Rectifier Loss Suppression Method and Apparatus Based on Switching State Pre-selection Strategy

Abstract

This invention provides a rectifier loss suppression method and apparatus based on a switching state pre-selection strategy, comprising the following steps: sampling to obtain the input voltage and current on the grid side and the output voltage on the DC side at time k; predicting the active power and reactive power estimates at time k+2; obtaining the cost function g; outputting a pre-selected voltage space vector according to the switching state pre-selection strategy; traversing the pre-selected voltage space vector, selecting the voltage space vector that minimizes the cost function g, and applying it to the rectifier at time k+1. This invention adds the switching state pre-selection strategy to the existing Model Predictive Direct Power Control (MPDPC) framework, which can effectively reduce the switching losses of the bridge arm with the highest aging degree in the rectifier, achieve special protection for the aging bridge arm, and solve the system lifetime problem caused by uneven aging of the bridge arm.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a rectifier loss suppression method and apparatus based on a switching state preselection strategy. Background Technology

[0002] Three-phase PWM rectifier topologies are commonly used in applications requiring the conversion of AC power to DC power. In renewable energy hydrogen production networks, they can serve as a hydrogen production power source, connecting to the grid and supplying power to the hydrogen electrolyzers.

[0003] Traditional rectifier systems suffer from power loss issues, which not only reduce system efficiency and reliability but also subject power switches to thermal stress, significantly shortening the lifespan of both the power switches and the rectifier. To improve rectifier efficiency, it is essential to reduce power losses generated by the power switches, with switching losses accounting for the majority. Currently, rectifier control schemes commonly employ Model Predictive Control (MPC), which can be broadly categorized into four types: Model Predictive Current Control (MPCC), Model Predictive Virtual Flux Control (MPVFC), Model Predictive Direct Power Control (MPDPC), and Model Predictive Virtual Flux Direct Power Control (MPVFDPC). The difference between these control schemes lies in the controlled variable. The MPCC scheme directly regulates the input current of the active rectifier by using the input current as the control variable. In contrast, the MPVFC method uses a virtual flux linkage of the input voltage, while MPDPC and MPVFDPC technologies regulate the input power.

[0004] Existing model predictive control technology can effectively improve the efficiency and reliability of three-phase active rectifiers, but it fails to take into account that the phase arms of the rectifier may have different degrees of aging. All the switches of the rectifier operate on an average basis during the grid cycle, causing the aging arms to be subjected to the same switching frequency as the healthy arms, which accelerates the damage of the aging switches. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention discloses a rectifier loss suppression method and apparatus based on a switch state pre-selection strategy.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] On the one hand, the present invention aims to provide a rectifier loss suppression method based on a switching state preselection strategy, comprising the following steps:

[0008] S1. Sample to obtain the current Input voltage on the grid side at any time and input current and DC side output voltage ,in , It is a three-phase phase;

[0009] S2. Based on the above Input voltage at time Input current and output voltage ,predict Active power estimate at time and reactive power estimates ;

[0010] S3. Based on the estimated active power... and reactive power estimates Obtain the cost function ,in , for Reference values ​​for active power and reactive power of the system at all times;

[0011] S4. Pre-select strategy based on switch status:

[0012] predict coordinate system The rectifier output voltage reference value is needed at all times. , ;

[0013] By using the Clarke inverse transform, The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ;

[0014] The performance indicators of each phase arm were sampled to determine the arm with the most severe aging.

[0015] Sort the output voltage reference values , , To obtain the maximum value and minimum value ;

[0016] If the reference value of the output voltage of the bridge arm with the most severe aging is not the maximum value. or minimum value Then the output preselected voltage space vector is all 8 voltage space vectors;

[0017] If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. Then the output preselected voltage space vector only includes the vector where the aging bridge arm is at the high position;

[0018] If the output voltage reference value of the bridge arm with the most severe aging is the minimum value Then the output preselected voltage space vector only includes the vector where the aging bridge arm is low-order;

[0019] S5. Traverse the pre-selected voltage space vectors and select the voltage space vector that minimizes the cost function g. and in It is constantly applied to the rectifier.

[0020] Furthermore, in step S2, based on the input voltage Input current and output voltage ,predict Active power estimate at time and reactive power estimates The steps include:

[0021] S21. Using Clarke transform, The input voltage in the coordinate system and input current Convert to Input voltage in coordinate system and input current ,in ;

[0022] S22. Based on the input current and input voltage predict Estimated input current at time t and input voltage estimate ;

[0023] S23. Based on the input voltage estimate and input current estimate ,get coordinate system Active power estimate at time and reactive power estimates .

