Harmonic voltage compensation controller and control method of three-phase voltage source inverter

Abstract

The invention relates to the technical field of voltage source type inverters, particularly discloses a harmonic voltage compensation controller and a harmonic voltage compensation control method of a three-phase voltage source type inverter, and aims to solve the problem that the harmonic voltage compensation of the three-phase voltage source type inverter cannot be realized under the condition of filter parameter perturbation and nonlinear load. The technical problem of how to ensure the global bounded stability of the system and effectively compensate the harmonic voltage under the condition of simplifying the sensor configuration is solved. According to the invention, a nonlinear double-closed-loop control structure only needing a filter inductance current sensor and a capacitor voltage sensor is designed, an improved passive control equation is adopted in a voltage outer loop, and a nonlinear control item combining a voltage error absolute value item and a sign function is introduced in a current inner loop; therefore, under the condition that only two control parameters are used, effective suppression of the harmonic voltage is achieved, low total harmonic distortion of the output voltage is still kept when parameter perturbation is large, meanwhile, high robustness to load sudden change, reference voltage switching and frequency change is achieved, and system cost and control complexity are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of voltage source inverter technology, and more particularly to a harmonic voltage compensation controller and control method for a three-phase voltage source inverter. Background Technology

[0002] With the rapid development of renewable energy, three-phase voltage source inverters (VSIs) can operate in both stand-alone and grid-connected modes, and are widely used in energy storage systems, microgrids, and V2G (vehicle-to-grid) applications for electric vehicles. In stand-alone or islanded modes, when the grid is unavailable, local loads must be powered by distributed generation (DG) systems, which function as controlled voltage sources. Therefore, a fundamental requirement is to regulate parameters such as voltage amplitude and frequency to ensure rapid dynamic response and zero steady-state error. However, in practical inverter applications, filter parameters may be perturbed by environmental factors (such as changes in operating temperature). Furthermore, the presence of nonlinear loads (such as uncontrolled rectifier bridges and switching power supplies) can cause output current distortion, leading to output voltage distortion. Moreover, due to the distributed nature of DG systems, using large-capacity power quality compensation devices significantly increases system costs. If the VSI can provide auxiliary power quality compensation, the total cost of the DG system will be greatly reduced. Therefore, developing a three-phase VSI control strategy that can effectively compensate for harmonic voltages even when filter parameters are perturbed is of great significance. On the other hand, if the controller can use as few sensors as possible, the system cost will be greatly reduced, which has great engineering value.

[0003] In linear controllers, proportional-integral (PI) control and proportional-resonant (PR) control are widely used. PI controllers are the most commonly used due to their simple structure and ease of implementation. However, their parameters are highly dependent on the accurate system transfer function, and during parameter tuning, the load is often simplified to a resistive load, making both PI and PR controllers very sensitive to changes in filter parameters and load conditions. On the other hand, PR controllers can effectively compensate for specific harmonic voltages, such as the 5th, 7th, and 11th harmonics. However, as the order of the harmonics being compensated increases, the number of parameters in the PR controller increases, making parameter tuning more difficult.

[0004] Numerous studies have explored nonlinear controllers to achieve greater robustness. Compared to traditional methods, nonlinear control exhibits stronger robustness against external disturbances and parameter perturbations. These studies, in addition to using filter inductor current sensors for overcurrent protection of switching devices and common point of coupling (PCC) voltage sensors for phase-locked loops, also employ output current sensors or filter capacitor current sensors. This undoubtedly increases system cost.

[0005] Passive control (PBC) is a nonlinear control strategy based on the energy concept. This algorithm exhibits high stability and robustness, and its design is simple and easy to implement. Therefore, it is suitable for industrial control applications in complex environments and with fluctuating parameters. The design of a passive controller primarily involves injecting damping into the system, causing the system's energy function to converge to the desired energy function, thus rendering the closed-loop system passive. Therefore, passive control has strong robustness to system parameter fluctuations and external disturbances. However, current passive control schemes still utilize output current sensors or filter capacitor current sensors, increasing system cost. Summary of the Invention

[0006] This invention provides a harmonic voltage compensation controller and control method for a three-phase voltage source inverter. The technical problem it solves is: how to ensure the global bounded stability of the system under parameter perturbation and nonlinear load with a simplified sensor configuration.

[0007] To address the above technical problems, this invention provides a harmonic voltage compensation controller for a three-phase voltage source inverter. The three-phase voltage source inverter includes a DC voltage... DC side capacitor A three-phase inverter circuit, and three LC parallel filter circuits connected to the three-phase output terminals of the three-phase inverter circuit. Each LC parallel filter circuit includes parallel inductors. and capacitor The key feature is that the harmonic voltage compensation controller includes an outer voltage loop controller, an inner current loop controller, a filter inductor current sensor, a filter capacitor voltage sensor, a current coordinate converter, a voltage coordinate converter, a modulation signal coordinate converter, and a PWM modulator.

