CN114362180B - LCL type grid-connected inverter compensation method, system, storage medium and computing equipment - Google Patents
LCL type grid-connected inverter compensation method, system, storage medium and computing equipment Download PDFInfo
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Abstract
The invention discloses a compensation method, a compensation system, a storage medium and a computing device for an LCL type grid-connected inverter, wherein the method is based on a topological structure of an LCL type grid-connected inverter system under a weak power grid environment, and a small signal model of the LCL type grid-connected inverter considering PLL influence is established; secondly, a phase-locked loop structure containing a low-pass filter is proposed from the improvement of the phase-locked loop structure; and finally, considering the influence of power grid background harmonic waves, providing a self-adaptive small signal compensation method based on deep reinforcement learning, and compensating disturbance caused by a phase-locked loop. The invention can widen the power grid impedance adaptation range of the system and effectively improve the robustness of the grid-connected inverter under the condition of weak power grid.
Description
Technical Field
The invention relates to a compensation method, a compensation system, a storage medium and a computing device for an LCL type grid-connected inverter, and belongs to the technical field of grid-connected control.
Background
Grid-connected inverters are generally used as an interface between a distributed power generation system and a public power grid, and electric energy generated by renewable energy sources is injected into the power grid in the form of alternating current. With the position distribution of the distributed power supply becoming more and more extensive, the power grid gradually shows weak grid characteristics, the strength degree of the power grid is generally described by a Short Circuit Ratio (SCR), the larger the impedance of the power grid is, the smaller the SCR value is, the stronger the weak grid characteristics of the system are, at the moment, the line voltage drop of grid-connected current flowing through the impedance of the power grid cannot be ignored, and the voltage of a public coupling Point (PCC) is not approximate to the voltage of the power grid any more.
In weak grid situations, the effect of Phase Locked Loops (PLLs) on system stability is gradually increased with increasing grid impedance. Grid impedance and grid current are the amount of interference for the PLL output phase. When the impedance of the power grid is increased and the grid-connected current is increased, the dynamic and static performances of the output phase of the power grid are influenced, and the robustness of the PLL is reduced. The deterioration of the performance of the phase-locked loop causes the distortion of the reference current, further causes the distortion of the network access current, the oscillation of the network access power, and even leads the whole inverter not to stably operate and to be cut off from the power grid by the protection device in serious conditions. The existing grid-connected inverter control method considering PLL influence mainly improves the adaptability of a grid-connected system to a weak power grid from a phase-locked loop structure or inverter output impedance remodeling. However, under a weak power grid, due to the influence of the fluctuation of distributed new energy power generation units such as wind power and photovoltaic power generation units, loads and the like, background harmonic waves exist in the power grid, the inductance of the power grid is in wide-range change, and the quality of grid-connected current and the stability of a grid-connected system are difficult to guarantee only from the aspect of improving a phase-locked loop structure or remolding the output impedance of an inverter.
Disclosure of Invention
The invention aims to provide a compensation method, a compensation system, a storage medium and a computing device for an LCL type grid-connected inverter.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a LCL type grid-connected inverter compensation method, which comprises the following steps: a low-pass filter is added in front of a phase-locked loop q-axis PI controller of the LCL type grid-connected inverter system, so that high-frequency disturbance components of PCC (point of common coupling) voltage are filtered;
and compensating the low-frequency harmonic disturbance component of the power grid by adopting the following method:
the frequency of a phase-locked loop of the LCL type grid-connected inverter system, the frequency error of the phase-locked loop and the integral of the frequency error are used as the input of the DDPG intelligent body to obtain the optimal compensation coefficient
And &>
Optimal compensation factor
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop;
and compensating the grid-connected current disturbance compensation quantity into the q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into the grid-connected voltage position.
Further, the low pass filter transfer function is:
wherein G is LPF As a low pass filter transfer function, ω c For the low pass filter cut-off frequency, s is the laplacian operator.
Further, the phase-locked loop transfer function is expressed as:
wherein,
for the transfer function of the phase-locked loop, H PLL (s)＝k ppll +k ipll Is the phase-locked loop PI controller, k ppll 、k ipll Proportional coefficient and integral coefficient, respectively, for a phase locked loop PI controller>
Is the d-axis pcc voltage steady-state value.
