Reactive power synchronous control inverter supporting grid voltage control method and system

Abstract

A method and system for inverter-supported grid voltage control with reactive power synchronization control is presented. When the grid voltage drops, the system collects the inverter's output reactive power deviation, output current command value, grid voltage drop coefficient, and grid voltage phase. A primary voltage regulation model is used to correct the inverter's output reactive power deviation. The reactive power synchronization model obtains the grid frequency deviation based on the corrected value of the inverter's output reactive power deviation. The phase angle model outputs the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint. The inverter's output current phase is determined based on the reactive power synchronization phase angle and the inverter's output current command value. The inverter's output reactive power command value is determined based on the grid voltage drop coefficient and the difference between the grid voltage phase and the inverter's output current phase. The inverter is then controlled according to the output reactive power command value, providing active reactive power support during grid voltage drops.

Description

Technical Field

[0001] This invention belongs to the field of AC power transmission control technology, specifically relating to an inverter-supported grid voltage control method and system for reactive power synchronous control. Background Technology

[0002] Inverters, as crucial devices for power conversion, comprise main circuits and control sections. Existing technologies commonly employ grid-tracking control methods, including vector current loops (PLLs) and phase-locked loops (PLLs). The vector current loop is used for rapid output current control, while the PLL is used for grid synchronization, tracking the frequency and phase of the terminal voltage. Based on this, the inverter adjusts the internal potential amplitude and phase according to current control requirements. Therefore, the PLL is critical in inverter control. However, in existing grid-tracking control methods, the introduction of the PLL inevitably introduces negative resistance into the inverter, easily triggering subsynchronous / supersynchronous oscillations and leading to system instability.

[0003] To address this issue, a phase-locked loop (PLL)-free grid-based control method simulating or partially simulating synchronous machine characteristics has been proposed, including droop control and virtual synchronous generator (VSG) control. Droop control enables autonomous power allocation between parallel inverters without communication, while VSG simulates the rotor motion equations of a synchronous machine, using control methods to analogize the damping and inertia of the synchronous machine and provide reactive power support to the grid. Furthermore, power synchronous control (PSC), possessing similar characteristics to VSG, has been proposed. PSC utilizes single-integration to convert power fluctuations into angular offsets, resulting in higher stability margins. PSC enhances the stability of inverters connected to weak grids and expands the power control range. Combining PSC with current-source control not only ensures good stability characteristics in weak grids but also improves the system's response speed and transient fault current-limiting capability. PSC can be categorized into active power synchronization, reactive power synchronization, and composite power synchronization based on the synchronization medium. Active power synchronization control, by analogy with the instantaneous power transfer mechanism, enables active power support during grid frequency dips, but it cannot respond to grid voltage dips. Reactive power synchronization can achieve accurate synchronization under special conditions such as uncontrollable active power, but existing reactive power synchronization inverters cannot improve response speed and achieve rapid reactive power compensation during grid voltage dips based on reactive power control. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and system for inverter-supported grid voltage control based on reactive power synchronization control. Based on a reactive power synchronization control method, and leveraging the reactive power tracking characteristics of the power synchronization loop itself, it achieves proactive reactive power support from the inverter during grid voltage dips. Building upon the traditional reactive power synchronization loop control architecture, analogous to the dynamic voltage restorer in a synchronous generator, a primary voltage regulation coefficient is introduced to realize the transformation from frequency deviation to power command value enhancement, providing transient power support to the grid. Furthermore, to achieve rapid response during voltage dips, an adaptive adjustment control of the power synchronization coefficient based on voltage detection is proposed, which improves response speed and enables rapid reactive power support during grid voltage dips.

[0005] The present invention adopts the following technical solution.

[0006] This invention proposes a method for inverter-supported grid voltage control with reactive power synchronous control, comprising:

[0007] Establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model;

[0008] When the grid voltage drops, the inverter's output reactive power deviation, the inverter's output current command value, the grid voltage drop coefficient, and the grid voltage phase are collected.

[0009] The inverter's output reactive power deviation is corrected using a primary voltage regulation model. The grid frequency deviation is obtained using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation. The reactive power synchronization phase angle is output using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. The inverter's output current phase is determined based on the reactive power synchronization phase angle and the inverter's output current command value. The inverter's output reactive power command value is determined based on the grid voltage drop factor and the difference between the grid voltage phase and the inverter's output current phase. The inverter is then controlled based on the inverter's output reactive power command value.

[0010] Preferably, the primary voltage regulation model takes the grid frequency deviation output by the reactive power synchronization model as input, obtains the reactive power compensation amount caused by the grid voltage drop based on the primary voltage regulation coefficient and the grid frequency deviation, and uses the reactive power compensation amount to correct the output reactive power deviation of the inverter.

[0011] After a voltage regulation model correction, the reactive power synchronization model takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation.

[0012] The phase angle model is used to output the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

[0013] Preferably, the reactive power synchronization phase angle model satisfies the following relationship:

[0014]

[0015] In the formula, θ QSC The reactive power synchronization phase angle is ω, the grid frequency is s, and the frequency domain operation symbol is ω. ref Given the grid frequency, q ref S is the inverter's output reactive power command value, q is the inverter's actual output reactive power value, and S is the reactive power output of the inverter. n k is the rated capacity of the inverter. q This is the reactive power synchronization coefficient.

