Static error-free APF current inner loop control system and control method

Abstract

The embodiment of the invention provides a static-error-free APF current inner loop control system and a static-error-free APF current inner loop control method. An output current sampling signal of a current control period and an output current signal, predicted in a previous period, of the current control period form a correction current according to a specific proportion; generating a current prediction signal of the next period by using the correction current; a voltage signal is further generated; and meanwhile, an error compensation signal is generated by utilizing the correction current, and is added with the voltage signal to obtain a voltage control signal to be input into the PWM modulation module to drive the APF. According to the scheme, APF control without delay dynamic tracking can be realized, steady-state errors of current tracking caused by system parameter deviation can be solved, and the accuracy and reliability of control are improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of active power filtering, and in particular to an APF current inner loop control system and control method without static error. Background Art

[0002] In new power systems, high-order harmonics are increasing day by day. Although the traditional APF current control method is qualified in suppressing low-order harmonics in the power grid, the compensation of high-order harmonics requires the current loop to have an extremely high bandwidth, which is difficult to achieve with the traditional APF current control method.

[0003] In this regard, the present invention proposes a static error-free APF current inner loop control system and control method. The method uses the output current sampling signal of the current control cycle and the output current signal of the current control cycle predicted in the previous cycle to form a correction current in a specific ratio; then uses the correction current to generate the current prediction signal of the next cycle; and then generates a voltage signal; and at the same time uses the correction current to generate an error compensation signal, and adds it to the voltage signal to obtain a voltage control signal input to the PWM modulation module to drive the APF.

[0004] This solution can not only realize APF control with dynamic tracking without delay, but also solve the steady-state error of current tracking caused by parameter deviation. Summary of the invention

[0005] The present invention provides an APF current inner loop control system and control method without static error, wherein the output current sampling signal of the current control cycle and the output current signal of the current control cycle predicted in the previous cycle are used to form a correction current according to a specific ratio; the correction current is then used to generate the current prediction signal of the next cycle; and a voltage signal is then generated based on this; and the correction current is used to generate an error compensation signal at the same time, and the error compensation signal is added to the voltage signal to obtain a voltage control signal input to a PWM modulation module to drive the APF. The APF control without delay dynamic tracking can be realized, and the steady-state error of current tracking caused by system parameter deviation can be solved, thereby improving the accuracy and reliability of control.

[0006] In a first aspect, an embodiment of the present invention provides an APF current inner loop control system without static error, including a voltage acquisition module, a current acquisition module, a voltage prediction module, a current prediction module, a voltage generation module, a PWM generation module, an error compensation module and an actual circuit;

[0007] The input end of the voltage acquisition module is connected to the common coupling point of the actual circuit, and the output end of the voltage acquisition module is respectively connected to the input end of the voltage prediction module and the input end of the current prediction module; the input end of the current acquisition module is connected to the filter inductor of the actual circuit, and the output end of the current acquisition module is connected to the input end of the current prediction module; the input end of the current prediction module is also connected to the output end of the delay module; the output end of the current prediction module is respectively connected to the input end of the error compensation module and the input end of the voltage generation module; the input of the voltage generation module is also used to receive an external compensation current instruction and the output of the voltage prediction module; the error compensation module also includes a compensation current instruction input end for receiving an external compensation current instruction; the output of the voltage generation module is added to the output of the error compensation module, and then connected to the limit module, the delay module and the PWM generation module in sequence; the output end of the PWM generation module is connected to the APF inverter in the actual circuit as the output end of the control module;

[0008] The voltage acquisition module is used to acquire the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmit the voltage sampling signal to the voltage prediction module and the current prediction module; the voltage prediction module is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and output the voltage prediction signal to the voltage generation module; the current acquisition module is used to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmit the current sampling signal to the current prediction module; the current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and use the correction current, the current sampling signal signal, the voltage sampling signal and the output signal of the delay module to obtain a current prediction signal, and output the current prediction signal to the voltage generation module and the error compensation module; the error compensation module is used to obtain an error compensation signal according to the compensation current instruction and the output of the current prediction module; the voltage generation module is used to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the voltage signal and the error compensation signal are added to obtain a voltage control signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module; the PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.

[0009] Optionally, the discrete control model of the actual circuit is:

[0010]

[0011] Among them, Ts is the preset sampling period, ω0 is the rated angular frequency, L1 is the filter inductance, R1 is the parasitic resistance in the actual circuit, A and B are constants, ud(k) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k, and uq(k) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k; udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, and uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k; iLd(k) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k, and iLq(k) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k; iLd(k+1) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k+1, and iLq(k+1) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k+1.

