Droop control method and device for a doubly-fed gravity energy storage system based on electromagnetic torque

Abstract

The present invention discloses a droop control method and device for a doubly-fed gravity energy storage system based on electromagnetic torque. The method comprises: collecting the three-phase voltage and current on the stator side, the three-phase current on the rotor side, the actual value of the electromagnetic torque, and the rotor speed of a doubly-fed motor; using a proportional-integral regulator and combining it with the rotor speed to provide an electromagnetic torque reference value, and performing droop control to obtain a phase reference value and a phase slip in combination with the electromagnetic torque actual value and the rotor speed; performing coordinate transformation on the three-phase voltage and current on the stator side and the three-phase current on the rotor side according to the phase reference value and the phase slip, and providing a coordinate transformation result; obtaining a stator flux according to the coordinate transformation result, performing feedforward calculation, and providing a rotor side voltage adjustment value; analyzing the stator side voltage amplitude reference value in combination with the stator side reactive power, integrating it into the proportional-integral regulator, and providing a rotor side target voltage reference value; and generating a control signal according to the rotor side target voltage reference value to control the doubly-fed motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of gravity energy storage, and in particular relates to a droop control method and device for a double-fed gravity energy storage system based on electromagnetic torque. Background Art

[0002] In the power system, gravity energy storage, as a reliable means of energy storage, provides support for the large-scale consumption of renewable energy.

[0003] At present, most gravity energy storage systems use synchronous motors as generator motors, which realize the conversion of mechanical energy into electrical energy through the synchronous rotation of the motor rotor and stator magnetic field. Patent CN115714558A discloses a model prediction torque control method for improving the efficiency of gravity energy storage motors, which relates to the field of motor control technology. The voltage vector, rotor position angle and stator current of the motor are input into the prediction model to predict the magnetic flux and torque of the motor at the next moment; the predicted variable value of the motor and the given reference value are subjected to the cost function to screen the optimal voltage vector to act on the system, and the cost function includes a load angle cost function. The stability performance of the permanent magnet synchronous motor under complex working conditions is improved, thereby improving the efficiency of the gravity energy storage motor control system and improving the practicality of the gravity energy storage system.

[0004] In gravity energy storage, a synchronous machine is usually used to convert the gravitational potential energy of a heavy object into electrical energy and transmit it to the load end or the grid end. However, the speed of the synchronous machine is the speed corresponding to the grid frequency, so the speed at which the heavy object rises or falls can only maintain a single value. It is difficult to quickly respond to instantaneous changes in the load and achieve precise speed regulation. Summary of the Invention

[0005] In view of the defects in the above-mentioned prior art, the present invention provides a droop control method and device for a doubly fed gravity energy storage system based on electromagnetic torque, the method comprising: collecting the three-phase voltage on the stator side, the three-phase current on the stator side, the three-phase current on the rotor side, the actual value of the electromagnetic torque and the rotor speed of the doubly fed motor; using a proportional-integral regulator, in combination with the rotor speed of the doubly fed motor, giving an electromagnetic torque reference value; based on the electromagnetic torque reference value, in combination with the actual value of the electromagnetic torque and the rotor speed, performing droop control to obtain a phase reference value and a phase slip; and according to the phase reference value and the phase slip, performing droop control on the doubly fed motor. The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are transformed to provide the coordinate transformation result; the flux calculation is performed based on the coordinate transformation result, and the stator flux obtained by the flux calculation is combined to perform feedforward calculation to provide the rotor side voltage adjustment value; based on the rotor side voltage adjustment value and combined with the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional-integral regulator to provide the rotor side target voltage reference value; the rotor side target voltage reference value is subjected to space vector pulse width modulation to generate a control signal to control the rotor side converter in the doubly fed generator.

[0006] In a first aspect, the present invention provides a droop control method for a doubly-fed gravity energy storage system based on electromagnetic torque, which specifically comprises the following steps:

[0007] Collect the stator side three-phase voltage, stator side three-phase current, rotor side three-phase current, actual value of electromagnetic torque and rotor speed of the doubly fed generator;

[0008] The electromagnetic torque reference value is given by the proportional-integral regulator in combination with the rotor speed of the doubly-fed generator;

[0009] Based on the electromagnetic torque reference value, combined with the actual electromagnetic torque value and the rotor speed, droop control is performed to obtain the phase reference value and phase slip;

[0010] According to the phase reference value and phase slip, coordinate transformation is performed on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side, and the coordinate transformation result is given;

[0011] The flux calculation is performed based on the coordinate transformation results. The stator flux obtained by the flux calculation is combined with the feedforward calculation to provide the rotor side voltage adjustment value.

[0012] According to the rotor side voltage adjustment value, combined with the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional integral regulator to give the rotor side target voltage reference value;

[0013] The rotor-side target voltage reference value is subjected to space vector pulse width modulation to generate a control signal for controlling the rotor-side converter in the doubly-fed generator.

[0014] Furthermore, the proportional-integral regulator is used to provide an electromagnetic torque reference value in combination with the rotor speed of the doubly-fed generator, specifically including:

[0015] According to the rotor speed of the doubly-fed generator and the rotor speed reference value, the change of the rotor speed of the doubly-fed generator is analyzed, and the speed difference between the rotor speed and the rotor speed reference value is given;

[0016] Determine the proportional-integral regulator through the proportional gain and integral gain of the electromagnetic torque;

[0017] Combining the proportional-integral regulator and the speed difference, the electromagnetic torque reference value is given.

[0018] Furthermore, based on the electromagnetic torque reference value, combined with the actual electromagnetic torque value and the rotor speed, droop control is performed to obtain a phase reference value, specifically including:

[0019] According to the electromagnetic torque reference value and the actual electromagnetic torque value, the change of the electromagnetic torque of the doubly fed motor is analyzed, and the torque difference between the electromagnetic torque reference value and the actual electromagnetic torque value is given;

[0020] According to the torque difference, combined with the droop coefficient and the frequency setting value, the stator side frequency reference value is given;

[0021] The stator side frequency reference value is integrated and calculated to obtain the phase reference value.

[0022] Furthermore, the coordinate transformation result includes the stator side voltage component, the stator side current component and the rotor side current component in the two-phase rotating coordinate system;

[0023] According to the phase reference value and phase slip, coordinate transformation is performed on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side, and the coordinate transformation results are given, including:

[0024] The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given;

[0025] According to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system;

[0026] According to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system.

[0027] Furthermore, the coordinate transformation is to transform the two-phase / three-phase stationary coordinate system into a two-phase rotating coordinate system.

[0028] Furthermore, the stator side voltage component in the two-phase stationary coordinate system includes a stator side voltage α component and a stator side voltage β component, the stator side current component in the two-phase stationary coordinate system includes a stator side current α component and a stator side current β component, and the rotor side current component in the two-phase stationary coordinate system includes a rotor side current α component and a rotor side current β component;

[0029] The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given, specifically including:

[0030] Based on the Clarke transformation matrix, the coordinate transformation of the stator side three-phase voltage, the stator side three-phase current and the rotor side three-phase current in the three-phase coordinate system is performed respectively to obtain the corresponding stator side voltage α component, stator side voltage β component, stator side current α component, stator side current β component, rotor side current α component and rotor side current β component.

