Converter instantaneous power stabilization control method and system under electromagnetic scale

Abstract

The invention discloses a converter instantaneous power stabilization control method and system under an electromagnetic scale, and the method comprises the steps: enabling the active power and reactive power of a converter to serve as an active power reference value and a reactive power reference value, and inputting the active power and reactive power into a power control loop of the converter, and obtaining an output current reference value of the converter; wherein the active power of the converter changes along with the change of the voltage amplitude of the capacitor; the reactive power of the converter changes along with the change of the capacitor voltage phase. By establishing the control logic between the reactive power output by the converter and the capacitor voltage phase and the control logic between the active power output by the converter and the capacitor voltage amplitude, the reactive power and the active power output by the converter are actively adjusted, and the phase stability and the energy stability of the new energy grid-connected system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy grid-connected control, and in particular to a method and system for controlling instantaneous power stabilization of a converter under electromagnetic scale. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The new energy grid-connected system refers to a system architecture that connects renewable energy such as wind energy and solar energy to the power system through power electronic equipment such as grid-connected converters to achieve energy supply. Its core lies in the coordination of the characteristics of new energy power generation with the traditional power system, including the regulation and control of frequency and voltage. The synchronous machine generates electricity through the rotation of the rotor, and due to its large inertia, it can better maintain the frequency stability of the power grid. In the synchronous machine system of the traditional power grid, due to the large inertia and long rotor flux time constant of the synchronous machine, and the slow response speed of the control execution unit (usually in the second level or even longer time range), the synchronous machine behaves as a voltage source on the electromagnetic scale, and its electromagnetic dynamic process is mainly a natural response under the excitation of the voltage source without control participation. The electromagnetic response process of the synchronous machine in a very short time lasts for a short time and is usually able to remain stable, so this process has not received enough attention for a long time.

[0004] The introduction of instantaneous power allows the concept of power to be extended to the dynamic process of the electromagnetic scale, including the description of various transient electrical quantities. The high-speed vector control of the converter based on instantaneous power allows the control of new energy power sources to penetrate into the instantaneous active and reactive power of the electromagnetic scale. The existing designs of instantaneous active and reactive control of new energy sources mostly refer to the dynamic mechanism of the electromechanical scale of traditional synchronous machine systems. However, at the electromagnetic scale, the converter control system of the new energy system can perform instantaneous power control on the electromagnetic time scale (usually within the millisecond range). When the converter of the new energy system adopts a control design similar to that of the synchronous machine, the response speed of the converter is much faster than that of the synchronous machine, and the existing controller may not be able to accurately capture and control these fast electromagnetic dynamics, resulting in the system being unable to adjust the power output in time, thereby causing unstable oscillations.

[0005] Existing technologies often adjust control parameters to increase the damping level of new energy stations at the resonant frequency to improve the stability of new energy grid connection. However, this method requires knowing the system oscillation frequency in advance, decomposing the corresponding frequency components after the oscillation occurs, and then adding damping resistance control. It can only be optimized around a certain oscillation frequency point. However, the cause and development mechanism of the oscillation of the new energy grid-connected system are still unclear, and there are many possibilities for broadband oscillation frequencies. Therefore, the regulation effect of this method is often not ideal. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a method and system for instantaneous power stabilization control of a converter under electromagnetic scale. By establishing the control logic between the reactive power output of the converter and the phase of the capacitor voltage, as well as the control logic between the active power output of the converter and the amplitude of the capacitor voltage, the reactive power and active power output of the converter are actively adjusted, thereby increasing the phase stability and energy stability of the new energy grid-connected system.

[0007] In some embodiments, the following technical solutions are adopted:

[0008] A method for controlling instantaneous power stabilization of a converter at an electromagnetic scale, comprising:

[0009] The active power and reactive power of the converter are input into the power control loop of the converter as the active power reference value and the reactive power reference value respectively, so as to obtain the output current reference value of the converter;

[0010] Among them, the active power of the converter changes with the change of the capacitor voltage amplitude.