[0008] The filter inductor current sensor detects the three-phase inductor current of the filter. Filter capacitor voltage sensor detects the three-phase capacitor voltage of the filter. From the current coordinate converter and the voltage coordinate converter respectively Coordinate system transformation coordinate system, to obtain the corresponding Current and Voltage Then, Current Input the voltage outer loop controller and the current inner loop controller, and... Voltage Input the voltage outer loop controller, and simultaneously Reference voltage Input the voltage outer loop controller and the current inner loop controller;

[0009] Current , Voltage and Reference voltage After calculation by the outer voltage loop controller, the reference value of the filter inductor current is obtained. Input the current inner loop controller;

[0010] Filter inductor current reference value , Reference voltage and Current Through the calculations of the aforementioned inner current loop controller, the following is obtained: Modulated signal in coordinates Input the modulation signal coordinate converter;

[0011] The modulation signal coordinate converter will Modulated signal in coordinates Switch to In coordinate system, we obtain The modulation signal in the coordinate system is input to the PWM modulator;

[0012] The PWM modulator modulates the signal through carrier modulation. The modulation signal under the coordinate system is modulated, and the output PWM drive signal is applied to the three-phase inverter circuit, so that the three-phase inverter circuit outputs three-phase AC power.

[0013] Preferably, the control equation of the voltage outer loop controller is:

[0014] ,

[0015] in, , These respectively represent the outputs of the outer loop voltage controller. axis, Reference value for filter inductor current on the shaft. , These respectively represent the values ​​obtained by the current coordinate converter. axis, The filter inductor current of the shaft, , These respectively represent the values ​​obtained by the voltage coordinate converter. axis, The filter capacitor voltage of the axis, , for , The corresponding reference voltage, , They are respectively , The first derivative with respect to time, This represents the voltage outer loop gain.

[0016] Preferably, the control equation of the current inner loop controller is:

[0017] ,

[0018] in, , The outputs of the inner current loop controller are respectively axis, The modulation signal of the shaft, This is the sum of the current sensing resistor for the filter inductor current detection and the parasitic resistance of the filter inductor. , They are respectively, For the inner current loop gain, For a sign function, when the independent variable is greater than 0, less than 0, or equal to 0, They are equal to 1, -1, and 0 respectively.

[0019] Preferably, the voltage outer loop gain and current inner loop gain Determined through the following steps:

[0020] Based on the bounded stability analysis results of the system, determine the voltage outer loop gain that satisfies the given allowable error range. The range of values ​​for ;

[0021] Linearizing the system's differential equations near the steady-state operating point yields the result related to the current inner loop gain. and voltage outer loop gain Related time constant The expression;

[0022] Determine the time constant based on the bandwidth of the control system and the delay constraints of digital control. The value of ;

[0023] The determined time constant Substitute the time constant The expression for the inner current loop gain is obtained. and voltage outer loop gain ;

[0024] voltage outer loop gain Within the range of values, for satisfying the current inner loop gain and voltage outer loop gain The dynamic response is obtained through simulation or experimentation using combinations of values;

[0025] Analyze the dynamic response to determine the optimal combination of values ​​for the final inner current loop gain. and voltage outer loop gain .

[0026] Preferably, the voltage outer loop gain The range of values ​​is , This represents the maximum magnitude of the disturbance term in the linear term. Given an error threshold; time constant The expression is .

[0027] This invention also provides a harmonic voltage compensation control method for a three-phase voltage source inverter, used in the harmonic voltage compensation controller of the three-phase voltage source inverter. The key feature is that the method includes the following steps:

[0028] Detection filter three-phase inductor current Detection filter three-phase capacitor voltage From respectively Coordinate system transformation coordinate system, to obtain the corresponding Current and Voltage ;

[0029] Will Current The input voltage outer loop controller and the current inner loop controller will Voltage Input the voltage outer loop controller, and simultaneously Reference voltage Input the voltage outer loop controller and the current inner loop controller;

[0030] Current , Voltage and Reference voltage After calculation by the outer voltage loop controller, the reference value of the filter inductor current is obtained. Input the current inner loop controller;

[0031] Filter inductor current reference value , Reference voltage and Current Through the calculations of the aforementioned inner current loop controller, the following is obtained: Modulated signal in coordinates ;

[0032] Will Modulated signal in coordinates Switch to In coordinate system, we obtain Modulated signal in coordinate system;

[0033] By carrier modulation The modulation signal under the coordinate system is modulated, and the output PWM drive signal is applied to the three-phase inverter circuit, so that the three-phase inverter circuit outputs three-phase AC power.

[0034] Furthermore, the control equation of the voltage outer loop controller is:

[0035] ,

[0036] in, , These respectively represent the outputs of the outer loop voltage controller. axis, Reference value for filter inductor current on the shaft. , These respectively represent the values ​​obtained by the current coordinate converter. axis, The filter inductor current of the shaft, , These respectively represent the values ​​obtained by the voltage coordinate converter. axis, The filter capacitor voltage of the axis, , for , The corresponding reference voltage, , They are respectively , The first derivative with respect to time, This represents the voltage outer loop gain.

[0037] Furthermore, the control equation of the current inner loop controller is:

[0038] ,

[0039] in, , The outputs of the inner current loop controller are respectively axis, The modulation signal of the shaft, This is the sum of the current sensing resistor for the filter inductor current detection and the parasitic resistance of the filter inductor. , They are respectively , The first derivative with respect to time, For the inner current loop gain, For a sign function, when the independent variable is greater than 0, less than 0, or equal to 0, They are equal to 1, -1, and 0 respectively.

