Method and system for inhibiting overvoltage of direct current bus of variable pitch motor driver

Abstract

This application discloses a method and system for suppressing DC bus overvoltage in a pitch motor driver. It predicts the regenerative power the motor will generate in real time based on pitch motion commands and the motor's state, and adaptively lowers a fixed braking trigger voltage threshold according to the predicted power, forming a dynamic threshold. This approach allows the braking system to intervene before large-scale regenerative energy generation, thus pre-suppressing the bus voltage, effectively smoothing voltage spikes, avoiding the overvoltage risk caused by response lag in traditional solutions, and significantly improving the system's stability and reliability.

Description

Technical Field

[0001] This application relates to the field of intelligent suppression, specifically to a method and system for suppressing overvoltage on the DC bus of a pitch motor driver. Background Technology

[0002] In modern wind power systems, the pitch control system is crucial for the stable operation and power generation efficiency of wind turbines. However, during wind turbine operation, especially during rapid blade angle adjustments or emergency shutdowns, the pitch motor frequently enters regenerative braking mode. In this mode, the motor, like a generator, converts kinetic energy into electrical energy and feeds it back to the DC bus of the drive unit. If this regenerative energy is not managed or dissipated effectively or in a timely manner, it will cause a sharp increase in DC bus voltage, leading to overvoltage. DC bus overvoltage can not only damage the power electronic components in the drive unit and reduce system reliability, but it can also trigger false alarms or even cause system shutdown, seriously affecting the continuous and stable operation of the wind turbine. Therefore, developing an efficient DC bus overvoltage suppression method is of paramount importance for ensuring the safe, stable, and efficient operation of the pitch control system.

[0003] Currently, most solutions for suppressing DC bus overvoltage in pitch motor drives rely on feedback control based on bus voltage. These traditional methods monitor the DC bus voltage in real time, and once the voltage exceeds a preset threshold, they activate energy dissipation devices such as braking resistors to reduce the voltage. However, the core drawback of feedback control schemes lies in their inherent response lag. This means that by the time the system detects an overvoltage condition and begins braking, the DC bus voltage may have already experienced a significant or even dangerous instantaneous spike. This response lag is particularly prevalent in actual wind farms when dealing with sudden situations (such as emergency shutdown commands), where the voltage often spikes first before the system takes action. How to integrate multi-source data such as anemometers, blade position encoders, motor current, and pitch commands to establish a feedforward control model that can accurately predict future regenerative power, thereby achieving pre-suppression of overvoltage, remains a technical challenge that has not yet been fully resolved in terms of high-precision and low-cost industrial-grade implementation. Summary of the Invention

[0004] The embodiments disclosed herein aim to at least address one of the technical problems existing in the prior art, providing a method and system for suppressing DC bus overvoltage in a pitch motor driver. This method predicts the regenerative power that the motor will generate in real time based on pitch motion commands and the motor's state, and adaptively lowers a fixed braking trigger voltage threshold according to the predicted power magnitude, forming a dynamic threshold. In this way, the braking system can intervene in advance before large-scale regenerative energy generation, thereby achieving pre-suppression of the bus voltage, effectively smoothing voltage spikes, avoiding the overvoltage risk caused by response lag in traditional solutions, and greatly improving the stability and reliability of the system.

[0005] On the one hand, this application provides a method for suppressing DC bus overvoltage in a pitch motor driver, comprising: Obtain the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment; Based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment, the regeneration intention and power level are predicted to obtain the predicted regeneration power. Based on the predicted regenerative power and rated bus voltage, the basic braking threshold is adaptively adjusted to obtain the dynamic braking threshold. Obtain the actual bus voltage sampled in real time; Calculate the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold; The voltage error signal is input into a digital PI controller to obtain the braking duty cycle; Based on the braking duty cycle, a gate drive signal is generated.

[0006] In another aspect, this application provides a system for suppressing overvoltage on the DC bus of a pitch motor driver, comprising: The data acquisition module is used to acquire the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment. The regeneration intention and power level prediction module is used to predict the regeneration intention and power level based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment in order to obtain the predicted regeneration power. The dynamic suppression module is used to adaptively adjust the basic braking threshold based on the predicted regenerative power and the rated bus voltage to obtain the dynamic braking threshold. The actual bus voltage acquisition module is used to acquire the actual bus voltage sampled in real time. The voltage error calculation module is used to calculate the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold. The PI control module is used to input the voltage error signal into the digital PI controller to obtain the braking duty cycle; The gate drive module is used to generate gate drive signals based on the braking duty cycle.

