Inverter distributed power supply control method based on PID

Abstract

The invention belongs to the technical field of power supply, and provides a PID (Proportion Integration Differentiation)-based inverter type distributed power supply control method, which comprises the following steps of: acquiring three-phase voltage and three-phase current output by an inverter in an inverter type distributed power supply; coordinate transformation is carried out on the three-phase voltage and the three-phase current respectively, and decoupling voltage and decoupling current are obtained; inputting the decoupling voltage into an outer loop PID regulator to obtain a reference current; inputting the reference current and the decoupling current into an inner loop PID regulator to obtain a decoupling modulation signal; generating a switch control signal according to the decoupling modulation signal, and performing validity detection on the switch control signal to obtain a validity detection result; and if the validity detection result is that the switch control signal is valid, controlling the output voltage and the output current of the inverter in the inversion type distributed power supply through the switch control signal. Due to the adoption of a double-loop control strategy of a voltage outer loop and a current inner loop, the anti-interference capability, the control reliability and the stability of the inverter type distributed power supply are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a PID-based inverter-type distributed power supply control method. Background Art

[0002] Distributed power sources can be classified in different ways. According to the type of electrical interface they are connected to the grid, they can be divided into two categories: the first category is distributed power sources that are directly connected to the grid through a step-up transformer, mainly synchronous machines and double-fed wind turbines that can generate industrial frequency AC power; the second category is distributed power sources that supply power to the system through power electronic converters, mainly photovoltaic power sources, direct-drive wind turbines, and fuel cells. The most common type of distributed power source is the inverter-based distributed generation (IBDG) that uses an inverter as a grid-connected interface to connect to the grid.

[0003] Since inverter-type distributed power sources need to be connected to the power grid through grid-connected inverters, their fault output characteristics are affected by the inverter control strategy. In related technologies, inverter-type distributed power sources usually adopt a single-loop control strategy. Under the single-loop control strategy, when the load changes, the control response speed is slow. At the same time, it may cause unstable power transmission between the inverter and the power grid, affecting the safety and stability of the entire power system.

[0004] It can be seen that the traditional inverter-type distributed power supply control strategy has problems with insufficient control reliability and stability. Summary of the invention

[0005] The present invention provides a PID-based inverter distributed power supply control method to solve the defects of insufficient control reliability and stability in traditional inverter distributed power supply control strategies.

[0006] The present invention provides a PID-based inverter-type distributed power supply control method, comprising: Obtain the three-phase voltage and three-phase current output by the inverter in the inverter-type distributed power supply; Performing coordinate transformation on the three-phase voltage and the three-phase current respectively to obtain a decoupling voltage and a decoupling current; Inputting the decoupling voltage into an outer loop PID regulator to obtain a reference current output by the outer loop PID regulator; Inputting the reference current and the decoupling current into an inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator; generating a switch control signal according to the decoupling modulation signal, and performing validity detection on the switch control signal to obtain a validity detection result; If the validity detection result is that the switch control signal is valid, the output voltage and output current of the inverter in the inverter-type distributed power supply are controlled by the switch control signal.

[0007] According to the PID-based inverter-type distributed power supply control method provided by the present invention, coordinate transformation is performed on the three-phase voltage and the three-phase current respectively to obtain a decoupled voltage and a decoupled current, including: Respectively converting the three-phase voltage and the three-phase current from a three-phase stationary coordinate system to a two-phase stationary coordinate system to obtain a two-phase voltage and a two-phase current; The two-phase voltage and the two-phase current are respectively converted from a two-phase stationary coordinate system to a synchronous rotating coordinate system to obtain a decoupled voltage and a decoupled current.

[0008] According to the PID-based inverter-type distributed power supply control method provided by the present invention, the decoupling voltage includes: a d-axis voltage coordinate value and a q-axis voltage coordinate value; Inputting the decoupling voltage into an outer loop PID regulator to obtain a reference current output by the outer loop PID regulator, including: The d-axis voltage coordinate value is input into an outer loop PID regulator, and the outer loop PID regulator calculates the difference between a preset d-axis voltage reference value and the d-axis voltage coordinate value to obtain a d-axis voltage error value; Performing PID operation on the d-axis voltage error value to obtain a d-axis current reference value; The q-axis voltage coordinate value is input into an outer loop PID regulator, and the outer loop PID regulator calculates the difference between a preset q-axis voltage reference value and the q-axis voltage coordinate value to obtain a q-axis voltage error value; Performing PID operation on the q-axis voltage error value to obtain a q-axis current reference value; The d-axis current reference value and the q-axis current reference value are used as reference currents output by the outer-loop PID regulator.

[0009] According to the PID-based inverter-type distributed power supply control method provided by the present invention, the decoupling current includes: a d-axis current coordinate value and a q-axis current coordinate value; Inputting the reference current and the decoupling current into an inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator, including: Inputting the d-axis current reference value and the d-axis current coordinate value into an inner loop PID regulator, calculating the difference between the d-axis current reference value and the d-axis current coordinate value through the inner loop PID regulator, and obtaining a d-axis current error value; Performing PID operation on the d-axis current error value to obtain a d-axis modulation signal; The q-axis current reference value and the q-axis current coordinate value are input into an inner loop PID regulator, and the inner loop PID regulator calculates the difference between the q-axis current reference value and the q-axis current coordinate value to obtain a q-axis current error value; Performing PID operation on the q-axis current error value to obtain a q-axis modulation signal; The d-axis modulation signal and the q-axis modulation signal are used as decoupling modulation signals output by the inner-loop PID regulator.