The invention also provides an LCL type grid-connected inverter compensation system, which comprises a DDPG intelligent agent, a compensation module and a low-pass filter;
the low-pass filter is positioned in front of a q-axis PI controller of the phase-locked loop and used for filtering out high-frequency disturbance components of PCC (point of common coupling) voltage;
the DDPG intelligent agent is used for generating an optimal compensation coefficient by taking the phase-locked loop frequency, the phase-locked loop frequency error and the integral of the frequency error of the LCL type grid-connected inverter system as input signals
And &>
The compensation module is used for optimizing the compensation coefficient
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop; and compensating the grid-connected current disturbance compensation quantity into the q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into the grid-connected voltage position.
Further, in the above-mentioned case,
the low pass filter transfer function is:
wherein G is LPF As a low pass filter transfer function, ω c Is the low pass filter cut-off frequency and s is the laplacian.
Further, the low-pass filter cuts off the frequency ω c 2200Hz was taken.
Further, in the compensation module, the phase-locked loop transfer function is expressed as:
wherein,
for phase-locked loop transfer function, H PLL (s)＝k ppll +k ipll Is the phase-locked loop PI controller, k ppll 、k ipll Proportional coefficient and integral coefficient, respectively, for a phase locked loop PI controller>
Is the d-axis pcc voltage steady-state value.
Further, the DDPG agent employs the following equation as a reward function:
where r is the reward function, f is the PLL frequency, f 0 Is the power frequency.
A third aspect of the invention provides a computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a method according to any of the foregoing methods.
A fourth aspect of the invention provides a computing device comprising,
one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the foregoing methods.
The invention achieves the following beneficial effects:
the invention provides a compensation method and a compensation system for an LCL type grid-connected inverter. The invention can effectively solve the problems of grid-connected current distortion, grid-connected system instability and the like caused by the phase-locked loop under the weak grid condition, enhances the adaptability of the grid-connected inverter to wide-range impedance change, can keep small steady-state error of the phase-locked loop frequency even under the condition of the existence of grid background harmonic waves, and effectively improves the reliability and robustness of the grid-connected inverter system.
Drawings
FIG. 1 is a topological structure diagram of an LCL type grid-connected inverter system;
FIG. 2 is a control block diagram of a q-axis of an LCL type grid-connected inverter;
FIG. 3 is a simplified q-axis control block diagram of an LCL grid-connected inverter;
FIG. 4 is a topology of an improved PLL of the present invention;
fig. 5 is a small signal compensation control block diagram of the LCL type grid-connected inverter provided by the present invention;
fig. 6 is a block diagram of adaptive small-signal compensation control of the LCL type grid-connected inverter provided by the present invention;
FIG. 7 is a diagram of the internal network architecture of DDPG;
FIG. 8 is a simulation diagram of the frequency of a conventional PLL before compensation is added to the PLL according to an embodiment of the present invention;
FIG. 9 is a simulation diagram of grid-connected three-phase voltage and current before compensation is added to a traditional phase-locked loop in the embodiment of the invention;
FIG. 10 is a diagram of a frequency simulation after adaptive small signal compensation is added using an improved phase locked loop in an embodiment of the present invention;
fig. 11 is a simulation diagram of grid-connected three-phase voltage and current after adaptive small-signal compensation is added by using an improved phase-locked loop in the embodiment of the present invention.
Detailed Description
The invention is further described below. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The invention provides a LCL type grid-connected inverter compensation method, which comprises the following steps:
a low-pass filter is added in front of a phase-locked loop q-axis PI controller of the LCL type grid-connected inverter system, and a PCC voltage high-frequency disturbance component is filtered;
and compensating the low-frequency harmonic disturbance component of the power grid by adopting the following method:
the frequency of a phase-locked loop of the LCL type grid-connected inverter system, the frequency error of the phase-locked loop and the integral of the frequency error are used as the input of the DDPG intelligent body to obtain the optimal compensation coefficient
And &>
Optimal compensation factor
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop;
and compensating the grid-connected current disturbance compensation quantity into a q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into a grid-connected voltage position.
