KR100985921B1 - wind power system using doubly fed induction generator and control method thereof - Google Patents

Abstract

Disclosed is a double excitation induction wind power generation system and a control method thereof. The dual excitation induction wind power generation system according to the present invention uses a matrix converter and an offset voltage connected between the rotor and the power system of the winding induction generator to control the output or rotational speed of the winding induction generator connected to the blade. It may include a controller for controlling the matrix converter through a voltage modulation scheme. In addition, the control method of the wind power generation system according to the present invention comprises the steps of estimating the magnetic flux and slip angular velocity of the rotor of the winding-type induction generator connected to the blade, based on the estimated flux and slip angular velocity of the winding induction generator Calculating a torque and generating a reference current for controlling the active power of the rotor based on the torque; generating an output phase voltage command of the rotor based on the generated reference current; and generating the output phase voltage command And generating a gate signal for switching control of the matrix converter based on the measured input phase voltage of the stator of the wound induction generator. Through this, the present invention can increase the efficiency of the system and reduce the size of the system.

Wind power generation, induction generator, power system, matrix converter, gate signal

Description

Dual excitation induction wind power generation system and control method thereof {wind power system using doubly fed induction generator and control method}

The present invention relates to a double excitation induction wind power generation system and a control method thereof.

In general, a wind power generation system refers to a system that converts kinetic energy of wind into mechanical energy by using various types of windmills, and obtains power by driving a generator with mechanical energy. Such a wind power generation system is a renewable energy source with many advantages, such as environmentally friendly and unlimited resources.

The wind power generation system can be divided into the method of directly supplying the generated power to the user and the system of supplying power to the power system. The current trend is to build a large-scale complex to produce electricity and operate it in conjunction with the electricity grid.

The easiest way to link wind farms to power systems is to use squirrel cage induction generators. However, this method consumes reactive power, and this reactive power varies in real time according to the amount of active power generated. Therefore, to compensate for this, a staircase reactive power compensator combining a mechanical breaker and a capacitor bank was initially installed and operated, and recently, an inverter type reactive power compensator capable of continuous compensation is installed and operated.

The double-fed induction generator uses a winding induction generator, the stator is connected directly to the power system and the rotor is connected to the power system through a back-to-back converter. In this way, even if the speed of the rotor changes with the wind speed, it is possible to supply power to the grid at a constant voltage and frequency, and to control the power factor of the combined point of wind power generation. Therefore, there is no need to install a separate device for compensating reactive power.

However, the dual excitation induction system uses a back-to-back converter that converts low-frequency alternating current from the rotor into 60Hz commercial alternating current, which requires a large three-phase switching loss due to the AC-DC-AC three-stage power conversion. The disadvantage is that the system scale is large.

The present invention has been made to solve the above problems, by using an energy-efficient matrix converter to connect the rotor of the winding induction generator to the power system, the double excitation induction to increase the efficiency of the system It is to provide a type wind power generation system and a control method thereof.

In addition, the present invention provides a dual excitation induction wind power generation system and a control method thereof that can reduce the size of the system by using a matrix converter with a simple hardware configuration to connect the rotor of the winding induction generator to the power system. It is.

To this end, the dual excitation induction wind power system according to an aspect of the present invention is a matrix connected between the rotor and the power system of the winding induction generator to control the output or rotational speed of the winding induction generator connected to the blade It may include a controller for controlling the matrix converter through a voltage modulation scheme using a converter and an offset voltage.

The controller is a parameter estimator for estimating magnetic flux and slip angular velocity with respect to the rotor of the wound induction generator, and calculates torque of the wound induction generator based on the estimated flux and slip angular velocity. A reference current generator for generating a reference current for controlling active power; a current controller for generating an output phase voltage command of the rotor based on the generated reference current; and the winding type measured with the generated output phase voltage command. It may include a voltage modulator for generating a gate signal for switching control of the matrix converter based on the input phase voltage of the stator of the induction generator.

The voltage modulator generates a carrier and an offset voltage within a switching period based on the input phase voltage, generates a pole voltage command based on the generated offset voltage and the output phase voltage command, and generates the pole voltage command and the carrier. The gate signal for controlling the matrix converter may be generated by comparing the? At this time, the voltage modulation unit the carrier within one switching period T _s of at least two switching intervals in accordance with the phase angle of the input voltage T divided by ₁ and T _2, the switching period T ₁ and T ₂ for each phase and Each of the offset voltages may be generated.