[0011] As a further solution, the active power of the converter varies with the capacitor voltage amplitude, specifically:

[0012] P res =P res0 +K U (U C ref -U C );

[0013] Among them, P res is the active power of the converter after the change, P res0 is the actual active power output of the converter, K U is the active power droop coefficient, U C is the capacitor voltage amplitude, U C_ref is the capacitor voltage amplitude reference value.

[0014] As a further solution, it also includes: the reactive power of the converter changes with the change of the capacitor voltage phase.

[0015] As a further solution, the reactive power of the converter changes with the change of the capacitor voltage phase, specifically:

[0016] Q res =Q res0 +K θ (θ C -θ C_ref );

[0017] Among them, Q res is the reactive power of the converter after the change, Qres0 is the reactive power actually output by the converter, K θ is the reactive power droop coefficient, θ C is the capacitor voltage phase, θ C_ref is the capacitor voltage phase reference value.

[0018] As a further solution, after obtaining the output current reference value of the converter, it also includes: based on the current reference value, obtaining the three-phase modulation voltage of the converter through proportional integral control and coordinate transformation, and the three-phase modulation voltage is used to realize the control of the converter after PWM modulation.

[0019] In other embodiments, the following technical solutions are adopted:

[0020] An electromagnetic scale converter instantaneous power stabilization control system, comprising:

[0021] A power control module, used to input the active power and reactive power of the converter into the power control loop of the converter as an active power reference value and a reactive power reference value respectively, to obtain an output current reference value of the converter;

[0022] The active power control module is used to control the active power of the converter to change with the change of the capacitor voltage amplitude.

[0023] As a further option, it also includes:

[0024] The reactive power control module is used to control the reactive power of the converter to change with the change of the capacitor voltage phase.

[0025] In other embodiments, the following technical solutions are adopted:

[0026] A terminal device comprises a processor and a memory, wherein the processor is used to implement instructions; the memory is used to store a plurality of instructions, wherein the instructions are suitable for being loaded by the processor and executing the above-mentioned method for controlling instantaneous power stabilization of a converter under electromagnetic scale.

[0027] In other embodiments, the following technical solutions are adopted:

[0028] A computer-readable storage medium stores a plurality of instructions, wherein the instructions are suitable for being loaded by a processor of a terminal device and executing the above-mentioned method for controlling instantaneous power stabilization of a converter under electromagnetic scale.

[0029] In other embodiments, the following technical solutions are adopted:

[0030] A computer program product includes a computer program / instruction, which implements the above-mentioned method for controlling instantaneous power stabilization of a converter under electromagnetic scale when executed by a processor.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention constructs a control logic between the inverter reactive power and the capacitor voltage phase, and actively changes the reactive power output by the inverter when the capacitor voltage phase changes, so that the new energy grid-connected system can provide instantaneous reactive power to prevent the capacitor voltage phase from further changing, thereby stabilizing the system phase, thereby increasing the phase stability of the new energy grid-connected system.

[0033] (2) The present invention constructs a control logic between the active power of the converter and the capacitor voltage amplitude, and actively changes the active power output by the converter when the capacitor voltage amplitude changes, so that the new energy grid-connected system can provide instantaneous active power to prevent the capacitor voltage amplitude from further changing, thereby stabilizing the system energy, thereby increasing the energy stability of the new energy grid-connected system.

[0034] Other features and advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a typical schematic diagram of a new energy grid-connected system;

[0036] Figure 2 In the embodiment of the present invention, res =0.8pu,Q res = 0 when the characteristic value distribution diagram;

[0037] Figure 3 In the embodiment of the present invention, res0 =0.8pu, increase Q res -θ C Comparison chart of system characteristic values ​​before and after control;

[0038] Figure 4 In the embodiment of the present invention, res =0.8pu,Q res = 0 when the characteristic value distribution diagram;

[0039] Figure 5 In the embodiment of the present invention, res0 =-0.8pu, increase P res -U C Comparison chart of system characteristic values ​​before and after control;

[0040] Figure 6 A schematic diagram of a basic control structure of a new energy grid-connected converter in an embodiment of the present invention;

[0041] Figure 7In the embodiment of the present invention, Q is added res -θ C Control structure diagram;

[0042] Figure 8 In the embodiment of the present invention, P is added res -U C Control structure diagram;

