CN115694276A - Control method of independent excitation power generation system with outer ring single-proportion adjustment - Google Patents
Control method of independent excitation power generation system with outer ring single-proportion adjustment Download PDFInfo
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Abstract
The invention discloses an independent excitation power generation system control method with outer ring single proportion regulation, when the load in the independent excitation direct current power generation system suddenly increases or suddenly decreases, the capacitance energy error is used as the input given of an outer ring single proportion regulator, the output of the regulator is instantaneous power increment given, the load current increment given is obtained after division operation processing, the actual load current feedback is added, and the excitation current given is converted through the load excitation corresponding relation, thereby realizing voltage stabilization control. The control method provided by the invention solves the problem that the instantaneous power increment is not 0 when the system is in a steady state due to the integral link of the existing capacitance energy balance control outer loop PI regulator, and the obtained energy storage current increment is contradictory to the introduced load current feedback. The optimized setting of the outer ring proportional gain improves the voltage stabilization control dynamic performance and the voltage steady-state precision of the system under the change of the load current, so that the system has good voltage following performance and robustness of the load change.
Description
Technical Field
The invention relates to the technical field of motor control, in particular to a control method of an independent excitation power generation system with an outer ring adjusted in a single proportion mode.
Background
The independent excitation generator comprises an electric excitation motor, a hybrid excitation motor and the like, and the motor has the characteristics that an excitation magnetic field is convenient to adjust, excitation current can be quickly cut off when the generator fails to achieve failure demagnetization, the output voltage is kept stable in a wide rotating speed range and the like, so that the independent excitation generator is widely applied to occasions with high requirements on safety, such as special vehicles, aviation power generation and the like.
The control algorithm of the independent excitation direct-current power generation system is generally Voltage Closed Control (VCC) based on a PI regulator, and a control structure of double closed loops of an excitation current, which adopts an output Voltage, can accelerate the response speed of the excitation current compared with single Voltage loop control. The PI regulator of the voltage ring can ensure the stable-state control precision of the output voltage of the system, but is limited by the fixed PI parameter and the nonlinear reason of the system, and when the system faces load mutation under different working conditions, the dynamic regulation characteristic of the output voltage possibly has the problems of low response speed, large voltage recovery overshoot and the like.
In order to improve the Dynamic Performance of the independent excitation power generation system, the document "Capacitor-Energy-based Control of double salt Brush 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, and the main control concept is as follows: the difference value is obtained by a PI regulator, the expected value of the charging current is added to the load current to obtain the output current of the rectifying circuit, the given value of the exciting current is obtained according to the functional relation between the output current of the rectifying circuit and the exciting current, and the given value is tracked by the actual value of the exciting current through chopping of a half-bridge converter. Compared with the traditional magnetic and voltage regulating method, the control strategy takes the charging current as a control target, improves the performance of the system and reduces the dynamic ripple of the output voltage. However, the output of the PI regulator is composed of a proportional link and an integral link, and the voltage error of the system in a steady state is 0, so in the above control method, the output of the proportional link of the outer-loop PI regulator is zero, if the output of the integral link is also 0 in the steady state of the system, taking load sudden-increase as an example, the waveform of the energy storage of the capacitor when all the loads suddenly increase should be as shown in fig. 4, and only when shaded error areas SL and SH are equal, the integral value of the energy storage error of the integral link after the dynamic state is 0. It shows that, theoretically, the integral link of the control method can bring overshoot to the system, and the overshoot depends on the integral gain coefficient, which is not in accordance with the original intention of the control algorithm itself for improving the dynamic performance of the system.
The outer ring integral loop in the control strategy conflicts with current load introduced by the system, so that the system has steady-state adjustment error, and the dynamic waveform of the output voltage has multiple adjustment processes including overshoot/down adjustment processes. Therefore, in order to further improve the dynamic performance of the system, the setting and optimization steps of the single-proportion gain after the outer ring integral gain is removed need to be considered, so that the whole set of power generation system can rapidly adjust the single-proportion gain of the outer ring to maintain the stability of the output voltage under different working conditions; the method can adapt faster when the system capacitance parameter is mismatched, reduce the sensitivity of the system to the capacitance parameter and improve the control robustness of the system.