[0040] Furthermore, the voltage outer loop gain and current inner loop gain Determined through the following steps:

[0041] Based on the bounded stability analysis results of the system, determine the voltage outer loop gain that satisfies the given allowable error range. The range of values ​​for ;

[0042] Linearizing the system's differential equations near the steady-state operating point yields the result related to the current inner loop gain. and voltage outer loop gain Related time constant The expression;

[0043] Determine the time constant based on the bandwidth of the control system and the delay constraints of digital control. The value of ;

[0044] The determined time constant Substitute the time constant The expression for the inner current loop gain is obtained. and voltage outer loop gain ;

[0045] voltage outer loop gain Within the range of values, for satisfying the current inner loop gain and voltage outer loop gain The dynamic response is obtained through simulation or experimentation using combinations of values;

[0046] Analyze the dynamic response to determine the optimal combination of values ​​for the final inner current loop gain. and voltage outer loop gain .

[0047] Preferably, the voltage outer loop gain The range of values ​​is , This represents the maximum magnitude of the disturbance term in the linear term. Given an error threshold; time constant The expression is .

[0048] The harmonic voltage compensation controller and control method for a three-phase voltage source inverter provided by this invention have the following main contributions:

[0049] 1) Based on the passive current controller, a passive dual closed-loop controller for three-phase voltage source inverters is derived, which enables the controller to compensate for harmonic voltages.

[0050] 2) Based on the passive dual closed-loop controller, the absolute value term of the voltage error is introduced into the current inner loop controller, which effectively solves the chattering problem caused by the sliding phase term in the current inner loop controller.

[0051] 3) A nonlinear control term was introduced into the passive current inner loop controller, enhancing the system's robustness. This allows the system to effectively compensate for harmonic voltages even under 50% parameter perturbation.

[0052] 4) For the proposed controller, the system stability was analyzed in detail and a parameter tuning method was given;

[0053] 5) The proposed controller has only two control parameters, which greatly simplifies the system design;

[0054] 6) The proposed controller only uses a filter inductor current sensor and an output voltage sensor, which saves system costs. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the overall structure of the harmonic voltage compensation controller for a three-phase voltage source inverter provided in an embodiment of the present invention;

[0056] Figure 2 This is a schematic diagram of the nonlinear dual closed-loop control structure of a conventional three-phase voltage source inverter with an output current sensor provided in an embodiment of the present invention.

[0057] Figure 3 This is provided by the embodiments of the present invention. For example Figure 2 The corresponding operational principle diagram of the control structure;

[0058] Figure 4 This is provided by the embodiments of the present invention. For example Figure 1 The corresponding operational principle diagram of the control structure;

[0059] Figure 5 This is a schematic diagram of the prototype structure of the GaN / Si hybrid ANPC inverter provided in an embodiment of the present invention;

[0060] Figure 6 This is a schematic diagram of the RCD nonlinear load circuit used in the experiment provided in the embodiment of the present invention;

[0061] Figure 7 These are experimental waveforms of the output three-phase voltage and phase a output current under different load conditions provided in the embodiments of the present invention;

[0062] Figure 8 This is the corresponding embodiment provided by the present invention. Figure 7 Total harmonic distortion (THD) analysis diagram of output phase voltage under different load conditions;

[0063] Figure 9 This is a waveform comparison diagram (including a magnified view of the peak) of the output phase voltage tracking reference voltage provided in the embodiment of the present invention.

[0064] Figure 10 This is a waveform diagram of phase voltage and output current under different loads when the output voltage frequency is 60Hz, provided by an embodiment of the present invention.

[0065] Figure 11 This is a waveform diagram of phase voltage and output current during dynamic load switching and dynamic reference voltage switching provided in an embodiment of the present invention. Detailed Implementation

[0066] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0067] The harmonic voltage compensation controller for a three-phase voltage source inverter provided in this embodiment of the invention has the following structure: Figure 1 As shown, a nonlinear dual-closed-loop control structure without an output current sensor is adopted. Figure 1 In this context, three-phase voltage source inverters include DC voltage... DC side capacitor A three-phase inverter circuit consisting of 6 MOSFETs; and three LC parallel filter circuits connected to the three-phase output terminals of the three-phase inverter circuit (each LC parallel filter circuit includes a parallel inductor). and capacitor The resistor r is the sum of the current-sensing resistor for detecting the filter inductor current and the parasitic resistance of the filter inductor. Since the current-sensing resistor is only... Therefore, in control system analysis, the resistor r is uniformly regarded as a filter inductor. The parasitic resistance. In application, the output terminals of the three LC parallel filter circuits are each connected through an inductor ( Connect nonlinear loads or resistive loads.