[0043] Fig. 9 It is a simulation model of a new energy grid-connected system in an embodiment of the present invention;

[0044] 10(a)-(c) are respectively dynamic process diagrams of active power, reactive power and terminal voltage after disturbance in the state where the new energy generates active power according to an embodiment of the present invention;

[0045] Figure 11 (a)-(c) are respectively the additional Q in the embodiment of the present invention. res -θ C Simulation results of active power, reactive power and terminal voltage after control;

[0046] 12(a)-(c) are respectively dynamic process diagrams of active power, reactive power and terminal voltage after disturbance in the state of new energy absorbing active power in an embodiment of the present invention;

[0047] Figure 13 (a)-(c) are respectively the additional P in the embodiment of the present invention. res -U C Simulation results of active power, reactive power and terminal voltage after control. DETAILED DESCRIPTION

[0048] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0049] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0050] Embodiment 1

[0051] In one or more embodiments, a method for controlling instantaneous power stabilization of a converter at an electromagnetic scale is disclosed, specifically comprising:

[0052] The active power and reactive power of the converter are input into the power control loop of the converter as the active power reference value and the reactive power reference value respectively, so as to obtain the output current reference value of the converter;

[0053] Among them, the active power of the converter changes with the change of the capacitor voltage amplitude; the reactive power of the converter changes with the change of the capacitor voltage phase.

[0054] As a specific implementation method, the active power of the converter changes with the change of the capacitor voltage amplitude, specifically:

[0055] P res =P res0 +K U (U C_ref -U C );

[0056] Among them, P res is the active power of the converter after the change, P res0 is the actual output active power of the converter before the change, K U is the active power droop coefficient, U C is the capacitor voltage amplitude, U C_ref is the capacitor voltage amplitude reference value.

[0057] The reactive power of the converter changes with the capacitor voltage phase, specifically:

[0058] Q res =Q res0 +K θ (θ C -θ C_ref );

[0059] Among them, Q res is the reactive power of the converter after the change, Q res0 is the reactive power actually output by the converter before the change, K θ is the reactive power droop coefficient, θ C is the capacitor voltage phase, θ C_ref is the capacitor voltage phase reference value.

[0060] Specific, combined Figure 6 The basic control structure of the new energy grid-connected converter is shown in the figure. The control process of the converter is as follows:

[0061] The current transformer and the voltage transformer measure the voltage and current at the grid connection point respectively, and the voltage phase angle at the grid connection point is tracked through the phase-locked loop (PLL); the dq coordinate transformation of the voltage and current signals is realized, and the power control loop adopts constant power control to obtain the converter output current reference value, which is given to the current control loop. The current control loop adopts proportional integral PI control to obtain the converter modulation voltage, which is given to the converter after PWM modulation to realize control.

[0062] In the above-mentioned control process of the converter, the phase-locked loop PLL, coordinate conversion, current control loop and PWM modulation process are all conventional means that can be realized by the prior art; it should be noted that in this embodiment, the active power P of the converter is res and reactive power Q res As active reference value P ref and reactive power reference value Q ref Input into the power control loop; at the same time, the reactive power Q res pass Figure 7 The structure diagram shown in the figure realizes that the active power P res pass Figure 8 The structure diagram shown is implemented.

[0063] The method of this embodiment actively adjusts the reactive power and active power output by the converter by establishing the control logic between the reactive power output by the converter and the capacitor voltage phase, as well as the control logic between the active power output by the converter and the capacitor voltage amplitude, thereby increasing the phase stability and energy stability of the new energy grid-connected system.

[0064] The method of this embodiment is described in detail below.

[0065] (1) First, the mechanism of instantaneous active and reactive power of three-phase inductance and three-phase capacitance at the electromagnetic scale is explained.

[0066] For a three-phase inductor, the total energy stored is E L It can be expressed as:

[0067]

[0068] where i La ,i Lb ,i Lc is the instantaneous value of the three-phase inductor current. Assuming that there is no zero-sequence component, the park transformation of equation (1) can be obtained:

[0069]

[0070] Among them, L is the three-phase inductance value; i Ld is the d-axis component of the three-phase inductor current in the dq synchronous rotating coordinate system; i Lqis the q-axis component of the three-phase inductor current in the dq synchronous rotating coordinate system; I L is the three-phase inductor current amplitude.