[0012] Optionally, the core control equation of the voltage prediction module is:

[0013]

[0014] Among them, udpcc_p(k+1) is the d-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, uqpcc_p(k+1) is the q-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, udpcc(k-1) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system with a k-1 period, and uqpcc(k-1) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system with a k-1 period.

[0015] Optionally, the core control equation of the current prediction module is:

[0016]

[0017] Among them, idp(k+1) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1, iqp(k+1) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1, idp(k) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system at time k, iqp(k) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system at time k; ud(k) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k, uq(k) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k; udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k; iLd(k) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k, and iLq(k) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k.

[0018] Optionally, the core control equation of the error compensation module is:

[0019] Among them, ud_cor(k+1) is the d-axis component of the error compensation signal, uq_cor(k+1) is the p-axis component of the error compensation signal, Bp is the parameter estimation value of B, Bp-1 represents the reciprocal of Bp, and X3 is the compensation coefficient.

[0020] In a second aspect, the present invention further provides an APF current inner loop control method without static error, which is applied to any APF current inner loop control system without static error described in the first aspect of the present invention, comprising:

[0021] Using the voltage acquisition module to acquire the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmitting the voltage sampling signal to the voltage prediction module and the current prediction module;

[0022] Using the voltage prediction module to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and outputting the voltage prediction signal to the voltage generation module;

[0023] Using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmitting the current sampling signal to the current prediction module;

[0024] Using the current prediction module to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module to obtain a current prediction signal, and output the current prediction signal to the voltage generation module and the error compensation module;

[0025] Using the error compensation module to obtain an error compensation signal according to the compensation current instruction and the output of the current prediction module;

[0026] The voltage generation module is used to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the voltage signal and the error compensation signal are added to obtain a voltage control signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module;

[0027] The PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.

[0028] Optionally, after the voltage value of the common coupling point of the actual circuit is collected by the voltage collection module to obtain a voltage sampling signal, before the voltage sampling signal is transmitted to the voltage prediction module and the current prediction module, the method further includes:

[0029] Based on the formula Convert the three-phase output voltage of the common coupling point into a voltage on a synchronous rotating coordinate system; wherein θ represents the rotation angle of the synchronous rotating coordinate system, udpcc and uqpcc represent the d-axis and q-axis components of the common coupling point voltage in the synchronous rotating coordinate system, respectively, and upcc_a, upcc_b and upcc_c represent the three-phase output voltage;

[0030] After using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, before transmitting the current sampling signal to the current prediction module, it also includes:

[0031] Based on the formula The three-phase output current of the filter inductor is converted into a current on a synchronous rotating coordinate system; wherein iLd and iLq respectively represent the d-axis and q-axis components of the three-phase output current in the synchronous rotating coordinate system, and iLa, iLb and iLc represent the three-phase output current.

[0032] Optionally, using the voltage prediction module to obtain a voltage prediction signal according to the voltage sampling signal at the current moment includes:

[0033] The voltage prediction module is used according to the voltage sampling signal at the current moment, based on the formula A voltage prediction signal is obtained.

[0034] Optionally, obtaining a current prediction signal by using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module includes:

[0035] Using the current prediction module, based on the formula

[0036] The d-axis component idp(k+1) and the q-axis component iqp(k+1) of the current prediction signal in the synchronous rotating coordinate system at the next acquisition moment are obtained; wherein, is the correction current expression, and X1 represents the proportion of the actual current and the predicted current in the correction current.

[0037] Optionally, using the voltage generation module to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction includes:

[0038] By using the voltage generation module, according to the current prediction signal, the voltage prediction signal and the compensation current instruction, based on the formula A voltage signal is obtained; wherein ud(k+1) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1, and uq(k+1) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1; udpcc_p(k+1) is the d-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, and uqpcc_p(k+1) is the q-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1; idref(k) is the d-axis component of the compensation current command in the synchronous rotating coordinate system at time k, and iq ref(k) is the q-axis component of the compensation current command in the synchronous rotating coordinate system at time k, idref(k-1) is the d-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period, iqref(k-1) is the q-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period; idp(k+1) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system of k+1 time, iqp(k+1) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system of k+1 time; Bp is the parameter estimation value of B, Bp -1 It is the reciprocal of Bp; X2 represents the ratio of the current prediction signal to the compensation current command.

