A control method of an outer ring single-proportion regulation independent excitation power generation system

Abstract

The application discloses an independent excitation power generation system control method of outer ring single proportion regulation, and when the load in the independent excitation direct current power generation system suddenly increases or suddenly decreases, the capacitor energy error is used as the input given value of the outer ring single proportion regulator, the regulator output is the instantaneous power increment given value, the load current increment given value is obtained after the division operation processing, the actual load current feedback is added, the excitation current given value is converted from the load excitation corresponding relation, so that the voltage stabilization control is realized. The control method provided by the application solves the problem that the integral element of the existing capacitor energy balance control outer ring PI regulator causes the instantaneous power increment to be not 0 at the system steady state, and the obtained energy storage current increment is contradictory to the introduced load current feedback. The optimization setting of the outer ring proportion gain improves the voltage stabilization control dynamic performance and voltage steady state precision of the system under the load current change, so that the system has good voltage following performance and load change robustness.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and mainly to a control method for an independent excitation power generation system with single-proportional adjustment of the outer loop. Background Technology

[0002] Independent excitation generators include electrically excited and hybrid excitation generators. These generators are widely used in special vehicles, aviation power generation and other applications with high safety requirements because they have the advantages of easy adjustment of the excitation magnetic field, rapid interruption of the excitation current to achieve fault demagnetization in the event of a generator failure, and stable output voltage over a wide speed range.

[0003] The control algorithm for independently excited DC generator systems is generally a voltage closed-loop control (VCC) based on a PI regulator. This dual-loop control structure, employing both output voltage and excitation current, can accelerate the response speed of the excitation current compared to single-voltage-loop control. While the PI regulator in the voltage loop can ensure the steady-state control accuracy of the system's output voltage, limitations due to fixed PI parameters and the system's inherent nonlinearity can lead to slow response speed and large voltage recovery overshoot when the system faces sudden load changes under different operating conditions.

[0004] To improve the dynamic performance of independent excitation generator systems, the paper "Capacitor-Energy-based Control of Doubly Salient Brushless DC Generator for Dynamic Performance Optimization" (Yanwu Xu; Zhuoran Zhang; Zhangming Bian; Li Yu, IEEE Transactions on Energy Conversion, 2020, vol:35, no:4, 1886-1896) proposes a generator control method based on charge and discharge energy control. Its main control idea is as follows: the expected value of the charging power of the filter capacitor is subtracted from the actual value. This difference is passed through a PI regulator to obtain the expected value of the charging current. The expected value of the charging current is added to the load current to obtain the output current of the rectifier circuit. Then, based on the functional relationship between the output current of the rectifier circuit and the excitation current, the setpoint of the excitation current is obtained. A half-bridge converter is used to chop the actual value of the excitation current to make it track the setpoint. Compared with traditional magneto-voltage regulation methods, this control strategy, using the charging current as the control target, improves system performance and reduces the dynamic ripple of the output voltage. However, the output of a PI controller consists of both a proportional and an integral element. Since the voltage error of the system in steady state is zero, the proportional element output of the outer-loop PI controller in the above control method is zero. If the output of the integral element is also required to be zero in steady state, taking a sudden load increase as an example, the capacitor energy storage waveform during all sudden load increases should be as shown in the attached figure. Figure 4 As shown, the integral value of the energy storage error of the integral element is zero only when the error area SL of the shaded area is equal to SH after the dynamic phase ends. This indicates that, theoretically, the integral element of the above control method will inevitably introduce overshoot into the system, and the magnitude of the overshoot depends on the integral gain coefficient, which is inconsistent with the original intention of the control algorithm to improve the dynamic performance of the system.

[0005] The outer-loop integral term in the above control strategy conflicts with the current load introduced by the system itself, resulting in steady-state regulation error and multiple adjustment processes in the dynamic waveform of the output voltage, including overshoot / downshoot. Therefore, to further improve the dynamic performance of the system, it is necessary to consider removing the tuning and optimization steps of the single proportional gain after removing the outer-loop integral gain. This would allow the entire power generation system to quickly adjust the outer-loop single proportional gain to maintain output voltage stability under different operating conditions; it would also allow for faster adaptation to system capacitor parameter mismatch, reducing the system's sensitivity to capacitor parameters and improving the system's control robustness.

