Fault-tolerant control method, system and equipment for active power filter, medium and product

Abstract

The invention relates to the technical field of power filters, and discloses a fault-tolerant control method, system, equipment, medium and product for an active power filter, and the method comprises the steps: building an observer of a fault sensor through the type of the fault sensor after the type of the fault sensor of the active power filter is determined, and outputting an observation value through the observer; and fault-tolerant control is carried out on the fault sensor through the observed value, so that the fault-tolerant control is carried out on the power grid voltage sensor, the inverter output current sensor and the direct current side voltage sensor without changing a modulation strategy, and the accuracy of fault-tolerant control of the active power filter is improved; and stable operation and reliability of the system of the active power filter are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power filters, and in particular to a fault-tolerant control method, system, equipment, medium and product of an active power filter. Background Art

[0002] Parallel active power filters are widely used in the field of harmonic control due to their good real-time performance and safety. However, due to factors such as equipment aging and mechanical vibration, the current and voltage sensors in the system are prone to failure. At this time, there is a large deviation between the measured value and the actual value, and the controller will not be able to work normally. If the inverter has an overcurrent, other components in the system will be damaged due to overcurrent or overvoltage, and may even affect the load-end equipment, causing more serious consequences. Fault-tolerant control refers to the use of algorithms to enable the system to continue to operate under the original performance indicators, or to continue to operate when the performance indicators are reduced but no harm is caused. In order to avoid sensor failures affecting system operation and further expansion of failures, it is necessary to perform fault-tolerant control on sensor failures of active power filters.

[0003] At present, the sensor fault-tolerant control of the active power filter only considers the case of no AC voltage sensor, which makes the accuracy of the sensor fault-tolerant control of the active power filter poor and the reliability low. Summary of the invention

[0004] In view of this, the present invention provides an active power filter fault-tolerant control method, system, device, medium and product, which solves the technical problems of poor accuracy and low reliability of sensor fault-tolerant control of the active power filter.

[0005] A first aspect of the present invention provides a fault-tolerant control method for an active power filter, comprising:

[0006] In response to a fault-tolerant control request of a fault sensor of the active power filter, determining the type of the fault sensor; wherein the type of the fault sensor includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor;

[0007] Constructing an observer of the fault sensor according to the fault sensor type;

[0008] An observation value is outputted by the observer, and fault-tolerant control is performed on the faulty sensor by using the observation value.

[0009] Preferably, when the fault sensor type is a grid voltage sensor;

[0010] The step of constructing an observer for the fault sensor according to the fault sensor type comprises:

[0011] Constructing a mathematical model of the active power filter according to the topological structure of the active power filter;

[0012] Converting the mathematical model of the active power filter into a mathematical model in a two-phase stationary coordinate system;

[0013] An orthogonal filter based on a second-order generalized integrator performs an integration operation on the differential terms in the mathematical model of the active power filter in a two-phase stationary coordinate system to obtain a mathematical model of the observer of the grid voltage sensor, and the mathematical model of the observer of the grid voltage sensor outputs the observed value including the grid voltage.

[0014] Preferably, when the fault sensor type is an inverter output current sensor;

[0015] The step of constructing an observer for the fault sensor according to the fault sensor type comprises:

[0016] Constructing a mathematical model of the active power filter according to the topological structure of the active power filter;

[0017] Updating the mathematical model of the active power filter according to the stray resistance at the output end of the inverter;

[0018] Based on the updated mathematical model of the active power filter, selecting the inverter output current as the state variable of the active power filter, and determining the state equation of the active power filter;

[0019] The state equation is recursively updated based on an extended Kalman filter algorithm to obtain a mathematical model of an observer of the inverter output current sensor.

[0020] Preferably, outputting the observation value through the observer and performing fault-tolerant control on the faulty sensor through the observation value comprises:

[0021] Outputting an observation value through a mathematical model of an observer of the inverter output current sensor; wherein the observation value is a state variable of an active power filter optimized by the observer;

[0022] Using current sensors on other non-fault phases at the output end of the inverter to obtain current observation values ​​of the non-fault phases;

[0023] Performing coordinate transformation on the current observation value of the non-fault phase to obtain the α-axis current component in the α-β coordinate system;

[0024] Using the α-axis current component to update and correct the observed value to obtain an optimal observed value;

[0025] The faulty sensor is controlled to be fault-tolerant by using the optimal observation value.

[0026] Preferably, when the fault sensor type is a DC side voltage sensor;

[0027] The step of constructing an observer for the fault sensor according to the fault sensor type comprises:

[0028] Constructing a mathematical model of the active power filter according to the topological structure of the active power filter;

[0029] Converting the mathematical model of the active power filter into a mathematical model in a synchronous rotating coordinate system;

[0030] Based on the mathematical model of the active power filter in the synchronous rotating coordinate system, the DC side voltage of the DC side voltage sensor is selected as the state variable of the active power filter to determine the state equation of the active power filter;

[0031] The state equation is recursively updated based on an extended Kalman filter algorithm to obtain a mathematical model of an observer of the DC side voltage sensor.