[0039] An embodiment of the present invention provides an APF current inner loop control system and control method without static error, the system comprising a control module and an actual circuit; the control module comprising a voltage acquisition module, a current acquisition module, a voltage prediction module, a current prediction module, a voltage generation module, a limit module, a delay module, an error compensation module and a PWM generation module; the actual circuit comprises an APF inverter and a filter inductor, the APF inverter and the filter inductor are connected in series and connected to the grid side; the input end of the voltage acquisition module is connected to the common coupling point of the actual circuit, the output end of the voltage acquisition module is respectively connected to the input end of the voltage prediction module and the input end of the current prediction module; the input end of the current acquisition module The output end of the current acquisition module is connected to the input end of the current prediction module; the input end of the current prediction module is also connected to the output end of the delay module; the output end of the current prediction module is respectively connected to the input end of the error compensation module and the input end of the voltage generation module; the input of the voltage generation module is also used to receive the external compensation current instruction and the output of the voltage prediction module; the error compensation module also includes a compensation current instruction input end for receiving the external compensation current instruction; the output of the voltage generation module is added to the output of the error compensation module, and then connected to the limit module, the delay module and the PWM generation module in turn; the output end of the PWM generation module is used as the control module The output end is connected to the APF inverter in the actual circuit; the voltage acquisition module is used to collect the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmit the voltage sampling signal to the voltage prediction module and the current prediction module; the voltage prediction module is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and output the voltage prediction signal to the voltage generation module; the current acquisition module is used to collect the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmit the current sampling signal to the current prediction module; the current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and A current prediction signal is obtained by using the correction current, current sampling signal, voltage sampling signal and the output signal of the delay module, and the current prediction signal is output to the voltage generation module and the error compensation module; the error compensation module is used to obtain the error compensation signal according to the compensation current instruction and the output of the current prediction module; the voltage generation module is used to obtain the voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the voltage control signal is obtained by adding the voltage signal and the error compensation signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module; the PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.The above technical solution uses the output current sampling signal of the current control cycle and the output current signal of the current control cycle predicted in the previous cycle to form a correction current in a specific ratio; then uses the correction current to generate the current prediction signal of the next cycle; and then generates a voltage signal; and at the same time uses the correction current to generate an error compensation signal, and adds it to the voltage signal to obtain a voltage control signal input to the PWM modulation module to drive the APF. This solution can not only realize APF control with dynamic tracking without delay, but also solve the steady-state error of current tracking caused by system parameter deviation, thereby improving the accuracy and reliability of control. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of an APF current inner loop control system without static error provided by an embodiment of the present invention;

[0041] Figure 2 It is a practical circuit topology diagram provided by an embodiment of the present invention;

[0042] Figure 3 It is a flow chart of an APF current inner loop control method without static error provided by an embodiment of the present invention;

[0043] Figure 4 It is the current change following curve diagram under the APF current inner loop without net difference control method without static error;

[0044] Figure 5 It is a current variation following curve diagram of the prior art. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0046] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the directional words such as "upper", "lower", "left", "right" and the like described in the embodiments of the present invention are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present invention. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes and do not represent any order, quantity or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0047] The term “including” and its variations used in the present invention are open inclusions, that is, “including but not limited to.” The term “based on” means “based at least in part on.” The term “one embodiment” means “at least one embodiment.”

[0048] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or interdependence.

[0049] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0050] Figure 1 Schematic diagram of the structure of an APF current inner loop control system without static error provided by an embodiment of the present invention. Figure 2 This is a practical circuit topology diagram provided by an embodiment of the present invention, refer to Figure 1 , Figure 2 The system includes a control module and an actual circuit; the control module includes a voltage acquisition module 10, a current acquisition module 20, a voltage prediction module 30, a current prediction module 40, a voltage generation module 50, a limit module 80, a delay module 90, an error compensation module 100 and a PWM generation module 60; the actual circuit includes an APF inverter 71 and a filter inductor 72, and the APF inverter 71 and the filter inductor 72 are connected in series and connected to the grid side Grid;