As a preferred implementation manner, this embodiment provides an adaptive small-signal compensation method for an LCL type grid-connected inverter, which specifically includes:
firstly, a topological structure of an LCL type grid-connected inverter system in a weak power grid environment is described, and a small signal model of the LCL type grid-connected inverter considering PLL influence is established. As shown in fig. 1, the LCL type grid-connected inverter system is based on a hybrid coordinate system structure, where L is 1 ,L 2 ,C f Respectively an inverter side inductor, a network side inductor, a filter capacitor and U dc Is a DC side voltage u a ,u b ,u c Bridge arm voltages of three phases a, b and c, U ga ,U gb ,U gc A, b, c three-phase grid voltages, ω 0 For the angular frequency of the power grid, a, b, c three-phase point voltage of common coupling U pcc_abc The phase angle is output to theta, K through PLL c For the feedback coefficient of capacitance and current, the current loop adopts PI controller with expression G i ＝(k p +k i /s)，k p 、k i Proportional and integral coefficients, I, of the PI controller, respectively 1 ,I 2 ,I c Bridge arm current, grid-connected current and capacitance current respectively. The control principle is as follows: a, b, c three-phase grid-connected current I 2_abc I obtained after park transformation 2d ,I 2q Are respectively d-axisAnd q-axis grid-connected current actual value, I 2d ,I 2q Grid-connected current reference value with d axis and q axis
Inputting the difference into a PI controller, decoupling output signals of the PI controller, performing park inverse transformation, and subtracting a signal subjected to park inverse transformation and a capacitance current feedback signal by adopting a capacitance current feedback active damping method to obtain an input signal U of SVPWM (space vector pulse width modulation) in order to inhibit high-frequency resonance introduced by LCL (lower control level) rα And U rβ And the SVPWM module outputs PWM signals to control the on and off of the IGBT, thereby realizing grid connection. Because the public coupling Point (PCC) voltage is easy to be interfered under the condition of weak power grid, thereby influencing the dynamic characteristic of the phase-locked loop, the phase angle theta of the power grid voltage and the phase-locked loop output phase angle theta PLL There is a deviation Δ θ between. The presence of Δ θ divides the dq axis into a system dq axis and a controller dq axis, now θ PLL And the reference coordinate axes of θ are defined as a c-domain and an s-domain, respectively. The relationship of variable x between these two domains can be expressed as:
in the formula: the subscripts "d" and "q" represent the d-axis and q-axis, respectively; subscript "0" indicates the steady state value; Δ x represents a small-signal disturbance variable.
The q-axis control block diagram of the grid-connected inverter current loop is shown in FIG. 2, wherein U pccq 、U rq And I cq Q-axis PCC voltage, q-axis modulation voltage and q-axis capacitance current, G de And(s) is control delay, and the expression is as follows:
wherein, T s Is the sampling period.
Fig. 2 can be simplified to fig. 3 by a control block diagram equivalent transformation, wherein,
system loop gain T A Can be expressed as:
T A (s)＝G x1 (s)G x2 (s)G de (s)G i (s) (5)
the phase-locked loop small signal model is as follows:
wherein, G PLL (s) is a phase locked loop transfer function expressed as
H PLL (s)＝k ppll +k ipll Is the phase-locked loop PI controller, k ppll 、k ipll Proportional term coefficient and integral term coefficient of the phase-locked loop PI controller, respectively>
Is the d-axis PCC voltage steady state value>
And the small signal disturbance quantity is the PCC voltage. Substituting formula (6) into formula (1) to obtain:
assuming that under the condition of unit power factor, the steady state value of the q axis of the system
Is 0 and the dynamic characteristics of the PLL only influence the grid current I 2q And a modulation voltage U rq That is to say that,
wherein,
respectively modulating the small signal disturbance quantity of the q-axis modulation voltage of the controller and the small signal disturbance quantity of the q-axis modulation voltage of the system, and then combining>
Modulating a steady state value of the voltage for the system d-axis>
For the small signal disturbance quantity of the q-axis grid-connected current of the controller>
And the steady-state value is the grid-connected current steady-state value of the system d axis.