[0031] Furthermore, the stator side voltage component in the two-phase rotating coordinate system includes a stator side voltage d component and a stator side voltage q component, and the stator side current component in the two-phase rotating coordinate system includes a stator side current d component and a stator side current q component;

[0032] According to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system, which specifically include:

[0033] Determining a first Park transformation matrix according to the phase reference value;

[0034] Based on the first Park transformation matrix, the stator side voltage component and the stator side current component in the two-phase stationary coordinate system are respectively transformed to obtain the corresponding stator side voltage d component, stator side voltage q component, stator side current d component and stator side current q component.

[0035] Furthermore, the rotor side current component in the two-phase rotating coordinate system includes a rotor side current d component and a rotor side current q component;

[0036] According to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system, which specifically includes:

[0037] Determine a second Park transformation matrix according to the phase slip;

[0038] Based on the second Park transformation matrix, coordinate transformation is performed on the rotor side current components in the two-phase stationary coordinate system to obtain corresponding rotor side current d component and rotor side current q component.

[0039] Furthermore, the flux calculation is performed based on the coordinate transformation results. Combined with the stator flux obtained by the flux calculation, a feedforward calculation is performed to provide the rotor side voltage adjustment value, specifically including:

[0040] According to the stator side voltage component and stator side current component in the two-phase stationary coordinate system in the coordinate transformation result, combined with the stator resistance, the stator flux in the two-phase stationary coordinate system is given;

[0041] According to the first Park transformation matrix, combined with the stator flux in the two-phase stationary coordinate system, the stator flux in the two-phase rotating coordinate system is obtained;

[0042] Based on the stator flux in the two-phase rotating coordinate system, combined with the rotor resistance, rotor leakage inductance, speed slip and mutual inductance, the rotor side voltage adjustment value is obtained.

[0043] Furthermore, the stator flux in the two-phase rotating coordinate system includes a stator flux d component and a stator flux q component, and the rotor side voltage adjustment value includes a rotor side voltage adjustment value d component and a rotor side voltage adjustment value q component;

[0044] Based on the stator flux in the two-phase rotating coordinate system, combined with the rotor resistance, rotor leakage inductance, speed slip and mutual inductance, the rotor side voltage adjustment value is obtained, specifically including:

[0045] The product of the rotor resistance and the rotor side current q component is taken as the first product;

[0046] The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current d component is used as the second product;

[0047] The product of the speed slip, the leakage inductance ratio and the stator flux d component is used as the third product, wherein the leakage inductance ratio is the ratio of the mutual inductance to the stator leakage inductance;

[0048] The product of the rotor resistance and the rotor side current d component is taken as the fourth product;

[0049] The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current q component is taken as the fifth product;

[0050] Add the first product, the second product and the third product to obtain the rotor side voltage adjustment value d component;

[0051] The fifth product is subtracted from the fourth product to obtain the rotor side voltage adjustment value q component.

[0052] Furthermore, the stator-side reactive power is obtained by multiplying each stator-side line voltage component of the doubly-fed generator by the corresponding stator-side line current component.

[0053] Furthermore, the leakage inductance coefficient is obtained by the stator leakage inductance, the rotor leakage inductance and the mutual inductance.

[0054] Furthermore, based on the rotor side voltage adjustment value and the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional integral regulator to provide the rotor side target voltage reference value, specifically including:

[0055] Based on the power difference between the stator side reactive power and the stator side reactive power reference value, combined with the droop coefficient and the voltage amplitude setting value, a stator side voltage amplitude reference value is given;

[0056] According to the stator side voltage amplitude reference value and the stator side angular frequency reference value, the stator side three-phase voltage in the three-phase stationary coordinate system is given, and the stator side three-phase voltage is transformed into a stator side voltage reference value in the two-phase rotating coordinate system;

[0057] The voltage difference between the stator side voltage reference value and the stator side voltage component in the two-phase rotating coordinate system is analyzed, and the rotor side current reference value in the two-phase rotating coordinate system is given by combining the proportional integral regulator;

[0058] A current closed loop is adopted to obtain the rotor side target voltage reference value based on the rotor side current reference value and the current difference of the rotor side current component in the two-phase rotating coordinate system, the proportional integral regulator and the rotor side voltage adjustment value are integrated.

[0059] Furthermore, performing space vector pulse width modulation on the rotor-side target voltage reference value to generate a control signal to control the rotor-side converter in the doubly-fed generator specifically includes:

[0060] Converting the rotor side target voltage reference value from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the rotor side target voltage α component and the rotor side target voltage β component;

[0061] Analyze the amplitude and phase of the rotor-side target voltage according to the rotor-side target voltage α component and the rotor-side target voltage β component to determine the sector where the rotor-side target voltage is located;

[0062] Based on the sector where the rotor side target voltage is located, the effective vector and the zero vector are selected, and the vector action time is given;

[0063] According to the vector action time, a control signal required by the rotor-side converter is generated, and the rotor-side converter in the doubly-fed generator is controlled according to the control signal.

[0064] In a second aspect, the present invention further provides a droop control device for a doubly-fed gravity energy storage system based on electromagnetic torque, which adopts any of the above-mentioned droop control methods for a doubly-fed gravity energy storage system based on electromagnetic torque, comprising:

[0065] A data acquisition module is used to collect the stator side three-phase voltage, stator side three-phase current, rotor side three-phase current, actual value of electromagnetic torque and rotor speed of the doubly fed motor;

[0066] The torque determination module is used to provide an electromagnetic torque reference value by combining the rotor speed of the doubly-fed generator through a proportional-integral regulator;

[0067] A phase determination module is used to perform droop control based on the electromagnetic torque reference value, the actual electromagnetic torque value and the rotor speed to obtain a phase reference value and a phase slip;

[0068] The coordinate transformation module is used to perform coordinate transformation on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side according to the phase reference value and the phase slip, and provide the coordinate transformation result;

[0069] The flux calculation module is used to calculate the flux according to the coordinate transformation results, and perform feedforward calculation based on the stator flux obtained by the flux calculation to provide the rotor side voltage adjustment value;

[0070] The voltage calculation module is used to analyze the stator side voltage amplitude reference value based on the rotor side voltage adjustment value and the stator side reactive power, integrate it into the proportional integral regulator, and provide the rotor side target voltage reference value;

[0071] The control module is used to perform space vector pulse width modulation on the rotor side target voltage reference value to generate a control signal to control the rotor side converter in the doubly fed generator.