[0016] Preferably, the correction value of the inverter's output reactive power deviation obtained after one voltage regulation model correction satisfies the following relationship:

[0017] Δq=q ref -q+D·Δω

[0018] In the formula, Δq is the correction value for the output reactive power deviation of the inverter, and q ref q is the output reactive power command value of the inverter, q is the actual output reactive power value of the inverter, D is the primary voltage regulation coefficient, and Δω is the grid frequency deviation.

[0019] When the grid voltage does not drop, the difference between the inverter's output reactive power command value and the actual value is the inverter's output reactive power deviation.

[0020] Preferably, the power grid frequency deviation satisfies the following relationship:

[0021]

[0022] In the formula, k q S is the reactive power synchronization coefficient. n This refers to the rated capacity of the inverter.

[0023] Preferably, the reactive power synchronization phase angle satisfies the following relationship:

[0024]

[0025] In the formula, θ QSC The reactive power synchronization phase angle, ω ref s is the given value for the power grid frequency, and s is the frequency domain operator.

[0026] Preferably, the grid voltage drop factor is the ratio of the actual grid voltage value to the commanded value;

[0027] When the grid voltage drop factor is not less than the set threshold, the reactive power synchronization factor ranges from [0.01, 200].

[0028] When the grid voltage drop coefficient is less than the set threshold, the reactive power synchronization coefficient ranges from [500, 4000].

[0029] The threshold value is set to be no less than 0.9.

[0030] Preferably, depending on the different values ​​of the reactive power synchronization coefficient, the primary voltage regulation coefficient satisfies the following relationship:

[0031] D=α·D0

[0032] In the formula, when the grid voltage drop coefficient is not less than the set threshold, the value of α is 1; when the grid voltage drop coefficient is less than the set threshold, the value of α is 0.08% of the reactive power synchronization coefficient; D0 is the initial value of the primary voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified by the standard, the value of D0 is 0; when the grid frequency deviation exceeds the allowable deviation range specified by the standard, D0 is the base value of the reactive power droop control coefficient.

[0033] Preferably, determining the inverter output current phase based on the reactive power synchronization phase angle and the inverter output current command value includes:

[0034] Based on the inverter output current command value, the initial phase of the inverter output current is determined using the following formula:

[0035]

[0036] In the formula, I dref I qref These represent the d-axis and q-axis components of the inverter's output current command, respectively. I represents the initial phase of the inverter output current, and I represents the peak value of the phase current in the inverter output current command.

[0037] The phase of the inverter output current is obtained by calculating the difference between the reactive power synchronization phase angle and the initial phase of the inverter output current using the following formula:

[0038]

[0039] In the formula, θ represents the phase of the inverter output current. QSC This is the reactive power synchronization phase angle.

[0040] Preferably, the command value for the inverter's output reactive power is determined based on the grid voltage sag coefficient and the difference between the collected grid voltage phase and the inverter output current phase, including:

[0041] The difference between the acquired grid voltage phase and the inverter output current phase is calculated using the following formula:

[0042]

[0043] In the formula, This is the difference between the phase of the collected grid voltage and the phase of the inverter output current. The phase of the grid voltage;

[0044] The inverter's output reactive power command value is determined by the following relationship:

[0045]

[0046] In the formula, k drop U is the grid voltage sag factor, which is the ratio of the actual grid voltage value to the commanded value. ref This is the inverter output voltage command value.

[0047] Preferably, the reactive power command value output by the inverter satisfies the following relationship:

[0048] q ref =-1.5U ref I qref

[0049] In the formula, U ref I is the inverter output voltage command value. qref This represents the q-axis component of the inverter's output current command.

[0050] This invention also proposes an inverter-supported grid voltage control system for reactive power synchronous control, comprising: a model module, a data acquisition module, and a control module;

[0051] The model module is used to establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model.

[0052] The data acquisition module is used to collect the inverter's output reactive power deviation, inverter's output current command value, grid voltage drop coefficient, and grid voltage phase when the grid voltage drops.

[0053] The control module is used to correct the inverter's output reactive power deviation using a primary voltage regulation model, obtain the grid frequency deviation using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation, and output the reactive power synchronization phase angle using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. It determines the inverter's output current phase based on the reactive power synchronization phase angle and the inverter's output current command value; determines the inverter's output reactive power command value based on the grid voltage drop factor and the difference between the grid voltage phase and the inverter's output current phase; and controls the inverter based on the output reactive power command value.

[0054] Preferably, the model module includes: a primary voltage regulation unit, a reactive power synchronization unit, and a phase angle unit; wherein,

[0055] The primary voltage regulation unit takes the grid frequency deviation output by the reactive power synchronization model as input, obtains the reactive power compensation caused by the grid voltage drop based on the primary voltage regulation coefficient and the grid frequency deviation, and uses the reactive power compensation to correct the output reactive power deviation of the inverter.

[0056] After a voltage regulation unit correction, the reactive power synchronization unit takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation.

[0057] The phase angle unit outputs the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

[0058] Preferably, the model module further includes: a grid voltage sag coefficient adjustment unit and a primary voltage regulation coefficient adjustment unit; wherein,

[0059] The grid voltage sag coefficient adjustment unit is used to set the reactive power synchronization coefficient to a value range of [0.01, 200] when the grid voltage sag coefficient is not less than a set threshold, and the reactive power synchronization coefficient to a value range of [500, 4000] when the grid voltage sag coefficient is less than a set threshold. The set threshold value range is not less than 0.9. The grid voltage sag coefficient is the ratio of the actual grid voltage value to the commanded value.