[0007] Compared with existing technologies, this application provides a method and system for suppressing DC bus overvoltage in a pitch motor driver. It predicts the regenerative power the motor will generate in real time based on pitch motion commands and the motor's state, and adaptively lowers a fixed braking trigger voltage threshold according to the predicted power, forming a dynamic threshold. This approach allows the braking system to intervene before large-scale regenerative energy generation, thus pre-suppressing the bus voltage, effectively smoothing voltage spikes, avoiding the overvoltage risk caused by response lag in traditional solutions, and greatly improving the system's stability and reliability. Attached Figure Description

[0008] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0009] Figure 1 This is a flowchart of a method for suppressing DC bus overvoltage in a pitch motor driver according to an embodiment of this application; Figure 2 This is a data flow diagram of a method for suppressing DC bus overvoltage in a pitch motor driver according to an embodiment of this application; Figure 3 This is a block diagram of a pitch motor driver DC bus overvoltage suppression system according to an embodiment of this application. Detailed Implementation

[0010] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0011] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0012] While this application makes various references to certain modules of the systems according to embodiments of this application, any number of different modules can be used and run on user terminals and / or servers. The modules described are merely illustrative, and different aspects of the systems and methods may use different modules.

[0013] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously as needed. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0014] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0015] The present application proposes a method for suppressing overvoltage on the DC bus of a pitch motor driver. Figure 1 This is a flowchart of a method for suppressing DC bus overvoltage in a pitch motor driver according to an embodiment of this application. Figure 2 This is a data flow diagram illustrating a method for suppressing DC bus overvoltage in a pitch motor driver according to an embodiment of this application. Figure 1 and Figure 2 As shown, the method for suppressing DC bus overvoltage of a pitch motor driver according to an embodiment of this application includes the following steps: S1, acquiring the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment; S2, predicting the regeneration intention and power level based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment to obtain the predicted regeneration power; S3, adaptively adjusting the basic braking threshold based on the predicted regeneration power and the rated bus voltage to obtain the dynamic braking threshold; S4, acquiring the real-time sampled actual bus voltage; S5, calculating the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold; S6, inputting the voltage error signal into a digital PI controller to obtain the braking duty cycle; S7, generating a gate drive signal based on the braking duty cycle.

[0016] Specifically, S1 involves acquiring the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment. It should be understood that in the pitch system of a wind turbine generator, when the motor decelerates or moves in the opposite direction under external forces (such as wind), it enters a power generation state, converting mechanical energy into electrical energy and feeding it back to the DC bus. This is the main reason for excessively high bus voltage. Traditional overvoltage suppression methods are usually passive responses, meaning braking is only initiated after the voltage rises to a certain threshold, resulting in response lag and poor suppression effects. In the technical solution of this application, by actively acquiring these three key parameters, the aim is to transform passive into active. Specifically, the pitch angle command clarifies the motion target that the control system needs to achieve; the actual blade angle at the previous moment and the actual angular velocity of the motor at the previous moment jointly define the current actual state of the system. By comparing the target with the current state, the system can predict the actions (acceleration, deceleration, or maintenance) necessary to achieve the target, thereby predicting in advance whether regenerative energy will be generated and the scale of regenerative energy. This prepares for subsequent dynamic adjustment of the braking threshold and early initiation of energy dissipation, ultimately achieving precise and timely suppression of bus overvoltage.

[0017] The pitch angle command is a target angle value calculated by the wind turbine's main controller based on current wind conditions and grid demand. It represents the precise position the blades are expected to reach in the next stage. This command is the final target input of the pitch drive servo control system. The actual blade angle at the previous moment refers to the blade angle value actually measured and fed back by a position sensor (such as an absolute encoder) before the start of the current control cycle (k), i.e., at the end of the previous control cycle (k-1). This is a feedback quantity reflecting the true position state of the system. The actual angular velocity of the motor at the previous moment is the actual rotational angular velocity of the motor rotor at the end of the previous control cycle, reflecting the dynamic characteristics of the system at the previous moment. These three parameters together constitute the input boundary conditions of the prediction algorithm.

[0018] In practice, firstly, the drive receives the pitch angle command from the wind turbine main controller via an internal communication bus (such as CAN bus or EtherCAT). This command is read as an external input and stored in the drive's memory as the motion target for the current control cycle. Simultaneously, the drive reads from its internal registers or memory the actual blade angle and the actual motor angular velocity measured and stored at the end of the previous control cycle (k-1). These two values ​​serve as feedback on the system state and are the results of the control and measurement in the previous cycle.