[0010] According to the PID-based inverter-type distributed power supply control method provided by the present invention, a switch control signal is generated according to the decoupling modulation signal, including: Converting the d-axis modulation signal and the q-axis modulation signal in the decoupled modulation signal from a synchronous rotating coordinate system to a two-phase stationary coordinate system to obtain a two-phase modulation signal; Converting the two-phase modulation signal from a two-phase stationary coordinate system to a three-phase stationary coordinate system to obtain a three-phase modulation signal; The three-phase voltage wave values ​​in the three-phase modulation signal are compared with preset carrier reference values ​​respectively, and a switch control signal is generated according to the comparison result.

[0011] According to the PID-based inverter-type distributed power supply control method provided by the present invention, the switch control signal is tested for effectiveness to obtain a effectiveness test result, including: Respectively determining an amplitude deviation, a frequency deviation, a duty cycle deviation, and a phase deviation of the switch control signal; Normalizing the amplitude deviation, the frequency deviation, the duty cycle deviation, and the phase deviation, and performing weighted operation on the normalized amplitude deviation, the frequency deviation, the duty cycle deviation, and the phase deviation to obtain a signal comprehensive deviation; The validity detection result of the switch control signal is obtained according to the signal comprehensive deviation.

[0012] According to the PID-based inverter-type distributed power supply control method provided by the present invention, the validity detection result of the switch control signal is obtained according to the signal comprehensive deviation, including: If the signal comprehensive deviation is greater than or equal to the preset deviation upper limit value, the validity detection result is that the switch control signal is invalid; If the signal comprehensive deviation is less than the preset deviation upper limit, the validity detection result is that the switch control signal is valid.

[0013] According to the PID-based inverter-type distributed power supply control method provided by the present invention, after controlling the output voltage and output current of the inverter in the inverter-type distributed power supply by the switch control signal, the method further includes: Determine the output voltage deviation rate, voltage fluctuation rate, output current total harmonic distortion rate and power factor of the inverter-type distributed power supply; According to the output voltage deviation rate, the voltage fluctuation rate, the output current total harmonic distortion rate and the power factor, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

[0014] According to the PID-based inverter-type distributed power supply control method provided by the present invention, the key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted according to the output voltage deviation rate, the voltage fluctuation rate, the output current total harmonic distortion rate and the power factor, including: Subtracting the output voltage deviation rate from a preset deviation rate reference value, and taking a first difference obtained by the subtraction as a quotient of the output voltage deviation rate to obtain a voltage deviation error ratio; Subtracting the voltage fluctuation rate from a preset fluctuation rate reference value, and dividing the voltage fluctuation rate by a second difference, to obtain a voltage fluctuation error ratio; Subtracting the output current total harmonic distortion rate from a preset distortion rate reference value, and dividing the third difference obtained by the difference by the output current total harmonic distortion rate to obtain a current harmonic error ratio; Subtracting a preset power factor reference value from the power factor, and dividing a fourth difference obtained by the subtraction by the power factor to obtain a power factor error ratio; Extracting the first two with larger values ​​among the voltage deviation error ratio, the voltage fluctuation error ratio, the current harmonic error ratio and the power factor error ratio to obtain a target error ratio; According to the target error ratio, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

[0015] The PID-based inverter distributed power supply control method provided by the present invention obtains the three-phase voltage and three-phase current output by the inverter in the inverter distributed power supply, performs coordinate transformation on the three-phase voltage and the three-phase current respectively, obtains the decoupling voltage and the decoupling current, inputs the decoupling voltage into the outer loop PID regulator, obtains the reference current output by the outer loop PID regulator, inputs both the reference current and the decoupling current into the inner loop PID regulator, obtains the decoupling modulation signal output by the inner loop PID regulator, generates a switch control signal according to the decoupling modulation signal, performs validity detection on the switch control signal, obtains the validity detection result, and if the validity detection result is that the switch control signal is valid, the output voltage and output current of the inverter in the inverter distributed power supply are controlled by the switch control signal. Since the control link adopts a dual-loop control strategy of voltage outer loop control and current inner loop control, when the entire system is subject to external interference, such as load mutation or grid voltage fluctuation, the voltage outer loop can adjust the output voltage in time, while the current inner loop can quickly respond to current changes, suppress current fluctuations, prevent overcurrent, and avoid damage to the inverter due to current mutations, thereby improving the anti-interference ability of the inverter-type distributed power supply and improving the control reliability and stability of the inverter-type distributed power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a flow chart of a PID-based inverter-type distributed power supply control method provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of an inverter circuit in an embodiment of the present invention; Figure 3 It is a structural diagram of a PID-based inverter-type distributed power supply control system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Combine the following Figures 1 to 3The detailed scheme of the PID-based inverter-type distributed power supply control method provided by an embodiment of the present invention is described.

[0020] Figure 1 It is a flow chart of a PID-based inverter-type distributed power supply control method provided in an embodiment of the present invention.

[0021] like Figure 1 As shown, the PID-based inverter-type distributed power supply control method provided in an embodiment of the present invention can be executed by an electronic device with data receiving and data processing capabilities, and the method mainly includes the following steps: Step 110: Obtain the three-phase voltage and three-phase current output by the inverter in the inverter-type distributed power source.

[0022] In this embodiment, the three-phase voltage in the three-phase AC voltage signal output by the inverter can be collected by a voltage sensor. 、u b 、u c The three-phase current in the three-phase AC current signal output by the inverter is collected by the current sensor 、 i b 、i c .

[0023] In practical applications, the inverter-type distributed power supply is structurally divided into an inverter and a power supply unit. In this embodiment, the inverter of the inverter-type distributed power supply adopts a two-level three-phase bridge inverter circuit. The structure of the inverter circuit is as follows: Figure 2 As shown, the inverter circuit is mainly composed of six power switch tubes Q1, Q2, Q3, Q4, Q5, and Q6. Every two power switch tubes are connected in series to form a bridge arm, and there are three bridge arms in total.