[0060] The primary voltage regulation coefficient adjustment unit is used to calculate the primary voltage regulation coefficient according to the different values ​​of the reactive power synchronization coefficient, using the following formula:

[0061] D=α·D0

[0062] In the formula, when the grid voltage drop coefficient is not less than the set threshold, the value of α is 1; when the grid voltage drop coefficient is less than the set threshold, the value of α is 0.08% of the reactive power synchronization coefficient; D0 is the initial value of the primary voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified by the standard, the value of D0 is 0; when the grid frequency deviation exceeds the allowable deviation range specified by the standard, D0 is the base value of the reactive power droop control coefficient.

[0063] Preferably, the control module includes: an inverter output current phase calculation unit and an inverter output reactive power command value calculation unit; wherein,

[0064] The inverter output current phase calculation unit is used to calculate the initial phase of the inverter output current based on the inverter output current command value, calculate the difference between the reactive power synchronization phase angle and the initial phase of the inverter output current, and obtain the phase of the inverter output current.

[0065] The inverter output reactive power command value calculation unit is used to calculate the difference between the collected grid voltage phase and the inverter output current phase, and determines the inverter output reactive power command value according to the following relationship:

[0066]

[0067] In the formula, k drop U is the grid voltage sag factor, which is the ratio of the actual grid voltage value to the given value. ref This is the inverter output voltage command value.

[0068] A terminal includes a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of a method.

[0069] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of a method.

[0070] The beneficial effects of this invention, compared with the prior art, include at least the following: By studying the structure of the reactive power synchronization loop in a power synchronous inverter and utilizing the error-free tracking characteristics of its built-in integral element, lossless reactive power output can be achieved during grid voltage dips without the need for additional components. Specifically, by adjusting the phase locked by the power synchronization loop, the phase difference between voltage and current is increased, thereby maintaining the inverter's output reactive power at the level before the grid voltage dip, providing reactive power compensation to the grid without introducing overcurrent risk to the inverter. Furthermore, by adding a voltage dip detection element and a real-time reactive power synchronization coefficient adjustment system, key parameters affecting response speed are coupled with the grid voltage state to achieve rapid response of the reactive power synchronization loop, improve phase-locking speed, and thus enhance the reactive power support response speed under grid voltage dips. Attached Figure Description

[0071] Figure 1 This invention presents a flowchart of an inverter-supported grid voltage control method for reactive power synchronous control.

[0072] Figure 2 This is a block diagram of the reactive power synchronization loop control in the embodiment;

[0073] Figure 3 This is a comparison chart of theoretical analysis and simulation results of reactive power synchronization loop output phase under grid voltage drop in the embodiment;

[0074] Figure 4 The simulation results of the inverter's output active and reactive power under grid voltage dips in the embodiment are shown.

[0075] Figure 5 The simulation results show the active and reactive power output of the inverter after adopting the response speed optimization control strategy in the embodiment. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0077] This invention proposes a method for inverter-supported grid voltage control with reactive power synchronous control.

[0078] Establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model;

[0079] When the grid voltage drops, the inverter's output reactive power deviation, the inverter's output current command value, the grid voltage drop coefficient, and the grid voltage phase are collected.

[0080] The inverter's output reactive power deviation is corrected using a primary voltage regulation model. The grid frequency deviation is obtained using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation. The reactive power synchronization phase angle is output using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. The inverter's output current phase is determined based on the reactive power synchronization phase angle and the inverter's output current command value. The inverter's output reactive power command value is determined based on the grid voltage drop factor and the difference between the grid voltage phase and the inverter's output current phase. The inverter is then controlled based on the inverter's output reactive power command value.

[0081] The method proposed in this invention adjusts the reactive power synchronization phase angle based on the reactive power synchronization phase angle model when the grid voltage drops, according to the inverter output current command value and the grid voltage phase, so that the inverter output reactive power is maintained at the level before the grid voltage drops, thereby achieving active reactive power support and rapid response under grid voltage drops.

[0082] like Figure 1 As shown, the control methods include:

[0083] Step 1: Collect the actual value of reactive power output by the inverter. Based on the active power synchronous phase angle model, establish the reactive power synchronous phase angle model, including the primary voltage regulation model, the reactive power synchronization model, and the phase angle model.

[0084] During the instantaneous power transfer between synchronous motors, the generator transfers energy to the motor through the reactance, forming an electrical energy transmission system. The system's power during stable operation is:

[0085]

[0086] In the formula, U INV U is the generator port output voltage. PCC X is the voltage at the motor, X is the reactance, δ is the power angle, and δ is the potential angle between the generator and the motor.

[0087] WhenU INV Advanced U PCC When δ is positive, the generator supplies power to the motor.

[0088] When the inverter uses a control method mediated by active power to maintain synchronization, the active power synchronization phase angle model satisfies the following relationship:

[0089]

[0090] In the formula, Pref S is the setpoint for the inverter's output active power, p is the actual value of the inverter's output active power, and S is the value of the active power. n ω is the rated capacity of the inverter, and ω is the grid frequency detected by the power synchronization loop. ref Given the grid frequency, k p θ is the active power synchronization coefficient, s is the frequency domain operation symbol, and θ is the frequency domain operation symbol. PSC The phase angle is the output phase angle of the active power synchronization loop.

