AC excitation synchronous condenser and control method thereof

Patent metadata

Field	Value
Publication number	US-10411627-B2
Application number	US-201815933856-A
Country	US
Kind code	B2
Filing date	Mar 23, 2018
Priority date	Dec 25, 2017
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

An AC excitation synchronous condenser and a control method, an AC-excitation induction machine, a full-controlled AC excitation converter, a grid-side converter and a controller. The AC-excitation induction machine is the core power converting device, and its stator and rotor windings are AC windings with terminals. The controller is configured to control the full-controlled AC excitation converter to perform excitation and speed regulation on the AC-excitation induction machine and also control the grid-side converter to ensure the excitation capability of the full-controlled AC excitation converter, so that support and regulation of the active power and reactive power are achieved.

First claim

The invention claimed is:

1. An AC excitation synchronous condenser, comprising: an AC-excitation induction machine, a full-controlled AC excitation converter, a grid-side converter and a controller; wherein the AC-excitation induction machine is the core power converting device, and stator and rotor windings of the AC-excitation induction machine are AC windings with terminals; wherein the controller is configured to process voltage, current and rotating speed signals so as to generate an excitation voltage command for the full-controlled AC excitation converter and control voltage command for the grid-side converter and comprises: an event and command control module, a rotating speed and reactive power control module, an excitation current control module and a DC voltage control module;
the event and command control module has a first input terminal for receiving a superior reactive power command (Q in *) and a second input terminal for receiving voltage and frequency signals of the local power grid, and is configured to receive the superior reactive power command (Q in *), collect a measured voltage (U) and a measured frequency f and then process the input signals according to a working mode, a rated voltage U N , a rated frequency f N , a maximum rotating speed command ω r max * and a minimum rotating speed command ω r min * that are preset, so as to obtain a reactive power command (Q*) and a rotating speed command (ω r *);
the rotating speed and reactive power control module has a first input terminal which is connected to a first output terminal of the event and command control module, a second input terminal which is connected to a second output terminal of the event and command control module, a third input terminal for receiving an instantaneous reactive power (Q) output from the AC excitation synchronous condenser to the local power grid and a fourth input terminal for receiving a measured rotating speed (ω r ) of the AC-excitation induction machine, and is configured to receive the reactive power command (Q*) and the rotating speed command (ω r *), collect the instantaneous reactive power (Q) and the measured rotating speed (ω r ) and then process the input signals according to a rotor maximum reactive current command I rq max *, a rotor minimum reactive current command I rq min *, a rotor maximum active current command I rd max * and a rotor minimum active current command I rd min * that are preset, so as to obtain a rotor reactive current command I rq * and a rotor active current command I rd *;
the excitation current control module has a first input terminal which is connected to a first output terminal of the rotating speed and reactive power control module, a second input terminal which is connected to a second output terminal of the rotating speed and reactive power control module and a third input terminal for receiving current signals, and is configured to receive the rotor reactive current command I rq * and the rotor active current command I rd *, collect a rotor active current I rd , a rotor reactive current I rq , a stator active current I sd and a stator reactive current I sq of the AC-excitation induction machine as well as a slip frequency angular velocity ω s , and then process the input signals according to a maximum excitation current capacity I max of the full-controlled AC excitation converter, an excitation inductance L m of the AC-excitation induction machine and a rotor inductance L r of the AC-excitation induction machine, so as to obtain an excitation voltage command for the full-controlled AC excitation converter, so that the full-controlled AC excitation converter is controlled to perform AC excitation of the AC-excitation induction machine;
the DC voltage control module has a first input terminal for receiving a DC bus voltage (U dc ) and a second input terminal for receiving voltage and current signals of the local power grid, and is configured to receive the DC bus voltage (U dc ), collect an active current (I gd ) and a reactive current I gq output from the grid-side converter, a d-axis component U gd and a q-axis component U gq of a voltage at the access point of the grid-side converter and a power grid voltage angular velocity ω 1 , and then process the input signals according to a DC bus voltage command U dc *, a resistance R g of a filter in the grid-side converter and an inductance L g of the filter in the grid-side converter to obtain a control voltage of the grid-side converter, so as to maintain the stability of the DC bus voltage, so that it is ensured that the full-controlled AC excitation converter has sufficient excitation control capability;
the full-controlled AC excitation converter is configured to receive the excitation voltage command and perform independent regulation on the active power and the reactive power of the AC-excitation induction machine; and
the grid-side converter is configured to receive the control voltage command and regulate the active power input from the grid-side converter so as to maintain the stability of the DC bus voltage, so that it is ensured that the full-controlled AC excitation converter has sufficient excitation control capability.

2. A control method for an AC excitation synchronous condenser, comprising:
S 1 : obtaining a corresponding reactive power command Q* from the superior command or the local control according to a preset working mode;
S 2 : obtaining a rotating speed command ω r * according to information about a frequency of the local power grid and a motor speed;
S 3 : obtaining a rotor reactive current command I rq * according to deviation between a measured reactive power of the local power grid and the reactive power command;
S 4 : obtaining a rotor active current command I rd * according to deviation between a measured rotating speed of the AC-excitation induction machine and the rotating speed command;
S 5 : limiting and allocating the dynamic active current command and reactive current command according to the capacity of the full-controlled AC excitation converter, and obtaining an excitation voltage command for the full-controlled AC excitation converter, so that the full-controlled AC excitation converter performs independent excitation of the AC-excitation induction machine; and
S 6 : calculating an active current command for the grid-side converter according to deviation between a measured DC bus voltage and the DC bus voltage command, and obtaining a control voltage command for the grid-side converter, so as to maintain the stability of the DC bus voltage, so that it is ensured that the full-controlled AC excitation converter has sufficient excitation control capability.

3. The control method of claim 2 , wherein the step S 1 specifically includes: if the set working mode is to obtain a reactive power command from the superior command, receiving a superior reactive power command (Q in *) and obtaining a reactive power command Q*=Q in *; or if the set working mode is to obtain a reactive power command from the local control, obtaining a measured voltage (U) of the local power grid and then obtaining a reactive power command Q*=K pu (U N −U)+K iu ∫(U N −U)dt through proportional-integral operation, where K pu represents a proportional coefficient of a reactive power regulator, and K iu represents an integration coefficient of the reactive power regulator.

4. The control method of claim 2 , wherein the step S 2 specifically includes: obtaining a measured frequency f of the local power grid and according to a rated rotating speed synchronization command ω rN *, a rated frequency f N of the local power grid, a maximum rotating speed command ω r max * and a minimum rotating speed command ω r min * that are preset, obtaining a rotating speed command (ω r *) through proportional-integral operation, in which the rotating speed c

Assignees

• Univ Huazhong Science Tech

Inventors

• Hu Jiabing
• Chang Yuanzhu
• Zhang Enbo
• Yuan Xiaoming

Classifications

• H02J3/1885 Primary

  using rotating AC generators, e.g. synchronous generators · CPC title

• Y02E40/30

  Reactive power compensation · CPC title

• H02P9/10

  Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load · CPC title

• H02P9/08 Primary

  Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation · CPC title

• H02J3/18

  Arrangements for adjusting, eliminating or compensating reactive power in networks · CPC title