[0024] Step 120: performing coordinate transformation on the three-phase voltage and the three-phase current respectively to obtain a decoupled voltage and a decoupled current.

[0025] It can be understood that in order to simplify the analysis process, this embodiment transforms the three-phase voltage and the three-phase current from the three-phase stationary coordinate system to the synchronous rotating coordinate system by means of coordinate transformation to obtain the decoupled voltage u d and u q And decoupling current i d and i q .

[0026] In some embodiments, the decoupling voltage and the decoupling current may be digitally filtered, such as using a low-pass filter to remove high-frequency noise and interference to improve signal quality and stability.

[0027] Step 130: input the decoupling voltage into the outer loop PID regulator to obtain a reference current output by the outer loop PID regulator.

[0028] In this embodiment, the outer loop PID regulator mainly implements PID regulation of the decoupling voltage and can eventually output a reference current.

[0029] Step 140: Input the reference current and the decoupling current into the inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator.

[0030] In this embodiment, the inner loop PID regulator mainly implements PID regulation of the decoupling current, and can eventually output a decoupling modulation signal.

[0031] Step 150: Generate a switch control signal according to the decoupling modulation signal, and perform validity detection on the switch control signal to obtain a validity detection result.

[0032] It can be understood that the effectiveness detection link can determine the effectiveness of the switch control signal, and the subsequent control is implemented under the premise that the switch control signal is valid, which can ensure the accuracy and effectiveness of the control strategy.

[0033] Step 160: If the validity detection result is that the switch control signal is valid, the output voltage and output current of the inverter in the inverter-type distributed power source are controlled by the switch control signal.

[0034] This embodiment adopts a dual-loop control strategy of voltage outer-loop control and current inner-loop control. The voltage outer-loop control can monitor and stabilize the output voltage in real time. When the system is subject to external interference, such as load mutation and grid voltage fluctuation, the voltage outer loop can adjust the output voltage in time to keep it near the voltage reference value. The current inner loop can quickly respond to current changes, suppress current fluctuations, prevent overcurrent, and avoid damage to the inverter due to current mutations, thereby improving the anti-interference ability and stability of the inverter-type distributed power supply control link.

[0035] In one embodiment, coordinate transformation is performed on the three-phase voltage and the three-phase current respectively to obtain the decoupled voltage and the decoupled current, which specifically includes: Firstly, the three-phase voltage and the three-phase current are respectively converted from the three-phase stationary coordinate system to the two-phase stationary coordinate system to obtain the two-phase voltage and the two-phase current.

[0036] In this embodiment, the three-phase voltage and three-phase current collected in the three-phase stationary coordinate system (i.e., the abc coordinate system) can be converted to the two-phase stationary coordinate system (i.e., the αβ coordinate system) through Clarke transformation. Taking the three-phase voltage as an example, the conversion formula is as follows: (1) in, u α and u β Represents the two-phase voltage, 、u b 、u c Indicates three-phase voltage.

[0037] Similarly, the two-phase current can be obtained i α and i β .

[0038] Then, the two-phase voltage and the two-phase current are respectively transformed from the two-phase stationary coordinate system to the synchronous rotating coordinate system to obtain the decoupled voltage and the decoupled current.

[0039] In this embodiment, the two-phase voltage and two-phase current in the two-phase stationary coordinate system can be converted to the synchronous rotating coordinate system (ie, the dq coordinate system) through Park transformation. Taking the two-phase voltage as an example, the conversion formula is as follows: (2) in, u d and u q represents the decoupling voltage, u α and u β Represents the two-phase voltage, It represents the phase angle of the grid voltage and can be obtained through a phase-locked loop.

[0040] Similarly, the decoupling current can be obtained i d and i q .

[0041] When a three-phase symmetrical fault occurs in the distribution network, the grid voltage remains symmetrical, and the grid connection point voltage only contains a DC component without a negative sequence component. The above decoupling scheme can achieve accurate decoupling of the three-phase voltage and the three-phase current.

[0042] However, when an asymmetric fault occurs in the distribution network, the grid voltage will no longer remain symmetrical. At this time, the grid voltage will contain not only the positive-sequence component but also the negative-sequence component. The three-phase current output by the inverter in the inverter-type distributed power supply will also contain positive-sequence components and negative-sequence components. The negative-sequence components of the three-phase voltage and three-phase current will produce 2-fold frequency components in the dq coordinate system after Park transformation. The existence of negative-sequence components will also affect the service life of the inverter and the power quality of the grid.

[0043] Due to the existence of negative-sequence components, the positive and negative sequence components need to be decoupled. At this time, two synchronously rotating dq coordinate systems can be established, namely the positive-sequence synchronously rotating dq coordinate system and the negative-sequence synchronously rotating dq coordinate system. The positive and negative sequence components of the three-phase voltage and three-phase current are converted into DC components in their respective coordinate systems after Park transformation.

[0044] When an asymmetric fault occurs in the distribution network, the mathematical model of the positive and negative sequence components of the three-phase voltage in the dq coordinate system is: (3) in, , It represents the positive sequence component of the three-phase voltage in the dq coordinate system, , It represents the negative sequence component of the three-phase voltage in the dq coordinate system, , represents the positive sequence component of the three-phase current in the dq coordinate system, , It represents the negative sequence component of the three-phase current in the dq coordinate system, , It represents the positive sequence component of the grid connection point voltage on the dq axis, , It represents the negative sequence component of the grid connection point voltage on the dq axis, represents the grid frequency, R and L represent the filter resistance and filter inductance respectively.