[0068] The nonlinear dual-closed-loop control structure designed in this embodiment includes a voltage outer loop controller, a current inner loop controller, a filter inductor current sensor, a filter capacitor voltage sensor, a current coordinate converter, a voltage coordinate converter, a modulation signal coordinate converter, and a PWM modulator. The filter inductor current sensor detects the three-phase inductor current of the filter. (include , and ), Filter capacitor voltage sensor detects the three-phase capacitor voltage of the filter. (include , and ), respectively through current coordinate converter and voltage coordinate converter from Coordinate system transformation coordinate system, to obtain the corresponding Current (include , )and Voltage (include , Then, Current The input voltage outer loop controller and the current inner loop controller will Voltage Input voltage outer loop controller, simultaneously Reference voltage (include , Input voltage outer loop controller and current inner loop controller. Current , Voltage and Reference voltage After calculation by the voltage outer loop controller, the reference value of the filter inductor current is obtained. (include , Input current inner loop controller. Filter inductor current reference value. , Reference voltage and Current Through the calculations of the current inner loop controller, the following is obtained: Modulated signal in coordinates (include and The input modulated signal coordinate converter will... Modulated signal in coordinates Switch to In coordinate system, we obtain Modulated signal in coordinates (include , and The input is to the PWM modulator. Finally, the PWM modulator modulates the signal via carrier modulation. The modulation signal in coordinate mode is modulated, and the PWM drive signal of the inverter switching device is applied to the three-phase inverter circuit, causing the three-phase inverter circuit to output three-phase AC power. This forms a control closed loop, stabilizing the output voltage of the three-phase inverter circuit at the reference voltage.

[0069] Figure 2 This is a nonlinear dual-closed-loop control structure for a three-phase voltage source inverter with an output current sensor, and... Figure 1 The difference lies in the use of a filter output current in the voltage outer loop controller. (include , , , switch to Coordinate systems include , ),and Figure 1 The voltage outer loop uses a filter inductor current. Replaced output current part.

[0070] Figure 3 Drawing Taking the shaft as an example Figure 2 The operational principle diagram of the corresponding nonlinear dual closed-loop control structure, and the derivation process of the control equations used by the voltage outer loop controller and the current inner loop controller are as follows.

[0071] According to the KVL and KCL equations of the LC filter, we can obtain:

[0072] (1)

[0073] in, , , , They represent , , , The first derivative with respect to time.

[0074] Equation (1) can be written in Euler-Lagrange (EL) form:

[0075] (2)

[0076] in, The input vector represents the port power variable injected externally into the LC filter system. This is the dissipation matrix, a positive semi-definite matrix, representing the dissipation (energy loss) part of the system, mainly the parasitic resistance of the inductor in this case; For state vectors, key variables describing the energy storage state of the system; The interconnection matrix, an antisymmetric matrix, describes the conservative (lossless) energy exchange paths between state variables within the system, such as the relationship between capacitor charging and discharging and inductor current. It reflects the internal structure of the system. for The first derivative with respect to time represents the rate of change of the state; This is the inertia (or mass / energy storage) matrix, a positive definite diagonal matrix whose elements represent the "inertia" of each energy storage element in the system, i.e., the inductance and capacitance values. It represents the rate of change of state. It is related to the system's momentum or "inertial force".

[0077] , , , , They are represented as follows:

[0078] (3)

[0079] Let the system energy function be: The rate of change of the energy stored in the system is: The top right corner mark This represents the matrix transpose. Therefore:

[0080] (4)

[0081] The passivity requirement of the system is known to be as follows:

[0082] (5)

[0083] in, This represents the rate at which the system receives input energy (corresponding to this embodiment). ), This represents the rate at which the system dissipates energy (corresponding to this embodiment). ).

[0084] Clearly, equation (4) satisfies the system's passivity requirement. Therefore, the three-phase voltage source inverter can be controlled by a passive controller. The actual value of the state vector is... The reference value of the state vector is set as The state vector error is defined as The three are represented as follows:

[0085] , (6)

[0086] in, , , , They represent , , , Reference values.

[0087] Substituting equation (6) into equation (2), we get:

[0088] (7)

[0089] in, , They are respectively , The first derivative with respect to time.

[0090] To accelerate the system convergence speed, a damping term is added to both sides of equation (7). :

[0091] (8)

[0092] in, This represents the damping injection gain matrix, used to introduce additional damping in a passive control framework to accelerate system convergence, as detailed below:

[0093] (9)

[0094] in, , These are the inner current loop gain and the outer voltage loop gain, respectively.

[0095] when Then, by expanding equation (8), we can obtain the current inner loop controller and voltage outer loop controller of the passive dual closed-loop controller:

[0096] (10)

[0097] in, , , , They are , , , The first derivative with respect to time.

[0098] Figure 2 , Figure 3 The passive dual-loop controller shown can guarantee system stability under a certain degree of parameter perturbation. However, when faced with harmonic voltages caused by nonlinear loads, it cannot effectively track the inner loop current, thus failing to effectively compensate for harmonic voltages and resulting in a degraded output voltage quality. The controller designed in this embodiment... Figure 1 The nonlinear dual-closed-loop controller shown is compared to Figure 1 Aside from the absence of three current sensors, the most crucial aspect lies in the unique design of the outer voltage loop controller and the inner current loop controller, which overcomes the problem of not being able to effectively compensate for harmonic voltages.

[0099] Specifically, Figure 4 Drawing Taking the shaft as an example Figure 1 The operational principle diagram of the corresponding nonlinear double-closed-loop control structure. (Reference) Figure 4 The control equation for the voltage outer loop controller is:

[0100] (11)

[0101] Comparing equations (10) and (11), it can be found that the controller proposed in this embodiment will convert the passive voltage outer loop equation into... use The replacement was performed. In a three-phase inverter, compared to a traditional passive controller, the controller proposed in this embodiment saves three current sensors and their sampling circuits. This significantly reduces system cost. Since the damping term of the voltage outer loop remains unchanged, it still possesses the robustness to parameter perturbations of a traditional passive controller. However, due to the neglect of the influence of the filter capacitor current, the system introduces sinusoidal and cosine disturbance terms, resulting in the system only achieving bounded stability, which will be analyzed in detail below.