[0071] It can be obtained that the total energy of the three-phase inductance is proportional to the square of the amplitude of the current space vector. The derivative of the instantaneous energy of the three-phase inductance is shown in (3):

[0072]

[0073] Its value is equal to the instantaneous active power P of the three-phase inductance L , the specific expression is as follows:

[0074]

[0075] Among them, u Ld and u Lq They are respectively the d-axis component and q-axis component of the three-phase inductor voltage in the dq synchronous rotating coordinate system.

[0076] The instantaneous active power on the three-phase inductor can replenish energy to the inductor and will affect the amplitude of its current space vector.

[0077] Instantaneous reactive power Q of three-phase inductance L and energy E L The relationship between them is shown in (5).

[0078]

[0079] Among them, θ L is the phase angle of the current vector on the three-phase inductor in the dq coordinate system; ω is the rotation angular velocity of the dq coordinate system.

[0080] The instantaneous reactive power on the three-phase inductor affects the rotation speed of the inductor current vector. Corresponding to a certain inductor energy (inductor current amplitude), a certain reactive power is required to maintain the rated electrical angular velocity rotation.

[0081] Similarly, a similar relationship can be obtained for the three-phase capacitors:

[0082]

[0083]

[0084] The instantaneous active power on the three-phase capacitor can charge the capacitor and will affect the amplitude of its voltage space vector.

[0085]

[0086] Among them, E C is the total energy stored in the three-phase capacitors, P Cis the instantaneous active power of the three-phase capacitor, Q C is the instantaneous reactive power of the three-phase capacitor, C is the three-phase capacitance value; u Ca 、u Cb 、u Cc is the abc axis component of the three-phase capacitor voltage in the abc three-phase stationary coordinate system; u Cd is the d-axis component of the three-phase capacitor voltage in the dq synchronous rotating coordinate system; u Cq is the q-axis component of the three-phase capacitor voltage in the dq synchronous rotating coordinate system; U C is the three-phase capacitor voltage amplitude; i Cd is the d-axis component of the three-phase capacitor current in the dq synchronous rotating coordinate system; i Cq is the q-axis component of the three-phase capacitor current in the dq synchronous rotating coordinate system; θ C is the phase angle of the voltage vector on the three-phase capacitor in the dq coordinate system.

[0087] The instantaneous capacitive reactive power on the three-phase capacitor affects the rotation speed of the capacitor voltage vector. Corresponding to a certain capacitor energy (capacitor voltage amplitude), a certain capacitive reactive power is required to maintain the rated electrical angular velocity rotation.

[0088] First determine E L and E C Base value:

[0089]

[0090] Among them, S B is the power base value, ω B is the base value of angular velocity, 1 / ω B is the time base value, S B / ω B is the energy base value, U C is the voltage base value, and the physical quantity with * represents the normalized parameter.

[0091] Therefore, the per-unit expressions of the three-phase inductance and three-phase capacitance can be obtained, and the per-unit values ​​are used in the following text unless otherwise specified:

[0092]

[0093] The active power of a three-phase LC element directly affects the change in its energy, which is then reflected in the change in the current and voltage amplitude; while the reactive power mainly affects the phase of the current or voltage. In the power system, the active and reactive power of the LC element depends on the type of power supply and the connection relationship between its components. When the system is disturbed, the state change of one component will affect the active and reactive power of another component, resulting in a complex coupling effect in the entire dynamic process. However, the rule that "the energy change of the LC element is determined by its active power, and the change in the current and voltage phase is determined by the reactive power" always holds true.

[0094] This law is different from the mechanism of action of active power affecting frequency and phase, and reactive power affecting voltage amplitude based on quasi-steady-state electrical quantities in traditional synchronous power systems. It is the mechanism of instantaneous active and reactive power at a more microscopic electromagnetic scale.