[0045] In one embodiment, the decoupling voltage includes: a d-axis voltage coordinate value and a q-axis voltage coordinate value.

[0046] The decoupling voltage is input into the outer loop PID regulator to obtain the reference current output by the outer loop PID regulator, which specifically includes: In the first step, the d-axis voltage coordinate value is input into the outer loop PID regulator, and the outer loop PID regulator calculates the difference between the preset d-axis voltage reference value and the d-axis voltage coordinate value to obtain the d-axis voltage error value.

[0047] In this embodiment, the calculation formula of the d-axis voltage error value is: (4) in, u d represents the d-axis voltage error value, u dref Indicates the preset d-axis voltage reference value, u d Indicates the d-axis voltage coordinate value.

[0048] In the second step, PID operation is performed on the d-axis voltage error value to obtain the d-axis current reference value.

[0049] In this embodiment, a PID operation is performed on the d-axis voltage error value, and the specific calculation is as follows: (5) in, i dref represents the d-axis current reference value, K P1 Represents the proportional coefficient of the outer loop PID regulator, K i1 Represents the integral coefficient of the outer loop PID regulator, K d1 Represents the differential coefficient of the outer loop PID regulator, u d Indicates the d-axis voltage error value.

[0050] The third step is to input the q-axis voltage coordinate value into the outer loop PID regulator, and calculate the difference between the preset q-axis voltage reference value and the q-axis voltage coordinate value through the outer loop PID regulator to obtain the q-axis voltage error value.

[0051] In this embodiment, the calculation formula of the q-axis voltage error value is: (6) in, u q represents the q-axis voltage error value, u qref Indicates the preset q-axis voltage reference value, u q Indicates the q-axis voltage coordinate value.

[0052] The fourth step is to perform PID operation on the q-axis voltage error value to obtain the q-axis current reference value.

[0053] In this embodiment, PID operation is performed on the q-axis voltage error value, and the specific calculation is as follows: (7) in, i qref represents the q-axis current reference value,K P1 Represents the proportional coefficient of the outer loop PID regulator, K i1 Represents the integral coefficient of the outer loop PID regulator, K d1 Represents the differential coefficient of the outer loop PID regulator, u q Indicates the q-axis voltage error value.

[0054] The fifth step is to use the d-axis current reference value and the q-axis current reference value as the reference current output by the outer loop PID regulator.

[0055] In one embodiment, the decoupling current specifically includes: a d-axis current coordinate value and a q-axis current coordinate value.

[0056] The reference current and the decoupling current are input into the inner loop PID regulator to obtain the decoupling modulation signal output by the inner loop PID regulator, which specifically includes: In the first step, the d-axis current reference value and the d-axis current coordinate value are input into the inner loop PID regulator, and the difference between the d-axis current reference value and the d-axis current coordinate value is calculated by the inner loop PID regulator to obtain the d-axis current error value.

[0057] In this embodiment, the d-axis current error value can be calculated as follows: (8) in, i d represents the d-axis current error value, i dref represents the d-axis current reference value, i d Indicates the d-axis current coordinate value.

[0058] In the second step, PID operation is performed on the d-axis current error value to obtain the d-axis modulation signal.

[0059] In this embodiment, a PID operation is performed on the d-axis current error value, and the specific calculation is as follows: (9) in, u dmod represents the d-axis modulation signal, K P2 Represents the proportional coefficient of the inner loop PID regulator, K i2 Represents the integral coefficient of the inner loop PID regulator, K d2 Represents the differential coefficient of the inner loop PID regulator, i d Indicates the d-axis current error value.

[0060] In the third step, the q-axis current reference value and the q-axis current coordinate value are input into the inner loop PID regulator, and the difference between the q-axis current reference value and the q-axis current coordinate value is calculated by the inner loop PID regulator to obtain the q-axis current error value.

[0061] In this embodiment, the q-axis current error value can be calculated as follows: (10) in, i q represents the q-axis current error value, i qref represents the q-axis current reference value, i q Indicates the q-axis current coordinate value.

[0062] The fourth step is to perform PID operation on the q-axis current error value to obtain the q-axis modulation signal.

[0063] In this embodiment, a PID operation is performed on the q-axis current error value, and the specific calculation is as follows: (11) in, u qmod represents the q-axis modulation signal, K P2 Represents the proportional coefficient of the inner loop PID regulator, K i2 Represents the integral coefficient of the inner loop PID regulator, K d2 Represents the differential coefficient of the inner loop PID regulator, i q Indicates the q-axis current error value.

[0064] The fifth step is to use the d-axis modulation signal and the q-axis modulation signal as the decoupling modulation signal output by the inner loop PID regulator.

[0065] In one embodiment, generating a switch control signal according to the decoupling modulation signal specifically includes: Firstly, the d-axis modulation signal and the q-axis modulation signal in the decoupling modulation signal are converted from a synchronous rotating coordinate system to a two-phase stationary coordinate system to obtain a two-phase modulation signal.

[0066] In this embodiment, the decoupled modulation signal in the dq coordinate system can be u dmod and u qmodThrough the inverse Park transform, the α-axis modulation signal and the β-axis modulation signal in the two-phase modulation signal are obtained. The conversion formula is as follows: (12) in, u αmod represents the α-axis modulation signal, u βmod represents the β-axis modulation signal, u dmod represents the d-axis modulation signal, u qmod represents the q-axis modulation signal, It represents the phase angle of the grid voltage and can be obtained through a phase-locked loop.

[0067] Then, the two-phase modulation signal is converted from the two-phase stationary coordinate system to the three-phase stationary coordinate system to obtain a three-phase modulation signal.

