected into the distribution network from the wind farm is the voltage total harmonic distortion rate induced at a common point. If it is equal to or higher than the wave distortion rate threshold, it is considered that the standard has been exceeded.

When the harmonic current injected from the wind farm into the distribution network exceeds the standard, an active filter is designed, a wind farm electromagnetic transient model including the active filter is constructed, and the maintenance effect on the harmonic current is verified.

The active filter is designed based on the harmonic current generated by the wind power generator set by removing the harmonic currents that exceed the standard generated by the wind power generator set, and the active filter is used as a booster station in the wind farm. Build an electromagnetic transient model of the wind farm mounted on the side and fitted with an active filter, and perform simulation calculations again to obtain the harmonic currents injected from the wind farm into the grid after the active filter is mounted. , Compare the harmonic currents injected into the distribution network from the wind farms before and after the active filter is installed, and verify the effectiveness of the electromagnetic transient model of the wind farm with the active filter installed.

There are relatively few studies that fully systematically analyze and verify modeling, simulation, evaluation and maintenance of the harmonic effects of wind turbine sets on the grid in related technologies. On the other hand, the harmonic analysis and maintenance method of the dual power supply type wind power generator set grid interconnection according to the present invention is based on the mathematical model of the variable speed / variable pitch double power supply type wind power generator set. Inner Mongolia based on ADPSS wind farm simulation calculations and harmonic analysis, as well as an active filter electromagnetic transient model designed when harmonics exceed standards by building an electromagnetic transient model for a heavy-fed wind power generator set. Large-scale wind farms in the eastern region have important guidance in assessing the effects of harmonics from connections to distribution networks.

In order for those skilled in the art to better understand the present invention, specific examples are illustrated below, modeling and analysis are performed using the Inner Mongolia Huaden Katsu Flag Wutaohai Wind Farm as an example, and the Inner Mongolia Huaden Katsu Flag Wutaohai Wind. The planned installed capacity of the farm is 350 MW, it is constructed with two steps, the installed capacity of the first stage is 49.5 MW, the second stage is located on the south side of the first stage, and the installed capacity is It is 300 MW. Inner Mongolia Huadian Banner Wutaohai Wind Farm occupies an area of 98km ³ and is equipped with 200 1500kW wind power generator sets with an installed capacity of 300MW.

The electromagnetic transient model constructed in the ADPSS program is shown in FIG.

1. Harmonic calculation analysis (1) Harmonic current calculation and conclusion Windfarm selected 234 1500kW double feed type asynchronous motors and connected them to the system at a voltage level of 220kV.
When the short-circuit capacitance is Sk1, the allowable value of the harmonic current at the _hth time is as follows.

In the formula, Sk1 is the minimum short-circuit capacity at the common connection point, _Sk2 is the reference short-circuit capacity, and _Ihp is defined in the Chinese standard GB / _T14549-1993 << Power Quality-Utility Grid Harmonics >>. It is the corresponding allowable value of the harmonic current of the hth time, and I _h is the allowable value of the harmonic current of the _hth time when the short circuit capacitance is Sk1.

Based on the Chinese standard GB / T14549-1993 << Power Quality-Utility Grid Harmonics >>, the principle of harmonic current allocation at the common connection point PCC is injected into the grid from each user at the same common connection point. The harmonic current allowance is assigned by this user as a ratio of the contracted capacity at that point to the capacity of the power supply facility at its common connection point.

The h-th harmonic current permissible value of the i-th user at the common connection point is as follows.

However, S _i is the power usage contract capacity of the i-th user, St is the power supply equipment capacity at the common connection point, α is the phase superposition coefficient, and S _{i =} 350 MVA (No. 1). (Wind power generation capacity of 2 stairs), and St ₌ 1524 MVA.

A common connection point of the wind farm in the wind farm obtained by performing harmonic analysis simulation calculation using the ADPSS program while referring to the actual situation of the wind farm in the wind farm according to the constructed wind farm electromagnetic transient model. The current waveform in Point of Common Coupling ( PCC ) is shown in FIG.

The waveform in the time domain obtained by the simulation is DFTed, and the harmonic current value injected into the distribution network from the Karasukai wind farm is obtained. Based on the Chinese standard, the harmonic current threshold that allows injection from the Wutaohai wind farm is calculated in common, and the harmonic current value and threshold generated in the wind farm calculated by the electromagnetic transient model of the wind farm. If the harmonic current value generated in the wind farm is smaller than the threshold value, it indicates a pass, and if the harmonic current value generated in the wind farm is greater than or equal to the threshold value, it is considered to have exceeded the standard. The comparison results are shown in Table 1.

According to the calculation result, the harmonic current injected from the wind farm calculated this time to the common point is large at the 3rd, 5th, and 7th times, exceeds the harmonic current threshold, and it is necessary to install the corresponding active filter. ..

(2) Calculation and conclusion of harmonic voltage The harmonic voltage content of the hth time of the distribution network is as follows.