[0051] The input end of the voltage acquisition module 10 is connected to the common coupling point of the actual circuit, and the output end of the voltage acquisition module 10 is respectively connected to the input end of the voltage prediction module 30 and the input end of the current prediction module 40; the input end of the current acquisition module 20 is connected to the filter inductor 72 of the actual circuit, and the output end of the current acquisition module 20 is connected to the input end of the current prediction module 40; the input end of the current prediction module 40 is also connected to the output end of the delay module; the output end of the current prediction module 40 is respectively connected to the input end of the error compensation module and the input end of the voltage generation module 50; the input of the voltage generation module 50 is also used for The output of the voltage prediction module 30 receives the external compensation current command and the output of the voltage prediction module 30; the error compensation module also includes a compensation current command input terminal for receiving the external compensation current command; the output of the voltage generation module 50 is added to the output of the error compensation module, and then connected to the limit module, the delay module and the PWM generation module 60 in sequence; the output end of the PWM generation module 60 is connected to the APF inverter 71 in the actual circuit as the output end of the control module; the voltage acquisition module 10 is used to collect the voltage value of the common coupling point of the actual circuit, obtain a voltage sampling signal, and transmit the voltage sampling signal to the voltage prediction module 30 and the current The prediction module 40; the voltage prediction module 30 is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and output the voltage prediction signal to the voltage generation module 50; the current acquisition module 20 is used to collect the current value of the filter inductor 72 of the actual circuit to obtain a current sampling signal, and transmit the current sampling signal to the current prediction module 40; the current prediction module 40 is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and obtain the current by using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module The current prediction signal is output to the voltage generation module 50 and the error compensation module; the voltage generation module 50 is used to obtain the voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the error compensation module is used to obtain the error compensation signal according to the compensation current instruction and the output of the current prediction module 40; the voltage signal and the error compensation signal are added to obtain the voltage control signal, and the voltage control signal is output to the PWM generation module 60 through the limiting module and the delay module; the PWM generation module 60 is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter 71.

[0052] Figure 3 Schematic diagram of a flow chart of an APF current inner loop control method without static error provided by an embodiment of the present invention, and the following reference Figure 1 , Figure 3 For an introduction to this method, see Figure 3 , the method comprising:

[0053] S110, using a voltage acquisition module to acquire a voltage value of a common coupling point of an actual circuit, obtaining a voltage sampling signal, and transmitting the voltage sampling signal to a voltage prediction module and a current prediction module.

[0054] S111 . Obtain a voltage prediction signal using a voltage prediction module according to a voltage sampling signal at a current moment, and output the voltage prediction signal to a voltage generation module.

[0055] Specifically, refer to Figure 1 When APF is applied to the power grid, it is necessary to detect harmonics and other power quality problems in the power grid, and quickly generate corresponding compensation currents according to fluctuations, so as to stabilize the grid side; therefore, after determining the current size that needs to be compensated, APF needs to output compensation currents of corresponding sizes; and the power grid fluctuations are changing, and the corresponding compensation currents also need to change, so it is necessary to ensure that the current output by the actual circuit 70 in the APF can change in time according to the current changes that need to be compensated, so firstly, it is necessary to collect the voltage value of the common coupling point PCC of the actual circuit at a preset period, and transmit the voltage value of the common coupling point PCC to the voltage prediction module 30, so as to use the voltage prediction module 30 to predict the voltage value that will change at the next moment.

[0056] S112, using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmitting the current sampling signal to the current prediction module.

[0057] S113, using the current prediction module to form a correction current based on the current sampling signal at the current moment and the current sampling signal at the previous moment predicted, and using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module to obtain a current prediction signal, and output the current prediction signal to the voltage generation module and the error compensation module.

[0058] Specifically, after collecting the voltage value on the current grid side and predicting the voltage value of the next cycle, it is necessary to use the current acquisition module 20 to collect the current value of the actual circuit to predict the current value of the next cycle. However, the deviation of the system parameters from the rated value will cause the current value output by the actual circuit to be inconsistent with the current value predicted to be output by the actual circuit, thereby failing to provide effective harmonic compensation or reactive power support. Therefore, it is necessary to form a correction current based on the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and use the correction current, current sampling signal, voltage sampling signal and the signal output by the delay module 90 at the previous moment to obtain a current prediction signal; use the correction current to further accurately predict the current.

[0059] S114, using the error compensation module to obtain an error compensation signal according to the compensation current instruction and the output of the current prediction module.

[0060] The compensation current instruction may be understood as an instruction corresponding to the compensation current required to compensate for the fluctuation on the current grid side.

[0061] Specifically, refer to Figure 1 After the error compensation module 100 receives the compensation current command input from the outside and the correction current output by the current prediction module 40, it generates an error compensation signal according to the compensation current command and the correction current, and transmits it to the voltage generation module 50 to perform error compensation on the voltage signal of the voltage generation module 50, thereby compensating the voltage of the driving inverter.

[0062] S115, using the voltage generation module to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; adding the voltage signal and the error compensation signal to obtain a voltage control signal, and outputting the voltage control signal to the PWM generation module through the limiting module and the delay module.