[0068] In this embodiment, the two-phase modulation signal can be converted from a two-phase stationary coordinate system to a three-phase stationary coordinate system by inverse Clarke transformation to obtain a three-phase modulation signal. The conversion formula is as follows: (13) in, , , Represents a three-phase modulated signal, u αmod represents the α-axis modulation signal, u βmod represents the β-axis modulation signal.

[0069] Finally, the three-phase voltage wave values ​​in the three-phase modulation signal are compared with the preset carrier reference values ​​respectively, and a switch control signal is generated according to the comparison result.

[0070] In practical applications, each phase modulation signal in the three-phase modulation signal can be compared with the carrier reference value in the triangular wave carrier. When a phase modulation signal is greater than the carrier reference value, the corresponding switch control signal is a high level; when a phase modulation signal is less than the carrier reference value, the corresponding switch control signal is a low level.

[0071] Modulate the signal with phase A For example, compare the A phase modulation signal and carrier reference value u c : like > u c , then the switch control signal corresponding to the upper bridge arm switch tube of phase A is high level (i.e. turned on), and the switch control signal corresponding to the lower bridge arm switch tube is low level (i.e. turned off).

[0072] like < u c , the switch control signal corresponding to the upper bridge arm switch tube of phase A is low level (i.e. turned off), and the switch control signal corresponding to the lower bridge arm switch tube is high level (i.e. turned on).

[0073] Similarly, the B phase modulation signal can be and C phase modulation signal The same comparison operation is performed to obtain the corresponding switch control signal.

[0074] In one embodiment, the switch control signal is tested for validity to obtain a validity test result, which specifically includes: First, the amplitude deviation, frequency deviation, duty cycle deviation and phase deviation of the switch control signal are determined respectively.

[0075] In this embodiment, the amplitude deviation is mainly calculated based on the amplitude of the switch control signal. Specifically, the amplitude of the switch control signal can be directly measured using an oscilloscope or other instrument. The oscilloscope can display the waveform of the switch control signal in real time and can accurately measure its amplitude. Subsequently, the amplitude of the switch control signal is subtracted from the preset amplitude reference value to obtain the amplitude deviation.

[0076] In practical applications, the amplitude corresponding to the high-level signal in the switch control signal should usually be around 3.3V or 5V, depending on the logic level standard of the system. Therefore, the preset amplitude reference value may include an upper amplitude limit and a lower amplitude limit. The upper amplitude limit is set to 5V, and the lower amplitude limit is set to 3.3V. If the amplitude of the high-level signal deviates from the reference range defined by the upper amplitude limit and the lower amplitude limit, for example, the amplitude of the high-level signal is lower than 2V or higher than 6V, it means that the amplitude of the high-level signal is inaccurate, which may cause the switching device to fail to turn on or off normally.

[0077] In this embodiment, the frequency deviation is mainly calculated based on the frequency of the switch control signal. Specifically, the frequency of the switch control signal can be determined by using the frequency measurement function of a spectrum analyzer or an oscilloscope. The spectrum analyzer can accurately analyze the spectrum components of the switch control signal and determine its fundamental frequency; the oscilloscope can measure the period of the signal and then calculate the frequency.

[0078] In practical applications, the frequency of the switch control signal should be consistent with the preset PWM frequency of the system. Therefore, the frequency deviation can be obtained by subtracting the frequency of the switch control signal from the PWM frequency. For example, in a system with a preset PWM frequency of 10kHz, if the measured frequency deviation of the switch control signal exceeds ±5% (i.e., not within the range of 9.5kHz-10.5kHz), the frequency of the switch control signal is considered to be inaccurate, which may affect the output performance and power quality of the inverter.

[0079] In this embodiment, the duty cycle deviation is mainly calculated based on the duty cycle of the switch control signal. The duty cycle of the switch control signal can also be measured using an oscilloscope. The oscilloscope can intuitively display the high level duration and period of the switch control signal. The duty cycle can be obtained by calculating the ratio of the high level duration to the period.

[0080] In practical applications, the duty cycle of the switch control signal can be subtracted from the preset duty cycle reference value to obtain the duty cycle deviation. The preset duty cycle reference value can be accurately set according to the control requirements of the system. If the measured duty cycle of the switch control signal is significantly different from the preset duty cycle reference value, such as the duty cycle deviation exceeds ±3%, it means that the duty cycle of the switch control signal is inaccurate, which may cause the waveform of the output voltage to be distorted.

[0081] In this embodiment, the phase deviation is mainly calculated based on the phase of the switch control signal. Specifically, for a three-phase system, it is necessary to detect the relationship between the three-phase phases in the switch control signal. Specifically, a dual-trace or multi-trace oscilloscope can be used to simultaneously measure the three-phase signal, and the phase difference, that is, the phase deviation, can be determined by observing the relative position of the waveform.

[0082] In a three-phase system, the phase difference between the switch control signals should be strictly maintained at 120°. If the phase deviation exceeds ±5°, it will affect the symmetry of the three-phase voltage and current output by the inverter, resulting in unstable operation of loads such as motors.

[0083] Then, the amplitude deviation, frequency deviation, duty cycle deviation and phase deviation are normalized, and weighted operation is performed on the normalized amplitude deviation, frequency deviation, duty cycle deviation and phase deviation to obtain a comprehensive signal deviation.

[0084] In this embodiment, through normalization processing, each deviation can be expressed within the same numerical range. Specifically, each deviation can be expressed within the numerical interval [0,1]. Then, the amplitude deviation, frequency deviation, duty cycle deviation and phase deviation can be weighted and summed to obtain the comprehensive signal deviation.

