96 results about "Shunt active power filter" patented technology

The present invention comprises a controller for the cascade H-bridge three-phase multilevel converter used as a shunt active filter. Based on the proposed mathematical model, the controller is designed to compensate harmonic distortion and reactive power due to a nonlinear distorting load. Simultaneously, the controller guarantees regulation and balance of all capacitor voltages. The idea behind the controller is to allow distortion of the current reference during the transients to guarantee regulation and balance of the capacitors voltages. The controller provides the duty ratios for each H-bridge of the cascade multilevel converter.

The invention discloses a novel control method of an LCL type three-phase shunt active power filter, which constructs a system of an active power filter with LCL filter based on an active damping optimization control method of a single-network-side inductance current feedback and a current tracking control method of a novel generalized integrator. A high-pass filter is added to the feedback loop to optimize the parameters, which overcomes the disadvantageous influence of the existing active damping method on the stability of the system in the fundamental domain. At that same resonant frequency, first-order generalized integrator with opposite phase order, As such, that novel generalize integrator realizes infinite gain only at the positive sequence resonant frequency or only at the negative sequence resonant frequency, The novel generalized integrator has the characteristics of selective compensation for positive and negative sequence signals with the same frequency, and can distributedifferent gains, reduce the complexity of control algorithm, improve the computational efficiency, solve the problem of harmonic compensation under the condition of unbalanced power network and load,and improve the compensation performance and flexibility of application.

The invention discloses an active power filter for detecting a harmonic wave and a wattless current and a detecting method thereof. The active power filter comprises a harmonic wave and wattless current detecting circuit and a compensating current generating circuit, wherein the harmonic wave and wattless current detecting circuit and the compensating current generating circuit are successively connected in series at the current side of a power grid. The compensating current generating circuit comprises a current tracking control module, a driving circuit module and a main circuit module, wherein the current tracking control module, the driving circuit module and the main circuit module are successively connected in series. The topological structure of the main circuit module is a three-phase four-leg PWM converter. Compared with prior art, a novel harmonic wave detecting algorithm according to the invention does not require a phase-locked loop or matrix transform, thereby effectively prevent a zero-sequence harmonic leakage error caused by coordinate conversion, greatly improving detecting precision and greatly improving compensation effect.

The invention discloses an integral power quality regulator. The integral power quality regulator comprises series-connection and parallel-connection active power filter units, a measuring unit and a control unit, wherein the parallel-connection active power filter unit and a parallel-connection passive filter unit are serially connected to each other to form a parallel-connection unit and are connected to a system in parallel; the series-connection active power filter unit is controlled by a series-connection control unit, and outputs sine-wave current by driving switch tubes of a first inverter unit; the parallel-connection active filter unit is controlled by a parallel-connection control unit and outputs appointed voltage by driving various switch tubes of a second inverter; and the parallel-connection passive filter unit is an LC (liquid chromatography) filter circuit, and is used for providing low-impedance access for load harmonic current and compensating reactive power of a load. By the integral power quality regulator, the shortcoming that the original parallel-connection active filter is high in capacity and high in manufacturing cost is overcome; a detection and control system is simple; an output tracking effect is high; a compensation effect is high; cost performance is also high; and hardware implementation is facilitated.

The invention discloses a parallel APF DC side voltage control method based on a sliding mode PI compound control algorithm. The method comprises the following steps: firstly establishing a low-order system model of a dq coordinate system by using synchronous rotating coordinate transformation; determining the sliding mode switching function of the DC side voltage according to the selection principle of sliding mode surfaces; and finally designing the control parameter output function of a PI controller according to the switching function of the sliding mode surfaces. By adopting the control method disclosed by the invention, the steady state performance and response speed of the DC side voltage can be improved, and the voltage fluctuation can also be effectively reduced; and a parallel APF control system based on the sliding mode PI compound control algorithm has good robust performance and dynamic performance. According to the parallel APF DC side voltage control method based on the sliding mode PI compound control algorithm disclosed by the invention, the parameter of the PI controller is determined through the sliding mode controller, the steady state accuracy and response speed during load sudden change and reference voltage jump can be increased, the power loss at the DC side can be reduced, and thus the compensation ability of the parallel APF (active power filter) can be ensured.