[0072] The electromagnetic torque-based droop control method and device for a doubly-fed gravity energy storage system provided by the present invention have at least the following beneficial effects:

[0073] (1) Through the coordinated control of the stator side and rotor side of the doubly fed machine, the rotor side voltage is directly controlled, and the electromagnetic torque reference value is used. Droop control can respond to the rotor speed reference value in time , the mechanical torque of the heavy object and the transformation of the active power consumed at the load end, and make adaptive adjustments to translate the droop curve to maintain the ultimate stability of the gravity energy storage system and improve the grid support capacity of the doubly fed gravity energy storage system.

[0074] (2) Introducing the rotor side voltage adjustment value to correct the rotor side voltage can dynamically offset the coupled voltage component, further reduce power fluctuations, and improve the dynamic performance and control accuracy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 A flow chart of a droop control method for a double-fed gravity energy storage system based on electromagnetic torque provided by an embodiment of the present invention;

[0076] Figure 2 A flow chart for providing an electromagnetic torque reference value provided by an embodiment of the present invention;

[0077] Figure 3 A flow chart for obtaining a phase reference value provided by an embodiment of the present invention;

[0078] Figure 4 A flow chart for obtaining phase slip provided by an embodiment of the present invention;

[0079] Figure 5 A flowchart showing coordinate transformation results provided by an embodiment of the present invention;

[0080] Figure 6 A flow chart for providing a rotor side voltage adjustment value provided by an embodiment of the present invention;

[0081] Figure 7 A flow chart of generating a control signal provided by an embodiment of the present invention;

[0082] Figure 8 A structural block diagram of droop control based on electromagnetic torque provided in an embodiment of the present invention;

[0083] Figure 9 This is a structural block diagram of a droop control device for a doubly-fed gravity energy storage system based on electromagnetic torque provided by an embodiment of the present invention.

[0084] Among them, 201 is a data acquisition module; 202 is a torque determination module; 203 is a phase determination module; 204 is a coordinate transformation module; 205 is a flux calculation module; 206 is a voltage calculation module; and 207 is a control module. DETAILED DESCRIPTION

[0085] To better understand the above technical solution, the following will be described in detail with reference to the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0086] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0087] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0088] With the world's increasing emphasis on clean energy and sustainable development, the development and utilization of renewable energy has become increasingly important.

[0089] Gravity energy storage utilizes the height difference between objects to store and release energy. During charging, the system converts electrical energy into gravitational potential energy by lifting a heavy object. During discharge, the heavy object descends, driving a generator to generate electricity, converting gravitational potential energy into electrical energy. This energy storage method not only offers stable technical performance, a long service life, and no degradation, but is also highly safe and pollution-free. Furthermore, gravity energy storage has low site requirements and few restrictions on applicable scenarios, making it potentially suitable for large-scale deployment. Especially when combined with new energy projects such as photovoltaic and wind power generation, gravity energy storage can form an integrated energy system and improve energy efficiency. Furthermore, the rotational inertia of gravity energy storage can provide the power system with systemic anti-disturbance capabilities, further enhancing its stability.

[0090] In power systems, the grid-connected operation of renewable energy has become a critical issue. Doubly-fed generators, as an important power electronic device, play a vital role in the grid-connected control of renewable energy. Traditional droop control is a control strategy capable of independently supporting grid voltage. By simulating the droop characteristics of synchronous generators, it generates the phase angle and amplitude of the internal potential, thereby enabling rapid adjustment of the pulse width modulation (PWM) signal. This control strategy enables doubly-fed generators to achieve instantaneous active / reactive power response during grid-connected operation, freeing them from the response delay of the measurement link.

[0091] Doubly-fed asynchronous motors, on the other hand, can flexibly control rotor speed and, at the same time, enable a wider range of power adjustments fed into the grid by gravity energy storage systems by varying rotor speed or the mechanical torque of the weights. However, unlike synchronous motors, doubly-fed motors have low damping and mechanical inertia, and their ability to support the grid is limited. Therefore, a droop control strategy is employed to simulate the primary frequency modulation characteristics of synchronous motors. Applying doubly-fed mechanism network control to gravity energy storage systems can fully leverage the advantages of both, further improving the stability and reliability of the power system. This combined application not only optimizes the energy structure and improves the utilization and reliability of renewable energy, but also provides strong support and guarantees for the development of new energy, promoting the sustained and healthy development of the new energy industry.

[0092] In order to change the power fed into the grid, it is necessary to change the torque of the weight, e.g. Figure 1 As shown, an embodiment of the present invention provides a droop control method for a doubly fed gravity energy storage system based on electromagnetic torque, and the specific steps are as follows:

[0093] S101: Collecting the stator side three-phase voltage, stator side three-phase current, rotor side three-phase current, actual value of electromagnetic torque and rotor speed of the doubly-fed generator.

[0094] In the embodiment provided by the present invention, the three-phase voltage on the stator side is Collected through the following methods:

[0095] First, select a suitable voltage transformer. In this example, an electromagnetic voltage transformer is chosen, with a rated primary voltage matching the stator grid voltage and a secondary capable of outputting a low-voltage standard signal. Connect the selected electromagnetic voltage transformer to the stator using a three-phase star connection. Fuses are installed to protect the secondary side from short circuits. A signal conditioning module converts the secondary voltage signal into an analog value for reading by a data acquisition card. An RC low-pass filter is used to eliminate high-frequency noise. A synchronous sampler is used to sample and calculate the amplitude to obtain the effective value of the three-phase voltage, which is the stator three-phase voltage.

[0096] In the embodiment provided by the present invention, the three-phase current on the stator side Collected by:

[0097] Similarly, first select an appropriate current sensor. In this example, a closed-loop Hall effect current sensor is chosen. Its rated current covers the stator rated current and its bandwidth is sufficient to capture high-frequency harmonics. The closed-loop Hall effect current sensor is connected in series between the stator winding and the grid connection to ensure independent measurement of the three phases and avoid magnetic field interference. Short-circuit protection resistors are placed on the secondary side of the current sensor to prevent the risk of open-circuit high voltage. The sensor's output current signal is converted to a voltage signal using a precision shunt resistor, and the amplified voltage signal is collected using a synchronous sampler. Finally, the amplified voltage signal is converted back to a current signal using a voltage-to-current conversion circuit to obtain the three-phase current on the stator side.

[0098] In the embodiment provided by the present invention, the rotor side three-phase current Collected through the following methods:

[0099] A broadband Rogowski coil is selected as the sensor to accommodate the frequency variations of the rotor current. It is connected to the rotor circuit via slip rings. The slip ring contact resistance should be less than 1mΩ to minimize signal attenuation. The Rogowski coil directly outputs a mV-range voltage, which is amplified by an instrumentation amplifier. The amplified signal is then converted back to the original current signal by an integrator circuit, yielding the three-phase rotor current.