[0024] Furthermore, in step S22, based on the input current predict Estimated input current at time t The steps include:

[0025] The input current Substitute into the current prediction model to predict Estimated input current at time t ;

[0026] The Estimated input current at time t Substitute into the current prediction model to predict Estimated input current at time t ;

[0027] The current prediction model is as follows:

[0028]

[0029] in, The sampling period is This is the rectifier output voltage. For line resistance, This refers to the line inductance.

[0030] Further, in step S22, based on the input voltage predict Estimated input voltage at time 1 The steps include:

[0031] The input voltage Substitute into the voltage prediction model to predict Estimated input voltage at time 1 ;

[0032] The Estimated input voltage at time 1 Substitute into the voltage prediction model to predict Estimated input voltage at time 1 ;

[0033] The voltage prediction model is as follows:

[0034]

[0035] in, The phase angular velocity of the power grid is tracked and collected in real time by a phase-locked loop (PLL). The sampling period.

[0036] Furthermore, predictions coordinate system The rectifier output voltage reference value is needed at all times. , The steps include:

[0037] predict Reference input current at time 1 , ;

[0038] The reference input current , Substitution Formula for predicting current at time:

[0039] ,

[0040] get coordinate system The rectifier output voltage reference value is needed at all times. , .

[0041] Furthermore, if the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. It also includes the following steps:

[0042] Clamp the upper switch tube of the aged bridge arm to the positive bus P of the DC bus.

[0043] Furthermore, if the reference value of the output voltage of the bridge arm with the most severe aging is the minimum value... It also includes the following steps:

[0044] The lower switch of the aged bridge arm is clamped to the negative bus N of the DC bus.

[0045] A rectifier loss suppression device based on a switching state preselection strategy includes:

[0046] Sampling module: used to sample and obtain the current Input voltage on the grid side at any time and input current and DC side output voltage ,in , It is a three-phase phase;

[0047] Prediction module: used for prediction based on input voltage Input current and output voltage ,predict Active power estimate at time and reactive power estimates ;

[0048] Cost function generation module: based on the estimated active power. and reactive power estimates Obtain the cost function ,in , for Reference values ​​for active power and reactive power of the system at all times;

[0049] Switch state pre-selection module: predicts the switch state based on the switch state pre-selection strategy. coordinate system The rectifier output voltage reference value is needed at all times. , ;

[0050] By using the Clarke inverse transform, The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ;

[0051] The performance indicators of each phase arm were sampled to determine the arm with the most severe aging.

[0052] Sort the output voltage reference values , , To obtain the maximum value and minimum value ;

[0053] If the reference value of the output voltage of the bridge arm with the most severe aging is not the maximum value. or minimum value Then the output preselected voltage space vector is all 8 voltage space vectors;

[0054] If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. Then the output preselected voltage space vector only includes the vector where the aging bridge arm is at the high position;

[0055] If the output voltage reference value of the bridge arm with the most severe aging is the minimum value Then the output preselected voltage space vector only includes the vector where the aging bridge arm is low-order;

[0056] Evaluation module: Traverses the pre-selected voltage space vectors and selects the voltage space vector that minimizes the cost function g. and in It is constantly applied to the rectifier.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention adds a switching state pre-selection strategy to the existing model predictive direct power control (MPDPC) framework, which can effectively reduce the switching losses of the bridge arm with the highest aging degree in the rectifier, realize special protection for the aging bridge arm, and solve the system life problem caused by uneven aging of the bridge arm. Attached Figure Description

[0058] Figure 1 A schematic diagram of the topology of the three-phase PWM rectifier of the present invention is shown;

[0059] Figure 2 This invention illustrates the three-phase PWM rectifier in... The equivalent space voltage vector distribution diagram output in the coordinate system;

[0060] Figure 3 The control block diagram of conventional Model Predictive Direct Power Control (MPDPC) is shown;

[0061] Figure 4 A control block diagram of a rectifier based on a switch state preselection strategy according to the present invention is shown;

[0062] Figure 5 A flowchart of a rectifier loss suppression method based on a switch state preselection strategy according to the present invention is shown;

[0063] Figure 6 A flowchart of the switch state preselection strategy of the present invention is shown;

[0064] Figure 7 A structural block diagram of a rectifier loss suppression device based on a switch state preselection strategy according to the present invention is shown.