[0091] Generally, as an approximation of a synchronous motor, the instantaneous power transfer behavior of a synchronous motor is mimicked by establishing a relationship between the inverter's output active power and frequency. However, in an inverter, there is no necessary connection between the phase of the electrical variable and the mechanical system that needs to restore its position through synchronizing torque. Therefore, the inverter lacks the inherent requirement to link active power deviation with phase angle offset to achieve system synchronization. It is evident that power synchronization methods use power as the medium for the synchronization process, and traditionally, active power is generally chosen as the synchronization medium. When the active power required for the synchronization process is uncontrollable, the required instantaneous active power transfer cannot be guaranteed, and the synchronization mechanism will fail. Therefore, in unity power factor operation, reactive power is chosen as the synchronization medium, and synchronization is achieved through the dynamic relationship between reactive power deviation and phase angle offset.

[0092] The reactive power synchronization phase angle model proposed in this invention satisfies the following relationship:

[0093]

[0094] q ref =-1.5U ref I qref (4)

[0095] In the formula, θ QSC The reactive power synchronization phase angle is ω, the grid frequency is s, and the frequency domain operation symbol is ω. ref Given the grid frequency, q ref S is the inverter's output reactive power command value, q is the inverter's actual output reactive power value, and S is the reactive power output of the inverter. n k is the rated capacity of the inverter. q U is the reactive power synchronization coefficient. ref I is the peak value of the rated phase voltage of the power grid. qref This represents the q-axis component of the inverter's output current command.

[0096] The primary voltage regulation model takes the grid frequency deviation output by the reactive power synchronization model as input. Based on the primary voltage regulation coefficient and the grid frequency deviation, the reactive power compensation caused by the grid voltage drop is obtained. The reactive power compensation is then used to correct the output reactive power deviation of the inverter.

[0097] After a voltage regulation model correction, the reactive power synchronization model takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation.

[0098] The phase angle model is used to output the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

[0099] The correction value of the inverter's output reactive power deviation, obtained after one voltage regulation model correction, satisfies the following relationship:

[0100] Δq=q ref -q+D·Δω

[0101] In the formula, Δq is the correction value for the output reactive power deviation of the inverter, and q ref q is the output reactive power command value of the inverter, q is the actual output reactive power value of the inverter, D is the primary voltage regulation coefficient, and Δω is the grid frequency deviation.

[0102] When the grid voltage does not drop, the difference between the inverter's output reactive power command value and the actual value is the inverter's output reactive power deviation.

[0103] In a non-limiting preferred embodiment, the primary voltage regulation coefficient D ranges from [40, 320].

[0104] like Figure 2 As shown, the reactive power synchronization phase angle model includes: primary voltage regulation model, reactive power synchronization model and phase angle model.

[0105] Figure 2 In this context, Δq represents the output reactive power deviation of the inverter. * The per-unit inverter output reactive power deviation, Δθ is the phase angle deviation, and θ is the phase angle deviation. ref Here, angular frequency is the given value, and D is the primary voltage regulation coefficient. In the reactive power synchronous phase angle model proposed in this invention, the per-unit inverter output reactive power deviation Δq * Synchronization coefficient k with reactive power q The product is the grid frequency deviation Δω, which is converted into the phase angle deviation Δθ by the integral operator 1 / s. The phase angle deviation Δθ is then compared with the angular frequency setpoint θ corresponding to the grid frequency setpoint. ref Superimposed, the reactive power synchronization phase angle θ is obtained. QSC Furthermore, after the voltage regulation coefficient is applied once, Δω is related to the inverter's output reactive power command value q. ref The output reactive power deviation of the inverter is obtained by superimposing the actual values ​​q of the inverter's output reactive power. Reactive power synchronization phase angle θQSC It provides the angle required to transform the inverter output vector from the synchronous rotating coordinate system to the stationary coordinate system.

[0106] From equation (3), we can see that the reactive power synchronization phase angle model starts from the reactive power level and uses the reactive power synchronization coefficient k. q The process transforms reactive power difference into frequency deviation. The obtained frequency deviation is summed with the grid frequency setpoint to obtain the actual grid frequency. After integration, the output phase of the power synchronization loop is obtained, thereby achieving successful phase-locking of the grid voltage.

[0107] Step 2: When the grid voltage drops, collect the inverter's output reactive power deviation, the inverter's output current command value, the grid voltage drop coefficient, and the grid voltage phase.

[0108] Specifically, the grid voltage drop factor is the ratio of the actual grid voltage value to the commanded value;

[0109] When the grid voltage drop factor is not less than the set threshold, the reactive power synchronization factor ranges from [0.01, 200].

[0110] When the grid voltage drop coefficient is less than the set threshold, the reactive power synchronization coefficient ranges from [500, 4000].

[0111] The threshold value is set to be no less than 0.9.

[0112] Due to the presence of the integral element in the reactive power synchronization loop, the actual reactive power value q output by the inverter can achieve the reactive power command value q output by the inverter. ref Accurate tracking. (By q) ref From the calculation formula (4), we can see that the reactive power command value output by the inverter is calculated based on the grid voltage level to which the inverter is connected, and the reactive power command value will not be affected by grid voltage drops. For example, for an inverter connected to a 380V voltage system, even if a grid voltage drop occurs, q ref The calculation formula remains -1.5 × 311 × I qref At this time, the reactive power synchronization loop can accurately track the reactive power command value of the inverter output, so that the reactive power output of the inverter is maintained at the level before the grid voltage drop, thereby providing reactive power support to the grid.