[0102] refer to Figure 4 The control equation for the inner current loop controller is:

[0103] (12)

[0104] in, For a sign function, when the independent variable is greater than 0, less than 0, or equal to 0, They are equal to 1, -1, and 0 respectively.

[0105] The nonlinear term of the current inner loop controller proposed in this embodiment introduces the absolute value of the voltage error. and On the one hand, introducing the absolute value of the error can reduce chattering in traditional sliding diaphragm control. On the other hand, unlike the traditional super-spiral sliding diaphragm controller where the sliding surface and the absolute value term are consistent, this approach... Where s is the sliding surface. In this embodiment, the absolute value term of the nonlinear control part is the voltage error of the outer loop, while the sign function term is the current error of the inner loop. This method introduces the outer loop voltage error into the nonlinear control part, which can further increase the robustness of the system and enable the controller to better compensate for harmonic voltages. Furthermore, the controller proposed in this embodiment eliminates the integral term in the super-spiral sliding diaphragm controller. This is because the nonlinear term is in the inner current loop and introduces the absolute value of the voltage outer loop error. In the voltage outer loop, this embodiment uses a passive controller, which itself has strong robustness and does not need to introduce an integral term to enhance the anti-interference capability of the system. Compared with the super-spiral sliding diaphragm controller, the controller proposed in this embodiment greatly simplifies the parameter design of the controller, so that the controller parameters only include the inner loop gain. and the gain of the outer loop The following section presents a stability analysis and parameter tuning for the proposed controller.

[0106] The KVL equation for the filter is expressed as:

[0107] (13)

[0108] Because it does not include a power control loop, the controller designed for this embodiment... shaft and Since the axes are identical and independent, subscripts are omitted in the stability proof. and Combining equations (12) and (13), we get:

[0109] (14)

[0110] Let voltage error , First derivative with respect to time By combining equations (11) and (14), we get:

[0111] (15)

[0112] in, express The second derivative with respect to time.

[0113] Substituting the actual reference voltage into equation (15), where Output voltage angular frequency The corresponding frequency ,get:

[0114] (16)

[0115] Observing equation (16), it can be found that there are sine or cosine perturbation terms in both the linear and nonlinear parts. This is because the sign function in the nonlinear part contains perturbation terms. This means the system can only guarantee bounded stability, meaning it can only tolerate errors. Fluctuating within a very small range, i.e. ,in Let be a given error threshold (a positive constant). We will now prove the bounded stability of the system's differential equations.

[0116] Define the Lyapunov functions of the system:

[0117] (17)

[0118] but Substituting equation (16) into the equation, we get:

[0119] (18)

[0120] In Input-to-State Stability (ISS) theory, when At that time, the system is stable from input to state, that is, the system state is stable. The influence of the disturbance is bounded, indicating that the system possesses robust stability in the presence of the disturbance. It is a positive definite function, representing the decay term of the system state. It's about disturbances. A positive definite function.

[0121] The perturbation term in the sign function sign Treating it as an external disturbance, we get:

[0122] (19)

[0123] in, This indicates that due to the disturbance term The existence of this introduces errors or uncertainties into the sign function. The maximum magnitude of the disturbance term in the linear term is Therefore, separating the disturbance term, we obtain:

[0124] (20)

[0125] Then the system attenuation term Disturbance term amplitude Therefore, as long as the magnitude of the attenuation term is greater than the magnitude of the disturbance term, the system is globally bounded and stable, that is:

[0126] ,(twenty one)

[0127] Parasitic resistance And because Let's assume here. By utilizing Bounded scaling, taking sufficient conditions, and considering the worst-case scenario ( A simplified condition derived from this is:

[0128] ,(twenty two)

[0129] Therefore, we obtain The range of values Observing equation (22) reveals the accuracy error. The smaller, the more It will get bigger and bigger, when hour, However, due to system bandwidth limitations and the impact of latency in the DSP, and Further optimization is needed. The system differential equations will be linearized near the steady-state operating point, and the results will be given in conjunction with the system control bandwidth. and The range of values ​​for .

[0130] Since the system has been proven to remain stable under the influence of disturbance terms, and linearization analysis primarily focuses on performance optimization, the disturbance terms are ignored. The linearized system differential equation becomes:

[0131] ,(twenty three)

[0132] This is a first-order linear system with the following time constant:

[0133] .(twenty four)

[0134] To ensure that the effect of delay on the system's phase is acceptable at the bandwidth frequency, system bandwidth and digital control delay constraints are typically satisfied. ,and , It represents the closed-loop bandwidth of the control system (used to characterize the dynamic response speed of the system). This represents the equivalent control delay of the digital control system (including the total delay introduced by sampling, calculation, and PWM update). Considering the actual control system delay in this embodiment is... The system time constant can be calculated to be approximately In the stability analysis Substituting into equation (24), we can calculate .