[0095] In summary, it can be concluded that the alternating energy flow does not jump from one quasi-steady state to another quasi-steady state, but needs to go through a transition change process at the electromagnetic scale. This embodiment analyzes the relationship between the energy and instantaneous power of the two types of energy storage elements, capacitors and inductors, in the three-phase circuit at the electromagnetic scale, and obtains the action mechanism of instantaneous active and reactive power at the electromagnetic scale, which is different from the quasi-steady-state active power affecting the frequency and phase and the reactive power affecting the voltage of the traditional synchronous machine, laying a theoretical foundation and providing analytical ideas for the subsequent analysis of the unstable oscillation problem at the electromagnetic scale of the new energy grid-connected system.

[0096] (2) Additional Q of the converter power control loop res -θ C Control to suppress instability in active output state; where Q res is the reactive power of the converter, θ C is the capacitor voltage phase.

[0097] For a typical renewable energy grid-connected system, such as Figure 1 As shown, E represents the infinite grid, L, R, and C represent the topological structure of the synchronous machine connected to the infinite system, the renewable energy performs instantaneous active and reactive power control, and a controlled current source model represents the renewable energy control structure.

[0098] for Figure 1 The new energy grid-connected system shown in the figure sets the system parameters as grid voltage E = 1.0 pu, inductance L = 0.3 pu, resistance R = 0.03 pu, and capacitance C = 0.1 pu. After ignoring the dynamic process of the new energy grid-connected PQ control, the dynamics of the system can be described by (12):

[0099]

[0100] By linearizing equation (12), we can obtain:

[0101]

[0102]

[0103] in,

[0104] Among them, P E , Q E Output active power and reactive power for infinite power grid; P RC , Q RC is the active and reactive power flowing from the inductor L to the resistor R and capacitor C; Q res The reactive power output by the new energy converter. The subscript of the parameter with 0 indicates the steady-state value or initial value of the corresponding parameter when the system is stable and no disturbance occurs; the parameter with Δ in front indicates the disturbance amount of the corresponding parameter of the system in the small signal analysis.

[0105] The first is the scenario of new energy outputting active power. res =0.8pu,Q res = 0 for output, the state space equation A matrix and the corresponding eigenvalue distribution of the new energy grid-connected system in the equilibrium state are shown in Table 1 and Figure 2 shown.

[0106] Table 1P res =0.8pu,Q res =0 when the matrix coefficient of A

[0107] -31.4159 <![CDATA[2.3817×10 3 ]]> 0.1851 -0.1055 <![CDATA[-1.3577×10 3 ]]> <![CDATA[-2.3817×10 3 ]]> -0.1055 <![CDATA[1.3552×10 -4 ]]> <![CDATA[-5.3315×10 5 ]]> <![CDATA[5.3315×10 5 ]]> -31.4159 <![CDATA[1.3577×10 3 ]]> <![CDATA[5.3315×10 5 ]]> <![CDATA[-9.3531×10 5 ]]> <![CDATA[-2.3817×10 3 ]]> <![CDATA[2.3817×10 3 ]]>

[0108] from Figure 2 It can be seen that when the new energy converter is in active output state, the system has a positive eigenvalue in the real part, and the system cannot remain stable. The reasons are analyzed below:

[0109] First, we analyze the coefficients of the A matrix in Table 1. 13 A 14 ; A 23 A 24 ] The coefficient of the submatrix formed is small. This shows that the energy E of L and C L and E C The changes in E L and E C The influence of L, C current and voltage phase is very limited. 13 A 14 ; A 23 A 24 ] is approximately regarded as a zero matrix, so the A matrix can be regarded as a block lower triangular matrix, as shown in (15).

[0110]

[0111] In this way, the amplitude dynamics and phase dynamics of the system approximately present decoupled characteristics. The amplitude dynamics are completely determined by A1. Although the phase dynamics will be affected by the amplitude dynamics, the decay speed and frequency of the new transient components contained in the phase dynamics are still only determined by A4. The eigenvalues ​​of A1 and A4 can approximately represent the eigenvalues ​​of the system and determine whether the system is stable or not.

[0112] In P res =0.8pu, the system eigenvalue determined by A1 is a negative real part eigenvalue, and the system eigenvalue determined by A4 is a positive real part eigenvalue. In this case, the instability of the system is mainly caused by the phase instability of LC in the system.