[0100] In the embodiment provided by the present invention, the rotor speed Collected through the following methods:

[0101] First, select a suitable encoder. In this example, an incremental photoelectric encoder is selected. Mount the incremental photoelectric encoder to the motor shaft end through a coupling, ensuring a coaxiality error of <0.05mm to avoid vibration interference. The incremental photoelectric encoder outputs two orthogonal pulse signals, A and B, which are used to calculate speed and direction. Specifically, they are expressed as:

[0102]

[0103] in, is the number of pulses, Z is the number of encoder lines, is the sampling period.

[0104] In the embodiment provided by the present invention, the actual value of the electromagnetic torque Collected through the following methods:

[0105] A photoelectric torque sensor is selected to measure the actual electromagnetic torque value. The sensor is mounted on the motor shaft. The torque signal output by the sensor is collected, amplified, and filtered. The conditioned analog signal is then converted to a digital signal. Using a calibration curve, the digital signal is mapped to the actual torque value, completing the acquisition of the actual electromagnetic torque value.

[0106] S102: Providing an electromagnetic torque reference value through a proportional-integral regulator in combination with the rotor speed of the doubly-fed generator.

[0107] Reference Figure 2 , giving the electromagnetic torque reference value, specifically including:

[0108] According to the rotor speed of the doubly-fed generator and the rotor speed reference value, the change of the rotor speed of the doubly-fed generator is analyzed, and the speed difference between the rotor speed and the rotor speed reference value is given;

[0109] Determine the proportional-integral regulator through the proportional gain and integral gain of the electromagnetic torque;

[0110] Combining the proportional-integral regulator and the speed difference, the electromagnetic torque reference value is given.

[0111] In a specific embodiment, the rotor speed is As the feedback signal of speed closed loop control, it is controlled by proportional integral regulator. To achieve error-free control of the speed, the transfer function expression of the proportional-integral regulator in the frequency domain is as follows:

[0112]

[0113] in, is the proportional-integral regulator of the electromagnetic torque, S is the complex frequency domain variable in the Laplace transform, is the proportional gain of the electromagnetic torque, is the integral gain of electromagnetic torque.

[0114] Speed ​​closed loop output electromagnetic torque reference value , specifically expressed as:

[0115]

[0116] Where S is the complex frequency domain variable in Laplace transform, is the rotor speed reference value, The rotor speed reference value is the speed preset according to the system performance and operating conditions.

[0117] S103: Based on the electromagnetic torque reference value, combined with the actual electromagnetic torque value and the rotor speed, droop control is performed to obtain a phase reference value and a phase slip.

[0118] Reference Figure 3 , get the phase reference value, specifically including:

[0119] According to the electromagnetic torque reference value and the actual electromagnetic torque value, the change of the electromagnetic torque of the doubly fed motor is analyzed, and the torque difference between the electromagnetic torque reference value and the actual electromagnetic torque value is given;

[0120] According to the torque difference, combined with the droop coefficient and the frequency setting value, the stator side frequency reference value is given;

[0121] The stator side frequency reference value is integrated and calculated to obtain the phase reference value.

[0122] In a specific embodiment, the electromagnetic torque reference value As the input of droop control, it is compared with the actual value of electromagnetic torque Combined processing to obtain the stator side frequency reference value , specifically expressed as:

[0123]

[0124] in, is the stator side frequency reference value, is the preset droop coefficient, is the frequency setting value, is the electromagnetic torque reference value, is the actual value of electromagnetic torque.

[0125] Phase reference value , specifically expressed as:

[0126]

[0127] in, is the phase reference value, S is the complex frequency domain variable in Laplace transform, is the stator side frequency reference value.

[0128] Reference Figure 4 , and get the phase slip, including:

[0129] According to the stator side frequency reference value and rotor speed, the change of the doubly fed generator rotor speed is analyzed and the speed slip is given;

[0130] According to the speed slip, the phase slip is given.

[0131] In a specific embodiment, the stator side frequency reference value f and the rotor speed are Difference, get speed slip , and the speed slip Change to get phase slip , specifically expressed as:

[0132]

[0133] Where S is the complex frequency domain variable in Laplace transform.

[0134] S104: performing coordinate transformation on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side according to the phase reference value and the phase slip, and providing a coordinate transformation result.

[0135] The coordinate transformation results include the stator-side voltage component, stator-side current component, and rotor-side current component in the two-phase rotating coordinate system. The coordinate transformation transforms the two-phase / three-phase stationary coordinate system into a two-phase rotating coordinate system. The stator-side voltage component in the two-phase stationary coordinate system includes the stator-side voltage α component and the stator-side voltage β component. The stator-side current component in the two-phase stationary coordinate system includes the stator-side current α component and the stator-side current β component. The rotor-side current component in the two-phase stationary coordinate system includes the rotor-side current α component and the rotor-side current β component. The stator-side voltage component in the two-phase rotating coordinate system includes the stator-side voltage d component and the stator-side voltage q component. The stator-side current component in the two-phase rotating coordinate system includes the stator-side current d component and the stator-side current q component. The rotor-side current component in the two-phase rotating coordinate system includes the rotor-side current d component and the rotor-side current q component.

[0136] Reference Figure 5 , gives the coordinate transformation results, including:

[0137] The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given;

[0138] According to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system;

[0139] According to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system.

[0140] Furthermore, the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given, specifically including:

[0141] Based on the Clarke transformation matrix, the coordinate transformation of the stator side three-phase voltage, the stator side three-phase current and the rotor side three-phase current in the three-phase coordinate system is performed respectively to obtain the corresponding stator side voltage α component, stator side voltage β component, stator side current α component, stator side current β component, rotor side current α component and rotor side current β component.

[0142] In a specific embodiment, the stator side voltage component in the two-phase stationary coordinate system is , specifically expressed as:

[0143]

[0144] in, is the α component of the stator side voltage, is the stator side voltage β component, is the three-phase voltage on the stator side in the three-phase coordinate system, is the Clarke transformation matrix.

[0145] Stator side current components in the two-phase stationary coordinate system , specifically expressed as:

[0146]

[0147] in, is the α component of the stator side current, is the β component of the stator side current, is the three-phase current on the stator side in the three-phase coordinate system, is the Clarke transformation matrix.

[0148] Rotor side current components in the two-phase stationary coordinate system , specifically expressed as:

[0149]

[0150]

[0151] in, is the rotor side current α component, is the rotor side current β component, is the three-phase current on the rotor side in the three-phase coordinate system, is the Clarke transformation matrix.

[0152] Furthermore, according to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system, specifically including:

[0153] Determining a first Park transformation matrix according to the phase reference value;

[0154] Based on the first Park transformation matrix, the stator side voltage component and the stator side current component in the two-phase stationary coordinate system are respectively transformed to obtain the corresponding stator side voltage d component, stator side voltage q component, stator side current d component and stator side current q component.

[0155] In a specific embodiment, the first Park transformation matrix , specifically expressed as:

[0156]

[0157] in, is the phase reference value. , construct the first Park transformation matrix , transforming the stator side voltage component and the stator side current component from the two-phase stationary coordinate system into the two-phase rotating coordinate system.