The invention discloses a synthetic electric-energy quality regulator, comprising series and parallel active filter units, measuring unit and control units, where the parallel active filter unit is connected in series with parallel passive filter unit to compose a parallel unit, which is connected to the system; the series active filter unit is under the control of the series control unit and outputs sinusoidal current by the driving of all the switches of the first inverter unit; the parallel active filter unit is controlled by the parallel control unit and outputs an specific voltage by the driving of all the switches of the second inverter unit; the parallel passive filter unit is a LC filter circuit to provide a low resistance pass for harmonic current of a load and compensate reactive power of the load. The invention overcomes the shortages of large capacity and high manufacturing cost of the original parallel active filter; and has a better tracking effect and a better compensating effect, as well as higher performance/cost trade-off.

The invention discloses an improved broadband self-adaption resonance control method for an active power filter. The method comprises the steps that the three-phase voltage of a common coupling point is collected, and a phase-locked loop is used to acquire the voltage frequency fpll and the phase theta; a harmonic detection module extracts the harmonic signal command of nonlinear load current iL; the harmonic signal command is added to an output active current command acquired through a direct current voltage controller; subtracting the command and an output current feedback signal to acquire the input error signal of a current controller; the current controller composed of a harmonic controller and a PI controller is used to acquire the output control amount; and the output control amount, the common coupling point voltage feed forward amount and the filter capacitor current feedback amount through an active damping module are added to acquire a PWM wave modulation instruction signal.

The invention provides a method for protecting a medium and high voltage electronic equipment from a sudden power failure, which belongs to the power and electronics equipment power failure protection technology field and is characterized in that energy on a DC side is converted onto a control circuit and a driving circuit by adopting energy feedback concept, which not only realizes the full utilization of energy, but also realizes the function of protecting power grid from failure. Compared with the protective measures by UPS or batteries, the method has the advantage of reliable work, small device volume, long service life and low cost, etc. The protecting method is used in a shunt active power filter, and the effectiveness is verified.

The invention discloses a DC side capacitance voltage control method for a star-shaped chained active power filter. The DC side capacitance voltage control method comprises three layers of control. The first layer control is three-phase overall DC voltage control and comprises the steps that positive and negative sequences as well as harmonic components of voltage and current are separated through a cross decoupling filter, and independent control of fundamental wave active-reactive components of the chained APF as well as grid voltage feedforward control are achieved by utilizing power decoupling control. The second layer control comprises the step of adjusting active distribution of various phases of current conversion chains through injecting a zero-phase fundamental wave voltage into various phases of reference voltages, so as to achieve phase-to-phase DC voltage control. The third layer control adopts parallel compound type fuzzy control, compensates current effective value and power unit DC side voltage deviation according to the chained APF, adjusts gain of the controller, and achieves equilibrium control of DC side voltage of an intra-phase power unit. The DC side capacitance voltage control method can improve the DC side voltage stability of devices under non-ideal voltage conditions, and achieves the stable and equilibrium control of the DC side voltage of the chained APF under asymmetric working conditions.

An adaptive dc-link voltage controlled LC coupling hybrid active power filter (LC-HAPF) for reactive power compensation includes: two dc capacitors to provide dc-link voltage; a three-phase voltage source inverter to convert dc-link voltage into compensating voltages; three coupling LC circuits to convert compensating voltages into currents; and an adaptive dc voltage controller with reactive power compensation control algorithm. The control algorithm includes: first, calculating required minimum dc-link voltage in each phase with respect to loading reactive power; three-phase required minimum dc-link voltage will be maximum one among their minimum values; compare it with predetermined voltage levels to determine final reference dc-link voltage. A dc-link voltage feedback P/PI controller outputs dc voltage reference compensating currents. An instantaneous power compensation controller outputs reactive reference compensating currents. The final reference compensating currents will be sum of them. A PWM circuit provides LC-HAPF adaptive dc-link voltage control and dynamic reactive power compensation.