[0006] Furthermore, the document "A Control Method for a Hybrid Excitation Generator (Application No.: 202110256068.6)" is based on the idea of ​​capacitor charge balance and rationally designs the excitation current increase and decrease times without PI regulation to achieve one-time regulation convergence of output voltage during load abrupt changes. However, this process involves control switching from linear control to nonlinear control, which reduces the robustness of system control. The document "An Optimal Dynamic PI Parameter Tuning Method for a Magnetic and Voltage Regulating DC Generator System (Application No.: 202111286479.6)" is based on the conventional voltage vector control method and provides a voltage outer loop PI parameter tuning method. Its outer loop uses output voltage as the control target, while the control strategy based on capacitor energy balance uses charging current as the control target. On this basis, load current feedforward is introduced to remove the integral gain in the outer loop PI parameters, thereby reducing the overshoot oscillation caused by integral gain compared to the former, thus accelerating the dynamic response speed of the system. Summary of the Invention

[0007] Objective of the Invention: As can be seen from the control methods proposed in the background literature, the integral element of its outer-loop PI regulator has almost no effect on improving the dynamic performance of the system under load current variations. Therefore, this invention provides a control method for an independent excitation power generation system with single-proportional regulation in the outer loop. This method eliminates the integral element in the power outer loop, resolves the contradiction with the introduction of load current feedback by using single-proportional regulation, and proposes a system parameter optimization design procedure, thereby improving the dynamic performance of the system's voltage regulation control and the voltage steady-state accuracy under load current variations.

[0008] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0009] A control method for an independent excitation power generation system with outer-loop single-proportional adjustment is disclosed. The independent excitation power generation system includes an electrically excited / hybrid excited generator, an excitation current control module, a three-phase diode uncontrolled rectifier circuit, a filter capacitor, a load, an excitation / load current sensor, and an output voltage sensor. The three-phase diode uncontrolled rectifier circuit comprises three parallel bridge arms, each composed of two diodes connected in series. The midpoints of the three bridge arms are respectively connected to one end of the three-phase armature winding of the independent excitation generator, and the other end of the three-phase armature winding is short-circuited. The three-phase diode uncontrolled rectifier circuit is connected in parallel with the filter capacitor, the output voltage sensor, and the load, with the load and the load current sensor connected in series. The excitation current control module includes a single-phase full-bridge converter and an excitation winding voltage source. The single-phase full-bridge converter is powered by the excitation winding voltage source and comprises two parallel bridge arms, each composed of two switching transistors. The midpoints of the two sets of switching transistors are connected between the excitation winding and the excitation current sensor. The specific steps of the control method for the independent excitation power generation system with outer-loop single-proportional adjustment are as follows:

[0010] Step S1: Record the load current i at different steady-state conditions of the generator system while the generator is running at different speeds. o The corresponding excitation current value i f The load current i at different speeds n is obtained by fitting using the least squares method. o With excitation current value i f Relationship;

[0011] Step S2: Calculate the excitation current value i of the independent excitation power generation system under different constant speed steady-state operation conditions using the fitted relationship from step S1. f With load current i o The fitting coefficient K between them, which characterizes the fitting relationship, is shown below:

[0012]

[0013] Where a, b, c, and d represent polynomial coefficients, and the average value of the pre-stage rectifier current i is... recav equals i o ;

[0014] Step S3: The error between the capacitor energy stored after load disturbance and the capacitor energy stored corresponding to the reference voltage is adjusted by a single proportional adjustment and output as the instantaneous power increment reference. Divide the instantaneous power increment given value by the output voltage u after the disturbance. o Obtain the specified value of the energy storage current increment The load feedback current i is added to the specified value of the energy storage current increment. o As the command value of the rectified current Then, the excitation current is obtained by converting the fitting coefficient K given in step S2.

[0015] Step S4: Determine the excitation resistance R of the excitation winding. f With excitation inductance L f Then, based on the excitation current given value obtained in step S3, the PI parameter of the inner loop of the excitation current is tuned to achieve output voltage regulation control.