In addition, the document "a control method of a hybrid excitation generator (application number: 202110256068.6)" reasonably designs excitation current increase and decrease time to realize primary regulation convergence of output voltage without PI regulation based on a capacitance charge balance thought when load suddenly changes, but the process has control switching from linear control to nonlinear control, so that robustness of system control is reduced; document 202111286479.6 discloses an optimal dynamic PI parameter setting method for a magnetic-regulation and voltage-regulation direct-current generator system, which is a voltage outer ring PI parameter setting method based on a conventional voltage vector control method, wherein an outer ring of the method adopts an output voltage as a control target, a control strategy based on capacitance energy balance adopts a charging current as a control target, and a load current feedforward is introduced on the basis to remove an integral gain in an outer ring PI parameter, so that an overshoot oscillation link caused by the integral gain is reduced compared with the former, and the dynamic response speed of the system is accelerated.
Disclosure of Invention
The invention aims to: as can be known from the control methods proposed in the above background art documents, the integration link of the outer loop PI regulator has little effect on improving the dynamic performance of the system under the change of the load current. Therefore, the invention provides an independent excitation power generation system control method with an outer ring in single proportion regulation, which removes an integral link in a power outer ring, solves the contradiction between the introduction of load current feedback by adopting the single proportion regulation method, provides a system parameter optimization design step and improves the voltage stabilization control dynamic performance and the voltage steady-state precision of the system under the change of load current.
The technical scheme is as follows: in order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the independent excitation power generation system comprises an electric excitation/mixed excitation generator, an excitation current control module, a three-phase diode uncontrolled rectifying circuit, a filter capacitor, a load, an excitation/load current sensor and an output voltage sensor. The three-phase diode uncontrolled rectifying circuit comprises three parallel bridge arms, and each bridge arm is formed by connecting two diodes in series; the middle points of the three bridge arms are respectively connected with one end of a three-phase armature winding of the independent excitation generator, and the other end of the three-phase armature winding is in short circuit; the three-phase diode uncontrolled rectifying circuit is sequentially connected with the filter capacitor, the output voltage sensor and the load in parallel, and the load is connected with the load current sensor in series; the excitation current control module comprises a single-phase full-bridge converter and an excitation winding voltage source; the single-phase full-bridge converter is powered by an excitation winding voltage source and comprises two parallel bridge arms, each bridge arm consists of two switching tubes, and an excitation winding and an excitation current sensor are connected between the midpoints of the two switching tubes. The method is characterized in that the method for controlling the independent excitation power generation system with the outer ring single proportion adjusted comprises the following specific steps:
step S1, the generator operates at different rotating speeds, and different load currents i in the steady state of the power generation system are recorded o Corresponding exciting current value i f Fitting the load current i at different rotating speeds n by a least square method o And a value of excitation current i f The relational expression of (1);
step S2, solving the exciting current value i of the independent exciting power generation system under the condition of different constant rotating speed steady-state operation by the fitting relational expression in the step S1 f And the load current i o K of the fitting coefficient betweenThe characterization fit relationship is as follows:
wherein a, b, c and d represent polynomial coefficients, and the average value i of the pre-stage trimming current of the filter capacitor recav Is equal to i o ；
S3, outputting the error of the capacitor energy storage corresponding to the capacitor energy storage disturbed by the load and the reference voltage setting as the instantaneous power increment setting after single-proportion regulation
Dividing the instantaneous power increment set value by the disturbed output voltage u o Obtaining the specified value of the increment of the energy storage current
The energy storage current increment is used for superposing the load feedback current i with the specified value o As command value of rectified current
Then converting according to the fitting coefficient K given by the step S2 to obtain given exciting current
S4, determining the excitation resistance R of the excitation winding f And excitation inductance L f And performing PI parameter setting on the inner ring of the exciting current according to the given value of the exciting current obtained in the step S3 to realize output end voltage stabilization control.