[0063] Specifically, the current prediction module 40 transmits the predicted current prediction signal of the filter inductor 72 in the actual circuit of the next acquisition cycle to the voltage generation module 50, and the voltage prediction module 30 transmits the predicted voltage prediction signal of the grid side of the next acquisition cycle to the voltage generation module 50. The voltage generation module 50 outputs a voltage signal according to the current prediction signal including the current value of the filter inductor 72 in the next acquisition cycle, the voltage prediction signal including the voltage value of the common coupling point PCC in the next acquisition cycle, and the compensation current instruction corresponding to the current required by the grid side. The voltage signal and the error compensation signal are added to obtain a voltage control signal, and the voltage control signal is output to the PWM generation module 60 through the limit module 80 and the delay module 90.

[0064] S116. Use the PWM generation module to convert the voltage control signal into a PWM wave signal to drive the APF inverter.

[0065] Specifically, after receiving the voltage control signal, the PWM generation module 60 converts it into a PWM wave signal, thereby driving the APF inverter 71 to generate a corresponding compensation current to compensate the grid side, so that the final output compensation current value is equal to the current value corresponding to the compensation current instruction.

[0066] Optionally, refer to Figure 3, DGs represents the DC side; L1 represents the filter inductor, R1 represents the parasitic resistance, PCC represents the common coupling point, Lline represents the line inductor, Rline represents the line parasitic resistance, and Grid represents the grid. That is, the three-phase current iLabc and the three-phase voltage upcc_abc output by the actual circuit 70 will pass through the filter inductor L1 and the parasitic resistance R1 to reach the grid side. If the filter inductor L1 and the parasitic resistance R1 do not match the rated values, the current output to the grid side by the actual circuit 70 according to the compensation current instruction will be inconsistent with the compensation current required by the grid side. Therefore, an error compensation signal including an error compensation coefficient is also output to compensate for the current deviation caused by the deviation of the filter inductor L1 and the parasitic resistance R1 from the rated values. Figure 4 This is the current change following curve diagram under the APF current inner loop without net difference control method without static error. Figure 5 This is the current change following curve diagram of the prior art, refer to Figure 4 , Figure 5 , i* d and i* q are the d-axis component and q-axis component of the compensation current command, i d and i q The d-axis component and q-axis component of the actual output follow-up current are shown in the figure. The technical solution of the embodiment of the present invention can achieve fast following of the compensation current instruction without any current control steady-state error even when there is a huge error in the system filtering parameters.

[0067] An embodiment of the present invention provides an APF current inner loop control system and control method without static error, the system comprising a control module and an actual circuit; the control module comprising a voltage acquisition module, a current acquisition module, a voltage prediction module, a current prediction module, a voltage generation module, a limit module, a delay module, an error compensation module and a PWM generation module; the actual circuit comprises an APF inverter and a filter inductor, the APF inverter and the filter inductor are connected in series and connected to the grid side; the input end of the voltage acquisition module is connected to the common coupling point of the actual circuit, the output end of the voltage acquisition module is respectively connected to the input end of the voltage prediction module and the input end of the current prediction module; the input end of the current acquisition module The output end of the current acquisition module is connected to the input end of the current prediction module; the input end of the current prediction module is also connected to the output end of the delay module; the output end of the current prediction module is respectively connected to the input end of the error compensation module and the input end of the voltage generation module; the input of the voltage generation module is also used to receive the external compensation current instruction and the output of the voltage prediction module; the error compensation module also includes a compensation current instruction input end for receiving the external compensation current instruction; the output of the voltage generation module is added to the output of the error compensation module, and then connected to the limit module, the delay module and the PWM generation module in turn; the output end of the PWM generation module is used as the control module The output end is connected to the APF inverter in the actual circuit; the voltage acquisition module is used to collect the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmit the voltage sampling signal to the voltage prediction module and the current prediction module; the voltage prediction module is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and output the voltage prediction signal to the voltage generation module; the current acquisition module is used to collect the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmit the current sampling signal to the current prediction module; the current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and A current prediction signal is obtained by using the correction current, current sampling signal, voltage sampling signal and the output signal of the delay module, and the current prediction signal is output to the voltage generation module and the error compensation module; the error compensation module is used to obtain the error compensation signal according to the compensation current instruction and the output of the current prediction module; the voltage generation module is used to obtain the voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the voltage control signal is obtained by adding the voltage signal and the error compensation signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module; the PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.The above technical solution uses the output current sampling signal of the current control cycle and the output current signal of the current control cycle predicted in the previous cycle to form a correction current in a specific ratio; then uses the correction current to generate the current prediction signal of the next cycle; and then generates a voltage signal; and at the same time uses the correction current to generate an error compensation signal, and adds it to the voltage signal to obtain a voltage control signal input to the PWM modulation module to drive the APF. This solution can not only realize APF control with dynamic tracking without delay, but also solve the steady-state error of current tracking caused by system parameter deviation, thereby improving the accuracy and reliability of control.