[0016] Furthermore, the control system parameter optimization design process in step S3 is as follows:

[0017] Step S3.1: Convert the output voltage u o Multiply by the feedback coefficient K1' and the given reference voltage u o * Multiplying by the feedback coefficient K1 and taking the difference, since the energy feedback loop has a squared output voltage term, the feedback coefficient K1' and K1 can be equivalently represented as a fixed gain as follows:

[0018]

[0019] Where C is the capacitance value of the filter capacitor;

[0020] Step S3.2: To approximate the result, multiply the difference by the single proportional adjustment coefficient K. p Obtain the instantaneous power increment given The instantaneous power increment is given by dividing the output voltage u. o The equivalent is to multiply the instantaneous power increment by a fixed gain K2 as the specified value of the energy storage current increment. K2 is represented as follows:

[0021]

[0022] The feedback energy storage current passes through the transfer function module G c (s) provides the output voltage u o (s), G c The expression for (s) is as follows:

[0023]

[0024] Furthermore, the control system parameter optimization design process in step S4 is as follows:

[0025] Step S4.1, the open-loop transfer function of the excitation current loop structure is expressed as:

[0026]

[0027] To achieve zero-pole cancellation, a suitable current loop bandwidth ω needs to be determined. f Select k p k i The parameters are as follows:

[0028]

[0029] The closed-loop transfer function of the excitation current loop of the reduced first-order inertial system is obtained as follows:

[0030]

[0031] Step S4.2: The simplified transfer function from load disturbance to output is given as follows:

[0032]

[0033] The gain of the feedback loop in this control method is K1, the magnitude of which depends on the capacitance and the given voltage. The actual value of K1 is much smaller than unity gain; therefore, the outer loop single proportional coefficient K... p The value is relatively large.

[0034] Furthermore, the outer ring single proportional coefficient K pThe specific tuning steps are as follows:

[0035] Step S5: Based on the state equation of the output capacitor voltage, calculate the load current from I. o1 To I o3 The time function expression for the ideal optimal output voltage curve under abrupt changes;

[0036] Step S6: Based on the concept of capacitor charge balance, for any given rotational speed n, a specific load current I... o1 To I o3 The sudden change is achieved by using the excitation current i fitted in S1. f Load current i o The optimal outer loop single proportional coefficient K is obtained by considering the relationship between the three factors: rotational speed n, and rotational speed n. p .

[0037] Furthermore, the process of obtaining the time function expression for the ideal optimal output voltage curve under load abrupt change in step S5 is as follows:

[0038] Step S5.1: Transform the state equation of the load terminal capacitor voltage into a first-order differential equation:

[0039]

[0040] Where C is the capacitance of the filter capacitor, Z is the equivalent impedance of the load terminal, and i rec The rectified current before the filter capacitor is i in steady state. rec equals i o ;

[0041] Step S5.2, for the load current I o1 To I o3 The abrupt change, let Z be the equivalent impedance after the abrupt change, and use... It means that u o * Given the output voltage, solving the first-order differential equation yields:

[0042]

[0043] Treating the moment t0 of the load mutation as 0, the above equation simplifies to:

[0044]

[0045] The rectified current i before the filter capacitor rec Due to the excitation current i f Direct control. Excitation winding self-inductance L f The magnetizing current i is relatively large when the full-bridge switching transistor outputs full duty cycle. f Linear rise or fall, slope and self-inductance L fRelated. Without considering magnetic field saturation, assuming i rec Follow i f The linear increase or decrease has an upward slope of k1 and a downward slope of -k1.

[0046] Step S5.3: Based on the concept of capacitor charge balance, ideally, after a sudden increase in load current, the rectified current i rec It should follow the excitation current i f Linear increase, expressed as a time function: i rec =k1t+I o1 The time function of the decreasing phase of the excitation current is related to time t2. Let t2 = x, then the expression for the decrease is: i' rec = -k1t+b, at time t2, i rec =i' rec We get b = 2k1x + I o1 Then the rectified current i rec The segmented representation is as follows:

[0047]

[0048] The ideal load mutation end time t3 depends on i when t>x. rec The expression, and the value I before and after the sudden change in load current. o1 and I o3 Represented as:

[0049]

[0050] Step S5.4: Transform the rectified current i into segments. rec Substituting the output voltage expression from step S5.2 and simplifying it, the ideal piecewise time function of the output voltage is expressed as:

[0051]

[0052] Furthermore, after the load current suddenly decreases, the rectified current i rec The segmented representation is as follows:

[0053]

[0054] The sign of k1 is inverted in the formula, while the rest of the derivation process remains unchanged.