[0113] Then, the reasons for system instability can be summarized as follows: when the renewable energy output is instantaneous reactive power Q res When θ remains unchanged, C The change of the renewable energy grid-connected converter cannot provide the ability to prevent θ C To solve this problem, Q res With θ C The control logic between θ C Actively change Q when changing res , so that the new energy provides the blocking C The instantaneous reactive power is further changed to stabilize the system phase. This control logic is shown in equation (16):

[0114] Q res =Q res0 +K θ (θ C -θ C_ref ) (16)

[0115] Among them, Q res0 K is the reactive power output when the converter is not controlled. θ For additional Q res -θ C Controlled droop coefficient.

[0116] That is, when the voltage phase increases, the inductive instantaneous reactive power output increases (and the capacitive instantaneous reactive power output decreases), and when the voltage phase decreases, the inductive instantaneous reactive power output decreases (and the capacitive instantaneous reactive power output increases).

[0117] After adding such control, Figure 1 The system state space equation is shown in equation (17).

[0118]

[0119] The corresponding linearized equation is shown in equation (18):

[0120]

[0121] As mentioned above, the 0 in the table below the parameter indicates the steady-state value or initial value of the corresponding parameter before the system is disturbed.

[0122] In this way, without changing other elements in the state equation A matrix, A 44 It is converted into the form shown in formula (19).

[0123]

[0124] As long as K θ is a positive value, then this additional control can play a role in A 44 The reduction effect of A 44 It becomes a negative value, increasing the phase stability of the renewable energy grid-connected system.

[0125] Take K θ =1, compare with or without the additional Q res -θ C The eigenvalue results when controlling, such as Figure 3 It can be seen that: in the active output mode of the converter, the eigenvalues ​​of A1 and A4 are calculated to obtain that the real part of the eigenvalue of A4 is positive, and A4 reflects the state quantity of the current phase angle on L and the voltage phase angle on C. Therefore, the converter is in a phase unstable state in the active output mode.

[0126] In the additional Q res -θ C After the control, the two eigenvalues ​​strongly correlated with the A4 submatrix shifted significantly to the left, from the right half plane to the left half plane, and the new energy grid-connected system changed from unstable to stable. The two eigenvalues ​​strongly correlated with the A1 submatrix remained almost unchanged.

[0127] The above results show that when the renewable energy grid-connected system has phase instability in the active output mode, the additional Q res -θ C Control can help the system phase stabilize.

[0128] (3) Converter power control loop additional P res -U C Control suppression of instability in the active absorption state; where P res is the active power of the converter, U C is the capacitor voltage amplitude.

[0129] In the new energy res=-0.8pu, Q res = 0 for output (e.g., energy storage device charging operation), the state space equation A matrix and the corresponding eigenvalue distribution of the new energy grid-connected system in the equilibrium state are shown in Table 2 and Figure 4 shown.

[0130] Table 2P res =-0.8pu, Q res =0 when the matrix coefficient of A

[0131] -31.4159 <![CDATA[-2.6554×10 3 ]]> 0.2057 -0.0946 <![CDATA[1.2218×10 3 ]]> <![CDATA[2.6554×10 3 ]]> -0.0946 <![CDATA[1.2135×10 -4 ]]> <![CDATA[-4.798×10 5 ]]> <![CDATA[4.798×10 5 ]]> -31.4159 <![CDATA[-1.2218×10 3 ]]> <![CDATA[4.798×10 5 ]]> <![CDATA[-1.0428×10 6 ]]> <![CDATA[2.6554×10 3 ]]> <![CDATA[-2.6554×10 3 ]]>

[0132] from Figure 4 It can be seen that when the new energy converter is in the active absorption state, the system has a positive eigenvalue in the real part, and the system cannot remain stable; the reasons are analyzed below:

[0133] In P res =-0.8pu, the system eigenvalue determined by A1 is a positive real part eigenvalue, and the system eigenvalue determined by A4 is a negative real part eigenvalue. In this case, the instability of the system is mainly caused by the energy instability of LC in the system.