[0065] Figure 8 The diagram showing the correspondence between the switching state, voltage space vector, equivalent voltage space vector, and amplitude of the present invention is illustrated.

[0066] Figure 9 The diagram shows the correspondence between the aging bridge arm, conditions, clamping switch tube, and preselected voltage space vector of the present invention. Detailed Implementation

[0067] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0069] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0070] like Figure 1 As shown, the three-phase PWM rectifier of this invention mainly consists of the following parts: a symmetrical three-phase voltage source. , , Inductance of power grid side lines and line resistance And a three-phase bridge arm consisting of six IGBT power switching transistors, each phase bridge arm ( , , The phase consists of two IGBT power switches connected in series, and the two IGBT power switches strictly adopt a high-frequency complementary conduction control method, that is, when one switch is on, the other switch must be off. For example, Phase bridge arm is connected by upper switch tube and the next switching transistor Series configuration, when the switching transistor is connected. When turned on, the lower switching transistor This is to prevent the DC bus (positive bus) from being shut off. With negative busbar A shoot-through short circuit can form between the upper and lower switching transistors of the same phase arm, damaging the IGBT power switching device. It is understandable that each phase arm ( , , The switching state of a phase is a single-degree-of-freedom binary variable, that is, the switching state of each phase arm ( , , The phase has two switching states, represented by 0 (low bit) and 1 (high bit). Specifically, When, it means upper switch tube of phase bridge arm Turn on, switch off Turn off, at this time The phase AC terminal potential is forcibly fixed at the positive busbar. Current via the upper switch tube Flow to positive bus ; When, it means Lower switch tube of phase bridge arm On / off switch Turn off, at this time The phase AC terminal potential is forcibly fixed at the negative busbar. Current via the next switching transistor The current flows to the negative busbar. It should be noted here that: due to the three-phase bridge arm ( , , The switching states of the phases are independent of each other, and the rectifier has a total of Possible combinations of switch states Combining Figure 8 As shown, these 8 switching state combinations correspond to 8 discrete voltage space vectors. This includes 6 pairs with equal amplitude and different directions. effective vector and two zero vectors with zero magnitude The Clarke transformation formula can be used to transform three-phase quantities. Transform into two phasors , and thus The eight switch states in the coordinate system are mapped to Output in coordinate system Figure 2 The equivalent voltage space vector distribution diagram is shown. By transforming the coordinates, the three-phase AC quantities are converted into two-phase DC quantities for control, which greatly simplifies the control complexity and retains all amplitude / phase information without redundant dimensions.

[0071] To better illustrate the improvements of this invention, the working principle of traditional Model Predictive Direct Power Control (MPDPC) will first be explained in detail. Specifically, in conjunction with... Figure 3 As shown, For each phase input current on the grid side, For each phase input voltage on the grid side, for Any one of the three phases; This is the DC-side output voltage.

[0072] Among them, input current The dynamic expression is as follows:

[0073] (1)

[0074] In equation (1), It is the rectifier output voltage. Depend on The switching status of the three-phase bridge arms and the output voltage on the DC side The decision is as follows:

[0075] (2)

[0076] In formula (2) , and This refers to the switching state of the upper switching transistor in a set of switching transistors connected to each phase of the power supply. When When the upper switch is on, the lower switch is off; when When the upper switch is off, the lower switch is on. for Any one of the three phases.

[0077] In addition, the input current per phase in equation (1) and input voltage per phase The Clarke transform can be used to... Transformation of three-phase variables in coordinate system Two-phase variables in a coordinate system, The input voltage and input current in the coordinate system are expressed as follows:

[0078] (3)

[0079] In equation (3), for Either of the two phases can then be used to obtain the following: The vector expression of equation (1) in the coordinate system is as follows:

[0080] (4)

[0081] To control the three-phase PWM rectifier, the continuous differential equation shown in equation (4) needs to be discretized using the forward Euler method, with a sampling period of . As shown below, the final result can be simplified to: The formula for predicting discrete-time input current in a coordinate system is used to predict... Estimated input current at time:

[0082] (5)

[0083] To ensure the real-time control performance of the MPDPC method in practical applications, delay compensation is required. That is, based on equation (5), a further forward prediction is performed to obtain... Estimated input current at time:

