Direct current bus voltage control method, control system and electronic equipment

Abstract

The invention discloses a DC bus voltage control method, a DC bus voltage control system and electronic equipment. The control method comprises the following steps: determining a first voltage according to a direct-current bus voltage reference value, a direct-current bus voltage actual value and a voltage loop proportional-integral transfer function; under the condition that the absolute value of the variable quantity of the actual value of the direct-current bus voltage is larger than a set threshold value, a self-adaptive virtual capacitance transfer function is determined according to the change rate of the actual value of the direct-current bus voltage and a reference threshold value; determining a second voltage according to the DC bus voltage reference value, the DC bus voltage actual value and the adaptive virtual capacitance transfer function; and performing current loop decoupling control on the current deviation value to obtain a driving signal of the rectifier. Adaptive virtual capacitance parameter control can be added according to the change rate of the actual value of the DC bus voltage, rapid and stable control of the actual value of the DC bus voltage is achieved, and the requirement of the dynamic response performance of a transformer substation for rapidity is met.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current bus control, and in particular to a direct current bus voltage control method, a control system and electronic equipment. Background Art

[0002] As an important intermediate link in the transmission and distribution of electric energy in the distribution network, substations play important roles in power transmission, power flow optimization, voltage regulation, and power quality management. With the large-scale access of distributed new energy and flexible loads, the large-scale access to the power grid and the mismatch between the temporal and spatial characteristics of sources and loads have brought new challenges to the efficient and reliable operation of traditional substations due to the large randomness and volatility of distributed new energy generation. In substations, distributed energy such as photovoltaics and energy storage devices are all connected to the DC bus through extremely fast-responding power electronic converters. The intermittent and random nature of distributed energy will cause large power fluctuations, resulting in large fluctuations in the actual value of the DC bus voltage, threatening the safe and stable operation of substations.

[0003] In summary, with the development of new distribution systems, substations have an increasingly urgent need for fast and stable control of bus voltage. Traditional DC microgrid stability control methods can no longer meet the needs of new DC distribution systems for fast and stable control of bus voltage. Summary of the invention

[0004] The present invention provides a control method, a control system and an electronic device for a DC bus voltage, which can add adaptive virtual capacitor parameter control according to the actual value change rate of the DC bus voltage, so as to achieve rapid and stable control of the actual value of the DC bus voltage and meet the requirements of the dynamic response performance of the substation for rapidity.

[0005] In a first aspect, an embodiment of the present invention provides a method for controlling a DC bus voltage, comprising: obtaining an actual value of a DC bus voltage, a reference value of a DC bus voltage, and an AC side output current of a rectifier; performing a dq transformation on the AC side output current according to a phase difference of a phase-locked loop output to determine a d-axis current and a q-axis current of the AC side output current in a two-phase rotating coordinate system; determining a first voltage according to a DC bus voltage reference value, an actual value of the DC bus voltage, and a voltage loop proportional-integral transfer function; when an absolute value of a change in the actual value of the DC bus voltage is greater than a set threshold, determining an adaptive virtual capacitor transfer function according to a rate of change of the actual value of the DC bus voltage and a reference threshold; determining a second voltage according to the DC bus voltage reference value, the actual value of the DC bus voltage, and an adaptive virtual capacitor transfer function; determining a d-axis current reference value of the AC side output current in a two-phase rotating coordinate system according to the first voltage and the second voltage; calculating a current deviation value according to the d-axis current reference value, the q-axis current reference value, and the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system; and performing current loop decoupling control on the current deviation value to obtain a drive signal for the rectifier.

[0006] In a second aspect, an embodiment of the present invention provides a control system for a DC bus voltage, including:

[0007] An acquisition module is used to acquire the actual value of the DC bus voltage, the reference value of the DC bus voltage and the AC side output current of the rectifier; a transformation module is used to perform a dq transformation on the AC side output current according to the phase difference of the phase-locked loop output, so as to determine the d-axis current and q-axis current of the AC side output current in a two-phase rotating coordinate system; a current deviation value determination module is used to determine a first voltage according to the DC bus voltage reference value, the DC bus voltage actual value and the voltage loop proportional integral transfer function; when the absolute value of the change amount of the DC bus voltage actual value is greater than the set threshold, the adaptive virtual capacitor transfer function is determined according to the change rate of the DC bus voltage actual value and the reference threshold; the second voltage is determined according to the DC bus voltage reference value, the DC bus voltage actual value and the adaptive virtual capacitor transfer function; the d-axis current reference value of the AC side output current in the two-phase rotating coordinate system is determined according to the first voltage and the second voltage; the current deviation value is calculated according to the d-axis current reference value and the d-axis current of the AC side output current in the two-phase rotating coordinate system; and a control module is used to perform current loop decoupling control on the current deviation value to obtain a driving signal for the rectifier.