[0134] The reasons for instability can be summarized as follows: when the new energy output instantaneous active power P res If E remains unchanged, C The changes in the renewable energy grid-connected converter cannot provide the ability to prevent E C To solve this problem, we can establish P res With E C The control logic between E C Actively change P when changes occur res , so that new energy can provide protection against E C The instantaneous active power further changes to stabilize the system energy. This control process is shown in formula (20):

[0135] P res =P res0 +K E (E C_ref -E C ) (20)

[0136] But at the same time, considering E C To obtain the voltage U C It is also necessary to know the size of the capacitor C, which is more complicated. C and E C There is a positive correlation between them as shown in formula (9), so U C The change of E C Changes in P res , forming Pres -U control can also dampen the change of C energy.

[0137] Then the control process is shown in formula (21):

[0138] P res =P res0 +K U (U C_ref -U C ) (twenty one)

[0139] That is, when the voltage amplitude increases, the instantaneous active power output decreases, and when the voltage amplitude decreases, the instantaneous active power output increases. After adding such control, the system equation is shown in formula (22):

[0140]

[0141] The corresponding linearized equation is shown in (23):

[0142]

[0143] Without changing other elements in the system state space equation A matrix, A 22 is converted to (24):

[0144]

[0145] As long as K U is positive, then this additional control can play a role in A 22 The reduction effect of A 22 It becomes a negative value, increasing the energy stability of the renewable energy grid-connected system.

[0146] Take K U =1, in P res0 = -0.8pu, compare with and without the additional P res -U C The eigenvalue results when controlling, such as Figure 5 shown.

[0147] It can be seen that when P is added res -U C After the control, the two eigenvalues ​​strongly correlated with the A1 submatrix shifted significantly to the left, from the right half plane to the left half plane, and the system changed from unstable to stable. The two eigenvalues ​​strongly correlated with the A4 submatrix remained almost unchanged.

[0148] The above results show that when the renewable energy grid-connected system is in an unstable energy state under the active power absorption mode, the additional P res -U C Control can help stabilize system energy.

[0149] (4) Simulation Verification

[0150] use Fig. 9 The simulation model is built with the structure shown in the figure. In the initial equilibrium state, the new energy converter is set to emit active power. The converter outputs active power of 0.8pu and reactive power of 0p.u. At 0.01s, the system voltage is subjected to a small disturbance of -0.01pu. Through simulation, the dynamic processes of the active power, reactive power and terminal voltage of the grid-connected converter can be obtained as follows: Figure 10(a)-10(c) It can be seen that the voltage, active power and reactive power of the new energy grid-connected converter diverge and become unstable after the disturbance.

[0151] In the case of active output of the new energy grid-connected converter, the Q of this embodiment is added to the grid-connected converter system where the voltage disturbance is unstable. res -θ C Control, where K θ Take 1, the simulation results are as follows Figure 11(a)-11(c) As shown, it can be seen that after adding this control, the active power, reactive power and terminal voltage of the converter after the disturbance can be quickly stabilized, and the dynamic characteristics are good.

[0152] Similarly, in the initial equilibrium state, the new energy converter is set to absorb active power, and the converter outputs -0.3pu active power and 0p.u. reactive power. At 0.01s, the system voltage is subjected to a small disturbance of -0.01pu. Through simulation, the dynamic processes of the active power, reactive power and terminal voltage of the grid-connected converter at this time can be obtained as follows: Figure 12(a)-12(c) As shown in the figure, it can be seen that the new energy grid-connected converter will also experience divergent instability of terminal voltage, active power and reactive power after disturbance.

[0153] In the case of active absorption of the new energy grid-connected converter, the P of this embodiment is added to the grid-connected converter system where the voltage disturbance is unstable. res -U C Control, where K U Take 1, the simulation results are as follows Figure 13(a)-13(c) As shown, it can be seen that after adding this control, the active power, reactive power and terminal voltage of the converter can be quickly stabilized after the voltage disturbance, and the dynamic characteristics are good.

[0154] Embodiment 2

[0155] In one or more embodiments, a control system for instantaneous power stabilization of a converter at an electromagnetic scale is disclosed, comprising:

[0156] A power control module, used to input the active power and reactive power of the converter into the power control loop of the converter as an active power reference value and a reactive power reference value respectively, to obtain an output current reference value of the converter;

[0157] The active power control module is used to control the active power of the converter to change with the change of the capacitor voltage amplitude.