[0068] Optionally, after the voltage value of the common coupling point of the actual circuit is collected by the voltage collection module to obtain the voltage sampling signal, before the voltage sampling signal is transmitted to the voltage prediction module and the current prediction module, the method further includes:

[0069] The three-phase output voltage at the common coupling point is converted into the voltage on the axis of the synchronous rotating coordinate system.

[0070] For example, based on the formula The three-phase output voltage at the common coupling point is converted into the voltage on the axis of the synchronous rotating coordinate system; wherein, θ represents the rotation angle of the synchronous rotating coordinate system, udpcc and uqpcc represent the d-axis and q-axis components of the three-phase output voltage in the synchronous rotating coordinate system, respectively, and upcc_a, upcc_b and upcc_c represent the three-phase output voltage.

[0071] After using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain the current sampling signal, before transmitting the current sampling signal to the current prediction module, it also includes:

[0072] The three-phase output current of the filter inductor is converted into the current on the axis of the synchronous rotating coordinate system.

[0073] For example, based on the formula The three-phase output current of the filter inductor is converted into the current on the axis of the synchronous rotating coordinate system; wherein, iLd and iLq respectively represent the d-axis and q-axis components of the three-phase output current in the synchronous rotating coordinate system, and iLa, iLb and iLc represent the three-phase output current.

[0074] Optionally, in the above step S111, using the voltage prediction module to obtain a voltage prediction signal according to the voltage sampling signal at the current moment includes:

[0075] Using the voltage prediction module, according to the voltage sampling signal at the current moment, based on the formula The d-axis component udpcc_p(k+1) and q-axis component uqpcc_p(k+1) of the voltage prediction signal including the predicted voltage value at the next acquisition moment are obtained; wherein udpcc(k) and uqpcc(k) respectively represent the q-axis component and d-axis component of the voltage value of the common coupling point of the synchronous rotating coordinate system at the current acquisition moment; udpcc(k-1) and uqpcc(k-1) respectively represent the q-axis component and d-axis component of the voltage value of the common coupling point of the synchronous rotating coordinate system at the previous acquisition moment.

[0076] Specifically, after the voltage prediction module 30 uses the voltage acquisition module 10 to acquire the q-axis component udpcc(k) and the d-axis component uqpcc(k) of the common coupling point voltage value in the current acquisition cycle, the q-axis component udpcc(k-1) and the d-axis component uqpcc(k-1) of the common coupling point voltage value acquired in the previous acquisition cycle are used to predict the voltage based on the formula The d-axis component udpcc_p(k+1) and the q-axis component uqpcc_p(k+1) of the voltage prediction signal including the predicted voltage value of the common coupling point at the next acquisition time are predicted.

[0077] Optionally, in the above step S113, a current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and a current prediction signal is obtained by using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module, including:

[0078] Using the current prediction module, based on the formula

[0079] The d-axis component idp(k+1) and q-axis component iqp(k+1) of the current prediction signal in the synchronous rotating coordinate system at the next acquisition time are obtained; wherein, is the correction current expression, and X1 represents the proportion of actual current and predicted current in the correction current.

[0080] Specifically, the correction current expression is: The current prediction module 40 uses the actual current currently output and the predicted current that should be output in the current cycle to obtain the correction current, and then uses the correction current to correct the next predicted current, that is, based on the formula

[0081] According to the correction current, the current sampling signal, the voltage sampling signal and the signal output by the delay module, the d-axis component idp(k+1) and the q-axis component iqp(k+1) of the current prediction signal including the predicted current value at the next acquisition moment are obtained, wherein adjusting X1 can adjust the proportional relationship between the actual current and the predicted current, thereby performing steady-state error compensation.

[0082] Optionally, in the above step S115, using a voltage generation module to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction includes:

[0083] Using the voltage generation module, according to the current prediction signal, voltage prediction signal and compensation current instruction, based on the formula The voltage signal is obtained; wherein ud(k+1) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1, and uq(k+1) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1; udpcc_p(k+1) is the d-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, and uqpcc_p(k+1) is the q-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1; idref(k) is the d-axis component of the compensation current command in the synchronous rotating coordinate system at time k, and iq ref(k) is the q-axis component of the compensation current command in the synchronous rotating coordinate system at time k, idref(k-1) is the d-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period, iqref(k-1) is the q-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period; idp(k+1) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1, iqp(k+1) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1; Bp is the parameter estimation value of B, Bp -1 It is the reciprocal of Bp; X2 represents the ratio of the current prediction signal to the compensation current command.