[0008] In a third aspect, an embodiment of the present invention provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the DC bus voltage control method provided in any embodiment of the present invention.

[0009] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable a processor to implement the DC bus voltage control method provided by any embodiment of the present invention when executed.

[0010] The control method of the DC bus voltage provided by the embodiment of the present invention is achieved by adding adaptive virtual capacitor parameter control according to the DC bus voltage change rate on the basis of the voltage and current dual closed-loop control method of the rectifier. When the absolute value of the change in the actual value of the DC bus voltage is greater than the set threshold, the adaptive virtual capacitor control is added. When the absolute value of the change in the actual value of the DC bus voltage increases, the capacitor is adaptively adjusted to increase, thereby improving the inertia capacity of the DC system and suppressing further deterioration of the voltage; when the absolute value of the change in the actual value of the DC bus voltage decreases, the virtual capacitor is adaptively adjusted to decrease, thereby reducing inertia and shortening the voltage recovery time. The substation adopting the proposed adaptive virtual capacitor control method can realize rapid and stable control of the substation bus voltage, can quickly smooth out rapid disturbances in the source, load and storage of the substation, and realize friendly interaction between the substation and the power grid.

[0011] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0013] Figure 1 It is a schematic diagram of the overall structure of a main circuit topology and a control method of a substation rectifier provided by an embodiment of the present invention;

[0014] Figure 2 is a flow chart of a method for controlling a DC bus voltage provided by an embodiment of the present invention;

[0015] Figure 3 is a schematic diagram of a hyperbolic tangent function in an adaptive virtual capacitor control provided by an embodiment of the present invention;

[0016] Figure 4 It is a control block diagram of the actual value of a DC bus voltage provided by an embodiment of the present invention;

[0017] Figure 5 is a flow chart of another method for controlling a DC bus voltage provided by an embodiment of the present invention;

[0018] Figure 6 It is the bus voltage fluctuation curve of the substation;

[0019] Figure 7 It is the active power waveform diagram of the interaction between the substation and the power grid;

[0020] Figure 8 It is the single-phase voltage waveform diagram on the grid side of the substation;

[0021] Fig. 9 It is the d-axis grid-connected current waveform of the substation;

[0022] Fig.10 It is a structural schematic diagram of a control system of a DC bus voltage provided by an embodiment of the present invention;

[0023] Fig.11 It is a structural schematic diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] 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 should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] Figure 1 FIG. 1 is a schematic diagram of the overall structure of a main circuit topology and control method of a substation rectifier provided by an embodiment of the present invention. Figure 1 As shown, C dc is the DC side capacitance, U dcref and U dc are the reference value and actual value of the substation bus voltage respectively; v a 、v b 、v c is the output voltage of the rectifier 100 on the AC side; i a 、i b 、i c is the output current of the rectifier 100 on the AC side; vga 、v gb 、v gc Connect the substation to the grid voltage; ga 、i gb 、i gc is the grid-connected current of the substation; C f , R d are filter capacitor and damping resistor respectively; L f , R f are the filter inductance and its equivalent resistance respectively; v d 、v q and i d 、i q are the voltage and current of the AC side of the rectifier 100 in the dq coordinate system respectively; i dref 、i qref are the reference values ​​of the d-axis and q-axis currents of the current loop in the dq coordinate system respectively; θ is the output phase difference of the phase-locked loop.

[0027] Figure 2 This is a flow chart of a method for controlling a DC bus voltage provided by an embodiment of the present invention. This embodiment is applicable to controlling the actual value of the DC bus voltage of a rectifier that interacts with a power grid in a substation. The method can be executed by a controller, which can be implemented in the form of hardware and / or software. The controller can be configured in a substation control system. Figure 1 and Figure 2 , the DC bus voltage control method includes:

[0028] S101. Obtain an actual value of a DC bus voltage, a reference value of a DC bus voltage, and an AC side output current of a rectifier.

[0029] Specifically, a high-precision voltage sensor can be installed at the DC bus terminal to measure the actual value of the DC bus voltage U in real time. dc The voltage sensor converts the voltage signal into an electrical signal (such as an analog voltage or current signal) and transmits it to the analog input module of the control system.

[0030] The data acquisition card or module in the control system receives the analog signal from the voltage sensor and converts it into a digital quantity so that the controller can read and process it.

[0031] DC bus voltage reference value U dcref It is usually preset according to the system design requirements and operating conditions. The operator can input the desired DC bus voltage reference value U through the control system's human-machine interface (such as touch screen, host computer software, etc.) dcref The input DC bus voltage reference value U dcref Stored in the controller's memory for use by the control algorithm.

[0032] In some embodiments, a current sensor may be installed on the AC side output line of the rectifier 100 to measure the AC side output current of the rectifier 100. The current sensor may be a Hall effect sensor, a current transformer, etc., which converts the current signal into an electrical signal that can be processed by the control system. Similar to the DC bus voltage measurement, the signal output by the current sensor is amplified, filtered, etc. by the signal conditioning circuit, and then converted into a digital quantity by the data acquisition module of the control system.