The controller according to the present invention may further include a PWM generator for generating a pulse width modulation (PWM) pulse according to the generated gate signal and a gate driver for driving the gate of the matrix converter according to the generated PWM pulse.

In addition, the dual excitation induction wind power generation system according to the present invention may further include a circuit breaker connected between the stator of the winding induction generator and the power system.

According to another aspect of the present invention, there is provided a control method of a wind power generation system, the method comprising: estimating a magnetic flux and a slip angular velocity of a rotor of a winding type induction generator connected to a blade, based on the estimated magnetic flux and slip angular velocity; Calculating a torque of the generator and generating a reference current for controlling the active power of the rotor based on the torque of the generator; generating a voltage command of the output phase of the rotor based on the generated reference current; and generating the generated output. And generating a gate signal for switching control of the matrix converter based on the phase voltage command and the input phase voltage of the stator of the wound induction generator.

The generating of the gate signal may include generating a carrier and an offset voltage within a switching period based on the input phase voltage, generating a pole voltage command based on the generated offset voltage and the output phase voltage command. And comparing the pole voltage command with the carrier to generate a gate signal for controlling the matrix converter. Generating the carrier and offset voltage divides one switching period T _s for each phase into at least two switching periods T ₁ and T ₂ according to the phase angle of the input voltage, and within the switching periods T ₁ and T ₂ . Each of the carrier and the offset voltage may be generated at.

In addition, the control method of the wind power generation system according to the present invention includes generating a pulse width modulation (PWM) pulse according to the generated gate signal and receiving the generated PWM pulse to drive the gate of the matrix converter accordingly. It may further comprise a step.

Hereinafter, a dual excitation induction wind power generation system and a control method thereof according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 12C.

The present invention proposes a dual excitation induction wind power generation system using a matrix converter. That is, the present invention can use a matrix converter having a high energy efficiency and a simple hardware configuration to connect the rotor of the wound induction generator to the power system.

1 is an exemplary view showing the configuration of a schematic wind power generation system according to an embodiment of the present invention.

As shown in FIG. 1, a system according to the present invention comprises a blade 110, a gear box 120, a generator 130, a breaker or a circuit breaker 140. , A matrix converter 150, a controller 160, and a power system or grid 170.

The blade 110 may transmit power to a generator by rotating by receiving wind energy.

Since the gearbox 120 has a low rotation speed, the gearbox 120 may be positioned between the blade 110 and the rotor of the generator 130 to increase the rotation speed. Depending on the wind power generation system, the gears may not be used, but in this case, a high pole number generator 130 may be used. For example, a winding type induction generator having 4 poles or 6 poles may be used.

In general, the generator 130 is a component that generates electricity by using the rotational force after the energy of the wind is converted to the rotational force by the rotor is an important factor that determines the efficiency of electrical energy generation or the quality of electricity. Synchronizers or inductors are largely used as such generators. The synchronous machines can be divided into winding field type and permanent magnet type according to the field type, and the inductor can be classified into cage type and winding type according to the structure of the rotor. In particular, the winding induction generator, winding induction generator (doubly fed induction generator (DFIG)) can be installed in a place characterized by variable wind speed and excellent mechanical characteristics compared to the synchronous generator or synchronous generator, such as wind power generation This is especially useful for systems.

The breaker 140 may be connected between the stator of the winding type induction generator 130 and the power system 170.

The matrix converter 150 may be connected between the rotor and the power system of the winding induction generator to control the output or rotational speed of the winding induction generator, and may transmit bidirectional power and adjust the power factor of the input current. Due to the advantage of not needing a DC link circuit, it may be a circuit that can obtain an AC output of a variable voltage and a variable frequency from a commercial three-phase AC power source without DC conversion. This will be described in more detail with reference to FIG. 2.

2 is an exemplary view showing a detailed structure of the three-phase matrix converter shown in FIG.

As shown in FIG. 2, the three-phase matrix converter according to the present invention includes nine bidirectional AC switches, and can control them instantaneously. There is no independent reflux path for the load current and inputs without a DC link circuit. The output can be connected directly.