Further, the control system parameter optimization design process in step S3 is as follows:
step S3.1, outputting the voltage u o Multiplying by a feedback factor K 1 ' with a given reference voltage u o * Multiplying by a feedback factor K 1 Making difference, because the square term of the output voltage exists in the energy feedback link, the feedback coefficient K is calculated 1 ' and K 1 Equivalent to a fixed gain tableShown below:
wherein C is the capacitance value of the filter capacitor;
step S3.2, multiplying the difference result by a single-scale adjustment coefficient K for approximate processing p Obtaining instantaneous power increment given
The instantaneous power increment is given by the output voltage u o Equivalent to a given instantaneous power increment multiplied by a fixed gain K 2 As a specified value of energy storage current increment
K 2 Is represented as follows:
the energy storage current after feedback passes through a transfer function module G c (s) to an output voltage u o (s)，G c (s) the expression is as follows:
further, the process of optimally designing the parameters of the control system in step S4 is as follows:
step S4.1, the excitation current loop structure open loop transfer function is expressed as:
to implement zero-pole cancellation, a suitable current loop bandwidth ω is determined f Select k p 、k i The parameters are as follows:
the closed loop transfer function of the excitation current loop with the reduced order as a first-order inertia system is obtained as follows:
step S4.2, the simplified transfer function from load disturbance to output is given as:
the gain of the feedback loop of the control method is K 1 The magnitude of which depends on the capacitance of the capacitor and on the value of a given voltage, K 1 The actual value is much smaller than unity, so the outer loop single scale factor K p The value is large.
Further, the outer ring single proportionality coefficient K p The specific setting steps are as follows:
s5, solving a load current I according to a state equation of the capacitor voltage at the output end o1 To I o3 A time function expression of an ideal optimal output voltage curve under the condition of mutation;
step S6, according to the idea of capacitance charge balance, the specific load current I under any rotating speed n o1 To I o3 Using the excitation current i fitted in S1 f Load current i o Solving the optimal outer ring single proportionality coefficient K by the relation of the rotating speed n p 。
Further, the time function expression of the ideal optimal output voltage curve under the condition of load sudden change in the step S5 is obtained as follows:
s5.1, converting a state equation of the capacitor voltage at the load end into a first-order differential equation:
wherein C is the capacitance of the filter capacitor, Z is the equivalent impedance of the load end, i rec For the rectified current of the preceding stage of the filter capacitor, i in steady-state conditions rec Is equal to i o ；
Step S5.2, for the load current I o1 To I o3 Let Z be the equivalent impedance after mutation, use
Is represented by u o * For the given value of the output voltage, solving a first order differential equation to obtain:
moment t of sudden change of load 0 Considering as 0, the above formula is simplified as:
rectified current i of filter capacitor front stage rec By exciting current i f And (4) direct control. Excitation winding self-inductance L f Larger, when the full-bridge switch tube outputs full duty ratio, the exciting current i f Linear up or down, slope and self-inductance value L f And (4) correlating. Irrespective of the saturation of the magnetic field, see i rec With i f Linearly rising or falling with a rising slope of k 1 The falling slope is-k 1 ；
Step S5.3, according to the idea of capacitance charge balance, rectifying current i after sudden load current increase under ideal conditions rec Should follow the excitation current i f Linear rise, expressed as a function of time: i.e. i rec ＝k 1 t+I o1 Time function and t at the decreasing stage of the exciting current 2 Associated with time, let t 2 = x, the decreasing expression is: i' rec ＝-k 1 t + b at t 2 Time of day is composed of rec ＝i' rec Result in b =2k 1 x+I o1 . Then the current i is rectified rec The segmentation is represented as:
ideal load jump end time t 3 According to t>I at x rec Expression, and value I before and after sudden change of load current o1 And I o3 Expressed as:
step S5.4, rectifying current i expressed by segments rec Substituting into the output voltage expression in step S5.2 and simplifying, the ideal piecewise time function of the output voltage is expressed as:
further, the load current is suddenly reduced and then the current i is rectified rec The segmentation is represented as:
in the formula k 1 The sign is inverted, and the rest derivation processes are unchanged.