Under a weak grid, the q-axis output impedance of the grid-connected inverter can be expressed as:
wherein,
the q-axis grid-connected current small signal disturbance amount can be expressed as,
it can be known from equation (13) that the grid-connected current disturbance caused by the phase-locked loop can be effectively reduced by compensating the q-axis grid-connected current and the modulation voltage.
For suppressing high-frequency disturbance component of PCC voltage, reducing the power grid impedance
The influence on the phase angle output by the phase-locked loop is based on the small signal model of the LCL grid-connected inverter established in the foregoing, and a phase-locked loop structure including a low-pass filter is proposed from the point of improving the phase-locked loop structure, as shown in fig. 4. On the basis of the traditional phase-locked loop, a low-pass filter is added in front of a q-axis PI controller of the phase-locked loop, the transfer function of the low-pass filter can be expressed as,
wherein omega c To cut-off frequency, ω c The smaller the interference rejection, the better, but the smaller ω c Resulting in a slower response speed. Comprehensively considering, the invention selects omega c ＝2200。
As known from cut-off frequency, the low-pass filter can effectively filter more than 7 times of harmonic waves in PCC voltage, but the power grid has abundant low-order background harmonic waves, the harmonic waves can influence a grid-connected control system through a phase-locked loop, the good grid-connected current quality of a grid-connected inverter can not be ensured only by improving the structure of the phase-locked loop, and small signal disturbance at the modulation voltage and grid-connected current of the grid-connected inverter after the low-pass filter is added can be expressed as,
it can be known from equation (13) that grid-connected current disturbance caused by the phase-locked loop can be effectively reduced by compensating the q-axis grid-connected current and the modulation voltage. Assuming that the grid-connected inverter works under the unit power factor and the grid voltage has no fluctuation, the grid current steady-state value
Is equal to the set d-axis current reference value->
Modulation voltage steady-state value>
Can be approximately equal to the network voltage>
As shown in fig. 5, the influence of the phase-locked loop on the grid-connected current can be eliminated by adding corresponding compensation at the grid-connected current feedback loop and the modulation voltage, respectively. But the above approximate equivalence is no longer true when considering the presence of grid background harmonics.
In order to improve the adaptability of wide-range change of impedance of the grid-connected inverter under the condition of existence of power grid background harmonic waves, on the basis of improving a phase-locked loop structure, self-adaptive compensation is added, and a Deep Deterministic Policy Gradient (DDPG) algorithm in Deep reinforcement learning is adopted to perform self-adaptive compensation on modulation voltage and grid-connected current and improve grid-connected current distortion under the condition of weak power grid.
The deep determination strategy gradient strategy based on deep reinforcement learning is divided into two modules, namely an environment module and an intelligent agent module, wherein the environment module is a physical model of a grid-connected inverter, the intelligent agent module comprises a strategy (deep neural network) and a reinforcement learning algorithm, the reinforcement learning algorithm continuously updates the strategy module according to an observed value (observer) and an incentive (Reward) in the training process, and an Action instruction (Action) generated by the strategy module acts on the grid-connected inverter, so that closed-loop control between the grid-connected inverter and the intelligent agent module is formed.
DDPG adaptive compensation control is adopted, as shown in figure 6, to perform adaptive compensation on the modulation voltage disturbance quantity and the grid-connected current disturbance quantity (formulas 15, 16 and 17), namely, an optimal compensation coefficient is obtained by taking the integral of the frequency error and the frequency error of a phase-locked loop as the input of DDPG through an algorithm
And &>
To compensate for disturbance components introduced by a phase-locked loop, and to sum the compensation coefficients>
Obtaining the grid-connected current disturbance compensation quantity (formula (17)) after the phase-locked loop, and compensating the q-axis grid-connected current I 2q Then combining with a q-axis grid-connected current reference value>
Inputting the difference into a q-axis PI controller; decoupling the output of the q-axis PI controller to obtain grid-connected voltage;
will compensate the coefficient
Obtaining a modulation voltage disturbance compensation quantity (formula (16)) through a phase-locked loop, and performing park inverse transformation after compensating the modulation voltage disturbance compensation quantity to a grid-connected voltage;
and finally, subtracting the signal subjected to park inverse transformation from the capacitance current feedback signal to obtain an input signal of SVPWM (space vector pulse width modulation) and outputting a PWM (pulse width modulation) signal through an SVPWM module to control the on-off of the IGBT, thereby realizing grid connection.