[0019] Specifically, S2 predicts the regeneration intention and power level based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment to obtain the predicted regeneration power. It should be understood that in a pitch drive system, when the motor needs to decelerate and brake the high-speed rotating blades, or when the blades are subjected to external torques such as strong winds causing the motor to rotate in the opposite direction, the motor will operate in generator mode, converting mechanical energy into electrical energy and feeding it back to the DC bus of the drive. If this regeneration energy cannot be consumed or stored in time, it will cause the voltage on the bus capacitor to surge rapidly, leading to overvoltage faults and even damage to power devices. Traditional suppression methods often activate the braking circuit only after detecting that the bus voltage has exceeded a fixed threshold, resulting in a response lag, especially when the regeneration power is large, which may not effectively suppress voltage overshoot. In the technical solution of this application, by establishing a predictive model, the regeneration intention and power level (i.e., the magnitude of the regeneration power) can be accurately predicted based on the system's control commands and current state before the actual regeneration energy is generated, generating the key indicator of predicted regeneration power. This forward-looking information allows the system to adjust its response strategy in advance, thereby suppressing bus voltage overshoot more promptly and effectively.

[0020] Among these, regenerative intent is a qualitative judgment of whether the motor will enter a power generation state in the next control cycle. When the motor's torque direction is opposite to its speed direction, it indicates that the motor is performing negative work, and the system intends to generate electricity regenerate. Power level prediction, based on the determination of regenerative intent, is a quantitative estimate of the power fed back to the DC bus. This prediction result is ultimately expressed as the specific physical quantity of predicted regenerative power, measured in watts (W). It represents the regenerative energy flow that the system expects to generate and process in the next control cycle. The magnitude of this value directly determines the subsequent dynamic adjustment of the braking threshold and is the core data for achieving adaptive control.

[0021] In practice, firstly, based on the actual blade angle and the actual angular velocity of the motor at the previous moment, the pitch angle command is analyzed to obtain the commanded angular velocity and angular acceleration. Through this analysis, the system can plan an instantaneous trajectory based on the current actual state and the final target position. This trajectory contains the velocity and acceleration information required to achieve the target. These two dynamic commands are the direct inputs for subsequent calculations and predictions of electromagnetic torque, and consequently, regenerative power. Specifically, the pitch angle command is analyzed using the following formula:

[0022]

[0023] in, This is a pitch angle command. The actual blade angle at the previous moment. The actual angular velocity of the motor at the previous moment. To control the cycle duration.

[0024] Next, the predicted electromagnetic torque is calculated based on the commanded angular velocity and commanded angular acceleration. It should be understood that the mechanical power of a motor is the product of its output torque and angular velocity, while its electromagnetic behavior (such as stator current) is directly related to the electromagnetic torque. Therefore, to predict whether the motor will regenerate electricity and the magnitude of the regenerative power, the predicted electromagnetic torque should be calculated first. By calculating the predicted electromagnetic torque, the system can anticipate the motor's load condition in the next control cycle. This predicted torque value, along with the motor's speed information, will jointly determine whether the system is in a motoring state (consuming electrical energy) or a generating state (producing electrical energy), and is an indispensable prerequisite for calculating the magnitude of the regenerative power. It is worth noting that the predicted electromagnetic torque is not directly measured by sensors, but is a theoretical value calculated based on a defined mathematical and physical model. It represents the total torque that the electromagnetic field inside the motor needs to generate to achieve the commanded angular velocity and commanded angular acceleration calculated in the previous step. This torque consists of multiple components that collectively balance all dynamic and static loads in the system. These components mainly include: the inertial torque used to change the system's angular velocity, the frictional torque used to overcome internal and external friction, and the external load torque used to counteract external forces such as wind and gravity from the blades. Specifically, the predicted electromagnetic torque is calculated using the following formula:

[0025] in, For inertial torque, For frictional torque, For external load torque, The total moment of inertia of the system. is the coefficient of viscous friction.

[0026] Furthermore, regenerative power is predicted based on the predicted electromagnetic torque and the actual angular velocity of the motor at a given moment. In other words, by applying fundamental physical principles, the torque and velocity in the mechanical domain are accurately converted into power in the electrical domain. This final predicted regenerative power value is the culmination of the entire predictive suppression strategy, providing a precise and forward-looking quantitative basis for subsequent dynamic adjustment of the braking threshold. This allows the system to respond appropriately in advance based on the magnitude of the impending energy surge. It is worth noting that the predicted regenerative power represents the electrical power that the system model predicts will be fed back to the DC bus in the next control cycle due to the motor entering generator mode. This value is calculated based on a fundamental physical principle: the mechanical power of the motor equals the product of its electromagnetic torque and rotor angular velocity. When the motor performs negative work, i.e., when the torque direction is opposite to the velocity direction, the mechanical power is negative, indicating that mechanical energy is being absorbed by the system and converted into electrical energy. At this time, the electrical power fed back to the circuit equals the negative mechanical power (ignoring losses). Therefore, the predicted regenerative power numerically represents the energy flow rate in this conversion process.