Further, the load current in the step S6 is represented by I o1 To I o3 Optimal outer loop single proportionality coefficient K under mutation p The calculation process is as follows:
step S6.1, the relevant time node t of the ideal dynamic waveform in the step S5.3 is obtained 1 、t 2 、t 3 (ii) a Let the output voltage u in step S5.4 o 0 in the expression<t<T is obtained by derivation of x segment to time and solving for the derivative as 0 1 ：
Step S6.2, according to the idea of capacitance charge balance, having S A ＝S B +S C In which S is A Comprises the following steps:
wherein the time t 1 Known as u o And i rec Is the first segment of the two piecewise functions in steps S5.3 and S5.4, S B +S C Expressed as:
order S A ＝S B +S C I.e. a single unknown quantity x is solved, the time t 2 ，t 3 Can be obtained according to the following formula:
step 6.3, obtaining the secondary load current I o1 To I o3 Optimal outer ring single scale coefficient K corresponding to mutation p Then, K is obtained from the following formula p ：
By adopting the technical scheme of the invention, the beneficial effects can be realized as follows:
(1) The control method of the independent excitation power generation system based on the single-proportion adjustment of the capacitor energy balance outer ring provided by the invention performs the single-proportion control on the capacitor energy storage outer ring on the basis of keeping the exciting current inner ring, and an integral link is removed, so that the contradiction caused by introducing the load current feedback is avoided. Therefore, steady-state errors do not exist after the dynamic process of the system is finished, and the dynamic performance of the system under sudden load change is improved.
(2) The control strategy provided by the invention can adjust the outer ring single-proportion regulating coefficient according to the capacitance parameter, and the optimal outer ring single-proportion gain coefficient is adjusted through the capacitance charge balance control idea, so that the system dynamic response speed is higher, the inhibition capability on load disturbance is strong, the influence of capacitance parameter mismatch is small, and the overall robustness is strong.
(3) Compared with the traditional voltage closed-loop control algorithm, the control strategy provided by the invention has stronger adaptability to load step disturbance under different working conditions, a load step response result close to critical damping can be obtained more easily after parameter optimization, the output voltage is recovered quickly, and the dynamic performance is excellent.
Drawings
FIG. 1 is a hardware structure diagram of an independent excitation power generation system provided by the present invention;
FIG. 2 is a control structure diagram of an outer ring single-scale regulated independent excitation power generation system;
FIG. 3 is a diagram of a current loop of an excitation control module;
FIG. 4 is a diagram of a typical output voltage waveform under sudden load change;
FIG. 5 is a control schematic diagram of an outer ring single-proportion regulated independent excitation power generation system;
FIG. 6 shows ideal waveforms of output voltage, load current, and rectified current corresponding to a sudden increase in load current;
FIG. 7 is a block diagram of a conventional voltage-current dual closed loop control;
FIG. 8 is a graph of unit step response results from load disturbances to output voltage after adding an integration element;
FIG. 9 is a graph of unit step response results from load disturbances to output voltage for different single scaling factors;
FIG. 10 is a graph comparing conventional voltage vector control with the control voltage response waveform of the present invention during a load disturbance.
Detailed Description
In order to make the objects, technical solutions and features of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 5 is a control schematic diagram of an independent excitation power generation system based on capacitance energy balance outer ring single-proportion adjustment, and a hardware system topology applied to the independent excitation power generation system is shown in fig. 1. The system comprises an electric excitation/mixed excitation generator, an excitation current control module, a three-phase diode uncontrolled rectifying circuit, a filter capacitor, a load, an excitation/load current sensor and an output voltage sensor. The three-phase diode uncontrolled rectifying circuit comprises three parallel bridge arms, and each bridge arm is formed by connecting two diodes in series; the middle points of the three bridge arms are respectively connected with one end of a three-phase armature winding of the independent excitation generator, and the other end of the three-phase armature winding is in short circuit; the three-phase diode uncontrolled rectifying circuit is sequentially connected with the filter capacitor, the output voltage sensor and the load in parallel, and the load is connected with the load current sensor in series; the excitation current control module comprises a single-phase full-bridge converter and an excitation winding voltage source; the single-phase full-bridge converter is powered by an excitation winding voltage source and comprises two parallel bridge arms, each bridge arm consists of two switching tubes, and an excitation winding and an excitation current sensor are connected between the midpoints of the two switching tubes.