[0158] The reactive power control module is used to control the reactive power of the converter to change with the change of the capacitor voltage phase.

[0159] The specific implementation of the above modules is the same as that in Example 1 and will not be described in detail.

[0160] Embodiment 3

[0161] In one or more embodiments, a terminal device is disclosed, which includes a processor and a memory, the processor is used to implement instructions; the memory is used to store multiple instructions, and the instructions are suitable for being loaded by the processor and executing the electromagnetic scale converter instantaneous power stabilization control method described in Example 1.

[0162] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0163] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0164] In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software.

[0165] Embodiment 4

[0166] In one or more embodiments, a computer-readable storage medium is disclosed, in which a plurality of instructions are stored, wherein the instructions are suitable for being loaded by a processor of a terminal device and executing the method for controlling instantaneous power stabilization of a converter at an electromagnetic scale described in Example 1.

[0167] Embodiment 5

[0168] In one or more embodiments, a computer program product is disclosed, including a computer program / instruction, which, when executed by a processor, implements the method for controlling instantaneous power stabilization of a converter at an electromagnetic scale described in Embodiment 1.

[0169] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for controlling the instantaneous power stabilization of a converter at an electromagnetic scale, characterized in that: include: The active power and reactive power of the converter are input into the power control loop of the converter as the active power reference value and the reactive power reference value respectively, so as to obtain the output current reference value of the converter; Among them, the active power of the converter changes with the change of the capacitor voltage amplitude.

2. The method for controlling the instantaneous power stabilization of a converter under electromagnetic scale according to claim 1, characterized in that: The active power of the converter changes with the change of the capacitor voltage amplitude, specifically: P res =P res0 +K U (IN C_ref -IN C ); Among them, P res is the active power of the converter after the change, P res0 is the actual active power output of the converter, K U is the active power droop coefficient, U C is the capacitor voltage amplitude, U C_ref is the capacitor voltage amplitude reference value.

3. The method for controlling the instantaneous power stabilization of a converter under electromagnetic scale according to claim 1, characterized in that: Also includes: The reactive power of the converter changes with the phase of the capacitor voltage.

4. The method for controlling the instantaneous power stabilization of a converter under electromagnetic scale according to claim 3, characterized in that: The reactive power of the converter changes with the capacitor voltage phase, specifically: Q res =Q res0 +K θ (i C -θ C_ref ); Among them, Q res is the reactive power of the converter after the change, Q res0 is the reactive power actually output by the converter, K θ is the reactive power droop coefficient, θ C is the capacitor voltage phase, θ C_ref is the capacitor voltage phase reference value.

5. The method for controlling the instantaneous power stabilization of a converter in an electromagnetic scale according to claim 1, characterized in that: After obtaining the output current reference value of the converter, it also includes: based on the current reference value, obtaining the three-phase modulation voltage of the converter through proportional integral control and coordinate transformation, and the three-phase modulation voltage is used to realize the control of the converter after PWM modulation.

6. An electromagnetic scale converter instantaneous power stabilization control system, characterized in that: include: A power control module, used to input the active power and reactive power of the converter into the power control loop of the converter as an active power reference value and a reactive power reference value respectively, to obtain an output current reference value of the converter; The active power control module is used to control the active power of the converter to change with the change of the capacitor voltage amplitude.

7. The electromagnetic scale converter instantaneous power stabilization control system according to claim 6, characterized in that: Also includes: The reactive power control module is used to control the reactive power of the converter to change with the change of the capacitor voltage phase.

8. A terminal device, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions, characterized in that: The instructions are suitable for being loaded by a processor and executing the method for controlling instantaneous power stabilization of an electromagnetic scale converter as described in any one of claims 1 to 5.

9. A computer-readable storage medium storing a plurality of instructions, characterized in that: The instruction is suitable for being loaded by a processor of a terminal device and executing the method for controlling instantaneous power stabilization of an electromagnetic scale converter as described in any one of claims 1 to 5.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the method for controlling the instantaneous power stabilization of a converter at an electromagnetic scale as described in any one of claims 1 to 5 is implemented.

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