[0055] Furthermore, in step S6, the load current is determined by I. o1 To I o3 The optimal outer loop single proportional coefficient K under mutation p The calculation process is as follows:

[0056] Step S6.1: Determine relevant time nodes t1, t2, and t3 of the ideal dynamic waveform in step S5.3; let the output voltage u in step S5.4 o Differentiate the segment 0<t<x in the expression with respect to time, set the derivative to 0, and solve to obtain t1:

[0057]

[0058] Step S6.2: According to the principle of capacitor charge balance, there is S A =S B +S C , wherein S A is:

[0059]

[0060] Wherein time t1 is known, the expressions of u o and i rec are the first segment of the two piecewise functions in steps S5.3 and S5.4, and S B +S C is expressed as:

[0061]

[0062] Let S A =S B +S C the single unknown x can be solved, and then the time quantities t2 and t3 can be obtained by the following formula:

[0063]

[0064] Step 6.3: Obtain the optimal single outer loop proportional coefficient K corresponding to the sudden change of the load current from I o1 to I o3 K p , K is obtained by the following formula p :

[0065]

[0066] Adopting the above technical solution conceived by the present invention can achieve the following beneficial effects:

[0067] (1) The independent excitation power generation system control method based on single proportional adjustment of capacitor energy balance outer loop provided by the present invention performs single proportional control on the capacitor energy storage outer loop on the basis of retaining the excitation current inner loop, and removes the integral link, thereby avoiding the contradiction caused by introducing load current feedback. This ensures that there is no steady-state error after the dynamic process of the system ends, and improves the dynamic performance of the system under load sudden change.

[0068] (2) The control strategy provided by the present invention can adjust the single proportional adjustment coefficient of the outer loop based on the capacitor parameters. The optimal single proportional gain coefficient of the outer loop is tuned by the capacitor charge balance control idea, so that the system dynamic response speed is faster, the ability to suppress load disturbance is stronger, the influence of capacitor parameter mismatch is smaller, and the overall robustness is stronger.

[0069] (3) Compared with the traditional voltage closed-loop control algorithm, the control strategy provided by the present invention has stronger adaptability to load step disturbances under different operating conditions. After parameter optimization, it is easier to obtain load step response results close to critical damping, output voltage recovery is fast, and dynamic performance is excellent. Attached Figure Description

[0070] Figure 1 The hardware structure diagram of the independent excitation power generation system provided by this invention;

[0071] Figure 2 This is a control structure diagram for an independent excitation power generation system with single-proportional regulation in the outer loop.

[0072] Figure 3 This is a diagram of the current loop structure of the excitation control module;

[0073] Figure 4 This is the output voltage waveform under normal load sudden change;

[0074] Figure 5 This is a control principle diagram of an independent excitation power generation system with single proportional regulation in the outer loop;

[0075] Figure 6 The ideal waveforms of output voltage, load current, and rectified current corresponding to a sudden increase in load current;

[0076] Figure 7 This is a block diagram of a traditional voltage and current dual closed-loop control.

[0077] Figure 8 The diagram shows the unit step response of the output voltage to the load disturbance after adding an integral element.

[0078] Figure 9 The figure shows the unit step response of the load disturbance to the output voltage under different single proportional regulation coefficients;

[0079] Figure 10 This is a comparison of the voltage response waveforms of conventional voltage vector control and the control voltage of this invention under load disturbance. Detailed Implementation