The invention provides an independent excitation power generation system control method based on capacitance energy balance outer ring single proportion regulation, which comprises the following specific implementation steps:
step S1, the generator operates at different rotating speeds, and different load currents i in the steady state of the power generation system are recorded o Corresponding exciting current value i f Fitting load current i at different rotating speeds n by a least square method o And the value of excitation current i f The relational expression of (1);
step S2, solving the excitation current value i of the independent excitation power generation system under the condition of different constant rotating speed steady-state operation by the fitting relation in the step S1 f And the load current i o A fitting coefficient K between, the fitting coefficient characterizing the fitting relationIs as follows:
wherein a, b, c and d represent polynomial coefficients, and the average value i of the pre-stage trimming current of the filter capacitor recav Is equal to i o ；
S3, outputting the error of the capacitor energy storage corresponding to the capacitor energy storage disturbed by the load and the reference voltage setting as the instantaneous power increment setting after single proportion adjustment
Dividing the instantaneous power increment set value by the disturbed output voltage u o Obtaining the specified value of the increment of the energy storage current
The energy storage current increment is used for superposing the load feedback current i with the specified value o As command value of rectified current
Then converting according to the fitting coefficient K given by the step S2 to obtain given exciting current
S4, determining the excitation resistance R of the excitation winding f And excitation inductance L f And performing PI parameter setting on the inner ring of the exciting current according to the given value of the exciting current obtained in the step S3 to realize output end voltage stabilization control.
Specifically, the process of optimally designing the parameters of the control system in step S3 is as follows:
step S3.1, outputting the voltage u o Multiplying by a feedback factor K 1 ' with a given reference voltage u o * Multiplying by a feedback factor K 1 Making difference, because the square term of the output voltage exists in the energy feedback link, the feedback coefficient K is calculated 1 ' and K 1 The equivalent is a fixed gain expressed as follows:
wherein C is the capacitance value of the filter capacitor;
step S3.2, multiplying the difference result by a single-scale adjustment coefficient K for approximate processing p Obtaining instantaneous power increment given
The instantaneous power increment is given by the output voltage u o Equivalent to a given instantaneous power increment multiplied by a fixed gain K 2 As a specified value of energy storage current increment
K 2 Is represented as follows:
the energy storage current after feedback passes through a transfer function module G c (s) to an output voltage u o (s)，G c (s) the expression is as follows:
specifically, the control system parameter optimization design process in step S4 is as follows:
step S4.1, the excitation current loop structure open loop transfer function is expressed as:
to achieve pole-zero cancellation, a suitable current loop bandwidth ω is determined f Select k p 、k i The parameters are as follows:
the closed loop transfer function of the excitation current loop with the order reduced to be a first-order inertia system is obtained as follows:
step S4.2, the simplified transfer function from load disturbance to output is given as:
the gain of the feedback loop of the control method is K 1 The magnitude of which depends on the capacitance of the capacitor and on the value of a given voltage, K 1 The actual value is much smaller than the unity gain, so the outer loop single scale factor K p The value is large.