[0033] S102 , performing dq transformation on the AC side output current according to the phase difference of the phase-locked loop output, so as to determine the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system.

[0034] Specifically, the main function of the phase-locked loop is to track the phase and frequency of the grid voltage, and the phase difference signal it outputs can be used as the rotation angle reference for the dq transformation. Through this reference angle, the AC quantity in the three-phase stationary coordinate system can be converted to the dq coordinate system that rotates synchronously with the grid voltage, so that in the dq coordinate system, the d-axis can always be aligned with a certain direction of the grid voltage vector (for example, the d-axis is usually aligned with the real part of the grid voltage vector), which makes it easier to analyze and control physical quantities such as current.

[0035] For the three-phase alternating current i a 、i b 、i c (Assuming it is a sinusoidal current), the d-axis current i in the two-phase rotating coordinate system d and q-axis current i q It can be calculated by the following formula:

[0036]

[0037] Among them, i a 、i b 、i c is the AC side output current, i d 、i q They respectively represent the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system, and θ represents the phase difference of the phase-locked loop output.

[0038] In a synchronous rotating coordinate system, the d-axis current is usually related to the active power. By controlling the d-axis current, the active power input to the rectifier 100 can be adjusted. For example, in the DC bus voltage control, the d-axis current reference value is adjusted according to the change of the DC bus voltage, and then the active power absorbed by the rectifier 100 from the power grid is adjusted to stabilize the DC bus voltage.

[0039] The q-axis current is related to reactive power. Controlling the q-axis current can compensate or adjust the reactive power of the power grid and improve the power factor and other power grid performance indicators. In some applications, the q-axis current can be controlled to zero to achieve unity power factor operation and reduce reactive impact on the power grid.

[0040] S103 . Determine a first voltage according to a DC bus voltage reference value, an actual DC bus voltage value, and a voltage loop proportional-integral transfer function.

[0041] Specifically, in power systems, especially in scenarios involving DC bus voltage control, such as DC bus voltage stability control after distributed energy is connected to a substation, it is necessary to stabilize the DC bus voltage near a set reference value. This is because the stability of the DC bus voltage directly affects the normal operation of the entire system, and unstable DC bus voltage may cause equipment damage, power quality degradation and other problems.

[0042] The output of the proportional link is proportional to the input error (the difference between the reference value and the actual value of the DC bus voltage). Its function is to respond quickly to the current error and change the output in the direction of reducing the error. For example, if the actual value of the DC bus voltage is lower than the reference value, the proportional link will generate a corresponding control signal according to the size of the error, prompting the system to increase the output to increase the DC bus voltage. The larger the proportional coefficient, the faster the system responds to the error, but it may cause the system stability to decrease and overshoot to occur.

[0043] The output of the integral link is proportional to the integral of the input error. Its main function is to eliminate steady-state errors, that is, to ensure that the actual value of the DC bus voltage is equal to the reference value when the system reaches a steady state. Even if the proportional link has brought the system output close to the target value, there may still be small errors due to various factors. The integral link will continue to accumulate these errors and gradually adjust the output until the error is zero.

[0044] The process of determining the first voltage: First, calculate the DC bus voltage reference value U dcref With the actual value U dc The error between them, that is, e(s) = U dcref -U dc .

[0045] Voltage loop proportional-integral transfer function: H V (s) = k p_V +k i_V / s;

[0046] The first voltage u1(s) can be determined according to the following formula: dcref -U dc )H V (s);

[0047] Among them, k p_V Represents the proportional coefficient of the voltage loop proportional-integral transfer function, k i_V represents the integral coefficient of the voltage loop proportional-integral transfer function, s represents the Laplace transform factor, U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H V (s) represents the voltage loop proportional-integral transfer function.

[0048] S104 . When the absolute value of the change in the actual value of the DC bus voltage is greater than a set threshold, determine an adaptive virtual capacitor transfer function according to a change rate of the actual value of the DC bus voltage and a reference threshold.

[0049] Specifically, the threshold is set to determine whether the fluctuation of the DC bus voltage exceeds the acceptable range. When the absolute value of the change in the actual value of the DC bus voltage is greater than the set threshold, it means that the voltage fluctuation is large, which may have an adverse effect on the system performance. At this time, it is necessary to introduce adaptive virtual capacitor control to enhance the stability of the system. If the voltage fluctuation is within the threshold range, the system can assume that the current operating state is relatively stable and no additional virtual capacitor parameter adjustment is required, thereby reducing the calculation amount of the control algorithm and the complexity of the system.

[0050] The rate of change of the actual value of the DC bus voltage can intuitively reflect whether the voltage is rising or falling, and how fast it changes. By monitoring the rate of change of the actual value of the DC bus voltage, the control system can timely understand the dynamic characteristics of the DC bus voltage in order to make corresponding control decisions.