[0085] Finally, the effectiveness detection result of the switch control signal is obtained according to the comprehensive deviation of the signal.

[0086] In a specific implementation, obtaining the validity detection result of the switch control signal according to the signal comprehensive deviation includes: If the signal comprehensive deviation is greater than or equal to the preset deviation upper limit value, the validity detection result is that the switch control signal is invalid.

[0087] If the signal comprehensive deviation is less than the preset deviation upper limit, the validity detection result is that the switch control signal is valid.

[0088] In this embodiment, the signal comprehensive deviation is compared with the preset deviation upper limit value, and then the validity of the switch control signal is detected according to the comparison result, which can avoid the problem of affecting the control reliability of the inverter-type distributed power supply when the switch control signal is invalid.

[0089] In one embodiment, after controlling the output voltage and output current of the inverter in the inverter-type distributed power supply by the switch control signal, the method may further include: First, the output voltage deviation rate, voltage fluctuation rate, output current total harmonic distortion rate and power factor of the inverter-type distributed power supply are determined.

[0090] When calculating the voltage deviation rate, the output voltage of the inverter may be subtracted from a preset voltage reference value to obtain a voltage difference value, and then the voltage difference value may be divided by the output voltage to obtain the output voltage deviation rate.

[0091] When calculating the voltage fluctuation rate, the maximum RMS value, the minimum RMS value and the average RMS value of the output voltage within a preset time period can be first determined, and then the maximum RMS value is subtracted from the minimum RMS value to obtain the RMS difference, and then the RMS difference is divided by the average RMS value to obtain the voltage fluctuation rate.

[0092] When calculating the total harmonic distortion rate of the output current, it can be calculated by the percentage of the square root of the sum of the squares of the effective values ​​of all harmonic components in the output current and the effective value of the fundamental current. In this embodiment, the total harmonic distortion rate of the output current should be less than 5%.

[0093] In this embodiment, the input power, output power, and phase difference between output voltage and output current of the inverter can be measured by a power analyzer to calculate the power factor. In this embodiment, the power factor should be greater than 0.95.

[0094] Then, according to the output voltage deviation rate, voltage fluctuation rate, output current total harmonic distortion rate and power factor, the key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

[0095] In one embodiment, according to the output voltage deviation rate, voltage fluctuation rate, output current total harmonic distortion rate and power factor, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted, specifically including: The output voltage deviation rate is subtracted from a preset deviation rate reference value, and a first difference obtained by the subtraction is divided by the output voltage deviation rate to obtain a voltage deviation error ratio.

[0096] The voltage fluctuation rate is subtracted from a preset fluctuation rate reference value, and a second difference obtained by the subtraction is divided by the voltage fluctuation rate to obtain a voltage fluctuation error ratio.

[0097] The total harmonic distortion rate of the output current is subtracted from a preset distortion rate reference value, and a third difference obtained by the subtraction is divided into the total harmonic distortion rate of the output current to obtain a current harmonic error ratio.

[0098] The preset power factor reference value is subtracted from the power factor, and a fourth difference obtained by the subtraction is divided by the power factor to obtain a power factor error ratio.

[0099] The first two with larger values ​​among the voltage deviation error ratio, voltage fluctuation error ratio, current harmonic error ratio and power factor error ratio are extracted to obtain the target error ratio.

[0100] According to the target error ratio, the key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

[0101] In a specific implementation, if the target error ratio includes the voltage deviation error ratio, indicating that the system steady-state error is too large, the process of adjusting the key parameters of the outer loop PID regulator and the inner loop PID regulator is as follows: First, increase the integral coefficient of the outer loop regulator and enhance the integral effect to eliminate the steady-state error. Specifically, the integral coefficient of the outer loop regulator can be increased by 10%-20%. In practical applications, a first corresponding relationship between the voltage deviation error ratio and the increase in the integral coefficient of the outer loop regulator can be established, and then the increase in the integral coefficient of the current outer loop regulator can be determined based on the first corresponding relationship and the current voltage deviation error ratio.

[0102] Then, the proportional coefficient of the inner loop regulator is fine-tuned. Specifically, the proportional coefficient of the inner loop regulator can be increased by 5%-10%. In practical applications, a second corresponding relationship between the voltage deviation error ratio and the increase in the proportional coefficient of the inner loop regulator can be established. Then, the increase in the proportional coefficient of the current inner loop regulator can be determined based on the second corresponding relationship and the current voltage deviation error ratio.

[0103] If the target error ratio includes the voltage fluctuation error ratio, indicating that the system dynamic response is poor, the process of adjusting the key parameters of the outer loop PID regulator and the inner loop PID regulator is as follows: Increase the proportional coefficient of the outer loop regulator to speed up the system's response to voltage changes. At the same time, increase the differential coefficient of the outer loop regulator to predict the voltage change trend in advance and suppress voltage fluctuations. Specifically, the proportional coefficient of the outer loop regulator and the differential coefficient of the outer loop regulator can be increased by 10%-20% respectively. In practical applications, a third corresponding relationship between the voltage fluctuation error ratio and the increase in the differential coefficient of the outer loop regulator and the increase in the proportional coefficient of the outer loop regulator can be established, and then the current increase in the proportional coefficient of the outer loop regulator and the increase in the differential coefficient of the outer loop regulator can be determined based on the third corresponding relationship and the current voltage fluctuation error ratio.