At this time, in the switch of the matrix converter, in order to reliably operate the commutation of the configured switch, a complicated control method is required as compared to the existing power converter, and a protection circuit such as a clamp circuit or a snubber circuit is required. This matrix converter can have two basic rules for commutation.

That is, considering only the input two phases for one output side, the two bidirectional switches should not be kept on at the same time in the switching of the matrix converter, which leads to the destruction of the switching element due to the overcurrent caused by the line short circuit. Because. In addition, two bidirectional switches should not be turned off at the same time because inductive loads have no reflux path and cause overvoltage, which affects the matrix converter. Therefore, during the switching operation of the matrix converter, one output must operate to connect only one switch of the two inputs.

In addition, the controller 160 may control the matrix converter, that is, the switching of the matrix converter. The operation principle of the present invention configured as described above will be described with reference to FIGS. 3 to 10.

3 is an exemplary view showing a detailed structure of a controller of the matrix converter shown in FIG.

As shown in FIG. 3, the controller of the matrix converter according to the present invention includes a parameter estimator 310, a reference current generator 320, a current controller 330, a voltage modulator 340, and a pulse width modulation. A generator 350, a gate driver 360, and a phase locked loop (PLL) unit 370 may be included.

The parameter estimator 310 may estimate magnetic flux and slip angular velocity of the stator and the rotor of the induction generator. The reference current generator 320 may calculate the torque of the induction generator, the active power of the stator and the rotor, and the reactive power based on the parameters estimated by the parameter estimator 310. The reference current generator 320 may generate a reference current for controlling the torque of the induction generator by setting the reference value of the active power of the rotor.

The current controller 330 may generate an output phase voltage command of the rotor based on the generated reference current.

The voltage modulator 340 outputs stator input phase voltages V _ga , V _gb , V _gc measured by the output phase voltage commands V _as ^* , V _bs ^* , V _cs ^* and PT (Potential Transformer). The voltage modulation may be performed based on the voltage modulation method, and the voltage modulation method using the offset voltage may be applied.

At this time, the voltage modulation method using the offset voltage is the pole voltage command (V _an ^* , V _bn ^* , V _cn ^* ) by adding the offset voltage V _sn to the output phase voltage commands V _as ^* , V _bs ^* , V _cs ^* . ), And then a method of generating a gate signal by comparing the pole voltage command with a carrier.

In this case, the PLL unit 370 may define MAX, MID, and MIN from the three-phase voltage of the input side for generating the carrier.

The PWM generator 350 generates a PWM pulse or a PWM switching signal for switching control of the matrix converter according to the generated gate signal, so that the gate driver 360 drives each gate of the matrix converter according to the generated PWM pulse. Switching control.

4 is an exemplary view showing a control method of a wind power generation system according to an embodiment of the present invention.

인 블레이드에 풍속

인 바람이 불어오는 경우를 가정하면, 바람으로부터 흡수되는 전체 에너지 즉, 블레이드에서 변환되는 기계적 에너지

는 다음의 [수학식 1]과 같이 표현될 수 있다.As shown in Figure 4, first, the radius of rotation

Wind speed on the blade

Assuming that the wind is blowing, the total energy absorbed from the wind, ie the mechanical energy converted at the blade

May be expressed as Equation 1 below.

[Equation 1]

는 블레이드의 회전 단면적[

]으로 을

의미하고,

는 공기의 밀도로서 대략 1.225[

]을 의미할 수 있다. 또한,

는 출력계수를 의미하고,

는 주속비(tip speed ratio)를 의미하며,

는 블레이드의 피치각을 의미할 수 있다.here,

Is the rotational cross-sectional area of the blade [

To

Mean,

Is approximately 1.225 [

] Can mean. Also,

Means output coefficient,

Means the tip speed ratio,

May mean a pitch angle of the blade.

는 풍속과 회전속도의 비율로서 다음의 [수학식 2]와 같이 표현할 수 있다.At this time, the main speed ratio

Is the ratio of wind speed and rotation speed and can be expressed as shown in [Equation 2].

[Equation 2]

는 블레이드의 회전 각속도를 의미하고,

는 블레이드의 회전자 반경을 의미할 수 있다.here,

Means the rotational angular velocity of the blade,

May refer to the rotor radius of the blade.