[0032] Preferably, outputting the observation value through the observer and performing fault-tolerant control on the faulty sensor through the observation value comprises:

[0033] Outputting an observation value through a mathematical model of an observer of the DC side voltage sensor; wherein the observation value is a state variable of an active power filter optimized by the observer;

[0034] Using current sensors on other non-fault phases at the output end of the inverter to obtain current observation values ​​of the non-fault phases;

[0035] Performing coordinate transformation on the current observation value of the non-fault phase to obtain a q-axis current component and a d-axis current component in a qd coordinate system;

[0036] Using the q-axis current component and the d-axis current component to update and correct the observed value to obtain an optimal observed value;

[0037] The faulty sensor is controlled to be fault-tolerant by using the optimal observation value.

[0038] In a second aspect, the present invention further provides an active power filter fault-tolerant control system, comprising:

[0039] A fault type determination module, configured to determine the type of the fault sensor in response to a fault-tolerant control request of the fault sensor of the active power filter; wherein the fault sensor type includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor;

[0040] An observer construction module, used to construct an observer of the fault sensor according to the type of the fault sensor;

[0041] The fault-tolerant control module is used to output the observation value through the observer and perform fault-tolerant control on the faulty sensor through the observation value.

[0042] In a third aspect, the present invention further provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the active power filter fault-tolerant control method as described in the first aspect.

[0043] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed, the steps of the active power filter fault-tolerant control method as described in the first aspect are implemented.

[0044] In a fifth aspect, the present invention further provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the active power filter fault-tolerant control method as described in the first aspect.

[0045] It can be seen from the above technical solutions that the present invention, after determining the type of the fault sensor of the active power filter, uses the fault sensor type to construct an observer of the fault sensor, outputs an observation value through the observer, and performs fault-tolerant control on the fault sensor through the observation value, thereby performing fault-tolerant control on the grid voltage sensor, the inverter output current sensor, and the DC side voltage sensor without changing the modulation strategy, thereby improving the accuracy of the fault-tolerant control of the active power filter and ensuring the stable operation and reliability of the active power filter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 An application environment of an active power filter fault-tolerant control method provided by an embodiment of the present invention;

[0048] Figure 2 A process of a fault-tolerant control method for an active power filter provided by an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of the topological structure of a parallel active power filter provided in an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of the structure of a second-order generalized integrator provided by an embodiment of the present invention;

[0051] Figure 5 A control block diagram of an observer for a power grid voltage sensor provided by an embodiment of the present invention;

[0052] Figure 6 A control block diagram of a phase-locked operation of an observer of a power grid voltage sensor provided by an embodiment of the present invention;

[0053] Figure 7 A control block diagram of an observer for an inverter output current sensor provided by an embodiment of the present invention;

[0054] Figure 8 A control block diagram of an observer for a DC side voltage sensor provided by an embodiment of the present invention;

[0055] Fig. 9 A schematic structural diagram of an active power filter fault-tolerant control system provided by an embodiment of the present invention;

[0056] Fig.10 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The active power filter fault-tolerant control method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown. Among them, the terminal 101 communicates with the server 102 through the network. The data storage system can store data that the server 102 needs to process. The data storage system can be integrated on the server 102, or it can be placed on the cloud or other network servers. The terminal 101 or the server 102 responds to the fault-tolerant control request of the fault sensor of the active power filter to determine the type of the fault sensor; wherein the fault sensor type includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor; an observer of the fault sensor is constructed according to the type of the fault sensor; the observation value is output through the observer, and the fault sensor is fault-tolerantly controlled through the observation value.

[0059] The terminal 101 may be, but is not limited to, various personal computers, laptop computers, smart phones, tablet computers, and the like.

[0060] The server 102 may be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0061] like Figure 2 As shown, the embodiment of the present application provides a fault-tolerant control method for an active power filter, and the method is applied to Figure 1 The terminal 101 or the server 102 in the example is used to illustrate, and the steps include the following steps S1 to S3. Among them:

[0062] Step S1, in response to a fault-tolerant control request of a fault sensor of an active power filter, determining the type of the fault sensor; wherein the fault sensor type includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor.

[0063] The grid voltage sensor is a sensor that provides grid voltage information to the active power filter (APF). Its failure may cause the active power filter to be unable to accurately obtain grid voltage information, thus affecting the filtering effect. The inverter output current sensor is used to monitor the current output by the inverter. Its failure may cause the active power filter to be unable to accurately obtain the current information output by the inverter, thereby affecting the accuracy of harmonic compensation. The DC side voltage sensor is used to monitor the voltage on the DC side of the active power filter. Its failure may cause the active power filter to be unable to accurately obtain the DC side voltage information, thereby affecting the voltage stability of the DC side capacitor and the normal operation of the filter. After determining the type of faulty sensor, the system can construct a corresponding observer for fault-tolerant control.

[0064] It can be understood that, for determining the type of the faulty sensor, the fault-tolerant control request of the faulty sensor may include the type of the faulty sensor, thereby making it easy to obtain the type of the faulty sensor.