[0158] Stator side voltage components in two-phase rotating coordinate system , specifically expressed as:

[0159]

[0160] in, is the stator side voltage d component, is the q component of the stator side voltage.

[0161] Stator side current components in the two-phase rotating coordinate system , specifically expressed as:

[0162]

[0163] in, is the stator side current d component, is the q component of the stator side current.

[0164] Furthermore, according to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system, which specifically includes:

[0165] Determine a second Park transformation matrix according to the phase slip;

[0166] Based on the second Park transformation matrix, coordinate transformation is performed on the rotor side current components in the two-phase stationary coordinate system to obtain corresponding rotor side current d component and rotor side current q component.

[0167] In a specific embodiment, the second Park transformation matrix , specifically expressed as:

[0168]

[0169] in, is the phase slip. , construct the second Park transformation matrix , transforming the rotor side voltage component and the rotor side current component from the two-phase stationary coordinate system to the two-phase rotating coordinate system.

[0170] Rotor side current components in the two-phase rotating coordinate system , specifically expressed as:

[0171]

[0172] in, is the rotor side current d component, is the q component of the rotor side current.

[0173] S105: Calculate the flux linkage according to the coordinate transformation result, perform feedforward calculation based on the stator flux linkage obtained by the flux linkage calculation, and provide a rotor side voltage adjustment value.

[0174] Among them, the stator flux in the two-phase rotating coordinate system includes the stator flux d component and the stator flux q component, the stator flux in the two-phase stationary coordinate system includes the stator flux α component and the stator flux β component, and the rotor side voltage adjustment value includes the rotor side voltage adjustment value d component and the rotor side voltage adjustment value q component.

[0175] Reference Figure 6 , gives the rotor side voltage adjustment value, including:

[0176] According to the stator side voltage component and stator side current component in the two-phase stationary coordinate system in the coordinate transformation result, combined with the stator resistance, the stator flux in the two-phase stationary coordinate system is given;

[0177] According to the first Park transformation matrix, combined with the stator flux in the two-phase stationary coordinate system, the stator flux in the two-phase rotating coordinate system is obtained;

[0178] Based on the stator flux in the two-phase rotating coordinate system, combined with the rotor resistance, rotor leakage inductance, speed slip and mutual inductance, the rotor side voltage adjustment value is obtained.

[0179] In a specific embodiment, the stator flux in the two-phase stationary coordinate system , specifically expressed as:

[0180]

[0181] in, is the stator flux α component, is the stator flux β component, is the stator side voltage component in the two-phase stationary coordinate system, is the stator side current component in the two-phase stationary coordinate system, is the stator resistance, and S is the complex frequency domain variable in Laplace transform.

[0182] Stator flux in two-phase rotating coordinate system , specifically expressed as:

[0183]

[0184] Through the first Park transformation matrix, the stator flux in the two-phase stationary coordinate system is converted to the two-phase rotating coordinate system, and the stator flux in the two-phase rotating coordinate system is obtained. .

[0185] Furthermore, the rotor side voltage adjustment value is obtained, specifically including:

[0186] The product of the rotor resistance and the rotor side current q component is taken as the first product;

[0187] The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current d component is used as the second product;

[0188] The product of the speed slip, the leakage inductance ratio and the stator flux d component is used as the third product, wherein the leakage inductance ratio is the ratio of the mutual inductance to the stator leakage inductance;

[0189] The product of the rotor resistance and the rotor side current d component is taken as the fourth product;

[0190] The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current q component is used as the fifth product, wherein the leakage inductance coefficient is obtained by the stator leakage inductance, the rotor leakage inductance and the mutual inductance;

[0191] Add the first product, the second product and the third product to obtain the rotor side voltage adjustment value d component;

[0192] The fifth product is subtracted from the fourth product to obtain the rotor side voltage adjustment value q component.

[0193] In a specific embodiment, the rotor side voltage adjustment value , specifically expressed as:

[0194]

[0195] in, is the rotor side voltage adjustment value d component, is the rotor side voltage adjustment value q component, is the rotor resistance, is the rotor side current q component, is the speed slip, is the leakage inductance coefficient, is the rotor leakage inductance, is the rotor side current d component, For mutual induction, is the stator leakage inductance, is the stator flux d component.

[0196] S106: Analyze the stator side voltage amplitude reference value according to the rotor side voltage adjustment value and the stator side reactive power, integrate it into the proportional integral regulator, and provide the rotor side target voltage reference value.

[0197] The stator side reactive power is obtained by multiplying each stator side line voltage component of the doubly fed generator by the corresponding stator side line current component. , specifically expressed as:

[0198]

[0199] in, are the stator side line voltage components under three-phase voltage coordinates, They are the stator side line current components corresponding to the stator side line voltage components under the three-phase voltage coordinates.

[0200] It's understood that line voltage refers to the voltage between any two end-point (live) wires in a three-phase circuit. In a symmetrical three-phase circuit, the voltages on each phase are equal in magnitude and 120° out of phase with each other. Line current refers to the current flowing between any two end-point (live) wires in a three-phase circuit. In a symmetrical three-phase circuit, the currents on each phase are equal in magnitude and 120° out of phase with each other.

[0201] Furthermore, based on the rotor side voltage adjustment value and the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional integral regulator to provide the rotor side target voltage reference value, specifically including:

[0202] Based on the power difference between the stator side reactive power and the stator side reactive power reference value, combined with the droop coefficient and the voltage amplitude setting value, a stator side voltage amplitude reference value is given;

[0203] According to the stator side voltage amplitude reference value and the stator side angular frequency reference value, the stator side three-phase voltage in the three-phase stationary coordinate system is given, and the stator side three-phase voltage is transformed into a stator side voltage reference value in the two-phase rotating coordinate system;

[0204] The voltage difference between the stator side voltage reference value and the stator side voltage component in the two-phase rotating coordinate system is analyzed, and the rotor side current reference value in the two-phase rotating coordinate system is given by combining the proportional integral regulator;

[0205] A current closed loop is adopted to obtain the rotor side target voltage reference value based on the rotor side current reference value and the current difference of the rotor side current component in the two-phase rotating coordinate system, the proportional integral regulator and the rotor side voltage adjustment value are integrated.

[0206] The stator side reactive power As input in droop control, the stator side reactive power reference The difference between the sag coefficient and the Add the voltage amplitude setting value The stator side voltage amplitude reference value E is obtained, which is specifically expressed as:

[0207]

[0208] in, is the stator side reactive power, is the stator side reactive power reference value, is the droop coefficient, Set the value for the voltage amplitude.

[0209] In a specific embodiment, the stator side voltage amplitude reference value E and the stator side angular frequency reference value The resultant three-phase voltage on the stator side is expressed as:

[0210]

[0211] in, They are the voltages of the three-phase voltage on the stator side at both ends of each phase winding of the power supply or load.