는 다음의 [수학식 3]과 같이 표현할 수 있다.Meanwhile, torque generated from the blade

Can be expressed as Equation 3 below.

&Quot; (3) "

As such mechanical energy is transferred to the induction generator, the three-phase state equation for the voltage of the stator and the rotor is modeled, i.e., transformed, in the equivalent circuit of the induction generator in which both the stator and the rotor windings are connected by Y. When expressed as shown in Equation 4 below.

&Quot; (4) "

[v]

[v]

는 전압을,

는 저항을,

는 전류를, 그리고

는 자속을 의미할 수 있다. 예를 들면,

라고 표기하면 고정자 d축 전압을 정지 좌표계로 표현한 것이다. 또한,

은 유도발전기의 전기적 회전각속도를 의미하는데,

는 좌표계에 따라서 다른 값을 대입 예컨대, 정지 좌표계에서는

을, 동기 좌표계에서는

(동기 각속도)를 대입할 수 있다.Here, the superscript g means a reference coordinate system, and thus, the superscript g may be replaced with 's' for a stationary coordinate system and 'e' for a synchronous coordinate system. In the subscripts, d and q may refer to the dq coordinate axis, and in the subscripts, s and r may refer to the stator and the rotor, respectively.

The voltage,

Resistance,

Is the current, and

Can mean magnetic flux. For example,

In this case, stator d-axis voltage is expressed by the static coordinate system. Also,

Is the electrical rotational angular velocity of the induction generator,

Assigns a different value depending on the coordinate system. For example,

In the synchronous coordinate system

(Synchronous angular velocity) can be substituted.

Based on the above [Equation 4], the controller can estimate the relationship between the magnetic flux and current of the stator and rotor of the winding induction generator (S410), because the magnetic flux of the induction generator is proportional to the product of impedance and current. And the magnetic flux of the rotor can be expressed as Equation 5 below.

[Equation 5]

[wb]

[wb]

Here, L _m means the magnetizing inductance of the induction generator (magnetizing inductance), L _s means the inductance of the stator, L _r may mean the inductance of the rotor.

In this case, the torque of the induction generator means a mechanical force generated or consumed in the induction generator, this mechanical force can be expressed as shown in Equation 6 below.

&Quot; (6) "

의 관계를 가질 수 있다.Where the electrical rotational angular velocity ω _r and the mechanical rotational angular velocity ω _rm are

May have a relationship of

Thus, the torque of the induction generator is derived from Equation 6 and expressed as the current and magnetic flux of the stator and the rotor based on Equation 5 as shown in Equation 7 below.

[Equation 7]

The current and voltage of the stator converted to the d-q coordinate system in Equation 4 above can express the active power and the reactive power of the stator as shown in Equation 8.

[Equation 8]

Similarly, the active power and reactive power of the rotor can be expressed by Equation 9 by using the current and voltage of the rotor converted into the d-q coordinate system.

[Equation 9]

The controller may generate a reference current for controlling active power and reactive power of the stator and the rotor, respectively, based on the two Equations 7 and 8 generated at step S420.

The controller generates the output phase voltage commands V _as ^* , V _bs ^* , V _cs ^* of the rotor based on the generated reference current (S430), and the input phase voltages V _ga , V _gb , of the stator measured through PT. The carrier and the offset voltage are generated within the switching period based on V _gc (S440), and the pole voltage command V _an ^* based on the generated offset voltage V _sn and the output phase voltage commands V _as ^* , V _bs ^* , and V _cs ^* . , V _bn ^* , V _cn ^* may be generated (S450). Thus, the controller may generate a gate signal for switching control of the matrix converter by comparing the generated pole voltage commands V _an ^* , V _bn ^* , V _cn ^* with the carrier (S460).

In this case, if the switching period T _s is divided into T ₁ and T ₂ , and the offset voltage in the T ₁ section is defined as V _sn1 , and the offset voltage in the T ₂ section is defined as V _sn2 ,

1) a phase pole voltage command in T ₁ section V _an1 ^* = V _as ^* + V _sn1 , 2) a phase pole voltage command in T ₂ section V _an2 ^* = V _as ^* + V _sn2 , 3) T ₁ b the pole voltage command in the interval ^{_{V bn1 * = V bs * +}} V bn1, 4) b the pole voltage command in the T ₂ period ^{_{V bn2 * = V bs * +}} V bn2, 5) T of c from the _first section Phase pole voltage command V _cn1 ^* = V _cs ^* + V _cn1 , 6) The c phase pole voltage command V _cn2 ^* = V _cs ^* + V _cn2 in the T ₂ interval can be defined.