[0065] Step S2: construct an observer for the faulty sensor according to the type of the faulty sensor.

[0066] Among them, the observer of the fault sensor is a specific mathematical model designed based on the type of fault sensor, which is used to simulate and predict the output of the fault sensor. For different types of fault sensors, the construction method and algorithm of the observer will also be different. For example, for a grid voltage sensor fault, the observer can use other electrical parameters and topology of the active power filter to infer the grid voltage; for an inverter output current sensor fault or a DC side voltage sensor fault, the observer can reconstruct the output current or DC side voltage based on the inverter control strategy and the electrical characteristics of the output end.

[0067] Step S3: outputting observation values ​​through the observer, and performing fault-tolerant control on the faulty sensor through the observation values.

[0068] It should be noted that, in the embodiment of the present application, after determining the fault sensor type of the active power filter, an observer of the fault sensor is constructed using the fault sensor type, the observation value is output by the observer, and the fault sensor is fault-tolerantly controlled through the observation value. Thus, there is no need to change the modulation strategy, and the grid voltage sensor, the inverter output current sensor, and the DC side voltage sensor are fault-tolerantly controlled, thereby improving the accuracy of the fault-tolerant control of the active power filter and ensuring the stable operation and reliability of the active power filter system.

[0069] In some embodiments, when the fault sensor type is a grid voltage sensor;

[0070] In step S2, an observer of the faulty sensor is constructed according to the type of the faulty sensor, including:

[0071] Step S201: construct a mathematical model of the active power filter according to the topological structure of the active power filter.

[0072] Among them, the topology of the parallel active power filter is as follows: Figure 3 As shown, where u sa 、u sb 、u sc is the three-phase voltage on the grid side, u dc is the DC side voltage, i ia 、i ib 、i ic is the three-phase output current of the inverter, u ia 、u ib 、u ic is the three-phase output voltage of the inverter. 1 -T 6 is the switch tube of each phase bridge arm, L a, L b , L c are the output filter inductors of the a-phase, b-phase and c-phase bridge arms of the inverter, and C is the DC-side voltage stabilizing capacitor. At the same time, it is assumed that all switching devices in the active power filter are ideal devices, and line losses are not taken into account. The mathematical model of the parallel active power filter topology structure is converted to the synchronous rotating coordinate system to obtain the mathematical model:

[0073]

[0074] In the formula, , are the complex power components on the d-axis and the q-axis respectively, , are the current component on the d-axis and the current component on the q-axis respectively, , are the grid voltage component on the d-axis and the grid voltage component on the q-axis respectively. is the angular frequency, and L is the inverter output filter inductance.

[0075] Step S202: converting the mathematical model of the active power filter into a mathematical model in a two-phase stationary coordinate system.

[0076] Among them, the mathematical model of the active power filter is converted from the three-phase stationary coordinate system to the two-phase stationary coordinate system, and is expressed in matrix form as follows:

[0077]

[0078] In the formula, , are the components of the α-axis and β-axis of the grid voltage in the two-phase stationary coordinate system, , are the components of the α-axis and β-axis of the inverter output current in the two-phase stationary coordinate system, For the moment, , They are respectively the components of the α-axis and β-axis of the inverter output voltage in the two-phase stationary coordinate system.

[0079] Step S203: An orthogonal filter based on a second-order generalized integrator performs an integration operation on the differential terms in the mathematical model of the active power filter in the two-phase stationary coordinate system to obtain a mathematical model of an observer of the grid voltage sensor, wherein the mathematical model of the observer of the grid voltage sensor outputs observation values ​​including the grid voltage.

[0080] It is understandable that there are differential terms in the mathematical model of the source power filter in the two-phase stationary coordinate system. In actual calculations, differential terms are prone to amplify noise and introduce interference. Therefore, in the fault-tolerant control of the grid voltage sensor, it is usually converted into an integral operation, and the phase information of the grid voltage is obtained through the virtual flux method. However, the traditional virtual flux method has problems such as initial value sensitivity and DC bias, and requires complex algorithm optimization.

[0081] Therefore, the embodiment of the present application is based on the orthogonal filter of the second-order generalized integrator to perform integration operation on the differential terms in the mathematical model of the active power filter in the two-phase stationary coordinate system, which can effectively reduce noise interference.

[0082] Among them, the second-order generalized integrator (SOGI) can generate two mutually orthogonal components from an input signal, namely the in-phase component and the quadrature component. These two components have a phase difference of 90 degrees relative to each other. Figure 4 As shown in the figure, the second-order generalized integrator has the characteristic of internal resonance, which can make the input signal have infinite gain at a certain frequency, that is, the output can track the input signal without static error at this frequency point. Using this characteristic, SOGI is often used to separate positive and negative sequence components, and the orthogonal filter it forms can be used as a voltage-controlled oscillator in the phase-locked loop to perform grid phase locking.

[0083] exist Figure 4 In the second-order generalized integrator shown in Figure 1, v represents the input of SOGI, and are two mutually orthogonal output quantities, Ahead of the times The phase is 90°, is the resonant frequency, k is the gain coefficient,

[0084] The transfer function of SOGI can be expressed as:

[0085]

[0086]

[0087] In the formula, , are the first transfer function and the second transfer function respectively, and s is the Laplace operator.