[0104] If the target error ratio includes the current harmonic error ratio, which may be caused by inaccurate current tracking, the process of adjusting the key parameters of the outer loop PID regulator and the inner loop PID regulator is as follows: First, increase the proportional coefficient of the inner loop regulator to improve the tracking speed and accuracy of the current inner loop to the current command. At the same time, increase the differential coefficient of the inner loop regulator to suppress the oscillation of the current and reduce the generation of harmonics. Specifically, the proportional coefficient and differential coefficient of the inner loop regulator can be increased by 10%-20% respectively. In practical applications, a fourth corresponding relationship between the current harmonic error ratio and the increase in the proportional coefficient and the increase in the differential coefficient of the inner loop regulator can be established. Subsequently, the increase in the proportional coefficient and the increase in the differential coefficient of the current inner loop regulator can be determined based on the fourth corresponding relationship and the current current harmonic error ratio.

[0105] Then, the integral coefficient of the outer loop regulator is reduced to avoid the adverse effect of integral saturation on the output current. Specifically, the integral coefficient of the outer loop regulator can be reduced by 5%-10%. In practical applications, a fifth corresponding relationship between the current harmonic error ratio and the reduction amount of the integral coefficient of the outer loop regulator can be established. Subsequently, the reduction amount of the integral coefficient of the current outer loop regulator can be determined based on the fifth corresponding relationship and the current current harmonic error ratio.

[0106] If the target error ratio includes the power factor error ratio, the process of adjusting the key parameters of the outer loop PID regulator and the inner loop PID regulator is as follows: First, increase the proportional coefficient of the outer loop regulator, improve the rapidity and accuracy of voltage control, make the phase relationship between the output voltage and the output current more reasonable, and at the same time, increase the integral coefficient of the outer loop regulator to eliminate the steady-state error of the output voltage and ensure the stable output of the voltage. Specifically, the proportional coefficient and integral coefficient of the outer loop regulator can be increased by 10%-20% respectively. In practical applications, a sixth corresponding relationship between the power factor error ratio and the increase in the proportional coefficient and the increase in the integral coefficient of the outer loop regulator can be established. Subsequently, the increase in the proportional coefficient and the increase in the integral coefficient of the current outer loop regulator can be determined based on the sixth corresponding relationship and the current power factor error ratio.

[0107] Then, increase the proportional coefficient of the inner loop regulator so that the output current can better track the output voltage and improve the power factor. Specifically, the proportional coefficient of the inner loop regulator can be increased by 10%-20%. In practical applications, the seventh corresponding relationship between the power factor error ratio and the increase in the proportional coefficient of the inner loop regulator can be established. Subsequently, the increase in the proportional coefficient of the current inner loop regulator can be determined based on the seventh corresponding relationship and the current power factor error ratio.

[0108] This embodiment uses the above coefficient adjustment strategy to optimize key parameters of the outer loop regulator and the inner loop regulator during the control process, further improving the control reliability of the inverter-type distributed power supply.

[0109] Based on the same general inventive concept, the present invention also protects a PID-based inverter-type distributed power supply control system. The PID-based inverter-type distributed power supply control system provided by the present invention is described below. The PID-based inverter-type distributed power supply control system described below and the PID-based inverter-type distributed power supply control method described above can be referenced to each other.

[0110] Figure 3 It is a structural diagram of a PID-based inverter-type distributed power supply control system provided in an embodiment of the present invention.

[0111] like Figure 3 As shown, the PID-based inverter-type distributed power supply control system provided by the embodiment of the present invention specifically includes: The acquisition module 210 is used to acquire the three-phase voltage and three-phase current output by the inverter in the inverter-type distributed power source.

[0112] The conversion module 220 is used to perform coordinate conversion on the three-phase voltage and the three-phase current respectively to obtain the decoupled voltage and the decoupled current.

[0113] The outer loop regulating module 230 is used to input the decoupling voltage into the outer loop PID regulator to obtain a reference current output by the outer loop PID regulator.

[0114] The inner loop regulating module 240 is used to input the reference current and the decoupling current into the inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator.

[0115] The validity detection module 250 is used to generate a switch control signal according to the decoupling modulation signal, and perform validity detection on the switch control signal to obtain a validity detection result.

[0116] The control module 260 is used to control the output voltage and output current of the inverter in the inverter-type distributed power supply through the switch control signal when the validity detection result is that the switch control signal is valid.

[0117] Regarding the system in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated again here.

[0118] The PID-based inverter distributed power supply control system provided in this embodiment adopts a dual-loop control strategy of voltage outer loop control and current inner loop control in the control link. When the entire system is subject to external interference, such as load mutation or grid voltage fluctuation, the voltage outer loop can adjust the output voltage in time, and at the same time the current inner loop can quickly respond to current changes, suppress current fluctuations, prevent overcurrent, and avoid damage to the inverter due to current mutations, thereby improving the anti-interference ability of the inverter distributed power supply and improving the control reliability and stability of the inverter distributed power supply.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A PID-based inverter-type distributed power supply control method, characterized in that: include: Obtaining the three-phase voltage and three-phase current output by the inverter in the inverter-type distributed power supply; Performing coordinate transformation on the three-phase voltage and the three-phase current respectively to obtain a decoupling voltage and a decoupling current; Inputting the decoupling voltage into an outer loop PID regulator to obtain a reference current output by the outer loop PID regulator; Inputting the reference current and the decoupling current into an inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator; generating a switch control signal according to the decoupling modulation signal, and performing validity detection on the switch control signal to obtain a validity detection result; If the validity detection result is that the switch control signal is valid, the output voltage and output current of the inverter in the inverter-type distributed power supply are controlled by the switch control signal.