5 is an exemplary view for explaining the principle of the voltage modulation method using an offset according to an embodiment of the present invention.

As shown in FIG. 5, MAX = maximum (V _ga , V _gb , V _gc ), MID = middle (V _ga , V _gb , V _gc ) for the stator's input phase voltages V _ga , V _gb , V _gc , MIN = minimum (V _ga , V _gb , V _gc ) is defined and max = maximum (V _as ^* , V _bs ^* , for the output phase voltage commands V _sa ^* , V _sb ^* , V _sc ^* of the rotor. V _cs ^* ) and min = minimum (V _as ^* , V _bs ^* , V _cs ^* ) may be defined, respectively.

During the T _{1 period} , the voltage between MAX and MIN with the largest input line voltage can be used as the DC link voltage. In order to increase the voltage utilization during the T _{2 period} , the next higher input line voltage is used. For example, a voltage between MAX and MID or a voltage between MID and MIN may be used depending on the situation. .

For example, as shown in FIG. 5, when the voltage between MAX and MID is greater than the voltage between MID and MIN among the input line voltages, the carrier is MAX because the voltage between MAX and MIN is used as the virtual DC link voltage during the T _{1 period} . Up to MIN can be displayed. In addition, since the voltage between MAX and MID is used as the virtual DC link voltage during the T _{2 period,} the carrier can be indicated from MID to MAX. Thus, the carrier may appear discontinuously.

The offset voltage V _sn sets the pole voltage commands in the middle of the DC link voltage to position the effective vector in the middle of the switching period and the zero vector for the same time at both ends of the switching period. Can be. In this manner, the offset voltage can be obtained such that the effective vector and the zero vector are arranged in the T ₁ and T ₂ sections.

The offset voltage in the T ₁ section can be expressed as Equation 10 below.

[Equation 10]

The offset voltage in T ₂ can be expressed as Equation 11 and Equation 12 below. When using a voltage between MAX and MID as the virtual DC link voltage, use Equation 11 and MID. Equation 12 can be used when using a voltage between and MIN.

[Equation 11]

[Equation 12]

In this case, the switching time T ₁ section and T ₂ section may be determined according to the phase angle of the input voltage, and the sum of the T ₁ section and the T ₂ section should always be the switching period T _s . The T ₁ section and the T ₂ section may be expressed as in Equations 13 and 14 below.

[Equation 13]

[Equation 14]

와

의 관계를 설명하기 위한 예시도이다.6 is according to an embodiment of the present invention

Wow

It is an exemplary view for explaining the relationship of.

As shown in FIG. 6, the relationship of and may be expressed as in Equation 15 below.

[Equation 15]

Thereafter, the controller generates a PWM pulse according to the generated gate signal (S470), and receives the generated PWM pulse to drive the gate of the matrix converter accordingly (S480).

Hereinafter, various simulations have been performed using PSCAD / EMTDC software to analyze the operation and performance of the matrix converter proposed by the present invention, which will be described with reference to FIGS. 7 to 10.

7 is an exemplary view showing a simulation model of a controller according to an embodiment of the present invention.

As shown in FIG. 7, a simulation model of the controller is illustrated assuming a power system or a grid side as an input side and a rotor side of the generator as an output side. The controller defines MAX, MID, and MIN from the three-phase voltage at the input side using the PLL unit, and detects the voltage and current at the output side to estimate the magnetic flux induced by the stator and the rotor by using Equation (5). In addition, the rotational speed of the induction generator can be detected using an encoder, and the torque value of the induction generator can be calculated based on the detected rotational speed and the estimated magnetic flux.

The torque value thus found is defined as a reference value of the active power and the reactive power of the matrix converter, and the measured value is controlled accordingly. The PLL can also be used to calculate the T ₁ and T ₂ values for generating discrete carriers using MAX, MID, MIN, and reference values defined at the output three-phase voltage. Therefore, the controller can generate the gate signal to be applied to the switches of the nine matrix converters based on all the values thus obtained.