[0088] The amplitude-frequency and phase-frequency characteristics of the SOGI-based orthogonal filter can be obtained from the transfer function:

[0089]

[0090] In the formula, , are the first transfer function value and the second transfer function value respectively.

[0091] in,

[0092]

[0093]

[0094] From the above formula, we can see that Always lagging behind 90°, that is, the two output signals are orthogonal to each other; and when the angular frequency of the input signal is equal to the resonant frequency, that is, the angular frequency When It can track the input signal without static error, and at this time:

[0095]

[0096] In the formula, is the input of SOGI under the Laplace operator s, and are two mutually orthogonal output quantities under the Laplace operator s, is the imaginary unit.

[0097] Right now:

[0098]

[0099] In the formula, , They are two mutually orthogonal outputs at time t.

[0100] It can be seen that in the orthogonal filter based on SOGI, the differential calculation of a signal can be represented by a signal orthogonal to it. Therefore, by integrating the differential terms in the mathematical model of the active power filter in the two-phase stationary coordinate system through the orthogonal filter of the second-order generalized integrator, the noise interference can be effectively reduced, and the differential terms in the mathematical model are replaced by orthogonal signals to form the observer model of the grid voltage sensor, and thus determine the following: Figure 5 The control block diagram of the observer is shown in Figure 1. The observer model of the grid voltage sensor is:

[0101]

[0102] In the formula, and , and are two sets of mutually orthogonal current components, and is the output voltage of the inverter.

[0103] Among them, in the case of a grid voltage sensor failure, the input of the observer is the components of the three-phase output current of the inverter in the two-phase stationary coordinate system and the inverter output voltage, and the output is the components of the grid voltage in the two-phase stationary coordinate system. The components of the grid voltage in the two-phase stationary coordinate system are substituted into the controller of the grid voltage sensor for phase-locked operation to obtain the phase information of the grid voltage, thereby completing the fault-tolerant control of the APF grid voltage sensor failure.

[0104] In the two-phase stationary coordinate system, the phase information (phase angle) of the grid voltage is obtained by using the SOGI-based observer. The phase information (phase angle) replaces the phase-locked angle originally obtained by the grid voltage sensor to complete the fault-tolerant control. The control strategy framework is as follows: Figure 6 shown.

[0105] In some embodiments, when the fault sensor type is an inverter output current sensor;

[0106] Construct the observer of the faulty sensor according to the faulty sensor type, including:

[0107] Step S211: construct a mathematical model of the active power filter according to the topological structure of the active power filter.

[0108] Step S212: updating the mathematical model of the active power filter according to the stray resistance at the output end of the inverter.

[0109] Among them, the influence of the stray resistance R at the inverter output end is considered. The stray resistance R is introduced through the actual physical structure of the inverter output end, such as the line and connector. According to the technical manual of the cable or other conductive material used, the resistance value per unit length of the line at the inverter output end (usually expressed in ohms / kilometer or ohms / foot) can be found, and the total length of the wire between the inverter output end and the load can be determined. The stray resistance R is determined by multiplying the total length of the wire by the resistance value per unit length.

[0110] The mathematical model of the active power filter can be updated by using the stray resistance at the output end of the inverter, and the updated mathematical model of the active power filter is:

[0111]

[0112] Where R is the stray resistance, i id 、i iq are the d-axis component and q-axis component of the inverter output current in the synchronous coordinate system, u id 、uiq are the d-axis component and q-axis component of the inverter output voltage in the synchronous coordinate system, u sd 、u sq are the d-axis component and q-axis component of the grid voltage in the synchronous coordinate system.

[0113] Step S213: Based on the updated mathematical model of the active power filter, select the inverter output current as the state variable of the active power filter, and determine the state equation of the active power filter.

[0114] Among them, the inverter output current in the two-phase rotating coordinate system is selected as the state variable of the active power filter, that is, x=[i id i iq ]; the grid voltage, inverter output voltage and grid voltage phase-locking angle in the two-phase rotating coordinate system are selected as the input variables of the system, that is, u=[u sd u sq u id u iq ]Determine the state equation. The state equation is:

[0115]

[0116] Step S214: recursively update the state equation based on the extended Kalman filter algorithm to obtain a mathematical model of the observer of the inverter output current sensor.

[0117] Among them, the embodiment of the present application uses the extended Kalman filter algorithm to mathematically model the observer of the inverter output current sensor. Through the recursive update method, we can accurately process the state equation to obtain a more accurate mathematical model. On this basis, we further use the extended Kalman filter algorithm to predict the state variables in order to obtain more accurate prediction values.

[0118] Among them, the state equation combined with the extended Kalman filter algorithm can be obtained:

[0119]

[0120] In the formula, is the extended Kalman filter function.