[0051] The magnitude of the rate of change of the actual value of the DC bus voltage determines the adjustment direction and amplitude of the adaptive virtual capacitor transfer function. When the voltage change rate (i.e., the rate of change of the actual value of the DC bus voltage) is large, it means that the system is in a rapid dynamic change process, and a larger virtual capacitor is needed to increase the system inertia and suppress further voltage fluctuations; conversely, when the change rate is small, the virtual capacitor is appropriately reduced to speed up the system response speed and shorten the time it takes for the voltage to return to stability.

[0052] When the absolute value of the change in the actual value of the DC bus voltage is greater than the set threshold, the adaptive virtual capacitor transfer function is used to calculate the appropriate virtual capacitor parameters according to the rate of change of the actual value of the DC bus voltage and the reference threshold. For example, if the voltage change rate is large, the adaptive virtual capacitor transfer function will output a larger capacitance value, which is equivalent to adding a larger virtual capacitor to the system, thereby enhancing the inertia of the system and suppressing the rapid rise or fall of the voltage; conversely, if the voltage change rate is small, the adaptive virtual capacitor transfer function will output a smaller capacitance value, reducing the system inertia and allowing the voltage to return to stability more quickly.

[0053] In some embodiments, the adaptive virtual capacitor transfer function may adopt a hyperbolic tangent function. The hyperbolic tangent function has good nonlinear characteristics and can smoothly adjust the output value (virtual capacitor parameter) according to the input value (ie, the rate of change of the actual value of the DC bus voltage). Figure 3 Schematic diagram of a hyperbolic tangent function in an adaptive virtual capacitor control provided by an embodiment of the present invention. Figure 3 , m1 and m2 represent reference thresholds, U s To set the threshold, the x-axis is the rate of change of the actual value of the DC bus voltage, and the y-axis is the adaptive virtual capacitor value. The specific values ​​of m1 and m2 can adjust the sensitivity of the control system to voltage fluctuations and the range of virtual capacitor adjustment. By reasonably setting m1 and m2, the virtual capacitor can be appropriately adjusted under different voltage fluctuations according to the actual needs and characteristics of the system. Smaller m1 and m2 values ​​may make the system more sensitive to smaller voltage changes and start larger virtual capacitor adjustments earlier; while larger values ​​relatively reduce the sensitivity of the system, making the virtual capacitor adjustment smoother, avoiding unnecessary impacts on the system caused by too frequent or drastic adjustments.

[0054] S105 . Determine a second voltage according to a DC bus voltage reference value, an actual DC bus voltage value, and an adaptive virtual capacitor transfer function.

[0055] Specifically, the second voltage u2(s) is determined according to the following formula: dcref -U dc )H ce (s);

[0056] Among them, U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H ce (s) represents the adaptive virtual capacitor transfer function.

[0057] S106. Determine a d-axis current reference value of the AC side output current in a two-phase rotating coordinate system according to the first voltage and the second voltage.

[0058] Specifically, the reference current i is determined according to the following formula: dref :

[0059] i dref =u1(s)+u2(s)=(U dcref -U dc )(H V (s)+H ce (s);

[0060] Where, u1(s) represents the first voltage, u2(s) represents the second voltage, and U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H V (s) represents the voltage loop proportional-integral transfer function, H ce (s) represents the adaptive virtual capacitor transfer function.

[0061] S107, calculating a current deviation value according to a d-axis current reference value, a q-axis current reference value, and a d-axis current and a q-axis current of the AC side output current in a two-phase rotating coordinate system.

[0062] Specifically, the d-axis current deviation value Δi d =i dref -i d The d-axis current deviation reflects the difference between the actual d-axis current and the desired d-axis current reference value, and is the basis for subsequent current loop control adjustment. In the power system, the d-axis current is usually related to the active power. By controlling the d-axis current deviation, the active power input to the rectifier 100 can be adjusted, thereby affecting the stability of the DC bus voltage. For example, if Δi d If Δi is positive, it means that the actual d-axis current is less than the reference value, and it may be necessary to increase the active power absorbed by the rectifier from the grid to increase the DC bus voltage. d If the value is negative, it may be necessary to reduce the active power input.

[0063] Calculate the q-axis current deviation Δi q =i qref -i q The q-axis current is related to reactive power. Controlling the q-axis current deviation can compensate or adjust the reactive power of the power grid and improve the power factor and other power grid performance indicators. For example, in some applications, the q-axis current is controlled to zero to achieve unity power factor operation. At this time, Δi q The size and positive or negative sign of reflects the degree of deviation between the actual q-axis current and the ideal state (q-axis current is zero). The control system adjusts the control signal according to this deviation value to make the q-axis current approach the reference value.

[0064] S108, performing current loop decoupling control on the current deviation value to obtain a driving signal for the rectifier.