In order to verify the operation of dual excitation wind power generation system composed of matrix converters, a simulation was conducted using PSCAD / EMTDC software. In the simulation model, a wind power generation system was constructed using a three-phase 220V grid voltage and a 3.7KW winding type induction generator, and the existing rotor was connected to a power system using a matrix converter and a transformer.

Important parameters of such a simulation model can be shown in the following [Table 1].

TABLE 1

Bus voltage (L-L) 220 [V] Busbar frequency 60 [Hz] Blade rated wind speed 12 m / s Blade length 1.78 m Generator rating 3.7 [KW] Rotor side transformer 110: 220 (△ -Y) Switching frequency 5000 [Hz] Induction generator pole number 6-pole Cp (max) 0.323

It is assumed that the grid voltage is 220 [V] and the 6-pole induction generator produces synchronous speed at rated wind speed of 12 m / s.

8 is an exemplary view showing a simulation model of a wind power generation system according to the present invention.

As shown in FIG. 8, the simulation model of the wind power generation system according to the present invention may include a turbine simulator, a wound induction generator, a matrix converter, a controller, and the like. In particular, a transformer of 110 / 220V was used to smoothly combine the output voltage of the matrix converter connected to the rotor of the wound induction generator with the power system voltage.

9A to 9E are exemplary views showing computer simulation results according to an embodiment of the present invention.

As shown in Figs. 9A to 9E, the wind speed Vwind in Fig. 9A can be increased to 11 m / s from 40 seconds to 50 seconds and to 13 m / s from 50 seconds to 60 seconds. The rotational speed Wrpm of the induction generator according to the wind speed, the active power P_stator of the stator, the active power P_rotor of the rotor, and the total active power P_total supplied to the power system from the induction generator are shown in FIGS. 9B, 9C, 9D, and 9E, respectively. It can be seen that

Since the active power P_stator of the stator has a (+) sign when it is supplied from the power system to the induction generator, when the sign is (-) as shown in FIG. 9C, the stator may supply active power from the stator to the power system.

Since the active power P_rotor of the rotor also has a (+) sign when it is supplied from the power system to the induction generator, when the sign is (-) as shown in FIG. 9D, the active power may be supplied from the rotor to the power system.

On the other hand, as shown in FIG. 9E, the entire active power P_total delivered to the power system also has a positive sign when supplying the active power to the power system. If it is slower than the synchronous speed, the stator supplies the active power to the power system, but the rotor Active power can be supplied from the power system. Accordingly, the sum of the two active powers may have a sign of (+), which may mean that the active power supplied by the turbine simulator may be supplied to the power system.

However, at 1280 rpm, which is slightly higher than the synchronous speed, the active power of the rotor is changed from (+) to (-), and the total active power of the stator and rotor can be supplied to the power system.

In addition, when the rotational speed is 840rpm, the frequency of the rotor current may be 18 Hz proportional to slip. Since the rotor current is determined by the torque of the generator and the rotation speed is lower than the synchronous speed of 1200rpm, the active power on the rotor side may have a positive sign because the matrix converter supplies the active power to the rotor.

When the rotational speed is the synchronous speed, since the slip is 0 and the frequency of the rotor current has a value of 0, the DC shape can be shown as in the drawing. In synchronous speed, theoretically, the active power of the rotor shows 0, but it can be seen that it has some positive value due to the loss of the generator.

At 1310rpm, where the rotation speed is more than the synchronous speed, the frequency of the rotor current increases again to appear in the form of AC, and the active power of the rotor may represent a negative value. That is, it can be seen that the effective power is supplied to the power system from the rotor side of the induction generator.

10 is an exemplary view showing a voltage / current waveform according to the rotational speed of the induction generator according to an embodiment of the present invention.

As shown in FIG. 10, the current of the rotor, the voltage of the stator, and the effective power of the rotor according to the change of the rotation speed of the induction generator are shown. It can be seen that.

At this time, since the stator is connected to the power system, it can be seen that the voltage and frequency are constant regardless of the rotation speed. The effective power supplied from the stator to the power system may increase as the rotation speed increases. However, the current and frequency of the rotor can be different in magnitude and sign from the rotational speed in proportion to the rotational speed.