In the equation, UN is the nominal voltage of the distribution network, UN = 220 kV, _Sk is the three _- phase short-circuit capacitance of the common connection point, _Sk = 1987 MVA, and I _h is the _hth time. Harmonic current of.

The voltage total harmonic distortion is as follows.

In the equation, NRU _h is the hth harmonic voltage content.

The harmonic content and voltage total harmonic distortion rate of the distribution network induced by the harmonic current generated in the wind farm calculated above at the common point, and the 220 kV utility grid specified in the Chinese standard each time. Comparing the harmonic voltage content and the voltage full harmonic distortion rate threshold, the harmonic voltage content is smaller than the harmonic voltage content rate threshold, and the voltage full harmonic distortion rate is smaller than the voltage full harmonic distortion rate threshold. A small value indicates a pass, otherwise it is considered to exceed the standard, and specific comparison results are shown in Table 2.

The following is a comparison result between the voltage total harmonic distortion induced by the harmonic current injected from the wind farm into the distribution network in common and the voltage total harmonic distortion threshold of the 220 kV utility grid specified in the Chinese standard. Shown in the table.

According to the calculation results, the harmonic voltage content of each distribution network induced by the common points of the Wuyi Wind Farm passed, did not exceed the standard, and the 220kV voltage total harmonic distortion also passed. Yes, it meets the requirements of Chinese standards.

2. Harmonic maintenance of the wind farm (1) Active filter design of the wind farm and its model The Karasukai wind farm has a certain harmonic component at the common connection point, and the relatively large harmonic component is 3. This is the 5th and 7th harmonics, and the largest harmonic current is the 3rd harmonic. When connected to the grid, the busbars at each level experienced constant voltage distortion, but were within acceptable limits.

The harmonic currents of the 3rd, 5th, and 7th times injected from the Wuyi Wind Farm to the common connection point (Yangju Mizomon Station, 220kV bus bar) are relatively large, and all of them exceed the permissible value. The third harmonic current is the largest. If necessary, we designed an active filter that aims to remove the third, fifth, and seventh harmonic currents, and installed it on the 35kV side of the booster station of the wind farm, as well as the wind farm equipped with the active filter. The electromagnetic transient model of is constructed, and as shown in FIG. 8 , there is an active filter in the red frame. The harmonic current generated in the wind farm is corrected using the electromagnetic transient model of the wind farm equipped with the active filter, and the harmonic current is injected into the common connection point of the harmonic source and the induced harmonic voltage distortion is corrected. Improve power quality by removing or reducing.

(2) Harmonic analysis after the active filter is attached After the active filter is attached, the harmonic analysis calculation of the Karasukai wind farm is performed again. After the active filter is installed, the harmonic current injected from the Karasukai wind farm to the common connection point (Yangju groove gate station, 220kV bus bar) is calculated by simulation, compared with the threshold value, and the comparison result is compared. , Table 4.

Compare the harmonic currents injected into the common connection point (Yangju Mizomon Station, 220kV bus bar) from the Wuyi Wind Farm after the active filter is installed, and compare before the active filter is installed. All of them are reduced, and both are within the permissible range. Among them, the third harmonic current was reduced from the original 5.7A to 1.7A.

According to the above simulation calculation analysis, the active filter designed in the present invention effectively reduces the harmonic current component injected from the Karasukai wind farm into the distribution network, and the harmonic voltage content and total at each time. By reducing the harmonic voltage distortion factor, the harmonic effects of connecting the wind farm to the system meet the Chinese standard harmonic standards.

Claims (5)

Building an electromagnetic transient model of a double-powered wind turbine set based on a mathematical model of a double-powered wind power generator set,
According to the electromagnetic transient model of the dual power supply type wind power generator set, the electromagnetic transient simulation calculation is performed on the wind farm using the power system full digital real-time simulation system ADPSS, and the harmonics injected from the wind farm into the distribution network are performed. Obtaining current and harmonic voltage,
The harmonic current injected into the distribution network from the wind farm and the harmonic current threshold are compared, the harmonic voltage injected into the distribution network from the wind farm and the harmonic voltage threshold are compared, and the power is distributed from the wind farm. Determining whether the harmonic current or harmonic voltage injected into the network exceeds the standard, and
When the harmonic current injected from the wind farm into the distribution network exceeds the standard, design an active filter, build a wind farm electromagnetic transient model including the active filter, and verify the maintenance effect on the harmonic current. Including and
The electromagnetic transient model of the dual power supply type wind power generator set includes a generator converter model, a wind power transmission axis control model, a pitch angle control model, and an electric control model.
The generator converter model includes an effective control channel and an invalid control channel, and the effective control channel outputs an effective current signal using an exciting voltage control signal calculated by the electric control model as an input signal, and the invalid control channel is used. The channel outputs an invalid current signal using the effective current control signal calculated by the electric control model as an input signal.
The wind power transmission axis control model includes a moment of inertia of an impeller and a moment of inertia of a generator, and uses air power from an impeller and electromagnetic torque from a generator as two inputs and adjusts the pitch angle to adjust the blades. Obtaining the speed deviation between the car and the generator rotor,
The pitch angle control model includes a first part and a second part, and the first part gives a pitch control signal by a proportional / integral PI control process with a generator rotation speed ω _g as an input signal. Further, the power _Pord of the generator is used as an input signal, and the pitch correction signal is given by the correction process. When the pitch angle β is output to, and in the pitch angle control model, the power _Pord of the generator is larger than _PMX , or the rotation speed ω _g of the generator is larger than the reference value of the rotation speed, the above two The heavy feed wind generator set uses a fast variable pitch method to increase the pitch angle so as to reduce the rotational speed of the generator.
The electrical control model includes a wind power management system WPMS model, an excitation controller, and a power factor controller, the WPMS model simulates wind farm voltage invalidation control, and the excitation controller simulates a converter / excitation system. The power factor controller is a method for harmonic analysis and maintenance of a double-powered wind power generator set grid interconnection that monitors the power factor at the wind power generator grid interconnection point . The mathematical model of the double-powered wind power generator set is as follows.