[0080] To make the objectives, technical solutions, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the specific embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0081] Figure 5 This is a control principle diagram of an independent excitation power generation system based on capacitor energy balance outer loop single proportional regulation. The applied hardware system topology is as follows: Figure 1 As shown, it includes an electrically excited / hybrid excited generator, an excitation current control module, a three-phase diode uncontrolled rectifier circuit, a filter capacitor, a load, an excitation / load current sensor, and an output voltage sensor. The three-phase diode uncontrolled rectifier circuit comprises three parallel bridge arms, each consisting of two diodes connected in series; the midpoints of the three bridge arms are respectively connected to one end of the three-phase armature winding of the independent excited generator, and the other end of the three-phase armature winding is short-circuited; the three-phase diode uncontrolled rectifier circuit is connected in parallel with the filter capacitor, the output voltage sensor, and the load, with the load and load current sensor connected in series; the excitation current control module includes a single-phase full-bridge converter and an excitation winding voltage source; the single-phase full-bridge converter is powered by the excitation winding voltage source and comprises two parallel bridge arms, each consisting of two switching transistors, with the excitation winding and the excitation current sensor connected between the midpoints of the two sets of switching transistors.

[0082] This invention provides a control method for an independent excitation power generation system based on single proportional regulation of the outer loop of capacitor energy balance. The specific implementation steps are as follows:

[0083] Step S1: Record the load current i at different steady-state conditions of the generator system while the generator is running at different speeds. o The corresponding excitation current value i f The load current i at different speeds n is obtained by fitting using the least squares method. o With excitation current value i f Relationship;

[0084] Step S2: Calculate the excitation current value i of the independent excitation power generation system under different constant speed steady-state operation conditions using the fitted relationship from step S1. f With load current i o The fitting coefficient K between them, which characterizes the fitting relationship, is shown below:

[0085]

[0086] Where a, b, c, and d represent polynomial coefficients, and the average value of the pre-stage rectifier current i is... recav equals i o ;

[0087] Step S3: The error between the capacitor energy stored after load disturbance and the capacitor energy stored corresponding to the reference voltage is adjusted by a single proportional adjustment and output as the instantaneous power increment reference. Divide the instantaneous power increment given value by the output voltage u after the disturbance. o Obtain the specified value of the energy storage current increment The load feedback current i is added to the specified value of the energy storage current increment. o As the command value of the rectified current Then, the excitation current is obtained by converting the fitting coefficient K given in step S2.

[0088] Step S4: Determine the excitation resistance R of the excitation winding. f With excitation inductance L f Then, based on the excitation current given value obtained in step S3, the PI parameter of the inner loop of the excitation current is tuned to achieve output voltage regulation control.

[0089] Specifically, the control system parameter optimization design process in step S3 is as follows:

[0090] Step S3.1: Convert the output voltage u o Multiply by the feedback coefficient K1' and the given reference voltage u o * Multiplying by the feedback coefficient K1 and taking the difference, since the energy feedback loop has a squared output voltage term, the feedback coefficient K1' and K1 can be equivalently represented as a fixed gain as follows:

[0091]

[0092] Where C is the capacitance value of the filter capacitor;

[0093] Step S3.2: To approximate the result, multiply the difference by the single proportional adjustment coefficient K. p Obtain the instantaneous power increment given The instantaneous power increment is given by dividing the output voltage u. o The equivalent is to multiply the instantaneous power increment by a fixed gain K2 as the specified value of the energy storage current increment. K2 is represented as follows:

[0094]

[0095] The feedback energy storage current passes through the transfer function module G c (s) provides the output voltage u o (s), G c The expression for (s) is as follows:

[0096]

[0097] Specifically, the control system parameter optimization design process in step S4 is as follows:

[0098] Step S4.1, the open-loop transfer function of the excitation current loop structure is expressed as:

[0099]

[0100] To achieve zero-pole cancellation, a suitable current loop bandwidth ω needs to be determined. f Select k p k i The parameters are as follows:

[0101]

[0102] The closed-loop transfer function of the excitation current loop of the reduced first-order inertial system is obtained as follows:

[0103]

[0104] Step S4.2: The simplified transfer function from load disturbance to output is given as follows:

[0105]

[0106] The gain of the feedback loop in this control method is K1, the magnitude of which depends on the capacitance and the given voltage. The actual value of K1 is much smaller than unity gain; therefore, the outer loop single proportional coefficient K... p The value is relatively large.