[0121] Among them, the input matrix and output matrix are:

[0122]

[0123]

[0124] Extended Kalman filter function The Jacobian matrix can be obtained by linearization, denoted as F, where the Jacobian matrix F is:

[0125]

[0126] Assume the sampling frequency of the system is T s , the state equation of a nonlinear system can be discretized as:

[0127]

[0128]

[0129] In the formula, , are the state variables at time t and time t-1 respectively, is the grid voltage at time t-1, is the identity matrix, is the angular frequency of the input signal at time t-1, is the output variable at time t, is the output matrix at time t, is the input of SOGI at time t.

[0130] At this time, the state transfer matrix and output matrix are I+FT s and .

[0131] For an actual APF system, its system noise and measurement noise are generally difficult to obtain, so empirical values ​​are usually taken during the algorithm implementation process. The selection principle is to ensure that the algorithm can converge and track the actual value of the system state variable. At the same time, the selection of initial values ​​is also important in the calculation process. Usually, the initial value of the state variable x of the active power filter is 0 is selected as the zero vector, and the corresponding initial value of the covariance matrix P 0 Select a larger number. It is worth noting that the selected initial value may deviate from the actual value.

[0132] However, since the extended Kalman filter algorithm is a recursive update algorithm, the estimated value will be iteratively updated until the optimal estimated value is reached. In this process, the influence of the initial value error on the result can be gradually reduced to zero. 0 Matrix and initial value P 0 They are:

[0133]

[0134]

[0135]

[0136] Substituting the above analytical expression into the core formula of the extended Kalman filter algorithm, it is divided into five steps:

[0137] (1) Calculate the predicted value of the state variable:

[0138]

[0139] In the formula, is the prior state estimate at time t, , are the system matrices at time t, is the predicted value of the state variable at time t-1;

[0140] in, .

[0141] (2) Calculate the covariance matrix prediction value of the state variable:

[0142]

[0143] In the formula, is the prior error covariance matrix at time t, is the error covariance matrix prediction value at time t-1, T is the matrix device, and Q is the process noise covariance matrix.

[0144] (3) Calculate Kalman gain

[0145]

[0146] In the formula, is the Kalman gain at time t, is the observation noise covariance matrix.

[0147] (4) The state variable covariance matrix is ​​updated according to the Kalman gain, which can be simplified as follows:

[0148]

[0149] In the formula, is the predicted value of the error covariance matrix at time t.

[0150] (5) Update the estimated value of the state variable according to the Kalman gain and the measured value to obtain the observed value of the inverter output current, which is:

[0151]

[0152] In the formula, is the estimated value of the state variable, is the measured value, It is a nonlinear observation model that maps the state space to the measurement space.

[0153] By extending the Kalman filter algorithm, the inverter output current can be accurately observed, and the stability and accuracy of the system can be guaranteed even in the case of sensor failure. After obtaining the observed value of the inverter output current, we can substitute it into the APF control strategy to achieve precise control of the APF.

[0154] The embodiment of the present application achieves accurate observation and compensation of the faulty sensor by constructing an observer of the faulty sensor and using the extended Kalman filter algorithm to mathematically model and recursively update the observer, thereby improving the fault tolerance and stability of the system.

[0155] In addition, the embodiment of the present application can also optimize the design of the observer according to actual needs to improve the observation accuracy and the robustness of the system to adapt to different working conditions and needs.

[0156] Specifically, the observation value is output by the observer, and the faulty sensor is controlled by the observation value, including:

[0157] Step S301, outputting an observation value through a mathematical model of an observer of an inverter output current sensor; wherein the observation value is a state variable of an active power filter optimized by the observer;

[0158] Step S302, using current sensors on other non-faulty phases at the output end of the inverter to obtain current observation values ​​of the non-faulty phases;

[0159] Step S303, performing coordinate transformation on the current observation value of the non-fault phase to obtain the α-axis current component in the α-β coordinate system;

[0160] Step S304, using the α-axis current component to update and correct the observed value to obtain the optimal observed value;

[0161] Step S305: Perform fault-tolerant control on the faulty sensor through the optimal observation value.

[0162] It should be noted that, considering the failure of the current sensor installed at the output end of the inverter, in the three-phase three-wire parallel APF, only the information of two phases is needed to calculate the current of the other phase under the condition that the three-phase current is zero. Sensors are installed on the two phases at the output end. Considering the situation where one of them is damaged, an observer is constructed based on a single current sensor using the extended Kalman filter algorithm to complete fault-tolerant control.

[0163] Assuming that the A-phase current sensor of the APF is available after a fault occurs, that is, the A-phase current can be measured. After coordinate transformation, the α-axis current component is transformed to the α-axis through equal amplitude transformation in the α-β coordinate system, and its magnitude and direction remain unchanged. Therefore, when the A-phase current is measurable, the α-axis current component is also measurable.

[0164] The α-axis current component is used as the correction value. After completing the prediction part, the state variable is updated and corrected with the measured value of the α-axis current component to obtain the optimal observation value of the state variable of the active power filter. That is, the update and correction process of the observation value is:

[0165]

[0166] In the formula, Equal to the α-axis current component.