[0027] In this process, firstly, the regeneration intention is determined. This determination is based on the sign relationship between the predicted electromagnetic torque and the actual angular velocity of the motor at the previous moment. Physically, when the torque and angular velocity are in opposite directions, the motor is in a braking state or being dragged by an external load, i.e., operating in generator mode. In software implementation, this is represented by a negative product. Secondly, assuming the existence of a regeneration intention (i.e., the above product is negative), the regeneration power is calculated. The mechanical power of the motor is the product of the predicted electromagnetic torque and the actual angular velocity of the motor at the previous moment. Since this product is negative, it indicates that the system is absorbing mechanical energy, which will be converted into electrical energy. Therefore, the magnitude of the regeneration power is equal to the absolute value of this negative mechanical power. It is worth mentioning that, to ensure that the final predicted regeneration power value is not negative, a comparison and taking the larger value is usually adopted. Specifically, the system first calculates the product of the predicted electromagnetic torque and the actual angular velocity of the motor at the previous moment, and then takes the negative of the product; then, it compares this calculation result with zero, and takes the larger of the two as the final predicted regeneration power. If the motor is in a motoring or stationary state, the opposite of the product will be negative or zero. The larger of the product and zero will be zero, indicating no regenerative power. Conversely, if the motor is in a generating state, the opposite of the product will be positive. The larger of the product and zero will be the positive number itself, which is the predicted regenerative power.

[0028] Specifically, in step S3, the basic braking threshold is adaptively adjusted based on the predicted regenerative power and the rated bus voltage to obtain a dynamic braking threshold. It should be understood that in traditional control strategies, the braking threshold is usually a fixed, relatively high value (i.e., the basic braking threshold). This setting is a conservative compromise: setting it too low leads to frequent false braking triggers under normal operating conditions, causing unnecessary energy loss and system heating; setting it too high means that when faced with a large regenerative power surge, the bus voltage needs to rise a considerable distance before braking is triggered, during which time voltage overshoot may have already occurred, resulting in lag and poor suppression. In the technical solution of this application, by introducing predicted regenerative power, the braking threshold is no longer a static constant but a variable that dynamically changes with the operating conditions. When the system predicts that a large regenerative power is about to be generated, it proactively and proportionally lowers the braking threshold in advance, allowing the braking control loop to intervene earlier, thereby dissipating regenerative energy more promptly and smoothly, effectively avoiding drastic fluctuations and overshoots in the bus voltage.

[0029] The base braking threshold is a pre-set, fixed voltage value. It is typically set at a relatively safe and conservative level, serving as the default trigger point for the system to initiate regenerative braking when no predictive information is available. The rated bus voltage is the standard voltage value of the driver's DC bus under normal operating conditions, serving as the benchmark for the entire system's voltage level. The dynamic braking threshold is a variable voltage threshold that is recalculated in each control cycle. This dynamic threshold replaces the fixed base threshold, serving as a real-time reference for calculating the voltage error signal in the next stage. Its value depends on the magnitude of the predicted regenerative power, reflecting the adaptive nature of the control.

[0030] In practice, firstly, the initial voltage margin is determined based on the predicted regenerative power and the feedforward gain coefficient. By introducing the feedforward gain coefficient, the power quantity in watts is directly converted into a voltage quantity in volts. This initial voltage margin serves as the basis for lowering the fixed-base braking threshold, ensuring that the threshold adjustment is no longer arbitrary but proportional to the magnitude of the upcoming regenerative power. The larger the predicted regenerative power, the larger the calculated initial voltage margin, and the larger the planned threshold reduction, thus reserving a wider response space for strong energy surges. Specifically, the initial voltage margin is obtained by multiplying the predicted regenerative power value by the feedforward gain coefficient value. This calculation process directly and linearly transforms the predicted power information into a quantity with the same unit as voltage, allowing it to directly participate in subsequent threshold addition and subtraction calculations. This is a feedforward loop that does not rely on any current voltage feedback, generating an initial control adjustment amount entirely based on future predictions. Next, based on the rated bus voltage and safety margin, a minimum dynamic threshold limit is determined. It should be understood that the core of feedforward control is to act in advance based on predictions, but any prediction model may have errors, or the predicted regenerative power may be abnormally high under extreme conditions. If the threshold is adjusted solely based on this prediction, the threshold may be lowered to a level very close to or even below the normal operating voltage (i.e., the rated bus voltage). This could cause the braking circuit to be triggered before any abnormal increase in the bus voltage, resulting in unnecessary energy consumption and increased thermal stress on devices under non-regenerative conditions. More seriously, an excessively low threshold can severely interfere with the normal bus voltage regulation mechanism, potentially leading to system voltage instability or even oscillation. Therefore, in the technical solution of this application, a clear minimum dynamic threshold limit is set, providing a safe constraint on the downward movement of the dynamic threshold and ensuring that the braking logic always operates within a reasonable range of the bus voltage, regardless of the prediction result.