[0135] Based on the above analysis, the current inner loop gain With voltage outer loop gain The general design process can be summarized as follows:

[0136] (1) Based on the results of the system's bounded stability analysis, determine the range of acceptable error that satisfies the given tolerance. voltage outer loop gain The range of values ​​is determined to ensure that the system error converges to the predetermined range;

[0137] (2) Linearize the system differential equations near the steady-state operating point to obtain the gain of the inner current loop. and voltage outer loop gain Related time constant The expression;

[0138] (3) Determine the time constant based on the bandwidth of the control system and the delay constraints of digital control. The value of ;

[0139] (4) Determine the time constant Substitute the time constant The expression for the inner current loop gain is obtained. and voltage outer loop gain ;

[0140] (5) Gain in the outer voltage loop Within the range of values, for satisfying the current inner loop gain and voltage outer loop gain The dynamic response is obtained through simulation or experimentation using combinations of values;

[0141] (6) Analyze the dynamic response and determine the optimal combination of values ​​for the final inner current loop gain. and voltage outer loop gain .

[0142] Based on the above system, this embodiment also provides a harmonic voltage compensation control method for a three-phase voltage source inverter, which includes the following steps:

[0143] Detection filter three-phase inductor current Detection filter three-phase capacitor voltage From respectively Coordinate system transformation coordinate system, to obtain the corresponding Current and Voltage ;

[0144] Will Current The input voltage outer loop controller and the current inner loop controller will Voltage Input voltage outer loop controller, simultaneously Reference voltage Input voltage outer loop controller and current inner loop controller;

[0145] Current , Voltage and Reference voltage After calculation by the voltage outer loop controller, the reference value of the filter inductor current is obtained. Input current inner loop controller;

[0146] Filter inductor current reference value , Reference voltage and Current Through the calculations of the current inner loop controller, the following is obtained: Modulated signal in coordinates ;

[0147] Will Modulated signal in coordinates Switch to In coordinate system, we obtain Modulated signal in coordinate system;

[0148] By carrier modulation The modulation signal under the coordinate system is modulated, and the output PWM drive signal is applied to the three-phase inverter circuit, so that the three-phase inverter circuit outputs three-phase AC power.

[0149] The design and control of the voltage outer loop controller and current inner loop controller are consistent and will not be repeated here. It is important to emphasize that the embodiments described in this invention can be implemented in computing systems including backend components (e.g., as a data server), or computing systems including middleware components (e.g., an application server), or computing systems including frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with the implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0150] Computer programs for implementing the methods and systems of the present invention may be written in any combination of one or more programming languages ​​and stored in a computer-readable storage medium. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0151] Computer-readable storage media can be tangible media that may contain or store computer programs for use by or in conjunction with an instruction execution system, apparatus, or device. Computer-readable storage media can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, computer-readable storage media can be machine-readable signal media. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0152] The inverter structure used in the experiment is as follows: Figure 5 As shown in the figure. This embodiment uses a 10kW GaN / Si hybrid ANPC inverter prototype to verify the proposed controller. Red represents GaN MOSFETs, and blue represents Si MOSFETs. It should be noted that, firstly, since the controller and modulation module are decoupled in this embodiment, it is also applicable to other three-phase voltage source inverters, including two-level inverters and other types of three-level inverters such as TNPC or NPC inverters. Secondly, the ANPC prototype used in this embodiment employs an LCL filter. Because a snubber resistor is added to the filter capacitor of the LCL filter in this embodiment, the LCL resonance peak is effectively suppressed. Furthermore, only the filter inductor is used in the derivation and simulation of the controller equations. The current and voltage across the filter capacitor C are not involved; the filter inductor is not considered. Therefore, it is reasonable and effective to use a GaN / Si hybrid ANPC with snubber resistors to experimentally verify the proposed controller in this embodiment. Simulation and experimental parameters are shown in Table 1.

[0153] Table 1 Experimental Parameter Settings

[0154]

[0155] The main control circuit is based on the TMS320F280049C DSP; the GaN MOSFET is the Texas Instruments (TI) LMG3425R030; and the Si MOSFET is the ON Semiconductor FCH040N65S3-F155-ND. The nonlinear load used in the experiment is as follows: Figure 6 The RCD load shown includes a rectifier, capacitor, and resistive load.

[0156] The experiment is divided into harmonic compensation verification and parameter dynamic change verification. The harmonic compensation verification is further divided into filter parameter perturbation and output voltage frequency change; the parameter dynamic change is further divided into load dynamic change and reference voltage dynamic change.

[0157] Figure 7 The output three-phase phase voltages VAO, VBO, and VCO (i.e., VCO) under different load conditions. , and ) and the output current IAO of phase a (i.e. The waveform of ), where Figure 7 (a) and Figure 7 In (b), the load is linear. Figure 7 (c) and Figure 7 In the middle (d), a linear load is superimposed with a nonlinear load. Figure 7 (e) and Figure 7 In the middle (f), the load is nonlinear. Figure 7 (a) Figure 7 (c) and Figure 7 In the middle (e), the filter parameters are not perturbed. Figure 7 (b) Figure 7 (d) and Figure 7 In the middle (f), the filter parameters decrease by 50%. From... Figure 7 It can be seen that under RCD nonlinear load conditions, when the filter parameters decrease by 50%, the proposed controller controls the THD of the inverter output voltage to 3.43%. This effectively verifies that the proposed controller has robustness to filter parameter perturbations and good harmonic voltage compensation effect. Compared with the case where the filter parameters are not perturbed, the THD of the output voltage increases. This is because reducing the filter parameters leads to a larger cutoff frequency, thereby reducing the attenuation capability of low-frequency harmonics and resulting in an increase in THD.