[0107] Specifically, the outer ring single proportional coefficient K p The specific tuning steps are as follows:

[0108] Step S5: Based on the state equation of the output capacitor voltage, calculate the load current from I. o1 To I o3 The time function expression for the ideal optimal output voltage curve under abrupt changes;

[0109] Step S6: Based on the concept of capacitor charge balance, for any given rotational speed n, a specific load current I... o1 To I o3 The sudden change is achieved by using the excitation current i fitted in S1. f Load current i o The optimal outer loop single proportional coefficient K is obtained by considering the relationship between the three factors: rotational speed n, and rotational speed n. p .

[0110] Specifically, the process of obtaining the time function expression of the ideal optimal output voltage curve under the condition of load change in step S5 is as follows:

[0111] Step S5.1: Transform the state equation of the load terminal capacitor voltage into a first-order differential equation:

[0112]

[0113] Where C is the capacitance of the filter capacitor, Z is the equivalent impedance of the load terminal, and i rec The rectified current before the filter capacitor is i in steady state. rec equals i o ;

[0114] Step S5.2, for the load current I o1 To I o3 The abrupt change, let Z be the equivalent impedance after the abrupt change, and use... It means that u o * Given the output voltage, solving the first-order differential equation yields:

[0115]

[0116] Treating the moment t0 of the load mutation as 0, the above equation simplifies to:

[0117]

[0118] The rectified current i before the filter capacitor rec Due to the excitation current i f Direct control. Excitation winding self-inductance L f The magnetizing current i is relatively large when the full-bridge switching transistor outputs full duty cycle. f Linear rise or fall, slope and self-inductance L f Related. Without considering magnetic field saturation, assuming i rec Follow i f The linear increase or decrease has an upward slope of k1 and a downward slope of -k1.

[0119] Step S5.3: Based on the concept of capacitor charge balance, ideally, after a sudden increase in load current, the rectified current i rec It should follow the excitation current i f Linear increase, expressed as a time function: i rec =k1t+I o1 The time function of the decreasing phase of the excitation current is related to time t2. Let t2 = x, then the expression for the decrease is: i' rec = -k1t+b, at time t2, i rec =i' rec We get b = 2k1x + I o1 Then the rectified current i rec The segmented representation is as follows:

[0120]

[0121] The ideal end time t3 of the load sudden change is based on i when t>x rec expression, and the values I before and after the sudden load current change o1 and I o3 expressed as:

[0122]

[0123] Step S5.4: Substitute the segmented rectified current i rec into the output voltage expression in step S5.2 and simplify it, and the ideal piecewise time function of the output voltage is expressed as:

[0124]

[0125] Specifically, after the sudden reduction of the load current, the rectified current i rec is expressed in sections as:

[0126]

[0127] In the formula, the sign of k1 is inverted, and the rest of the derivation process remains unchanged.

[0128] Specifically, in the step S6, the load current changes from I o1 to I o3 the optimal outer loop single proportional coefficient K under sudden change p the obtaining process is as follows:

[0129] Step S6.1: Obtain the relevant time nodes t1, t2, and t3 of the ideal dynamic waveform in step S5.3; differentiate the 0<t<x segment with respect to time in the expression of the output voltage u in step S5.4, set the derivative to 0, and solve for t1: o

[0130]

[0131] Step S6.2: According to the idea of capacitor charge balance, there is S A = S B + S C , wherein S A is:

[0132]

[0133] wherein the time t1 is known, and the expressions of u o and i rec are the first segment of the two piecewise functions in steps S5.3 and S5.4, and S B + S C is expressed as:

[0134] ​

[0135] Let S A =S B +S C Once the single unknown x is solved, the time quantities t2 and t3 can be obtained using the following formula:

[0136]

[0137] Step 6.3: Calculate the load current using I. o1 To I o3 The optimal outer loop single proportional coefficient K corresponding to the mutation p K can be obtained from the following formula. p :

[0138]

[0139] Traditional voltage and current dual closed-loop block diagram as follows Figure 7 As shown, this dual-loop control structure can accelerate the response speed of the excitation current compared to single-voltage-loop control. However, due to the fixed PI parameters and the nonlinearity of the system itself, the dynamic adjustment characteristics of the output voltage may suffer from slow response speed and large voltage recovery overshoot when the system faces sudden load changes under different operating conditions. Therefore, the voltage error input of the traditional outer-loop PI regulator is replaced with the capacitor energy storage error input, resulting in better control performance in terms of system dynamics.