[0212] Perform coordinate transformation on the three-phase voltage on the stator side, changing it from the three-phase stationary coordinate system to the two-phase rotating coordinate system, and obtain the stator side voltage reference value in the two-phase rotating coordinate system , specifically expressed as:

[0213]

[0214] in, is the stator side voltage reference value in the two-phase stationary coordinate system, is the stator side voltage reference value α component, is the stator side voltage reference value β component, is the stator side voltage reference value d component, is the stator side voltage reference value q component, is the first Park transformation matrix, is the Clarke transformation matrix.

[0215] Will As the reference value of the voltage outer loop input, the stator side voltage component in the two-phase rotating coordinate system As the feedback value, the difference between the two is adjusted by proportional integral regulator. Processing, output rotor side current reference value in two-phase rotating coordinate system , specifically expressed as:

[0216]

[0217] in, is the rotor side current reference value d component, is the rotor side current reference value q component, is the proportional-integral regulator of the rotor side voltage, S is the complex frequency domain variable in Laplace transform, is the proportional gain of the rotor side voltage, is the integral gain of the rotor side voltage.

[0218] In the current closed-loop control, the rotor side current reference value and rotor side current component The difference passes through the proportional integral regulator Processing, plus the rotor side voltage adjustment value That is, the rotor side target voltage reference value in the two-phase rotating coordinate system is obtained, which is specifically expressed as:

[0219]

[0220] in, is the rotor side target voltage reference value d component, is the q component of the rotor side target voltage reference value, is the proportional-integral regulator of the rotor side current, S is the complex frequency domain variable in Laplace transform, is the proportional gain of the rotor side current, is the integral gain of the rotor side current.

[0221] S107: Perform space vector pulse width modulation on the rotor-side target voltage reference value to generate a control signal to control the rotor-side converter in the doubly-fed generator.

[0222] Reference Figure 7 , specifically including:

[0223] Converting the rotor side target voltage reference value from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the rotor side target voltage α component and the rotor side target voltage β component;

[0224] Analyzing the amplitude and phase of the rotor-side target voltage according to the rotor-side target voltage α component and the rotor-side target voltage β component to determine the sector in which the rotor-side target voltage is located; wherein the rotor-side target voltage includes the rotor-side target voltage α component and the rotor-side target voltage β component;

[0225] Based on the sector where the rotor side target voltage is located, the effective vector and the zero vector are selected, and the vector action time is given;

[0226] According to the vector action time, a control signal required by the rotor-side converter is generated, and the rotor-side converter in the doubly-fed generator is controlled according to the control signal.

[0227] Space vector pulse width modulation (SVPWM) is a modulation technology used in three-phase inverters. It is mainly used to control the output voltage vector of the inverter to achieve high-efficiency and low-harmonic motor drive.

[0228] In a specific embodiment, the rotor side target voltage reference value is first converted from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the rotor side target voltage α component and the rotor side target voltage β component The sectors in which the rotor-side target voltage α and β components are located are then determined based on their amplitudes and phases. Based on the sector in which the rotor-side target voltage is located, two adjacent valid vectors and a zero vector are selected and the vector action time is calculated. Based on the vector action time, the duration of each switching state is assigned. Based on the assigned switching state, corresponding control signals are generated to control the inverter's switching operation.

[0229] Vector action time, specifically expressed as:

[0230]

[0231] in, is the total switching period, i.e. the total vector action time, and is the vector action time of two adjacent effective vectors, is the vector action time of zero vector, is the amplitude of the target voltage on the rotor side, is the DC bus voltage, is the switching frequency.

[0232] Reference Figure 8 In the control process of the droop control method of the double-fed gravity energy storage system based on electromagnetic torque provided by the embodiment of the present invention, the traditional active power-frequency droop control is replaced by the electromagnetic torque-frequency droop control. The electromagnetic torque-frequency droop control utilizes the electromagnetic torque reference value output by the rotor closed loop. , and the actual value of electromagnetic torque , and frequency setting value Let’s build the sag curve together:

[0233]

[0234] Different from the active power reference value in active power-frequency droop control Once set, it cannot be changed, but the electromagnetic torque reference value is used. When droop control is performed, when the rotor speed reference value When the load is changed, when the mechanical torque of the weight is changed, when the active power consumed by the load is changed, By constructing an adaptive electromagnetic torque-frequency droop curve and combining speed control with droop control, an adaptive droop control method is implemented, improving the grid support capacity of the doubly-fed gravity energy storage system.

[0235] In a specific example, an electromagnetic torque-frequency droop control model of a doubly fed gravity energy storage system is built in Simulink. When the load and weight torque remain unchanged, the rotor speed of the doubly fed motor is controlled: It can be seen that when the mechanical torque of the weight input to the doubly fed motor in the gravity energy storage is constant, the adaptive translation adjustment of the droop curve can be achieved by changing the rotor speed. When the rotor speed is stable, the electromagnetic torque reference value is -0.6; when the rotor speed rises, the electromagnetic torque is greater than -0.6; when the rotor speed drops, the electromagnetic torque is less than -0.6. The error between the actual value of the electromagnetic torque and the reference value will be directly reflected in the frequency of the droop control output. Different electromagnetic torques and their corresponding frequencies are extracted and curve fitting is performed. The curve can reflect that the droop characteristic constructed by the electromagnetic torque-frequency has an electromagnetic torque reference value. Adaptive translation capability. Among them, Simulink is a graphical programming environment based on MATLAB for multi-domain simulation and model design.

[0236] By building an electromagnetic torque-frequency droop control model for a doubly-fed gravity energy storage system in Simulink and conducting simulations, we show that the gravity energy storage system adjusts the power delivered to the load as the weight is applied, effectively adapting to load variations. During the simulation, the mechanical torque is matched to the load power. Specifically, the energy storage system applies the corresponding weight according to the power demanded by the load.

[0237] When the circuit working condition suddenly changes, the electromagnetic torque reference value fluctuates but eventually stabilizes at the corresponding mechanical torque value, so that in steady state, the error between the electromagnetic torque reference value and the actual electromagnetic torque value is almost 0. Through droop control, the frequency can be stabilized at 50Hz with almost no deviation. This also reflects that the electromagnetic torque reference value The closed-loop speed output allows for autonomous adjustment, shifting the droop curve to achieve zero frequency deviation during steady-state frequency adjustment. Furthermore, the speed remains well-maintained at the set value during steady-state operation, except for speed fluctuations caused by sudden operating changes.