2. The PID-based inverter-type distributed power supply control method according to claim 1, characterized in that: Performing coordinate transformation on the three-phase voltage and the three-phase current respectively to obtain a decoupled voltage and a decoupled current, including: Respectively converting the three-phase voltage and the three-phase current from a three-phase stationary coordinate system to a two-phase stationary coordinate system to obtain a two-phase voltage and a two-phase current; The two-phase voltage and the two-phase current are respectively converted from a two-phase stationary coordinate system to a synchronous rotating coordinate system to obtain a decoupled voltage and a decoupled current.

3. The PID-based inverter-type distributed power supply control method according to claim 1, characterized in that: The decoupling voltage includes: a d-axis voltage coordinate value and a q-axis voltage coordinate value; Inputting the decoupling voltage into an outer loop PID regulator to obtain a reference current output by the outer loop PID regulator, including: The d-axis voltage coordinate value is input into an outer loop PID regulator, and the outer loop PID regulator calculates the difference between a preset d-axis voltage reference value and the d-axis voltage coordinate value to obtain a d-axis voltage error value; Performing PID operation on the d-axis voltage error value to obtain a d-axis current reference value; The q-axis voltage coordinate value is input into an outer loop PID regulator, and the outer loop PID regulator calculates the difference between a preset q-axis voltage reference value and the q-axis voltage coordinate value to obtain a q-axis voltage error value; Performing PID operation on the q-axis voltage error value to obtain a q-axis current reference value; The d-axis current reference value and the q-axis current reference value are used as reference currents output by the outer-loop PID regulator.

4. The PID-based inverter-type distributed power supply control method according to claim 3, characterized in that: The decoupling current includes: a d-axis current coordinate value and a q-axis current coordinate value; Inputting the reference current and the decoupling current into an inner loop PID regulator to obtain a decoupling modulation signal output by the inner loop PID regulator, including: Inputting the d-axis current reference value and the d-axis current coordinate value into an inner loop PID regulator, calculating the difference between the d-axis current reference value and the d-axis current coordinate value through the inner loop PID regulator, and obtaining a d-axis current error value; Performing PID operation on the d-axis current error value to obtain a d-axis modulation signal; The q-axis current reference value and the q-axis current coordinate value are input into an inner loop PID regulator, and the inner loop PID regulator calculates the difference between the q-axis current reference value and the q-axis current coordinate value to obtain a q-axis current error value; Performing PID operation on the q-axis current error value to obtain a q-axis modulation signal; The d-axis modulation signal and the q-axis modulation signal are used as decoupling modulation signals output by the inner-loop PID regulator.

5. The PID-based inverter-type distributed power supply control method according to claim 4, characterized in that: Generating a switch control signal according to the decoupling modulation signal includes: Converting the d-axis modulation signal and the q-axis modulation signal in the decoupled modulation signal from a synchronous rotating coordinate system to a two-phase stationary coordinate system to obtain a two-phase modulation signal; Converting the two-phase modulation signal from a two-phase stationary coordinate system to a three-phase stationary coordinate system to obtain a three-phase modulation signal; The three-phase voltage wave values ​​in the three-phase modulation signal are compared with preset carrier reference values ​​respectively, and a switch control signal is generated according to the comparison result.

6. The PID-based inverter-type distributed power supply control method according to claim 1, characterized in that: Performing validity detection on the switch control signal to obtain a validity detection result includes: Respectively determining an amplitude deviation, a frequency deviation, a duty cycle deviation, and a phase deviation of the switch control signal; Normalizing the amplitude deviation, the frequency deviation, the duty cycle deviation, and the phase deviation, and performing weighted operation on the normalized amplitude deviation, the frequency deviation, the duty cycle deviation, and the phase deviation to obtain a signal comprehensive deviation; The validity detection result of the switch control signal is obtained according to the signal comprehensive deviation.

7. The PID-based inverter-type distributed power supply control method according to claim 6, characterized in that: Obtaining the validity detection result of the switch control signal according to the signal comprehensive deviation, including: If the signal comprehensive deviation is greater than or equal to the preset deviation upper limit value, the validity detection result is that the switch control signal is invalid; If the signal comprehensive deviation is less than the preset deviation upper limit, the validity detection result is that the switch control signal is valid.

8. The PID-based inverter-type distributed power supply control method according to claim 1, characterized in that: After controlling the output voltage and output current of the inverter in the inverter-type distributed power supply by the switch control signal, the method further includes: Determine the output voltage deviation rate, voltage fluctuation rate, output current total harmonic distortion rate and power factor of the inverter-type distributed power supply; According to the output voltage deviation rate, the voltage fluctuation rate, the output current total harmonic distortion rate and the power factor, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

9. The PID-based inverter-type distributed power supply control method according to claim 8, characterized in that: According to the output voltage deviation rate, the voltage fluctuation rate, the output current total harmonic distortion rate and the power factor, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted, including: Subtracting the output voltage deviation rate from a preset deviation rate reference value, and taking a first difference obtained by the subtraction as a quotient of the output voltage deviation rate to obtain a voltage deviation error ratio; Subtracting the voltage fluctuation rate from a preset fluctuation rate reference value, and dividing the voltage fluctuation rate by a second difference, to obtain a voltage fluctuation error ratio; Subtracting the output current total harmonic distortion rate from a preset distortion rate reference value, and dividing the third difference obtained by the difference by the output current total harmonic distortion rate to obtain a current harmonic error ratio; Subtracting a preset power factor reference value from the power factor, and dividing a fourth difference obtained by the subtraction by the power factor to obtain a power factor error ratio; Extracting the first two with larger values ​​among the voltage deviation error ratio, the voltage fluctuation error ratio, the current harmonic error ratio and the power factor error ratio to obtain a target error ratio; According to the target error ratio, key parameters of the outer loop PID regulator and the inner loop PID regulator are adjusted.

Images