[0167] From this, we can get the principle of fault-tolerant control using the extended Kalman filter algorithm. When one phase current sensor fails and only one phase current sensor is available, the state variables of the APF active power filter can be corrected and updated. The control block diagram is as follows: Figure 7 As shown, under normal operating conditions, the harmonic extraction algorithm is used to obtain the harmonic current in the load current as a reference value, and the reference value is input into the current controller part as a difference between the reference value and the inverter output current feedback value. The controller uses repetitive control and PI control to track the reference current so that the inverter output current is consistent with the reference current, thereby realizing compensation for the harmonic components in the load current.

[0168] In the case of a current sensor failure, it is impossible to obtain an accurate reference current. Therefore, the reference current information is obtained with the help of an observer. At this time, the observer can obtain the optimal feedback current and enter the closed-loop control system, so that the APF can continue to operate in the event of a current sensor failure. The correction amount is introduced into the update correction module. In the fault-tolerant control algorithm for the inverter output current sensor failure, the α-axis current component is used as the correction amount. After the recursive algorithm, the optimal estimate of the state variable of the active power filter is obtained.

[0169] In some embodiments, when the fault sensor type is a DC link voltage sensor;

[0170] Construct the observer of the faulty sensor according to the faulty sensor type, including:

[0171] Step S221, constructing a mathematical model of the active power filter according to the topological structure of the active power filter;

[0172] Step S222, converting the mathematical model of the active power filter into a mathematical model in a synchronous rotating coordinate system;

[0173] In order to observe the DC voltage, when establishing the state equation of APF, it is different from the fault tolerance control of the inverter output current sensor in that the DC voltage u dc According to the mathematical model of APF, the mathematical model of the three-phase stationary coordinate system is converted to the synchronous rotating coordinate system:

[0174]

[0175] In the formula, C is the DC side capacitance, R is the stray resistance; S d , S q is the switching function S a , S b , S c The value after synchronous coordinate transformation.

[0176] Step S223: Based on the mathematical model of the active power filter in the synchronous rotating coordinate system, the DC side voltage of the DC side voltage sensor is selected as the state variable of the active power filter to determine the state equation of the active power filter.

[0177] Among them, the DC side voltage and the inverter output current in the two-phase rotating coordinate system are selected as the state variables of the active power filter, that is, x=[u dc i id i iq ]; select the grid voltage in the two-phase rotating coordinate system and the switching function value of the inverter in the coordinate system as the input variables of the system, that is, u=[u sd u sq S d S q ], the mathematical model of APF is transformed into the form of state space equation, and the state equation of active power filter is determined as:

[0178]

[0179] Step S224: recursively update the state equation based on the extended Kalman filter algorithm to obtain a mathematical model of the observer of the DC side voltage sensor.

[0180] Among them, combined with the extended Kalman filter algorithm, we can know:

[0181]

[0182] Among them, the input matrix and output matrix are:

[0183]

[0184]

[0185] Extended Kalman filter function The Jacobian matrix can be obtained by linearization, denoted as F, where the Jacobian matrix F is:

[0186]

[0187] Assume the sampling frequency of the system is T s , the state equation of a nonlinear system can be discretized as:

[0188]

[0189]

[0190] At this time, the state transfer matrix and output matrix are I+FT s and .

[0191] In order to achieve better results for the observer, after simulation comparison, take the initial value x 0 , P 0 , system noise Q matrix and measurement noise R 0 The matrices are:

[0192]

[0193]

[0194]

[0195]

[0196] Substituting the above analytical expression into the core formula of the extended Kalman filter algorithm, it is divided into five steps:

[0197] Compute the predicted values ​​of the state variables:

[0198]

[0199] In the formula, is the prior state estimate at time t, , are the system matrices at time t, is the predicted value of the state variable at time t-1; .

[0200] (2) Calculate the covariance matrix prediction value of the state variable:

[0201]

[0202] In the formula, is the prior error covariance matrix at time t, is the error covariance matrix prediction value at time t-1, T is the matrix device, and Q is the process noise covariance matrix.

[0203] (3) Calculate Kalman gain

[0204]

[0205] In the formula, is the Kalman gain at time t, is the observation noise covariance matrix.

[0206] (4) The state variable covariance matrix is ​​updated according to the Kalman gain, which can be simplified as follows:

[0207]

[0208] In the formula, is the predicted value of the error covariance matrix at time t.

[0209] (5) Update the estimated value of the state variable according to the Kalman gain and the measured value to obtain the observed value of the inverter output current, which is:

[0210]

[0211] In the formula, is the estimated value of the state variable, is the measured value, It is a nonlinear observation model that maps the state space to the measurement space.

[0212] In the fault-tolerant control for DC voltage sensor failure, the extended Kalman filter algorithm is used to observe the DC voltage. By constructing the mathematical model of APF and converting it to a synchronous rotating coordinate system, we can determine the state equation of APF. On this basis, the state equation is recursively updated using the extended Kalman filter algorithm to obtain the mathematical model of the observer of the DC voltage sensor. This observer can estimate the value of the DC voltage in real time, and can ensure the stability and accuracy of the system even in the case of sensor failure.