In the following, a wind power generation hardware simulator consisting of a squirrel cage induction motor and a winding induction generator was fabricated to confirm the possibility of hardware implementation of the proposed wind power generation system. The mechanical characteristics of the wind turbine are designed to simulate using a squirrel cage induction motor and a vector drive, and the electrical characteristics of the wind turbine are designed to simulate using a wound induction generator and a matrix converter, which will be described with reference to FIG. do.

11 is an exemplary view showing a prototype of a wind power generation system according to an embodiment of the present invention.

As shown in FIG. 11, a photograph of the wind power generation simulator used in the experiment is shown. A squirrel cage induction motor, a vector drive, and a winding induction generator simulating a wind turbine are one motor-generator set (MG-SET). It can be configured as. The matrix converter and the controller are manufactured in separate panels to connect the rotor and power system of the induction generator, and the controller is manufactured using TMS320vc33, a 32-bit floating-point DSP.

The critical circuit constants of the hardware simulator used in the experiment can be shown in the following [Table 2].

TABLE 2

Power supply voltage (L-L) 220 [V] Busbar frequency 60 [Hz] Motor rated capacity 7.5 [KW] Motor rated rotation speed 1750 rpm Generator rated capacity 3.7 [KW] Generator Rated Speed 1130 rpm Transformer ratio 110: 220 (△ -Y) Number of winding induction generator poles 6-pole

In this case, a squirrel cage induction motor simulating a turbine used 7.5kW, which is larger than the generator capacity of 3.7kW, to simulate various wind characteristics. A 110/220 transformer was also used to properly couple the low output voltage of the matrix converter to the grid voltage.

12A to 12C are exemplary views showing experimental results of a wind power generation system according to an embodiment of the present invention.

As shown in Figs. 12A to 12C, the experiment shows that the winding type induction generator has an active power of a stator, an active power of a rotor, a rotor A phase current, Stator A phase voltage is shown.

As shown in FIG. 12A, at 900 rpm, which is less than or equal to the synchronous speed, the active power supplied by the stator to the power system has a positive value, but the active power of the rotor has a negative value so that the active power flows into the induction generator in the rotor. Able to know. Accordingly, it can be seen that the sum of the active power of the stator and the active power of the rotor is a positive value and the active power formed in the blade is supplied to the power system as a whole. It can also be seen that the stator voltage maintains the grid voltage and the rotor current is low frequency AC.

As shown in FIG. 12B, the active power supplied to the power system by the stator has a positive value at the synchronous speed of 1200 rpm, and the active power of the rotor has a negative value so that the active power flows into the induction generator in the rotor. Able to know. At this time, due to the loss of the system, the effective power of the rotor is not zero, but its size is very small. Accordingly, it can be seen that the active power formed in the blade as a whole is supplied to the power system. In addition, it can be seen that the voltage of the stator maintains the grid voltage and the current of the rotor is DC because the slip is zero.

As shown in FIG. 12C, it can be seen that the active power of the stator and the rotor have a positive value at 1400 rpm, which is equal to or greater than the synchronous speed. Through this, the active power formed in the blade is supplied to the power system in two paths. . In addition, it can be seen that the voltage of the stator maintains the grid voltage, and the current of the rotor becomes alternating current with increasing slip.

As described above, the present invention replaces a back-to-back converter, which is a power converter of a conventional dual excitation induction wind power generation system, with a matrix converter capable of directly converting AC-AC, and describes the contents of analyzing its operating characteristics. We proposed a new output voltage modulation technique with simple switching operation and high reliability for the matrix converter, and developed a simulation model to verify the operation of the dual excitation induction wind power generation system. The validity of the hardware implementation is demonstrated.

Therefore, the dual excitation induction wind power generation system according to the present invention, unlike the system using a conventional back-to-back converter can have the advantage that the efficiency of the system can be improved and simplified by removing the DC link back-to Replacement of the back converter may be possible.

The functions used in the system disclosed herein can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). do. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

The dual excitation induction wind power generation system and the control method thereof according to the present invention can be modified and applied in various forms within the scope of the technical idea of the present invention, and are not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the technical spirit of the present invention, it is not limited to the above embodiments and the accompanying drawings, of course, and not only the claims to be described below but also claims Judgment should be made including scope and equivalence.

1 is an exemplary view showing the configuration of a schematic wind power generation system according to an embodiment of the present invention.