[0065] In the three-phase rectifier control system, there is a coupling relationship between the d-axis current and the q-axis current. This means that when the axis current is controlled, it will affect the axis current, and vice versa. This coupling phenomenon makes current control complicated, reducing the control accuracy and the dynamic response performance of the system. For example, when adjusting the active power (related to the d-axis current), it may cause fluctuations in reactive power (related to the q-axis current), affecting the power factor and power quality of the power grid. Therefore, decoupling control is required to make the control of the d-axis and q-axis currents independent of each other to achieve more accurate current control.

[0066] The control method of the DC bus voltage provided by the embodiment of the present invention is achieved by adding adaptive virtual capacitor parameter control according to the DC bus voltage change rate on the basis of the voltage and current dual closed-loop control method of the rectifier. When the absolute value of the change in the actual value of the DC bus voltage is greater than the set threshold, the adaptive virtual capacitor control is added. When the absolute value of the change in the actual value of the DC bus voltage increases, the capacitor is adaptively adjusted to increase, thereby improving the inertia capacity of the DC system and suppressing further deterioration of the voltage; when the absolute value of the change in the actual value of the DC bus voltage decreases, the virtual capacitor is adaptively adjusted to decrease, thereby reducing inertia and shortening the voltage recovery time. The substation adopting the proposed adaptive virtual capacitor control method can realize rapid and stable control of the substation bus voltage, can quickly smooth out rapid disturbances in the source, load and storage of the substation, and realize friendly interaction between the substation and the power grid.

[0067] Optionally, the adaptive virtual capacitance transfer function H ce (s) is:

[0068]

[0069] Among them, m1 and m2 are reference thresholds, is the rate of change of the actual value of the DC bus voltage, U s To set the threshold, ΔU dc is the actual value change of DC bus voltage.

[0070] Figure 4 The present invention provides a control block diagram of the actual value of a DC bus voltage. Figure 5 FIG. 1 is a flow chart of another method for controlling a DC bus voltage provided by an embodiment of the present invention. Figure 4 and Figure 5 The step of performing current loop decoupling control on the current deviation value to obtain a driving signal of the rectifier includes:

[0071] S201, sending the current deviation value to the current loop controller, and obtaining the d-axis voltage reference value and q-axis voltage reference value of the rectifier in the synchronous rotating coordinate system after the output of the current loop controller is subjected to cross-coupling compensation of the d-axis current and the q-axis current and voltage feedforward compensation.

[0072] First, a mathematical model of the three-phase rectifier in a two-phase rotating coordinate system (dq coordinate system) is established to analyze the coupling relationship between the d-axis and the q-axis. By analyzing the circuit principle and electromagnetic relationship, the d-axis voltage equation is obtained:

[0073] And the q-axis voltage equation:

[0074] Among them, v d 、v q is the voltage in the dq coordinate system, L f is the filter inductor, R is the resistance, ω is the grid angular frequency, e d 、e q is the component of the grid electromotive force in the dq coordinate system. From these equations, it can be seen that the d-axis current and the q-axis current are connected through the cross term ωL f i q and ωL f i d Mutual coupling.

[0075] In order to eliminate this coupling, a decoupling compensation term is introduced. For d-axis current control, ωLi is added to the d-axis voltage equation q The compensation term makes the shaft voltage equation become Thus, the influence of the q-axis current on the q-axis current is eliminated; similarly, for the q-axis current control, ωL is added to the q-axis voltage equation f i d The compensation term is The influence of the d-axis current on the q-axis current is eliminated, thus achieving the decoupling of the d-axis and q-axis currents.

[0076] The d-axis current deviation value Δi calculated previously d and q-axis current deviation Δi q The current loop controller can use PI (proportional integral) controller or other advanced control algorithms. The transfer function of the current loop controller is H i (s).

[0077] The current loop controller is based on the d-axis current deviation value Δi d , the proportional link output u of the PI controller pd =K pd Δi d (where K pdis the d-axis proportional coefficient), the integral link outputs u id =K id ∫Δi d dt(where K id is the d-axis integral coefficient), the total d-axis control amount u d =u pd +u id This control quantity is used to adjust the d-axis voltage to reduce the d-axis current deviation.

[0078] Similarly, the current loop controller is based on the q-axis current deviation value Δi q , calculate the q-axis control amount u q =u pq +u iq (where u pq =K pq Δi q is the output of the q-axis proportional link, K pq is the q-axis proportional coefficient; u iq =K iq ∫Δi q dt is the output of the q-axis integral link, K iq is the axis integral coefficient), which is used to adjust the q-axis voltage and reduce the q-axis current deviation.

[0079] The calculated d-axis and q-axis control quantities u d and u q Based on the cross-coupling compensation term (i.e. ωL f i q and ωL f i d ) and voltage feedforward compensation term (based on the grid electromotive force e d and e q Compensation is performed to improve the system's response speed to grid voltage changes) to obtain the final d-axis voltage reference value v dref and q-axis voltage reference value v qref .