[0031] The minimum dynamic threshold limit represents the absolute lowest level that the dynamic braking threshold can be achieved. At any time, the final effective dynamic braking threshold must not be lower than this limit value; the calculation of this limit value depends on two input parameters. The first is the rated bus voltage, which is the standard design voltage of the driver's DC bus during normal stable operation and serves as the baseline for the system voltage. The second is the safety margin, a pre-set, fixed positive voltage in volts. Physically, it represents the minimum safe isolation band that needs to be maintained between the desired lower limit of the braking threshold and the rated voltage. From a software engineering perspective, it is an important safety configuration parameter, and its value needs to be balanced between ensuring safety and avoiding false triggering. Specifically, the minimum dynamic threshold limit is obtained by adding the rated bus voltage and the safety margin. Furthermore, based on the minimum dynamic threshold limit, the maximum downsizing limit, the original voltage margin, and the basic braking threshold, the dynamic braking threshold is determined. It should be understood that while the original voltage margin reflects the predicted regenerative power, it may have two problems: first, when the predicted regenerative power is abnormally large, it may lead to an excessive and unnecessary large downsizing, which could make the system overly sensitive or even cause oscillations; second, it does not consider the absolute safe lower limit of the system voltage. Therefore, by introducing a dual safety clamping mechanism to constrain the original voltage margin, the final dynamic braking threshold is ensured to reflect the advantages of predictive adjustment without exceeding the preset stable operating boundary. This is the key step in achieving the final balance between pursuing sensitivity and ensuring robustness.

[0032] The maximum reduction limit is a pre-set positive voltage value in volts. Its function is to provide an upper limit for the original voltage margin; that is, regardless of the predicted regenerative power, the reduction in the basic braking threshold cannot exceed this limit. It is an important stability parameter used to suppress excessive feedforward and prevent the system from overreacting to prediction errors or sudden high-power predictions. The dynamic braking threshold is the braking trigger voltage that will actually take effect in the current control cycle, obtained after all calculations and constraints.

[0033] In this process, firstly, the original voltage margin is clamped at the upper limit to obtain the downward adjustment amount constrained by the upper limit. That is, the original voltage margin calculated in the previous step is compared with the preset maximum downward adjustment limit, and the smaller of the two values ​​is selected as the final adopted downward adjustment amount constrained by the upper limit. This process ensures that no matter how large the theoretically calculated adjustment demand is, the actual adjustment range will not exceed a preset safety upper limit. Next, the basic braking threshold is subtracted from the downward adjustment amount constrained by the upper limit to obtain the preliminary dynamic threshold. The preliminary dynamic threshold is an intermediate threshold obtained under the premise of considering feedforward adjustment and ensuring that the adjustment range is not too large. Then, based on the minimum dynamic threshold limit, the preliminary dynamic threshold is constrained by the lower limit to obtain the dynamic braking threshold. That is, the preliminary dynamic threshold is compared with the minimum dynamic threshold limit, and the larger of the two values ​​is selected as the final dynamic braking threshold that takes effect in the current control cycle. This process implements the final safety protection to ensure that no matter how the threshold is lowered, it will never fall below the system's preset safety bottom line.

[0034] Specifically, S4 acquires the actual bus voltage sampled in real time. The actual bus voltage refers to the physically existing voltage difference across the DC link of the pitch driver, i.e., across the large-capacity capacitor. This is the direct control target and protection object of the entire overvoltage suppression method.

[0035] Specifically, at the hardware level, a voltage sensing circuit is first required. Since DC bus voltages are typically hundreds of volts, far exceeding the range that a microcontroller (MCU) or digital signal processor (DSP) analog-to-digital converter (ADC) can handle (typically 0-3.3V or 0-5V), voltage sampling and preprocessing are necessary. This is usually achieved through a high-precision resistor divider network, which proportionally reduces the high voltage to a safe low-voltage range. To improve noise immunity and signal quality, the divided signal typically passes through an analog low-pass filter to remove high-frequency noise. At the software-hardware interaction level, the preprocessed analog voltage signal is connected to an ADC channel of the controller chip. At a specific moment in each control cycle (usually triggered by a timer interrupt to ensure time determinism), the ADC initiates a conversion, quantizing the input analog voltage value into a binary digital value, i.e., the raw ADC sample value. At the software level, the firmware performs the following operations: First, it reads the raw digital value of this conversion from the ADC's data register; then, based on pre-calibrated calibration parameters, the software performs a linear transformation operation to convert this raw ADC value into a voltage value with actual physical units (volts).