[0113] Step 3: Use the primary voltage regulation model to correct the inverter's output reactive power deviation; use the reactive power synchronization model to obtain the grid frequency deviation based on the corrected value of the inverter's output reactive power deviation; use the phase angle model to output the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint; determine the inverter's output current phase based on the reactive power synchronization phase angle and the inverter's output current command value; determine the inverter's output reactive power command value based on the grid voltage drop factor and the difference between the grid voltage phase and the inverter's output current phase; control the inverter based on the inverter's output reactive power command value.

[0114] In a three-phase power grid, the formula for calculating the system reactive power is as follows:

[0115]

[0116] In the formula, U is the actual peak phase voltage of the power grid; I is the peak phase current of the inverter output, and its calculation formula is shown in (6); The phase difference between the grid voltage and the inverter output current satisfies The phase of the grid voltage. This refers to the phase of the inverter output current.

[0117]

[0118] In the formula, I dref This is the d-axis current command value output by the inverter.

[0119] If a grid voltage drop occurs, U decreases proportionally, and the vector current loop in the inverter will control I to track the command value. At this time, to maintain the inverter's output reactive power at the level before the voltage drop, it is only possible to adjust the phase-locked loop phase through the reactive power synchronization loop, increasing the phase difference between voltage and current, thereby providing active reactive power support to the grid.

[0120] When the grid voltage drops, the output phase angle of the reactive power synchronization loop is calculated as follows:

[0121] Assume a three-phase voltage drop occurs in the power grid, and the voltage drop coefficient is denoted as k. drop At this time, the actual voltage of the power grid becomes k. drop U ref Then the inverter's output reactive power command value is:

[0122]

[0123] Since the integral element in the reactive power synchronization loop can accurately track the inverter's output reactive power command value, the difference between the acquired grid voltage phase and the inverter output current phase can be calculated using the following formula:

[0124]

[0125] Because the inverter output current is determined by θ QSC The dominant Park transformation and vector current control determine that the inverter output current phase satisfies in, The initial phase of the inverter output current is determined by the ratio between the dq-axis current command values, satisfying the following relationship:

[0126]

[0127] When the grid voltage drops, the output phase angle of the reactive power synchronization loop is:

[0128]

[0129] In the formula, the grid voltage phase It is represented as ωt.

[0130] Due to the introduction of the grid voltage sag factor k drop At this point, the output phase angle of the reactive power synchronization loop will further lag behind the grid voltage, thereby increasing the phase difference between the grid voltage and the inverter output current. According to equation (7), the phase difference This, to a certain extent, compensates for the reduction in inverter output reactive power caused by grid voltage dips, thereby maintaining the inverter output reactive power at the level before the grid voltage dip and providing reactive power support to the grid.

[0131] In fact, during frequency drops, the actual grid voltage U and the inverter output current amplitude I remain unchanged, therefore the inverter's rated capacity S remains unchanged. n The value is constant. In this case, in order to increase the reactive power output of the inverter, the active power it sends out needs to be reduced. Therefore, the active and rapid reactive power support of the inverter based on the reactive power synchronization loop will not bring the risk of device overcurrent.

[0132] When the grid voltage drops below a set threshold, the reactive power synchronization coefficient in the reactive power synchronization loop output phase angle model is increased, thereby adjusting the reactive power synchronization loop output phase angle so that the inverter outputs reactive power in response to the corresponding command value.

[0133] For the reactive power synchronization loop output phase angle model, the key control parameter is the reactive power synchronization coefficient k. qA larger power synchronization coefficient results in a larger bandwidth of the reactive power synchronization loop, leading to a faster transient response speed. This allows the inverter to track the corresponding command value more quickly with its output reactive power. However, an increase in the reactive power synchronization coefficient can negatively impact the stable operation of the inverter under weak grid conditions. When the impedance curve of a power synchronization inverter at 50Hz power frequency exhibits a reverse spike, it is highly likely to intersect with the grid impedance curve, causing resonance.

[0134] Therefore, under normal operating conditions, a relatively small reactive power synchronization coefficient k is usually selected. q To meet the requirements of inverter stability in weak grid conditions. However, when grid voltage drops occur, in order for the inverter to quickly provide reactive power support to the grid, it is desirable for the transient response speed of the reactive power synchronization loop to be faster, so that the inverter's reactive power output can reach steady state more quickly. At this time, a smaller reactive power synchronization coefficient k... q The requirements are difficult to meet.

[0135] To address this issue, this invention proposes a real-time adjustment method for the reactive power synchronization coefficient based on grid voltage dip detection. When no grid voltage dip occurs, the reactive power synchronization coefficient k... q The reactive power synchronization coefficient k is maintained at a low level, ranging from [0.01, 200], to ensure the safe and stable operation of the power synchronization inverter. If the grid voltage is detected to drop below 0.9 pu, the reactive power synchronization coefficient k is increased. q The value range is [500, 4000], which improves the transient response speed of the reactive power synchronization loop, so that the inverter outputs reactive power to track the command value at a faster speed, and realizes the active and fast support of the inverter based on reactive power synchronization control.

[0136] Depending on the different values ​​of the reactive power synchronization coefficient, the primary voltage regulation coefficient satisfies the following relationship:

[0137] D=α·D0

[0138] In the formula, when the grid voltage drop coefficient is not less than the set threshold, the value of α is 1; when the grid voltage drop coefficient is less than the set threshold, the value of α is 0.08% of the reactive power synchronization coefficient; D0 is the initial value of the primary voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified by the standard, the value of D0 is 0; when the grid frequency deviation exceeds the allowable deviation range specified by the standard, D0 is the base value of the reactive power droop control coefficient.