[0158] Figure 8 for Figure 7 (a) Figure 7 (c) and Figure 7 Under the medium (e) operating condition, the waveform of the output phase voltage tracking the reference voltage. Figure 8 (a) Figure 8 (b) and Figure 8 (c) respectively correspond to Figure 7 (a) Figure 7 (c) and Figure 7 THD analysis in (e). From Figure 8 It can be seen that the RCD load mainly increases the 5th, 7th, and 11th harmonics compared to the resistive load.

[0159] Figure 9 To output the waveform of the phase voltage tracking the reference voltage (-ref), Figure 9 middle Figure 9 In the diagram, (a), (c), and (e) represent a linear load, a linear load superimposed with a nonlinear load, and a nonlinear load, respectively. Figure 9 (b), (d), and (f) are respectively Figure 9 The magnified waveforms at the peak values ​​in (a), (c), and (e) are shown. Figure 9 It can be seen that the peak error between the output phase voltage and the reference voltage is controlled within... Within.

[0160] Figure 10 The waveforms of phase voltage and output current at a frequency of 60Hz under different loads are shown. Figure 9 In the diagram, (a), (c), and (e) represent a linear load, a linear load superimposed with a nonlinear load, and a nonlinear load, respectively. The controller parameters are... and and Figure 7 Same. Under RCD load conditions, the phase voltage THD is 3.12%. Comparison Figure 7 and Figure 10 It can be seen that the proposed controller has good robustness to changes in output voltage frequency, and the harmonic voltage compensation effect is basically consistent.

[0161] Figure 11 The waveforms of phase voltage and output current are based on dynamic changes in load and reference voltage. Figure 11 In (a), the dynamic switching from resistive load to nonlinear load is shown. Figure 11 (b) shows the dynamic switching from a 110V reference voltage to a 220V reference voltage. Figure 11 It can be seen that the proposed controller has good robustness to load switching and reference voltage switching, and the time from the switching moment to the steady state is less than 2.4ms.

[0162] In summary, this invention presents a nonlinear dual-loop controller for three-phase voltage source inverters under parameter perturbation. The proposed controller utilizes only filter inductor current sensors and output voltage sensors, saving system costs. Global asymptotic stability of the system is proven by combining sliding film theory and the control bandwidth of the inner and outer loops, and a parameter tuning method for the controller is provided. Experiments verify that the controller still exhibits excellent harmonic voltage compensation even with a 50% filter parameter perturbation and a three-phase uncontrolled rectifier bridge load, maintaining a total harmonic distortion rate of 3.43% for the output voltage. The proposed method demonstrates strong robustness to filter parameter perturbation, output voltage frequency changes, load switching, and dynamic reference voltage switching. The proposed controller uses only two control parameters, significantly simplifying system design. The proposed controller is suitable for energy systems with variable operating environments and load conditions, such as V2G electric vehicles and microgrids.

[0163] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. Harmonic voltage compensation controller for a three-phase voltage source inverter, which includes DC voltage... DC side capacitor A three-phase inverter circuit, and three LC parallel filter circuits connected to the three-phase output terminals of the three-phase inverter circuit. Each LC parallel filter circuit includes parallel inductors. and capacitor Its features are: The harmonic voltage compensation controller includes an outer voltage loop controller, an inner current loop controller, a filter inductor current sensor, a filter capacitor voltage sensor, a current coordinate converter, a voltage coordinate converter, a modulation signal coordinate converter, and a PWM modulator. The filter inductor current sensor detects the three-phase inductor current of the filter. Filter capacitor voltage sensor detects the three-phase capacitor voltage of the filter. From the current coordinate converter and the voltage coordinate converter respectively Coordinate system transformation coordinate system, to obtain the corresponding Current and Voltage Then, Current Input the voltage outer loop controller and the current inner loop controller, and... Voltage Input the voltage outer loop controller, and simultaneously Reference voltage Input the voltage outer loop controller and the current inner loop controller; Current , Voltage and Reference voltage After calculation by the outer voltage loop controller, the reference value of the filter inductor current is obtained. Input the current inner loop controller; Filter inductor current reference value , Reference voltage and Current Through the calculations of the aforementioned inner current loop controller, the following is obtained: Modulated signal in coordinates Input the modulation signal coordinate converter; The modulation signal coordinate converter will Modulated signal in coordinates Switch to In coordinate system, we obtain The modulation signal in the coordinate system is input to the PWM modulator; The PWM modulator modulates the signal through carrier modulation. The modulation signal under the coordinate system is modulated, and the output PWM drive signal is applied to the three-phase inverter circuit, so that the three-phase inverter circuit outputs three-phase AC power.

2. The harmonic voltage compensation controller for a three-phase voltage source inverter according to claim 1, characterized in that, The control equation for the voltage outer loop controller is: ， in, , These respectively represent the outputs of the outer loop voltage controller. axis, Reference value for filter inductor current on the shaft. , These respectively represent the values ​​obtained by the current coordinate converter. axis, The filter inductor current of the shaft, , These respectively represent the values ​​obtained by the voltage coordinate converter. axis, The filter capacitor voltage of the axis, , for , The corresponding reference voltage, , They are respectively , The first derivative with respect to time, This represents the voltage outer loop gain.