Wherein the phase-locked loop transfer function is
The frequency f and the error signal f of the phase-locked loop 0 -f and the error signal integral ^ f (f) 0 -f) as observed signal of DDPG, noted s = { f, f 0 -f,∫(f 0 -f) }, wherein f 0 Is the power frequency;
the value of the controlled quantity f obtained by the reward function module is used as the reward of the DDPG and is marked as r; the reward function is shown as equation (18).
The output action of DDPG is compensation coefficient
And &>
Marked as a, based on the strategy gradient method, the calculation strategy function of DDPG is shown as formula (19),
J(π θ )＝∫∫ρ(s)π θ (s,a)r(s,a)dads＝E s-ρ [r(s,a)] (19)
further increasing J (pi) θ ) The gradient of (a) is, that is,
in the formula, pi θ A strategy with a parameter theta; j is a policy function; rho is the probability distribution of the strategy; e s-ρ Obey the desire of the ρ distribution for s;
is a gradient; q (s, a) is the cost function of strategy pi under the condition that the observation is s and the action is a. Through iteration, the optimal compensation amount can be given.
In order to obtain the optimal compensation amount in a stable range, the DDPG algorithm is an important branch of deep reinforcement learning, the internal structure of the DDPG is shown in figure 7, the algorithm adopts an actuator-evaluator structure, an experience playback area is used for storing interaction information between an intelligent agent and the environment, and during off-line training, in order to avoid experience coupling, random batch sampling is carried out from the experience playback area every time to train network parameters. The evaluator goal is to obtain the best estimate and to compute a cost function from the obtained reward to correctly evaluate the current action of the actuator.
Examples
Matlab/Simulink is adopted for simulation, the specific training parameters of the DDPG algorithm are shown in the table 1, the parameter settings of the LCL type grid-connected inverter in the table 2 are shown in the table 2,
TABLE 1 DDPG algorithm training parameters
TABLE 2 LCL type grid-connected inverter parameters
The method of the invention is compared with the traditional method under the same weak grid environment.
When the impedance of the power grid is 15mH, 3% of 7-order harmonic and 2% of 5-order harmonic are added through a three-phase programmable voltage source, the uncompensated simulation result of the traditional phase-locked loop is adopted as shown in figures 8 and 9, the PLL error is about 15Hz, the grid-connected current is obviously distorted under the influence of the voltage distortion of the power grid, and the current distortion rate THD is 8.07%. The simulation results of the method provided by the invention are shown in fig. 10 and fig. 11, the error of the PLL is about 0.7Hz, the grid-connected current waveform is improved, and the current distortion rate THD is 2.07%.
According to simulation results, the LCL type grid-connected inverter self-adaptive small signal compensation method based on deep reinforcement learning can effectively solve the problems of grid-connected current distortion, grid-connected system instability and the like caused by the phase-locked loop under the weak grid condition, the adaptability of the grid-connected inverter to wide-range changes of impedance is enhanced, the frequency of the phase-locked loop can still keep a small steady-state error even under the condition that grid background harmonic exists, and the reliability and robustness of a grid-connected inverter control system can be effectively improved by the control method.
Another embodiment of the invention provides an LCL type grid-connected inverter self-adaptive small signal compensation system, which comprises a DDPG intelligent agent and a compensation module;
the DDPG intelligent agent is used for generating an optimal compensation coefficient by taking the phase-locked loop frequency, the phase-locked loop frequency error and the integral of the frequency error of the LCL type grid-connected inverter system as input signals
And &>
The compensation module is used for optimizing the compensation coefficient
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop; and compensating the grid-connected current disturbance compensation quantity into a q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into a grid-connected voltage position.