[0080] S202, converting the d-axis voltage reference value and the q-axis voltage reference value of the rectifier in the synchronous rotating coordinate system into an output voltage reference value of the rectifier and then using it as a modulation wave after amplitude limiting.

[0081] The obtained d-axis voltage reference value v dref and q-axis voltage reference value v qref Converted into the voltage reference value v in the three-phase stationary coordinate system through coordinate transformation (such as inverse Park transformation) ref The voltage reference value is then limited to ensure that it is within the voltage range allowed by the rectifier power switch device to prevent overvoltage from damaging the device.

[0082] S203, comparing the modulation wave with the triangular carrier wave, and controlling the on and off of the power switch device at the intersection of the modulation wave and the triangular carrier wave to obtain a driving signal for the switch tube of the rectifier.

[0083] Compare the limited three-phase voltage reference value with the triangular carrier signal. When the voltage reference value is greater than the triangular carrier signal, the corresponding power switch device is turned on; when the voltage reference value is less than the triangular carrier signal, the power switch device is turned off. In this way, the drive signal of the rectifier switch tube is generated to control the on and off of the rectifier power switch device, thereby realizing the control of the AC side input current, making the actual current track the reference current, and achieving the purpose of stabilizing the DC bus voltage and regulating the active and reactive power.

[0084] The present invention builds a substation example based on the MATLAB experimental simulation platform to verify the correctness and effectiveness of the DC bus voltage control method.

[0085] In the example simulation, the rectifiers that interact with the substation and the power grid adopt the DC bus voltage control method provided by the embodiment of the present invention to realize the interactive operation of the substation and the power grid, and maintain the DC bus voltage of the substation stable at 750V. Set the substation to connect to a 30kW DC load at the initial moment, and the power grid supplies power to the DC load; at 1s, the DC load is suddenly increased to 55kw to observe the impact of the power mutation on the operation of the substation; at 2s, simulate the photovoltaic access of the substation, and the photovoltaic power of the substation is used to supply power to the substation load first, and the insufficient part is supplied by the power grid.

[0086] Figure 6 It is the bus voltage fluctuation curve of the substation. Figure 6 The horizontal axis represents time (Time), in seconds (s), and the vertical axis represents the DC bus voltage (Voltage-dc), in volts (V). The black curve represents the DC bus voltage waveform of the substation rectifier using the traditional constant voltage PI control method, and the red curve represents the DC bus voltage waveform of the substation using the proposed adaptive virtual capacitor control method. Figure 6 It can be concluded that the DC bus voltage control method provided in the embodiment of the present invention can control the stability of the substation bus voltage. When the operating conditions change, such as a sudden increase in substation power and sudden access to photovoltaic power in the substation, the DC bus voltage fluctuation is significantly reduced compared with the traditional control method, and the bus voltage fluctuation is controlled within 2%. Moreover, when the substation operating conditions suddenly change, the bus voltage regulation time is significantly reduced, and rapid and stable control of the DC bus voltage can be achieved.

[0087] Figure 7 It is the active power waveform diagram of the interaction between the substation and the power grid. The power flowing from the grid into the substation is a positive value. Figure 7The horizontal axis represents time (Time), in seconds (s), and the vertical axis represents active power (Power), in watts (W). The black curve represents the substation grid interactive rectifier using the traditional constant voltage PI control method, and the red curve represents the adaptive virtual capacitor control method provided by the embodiment of the present invention.

[0088] according to Figure 7 It can be concluded that after adopting the control method provided in the embodiment of the present invention, when the load of the substation suddenly increases, the power fluctuation is significantly reduced, the adjustment time is shortened, and the rapid disturbance of the source, load and storage of the substation can be quickly smoothed out, the impact on the power of the substation is reduced, and the rapid and stable adjustment of the power of the substation can be achieved.

[0089] Figure 8 It is the single-phase voltage waveform on the grid side of the substation. Figure 8 The horizontal axis represents time (Time), the unit is second (s), and the vertical axis represents the single-phase voltage on the grid side (Voltage-grid), the unit is volt (V). Fig. 9 It is the waveform of the d-axis grid-connected current of the substation. Fig. 9 The horizontal axis represents time (Time), the unit is seconds (s), and the vertical axis represents the d-axis grid-connected current (Current-grid), the unit is ampere (A). Figure 8 and Fig. 9 It can be observed from the voltage and current waveforms shown that the substation adopting the control method provided in the embodiment of the present invention can be stably connected to the grid and operate without distortion of the grid-connected voltage waveform. When the substation operation scenario suddenly changes, the impact on the grid is significantly reduced, which verifies that the proposed control method can not only realize fast and stable control inside the substation, but also realize friendly interaction with the grid.