[0036] Specifically, in step S5, the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold is calculated. This voltage error signal represents the extent to which the current actual bus voltage exceeds the dynamic braking threshold. This signal has a clear physical meaning and directionality: when its actual value is positive, it indicates that the actual voltage is higher than the dynamic threshold, and the system is in an overvoltage state that needs to be suppressed; the larger the value, the more severe the overvoltage. When its actual value is zero or negative, it indicates that the actual voltage is still within the safe target range, and there is no need to initiate or strengthen braking. Therefore, this voltage error signal is the direct basis for determining whether braking is needed and the braking intensity, and it is a crucial error input in the closed-loop control circuit. By calculating this error, a quantified input that varies with the magnitude of the deviation is provided to the subsequent PI (proportional-integral) controller, ensuring that the intensity of braking energy dissipation matches the degree of actual overvoltage, thereby achieving precise control that avoids over-braking while effectively suppressing overvoltage.

[0037] In practice, the voltage error signal is obtained by calculating the difference between the real-time sampled actual bus voltage and the dynamic braking threshold. It's worth noting that in unidirectional control applications like regenerative braking, the braking circuit only operates when the voltage is too high; when the voltage falls below the threshold, braking should stop completely. Therefore, only a positive voltage error is meaningful. If the result of the above subtraction is negative (i.e., the actual voltage is below the dynamic threshold), it indicates that the system is in a safe state and no braking command should be generated. To achieve this, the software implementation typically includes a logical judgment. That is, by taking the larger value between zero and the calculated result, it is ensured that the output error signal is always zero when the actual voltage is not higher than the dynamic threshold. Thus, a non-zero positive error signal is only generated and transmitted to the subsequent PI controller when the actual voltage truly exceeds the dynamically set threshold. This approach prevents unnecessary integral accumulation (integral saturation) in the non-operating region of the PI controller, improving control stability and response accuracy.

[0038] Specifically, in step S6, the voltage error signal is input to the digital PI controller to obtain the braking duty cycle. That is, a PI (proportional-integral) controller is used to achieve more precise adjustment. The digital PI controller is a classic controller implemented in embedded systems using software algorithms, consisting of proportional and integral components. Specifically, the proportional (P) stage immediately generates a proportional control action based on the current error magnitude, achieving rapid response; the integral (I) stage accumulates historical errors, gradually eliminating static errors that the proportional stage cannot completely eliminate, ensuring that the bus voltage eventually stabilizes near the target threshold. By combining these two stages, the system can dynamically calculate an optimal braking intensity (reflected in the braking duty cycle) based on the magnitude and duration of the error, achieving rapid, stable, and error-free control of the bus voltage. The obtained braking duty cycle is a dimensionless value, typically ranging from 0 to 1 (or 0% to 100%). It directly defines the proportion of the conduction time of the power switch (such as an IGBT or MOSFET) driving the braking resistor within one PWM (pulse width modulation) cycle. A larger duty cycle means a longer switch conduction time, a larger current flowing through the braking resistor, and more energy consumed per unit time, resulting in stronger braking force. Conversely, a smaller duty cycle results in weaker braking force.

[0039] In practice, firstly, the proportional term is calculated. This term directly reflects the immediate impact of the current error magnitude. Specifically, the product of the current voltage error signal value and a preset proportional gain coefficient representing the controller's sensitivity is calculated to obtain the proportional term output. The proportional gain coefficient is a key tuning parameter; its magnitude determines how quickly the controller responds to the current error. Next, the integral term is calculated and updated. This term is used to eliminate steady-state error and reflects the impact of error accumulation. In digital systems, integration is approximated by accumulation. Specifically, the product of the current voltage error signal value and a preset integral gain coefficient value is calculated, and this result is multiplied by the control cycle duration to obtain the integral increment for the current cycle. Then, this increment is added to the accumulated value of the integral term saved at the previous moment to obtain the new accumulated value of the integral term at the current moment. The integral gain coefficient is also a key tuning parameter; its magnitude determines the speed at which the system eliminates steady-state error. In practical engineering, to prevent the integral term from increasing indefinitely when errors persist for a long time, an upper and lower limit is usually set for this accumulated value to prevent integral saturation. Then, the proportional and integral terms are merged. That is, the proportional term output value calculated in the first two steps and the updated integral term output value are added together to obtain the total output of the PI controller, i.e., the initial braking duty cycle command. Subsequently, output limiting is applied. Since the physical meaning of the braking duty cycle dictates that its value must be between "0" representing complete closure and "1" representing complete opening, a range constraint is applied to the initial duty cycle calculated in the previous step. Specifically, if the calculation result is less than 0, the final output braking duty cycle is 0; if the calculation result is greater than 1, the final output braking duty cycle is 1; if the result is between 0 and 1, it remains unchanged. This can be achieved by first comparing the initial duty cycle with 1 and taking the smaller value, and then comparing the result with 0 and taking the larger value. Through the above steps, a precise braking duty cycle is obtained that can quickly respond to the current error, gradually eliminate long-term deviations, and whose value is within the physically permissible range.