The invention discloses a method for fixed-time ring-width-variable current control of a three-phase three-wire system SAPF (Shunt Active Power Filter). The method comprises the following steps of: decoupling a three-phase current; carrying out single-phase analysis to obtain a calculation formula for ring-width-variable hysteresis control; and discretizing the obtained calculation formula for the ring-width-variable hysteresis control, and introducing a fixed-time control time Ts. The method retains the advantages of high tracking precision and rapid dynamic response of the traditional current hysteresis control method, simultaneously effectively limits the maximal switching frequency and fluctuation range of a switching device, reduces switching loss and mechanical noise, and facilitates the design of a filter circuit at an outlet side of the SAPF; and the invention provides the discretization control method for ring-width-variable current control based on a fixed time principle, and the discretization control method is applicable to an SAPF system taking DSP (Digital Signal Processor) as a core control chip and has a good engineering application prospect.

The invention belongs to the technical field of three-phase active power filter, in particular to a three-phase active power filter based on LCL filter and a control method thereof. Three-phase activepower filter based on LCL filter includes a three-phase inverter, an output filter and a control system. The three-phase inverter is a voltage-type inverter, and the energy storage original is a direct current capacitor; The output filter is a third-order filter, comprising an inverter-side filter inductor, a filter capacitor and a grid-side filter inductor; The control system is a current doubleclosed loop control of current detection and current feedback at the inverter side. The invention directly controls the harmonic component of the electric network current through the electric networkcurrent closed-loop control mode, thereby avoiding the detection delay and the assignment phase offset existing in the traditional load current detection method. Virtual damping is introduced to suppress the resonant peak of LCL filter through current feedback on inverter side.

The invention discloses a self-adaptive radial basis function (RBF) neural sliding mode control method for a three-phase shunt active power filter. According to the method, a mathematical model of an Active Power Filter (APF) is established; a switching function is used as the input of an RBF neural network while a sliding mode controller is used as the output of the RBF neural network; and single-input and single-output neural sliding mode control is realized by using the learning function of the neural network. According to the control scheme, the advantages of sliding mode control, self-adaptive algorithm and the RBF neural network are synthesized, harmonic waves in supply current can be detected and tracked timely, and the purposes of eliminating harmonic waves and improving the quality of electric energy can be achieved through the production of compensation currents which are equal in size and opposite in direction. Moreover, the self-adaptive RBF sliding mode control plot can online adjust the weight of the neural network in an online manner and guarantees the stability of the system based on Lyapunov theory.

The invention discloses an active power filter based on inverter side current feedback and a current control method of the active power filter. The active power filter comprises an APF (active power filter) system and an LCL filter, and the APF system is in a three-phase bridge type parallel structure. The current control method includes that feedback current of a current closed-loop control system takes inverter side current i1, a master controller GA (s) adopts PI control, and capacitance current feedback control is adopted. By means of feedback adjustment of LCL filter capacitance current on the basis of traditional feedback control of single inverter side current, control precision of the system is improved while resonance of the LCL filter and power grid parameters can be restrained.

The invention discloses an optimization control method for dynamic performances of an active power filter of a microgrid. A harmonic current detection link employs a combined filter of a specific subharmonic wave trap and a low-pass filter, wherein the specific subharmonic wave trap filters low-order harmonics, and the low-pass filter is wider in frequency band and filters high-order harmonics, thereby effectively overcoming the conflict between the bandwidth and response time of a conventional filter. A current control link carries out the independent control of a fundamental current and a harmonic current in a dq synchronous rotation system, thereby solving a problem that a DC side voltage drops during load varying. According to a control strategy, an AC side current and a DC side voltage are better in dynamic response and stability, and the method is suitable for the active power filter of the microgrid. The method is higher in harmonic detection speed, and is better in dynamic performance.