In this embodiment, the DDPG agent obtains the optimal compensation coefficient by calculating using a depth determination policy gradient algorithm
And &>
In this embodiment, the DDPG agent uses the following equation as the reward function:
where r is the reward function, f is the PLL frequency, f 0 Is the power frequency.
Preferably, the system further comprises a low-pass filter, the low-pass filter is positioned in front of the q-axis PI controller of the phase-locked loop,
the low pass filter transfer function is:
wherein G is LBF As a low pass filter transfer function, ω c Is the low pass filter cut-off frequency and s is the laplacian.
Preferably, the low-pass filter cuts off the frequency ω c 2200Hz was taken.
Another embodiment of the invention provides a computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a method according to any of the foregoing methods.
Another aspect of the invention provides a computing device comprising,
one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the foregoing methods.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A LCL type grid-connected inverter compensation method is characterized by comprising the following steps:
a low-pass filter is added in front of a phase-locked loop q-axis PI controller of the LCL type grid-connected inverter system, so that high-frequency disturbance components of PCC (point of common coupling) voltage are filtered;
and compensating the low-frequency harmonic disturbance component of the power grid by adopting the following method:
the frequency of a phase-locked loop of the LCL type grid-connected inverter system, the frequency error of the phase-locked loop and the integral of the frequency error are used as the input of the DDPG intelligent body to obtain the optimal compensation coefficient
And &>
Optimal compensation factor
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop;
and compensating the grid-connected current disturbance compensation quantity into the q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into the grid-connected voltage position.
2. The LCL type grid-connected inverter compensation method according to claim 1,
the low pass filter transfer function is:
wherein G is LPF As a low pass filter transfer function, ω c For the low pass filter cut-off frequency, s is the laplacian operator.
3. The LCL grid-connected inverter compensation method according to claim 2, wherein the phase-locked loop transfer function is expressed as:
wherein,
for the transfer function of the phase-locked loop, H PLL (s)＝k ppll +k ipll Is the phase-locked loop PI controller, k ppll 、k ipll Proportional term coefficient and integral term coefficient of the phase-locked loop PI controller, respectively>
Is the d-axis pcc voltage steady-state value.
4. An LCL grid-connected inverter compensation system is characterized by comprising a DDPG intelligent agent, a compensation module and a low-pass filter,
the low-pass filter is positioned in front of a q-axis PI controller of the phase-locked loop and used for filtering out high-frequency disturbance components of PCC (point of common coupling) voltage;
the DDPG intelligent agent is used for generating an optimal compensation coefficient by taking the phase-locked loop frequency of the LCL type grid-connected inverter system, the phase-locked loop frequency error and the integral of the frequency error as input signals
And &>
The compensation module is used for optimizing the compensation coefficient
And &>
Obtaining grid-connected current disturbance compensation quantity and modulation voltage disturbance compensation quantity after phase-locked loop; and compensating the grid-connected current disturbance compensation quantity into the q-axis grid-connected current position, and compensating the modulation voltage disturbance compensation quantity into the grid-connected voltage position.
5. LCL-type grid-connected inverter compensation system according to claim 4,
the low pass filter transfer function is:
wherein G is LPF As a low pass filter transfer function, ω c For the low pass filter cut-off frequency, s is the laplacian operator.
6. The LCL grid-connected inverter compensation system according to claim 5, wherein the phase-locked loop transfer function in the compensation module is expressed as:
wherein,
for the transfer function of the phase-locked loop, H PLL (s)＝k ppll +k ipll Is the phase-locked loop PI controller, k ppll 、k ipll Proportional term coefficient and integral term coefficient of the phase-locked loop PI controller, respectively>
Is the d-axis pcc voltage steady-state value.
7. The LCL grid-connected inverter compensation system according to claim 4, wherein the DDPG agent employs the following formula as a reward function:
where r is the reward function, f is the PLL frequency, f 0 Is the power frequency.
8. LCL grid-connected inverter compensation system according to claim 5, characterized in that said low pass filter cut-off frequency ω is such that c 2200Hz was taken.
9. A computer readable storage medium storing one or more programs, characterized in that: the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods of claims 1-3.
10. A computing device, characterized by: comprises the steps of (a) preparing a substrate,
one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods of claims 1-3.
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