[0040] Specifically, S7 generates a gate drive signal based on the braking duty cycle. It should be understood that the braking duty cycle provided by the PI controller cannot directly affect the bus voltage. Only through the gate drive signal can precise control of the power switch (such as an IGBT or MOSFET) be achieved, allowing it to periodically turn on and off. The switching action causes current to flow through the braking resistor, converting excess regenerative energy into heat and dissipating it, thereby stabilizing the bus voltage. Here, the gate drive signal is a pulse signal with specific electrical characteristics specifically designed to control power semiconductor switches. Its key features include: sufficient voltage swing (e.g., swinging from 0V or a negative voltage to +15V to ensure the power transistor is fully turned on and reliably turned off), a sufficiently large peak drive current (in amperes for rapidly charging and discharging the power transistor's input capacitor, shortening switching time and reducing switching losses), and typically electrical isolation characteristics (through optocouplers or magnetic isolation devices) to protect the low-voltage control circuitry from interference and potential damage from the high-voltage main circuitry.

[0041] In practice, the braking duty cycle is written into one or more registers (e.g., a comparator register) within the microcontroller specifically designed for PWM control. The microcontroller then uses this duty cycle value as an instruction to pass it to its built-in PWM generation hardware module; the PWM module within the microcontroller autonomously and with high precision generates the required gate drive signal. Its operation is typically based on a high-speed digital counter and a comparator. Counting period setting: The PWM module is configured to a fixed switching frequency (e.g., 10kHz or 20kHz), which determines the period of the PWM signal. The counter starts counting from zero until a preset period value is reached, then resets and restarts counting. Comparison-generated pulse: The PWM module internally compares the current value of the counter with a comparison value corresponding to the braking duty cycle value passed from the software in real time. When the counter starts counting from zero and reaches this comparison value within one cycle, the state of the PWM output signal will flip (e.g., from low level to high level). When the counter continues counting and reaches the end value of the cycle, the signal state will flip again (from high level to low level), completing a full PWM pulse. Gate driver circuit: The logic level signal directly output by the PWM module is insufficient to directly drive the power switching device. Therefore, this signal first passes through an external gate driver circuit or chip. The gate driver circuit has level conversion, current amplification, and isolation functions. It converts the low-voltage PWM signal from the microcontroller into the high-voltage, high-current signal required by the power switch, and provides the necessary steep rise / fall edges to ensure that the power switch can be turned on and off quickly and reliably, while isolating the voltage difference between the microcontroller and the power section. Finally, this signal processed by the driver circuit is directly applied to the gate (or gate) of the braking power switch to control its operation.

[0042] In summary, the method for suppressing DC bus overvoltage in the pitch motor driver according to the embodiments of this application is explained. It predicts the regenerative power that the motor will generate in real time based on the pitch motion command and state, and adaptively lowers a fixed braking trigger voltage threshold according to the magnitude of the predicted power, forming a dynamic threshold. In this way, the braking system can intervene in advance before the large-scale generation of regenerative energy, thereby achieving pre-suppression of the bus voltage, effectively smoothing voltage spikes, avoiding the overvoltage risk caused by response lag in traditional solutions, and greatly improving the stability and reliability of the system.

[0043] Furthermore, a system for suppressing DC bus overvoltage in a pitch motor driver is also provided.

[0044] Figure 3 This is a block diagram of a pitch motor driver DC bus overvoltage suppression system according to an embodiment of this application. Figure 3 As shown, the overvoltage suppression system 300 for the DC bus of the pitch motor driver according to an embodiment of this application includes: a data acquisition module 310, used to acquire the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment; a regeneration intention and power level prediction module 320, used to predict the regeneration intention and power level based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment to obtain the predicted regeneration power; a dynamic suppression module 330, used to adaptively adjust the basic braking threshold based on the predicted regeneration power and the rated bus voltage to obtain the dynamic braking threshold; an actual bus voltage acquisition module 340, used to acquire the real-time sampled actual bus voltage; a voltage error calculation module 350, used to calculate the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold; a PI control module 360, used to input the voltage error signal into a digital PI controller to obtain the braking duty cycle; and a gate drive module 370, used to generate a gate drive signal based on the braking duty cycle.