[0213] The DC side voltage observation value obtained by the observer can be substituted into the APF control strategy to achieve precise control of the APF.

[0214] At the same time, the design of the observer is optimized according to actual needs to improve the observation accuracy and the robustness of the system. Therefore, in the embodiment of the present application, the observer outputs the observation value, and the fault-tolerant control of the faulty sensor is performed through the observation value, including:

[0215] Step S311, outputting an observation value through the mathematical model of the observer of the DC side voltage sensor; wherein the observation value is a state variable of the active power filter optimized by the observer;

[0216] Step S312, using current sensors on other non-faulty phases at the output end of the inverter to obtain current observation values ​​of the non-faulty phases;

[0217] Step S313, performing coordinate transformation on the current observation value of the non-fault phase to obtain the q-axis current component and the d-axis current component in the qd coordinate system;

[0218] Step S314, using the q-axis current component and the d-axis current component to update and correct the observed value to obtain the optimal observed value;

[0219] Step S315: Perform fault-tolerant control on the faulty sensor through the optimal observation value.

[0220] Among them, the inverter output current in the measurable dq coordinate system can be used as the correction value, that is, y=[i id i iq ] After completing the prediction part, this pair of measurements is used to update and correct the state estimate to obtain the best estimate of the system state variables.

[0221] The updating and correction process of the state variables is expressed as:

[0222]

[0223] In the formula, is equal to the q-axis current component or the d-axis current component. Since the feedback current values ​​of the d and q axes are measurable when only the DC side voltage sensor fails, it can be used as a correction value for recursion to obtain the state variable u dc The best estimate of . From this, we can get the observer based on the extended Kalman filter, and the control block diagram is as follows Figure 8 As shown. sa 、u sb 、u sc It represents the three-phase grid voltage, which is u in the dq coordinate system after coordinate transformation. sd 、u sq ; S a , S b , S c It represents the switching function of the inverter, which is converted to the two-phase rotating coordinate system after coordinate transformation as S d , S q ; θ is the grid voltage phase-locking angle. After the above variables are passed through the prediction and estimation module, the DC side voltage prediction value u of the active power filter is obtained. dcP , predicted value of current component i on the d-axisidP , the predicted value of the current component on the q axis i iqP At this time, in order to obtain the optimal estimate of the system state variables, a measurable feedback current i is introduced id 、i iq As the correction amount, the optimal estimate of the system is obtained after the update correction link.

[0224] like Figure 8 As shown, under normal operating conditions, the normal operation of the APF relies on a stable DC side capacitor voltage as a basic support. To ensure that the APF can generate accurate compensation current in real time based on changes in the reference current, the DC side voltage value must be higher than the peak value of the grid line voltage. The core principle of DC side capacitor voltage tracking control is to achieve energy balance by adjusting the active power absorbed or released by the main circuit from the grid, so that the actual value of the DC voltage accurately tracks its reference value. In an embodiment of the present application, a PI control strategy is adopted, the core of which is to calculate u through a PI controller based on the difference between the reference value and the actual value of the DC voltage. dc The result is superimposed on the harmonic detection algorithm based on synchronous coordinate transformation, acting on the d-axis representing the active current to generate the corresponding reference current value. This process makes the compensation current output by the APF contain the fundamental active component, effectively completes the energy exchange between the DC side and the grid side, and realizes the precise adjustment of the actual value to the reference value.

[0225] When the DC voltage sensor fails, the accurate DC voltage value cannot be obtained through the sensor. Therefore, the observer is used to obtain the optimal DC voltage information and introduce it into the closed-loop control system to ensure that the APF can continue to operate in the case of a DC voltage sensor failure.

[0226] It should be noted that the embodiment of the present application applies the observer-based fault-tolerant control technology to the sensor fault processing of the active power filter, and constructs corresponding observers for grid voltage sensor failure, output current sensor failure and DC side voltage sensor failure to achieve effective fault-tolerant control, thereby improving the reliability of the system's fault-tolerant control.

[0227] Based on the same inventive concept, an embodiment of the present application further provides an active power filter fault-tolerant control system for implementing the above-mentioned active power filter fault-tolerant control method.

[0228] The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more active power filter fault-tolerant control system embodiments provided below can refer to the limitations on the active power filter fault-tolerant control method in the above text, and will not be repeated here.

[0229] like Fig. 9As shown, the embodiment of the present application provides an active power filter fault-tolerant control system, comprising:

[0230] The fault type determination module 100 is used to determine the fault sensor type in response to the fault-tolerant control request of the fault sensor of the active power filter; wherein the fault sensor type includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor;

[0231] An observer construction module 200 is used to construct an observer of a faulty sensor according to the type of the faulty sensor;

[0232] The fault-tolerant control module 300 is used to output observation values ​​through an observer and perform fault-tolerant control on the faulty sensor through the observation values.

[0233] like Fig.10 As shown, an embodiment of the present application provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, and when the computer program is executed by the processor 30, the processor 30 executes the steps of the active power filter fault-tolerant control method in the above embodiment.