[0139] This invention combines a reactive power synchronization loop with real-time adjustment of the reactive power synchronization coefficient, thereby enabling the inverter based on reactive power synchronization control to actively and quickly support the grid voltage and provide active and rapid reactive power support during grid voltage drops.

[0140] Existing power synchronous inverter control strategies only achieve power transmission under steady-state conditions. When voltage dips occur in the grid, they cannot quickly provide reactive power support to the system. In other words, the output power of the power synchronous inverter cannot respond quickly and accurately to changes in grid voltage status, lacking the ability to actively provide reactive power support to the grid. The inverter control system presented in this invention can achieve active and rapid reactive power support simply through a reactive power synchronization loop and a grid voltage dip detection element, thereby improving operational performance during grid fluctuations.

[0141] This invention utilizes the inherent characteristics of the reactive power synchronization loop, superimposed with a voltage drop detection element, to achieve rapid adjustment of the inverter's output reactive power, providing a basis for the inverter to actively and quickly support the grid's reactive power. This invention offers a novel design and application approach for an inverter-based grid voltage active support control system based on reactive power synchronization control. This solution has the following advantages:

[0142] By utilizing the inherent characteristics and output of the reactive power synchronization loop, accurate tracking of the inverter's output reactive power command value can be achieved without the need for additional components, thus enabling active support during grid voltage dips.

[0143] Based on the active support characteristics of reactive power synchronization loop, a real-time adjustment system for reactive power synchronization coefficient is proposed, which couples the grid voltage state with key control parameters, namely reactive power synchronization coefficient, thereby achieving active and rapid reactive power support when grid voltage drops.

[0144] This invention also proposes an inverter-supported grid voltage control system for reactive power synchronous control, comprising: a model module, a data acquisition module, and a control module;

[0145] The model module is used to establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model.

[0146] The data acquisition module is used to collect the inverter's output reactive power deviation, inverter's output current command value, grid voltage drop coefficient, and grid voltage phase when the grid voltage drops.

[0147] The control module is used to correct the inverter's output reactive power deviation using a primary voltage regulation model, obtain the grid frequency deviation using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation, and output the reactive power synchronization phase angle using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. It determines the inverter's output current phase based on the reactive power synchronization phase angle and the inverter's output current command value; determines the inverter's output reactive power command value based on the grid voltage drop factor and the difference between the grid voltage phase and the inverter's output current phase; and controls the inverter based on the output reactive power command value.

[0148] Preferably, the model module includes: a primary voltage regulation unit, a reactive power synchronization unit, and a phase angle unit; wherein,

[0149] The primary voltage regulation unit takes the grid frequency deviation output by the reactive power synchronization model as input, obtains the reactive power compensation caused by the grid voltage drop based on the primary voltage regulation coefficient and the grid frequency deviation, and uses the reactive power compensation to correct the output reactive power deviation of the inverter.

[0150] After a voltage regulation unit correction, the reactive power synchronization unit takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation.

[0151] The phase angle unit outputs the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

[0152] Preferably, the model module further includes: a grid voltage sag coefficient adjustment unit and a primary voltage regulation coefficient adjustment unit; wherein,

[0153] The grid voltage sag coefficient adjustment unit is used to set the reactive power synchronization coefficient to a value range of [0.01, 200] when the grid voltage sag coefficient is not less than a set threshold, and the reactive power synchronization coefficient to a value range of [500, 4000] when the grid voltage sag coefficient is less than a set threshold. The set threshold value range is not less than 0.9. The grid voltage sag coefficient is the ratio of the actual grid voltage value to the commanded value.

[0154] The primary voltage regulation coefficient adjustment unit is used to calculate the primary voltage regulation coefficient according to the different values ​​of the reactive power synchronization coefficient, using the following formula:

[0155] D=α·D0

[0156] In the formula, when the grid voltage drop coefficient is not less than the set threshold, the value of α is 1; when the grid voltage drop coefficient is less than the set threshold, the value of α is 0.08% of the reactive power synchronization coefficient; D0 is the initial value of the primary voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified by the standard, the value of D0 is 0; when the grid frequency deviation exceeds the allowable deviation range specified by the standard, D0 is the base value of the reactive power droop control coefficient.

[0157] Preferably, the control module includes: an inverter output current phase calculation unit and an inverter output reactive power command value calculation unit; wherein,

[0158] The inverter output current phase calculation unit is used to calculate the initial phase of the inverter output current based on the inverter output current command value, calculate the difference between the reactive power synchronization phase angle and the initial phase of the inverter output current, and obtain the phase of the inverter output current.

[0159] The inverter output reactive power command value calculation unit is used to calculate the difference between the collected grid voltage phase and the inverter output current phase, and determines the inverter output reactive power command value according to the following relationship:

[0160]

[0161] In the formula, k drop U is the grid voltage sag factor, which is the ratio of the actual grid voltage value to the given value. ref This is the inverter output voltage command value.