[0140] In existing literature, the output of the outer-loop PI regulator in generator control methods based on charge and discharge energy control consists of both proportional and integral components. Since the voltage error of the system in steady state is zero, the proportional component output of the outer-loop PI regulator in these methods is zero. If the output of the integral component is also required to be zero in steady state, taking a sudden load increase as an example, the capacitor energy storage waveform during all load increases should be as follows... Figure 4 As shown, the integral value of the energy storage error of the integral element is zero only when the error area SL of the shaded area is equal to SH after the dynamic phase ends. This indicates that, theoretically, the integral element of the above control method will inevitably introduce overshoot into the system, and the magnitude of the overshoot depends on the integral gain coefficient, which is inconsistent with the original intention of the control algorithm to improve the dynamic performance of the system.

[0141] Furthermore, the integral gain introduced by the above control method contradicts the load current feedback introduced by the system. If the system outer loop introduces an integral gain coefficient K... I Different integral gain coefficients K I The corresponding unit step response of the load disturbance to the output voltage is as follows: Figure 8 As shown. The outer-loop control, after introducing integral gain, causes the system to slowly adjust for the existing steady-state error after the dynamic process ends. The integral gain coefficient K...I Variations within a certain range do not help improve the dynamic performance of the system's step response, while excessively large values ​​will cause severe overshoot.

[0142] Removing the integral gain stage, the outer loop only has a single proportional gain coefficient K. p The system's unit step response to load disturbance to output voltage under different single proportional regulation coefficients is as follows: Figure 9 As shown, the integral gain coefficient K I When K = 0, p The larger the value of K, the faster the dynamic response speed, but it cannot be too large, otherwise overshoot will occur. Furthermore, it can be observed that when K... I When = 0, with the single proportional gain coefficient K p With the change, the system has no steady-state error at the end of the dynamic process, and the dynamic response speed is fast.

[0143] Compared to conventional voltage vector control methods that use capacitor charge balance to tune the PI controller, the voltage regulation effect achieved by using the charging current as the control target to tune the outer loop single proportional gain coefficient is different. Figure 10 As shown, under the same load change conditions, the control method proposed in this invention can achieve voltage stabilization faster than the conventional voltage vector control method, with almost no overshoot, fast dynamic response speed, and strong adaptability to load disturbances.

[0144] In summary, the independent excitation power generation system control method based on capacitor energy balance outer loop single proportional regulation provided by this invention solves the problems of slow dynamic regulation and steady-state error caused by the outer loop integral gain. Compared with traditional voltage vector control, it improves the dynamic performance of voltage regulation control and voltage steady-state accuracy of the system under load current changes.