[0090] In summary, the substation adopting the bus voltage control method provided by the present invention can realize fast and stable control of the substation bus voltage. Compared with the traditional constant voltage PI control method, when the substation operation scene suddenly changes, the substation bus voltage and power fluctuations are significantly reduced, the system adjustment time is reduced, and the rapid disturbance of the substation source, load and storage can be quickly smoothed. The power impact on the connected grid side is significantly reduced, and friendly interaction with the grid can be achieved.

[0091] The present invention proposes a control method for DC bus voltage based on a rectifier that interacts with the power grid in a substation, by adding adaptive virtual capacitor parameter control according to the DC bus voltage fluctuation rate based on the voltage and current double closed-loop control method of the rectifier. When the absolute value of the change in the actual value of the DC bus voltage is higher than the set threshold, the adaptive virtual capacitor control is added, and when the rate of change of the actual value of the DC bus voltage increases, the capacitor is adaptively adjusted to increase, thereby improving the inertia capacity of the DC system and suppressing further deterioration of the voltage; when the rate of change of the actual value of the DC bus voltage decreases, the virtual capacitor is adaptively adjusted to decrease, reduce inertia, and shorten the voltage recovery time.

[0092] Based on the same inventive concept, an embodiment of the present invention further provides a control system for a DC bus voltage. Fig.10 Schematic diagram of the structure of the control system of the DC bus voltage provided by the embodiment of the present invention. Fig.10 As shown, the control system 1 of the DC bus voltage includes:

[0093] The acquisition module 10 is used to acquire the actual value of the DC bus voltage, the reference value of the DC bus voltage and the AC side output current of the rectifier; the transformation module 20 is used to perform dq transformation on the AC side output current according to the phase output value of the phase-locked loop to determine the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system; the current deviation value determination module 30 is used to determine the first voltage according to the DC bus voltage reference value, the DC bus voltage actual value, and the voltage loop proportional integral transfer function; when the absolute value of the change amount of the DC bus voltage actual value is greater than the set threshold, the adaptive virtual capacitor transfer function is determined according to the change rate of the DC bus voltage actual value and the reference threshold; the second voltage is determined according to the DC bus voltage reference value, the DC bus voltage actual value and the adaptive virtual capacitor transfer function; the d-axis current reference value of the AC side output current in the two-phase rotating coordinate system is determined according to the first voltage and the second voltage; the current deviation value is calculated according to the d-axis current reference value and the d-axis current of the AC side output current in the two-phase rotating coordinate system; the control module 40 is used to perform current loop decoupling control on the current deviation value to obtain the driving signal of the rectifier.

[0094] It can be understood that the similarities between the control system of the DC bus voltage and the control method of the DC bus voltage can be referred to the description of the control method of the DC bus voltage, which will not be repeated here.

[0095] Fig.11: is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0096] like Fig.11 As shown, the electronic device 10 includes at least one processor 11, and a memory connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., wherein the memory stores a computer program that can be executed by at least one processor, and the processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 to the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0097] A number of components in the electronic device 10 are connected to the I / O interface 15, including: an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a disk, an optical disk, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0098] The processor 11 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 executes the various methods and processes described above, such as a method for controlling the DC bus voltage.

[0099] In some embodiments, the control method of the DC bus voltage may be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as a storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the control method of the DC bus voltage described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to execute the control method of the DC bus voltage in any other appropriate manner (e.g., by means of firmware).

[0100] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0101] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer program is executed by the processor, the functions / operations specified in the flow chart and / or block diagram are implemented. The computer program may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0102] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in combination with an instruction execution system, device or equipment. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0103] To provide interaction with a user, the systems and techniques described herein may be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or trackball) through which the user can provide input to the electronic device. Other types of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form (including acoustic input, voice input, or tactile input).

[0104] The systems and techniques described herein may be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0105] A computing system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The client and server relationship is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services.

[0106] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0107] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling a DC bus voltage, characterized in that: include: Obtain the actual value of the DC bus voltage, the reference value of the DC bus voltage and the AC side output current of the rectifier; Performing a dq transformation on the AC side output current according to the phase difference of the phase-locked loop output to determine the d-axis current and the q-axis current of the AC side output current in a two-phase rotating coordinate system; Determine a first voltage according to the DC bus voltage reference value, the DC bus voltage actual value, and a voltage loop proportional-integral transfer function; When the absolute value of the change in the actual value of the DC bus voltage is greater than a set threshold, determining an adaptive virtual capacitor transfer function according to a change rate of the actual value of the DC bus voltage and a reference threshold; Determine a second voltage according to the DC bus voltage reference value, the DC bus voltage actual value and the adaptive virtual capacitor transfer function; Determine a d-axis current reference value of the AC side output current in a two-phase rotating coordinate system according to the first voltage and the second voltage; Calculate the current deviation value according to the d-axis current reference value, the q-axis current reference value, and the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system; The current deviation value is subjected to current loop decoupling control to obtain a driving signal for the rectifier.