[0084] (6)

[0085] Furthermore, sensors can acquire... Input voltage on the grid side at any time :

[0086] (7)

[0087] Taking advantage of the constant frequency characteristic of the power grid, a rotating matrix can be used for prediction. The vector position of the grid voltage at any given time is shown below:

[0088] (8)

[0089] In equation (8), the grid phase angular velocity Provided by real-time tracking via a phase-locked loop (PLL). Similarly, further predictions can be made. The vector position of the grid voltage at time t is shown below:

[0090] (9)

[0091] From equations (6) and (9), we can obtain coordinate system Estimated input voltage at time 1 and input current estimate Therefore, it is possible to calculate coordinate system Active power estimate at time and reactive power estimates As shown below:

[0092] (10)

[0093] Cost function It is the core decision basis of Model Predictive Direct Power Control (MPDPC), used to quantify the total loss (switching loss + conduction loss) generated after selecting a certain combination of switching states. By quantifying and evaluating the total loss of each switching state, multi-objective optimization is achieved. The cost function can be obtained according to equation (10). The expression is as follows:

[0094] (11)

[0095] In equation (11), and For the system The active power reference value and reactive power reference value input at any time can be used to analyze the system using equation (10). Active power reference value input at all times and reactive power reference value This is obtained through secondary prediction. Among them, the active power reference value... The output voltage is provided by the outer loop PI controller of the DC voltage, which is used to dynamically adjust and maintain the DC side output voltage. Stability. Reactive power reference value. In industrial applications, the power factor needs to be set to 0.

[0096] Under the traditional Model Predictive Direct Power Control (MPDPC) method, the cost function is obtained. Then, it is necessary to iterate through the... arrive All eight voltage space vectors are selected to make the cost function Minimize a voltage space vector and in The control is applied to the rectifier at all times to achieve global optimal control. Existing models predict that direct power control (MPDPC) can effectively improve the efficiency and reliability of three-phase active rectifiers, but they fail to take into account that the phase arms of the rectifier may have different degrees of aging, and use all arms indiscriminately.

[0097] The bridge arms of a three-phase PWM rectifier may have different degrees of aging due to factors such as manufacturing process, uneven thermal stress distribution, and replacement during maintenance. Therefore, the lifespan of each bridge arm may vary. If any phase bridge arm fails, the entire active rectifier will stop working, making it crucial to extend the lifespan of the most severely aged bridge arm. This invention proposes a loss suppression method for three-phase PWM rectifiers based on a switch state preselection strategy, combined with... Figure 4 As shown, a switching state pre-selection strategy is added to the existing Model Predictive Direct Power Control (MPDPC) framework. This differs from the traditional MPDPC method which traverses all eight voltage space vectors and selects the state that minimizes the cost function. The smallest voltage space vector The method for suppressing losses in a three-phase PWM rectifier proposed in this invention pre-selects a pre-selection set of voltage space vectors through a switching state pre-selection strategy. When calculating the cost function g, it traverses the pre-selected voltage space vectors and selects the one that minimizes the cost function. Minimize a voltage space vector and in It is constantly applied to the rectifier.

[0098] Specifically, in combination Figure 5 As shown, the present invention provides a method for suppressing losses in a three-phase PWM rectifier based on a switch state pre-selection strategy, comprising the following steps:

[0099] S1. Sample to obtain the current time ( (Time) Input voltage on the grid side and input current and DC side output voltage ,in ;

[0100] S2. Based on the above Input voltage at time Input current and output voltage ,predict Active power estimate at time and reactive power estimates ;

[0101] S3. Based on the estimated active power... and reactive power estimates Obtain the cost function The , for Reference values ​​for active power and reactive power of the system at all times;

[0102] S4. Pre-selection strategy based on switch state: Prediction coordinate system The rectifier output voltage reference value is needed at all times. , , The bridge arm with the most severe aging is identified, and a pre-selected voltage space vector is output based on the output voltage reference value of that bridge arm.

[0103] S5. Traverse the pre-selected voltage space vectors and select the one that makes the cost function... The smallest voltage space vector and in It is constantly applied to the rectifier.

[0104] In step S1 above, the input voltage and input current and DC side output voltage Data can be collected in real time using sensors.