In particular, the outer ring single proportionality coefficient K p The specific setting steps are as follows:
s5, solving a load current I according to a state equation of the capacitor voltage at the output end o1 To I o3 A time function expression of an ideal optimal output voltage curve under a sudden change condition;
step S6, according to the idea of capacitance charge balance, the specific load current I under any rotating speed n o1 To I o3 Using the excitation current i fitted in S1 f Load current i o Solving the optimal outer ring single proportionality coefficient K by the relation of the rotating speed n p 。
Specifically, the time function expression of the ideal optimal output voltage curve under the condition of load sudden change in the step S5 is obtained as follows:
step S5.1, converting the state equation of the capacitance voltage of the load end into a first-order differential equation:
wherein C is the capacitance value of the filter capacitor, Z is the equivalent impedance of the load end, i rec For the rectified current of the preceding stage of the filter capacitor, i in steady-state conditions rec Is equal to i o ；
Step S5.2, for the load current I o1 To I o3 Let Z be the equivalent impedance after mutation, use
Is represented by the formula (I) in which u o * For the given value of the output voltage, solving a first order differential equation to obtain:
moment t of sudden change of load 0 Considering as 0, the above formula is simplified as:
rectified current i of filter capacitor front stage rec By excitation current i f And (4) directly controlling. Self-inductance L of excitation winding f Larger, when the full-bridge switch tube outputs full duty ratio, the exciting current i f Linear up or down, slope and self-inductance value L f And (4) correlating. Irrespective of the saturation of the magnetic field, see i rec With i f Linearly rising or falling with a rising slope of k 1 The falling slope is-k 1 ；
Step S5.3, according to the idea of capacitance charge balance, rectifying current i after sudden load current increase under ideal conditions rec Should follow the excitation current i f Linear rise, expressed as a function of time: i all right angle rec ＝k 1 t+I o1 Time function and t at the decreasing stage of the exciting current 2 About time, set t 2 = x, the decreasing expression is: i' rec ＝-k 1 t + b at t 2 Time of day is composed of rec ＝i' rec Result in b =2k 1 x+I o1 . Then the current i is rectified rec The segmentation is represented as:
ideal load jump end time t 3 According to t>I at x rec Expression, and value I before and after sudden change of load current o1 And I o3 Expressed as:
step S5.4, rectifying current i expressed by segments rec Substituting into the output voltage expression in step S5.2 and simplifying, the ideal piecewise time function of the output voltage is expressed as:
specifically, the load current is suddenly reduced and then the rectified current i rec The segmentation is represented as:
in the formula k 1 The sign is inverted, and the rest derivation processes are unchanged.
Specifically, the load current in step S6 is represented by I o1 To I o3 Optimal outer loop single proportionality coefficient K under mutation p The calculation process is as follows:
step S6.1, the relevant time node t of the ideal dynamic waveform in the step S5.3 is obtained 1 、t 2 、t 3 (ii) a Let the output voltage u in step S5.4 o 0 in the expression<t<T is obtained by differentiating the time by the x section and making the derivative be 0 1 ：
Step S6.2, according to the idea of capacitance charge balance, having S A ＝S B +S C In which S is A Comprises the following steps:
wherein the time t 1 Known as u o And i rec Is the first segment of the two piecewise functions of steps S5.3 and S5.4, S B +S C Expressed as:
order S A ＝S B +S C I.e. a single unknown quantity x is solved, the time t 2 ，t 3 The following equation can be obtained:
step 6.3, obtaining the secondary load current I o1 To I o3 Optimal outer ring single proportionality coefficient K corresponding to mutation p Then, K is obtained from the following formula p ：
A traditional voltage-current double closed loop block diagram is shown in fig. 7, and the control structure of the double closed loop can increase the response speed of the exciting current compared with the single voltage loop control. However, due to the fixed PI parameters and the nonlinearity of the system itself, when the system is subjected to sudden load changes under different working conditions, the dynamic regulation characteristic of the output voltage may have the problems of slow response speed, large voltage recovery overshoot and the like. Therefore, the voltage error input of the traditional outer loop PI regulator is replaced by the capacitive energy storage error input. So that better control effect is obtained in the aspect of improving the dynamic performance of the system.
The output of the outer ring PI regulator in the generator control method based on charge-discharge energy control proposed by the existing literature is composed of a proportional link and an integral link, and the voltage error of the system in a steady state is 0, so the output of the outer ring PI regulator in the control method is zero, if the output of the integral link is required to be 0 in the system steady state, taking load sudden increase as an example, the waveform of the capacitor energy storage when all loads suddenly increase should be as shown in FIG. 4, and the integral value of the integral link to the energy storage error is 0 after the dynamic state is finished only when the shaded error areas SL and SH are equal. This shows that, theoretically, the integral link of the above control method will bring overshoot to the system certainly, and the overshoot depends on the integral gain coefficient, which is not in accordance with the original intention of the control algorithm itself to improve the dynamic performance of the system.