2. The method for controlling the DC bus voltage according to claim 1, characterized in that: The adaptive virtual capacitance transfer function H ce (s) is: Among them, m1 and m2 are reference thresholds, is the rate of change of the actual value of the DC bus voltage, U s To set the threshold, ΔU dc is the actual value change of DC bus voltage.

3. The method for controlling the DC bus voltage according to claim 1, characterized in that: The step of determining the first voltage according to the DC bus voltage reference value, the DC bus voltage actual value, and the proportional-integral transfer function comprises: The first voltage u1(s) is determined according to the following formula: u1(s)=(U dcref -U dc )H V (S); H V (s)=k p_V +k i_V / s; Among them, k p_V Represents the proportional coefficient of the voltage loop proportional-integral transfer function, k i_V represents the integral coefficient of the voltage loop proportional-integral transfer function, s represents the Laplace transform factor, U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H V (s) represents the voltage loop proportional-integral transfer function.

4. The method for controlling the DC bus voltage according to claim 1, characterized in that: The step of determining the second voltage according to the DC bus voltage reference value, the DC bus voltage actual value and the adaptive virtual capacitor transfer function comprises: The second voltage u2(s) is determined according to the following formula: u2(s)=(U dcref -U dc )H ce (s); Among them, U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H ce (s) represents the adaptive virtual capacitor transfer function.

5. The method for controlling the DC bus voltage according to claim 1, characterized in that: The step of determining a d-axis current reference value of the AC side output current in a two-phase rotating coordinate system according to the first voltage and the second voltage comprises: Determine the reference current i according to the following formula dref : i dref =u1(s)+u2(s)=(U dcref -U dc )(H V (s)+H ce (s); Where, u1(s) represents the first voltage, u2(s) represents the second voltage, and U dcref Indicates the DC bus voltage reference value, U dc Indicates the actual value of the DC bus voltage, H V (s) represents the voltage loop proportional-integral transfer function, H ce (s) represents the adaptive virtual capacitor transfer function.

6. The method for controlling the DC bus voltage according to claim 1, characterized in that: The step of performing dq conversion on the AC side output current according to the phase-locked loop output phase difference comprises: The AC side output current is converted into dq according to the following formula: Among them, i a 、i b 、i c is the AC side output current, i d 、i q They respectively represent the d-axis current and q-axis current of the AC side output current in the two-phase rotating coordinate system, and θ represents the phase difference of the phase-locked loop output.

7. The method for controlling the DC bus voltage according to claim 1, characterized in that: The step of performing current loop decoupling control on the current deviation value to obtain the driving signal of the rectifier comprises: The current deviation value is sent to a current loop controller, and the output of the current loop controller is subjected to cross-coupling compensation of d-axis current and q-axis current and voltage feedforward compensation to obtain a d-axis voltage reference value and a q-axis voltage reference value of the rectifier in a synchronous rotating coordinate system; Converting the d-axis voltage reference value and the q-axis voltage reference value of the rectifier in the synchronous rotating coordinate system into the output voltage reference value of the rectifier and then limiting it as a modulation wave; The modulation wave is compared with the triangular carrier wave, and the on and off of the power switch device is controlled at the intersection point of the modulation wave and the triangular carrier wave to obtain the driving signal of the switch tube of the rectifier.

8. A control system for DC bus voltage, characterized in that: include: An acquisition module is used to acquire the actual value of the DC bus voltage, the reference value of the DC bus voltage and the AC side output current of the rectifier; A transformation module, used for performing a dq transformation on the AC side output current according to the phase difference of the phase-locked loop output, so as to determine the d-axis current and the q-axis current of the AC side output current in a two-phase rotating coordinate system; A current deviation value determination module is used to determine a first voltage according to the DC bus voltage reference value, the DC bus voltage actual value, and a voltage loop proportional-integral transfer function; when the absolute value of the change in the DC bus voltage actual value is greater than a set threshold, determine an adaptive virtual capacitor transfer function according to a rate of change of the DC bus voltage actual value and a reference threshold; determine a second voltage according to the DC bus voltage reference value, the DC bus voltage actual value, and the adaptive virtual capacitor transfer function; determine a d-axis current reference value of the AC side output current in a two-phase rotating coordinate system according to the first voltage and the second voltage; Calculating a current deviation value according to the d-axis current reference value and the d-axis current of the AC side output current in a two-phase rotating coordinate system; A control module is used to perform current loop decoupling control on the current deviation value to obtain a driving signal for the rectifier.

9. An electronic device, characterized in that: include: at least one processor; as well as A memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the method for controlling the DC bus voltage as described in any one of claims 1-7.

10. A computer-readable storage medium storing a program, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the method for controlling the DC bus voltage according to any one of claims 1 to 7 when executed.

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