[0105] In step S2 above, the first step is to use the Clarke transform to... The input voltage in the coordinate system and input current Convert to Input voltage in coordinate system and input current ,in for Either of the two phases; then based on Input current in coordinate system and input voltage predict Estimated input current at time t and input voltage estimate Therefore, the estimated value can be predicted based on the input voltage. and input current estimate You can get coordinate system Active power estimate at time and reactive power estimates Among them, based on input current predict Estimated input current at time t The current prediction model, and the current prediction model based on input voltage. Predicted voltage estimate The implementation principle of the voltage prediction model has been explained in detail above, and will not be repeated here.

[0106] In step S3 above, the cost function Its function is to guide the rectifier in selecting the optimal voltage space vector, in which the active power prediction value is included. and reactive power estimates It is a system The actual power that can be achieved at any given time; active power reference value. and reactive power reference value It is a system The target value that is expected to be achieved at all times.

[0107] In step S4 above, the prediction is made based on the switch state pre-selection strategy. coordinate system The rectifier output voltage reference value is needed at all times. , , The steps of identifying the bridge arm with the most severe aging and outputting a pre-selected voltage space vector based on the output voltage reference value of that bridge arm include:

[0108] S41. Prediction The rectifier output voltage reference value is needed at all times. , ;

[0109] S42. By using the Clarke inverse transform, The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ;

[0110] S43. Sample the performance indicators of each phase arm. According to the performance indicators Identify the bridge arm with the most severe aging.

[0111] S44. Sort the output voltage reference values , , To obtain the maximum value and minimum value ;

[0112] S45. Output the preselected voltage space vector based on the output voltage reference value of the bridge arm with the most severe aging.

[0113] In step S41 above, the output voltage reference value , Based on Reference input current at time 1 , The solution was obtained here, firstly for Reference input current at time 1 , The implementation principle will be explained as follows:

[0114] exist Instantaneous active power in coordinate system and instantaneous reactive power Defined as:

[0115] (12)

[0116] Solving equation (12) yields the current components:

[0117] (13)

[0118] Then, the grid voltage amplitude was used. Scaling (the peak phase voltage), according to the orthogonality invariance of the Clarke transform, we have:

[0119] (14)

[0120] Simplify equation (13) and predict forward. At that moment, we received coordinate system Reference input current at time:

[0121] (15)

[0122] The root cause of current variation in a three-phase PWM rectifier lies in the applied voltage difference, i.e., the essential function of equation (4). Therefore, if the current is required to be within the range of... Reaching the reference value at all times A precise voltage must be applied. To drive the current close to the reference value. To compensate for the execution delay, calculations are needed. coordinate system The rectifier output voltage applied at any time This causes the current to flow in Reaching the reference value at all times .Will Substituting into the left side of equation (6), the rectifier output voltage can be obtained by inverse solution. exist Expression in coordinate system:

[0123] (16)

[0124] In step S42 above, the Clarke inverse transform can be used to... coordinate system rectifier output voltage at time and Transform back Output voltage of each phase rectifier in the coordinate system , , :

[0125] (17)

[0126] In step S43 above, we obtain coordinate system After determining the output voltage of each phase rectifier at each moment, sort them from high to low:

[0127] (18)

[0128] In step S44 above, specific parameters of the power switching device (such as temperature, collector-emitter on-state voltage) are typically monitored. Threshold voltage (etc.) to determine the bridge arm with the most severe aging, which will not be described in detail here.

[0129] In step S45 above, it will be determined whether the bridge arm with the most severe aging is the maximum value among the three phases. ) or minimum value ( ), output different rectifier preselected voltage space vectors, if the bridge arm with the most severe aging is not the maximum value among the three phases ( ) or minimum value ( If the output preselected voltage space vectors are all 8 space voltage vectors, then, like the traditional MPDPC method, all space voltage vectors will be traversed when calculating the cost function g. If the bridge arm with the most severe aging is the maximum value among the three phases ( ) or minimum value ( If the voltage space vector that would cause the bridge arm with the most severe aging to switch state at the next sampling time is excluded, the remaining four voltage space vectors are output as pre-selected voltage space vectors, and the bridge arm with the most severe aging is clamped to the positive DC bus P (maximum value). (time) or parent line Q (minimum value ( (When) to prevent the bridge arm from changing its switching state, it greatly reduces the switching loss of the bridge arm with the highest degree of aging, and at the same time makes the output voltage close to the ideal output voltage waveform without significant loss in performance.