In addition, the integral gain introduced by the control method is contradictory to the load current feedback introduced by the system, if the integral gain coefficient K is introduced into the outer ring of the system I Different integral gain coefficient K I The unit step response results of the corresponding load disturbance to the output voltage are shown in fig. 8. After the outer loop control introduces the integral gain, the system can slowly adjust the existing steady-state error after the dynamic process is finished, and the integral gain coefficient K I The change in a certain range does not help to improve the dynamic performance of the step response of the system, and serious overshoot can be caused when the value is too large.
The integral gain link is removed, and only a single proportional gain coefficient K is arranged in an outer ring p Under the condition, the unit step response result of the system from load disturbance to output voltage under different single proportional adjustment coefficients is shown in fig. 9, and the integral gain coefficient K can be seen I K when =0 p The larger the value is, the faster the dynamic response speed is, but the dynamic response speed cannot be too large, otherwise, the overshoot phenomenon can occur. And it can be found that when K I When =0, the gain factor K follows the single scale p The system has no steady-state error when the dynamic process is finished, and the dynamic response speed is high.
Compared with the conventional voltage vector control method for setting PI based on the capacitance charge balance thought, the voltage stabilization effect of setting the outer ring single proportional gain coefficient by taking the charging current as the control target is different, as shown in figure 10, under the condition of the same load sudden change, the control method provided by the invention can achieve the voltage stabilization effect more quickly compared with the conventional voltage vector control method, and is almost free of overshoot, high in dynamic response speed and strong in load disturbance resistance adaptability.
In conclusion, the control method of the independent excitation power generation system based on the capacitor energy balance outer ring single-proportion regulation solves the problems of slow dynamic regulation, static error and the like caused by the integral gain of the outer ring, and compared with the traditional voltage vector control, the voltage stabilization control dynamic performance and the voltage steady-state precision of the system under the change of the load current are improved.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (6)
1. A control method of an independent excitation power generation system with an outer ring adjusted in a single proportion is characterized by comprising the following specific steps:
step S1, the generator runs at different rotating speeds, and different load currents i in the steady state of the independent excitation power generation system are recorded o Corresponding exciting current value i f Fitting the load current i at different rotation speeds n o And the value of excitation current i f The relational expression of (1);
step S2, solving the excitation current value i of the independent excitation power generation system under the condition of different constant rotating speed steady-state operation by the fitting relation in the step S1 f And the load current i o A fitting coefficient K between;
s3, outputting the error of the capacitor energy storage corresponding to the capacitor energy storage disturbed by the load and the reference voltage setting as the instantaneous power increment setting after single proportion adjustment
Dividing the instantaneous power increment set value by the disturbed output voltage u o Obtaining the specified value of the increment of the energy storage current
The energy storage current increment is used for superposing the load feedback current i with the specified value o As command value of rectified current
Then converting according to the fitting coefficient K given in the step S2 to obtain given exciting current
Step S4, determining excitation resistance R of excitation winding f And excitation inductance L f And performing PI parameter setting on the inner ring of the exciting current according to the given value of the exciting current obtained in the step S3 to realize output end voltage stabilization control.