[0084] Specifically, the core control equation of the voltage generation module 50 is: It can be seen that the voltage signal output by the voltage generating module 50 is affected by the current prediction signal, the voltage prediction signal and the compensation current instruction. Therefore, after the voltage generating module 50 receives the current prediction signal, the voltage prediction signal and the compensation current instruction, it obtains the voltage signal of the next cycle based on the above signals and the core control equation, and then adds it to the error compensation signal to obtain the voltage control signal, and outputs the voltage control signal to the PWM generating module through the limiting module and the delay module to generate a PWM control signal to drive the actual circuit.

[0085] Optionally, the core control equation of the error compensation module 100 is:

[0086] Among them, ud_cor(k+1) is the d-axis component of the error compensation signal, uq_cor(k+1) is the p-axis component of the error compensation signal, Bp is the parameter estimation value of B, Bp-1 represents the reciprocal of Bp, X3 is the compensation coefficient, and X3=X1+X2.

[0087] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An APF current inner loop control system without static error, characterized in that: It includes a control module and an actual circuit; the control module includes a voltage acquisition module, a current acquisition module, a voltage prediction module, a current prediction module, a voltage generation module, a limit module, a delay module, an error compensation module and a PWM generation module; the actual circuit includes an APF inverter and a filter inductor, and the APF inverter and the filter inductor are connected in series and then connected to the grid side; The input end of the voltage acquisition module is connected to the common coupling point of the actual circuit, and the output end of the voltage acquisition module is respectively connected to the input end of the voltage prediction module and the input end of the current prediction module; the input end of the current acquisition module is connected to the filter inductor of the actual circuit, and the output end of the current acquisition module is connected to the input end of the current prediction module; the input end of the current prediction module is also connected to the output end of the delay module; the output end of the current prediction module is respectively connected to the input end of the error compensation module and the input end of the voltage generation module; the input of the voltage generation module is also used to receive the compensation current instruction of the external compensation current instruction and the output of the voltage prediction module; the error compensation module also includes a compensation current instruction input end for receiving the external compensation current instruction; the output of the voltage generation module is added to the output of the error compensation module, and is sequentially connected to the limit module, the delay module and the PWM generation module; the output end of the PWM generation module is connected to the APF inverter in the actual circuit as the output end of the control module; The voltage acquisition module is used to acquire the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmit the voltage sampling signal to the voltage prediction module and the current prediction module; The voltage prediction module is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and output the voltage prediction signal to the voltage generation module; The current acquisition module is used to collect the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmit the current sampling signal to the current prediction module; The current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and obtain a current prediction signal by using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module, and output the current prediction signal to the voltage generation module and the error compensation module; The voltage generating module is used to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; The error compensation module is used to obtain an error compensation signal according to the compensation current instruction and the output of the current prediction module; The voltage control signal is obtained by adding the voltage signal and the error compensation signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module; The PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.

2. The control system according to claim 1, characterized in that: The discrete control model of the actual circuit is: Among them, Ts is the preset sampling period, ω0 is the rated angular frequency, L1 is the filter inductance, R1 is the parasitic resistance in the actual circuit, A and B are constants, ud(k) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k, and uq(k) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k; udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, and uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k; iLd(k) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k, and iLq(k) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k; iLd(k+1) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k+1, and iLq(k+1) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k+1.

3. The control system according to claim 1, characterized in that: The core control equation of the voltage prediction module is: Among them, udpcc_p(k+1) is the d-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, uqpcc_p(k+1) is the q-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, udpcc(k-1) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system with a k-1 period, and uqpcc(k-1) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system with a k-1 period.

4. The control system according to claim 1, characterized in that: The core control equation of the current prediction module is: Among them, idp(k+1) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1, iqp(k+1) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system at time k+1, idp(k) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system at time k, iqp(k) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system at time k; ud(k) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k, uq(k) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k; udpcc(k) is the d-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k, uqpcc(k) is the q-axis component of the voltage sampling signal in the synchronous rotating coordinate system at time k; iLd(k) is the d-axis component of the current sampling signal in the synchronous rotating coordinate system at time k, and iLq(k) is the q-axis component of the current sampling signal in the synchronous rotating coordinate system at time k.