An LADRC (linear active disturbance rejection controller) control based three-level shunt active power filter system is characterized by comprising a sampling and conditioning circuit unit, a DSP (digital signal processor) control unit, an IGBT (insulated gate bipolar transistor) isolation driving circuit unit, a protection circuit unit and a main circuit unit. A method of the LADRC control based three-level shunt active power filter system includes the steps of sampling and conditioning, DSP control processing, PWM (pulse width modulation) outputting, driving and transmitting. The control based three-level shunt active power filter system has the advantages that device design in simple, an advanced linear active disturbance rejection technology is adopted, high control accuracy is kept, system reliability is improved greatly, and the system has promising market prospect and engineering application value.

The invention discloses a composite circuit integrating rectification, active power filtering and energy feedback braking functions, which comprises a rectification unit, an active power filtering and reactive power compensation unit and a clamping circuit, wherein the rectification unit and the active power filtering and reactive power compensation unit are directly connected at an alternating current side, the rectification unit and the active power filtering and reactive power compensation unit are connected at a direct current side through the clamping circuit, and the clamping circuit is connected between the active power filtering and reactive power compensation unit and a DC bus and provides a circuit for feeding energy back to a power grid through an active power filtering unit from a braking load. The composite circuit disclosed by the invention can carry out good compensation on harmonic current in a power grid of a drilling platform, an overvoltage effect generated when a winch drops is also solved, the feedback load brakes energy to the power grid, and the energy-saving efficiency is high.

The invention discloses a double-resonance three-phase active power filter, and a control method and device, and solves the problems that in the prior art, the passive power filter is composed of an electric reactor, a capacitor and a resistor, while the compensation reactive power is achieved, the function of restraining the specific harmonic current is often taken into consideration, the passivepower filter is simple in structure and low in cost, but the influence of the frequency fluctuation of the power grid and other loads is large, and the technical problem that the performance of the filter is greatly influenced due to detuning of the filter is solved; the active power filter is a device for dynamically compensating harmonic current, all harmonic currents can be compensated, and specific harmonic currents can be compensated, but the active power filter is limited by the working voltage of the power electronic power device, and the cost is increased along with the increasing ofcapacity, and therefore the active power filter has the technical problem of being not suitable for a high-voltage system.

The invention discloses a DSP (Digital Signal Processor) and SAPF (Shunt Active Power Filter)-based real-time phase shift detection system, which is characterized by comprising a signal reshaping and transformation processing circuit, a DSP central data processing circuit, an isolating and driving circuit and a thyristor circuit. A working method of the DSP and SAPF-based real-time phase shift detection system comprises coordinate transformation, filtration, calculation, phase shift and coordinate inverse transformation. The system and the working method thereof have the advantages that 1 three-phase voltage distortion, and fundamental wave positive sequence active current in case of asymmetry can be detected in real time by using a real-time phase shift method, 2 the speed and the accuracy of control are improved and the system has excellent adjustment performance and reliability, 3 the device capacity and the voltage level are greatly improved, the stability of a power grid is enhanced, and operation of the entire system is prevented from being influenced by harmonic pollution, and 4 the system and the working method thereof have broad market application prospect.

The invention discloses a Z-source inverter shunt active power filter and a control method thereof. The Z-source inverter shunt active power filter comprises a power grid, a non-linear load, an output inducer, a Z-source inverter and a control circuit; the Z-source inverter comprises a direct-current source, a bilateral switch, a Z-source network and an inverter, the direct-current source is connected with the inverter through the Z-source network, and the bilateral switch is connected between the anode of the direct-current source and the Z-source network; a control system comprises a controller, a sensor unit and a power unit, the sensor unit comprises a voltage sensor for detecting the voltage of the power grid, a current sensor for detecting the current of the non-linear load, a current sensor for detecting the compensation command current of the inverter and a voltage sensor for detecting the voltage of the direct-current source, and the controller acquires the signals of the sensors, and controls the bilateral switch and the inverter by means of the acquired voltage values and current values. The filter dispenses the dead time in switching signals, and decreases the complexity of control, and the output current waveform is fundamentally not affected by direct-current voltage.