2. The method for controlling an independent excitation power generation system with single-proportion adjustment of an outer ring according to claim 1, wherein the control system parameter optimization design process in the step S3 is as follows:
step S3.1, outputting the voltage u o Multiplying by a feedback factor K 1 ' with a given reference voltage u o * Multiplying by a feedback factor K 1 Making difference, because the energy feedback link has square term of output voltage, the feedback coefficient K is calculated 1 ' and K 1 The equivalent is a fixed gain expressed as follows:
wherein C is the capacitance value of the filter capacitor;
step S3.2, multiplying the difference result by a single-scale adjustment coefficient K for approximate processing p Obtaining instantaneous power increment given
The instantaneous power increment is given by the output voltage u o Equivalent to a given instantaneous power increment multiplied by a fixed gain K 2 As a specified value of energy storage current increment
K 2 Is represented as follows:
the energy storage current after feedback passes through a transfer function module G c (s) to an output voltage u o (s)，G c (s) the expression is as follows:
3. the method for controlling an independent excitation power generation system with single-proportion adjustment of an outer ring according to claim 2, wherein the control system parameter optimization design process in the 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 ω is determined f Selecting k p 、k i The parameters are as follows:
the closed loop transfer function of the excitation current loop with the order reduced to be a first-order inertia system is obtained as follows:
step S4.2, the simplified transfer function from load disturbance to output is given as:
the gain of a feedback loop of the control method is K 1 The magnitude of which depends on the capacitance of the capacitor and on a given voltage value, K 1 The actual value is much smaller than the unity gain, so the outer loop single scale factor K p The value is large.
4. The method of claim 3, wherein the outer ring single scale factor K is a single scale factor of the outer ring p The specific setting steps are as follows:
s5, solving a load current I according to a state equation of the capacitor voltage at the output end o1 To I o3 A time function expression of an ideal optimal output voltage curve under a sudden change condition;
step S6, according to the idea of capacitance charge balance, the specific load current I under any rotating speed n o1 To I o3 Using the excitation current i fitted in S1 f Load current i o Solving the optimal outer ring single proportionality coefficient K by the relation of the rotating speed n p 。
5. The method for controlling an independent excitation power generation system with single-proportion adjustment of an outer ring according to claim 4, wherein the time function expression of the ideal optimal output voltage curve under the condition of sudden load change in the step S5 is obtained as follows:
step S5.1, converting the state equation of the capacitance voltage of the load end into a first-order differential equation:
wherein C is the capacitance of the filter capacitor, Z is the equivalent impedance of the load end, i rec For the rectified current of the preceding stage of the filter capacitor, i in steady-state conditions rec Is equal to i o ；
Step S5.2, for the load current I o1 To I o3 Let Z be the equivalent impedance after mutation, use
Is represented by the formula (I) in which u o * For the given value of the output voltage, solving a first order differential equation to obtain:
moment t of sudden change of load 0 Considering as 0, the above formula is simplified as:
rectified current i of filter capacitor front stage rec By exciting current i f Direct control; irrespective of the saturation of the magnetic field, see i rec With i f Linear change with slope k 1 ；
Step S5.3, according to the idea of capacitance charge balance, under ideal conditions, the load current is suddenly changed into the rectified current i rec The segmentation is represented as:
ideal load jump end time t 3 According to t>I at x rec Expression, and value I before and after sudden change of load current o1 And I o3 Expressed as:
step S5.4, rectifying current i expressed by segments rec Substituting into the output voltage expression in step S5.2 and simplifying, the ideal piecewise time function of the output voltage is expressed as:
6. the method as claimed in claim 5, wherein the load current in step S6 is controlled by I o1 To I o3 Optimal outer loop single proportionality coefficient K under mutation p The calculation process is as follows:
step S6.1, the relevant time node t of the ideal dynamic waveform in the step S5.3 is obtained 1 、t 2 、t 3 (ii) a Let the voltage u be output in step S5.4 o 0 in the expression<t<T is obtained by derivation of x segment to time and solving for the derivative as 0 1 ：
Step S6.2, according to the idea of capacitance charge balance, having S A ＝S B +S C In which S is A Comprises the following steps:
wherein the time t 1 Known as u o And i rec Is the first segment of the two piecewise functions in steps S5.3 and S5.4, S B +S C Expressed as:
order S A ＝S B +S C I.e. a single unknown quantity x is solved, the time t 2 ，t 3 Can be obtained according to the following formula:
step 6.3, the secondary load current I is obtained o1 To I o3 Optimal outer ring single proportionality coefficient K corresponding to mutation p Then, K is obtained from the following formula p ：
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