[0234] An embodiment of the present application provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed, the steps of the active power filter fault-tolerant control method in the above embodiment are implemented.

[0235] An embodiment of the present application provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the active power filter fault-tolerant control method in the above embodiment.

[0236] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, electronic devices, computer storage media and computer program products can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0237] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0238] In several embodiments provided by the present invention, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and a part of a module, a program segment or a code includes one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0239] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media, and computer program products and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0240] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0241] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0242] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for executing all or part of the steps of the method described in each embodiment of the present invention through a computer device (which can be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk and other media that can store program codes.

[0243] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault-tolerant control method for an active power filter, characterized in that: include: In response to a fault-tolerant control request of a fault sensor of the active power filter, determining the type of the fault sensor; wherein the type of the fault sensor includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor; Constructing an observer of the fault sensor according to the fault sensor type; An observation value is outputted by the observer, and fault-tolerant control is performed on the faulty sensor by using the observation value.

2. The active power filter fault-tolerant control method according to claim 1, characterized in that: When the fault sensor type is a grid voltage sensor; The step of constructing an observer for the fault sensor according to the fault sensor type comprises: Constructing a mathematical model of the active power filter according to the topological structure of the active power filter; Converting the mathematical model of the active power filter into a mathematical model in a two-phase stationary coordinate system; An orthogonal filter based on a second-order generalized integrator performs an integration operation on the differential terms in the mathematical model of the active power filter in a two-phase stationary coordinate system to obtain a mathematical model of the observer of the grid voltage sensor, and the mathematical model of the observer of the grid voltage sensor outputs the observed value including the grid voltage.

3. The active power filter fault-tolerant control method according to claim 1, characterized in that: When the fault sensor type is an inverter output current sensor; The step of constructing an observer for the fault sensor according to the fault sensor type comprises: Constructing a mathematical model of the active power filter according to the topological structure of the active power filter; Updating the mathematical model of the active power filter according to the stray resistance at the output end of the inverter; Based on the updated mathematical model of the active power filter, selecting the inverter output current as the state variable of the active power filter, and determining the state equation of the active power filter; The state equation is recursively updated based on an extended Kalman filter algorithm to obtain a mathematical model of an observer of the inverter output current sensor.

4. The fault-tolerant control method of active power filter according to claim 3, characterized in that: Outputting the observation value through the observer and performing fault-tolerant control on the faulty sensor through the observation value comprises: Outputting an observation value through a mathematical model of an observer of the inverter output current sensor; wherein the observation value is a state variable of an active power filter optimized by the observer; Using current sensors on other non-fault phases at the output end of the inverter to obtain current observation values ​​of the non-fault phases; Performing coordinate transformation on the current observation value of the non-fault phase to obtain the α-axis current component in the α-β coordinate system; Using the α-axis current component to update and correct the observed value to obtain an optimal observed value; The faulty sensor is controlled to be fault-tolerant by using the optimal observation value.

5. The fault-tolerant control method of active power filter according to claim 1, characterized in that: When the fault sensor type is a DC side voltage sensor; The step of constructing an observer for the fault sensor according to the fault sensor type comprises: Constructing a mathematical model of the active power filter according to the topological structure of the active power filter; Converting the mathematical model of the active power filter into a mathematical model in a synchronous rotating coordinate system; Based on the mathematical model of the active power filter in the synchronous rotating coordinate system, the DC side voltage of the DC side voltage sensor is selected as the state variable of the active power filter to determine the state equation of the active power filter; The state equation is recursively updated based on an extended Kalman filter algorithm to obtain a mathematical model of an observer of the DC side voltage sensor.

6. The fault-tolerant control method of active power filter according to claim 5, characterized in that: Outputting the observation value through the observer and performing fault-tolerant control on the faulty sensor through the observation value comprises: Outputting an observation value through a mathematical model of an observer of the DC side voltage sensor; wherein the observation value is a state variable of an active power filter optimized by the observer; Using current sensors on other non-fault phases at the output end of the inverter to obtain current observation values ​​of the non-fault phases; Performing coordinate transformation on the current observation value of the non-fault phase to obtain a q-axis current component and a d-axis current component in a qd coordinate system; Using the q-axis current component and the d-axis current component to update and correct the observed value to obtain an optimal observed value; The faulty sensor is controlled to be fault-tolerant by using the optimal observation value.

7. An active power filter fault-tolerant control system, characterized in that: include: A fault type determination module, configured to determine the type of the fault sensor in response to a fault-tolerant control request of the fault sensor of the active power filter; wherein the fault sensor type includes a grid voltage sensor, an inverter output current sensor, and a DC side voltage sensor; An observer construction module, used to construct an observer of the fault sensor according to the type of the fault sensor; The fault-tolerant control module is used to output the observation value through the observer and perform fault-tolerant control on the faulty sensor through the observation value.

8. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the active power filter fault-tolerant control method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the active power filter fault-tolerant control method according to any one of claims 1 to 6 are implemented.

10. A computer program product, characterized in that The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the steps of the active power filter fault-tolerant control method according to any one of claims 1 to 6.

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