[0130] Specifically, in combination Figure 6 , Figure 9 As shown, for a given bridge arm with the most severe aging (such as...) (phase), in a complete power grid cycle Internally, because the three-phase sinusoidal voltages are mutually... ,therefore The predicted reference voltage of the phase bridge arm will have The time is at its maximum ( ),have The time is in the minimum state ( ), remaining The time is in the middle ( ).when Phase bridge arm in The predicted reference voltage at time t is the predicted reference voltage in the three phases. The maximum value ( ) or minimum value ( When ), you can actively The phase bridge arm is clamped to the positive busbar P (at maximum value) or the negative busbar Q (at minimum value) of the DC busbar. Specifically, when At that time, Phase bridge arm switch tube The positive bus N clamped to the DC bus, i.e. upper switch tube of phase bridge arm Continuous conduction, lower switching transistor Continuous shutdown ), and output the preselected voltage space vector containing vector ( , , , );when( When ), Lower switch tube of phase bridge arm Clamped to the DC bus negative bus N, i.e. Lower switch tube of phase bridge arm Continuous conduction, upper switching transistor Continuous shutdown ), and output the preselected voltage space vector containing vector ( , , , ).

[0131] The pre-selection strategy for switching states proposed in this invention ensures that the switching action of the most severely aged bridge arm should occur during this period. Within the region, by forcing its switching state to remain unchanged, the switching losses caused by the switching action in this region are completely eliminated without significantly deteriorating the overall performance, greatly reducing the thermal stress of the aging bridge arm and extending the rectifier life.

[0132] At the same prediction time, the predicted reference rectifier voltage of the aging bridge arm is at the middle value of the three phases. If the predicted voltage is at an intermediate value, then no clamping operation is performed on that bridge arm, and all 8 space voltage vectors should be traversed when calculating the cost function g. The reason is that if the phase is forcibly clamped when the predicted voltage is at an intermediate value, the rectifier output voltage vector will be unable to reach its required target position, which may lead to control failure, causing the rectifier to enter a non-ideal overmodulation operating region with increased output current distortion or even controller instability.

[0133] Combination Figure 7 As shown, the present invention provides a rectifier loss suppression device based on a switching state preselection strategy, comprising:

[0134] Sampling module: used to sample and obtain the current time ( (Time) Input voltage on the grid side and input current and DC side output voltage ,in , It is a three-phase phase;

[0135] Prediction module: used for prediction based on the above Input voltage at time Input current and output voltage ,predict Active power estimate at time and reactive power estimates ;

[0136] Cost function generation module: based on the estimated active power. and reactive power estimates Obtain the cost function The , for Reference values ​​for active power and reactive power of the system at all times;

[0137] Switch state pre-selection module: Based on the switch state pre-selection strategy, it uses Clarke inverse transform to... The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ;

[0138] The performance indicators of each phase arm were sampled to determine the arm with the most severe aging.

[0139] Sort the output voltage reference values , , To obtain the maximum value and minimum value ;

[0140] If the reference value of the output voltage of the bridge arm with the most severe aging is not the maximum value. or minimum value Then the output preselected voltage space vector is all 8 voltage space vectors;

[0141] If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. Then the output preselected voltage space vector only includes the vector where the aging bridge arm is at the high position;

[0142] If the output voltage reference value of the bridge arm with the most severe aging is the minimum value Then the output preselected voltage space vector only includes the vector where the aging bridge arm is low-order;

[0143] Evaluation module: Traverses the pre-selected voltage space vectors and selects the voltage space vector that minimizes the cost function g. and in It is constantly applied to the rectifier.

[0144] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A rectifier loss suppression method based on a switching state pre-selection strategy, characterized in that, Includes the following steps: S1. Sample to obtain the current Input voltage on the grid side at any time Input current and DC side output voltage ,in , It is a three-phase phase; S2. Based on the above Input voltage at time Input current and output voltage ,predict Active power estimate at time and reactive power estimates ; S3. Based on the estimated active power... and reactive power estimates Obtain the cost function ,in , for Reference values ​​for active power and reactive power of the system at all times; S4. Pre-select strategy based on switch status: predict coordinate system The rectifier output voltage reference value is needed at all times. , ; By using the Clarke inverse transform, The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ; The performance indicators of each phase arm were sampled to determine the arm with the most severe aging. Sort the output voltage reference values , , To obtain the maximum value and minimum value ; If the reference value of the output voltage of the bridge arm with the most severe aging is not the maximum value. or minimum value Then the output preselected voltage space vector is all 8 voltage space vectors; If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. Then the output preselected voltage space vector only includes the vector where the aging bridge arm is at the high position; If the output voltage reference value of the bridge arm with the most severe aging is the minimum value Then the output preselected voltage space vector only includes the vector where the aging bridge arm is low-order; S5. Traverse the pre-selected voltage space vectors and select the voltage space vector that minimizes the cost function g. and in It is constantly applied to the rectifier.