3. The harmonic voltage compensation controller for a three-phase voltage source inverter according to claim 2, characterized in that, The control equation for the current inner loop controller is: ， in, , The outputs of the inner current loop controller are respectively axis, The modulation signal of the shaft, This is the sum of the current sensing resistor for the filter inductor current detection and the parasitic resistance of the filter inductor. , They are respectively , The first derivative with respect to time, For the inner current loop gain, For a sign function, when the independent variable is greater than 0, less than 0, or equal to 0, They are equal to 1, -1, and 0 respectively.

4. The harmonic voltage compensation controller for a three-phase voltage source inverter according to claim 3, characterized in that, Voltage outer loop gain and current inner loop gain Determined through the following steps: Based on the bounded stability analysis results of the system, determine the voltage outer loop gain that satisfies the given allowable error range. The range of values ​​for; Linearizing the system's differential equations near the steady-state operating point yields the result related to the current inner loop gain. and voltage outer loop gain Related time constant The expression; Determine the time constant based on the bandwidth of the control system and the delay constraints of digital control. The possible values ​​of ; The determined time constant Substitute the time constant The expression for the inner current loop gain is obtained. and voltage outer loop gain ; voltage outer loop gain Within the range of values, for satisfying the current inner loop gain and voltage outer loop gain The dynamic response is obtained through simulation or experimentation using combinations of values; Analyze the dynamic response to determine the optimal combination of values ​​for the final inner current loop gain. and voltage outer loop gain .

5. The harmonic voltage compensation controller for a three-phase voltage source inverter according to claim 4, characterized in that: Voltage outer loop gain The range of values ​​is , This represents the maximum magnitude of the disturbance term in the linear term. Given an error threshold; time constant The expression is .

6. A harmonic voltage compensation control method for a three-phase voltage source inverter, used in the harmonic voltage compensation controller of the three-phase voltage source inverter according to any one of claims 1 to 5, characterized in that, The method includes the following steps: Detection filter three-phase inductor current Detection filter three-phase capacitor voltage From respectively Coordinate system transformation coordinate system, to obtain the corresponding Current and Voltage ; Will Current The input voltage outer loop controller and the current inner loop controller will Voltage Input the voltage outer loop controller, and simultaneously Reference voltage Input the voltage outer loop controller and the current inner loop controller; Current , Voltage and Reference voltage After calculation by the outer voltage loop controller, the reference value of the filter inductor current is obtained. Input the current inner loop controller; Filter inductor current reference value , Reference voltage and Current Through the calculations of the aforementioned inner current loop controller, the following is obtained: Modulated signal in coordinates ; Will Modulated signal in coordinates Switch to In coordinate system, we obtain Modulated signal in coordinate system; By carrier modulation The modulation signal under the coordinate system is modulated, and the output PWM drive signal is applied to the three-phase inverter circuit, so that the three-phase inverter circuit outputs three-phase AC power.

7. The harmonic voltage compensation control method for a three-phase voltage source inverter according to claim 6, characterized in that, The control equation for the voltage outer loop controller is: ， in, , These respectively represent the outputs of the outer loop voltage controller. axis, Reference value for filter inductor current on the shaft. , These respectively represent the values ​​obtained by the current coordinate converter. axis, The filter inductor current of the shaft, , These respectively represent the values ​​obtained by the voltage coordinate converter. axis, The filter capacitor voltage of the axis, , for , The corresponding reference voltage, , They are respectively , The first derivative with respect to time, This represents the voltage outer loop gain.

8. The harmonic voltage compensation control method for a three-phase voltage source inverter according to claim 7, characterized in that, The control equation for the current inner loop controller is: ， in, , The outputs of the inner current loop controller are respectively axis, The modulation signal of the shaft, This is the sum of the current sensing resistor for the filter inductor current detection and the parasitic resistance of the filter inductor. , They are respectively , The first derivative with respect to time, For the inner current loop gain, For a sign function, when the independent variable is greater than 0, less than 0, or equal to 0, They are equal to 1, -1, and 0 respectively.

9. The harmonic voltage compensation control method for a three-phase voltage source inverter according to claim 7 or 8, characterized in that, Voltage outer loop gain and current inner loop gain Determined through the following steps: Based on the bounded stability analysis results of the system, determine the voltage outer loop gain that satisfies the given allowable error range. The range of values ​​for; Linearizing the system's differential equations near the steady-state operating point yields the result related to the current inner loop gain. and voltage outer loop gain Related time constant The expression; Determine the time constant based on the bandwidth of the control system and the delay constraints of digital control. The possible values ​​of ; The determined time constant Substitute the time constant The expression for the inner current loop gain is obtained. and voltage outer loop gain ; voltage outer loop gain Within the range of values, for satisfying the current inner loop gain and voltage outer loop gain The dynamic response is obtained through simulation or experimentation using combinations of values; Analyze the dynamic response to determine the optimal combination of values ​​for the final inner current loop gain. and voltage outer loop gain .

10. The harmonic voltage compensation control method for a three-phase voltage source inverter according to claim 9, characterized in that: Voltage outer loop gain The range of values ​​is , This represents the maximum magnitude of the disturbance term in the linear term. Given an error threshold; time constant The expression is .

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