[0162] When the grid voltage drops to 0.6 pu, the theoretical calculation results and simulation results of the reactive power synchronization loop output phase are as follows: Figure 3 As shown. At this time, in the control system, the initial setpoint i of the inverter output d-axis current. dini The q-axis current setpoint is 50A. qref The inverter rated capacity is -30A, S. n For 30kVA, ω ref The power synchronization coefficient is 100π, and the power synchronization coefficient is k. q The value is 200. If the grid voltage is detected to drop to 0.9 pu, the reactive power synchronization coefficient real-time adjustment system will adjust the power synchronization coefficient k. q Up to 500. When a grid voltage dip occurs, substituting the above simulation parameters, the calculated value is ωt - 0.156π, and the theoretical analysis results are plotted as follows. Figure 3 The solid sawtooth wave shown in the figure basically matches the simulation results (dashed sawtooth wave), verifying the correctness of the theoretical analysis of the reactive power synchronization loop output phase under grid voltage dips. Furthermore, from... Figure 2It can be seen that when the grid voltage drops, the reactive power synchronization loop will spontaneously adjust its output phase so that the locked phase lags behind the grid voltage, thereby increasing the phase difference between voltage and current. Figure 4 Simulation results of inverter output active and reactive power under grid voltage dips in a real-time adjustment system without reactive power synchronization coefficient. Figure 4 It can be seen that although the inverter can restore its output reactive power to the level before the grid voltage drop, the overall response speed is slow, requiring approximately 2.5 cycles to achieve power recovery. Figure 5 These are simulation results of the inverter's output active and reactive power under grid voltage dips after adopting a response speed optimized control strategy. Figure 5 As can be seen, the inverter's output reactive power can be restored to the level before the grid voltage drop in just 1 / 4 cycle, demonstrating a fast response speed and thus providing rapid and proactive reactive power support to the grid. Simulations verify the correctness of the theory, proving that the inverter's proactive and rapid grid voltage support control method based on reactive power synchronization control proposed in this invention can achieve rapid power support for grid voltage drops.

[0163] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0164] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0165] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0166] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via 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., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for inverter-supported grid voltage control with reactive power synchronous control, characterized in that, include: Establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model; When the grid voltage drops, the inverter's output reactive power deviation, the inverter's output current command value, the grid voltage drop coefficient, and the grid voltage phase are collected. The inverter's output reactive power deviation is corrected using a primary voltage regulation model. The grid frequency deviation is obtained using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation. The reactive power synchronization phase angle is output using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. The reactive power synchronization phase angle model satisfies the following relationship: In the formula, The reactive power synchronization phase angle, For the power grid frequency, For frequency domain operators, The given value for the power grid frequency, This is the output reactive power command value of the inverter. This represents the actual output reactive power of the inverter. The rated capacity of the inverter, This is the reactive power synchronization coefficient. This is the primary voltage regulation coefficient; The output current phase of the inverter is determined based on the reactive power synchronization phase angle and the output current command value of the inverter; the output reactive power command value of the inverter is determined based on the grid voltage drop factor and the difference between the grid voltage phase and the output current phase of the inverter; the inverter is controlled based on the output reactive power command value of the inverter.

2. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 1, characterized in that, The primary voltage regulation model takes the grid frequency deviation output by the reactive power synchronization model as input. Based on the primary voltage regulation coefficient and the grid frequency deviation, the reactive power compensation caused by the grid voltage drop is obtained. The reactive power compensation is then used to correct the output reactive power deviation of the inverter. After a voltage regulation model correction, the reactive power synchronization model takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation. The phase angle model is used to output the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

3. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 1, characterized in that, The correction value of the inverter's output reactive power deviation, obtained after one voltage regulation model correction, satisfies the following relationship: In the formula, This is the correction value for the output reactive power deviation of the inverter. This is the output reactive power command value of the inverter. This represents the actual output reactive power of the inverter. This is the primary voltage regulation coefficient. This refers to the power grid frequency deviation. When the grid voltage does not drop, the difference between the inverter's output reactive power command value and the actual value is the inverter's output reactive power deviation. .

4. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 3, characterized in that, The power grid frequency deviation satisfies the following relationship: In the formula, This is the reactive power synchronization coefficient. This refers to the rated capacity of the inverter.

5. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 4, characterized in that, The reactive power synchronization phase angle satisfies the following relationship: In the formula, The reactive power synchronization phase angle, The given value for the power grid frequency, This is a frequency domain operator.

6. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 4, characterized in that, The grid voltage sag factor is the ratio of the actual grid voltage value to the commanded value; When the grid voltage drop factor is not less than a set threshold, the reactive power synchronization factor can be categorized into the following ranges: ; When the grid voltage sag factor is less than a set threshold, the reactive power synchronization factor can take values ​​ranging from: ; The threshold value is set to be no less than 0.

9.

7. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 6, characterized in that, Depending on the different values ​​of the reactive power synchronization coefficient, the primary voltage regulation coefficient satisfies the following relationship: In the formula, when the grid voltage drop coefficient is not less than the set threshold, The value is 1, when the grid voltage drop coefficient is less than the set threshold. The value is taken as 0.08% of the reactive power synchronization coefficient; This is the initial value of the voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified in the standard, The value is 0 when the power grid frequency deviation exceeds the allowable deviation range specified in the standard. This is the base value for the reactive power droop control coefficient.

8. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 1, characterized in that, The inverter output current phase is determined based on the reactive power synchronization phase angle and the inverter output current command value, including: Based on the inverter output current command value, the initial phase of the inverter output current is determined using the following formula: In the formula, , These represent the d-axis and q-axis components of the inverter's output current command, respectively. This represents the initial phase of the inverter output current. This refers to the peak value of the phase current in the inverter output current command. The phase of the inverter output current is obtained by calculating the difference between the reactive power synchronization phase angle and the initial phase of the inverter output current using the following formula: In the formula, The phase of the inverter output current. This is the reactive power synchronization phase angle.

9. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 8, characterized in that, Based on the grid voltage sag coefficient and the difference between the collected grid voltage phase and the inverter output current phase, the command value for the inverter output reactive power is determined, including: The difference between the acquired grid voltage phase and the inverter output current phase is calculated using the following formula: ； In the formula, This is the difference between the phase of the collected grid voltage and the phase of the inverter output current. The phase of the grid voltage; The inverter's output reactive power command value is determined by the following relationship: In the formula, This refers to the grid voltage sag factor, which is the ratio of the actual grid voltage value to the commanded value. This is the inverter output voltage command value.

10. The inverter-supported grid voltage control method for reactive power synchronous control according to claim 9, characterized in that, The reactive power command value output by the inverter satisfies the following relationship: In the formula, This is the inverter output voltage command value. This represents the q-axis component of the inverter's output current command.

11. A reactive power synchronous control inverter-supported grid voltage control system, characterized in that, include: Model module, acquisition module, and control module; The model module is used to establish a reactive power synchronization phase angle model, including a primary voltage regulation model, a reactive power synchronization model, and a phase angle model. The data acquisition module is used to collect the inverter's output reactive power deviation, inverter's output current command value, grid voltage drop coefficient, and grid voltage phase when the grid voltage drops. The control module is used to correct the inverter's output reactive power deviation using a primary voltage regulation model, obtain the grid frequency deviation using a reactive power synchronization model based on the corrected value of the inverter's output reactive power deviation, and output the reactive power synchronization phase angle using a phase angle model based on the grid frequency deviation and the grid frequency setpoint. The reactive power synchronization phase angle model satisfies the following relationship: In the formula, The reactive power synchronization phase angle, For the power grid frequency, For frequency domain operators, The given value for the power grid frequency, This is the output reactive power command value of the inverter. This represents the actual output reactive power of the inverter. The rated capacity of the inverter, This is the reactive power synchronization coefficient. This is the primary voltage regulation coefficient; The output current phase of the inverter is determined based on the reactive power synchronization phase angle and the output current command value of the inverter; the output reactive power command value of the inverter is determined based on the grid voltage drop factor and the difference between the grid voltage phase and the output current phase of the inverter; the inverter is controlled based on the output reactive power command value of the inverter.

12. The inverter-supported grid voltage control system for reactive power synchronous control according to claim 11, characterized in that, The model module includes: a primary voltage regulation unit, a reactive power synchronization unit, and a phase angle unit; among which, The primary voltage regulation unit takes the grid frequency deviation output by the reactive power synchronization model as input, obtains the reactive power compensation caused by the grid voltage drop based on the primary voltage regulation coefficient and the grid frequency deviation, and uses the reactive power compensation to correct the output reactive power deviation of the inverter. After a voltage regulation unit correction, the reactive power synchronization unit takes the correction value of the inverter's output reactive power deviation as input, and obtains the grid frequency deviation based on the reactive power synchronization coefficient and the correction value of the inverter's output reactive power deviation. The phase angle unit outputs the reactive power synchronization phase angle based on the grid frequency deviation and the grid frequency setpoint.

13. The inverter-supported grid voltage control system for reactive power synchronous control according to claim 11, characterized in that, The model module also includes: a grid voltage sag coefficient adjustment unit and a primary voltage regulation coefficient adjustment unit; among which, The grid voltage sag coefficient adjustment unit is used to adjust the reactive power synchronization coefficient within a range when the grid voltage sag coefficient is not less than a set threshold. When the grid voltage drop factor is less than the set threshold, the reactive power synchronization factor can take values ​​ranging from [value missing]. The threshold value is set to be no less than 0.9, and the grid voltage drop coefficient is the ratio of the actual grid voltage value to the commanded value. The primary voltage regulation coefficient adjustment unit is used to calculate the primary voltage regulation coefficient according to the different values ​​of the reactive power synchronization coefficient, using the following formula: In the formula, when the grid voltage drop coefficient is not less than the set threshold, The value is 1, when the grid voltage drop coefficient is less than the set threshold. The value is taken as 0.08% of the reactive power synchronization coefficient; This is the initial value of the voltage regulation coefficient. When the grid frequency deviation is within the allowable deviation range specified in the standard, The value is 0 when the power grid frequency deviation exceeds the allowable deviation range specified in the standard. This is the base value for the reactive power droop control coefficient.

14. The inverter-supported grid voltage control system for reactive power synchronous control according to claim 11, characterized in that, The control module includes: an inverter output current phase calculation unit and an inverter output reactive power command value calculation unit; wherein, The inverter output current phase calculation unit is used to calculate the initial phase of the inverter output current based on the inverter output current command value, calculate the difference between the reactive power synchronization phase angle and the initial phase of the inverter output current, and obtain the phase of the inverter output current. The inverter output reactive power command value calculation unit is used to calculate the difference between the collected grid voltage phase and the inverter output current phase, and determines the inverter output reactive power command value according to the following relationship: In the formula, This refers to the grid voltage sag factor, which is the ratio of the actual grid voltage value to the given value. This is the inverter output voltage command value. This is the difference between the phase of the collected grid voltage and the phase of the inverter output current.

15. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-10.

16. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-10.

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