2. The rectifier loss suppression method according to claim 1, characterized in that, In step S2, based on the input voltage Input current and output voltage ,predict Active power estimate at time and reactive power estimates The steps include: S21. Using Clarke transform, The input voltage in the coordinate system and input current Convert to Input voltage in coordinate system and input current ,in ; S22. Based on the input current and input voltage predict Estimated input current at time t and input voltage estimate ; S23. Based on the input voltage estimate and input current estimate ,get coordinate system Active power estimate at time and reactive power estimates .

3. The rectifier loss suppression method according to claim 2, characterized in that, In step S22, based on the input current predict Estimated input current at time t The steps include: The input current Substitute into the current prediction model to predict Estimated input current at time t ; The Estimated input current at time t Substitute into the current prediction model to predict Estimated input current at time t ; The current prediction model is as follows: in, The sampling period is This is the rectifier output voltage. For line resistance, This refers to the line inductance.

4. The rectifier loss suppression method according to claim 2, characterized in that, In step S22, based on the input voltage predict Estimated input voltage at time 1 The steps include: The input voltage Substitute into the voltage prediction model to predict Estimated input voltage at time 1 ; The Estimated input voltage at time 1 Substitute into the voltage prediction model to predict Estimated input voltage at time 1 ; The voltage prediction model is as follows: in, The phase angular velocity of the power grid is tracked and collected in real time by a phase-locked loop (PLL). The sampling period.

5. The rectifier loss suppression method according to claim 1, characterized in that, The prediction coordinate system The rectifier output voltage reference value is needed at all times. , The steps include: predict Reference input current at time 1 , ; The reference input current , Substitution Current prediction model at time: get coordinate system The rectifier output voltage reference value is needed at all times. , .

6. The rectifier loss suppression method according to claim 1, characterized in that, If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. It also includes the following steps: Clamp the upper switch tube of the aged bridge arm to the positive bus P of the DC bus.

7. The rectifier loss suppression method according to claim 1, characterized in that, If the output voltage reference value of the bridge arm with the most severe aging is the minimum value It also includes the following steps: The lower switch of the aged bridge arm is clamped to the negative bus N of the DC bus.

8. A rectifier loss suppression device based on a switching state pre-selection strategy, characterized in that, include: Sampling module: used to sample and obtain the current Input voltage on the grid side at any time and input current and DC side output voltage ,in , It is a three-phase phase; Prediction module: used for prediction based on the above Input voltage at time Input current and output voltage ,predict Active power estimate at time and reactive power estimates ; Cost function generation module: based on the estimated active power. and reactive power estimates Obtain the cost function ,in , for Reference values ​​for active power and reactive power of the system at all times; Switch state pre-selection module: Based on the switch state pre-selection strategy, predict coordinate system The rectifier output voltage reference value is needed at all times. , ; By using the Clarke inverse transform, The output voltage reference value in the coordinate system , Convert to Three-phase output voltage reference value in coordinate system , , ; The performance indicators of each phase arm were sampled to determine the arm with the most severe aging. Sort the output voltage reference values , , To obtain the maximum value and minimum value ; If the reference value of the output voltage of the bridge arm with the most severe aging is not the maximum value. or minimum value Then the output preselected voltage space vector is all 8 voltage space vectors; If the reference value of the output voltage of the bridge arm with the most severe aging is the maximum value mentioned above. Then the output preselected voltage space vector only includes the vector where the aging bridge arm is at the high position; If the output voltage reference value of the bridge arm with the most severe aging is the minimum value Then the output preselected voltage space vector only includes the vector where the aging bridge arm is low-order; Evaluation module: Traverses the pre-selected voltage space vectors and selects the voltage space vector that minimizes the cost function g. and in It is constantly applied to the rectifier.

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