However, the magnetic flux interlinking of the stator and rotor is expressed as follows.

The equation of motion of the electromagnetic torque and rotor of the generator is as follows.

In the equation, p represents the differential operator, the subscripts s and r represent the stator and rotor of the generator, respectively, and L _s , L _r , and L _m represent the self-inductance and rotor of the stator, respectively. Represents the self-inductivity of and the mutual inductance between the stator and the rotor, the subscripts d and q represent the quantities on the d-axis and q-axis at the coordinates of dq0, respectively, and u, i, φ and R represent the quantities on the d-axis and q-axis, respectively. , Represents voltage, current, flux linkage and resistance, respectively, ω is the rotor angular velocity, s is the slip ratio, _Te is the electromagnetic torque, and T _m is the mechanical torque of the generator. The method according to claim 1, wherein T _J is an inertial time constant of the rotor. Obtaining the harmonic current injected into the grid from the wind farm
Calculating the harmonic current threshold that allows injection into the grid after the grid is connected to the wind farm
According to the electromagnetic transient model of the double-fed wind power generator set constructed, the simulation calculation is performed using the ADPS S to obtain the simulation current waveform flowing from the wind farm on the line to the grid interconnection point.
The simulation current waveform is subjected to the discrete Fourier transform to obtain the harmonic current value injected from the wind farm into the distribution network.
The harmonic current value injected from the wind farm into the distribution network is compared with the harmonic current threshold value, and if the harmonic current value injected from the wind farm into the distribution network is smaller than the harmonic current threshold value, the result is passed. The method according to claim 1, wherein if the harmonic current value injected into the distribution network from the wind farm is equal to or greater than the harmonic current threshold value, it is considered that the specification has been exceeded. Obtaining the harmonic voltage injected into the grid from the wind farm
Power Quality-Calculates the harmonic voltage content and voltage total harmonic distortion rate each time the harmonic current injected from the wind farm into the grid at the grid interconnection point is generated according to the utility grid harmonic specification standard. However,
The harmonic voltage content of the hth time of the distribution network is as follows.

In the equation, UN is the nominal voltage of the distribution network, _Sk is the three-phase short-circuit capacitance of the common connection point, and I _h is the _hth harmonic current.
The voltage total harmonic distortion is as follows.

In the equation, NRU _h is the hth harmonic voltage content.
The harmonic voltage injected from the wind farm into the distribution network is compared with the harmonic voltage content of each distribution network induced at a common point and the harmonic voltage content threshold of each distribution network, and the power is distributed from the wind farm. The harmonic current injected into the network is acceptable if the harmonic voltage content induced at the common point is smaller than the harmonic voltage content threshold, and the harmonic current injected from the wind farm into the distribution network is common. If the harmonic voltage content induced at the point is greater than or equal to the harmonic voltage content threshold, it is considered to exceed the standard.
The voltage total harmonic distortion factor induced by the harmonic voltage injected into the distribution network from the wind farm and the voltage total harmonic distortion factor threshold are compared, and the harmonics injected from the wind farm into the distribution network are compared. The voltage indicates a pass when the voltage total harmonic distortion factor induced at the common point is smaller than the voltage total harmonic distortion factor threshold, and the harmonic voltage injected from the wind farm into the distribution network is the voltage induced at the common point. The method of claim 1, wherein if the total harmonic distortion is greater than or equal to the voltage total harmonic distortion threshold, it is considered to exceed the standard. Designing an active filter and building an electromagnetic transient model of a wind farm that includes an active filter further includes designing the active filter and building an electromagnetic transient model of a wind farm that includes an active filter.
The active filter is designed based on the harmonic current generated by the wind power generator set by removing the harmonic current that exceeds the standard generated by the wind power generator set, and the active filter is used as a booster station of the wind farm. The method of claim 1, comprising mounting on the side and constructing an electromagnetic transient model of a wind farm that includes an active filter.

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