[0045] As described above, the pitch motor driver DC bus overvoltage suppression system 300 according to the embodiments of this application can be implemented in various wireless terminals, such as servers with pitch motor driver DC bus overvoltage suppression algorithms. In one possible implementation, the pitch motor driver DC bus overvoltage suppression system 300 according to the embodiments of this application can be integrated into the wireless terminal as a software module and / or a hardware module. For example, the pitch motor driver DC bus overvoltage suppression system 300 can be a software module in the operating system of the wireless terminal, or it can be an application developed for the wireless terminal; of course, the pitch motor driver DC bus overvoltage suppression system 300 can also be one of many hardware modules of the wireless terminal.

[0046] Alternatively, in another example, the overvoltage suppression system 300 for the DC bus of the pitch motor driver and the wireless terminal can also be separate devices, and the overvoltage suppression system 300 for the DC bus of the pitch motor driver can be connected to the wireless terminal via wired and / or wireless networks, and transmit interactive information in accordance with an agreed data format.

[0047] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for suppressing overvoltage on the DC bus of a pitch motor driver, characterized in that, include: Obtain the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment; Based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment, the regeneration intention and power level are predicted to obtain the predicted regeneration power. Based on the predicted regenerative power and rated bus voltage, the basic braking threshold is adaptively adjusted to obtain the dynamic braking threshold. Obtain the actual bus voltage sampled in real time; Calculate the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold; The voltage error signal is input into a digital PI controller to obtain the braking duty cycle; Based on the braking duty cycle, a gate drive signal is generated.

2. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 1, characterized in that, Based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment, the regeneration intention and power level are predicted to obtain the predicted regeneration power, including: Based on the actual blade angle and the actual angular velocity of the motor at the previous moment, the target motion state of the pitch angle command is analyzed to obtain the command angular velocity and command angular acceleration. Calculate the predicted electromagnetic torque based on the commanded angular velocity and commanded angular acceleration; The regenerative power is predicted by using the predicted electromagnetic torque and the actual angular velocity of the motor at a given moment.

3. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 2, characterized in that, Based on the actual blade angle and the actual motor angular velocity at the previous moment, the pitch angle command is analyzed to obtain the commanded angular velocity and commanded angular acceleration. This includes analyzing the target motion state of the pitch angle command using the following formula: in, This is a pitch angle command. The actual blade angle at the previous moment. The actual angular velocity of the motor at the previous moment. To control the cycle duration.

4. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 2, characterized in that, The predicted electromagnetic torque is calculated based on the commanded angular velocity and commanded angular acceleration, including: calculating the predicted electromagnetic torque using the following formula, where the formula is: in, For inertial torque, For frictional torque, For external load torque, The total moment of inertia of the system. It is the coefficient of viscous friction.

5. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 1, characterized in that, Based on the predicted regenerative power and rated bus voltage, the basic braking threshold is adaptively adjusted to obtain the dynamic braking threshold, including: The original voltage margin is determined based on the predicted regenerative power and the feedforward gain coefficient. The minimum dynamic threshold limit is determined based on the rated bus voltage and safety margin. The dynamic braking threshold is determined based on the minimum dynamic threshold limit, the maximum downward adjustment limit, the original voltage margin, and the basic braking threshold.

6. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 5, characterized in that, The minimum dynamic threshold limit is determined based on the rated bus voltage and safety margin, including adding the rated bus voltage and safety margin to obtain the minimum dynamic threshold limit.

7. The method for suppressing DC bus overvoltage in a pitch motor driver according to claim 5, characterized in that, Based on the minimum dynamic threshold limit, the maximum downsizing limit, the original voltage margin, and the basic braking threshold, the dynamic braking threshold is determined, including: The original voltage margin is clamped at the upper limit to obtain the amount of reduction of the upper limit constraint; The initial dynamic threshold is obtained by subtracting the downward adjustment of the upper limit constraint from the basic braking threshold. Based on the minimum dynamic threshold limit, a lower threshold constraint is applied to the initial dynamic threshold to obtain the dynamic braking threshold.

8. A system for suppressing overvoltage on the DC bus of a pitch motor driver, characterized in that, include: The data acquisition module is used to acquire the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment. The regeneration intention and power level prediction module is used to predict the regeneration intention and power level based on the pitch angle command, the actual blade angle at the previous moment, and the actual angular velocity of the motor at the previous moment in order to obtain the predicted regeneration power. The dynamic suppression module is used to adaptively adjust the basic braking threshold based on the predicted regenerative power and the rated bus voltage to obtain the dynamic braking threshold. The actual bus voltage acquisition module is used to acquire the actual bus voltage sampled in real time. The voltage error calculation module is used to calculate the voltage error signal between the real-time sampled actual bus voltage and the dynamic braking threshold. The PI control module is used to input the voltage error signal into the digital PI controller to obtain the braking duty cycle; The gate drive module is used to generate gate drive signals based on the braking duty cycle.

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