2 is an exemplary view showing a detailed structure of the three-phase matrix converter shown in FIG.

3 is an exemplary view showing a detailed structure of the matrix converter shown in FIG.

4 is an exemplary view showing a control method of a wind power generation system according to an embodiment of the present invention.

5 is an exemplary view for explaining the principle of the voltage modulation method using an offset according to an embodiment of the present invention.

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의 관계를 설명하기 위한 예시도이다.6 is according to an embodiment of the present invention

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It is an exemplary view for explaining the relationship of.

7 is an exemplary view showing a simulation model of a controller according to an embodiment of the present invention.

8 is an exemplary view showing a simulation model of a wind power generation system according to the present invention.

9A to 9E are exemplary views showing computer simulation results according to an embodiment of the present invention.

10 is an exemplary view showing a voltage / current waveform according to the rotational speed of the induction generator according to an embodiment of the present invention.

11 is an exemplary view showing a prototype of a wind power generation system according to an embodiment of the present invention.

12A to 12C are exemplary views showing experimental results of a wind power generation system according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110: blade

120: gearbox

130: generator

140: breaker

150: controller

160: power system

310: parameter estimation unit

320: reference current generator

330: current control unit

340: voltage modulator

350: PWM generator

360: gate driver

370: PLL section

Claims (11)

A matrix converter connected between the rotor and the power system of the wound induction generator to control the output or rotational speed of the wound induction generator connected to the blade; And A controller for controlling the matrix converter through a voltage modulation method using an offset voltage The controller includes: a parameter estimator for estimating magnetic flux and slip angular velocity of a rotor of the winding induction generator; A reference current generator configured to calculate torque of the wound induction generator based on the estimated magnetic flux and slip angular velocity and generate a reference current for controlling the active power of the rotor based on the torque; A current controller configured to generate a voltage command on the output of the rotor based on the generated reference current; And a voltage modulator for generating a gate signal for switching control of the matrix converter based on the generated output phase voltage command and the measured input phase voltage of the stator of the winding type induction generator. Type wind power system. delete According to claim 1, The voltage modulator, Generates a carrier and an offset voltage within a switching period based on the input phase voltage, Generate a pole voltage command based on the generated offset voltage and the output phase voltage command, And a gate signal for controlling the matrix converter by comparing the pole voltage command with the carrier. The method of claim 3, The voltage modulator, One switching section T _s for each phase is divided into at least two switching sections T ₁ and T ₂ according to the phase angle of the input voltage, and the carrier and the offset voltage are generated in the switching sections T ₁ and T ₂ , respectively. Dual excitation induction wind power system, characterized in that. According to claim 1, A PWM generator for generating a pulse width modulation (PWM) pulse in accordance with the generated gate signal; And And a gate driver for driving the gate of the matrix converter according to the generated PWM pulses. According to claim 1, A circuit breaker connected between the stator of the winding-type induction generator and the power system Dual excitation induction wind power generation system further comprising. Estimating magnetic flux and slip angular velocity for the rotor of the wound induction generator connected to the blade; Calculating a torque of the wound induction generator based on the estimated magnetic flux and slip angular velocity and generating a reference current for controlling the active power of the rotor based on the torque; Generating a voltage command on the output of the rotor based on the generated reference current; And Generating a gate signal for switching control of a matrix converter based on the generated output phase voltage command and the measured input phase voltage of the stator of the wound induction generator. . 8. The method of claim 7, Generating the gate signal, Generating a carrier and an offset voltage within a switching period based on the input phase voltage; Generating a pole voltage command based on the generated offset voltage and the output phase voltage command; And And comparing the pole voltage command with the carrier to generate a gate signal for controlling the matrix converter. The method of claim 8, Generating the carrier and the offset voltage, One switching section T _s for each phase is divided into at least two switching sections T ₁ and T ₂ according to the phase angle of the input voltage, and the carrier and the offset voltage are generated in the switching sections T ₁ and T ₂ , respectively. Control method of a wind power system, characterized in that. 8. The method of claim 7, Generating a pulse width modulation (PWM) pulse according to the generated gate signal; And Receiving the generated PWM pulses and driving the gate of the matrix converter accordingly. A recording medium having recorded thereon a computer readable program for performing the method of any one of claims 7 to 10.

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