[0145] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A control method for an independent excitation power generation system with single-proportional outer-loop regulation, characterized in that, The specific steps are as follows: Step S1: Record the load current i under steady-state conditions of the independent excitation power generation system when the generator operates at different speeds. o The corresponding excitation current value i f Fit the load current i at different speeds n o With excitation current value i f Relationship; Step S2: Calculate the excitation current value i of the independent excitation power generation system under different constant speed steady-state operation conditions using the fitted relationship from step S1. f With load current i o The fitting coefficient K between them; Step S3: The error between the capacitor energy stored after load disturbance and the capacitor energy stored corresponding to the reference voltage is adjusted by a single proportional adjustment and output as the instantaneous power increment reference. The instantaneous power increment given value is divided by the output voltage u after the disturbance. o Obtain the specified value of the energy storage current increment The specified value of the energy storage current increment is superimposed on the load feedback current i. o As the command value of the rectified current Then, the excitation current is obtained by converting the fitting coefficient K given in step S2. ; Step S4: Determine the excitation resistance R of the excitation winding. f With excitation inductance L f Then, based on the excitation current given value obtained in step S3, the PI parameter of the inner loop of the excitation current is tuned to achieve output voltage regulation control. Wherein, the outer ring single proportional coefficient K p The specific tuning steps are as follows: Step S5: Based on the state equation of the output capacitor voltage, calculate the load current from I. o1 To I o3 The time function expression of the ideal optimal output voltage curve under abrupt changes; Step S6: Based on the concept of capacitor charge balance, for any given rotational speed n, a specific load current I... o1 To I o3 The sudden change is achieved by using the excitation current i fitted in S1. f Load current i o The optimal outer loop single proportional coefficient K is obtained by considering the relationship between the three factors: rotational speed n, and rotational speed n. p ; The process of obtaining the time function expression of the ideal optimal output voltage curve under the condition of load change in step S5 is as follows: Step S5.1: Transform the state equation of the load terminal capacitor voltage into a first-order differential equation: ； Where C is the capacitance of the filter capacitor, Z is the equivalent impedance of the load terminal, and i rec The rectified current before the filter capacitor is i in steady state. rec equals i o ; Step S5.2, for the load current I o1 To I o3 The abrupt change, let Z be the equivalent impedance after the abrupt change, and use... It means that u o * Given the output voltage, solving the first-order differential equation yields: ； Treating the moment t0 of the load mutation as 0, the above equation simplifies to: ； The rectified current i before the filter capacitor rec Due to the excitation current i f Direct control; without considering magnetic field saturation, i rec Follow i f Linear change, with a slope of k1; Step S5.3: Based on the concept of capacitor charge balance, ideally, after a sudden change in load current, the rectified current i rec The segmented representation is as follows: ； The ideal load mutation end time t3 depends on i when t>x. rec The expression, and the value I before and after the sudden change in load current. o1 and I o3 Represented as: ； Step S5.4: Transform the rectified current i into segments. rec Substituting the output voltage expression from step S5.2 and simplifying it, the ideal piecewise time function of the output voltage is expressed as: ； In step S6, the load current is determined by I. o1 To I o3 The optimal outer loop single proportional coefficient K under mutation p The calculation process is as follows: Step S6.1: Obtain relevant time nodes t1, t2 and t3 of the ideal dynamic waveform in step S5.3; set the output voltage u in step S5.4 o differentiate the segment 0<t<x in the expression with respect to time, set the derivative to 0, and solve to obtain t1: ； Step S6.2: Based on the concept of capacitor charge balance, we have S A =S B +S C S A for: ； Where time t1 is known, u o and i rec The expression is the first segment of the two piecewise functions in steps S5.3 and S5.4, S B +S C Represented as: ； Let S A =S B +S C Once the single unknown x is solved, the time quantities t2 and t3 can be obtained using the following formula: ； Step 6.3: Calculate the load current using I. o1 To I o3 The optimal outer loop single proportional coefficient K corresponding to the mutation p K can be obtained from the following formula. p : 。 2. The control method for an independent excitation power generation system with outer loop single proportional regulation according to claim 1, characterized in that, The control system parameter optimization design process in step S3 is as follows: Step S3.1: Convert the output voltage u o Multiply by the feedback coefficient K1 ’ With a given reference voltage u o * Multiply by the feedback coefficient K1 and take the difference. Since the energy feedback loop has a squared output voltage term, the feedback coefficient K1 is... ’ The equivalent of K1 to a fixed gain is expressed as follows: ； Where C is the capacitance value of the filter capacitor; Step S3.2: To approximate the result, multiply the difference by the single proportional adjustment coefficient K. p Obtain the instantaneous power increment given The instantaneous power increment is given by dividing the output voltage u. o The equivalent is to multiply the instantaneous power increment by a fixed gain K2 as the specified value of the energy storage current increment. K2 is represented as follows: ； The feedback energy storage current passes through the transfer function module G c (s) provides the output voltage u o (s), G c The expression for (s) is as follows: 。 3. The control method for an independent excitation power generation system with single-proportional adjustment of the outer loop according to claim 2, characterized in that, The control system parameter optimization design process in step S4 is as follows: Step S4.1, the open-loop transfer function of the excitation current loop structure is expressed as: ； To achieve pole-zero cancellation, a suitable current loop bandwidth needs to be determined. Select k p k i The parameters are as follows: ； The closed-loop transfer function of the excitation current loop of the reduced first-order inertial system is obtained as follows: ； Step S4.2: The simplified transfer function from load disturbance to output is given as follows: ； The gain of the feedback loop in this control method is K1, the magnitude of which depends on the capacitance and the given voltage. The actual value of K1 is much smaller than unity gain; therefore, the outer loop single proportional coefficient K... p The value is relatively large.

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