5. The control system according to claim 1, characterized in that: The core control equation of the error compensation module is: Among them, ud_cor(k+1) is the d-axis component of the error compensation signal, uq_cor(k+1) is the p-axis component of the error compensation signal, Bp is the parameter estimation value of B, Bp-1 represents the reciprocal of Bp, and X3 is the compensation coefficient.

6. A static error-free APF current inner loop control method, applied to the static error-free APF current inner loop control system according to any one of claims 1 to 5, characterized in that: include: Using the voltage acquisition module to acquire the voltage value of the common coupling point of the actual circuit to obtain a voltage sampling signal, and transmitting the voltage sampling signal to the voltage prediction module and the current prediction module; Using the voltage prediction module to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, and outputting the voltage prediction signal to the voltage generation module; Using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, and transmitting the current sampling signal to the current prediction module; Using the current prediction module to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and using the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module to obtain a current prediction signal, and output the current prediction signal to the voltage generation module and the error compensation module; Using the error compensation module to obtain an error compensation signal according to the compensation current instruction and the output of the current prediction module; The voltage generation module is used to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction; the voltage signal and the error compensation signal are added to obtain a voltage control signal, and the voltage control signal is output to the PWM generation module through the limiting module and the delay module; The PWM generation module is used to convert the voltage control signal into a PWM wave signal to drive the APF inverter.

7. The control method according to claim 6, characterized in that: After the voltage value of the common coupling point of the actual circuit is collected by the voltage collection module to obtain a voltage sampling signal, before the voltage sampling signal is transmitted to the voltage prediction module and the current prediction module, the method further includes: Based on the formula Convert the three-phase output voltage of the common coupling point into a voltage on a synchronous rotating coordinate system; wherein θ represents the rotation angle of the synchronous rotating coordinate system, udpcc and uqpcc represent the d-axis and q-axis components of the common coupling point voltage in the synchronous rotating coordinate system, respectively, and upcc_a, upcc_b and upcc_c represent the three-phase output voltage; After using the current acquisition module to acquire the current value of the filter inductor of the actual circuit to obtain a current sampling signal, before transmitting the current sampling signal to the current prediction module, it also includes: Based on the formula The three-phase output current of the filter inductor is converted into a current on a synchronous rotating coordinate system; wherein iLd and iLq respectively represent the d-axis and q-axis components of the three-phase output current in the synchronous rotating coordinate system, and iLa, iLb and iLc represent the three-phase output current.

8. The control method according to claim 7, characterized in that: The voltage prediction module is used to obtain a voltage prediction signal according to the voltage sampling signal at the current moment, including: The voltage prediction module is used according to the voltage sampling signal at the current moment, based on the formula A voltage prediction signal is obtained.

9. The control method according to claim 6, characterized in that: The current prediction module is used to form a correction current according to the current sampling signal at the current moment and the current sampling signal at the current moment predicted at the previous moment, and the correction current, the current sampling signal, the voltage sampling signal and the output signal of the delay module are used to obtain a current prediction signal, including: Using the current prediction module, based on the formula The d-axis component idp(k+1) and the q-axis component iqp(k+1) of the current prediction signal in the synchronous rotating coordinate system at the next acquisition moment are obtained; wherein, is the correction current expression, and X1 represents the proportion of the actual current and the predicted current in the correction current.

10. The control method according to claim 6, characterized in that: The voltage generation module is used to obtain a voltage signal according to the current prediction signal, the voltage prediction signal and the compensation current instruction, including: By using the voltage generation module, according to the current prediction signal, the voltage prediction signal and the compensation current instruction, based on the formula A voltage signal is obtained; wherein ud(k+1) is the d-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1, and uq(k+1) is the q-axis component of the voltage signal in the synchronous rotating coordinate system at time k+1; udpcc_p(k+1) is the d-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1, and uqpcc_p(k+1) is the q-axis component of the voltage prediction signal in the synchronous rotating coordinate system at time k+1; idref(k) is the d-axis component of the compensation current command in the synchronous rotating coordinate system at time k, and iq ref(k) is the q-axis component of the compensation current command in the synchronous rotating coordinate system at time k, idref(k-1) is the d-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period, iqref(k-1) is the q-axis component of the compensation current command in the synchronous rotating coordinate system of k-1 period; idp(k+1) is the d-axis component of the current prediction signal in the synchronous rotating coordinate system of k+1 time, iqp(k+1) is the q-axis component of the current prediction signal in the synchronous rotating coordinate system of k+1 time; Bp is the parameter estimation value of B, Bp -1 It is the reciprocal of Bp; X2 represents the ratio of the current prediction signal to the compensation current command.

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