[0238] Reference Figure 9 The embodiment of the present invention provides a droop control device for a doubly-fed gravity energy storage system based on electromagnetic torque, comprising:

[0239] The data acquisition module 201 is used to collect the stator side three-phase voltage, the stator side three-phase current, the rotor side three-phase current, the actual value of the electromagnetic torque and the rotor speed of the doubly fed motor;

[0240] The torque determination module 202 is configured to provide an electromagnetic torque reference value by using a proportional-integral regulator in combination with the rotor speed of the doubly-fed generator;

[0241] The phase determination module 203 is configured to perform droop control based on the electromagnetic torque reference value, the actual electromagnetic torque value, and the rotor speed to obtain a phase reference value and a phase slip;

[0242] A coordinate transformation module 204 is used to perform coordinate transformation on the stator side three-phase voltage, the stator side three-phase current, and the rotor side three-phase current according to the phase reference value and the phase slip, and provide a coordinate transformation result;

[0243] The flux calculation module 205 is used to calculate the flux according to the coordinate transformation result, and perform feedforward calculation based on the stator flux obtained by the flux calculation to provide a rotor side voltage adjustment value;

[0244] The voltage calculation module 206 is used to analyze the stator side voltage amplitude reference value according to the rotor side voltage adjustment value and the stator side reactive power, integrate the proportional integral regulator, and provide the rotor side target voltage reference value;

[0245] The control module 207 is configured to perform space vector pulse width modulation on the rotor-side target voltage reference value to generate a control signal for controlling the rotor-side converter in the doubly-fed generator.

[0246] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the described module can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0247] It should be noted that the computer-readable medium mentioned above in the present disclosure may be a computer-readable signal medium or a computer-readable storage medium, or any combination of the two. A computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or component, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to, an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device, or component. In the present disclosure, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, which carries computer-readable program code. This propagated data signal may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to wires, optical cables, RF (radio frequency), etc., or any suitable combination thereof.

[0248] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device.

[0249] Computer program code for performing the operations of the present disclosure may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0250] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, program segment or part of code, which contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the boxes can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart and the combination of boxes in the block diagram and / or flowchart can be implemented using a dedicated hardware-based system that performs the specified functions or operations, or can be implemented using a combination of dedicated hardware and computer instructions.

[0251] The units described in the embodiments of the present disclosure may be implemented in software or hardware, wherein the name of a unit does not necessarily limit the unit itself.

[0252] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A droop control method for a doubly fed gravity energy storage system based on electromagnetic torque, characterized in that: include: Collect the stator side three-phase voltage, stator side three-phase current, rotor side three-phase current, actual value of electromagnetic torque and rotor speed of the doubly fed generator; The electromagnetic torque reference value is given by the proportional-integral regulator in combination with the rotor speed of the doubly-fed generator; According to the electromagnetic torque reference value and the actual electromagnetic torque value, the change of the electromagnetic torque of the doubly fed motor is analyzed, and the torque difference between the electromagnetic torque reference value and the actual electromagnetic torque value is given; According to the torque difference, combined with the droop coefficient and the frequency setting value, the stator side frequency reference value is given, where the electromagnetic torque reference value is As the input of droop control, it is compared with the actual value of electromagnetic torque Combined processing to obtain the stator side frequency reference value , specifically expressed as: ; in, is the stator side frequency reference value, is the preset droop coefficient, f0 is the frequency setting value, is the electromagnetic torque reference value, is the actual value of electromagnetic torque; Integrate the stator side frequency reference value to obtain the phase reference value; According to the stator side frequency reference value and rotor speed, the change of the doubly fed generator rotor speed is analyzed and the speed slip is given; According to the speed slip, the phase slip is given; According to the phase reference value and phase slip, coordinate transformation is performed on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side, and the coordinate transformation result is given; The flux calculation is performed based on the coordinate transformation results. The stator flux obtained by the flux calculation is combined with the feedforward calculation to provide the rotor side voltage adjustment value. According to the rotor side voltage adjustment value, combined with the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional integral regulator to give the rotor side target voltage reference value, where the stator side reactive power Q S As input in droop control, the stator side reactive power reference The difference between it and the droop coefficient K Q Then add the voltage amplitude setting value E0 to get the stator side voltage amplitude reference value E, which is specifically expressed as: ; The rotor-side target voltage reference value is subjected to space vector pulse width modulation to generate a control signal for controlling the rotor-side converter in the doubly-fed generator.

2. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: The electromagnetic torque reference value is given by the proportional-integral regulator in combination with the rotor speed of the doubly-fed generator, including: According to the rotor speed of the doubly-fed generator and the rotor speed reference value, the change of the rotor speed of the doubly-fed generator is analyzed, and the speed difference between the rotor speed and the rotor speed reference value is given; Determine the proportional-integral regulator through the proportional gain and integral gain of the electromagnetic torque; Combining the proportional-integral regulator and the speed difference, the electromagnetic torque reference value is given.

3. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: Based on the electromagnetic torque reference value, combined with the actual electromagnetic torque value and the rotor speed, droop control is performed to obtain the phase reference value, specifically including: According to the electromagnetic torque reference value and the actual electromagnetic torque value, the change of the electromagnetic torque of the doubly fed motor is analyzed, and the torque difference between the electromagnetic torque reference value and the actual electromagnetic torque value is given; According to the torque difference, combined with the droop coefficient and the frequency setting value, the stator side frequency reference value is given; The stator side frequency reference value is integrated and calculated to obtain the phase reference value.

4. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: The coordinate transformation results include the stator side voltage component, stator side current component and rotor side current component in the two-phase rotating coordinate system; According to the phase reference value and phase slip, coordinate transformation is performed on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side, and the coordinate transformation results are given, including: The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given; According to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system; According to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system.

5. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1 or 4, characterized in that: The coordinate transformation is to transform the two-phase / three-phase stationary coordinate system into a two-phase rotating coordinate system.

6. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 4, characterized in that: The stator side voltage component in the two-phase stationary coordinate system includes the stator side voltage α component and the stator side voltage β component, the stator side current component in the two-phase stationary coordinate system includes the stator side current α component and the stator side current β component, and the rotor side current component in the two-phase stationary coordinate system includes the rotor side current α component and the rotor side current β component; The three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side are converted from the three-phase coordinate system to the two-phase stationary coordinate system, and the stator side voltage component, the stator side current component, and the rotor side current component in the two-phase stationary coordinate system are given, specifically including: Based on the Clarke transformation matrix, the coordinate transformation of the stator side three-phase voltage, the stator side three-phase current and the rotor side three-phase current in the three-phase coordinate system is performed respectively to obtain the corresponding stator side voltage α component, stator side voltage β component, stator side current α component, stator side current β component, rotor side current α component and rotor side current β component.

7. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 4, characterized in that: The stator side voltage component in the two-phase rotating coordinate system includes the stator side voltage d component and the stator side voltage q component, and the stator side current component in the two-phase rotating coordinate system includes the stator side current d component and the stator side current q component; According to the phase reference value, the stator side voltage component and the stator side current component are converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the stator side voltage component and the stator side current component in the two-phase rotating coordinate system, which specifically include: Determining a first Park transformation matrix according to the phase reference value; Based on the first Park transformation matrix, the stator side voltage component and the stator side current component in the two-phase stationary coordinate system are respectively transformed to obtain the corresponding stator side voltage d component, stator side voltage q component, stator side current d component and stator side current q component.

8. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 4, characterized in that: The rotor side current components in the two-phase rotating coordinate system include the rotor side current d component and the rotor side current q component; According to the phase slip, the rotor side current component is converted from the two-phase stationary coordinate system to the two-phase rotating coordinate system to obtain the rotor side current component in the two-phase rotating coordinate system, which specifically includes: Determine a second Park transformation matrix according to the phase slip; Based on the second Park transformation matrix, coordinate transformation is performed on the rotor side current components in the two-phase stationary coordinate system to obtain corresponding rotor side current d component and rotor side current q component.

9. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: The flux calculation is performed based on the coordinate transformation results. Combined with the stator flux obtained by the flux calculation, a feedforward calculation is performed to provide the rotor side voltage adjustment value, specifically including: According to the stator side voltage component and stator side current component in the two-phase stationary coordinate system in the coordinate transformation result, combined with the stator resistance, the stator flux in the two-phase stationary coordinate system is given; According to the first Park transformation matrix, combined with the stator flux in the two-phase stationary coordinate system, the stator flux in the two-phase rotating coordinate system is obtained; Based on the stator flux in the two-phase rotating coordinate system, combined with the rotor resistance, rotor leakage inductance, speed slip and mutual inductance, the rotor side voltage adjustment value is obtained.

10. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 9, characterized in that: The stator flux in the two-phase rotating coordinate system includes a stator flux d component and a stator flux q component, and the rotor side voltage adjustment value includes a rotor side voltage adjustment value d component and a rotor side voltage adjustment value q component; Based on the stator flux in the two-phase rotating coordinate system, combined with the rotor resistance, rotor leakage inductance, speed slip and mutual inductance, the rotor side voltage adjustment value is obtained, specifically including: The product of the rotor resistance and the rotor side current q component is taken as the first product; The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current d component is used as the second product; The product of the speed slip, the leakage inductance ratio and the stator flux d component is used as the third product, wherein the leakage inductance ratio is the ratio of the mutual inductance to the stator leakage inductance; The product of the rotor resistance and the rotor side current d component is taken as the fourth product; The product of the speed slip, the leakage inductance coefficient, the rotor leakage inductance and the rotor side current q component is taken as the fifth product; Add the first product, the second product and the third product to obtain the rotor side voltage adjustment value d component; The fifth product is subtracted from the fourth product to obtain the rotor side voltage adjustment value q component.

11. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: The stator-side reactive power is obtained by multiplying each stator-side line voltage component of the doubly-fed generator by the corresponding stator-side line current component.

12. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 11, characterized in that: The leakage inductance coefficient is obtained by stator leakage inductance, rotor leakage inductance and mutual inductance.

13. The droop control method of a double-fed gravity energy storage system based on electromagnetic torque according to claim 1 or 11, characterized in that: According to the rotor side voltage adjustment value, combined with the stator side reactive power, the stator side voltage amplitude reference value is analyzed and integrated into the proportional integral regulator to give the rotor side target voltage reference value, specifically including: Based on the power difference between the stator side reactive power and the stator side reactive power reference value, combined with the droop coefficient and the voltage amplitude setting value, a stator side voltage amplitude reference value is given; According to the stator side voltage amplitude reference value and the stator side angular frequency reference value, the stator side three-phase voltage in the three-phase stationary coordinate system is given, and the stator side three-phase voltage is transformed into a stator side voltage reference value in the two-phase rotating coordinate system; The voltage difference between the stator side voltage reference value and the stator side voltage component in the two-phase rotating coordinate system is analyzed, and the rotor side current reference value in the two-phase rotating coordinate system is given by combining the proportional integral regulator; A current closed loop is adopted to obtain the rotor side target voltage reference value based on the rotor side current reference value and the current difference of the rotor side current component in the two-phase rotating coordinate system, the proportional integral regulator and the rotor side voltage adjustment value are integrated.

14. The droop control method of the double-fed gravity energy storage system based on electromagnetic torque according to claim 1, characterized in that: Performing space vector pulse width modulation on the rotor-side target voltage reference value to generate a control signal to control the rotor-side converter in the doubly-fed generator, specifically including: Converting the rotor side target voltage reference value from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the rotor side target voltage α component and the rotor side target voltage β component; Analyze the amplitude and phase of the rotor-side target voltage according to the rotor-side target voltage α component and the rotor-side target voltage β component to determine the sector where the rotor-side target voltage is located; Based on the sector where the rotor side target voltage is located, the effective vector and the zero vector are selected, and the vector action time is given; According to the vector action time, a control signal required by the rotor-side converter is generated, and the rotor-side converter in the doubly-fed generator is controlled according to the control signal.

15. A droop control device for a double-fed gravity energy storage system based on electromagnetic torque, characterized in that: The droop control method of a doubly-fed gravity energy storage system based on electromagnetic torque according to any one of claims 1 to 14 is adopted, comprising: A data acquisition module is used to collect the stator side three-phase voltage, stator side three-phase current, rotor side three-phase current, actual value of electromagnetic torque and rotor speed of the doubly fed motor; The torque determination module is used to provide an electromagnetic torque reference value by combining the rotor speed of the doubly-fed generator through a proportional-integral regulator; The phase determination module is used to analyze the change of the electromagnetic torque of the doubly fed motor according to the electromagnetic torque reference value and the actual electromagnetic torque value, and provide the torque difference between the electromagnetic torque reference value and the actual electromagnetic torque value; according to the torque difference, combined with the droop coefficient and the frequency setting value, the stator side frequency reference value is provided, wherein the electromagnetic torque reference value is As the input of droop control, it is combined with the actual value of electromagnetic torque T e The stator side frequency reference value f is obtained by joint processing, which is specifically expressed as: ; Where, f is the stator side frequency reference value, is the preset droop coefficient, f0 is the frequency setting value, is the electromagnetic torque reference value, T e is the actual value of the electromagnetic torque; the stator side frequency reference value is integrated to obtain the phase reference value; based on the stator side frequency reference value and the rotor speed, the change of the doubly fed machine rotor speed is analyzed to give the speed slip; based on the speed slip, the phase slip is given; The coordinate transformation module is used to perform coordinate transformation on the three-phase voltage on the stator side, the three-phase current on the stator side, and the three-phase current on the rotor side according to the phase reference value and the phase slip, and provide the coordinate transformation result; The flux calculation module is used to calculate the flux according to the coordinate transformation results, and perform feedforward calculation based on the stator flux obtained by the flux calculation to provide the rotor side voltage adjustment value; The voltage calculation module is used to analyze the stator side voltage amplitude reference value according to the rotor side voltage adjustment value and the stator side reactive power, and integrate the proportional integral regulator to give the rotor side target voltage reference value, wherein the stator side reactive power Q S As input in droop control, the stator side reactive power reference The difference between it and the droop coefficient K Q Then add the voltage amplitude setting value E0 to get the stator side voltage amplitude reference value E, which is specifically expressed as: ; The control module is used to perform space vector pulse width modulation on the rotor side target voltage reference value to generate a control signal to control the rotor side converter in the doubly fed generator.

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